1: Int J Dev Biol. 2005;49(7):851-8. 

PBX1 intracellular localization is independent of MEIS1 in epithelial cells of
the developing female genital tract.

Dintilhac A, Bihan R, Guerrier D, Deschamps S, Bougerie H, Watrin T, Bonnec G,
Pellerin I.

UMR 6061, Genetique et Developpement, IFR 140, Universite de Rennes 1, Campus
Villejean, Rennes, France.

While studies have highlighted the role of HOXA9-13 and PBX1 homeobox genes
during the development of the female genital tract, the molecular mechanisms
triggered by these genes are incompletely elucidated. In several developmental
pathways, PBX1 binds to MEINOX family members in the cytoplasm to be imported
into the nucleus where they associate with HOX proteins to form a higher complex
that modulates gene expression. This concept has been challenged by a recent
report showing that in some cell cultures, PBX1 nuclear localization might be
regulated independently of MEINOX proteins (Kilstrup-Nielsen et al., 2003). Our
work gives the first illustration of this alternative mechanism in an
organogenesis process. Indeed, we show that PBX1 is mostly cytoplasmic in
epithelial endometrial cells of the developing female genital tract despite the
nuclear localization of MEIS1. We thus provide evidence for a control of PBX1
intracellular distribution which is independent of MEINOX proteins, but is cell
cycle correlated.

PMID: 16172981 [PubMed - in process]


---------------------------------------------------------------


2: Leukemia. 2005 Nov;19(11):1948-57. 

CALM-AF10+ T-ALL expression profiles are characterized by overexpression of HOXA
and BMI1 oncogenes.

Dik WA, Brahim W, Braun C, Asnafi V, Dastugue N, Bernard OA, van Dongen JJ,
Langerak AW, Macintyre EA, Delabesse E.

Department of Immunology, Erasmus MC, Rotterdam, The Netherlands.

The t(10;11)(p13;q14-21) is found in T-ALL and acute myeloid leukemia and fuses
CALM (Clathrin-Assembly protein-like Lymphoid-Myeloid leukaemia gene) to AF10.
In order to gain insight into the transcriptional consequences of this fusion,
microarray-based comparison of CALM-AF10+ vs CALM-AF10- T-ALL was performed.
This analysis showed upregulation of HOXA5, HOXA9, HOXA10 and BMI1 in the
CALM-AF10+ cases. Microarray results were validated by quantitative RT-PCR on an
independent group of T-ALL and compared to mixed lineage leukemia-translocated
acute leukemias (MLL-t AL). The overexpression of HOXA genes was associated with
overexpression of its cofactor MEIS1 in CALM-AF10+ T-ALL, reaching levels of
expression similar to those observed in MLL-t AL. Consequently, CALM-AF10+ T-ALL
and MLL-t AL share a specific HOXA overexpression, indicating they activate
common oncogenic pathways. In addition, BMI1, located close to AF10 breakpoint,
was overexpressed only in CALM-AF10+ T-ALL and not in MLL-t AL. BMI1 controls
cellular proliferation through suppression of the tumor suppressors encoded by
the CDKN2A locus. This locus, often deleted in T-ALL, was conserved in
CALM-AF10+ T-ALL. This suggests that decreased CDKN2A activity, as a result of
BMI1 overexpression, contributes to leukemogenesis in CALM-AF10+ T-ALL. We
propose to define a HOXA+ leukemia group composed of at least MLL-t, CALM-AF10
and HOXA-t AL, which may benefit from adapted management.

PMID: 16107895 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


3: Blood. 2005 Nov 15;106(10):3559-3566. Epub 2005 Jul 26. 

Targeting MLL-AF4 with short interfering RNAs inhibits clonogenicity and
engraftment of t(4;11)-positive human leukemic cells.

Thomas M, Gessner A, Vornlocher HP, Hadwiger P, Greil J, Heidenreich O.

Department of Molecular Biology, Interfaculty Institute for Cell Biology,
Eberhard Karls University of Tuebingen, Auf der Morgenstelle 15, 72076
Tuebingen, Germany. olaf.heidenreich@uni-tuebingen.de.

The chromosomal translocation t(4;11) marks infant acute lymphoblastic leukemia
associated with a particularly dismal prognosis. The leukemogenic role of the
corresponding fusion gene MLL-AF4 is not well understood. We show that transient
inhibition of MLL-AF4 expression with small interfering RNAs impairs the
proliferation and clonogenicity of the t(4; 11)-positive human leukemic cell
lines SEM and RS4;11. Reduction of mixed-lineage leukemia (MLL)-ALL-1 fused gene
from chromosome 4 (AF4) levels induces apoptosis associated with caspase-3
activation and diminished BCL-X(L) expression. Suppression of MLL-AF4 is
paralleled by a decreased expression of the homeotic genes HOXA7, HOXA9, and
MEIS1. MLL-AF4 depletion inhibits expression of the stem-cell marker CD133,
indicating hematopoietic differentiation. Transfection of leukemic cells with
MLL-AF4 siRNAs reduces leukemia-associated morbidity and mortality in SCID mice
that received a xenotransplant, suggesting that MLL-AF4 depletion negatively
affects leukemia-initiating cells. Our findings demonstrate that MLL-AF4 is
important for leukemic clonogenicity and engraftment of this highly aggressive
leukemia. Targeted inhibition of MLL-AF4 fusion gene expression may lead to an
effective and highly specific treatment of this therapy-resistant leukemia.

PMID: 16046533 [PubMed - as supplied by publisher]


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4: Ann N Y Acad Sci. 2005 Jun;1044:109-16. 

Hox genes: from leukemia to hematopoietic stem cell expansion.

Abramovich C, Pineault N, Ohta H, Humphries RK.

Terry Fox Laboratory, 675 West 10th Avenue, Vancouver, BC, V5Z 1L3, Canada.
khumphri@bccrc.ca.

Hox genes are clearly implicated in leukemia; however, neither the specificity
of the leukemogenic potential among Hox genes of different paralog groups nor
the role of the homeodomain is clear. We tested the leukemogenic potential of
various NUP98-Hox fusion genes alone and with MEIS1. All genes tested had a
significant overlapping effect in bone marrow cells in vitro. However, not all
formed strong leukemogenic NUP98 fusion genes; but together with overexpression
of MEIS1, all induced myeloid leukemia. This phenomenon was also seen with NUP98
fusions containing only the homeodomain of the corresponding Hox protein. We
then exploited the strong transforming potential of NUP98-HOXD13 and
NUP98-HOXA10 to establish preleukemic myeloid lines composed of early myeloid
progenitors with extensive in vitro self-renewal capacity, short-term myeloid
repopulating activity, and low propensity for spontaneous leukemic conversion.
We also showed that MEIS1 can efficiently induce their conversion to leukemic
stem cells, thus providing a novel model for the study of leukemic progression.
In contrast to the leukemogenic effect of most of the Hox genes tested, HOXB4
has the ability to increase the self-renewal of hematopoietic stem cells without
disrupting normal differentiation. On the basis of the discovery that the
leukemogenic gene HOXA9 can also expand hematopoietic stem cells, we compared
the ability of NUP98-Hox fusions to that of HOXB4 to trigger HSC expansion in
vitro. Our preliminary results indicate that the expanding potential of HOXB4 is
retained and even augmented by fusion to NUP98. Moreover, even greater expansion
may be possible using Abd-B-like Hox fusions genes.

PMID: 15958703 [PubMed - in process]


---------------------------------------------------------------


5: Blood. 2005 Jul 1;106(1):254-64. Epub 2005 Mar 8. 

Meis1 programs transcription of FLT3 and cancer stem cell character, using a
mechanism that requires interaction with Pbx and a novel function of the Meis1
C-terminus.

Wang GG, Pasillas MP, Kamps MP.

Department of Pathology and Molecular Pathology Program, School of Medicine,
University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093,
USA.

Meis1 is a homeodomain transcription factor coexpressed with Hoxa9 in most human
acute myeloid leukemias (AMLs). In mouse models of leukemia produced by Hoxa9,
Meis1 accelerates leukemogenesis. Because Hoxa9 immortalizes myeloid progenitors
in the absence of Meis1 expression, the contribution of Meis1 toward leukemia
remains unclear. Here, we describe a cultured progenitor model in which Meis1
programs leukemogenicity. Progenitors immortalized by Hoxa9 in culture are
myeloid-lineage restricted and only infrequently caused leukemia after more than
250 days. Coexpressed Meis1 programmed rapid AML-initiating character,
maintained multipotent progenitor potential, and induced expression of genes
associated with short-term hematopoietic stem cells (HSCs), such as FLT3 and
CD34, whose expression also characterizes the leukemia-initiating stem cells of
human AML. Meis1 leukemogenesis functions required binding to Pbx, binding to
DNA, and a conserved function of its C-terminal tail. We hypothesize that Meis1
is required for the homing and survival of leukemic progenitors within their
hematopoietic niches, functions mediated by HSC-specific genes such as CD34 and
Fms-like tyrosine kinase 3 (FLT3), respectively. This is the first example of a
transcription factor oncoprotein (Meis1) that establishes expression of a
tyrosine kinase oncoprotein (FLT3), and explains their coexpression in human
leukemia. This cultured progenitor model will be useful to define the genetic
basis of leukemogenesis involving Hoxa9 and Meis1.

PMID: 15755900 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


6: J Biol Chem. 2005 Apr 1;280(13):12359-70. Epub 2005 Jan 28. 

HOXA9 activates transcription of the gene encoding gp91Phox during myeloid
differentiation.

Bei L, Lu Y, Eklund EA.

Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.

The CYBB gene encodes gp91Phox; a component of the phagocyte respiratory burst
oxidase. CYBB transcription is restricted to myeloid cells differentiated beyond
the promyelocyte stage. In undifferentiated myeloid cells, the homeodomain (HD)
transcription factor HoxA10 represses CYBB transcription via a cis element in
the proximal promoter. During myelopoiesis, phosphorylation of conserved
tyrosine residues in the HD decreases HoxA10 binding to this CYBB cis element.
In the current studies, we found HoxA9 activates CYBB transcription in
differentiated myeloid cells via the same cis element. We find HoxA9-mediated
CYBB-transcription requires Pbx1 but is inhibited by Meis1. Additionally,
phosphorylation of the conserved HD tyrosines increases HoxA9 binding to the
CYBB promoter. The HOXA9 gene is involved in leukemia-associated translocations
with the gene encoding Nup98, a nucleopore protein. We find expression of a
Nup98-hoxA9 fusion protein blocks HoxA9-induced CYBB transcription in
differentiating myeloid cells. In comparison to HoxA9, Nup98-hoxA9 has greater
binding affinity for the CYBB cis element, but binding is not altered by HD
tyrosine phosphorylation. Therefore, these studies identify CYBB as a common
target gene repressed by HoxA10 and activated by HoxA9. These studies also
suggest overexpression of Meis1 or Nup98-hoxA9 represses myeloid-specific gene
transcription, thereby contributing to differentiation block in leukemogenesis.

PMID: 15681849 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


7: Immunogenetics. 2005 Jan;56(10):710-21. Epub 2004 Dec 1. 

Characterization of two genes encoding leucine-rich repeat-containing proteins
in grass carp Ctenopharyngodon idellus.

Chang MX, Nie P, Xie HX, Sun BJ, Gao Q.

State Key Laboratory of Freshwater Ecology and Biotechnology, Chinese Academy of
Sciences, Wuhan, 430072, Hubei Province, PR China. pinnie@ihb.ac.cn

The cDNAs and genes of two different types of leucine-rich repeat-containing
proteins from grass carp (Ctenopharyngodon idellus) were cloned. Homology search
revealed that the two genes, designated as GC-GARP and GC-LRG, have 37% and 32%
deduced amino-acid sequence similarities with human glycoprotein A repetitions
predominant precursor (GARP) and leucine-rich alpha2-glycoprotein (LRG),
respectively. The cDNAs of GC-GARP and GC-LRG encoded 664 and 339 amino acid
residues, respectively. GC-GARP and GC-LRG contain many distinct structural
and/or functional motifs of the leucine-rich repeat (LRR) subfamily, such as
multiple conserved 11-residue segments with the consensus sequence LxxLxLxxN/CxL
(x can be any amino acid). The genes GC-GARP and GC-LRG consist of two exons,
with 4,782 bp and 2,119 bp in total length, respectively. The first exon of each
gene contains a small 5'-untranslated region and partial open reading frame. The
putative promoter region of GC-GARP was found to contain transcription factor
binding sites for GATA-1, IRF4, Oct-1, IRF-7, IRF-1, AP1, GATA-box and NFAT, and
the promoter region of GC-LRG for MYC-MAX, MEIS1, ISRE, IK3, HOXA9 and C/EBP
alpha. Phylogenetic analysis showed that GC-GARP and mammalian GARPs were
clustered into one branch, while GC-LRG and mammalian LRGs were in another
branch. The GC-GARP gene was only detected in head kidney, and GC-LRG in the
liver, spleen and heart in the copepod (Sinergasilus major)-infected grass carp,
indicating the induction of gene expression by the parasite infection. The
results obtained in the present study provide insight into the structure of fish
LRR genes, and further study should be carried out to understand the importance
of LRR proteins in host-pathogen interactions.

PMID: 15578176 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


8: Blood. 2005 Feb 15;105(4):1456-66. Epub 2004 Nov 2. 

HOXB6 overexpression in murine bone marrow immortalizes a myelomonocytic
precursor in vitro and causes hematopoietic stem cell expansion and acute
myeloid leukemia in vivo.

Fischbach NA, Rozenfeld S, Shen W, Fong S, Chrobak D, Ginzinger D, Kogan SC,
Radhakrishnan A, Le Beau MM, Largman C, Lawrence HJ.

Department of Medicine, Veterans Affairs Medical Center, San Francisco, CA
94121, USA. fischba@itsa.ucsf.edu

The HOX family of homeobox genes plays an important role in normal and malignant
hematopoiesis. Dysregulated HOX gene expression profoundly effects the
proliferation and differentiation of hematopoietic stem cells (HSCs) and
committed progenitors, and aberrant activation of HOX genes is a common event in
human myeloid leukemia. HOXB6 is frequently overexpressed in human acute myeloid
leukemia (AML). To gain further insight into the role of HOXB6 in hematopoiesis,
we overexpressed HOXB6 in murine bone marrow using retrovirus-mediated gene
transfer. We also explored structure-function relationships using mutant HOXB6
proteins unable to bind to DNA or a key HOX-binding partner, pre-B-cell leukemia
transcription factor-1 (PBX1). Additionally, we investigated the potential
cooperative interaction with myeloid ecotropic viral integration site 1 homolog
(MEIS1). In vivo, HOXB6 expanded HSCs and myeloid precursors while inhibiting
erythropoiesis and lymphopoiesis. Overexpression of HOXB6 resulted in AML with a
median latency of 223 days. Coexpression of MEIS1 dramatically shortened the
onset of AML. Cytogenetic analysis of a subset of HOXB6-induced AMLs revealed
recurrent deletions of chromosome bands 2D-E4, a region frequently deleted in
HOXA9-induced AMLs. In vitro, HOXB6 immortalized a factor-dependent
myelomonocytic precursor capable of granulocytic and monocytic differentiation.
These biologic effects of HOXB6 were largely dependent on DNA binding but
independent of direct interaction with PBX1.

PMID: 15522959 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


9: Blood. 2005 Feb 1;105(3):1222-30. Epub 2004 Oct 12. 

Meis1-mediated apoptosis is caspase dependent and can be suppressed by
coexpression of HoxA9 in murine and human cell lines.

Wermuth PJ, Buchberg AM.

Department of Microbiology and Immunology, Kimmel Cancer Center, Jefferson
Medical College, Thomas Jefferson University, 233 S 10th St, Philadelphia, PA
19107-5541, USA.

Coexpression of the homeodomain protein Meis1 and either HoxA7 or HoxA9 is
characteristic of many acute myelogenous leukemias. Although Meis1 can be
overexpressed in bone marrow long-term repopulating cells, it is incapable of
mediating their transformation. Although overexpressing HoxA9 alone transforms
murine bone marrow cells, concurrent Meis1 overexpression greatly accelerates
oncogenesis. Meis1-HoxA9 cooperation suppresses several myeloid differentiation
pathways. We now report that Meis1 overexpression strongly induces apoptosis in
a variety of cell types in vitro through a caspase-dependent process. Meis1
requires a functional homeodomain and Pbx-interaction motif to induce apoptosis.
Coexpressing HoxA9 with Meis1 suppresses this apoptosis and provides protection
from several apoptosis inducers. Pbx1, another Meis1 cofactor, also induces
apoptosis; however, coexpressing HoxA9 is incapable of rescuing Pbx-mediated
apoptosis. This resistance to apoptotic stimuli, coupled with the previously
reported ability to suppress multiple myeloid differentiation pathways, would
provide a strong selective advantage to Meis1-HoxA9 coexpressing cells in vivo,
leading to leukemogenesis.

PMID: 15479723 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


10: Blood. 2005 Jan 15;105(2):784-93. Epub 2004 Sep 28. 

Identification of cooperative genes for NUP98-HOXA9 in myeloid leukemogenesis
using a mouse model.

Iwasaki M, Kuwata T, Yamazaki Y, Jenkins NA, Copeland NG, Osato M, Ito Y, Kroon
E, Sauvageau G, Nakamura T.

Department of Carcinogenesis, Japanese Foundation for Cancer Research, Tokyo,
Japan.

The chromosomal translocation t(7; 11)(p15;p15), observed in human myeloid
leukemia, results in a NUP98 and HOXA9 gene fusion. We generated a transgenic
mouse line that specifically expressed the chimeric NUP98-HOXA9 gene in the
myeloid lineage. While only 20% of the transgenic mice progressed to leukemia
after a latency period, myeloid progenitor cells from nonleukemic transgenic
mice still exhibited increased proliferative potential. This suggested that the
NUP98-HOXA9 fusion induced a preleukemic phase, and other factors were required
for complete leukemogenesis. NUP98-HOXA9 expression promoted the onset of
retrovirus-induced BXH2 myeloid leukemia. This phenomenon was used to identify
cooperative disease genes as common integration sites (CISs). Meis1, a known HOX
cofactor, was identified as a CIS with a higher integration frequency in
transgenic than in wild-type BXH2 mice. By the same means we identified further
4 candidate cooperative genes, Dnalc4, Fcgr2b, Fcrl, and Con1. These genes
cooperated with NUP98-HOXA9 in transforming NIH 3T3 cells. The system described
here is a powerful tool to identify cooperative oncogenes and will assist in the
clarification of the multistep process of carcinogenesis.

PMID: 15454493 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


11: Mol Cell Biol. 2004 Aug;24(15):6751-62. 

Thrombopoietin induces HOXA9 nuclear transport in immature hematopoietic cells:
potential mechanism by which the hormone favorably affects hematopoietic stem
cells.

Kirito K, Fox N, Kaushansky K.

Department of Medicine, University of California-San Diego School of Medicine,
402 Dickinson St., Suite 380, San Diego, CA 92103-8811, USA.

Members of the homeobox family of transcription factors are major regulators of
hematopoiesis. Overexpression of either HOXB4 or HOXA9 in primitive marrow cells
enhances the expansion of hematopoietic stem cells (HSCs). However, little is
known of how expression or function of these proteins is regulated during
hematopoiesis under physiological conditions. In our previous studies we
demonstrated that thrombopoietin (TPO) enhances levels of HOXB4 mRNA in
primitive hematopoietic cells (K. Kirito, N. Fox, and K. Kaushansky, Blood
102:3172-3178, 2003). To extend our studies, we investigated the effects of TPO
on HOXA9 in this same cell population. Although overall levels of the
transcription factor were not affected, we found that TPO induced the nuclear
import of HOXA9 both in UT-7/TPO cells and in primitive
Sca-1(+)/c-kit(+)/Gr-1(-) hematopoietic cells in a mitogen-activated protein
kinase-dependent fashion. TPO also controlled MEIS1 expression at mRNA levels,
at least in part due to phosphatidylinositol 3-kinase activation. Collectively,
TPO modulates the function of HOXA9 by leading to its nuclear translocation,
likely mediated by effects on its partner protein MEIS1, and potentially due to
two newly identified nuclear localization signals. Our data suggest that TPO
controls HSC development through the regulation of multiple members of the Hox
family of transcription factors through multiple mechanisms.

PMID: 15254242 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


12: Leuk Lymphoma. 2004 Mar;45(3):567-74. 

Expression of HOX genes in acute leukemia cell lines with and without MLL
translocations.

Quentmeier H, Dirks WG, Macleod RA, Reinhardt J, Zaborski M, Drexler HG.

DSMZ--German Collection of Microorganisms and Cell Cultures, Department of Human
and Animal Cell Cultures, Braunschweig, Germany. hqu@dsmz.de

In primary cells from acute leukemia patients, expression of the genes MEIS1,
HOXA5, HOXA7 and HOXA9 has been reported to be correlated with the occurrence of
MLL translocations. It was our aim to find out whether MLL mutant (MLLmu) and
MLL wild-type (MLLwt) acute leukemia-derived cell lines might likewise be
discriminated on the basis of HOX gene expression. Southern blot analysis,
performed to verify the MLL status of the cells, showed that NOMO-1 was the only
cell line not tested previously carrying a rearranged MLL gene. Fluorescence in
situ hybridization analysis demonstrated that this cell line exhibited a
reciprocal t(9;11)(q23;p22). Sequencing of RT-PCR products thereof identified
unique MLL exon 10/AF-9 exon 5 fusion transcripts. We divided the acute
leukemia-derived cell lines (n = 37) according to the results of Southern blot
analysis into MLLmu (n = 19) and MLLwt (n = 18). Expression of HOX genes was
then analyzed by applying reverse transcriptase-polymerase chain reaction,
Northern and Western blot analyses. Acute myeloid leukemia (AML) cell lines
expressed the HOX genes significantly more often than acute lymphoblastic (ALL)
cell lines. In ALL, cells with MLL translocations expressed the genes 4 times
more often than MLLwt cells. Most distinct was the correlation between MLL
status and MEIS1 expression in ALL-derived cell lines: 8/8 MLLmu but 0/10 MLLwt
cell lines expressed MEIS1. Northern and Western blot analysis confirmed that
also HOXA9 and FLT3 were significantly more often and stronger expressed in
MLLmu than in MLLwt ALL cell lines. These results suggest that MLL aberrations
may regulate MEIS1 and HOXA9 gene expression in ALL-derived cell lines, while
AML-derived cell lines express these genes independently of the MLL status.

PMID: 15160920 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


13: Leukemia. 2004 Jul;18(7):1231-7. 

MEIS 1 expression is downregulated through promoter hypermethylation in AML1-ETO
acute myeloid leukemias.

Lasa A, Carnicer MJ, Aventin A, Estivill C, Brunet S, Sierra J, Nomdedeu JF.

Department of Hematology, Hospital de la Santa Creu i Sant Pau, Barcelona,
Spain.

Retroviral insertional mutagenesis in BXH2 mice commonly induces myeloid
leukemias. One of the most frequently involved genes in experimental studies is
Meis 1. In contrast to other genes in murine models, Meis 1 has not been
affected by recurrent chromosomal translocations or point mutations in human
leukemias. We found a constant downregulation of the Meis 1 gene mRNA in
AML1-ETO acute myeloid leukemias and in those cases harboring in frame mutations
in the bZIP domain of CEBPalpha. The absence of the Meis 1 mRNA was not caused
by inactivating point mutations in the coding sequence. Promoter
hypermethylation was present in more than half of the cases (9/14), including
samples obtained from the widely employed Kasumi-1 cell line. Double treatment
with 5-Aza-2'-deoxycytidine and trichostatin A of the Kasumi-1 cell line
partially reverses Meis 1 inhibition. HoxA9 levels were also low. In a cell line
model (U937 Tet AML1-ETO), AML1-ETO expression was not associated with Meis 1
suppression at 72 h. Nevertheless, Meis 1 repression is dependent on the
AML1-ETO transcript levels in treated leukemic patients. Chimeric products that
arise from chromosomal translocations may be associated with locus-specific
epigenetic inactivation. It remains to be investigated when this methylation
process is acquired and which are the basic mechanisms underlying these
molecular events in AML1-ETO and CEBPalpha-mutated AML.

PMID: 15103390 [PubMed - indexed for MEDLINE]


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14: Proc Natl Acad Sci U S A. 2004 Jan 20;101(3):817-22. Epub 2004 Jan 12. 

Ectopic expression of the homeobox gene Cdx2 is the transforming event in a
mouse model of t(12;13)(p13;q12) acute myeloid leukemia.

Rawat VP, Cusan M, Deshpande A, Hiddemann W, Quintanilla-Martinez L, Humphries
RK, Bohlander SK, Feuring-Buske M, Buske C.

GSF-Clinical Cooperative Group Leukemia and Department of Medicine III,
Grosshadern, Ludwig Maximilians University, 81377 Munich, Germany.

Creation of fusion genes by balanced chromosomal translocations is one of the
hallmarks of acute myeloid leukemia (AML) and is considered one of the key
leukemogenic events in this disease. In t(12;13)(p13;q12) AML, ectopic
expression of the homeobox gene CDX2 was detected in addition to expression of
the ETV6-CDX2 fusion gene, generated by the chromosomal translocation. Here we
show in a murine model of t(12;13)(p13;q12) AML that myeloid leukemogenesis is
induced by the ectopic expression of CDX2 and not by the ETV6-CDX2 chimeric
gene. Mice transplanted with bone marrow cells retrovirally engineered to
express Cdx2 rapidly succumbed to fatal and transplantable AML. The transforming
capacity of Cdx2 depended on an intact homeodomain and the N-terminal
transactivation domain. Transplantation of bone marrow cells expressing
ETV6-CDX2 failed to induce leukemia. Furthermore, coexpression of ETV6-CDX2 and
Cdx2 in bone marrow cells did not accelerate the course of disease in
transplanted mice compared to Cdx2 alone. These data demonstrate that activation
of a protooncogene by a balanced chromosomal translocation can be the pivotal
leukemogenic event in AML, characterized by the expression of a
leukemia-specific fusion gene. Furthermore, these findings link protooncogene
activation to myeloid leukemogenesis, an oncogenic mechanism so far associated
mainly with lymphoid leukemias and lymphomas.

PMID: 14718672 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


15: EMBO J. 2004 Jan 28;23(2):450-9. Epub 2004 Jan 8. 

Hematopoietic, angiogenic and eye defects in Meis1 mutant animals.

Hisa T, Spence SE, Rachel RA, Fujita M, Nakamura T, Ward JM, Devor-Henneman DE,
Saiki Y, Kutsuna H, Tessarollo L, Jenkins NA, Copeland NG.

Center for Cancer Research, Mouse Cancer Genetics Program, National Cancer
Institute, Frederick, MD, USA.

Meis1 and Hoxa9 expression is upregulated by retroviral integration in murine
myeloid leukemias and in human leukemias carrying MLL translocations. Both genes
also cooperate to induce leukemia in a mouse leukemia acceleration assay, which
can be explained, in part, by their physical interaction with each other as well
as the PBX family of homeodomain proteins. Here we show that Meis1-deficient
embryos have partially duplicated retinas and smaller lenses than normal. They
also fail to produce megakaryocytes, display extensive hemorrhaging, and die by
embryonic day 14.5. In addition, Meis1-deficient embryos lack well-formed
capillaries, although larger blood vessels are normal. Definitive myeloerythroid
lineages are present in the mutant embryos, but the total numbers of
colony-forming cells are dramatically reduced. Mutant fetal liver cells also
fail to radioprotect lethally irradiated animals and they compete poorly in
repopulation assays even though they can repopulate all hematopoietic lineages.
These and other studies showing that Meis1 is expressed at high levels in
hematopoietic stem cells (HSCs) suggest that Meis1 may also be required for the
proliferation/self-renewal of the HSC.

PMID: 14713950 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


16: Mol Cell Biol. 2004 Jan;24(2):617-28. 

Hoxa9 and Meis1 are key targets for MLL-ENL-mediated cellular immortalization.

Zeisig BB, Milne T, Garcia-Cuellar MP, Schreiner S, Martin ME, Fuchs U,
Borkhardt A, Chanda SK, Walker J, Soden R, Hess JL, Slany RK.

Department of Genetics, University Erlangen, Staudtstrasse 5, 91058 Erlangen,
Germany.

MLL fusion proteins are oncogenic transcription factors that are associated with
aggressive lymphoid and myeloid leukemias. We constructed an inducible MLL
fusion, MLL-ENL-ERtm, that rendered the transcriptional and transforming
properties of MLL-ENL strictly dependent on the presence of 4-hydroxy-tamoxifen.
MLL-ENL-ERtm-immortalized hematopoietic cells required 4-hydroxy-tamoxifen for
continuous growth and differentiated terminally upon tamoxifen withdrawal.
Microarray analysis performed on these conditionally transformed cells revealed
Hoxa9 and Hoxa7 as well as the Hox coregulators Meis1 and Pbx3 among the targets
upregulated by MLL-ENL-ERtm. Overexpression of the Hox repressor Bmi-1 inhibited
the growth-transforming activity of MLL-ENL. Moreover, the enforced expression
of Hoxa9 in combination with Meis1 was sufficient to substitute for MLL-ENL-ERtm
function and to maintain a state of continuous proliferation and differentiation
arrest. These results suggest that MLL fusion proteins impose a reversible block
on myeloid differentiation through aberrant activation of a limited set of
homeobox genes and Hox coregulators that are consistently expressed in
MLL-associated leukemias.

PMID: 14701735 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


17: Blood. 2003 Jul 1;102(1):262-8. Epub 2003 Mar 13. 

Gene expression signatures in MLL-rearranged T-lineage and B-precursor acute
leukemias: dominance of HOX dysregulation.

Ferrando AA, Armstrong SA, Neuberg DS, Sallan SE, Silverman LB, Korsmeyer SJ,
Look AT.

Department of Pediatric Oncology, Mayer-630, Dana-Farber Cancer Institute, 44
Binney Street, Boston, MA 02115, USA.

Rearrangements of the MLL locus, located on human chromosome 11q23, are frequent
in both infant and therapy-related leukemias. Gene expression analysis of
MLL-rearranged B-precursor acute lymphoblastic leukemias (MLL B-ALLs) has
identified these cases as a unique subtype of leukemia, characterized by the
expression of genes associated with both lymphoid and myeloid hematopoietic
lineages. Here we show that MLL fusions also generate a distinct genetic subtype
of T-lineage ALL (MLL T-ALL), in which leukemic cells are characterized by an
early arrest in thymocyte differentiation, with suggestive evidence of
commitment to the gammadelta lineage. Interestingly, multiple genes linked to
cell proliferation (eg, PCNA, MYC, CDK2, and POLA) were down-regulated in
MLL-fusion samples, relative to those transformed by other T-ALL oncogenes (P
<.000 001, Fisher exact test). Overall, MLL T-ALL cases consistently
demonstrated increased levels of expression of a subset of major HOX
genes--HOXA9, HOXA10, and HOXC6--and the MEIS1 HOX coregulator (P <.008,
one-sided Wilcoxon test), a pattern of gene expression that was reiterated in
MLL B-ALLs. However, expression of myeloid lineage genes, previously reported in
MLL B-ALLs, was not identified in T-lineage cases with this abnormality,
suggesting that myeloid gene dysregulation is dispensable in leukemic
transformation mediated by MLL fusion proteins. Our findings implicate
dysregulation of HOX gene family members as a dominant mechanism of leukemic
transformation induced by chimeric MLL oncogenes.

PMID: 12637319 [PubMed - indexed for MEDLINE]


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18: Leukemia. 2002 Nov;16(11):2302-8. 

A novel infant acute lymphoblastic leukemia cell line with MLL-AF5q31 fusion
transcript.

Imamura T, Morimoto A, Ikushima S, Kakazu N, Hada S, Tabata Y, Yagi T, Inaba T,
Hibi S, Sugimoto T, Imashuku S.

Department of Pediatrics, Kyoto Prefectural University of Medicine, Japan.

Infant acute lymphoblastic leukemia (ALL) is characterized by the presence of
the proB phenotype (CD10(-)/CD19(+)), poor prognosis and frequent rearrangement
of the mixed lineage leukemia (MLL) gene. The most frequent rearrangement is
t(4;11)(q21;q23), the role of whose product, the MLL-AF4 fusion transcript, has
been extensively studied in leukemogenesis. In a cell line of infant leukemia
with MLL rearrangement denoted KP-L-RY, panhandle PCR amplification of cDNA
revealed the presence of a fusion transcript, MLL-AF5q31, indicating that AF5q31
is also a partner gene of MLL. In this fusion transcript the MLL exon 6 is fused
in frame to the 5' side of the putative transactivation domain of AF5q31. The
AF5q31 protein is a member of the AF4/LAF4/FMR2-related family of proteins,
which have been suggested to play a role in hematopoietic cell growth and
differentiation. The MLL-AF5q31 fusion transcript, although probably rare,
appears to be associated with the pathogenesis of infant ALL like MLL-AF4.
Co-expression of HoxA9 and Meis1 genes in the KP-L-RY cell line indicated
possible functional similarity between MLL-AF4 and MLL-AF5q31. Further
understanding of the function of AF5q31 as well as the specific leukemogenic
mechanism of MLL-AF5q31 awaits future studies.

Publication Types:
    Case Reports

PMID: 12399976 [PubMed - indexed for MEDLINE]


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19: Br J Haematol. 2002 Oct;119(1):119-21. 

Frequent co-expression of HoxA9 and Meis1 genes in infant acute lymphoblastic
leukaemia with MLL rearrangement.

Imamura T, Morimoto A, Takanashi M, Hibi S, Sugimoto T, Ishii E, Imashuku S.

Department of Paediatrics, Kyoto Prefectural University of Medicine, Japan.
imamura@koto.kpu-m.ac.jp

We studied the expression of HoxA9 and Meis1 by reverse transcriptase-polymerase
chain reaction analysis in leukaemic cells from cases of infant acute
lymphoblastic leukaemia (ALL, n = 27) and childhood ALL (n = 29). These two
genes were co-expressed significantly more frequently in infant ALL than in
childhood ALL (19/27 vs0/29 cases, P < 0.001) and were highly associated with
MLL gene rearrangement in infant ALL cases (P < 0.001). These findings indicate
that the HoxA9 and Meis1 genes are closely associated with MLL gene
rearrangement in the development of infant ALL, which represents a distinct
entity of childhood ALL.

PMID: 12358913 [PubMed - indexed for MEDLINE]


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20: Oncogene. 2002 Jun 20;21(27):4247-56. 

Nup98-HoxA9 immortalizes myeloid progenitors, enforces expression of Hoxa9,
Hoxa7 and Meis1, and alters cytokine-specific responses in a manner similar to
that induced by retroviral co-expression of Hoxa9 and Meis1.

Calvo KR, Sykes DB, Pasillas MP, Kamps MP.

University of California School of Medicine, Department of Pathology 9500 Gilman
Drive, La Jolla, California, CA 92093-0612, USA.

The association between acute myeloid leukaemia (AML) and the aberrant
expression of Hoxa9 is evidenced by (1) proviral activation of Hoxa9 and Meis1
in BXH-2 murine AML, (2) formation of the chimeric Nup98-HoxA9 transactivator
protein as a consequence of the t(7;11) translocation in human AML, and (3) the
strong expression of HoxA9 and Meis1 in human AML. In mouse models, enforced
retroviral expression of Hoxa9 alone in marrow is not sufficient to cause rapid
AML, while co-expression of Meis1 and Hoxa9 induces rapid AML. In contrast,
retroviral expression of Nup98-HoxA9 is sufficient to cause rapid AML in the
absence of enforced Meis1 expression. Previously, we demonstrated that Hoxa9
could block the differentiation of murine marrow progenitors cultured in
granulocyte-macrophage colony-simulating factor (GM-CSF). These progenitors
lacked Meis1 expression, could not proliferate in stem cell factor (SCF), but
could differentiate into neutrophils when switched into granulocyte
colony-simulating factor (G-CSF). Ectopic expression of Meis1 in these Hoxa9
cells suppressed their G-CSF-induced differentiation, permitted proliferation in
SCF, and therein offered a potential explanation of cooperative function.
Because Meis1 binds N-terminal Hoxa9 sequences that are replaced by Nup98, we
hypothesized that Nup98-HoxA9 might consolidate the biochemical functions of
both Hoxa9 and Meis1 on target gene promoters and might evoke their same
lymphokine-responsive profile in immortalized progenitors. Here we report that
Nup98-HoxA9, indeed mimicks Hoxa9 plus Meis1 coexpression - it immortalizes
myeloid progenitors, prevents differentiation in response to GM-CSF, IL-3,
G-CSF, and permits proliferation in SCF. Unexpectedly, however, Nup98-Hoxa9 also
enforced strong transcription of the cellular Hoxa9, Hoxa7 and Meis1 genes at
levels similar to those found in mouse AML's generated by proviral activation of
Hoxa9 and Meis1. Using Hoxa9(-/-) marrow, we demonstrate that expression of
Hoxa9 is not required for myeloid immortalization by Nup98-HoxA9. Rapid
leukaemogenesis by Nup98-HoxA9 may therefore result from both the intrinsic
functions of Nup98-HoxA9, as well as of those of coexpressed HOX and MEIS1
genes.

PMID: 12082612 [PubMed - indexed for MEDLINE]


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21: Leukemia. 2002 Feb;16(2):186-95. 

Quantitative HOX expression in chromosomally defined subsets of acute
myelogenous leukemia.

Drabkin HA, Parsy C, Ferguson K, Guilhot F, Lacotte L, Roy L, Zeng C, Baron A,
Hunger SP, Varella-Garcia M, Gemmill R, Brizard F, Brizard A, Roche J.

Division of Medical Oncology, University of Colorado Health Sciences and Cancer
Centers, Denver, CO 80262, USA.

We used a degenerate RT-PCR screen and subsequent real-time quantitative RT-PCR
assays to examine the expression of HOX and TALE-family genes in 34 cases of
chromosomally defined AML for which outcome data were available. AMLs with
favorable cytogenetic features were associated with low overall HOX gene
expression whereas poor prognostic cases had high levels. Characteristically,
multiple HOXA family members including HOXA3-HOXA10 were jointly overexpressed
in conjunction with HOXB3, HOXB6, MEIS1 and PBX3. Higher levels of expression
were also observed in the FAB subtype, AML-M1. Spearmann correlation
coefficients indicated that the expression levels for many of these genes were
highly inter-related. While we did not detect any significant correlations
between HOX expression and complete response rates or age in this limited set of
patients, there was a significant correlation between event-free survival and
HOXA7 with a trend toward significance for HoxA9, HoxA4 and HoxA5. While
patients with elevated HOX expression did worse, there were notable exceptions.
Thus, although HOX overexpression and clinical resistance to chemotherapy often
coincide, they are not inextricably linked. Our results indicate that
quantitative HOX analysis has the potential to add new information to the
management of patients with AML, especially where characteristic chromosomal
alterations are lacking.

PMID: 11840284 [PubMed - indexed for MEDLINE]


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22: Proc Natl Acad Sci U S A. 2001 Nov 6;98(23):13120-5. Epub 2001 Oct 30. 

Meis1a suppresses differentiation by G-CSF and promotes proliferation by SCF:
potential mechanisms of cooperativity with Hoxa9 in myeloid leukemia.

Calvo KR, Knoepfler PS, Sykes DB, Pasillas MP, Kamps MP.

Department of Pathology, University of California, School of Medicine, 9500
Gilman Drive, La Jolla, CA 92093-0612, USA.

Hoxa9 and Meis1a are homeodomain transcription factors that heterodimerize on
DNA and are down-regulated during normal myeloid differentiation. Hoxa9 and
Meis1a cooperate to induce acute myeloid leukemia (AML) in mice, and are
coexpressed in human AML. Despite their cooperativity in leukemogenesis, we
demonstrated previously that retroviral expression of Hoxa9 alone--in the
absence of coexpressed retroviral Meis1 or of expression of endogenous Meis
genes--blocks neutrophil and macrophage differentiation of primary myeloid
progenitors cultured in granulocyte-macrophage colony-stimulating factor
(GM-CSF). Expression of Meis1 alone did not immortalize any factor-dependent
marrow progenitor. Because HoxA9-immortalized progenitors still execute
granulocytic differentiation in response to granulocyte CSF (G-CSF) and monocyte
differentiation in response to macrophage CSF (M-CSF), we tested the possibility
that Meis1a cooperates with Hoxa9 by blocking viable differentiation pathways
unaffected by Hoxa9 alone. Here we report that Meis1a suppresses G-CSF-induced
granulocytic differentiation of Hoxa9-immortalized progenitors, permitting
indefinite self-renewal in G-CSF. Meis1a also reprograms Hoxa9-immortalized
progenitors to proliferate, rather than die, in response to stem cell factor
(SCF) alone. We propose that Meis1a and Hoxa9 are part of a molecular switch
that regulates progenitor abundance by suppressing differentiation and
maintaining self-renewal in response to different subsets of cytokines during
myelopoiesis. The independent differentiation pathways targeted by Hoxa9 and
Meis1a prompt a "cooperative differentiation arrest" hypothesis for a subset of
leukemia, in which cooperating transcription factor oncoproteins block
complementary subsets of differentiation pathways, establishing a more complete
differentiation block in vivo.

PMID: 11687616 [PubMed - indexed for MEDLINE]


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23: Exp Hematol. 2001 Jul;29(7):856-63. 

Inhibition of myeloid differentiation by Hoxa9, Hoxb8, and Meis homeobox genes.

Fujino T, Yamazaki Y, Largaespada DA, Jenkins NA, Copeland NG, Hirokawa K,
Nakamura T.

Department of Carcinogenesis, The Cancer Institute, Japanese Foundation for
Cancer Research, Tokyo, Japan.

OBJECTIVE: The homeobox gene Hoxb8 is activated in the murine myelomonocytic
cell line WEHI-3B as a result of intracisternal A particle integration.
Cooperative activation between Hoxa9 and Meis1 is induced by retroviral
integration in BXH2 murine myeloid leukemias and the myeloid leukemia cell line
M1. The present study was conducted to examine possible Meis gene activation and
cooperative DNA binding of homeobox proteins in WEHI-3B and to reveal the
specific role of Hox and Meis genes in myeloid differentiation. MATERIALS AND
METHODS: Northern blot analysis and reverse transcriptase polymerase chain
reaction were performed to examine homeobox genes expression. Electrophoretic
mobility shift assay was performed to evaluate DNA binding of homeobox proteins.
Myeloid differentiation of 32Dcl3 was induced by granulocyte colony-stimulating
factor. RESULTS: Meis2 was coactivated with Hoxb8 in WEHI-3B cells. DNA-protein
complexes including Hox, Meis, and Pbx were observed in WEHI-3B and 32Dcl3.
Expression and the DNA-binding complex of Hoxa9, Hoxb8, Meis1, and Meis2 were
down-regulated during myeloid differentiation of 32Dcl3 cells. Enforced
expression of Hox or Meis genes inhibited myeloid differentiation of
32Dcl3.CONCLUSION: The results indicate that Meis2 is an important Meis gene for
myeloid leukemogenesis and that Hox and Meis are important genes for myeloid
leukemogenesis through differentiation block.

PMID: 11438208 [PubMed - indexed for MEDLINE]


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24: Oncogene. 2001 Feb 15;20(7):874-8. 

Upregulation of Meis1 and HoxA9 in acute lymphocytic leukemias with the t(4 :
11) abnormality.

Rozovskaia T, Feinstein E, Mor O, Foa R, Blechman J, Nakamura T, Croce CM,
Cimino G, Canaani E.

Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot
76100, Israel.

Rearrangements of the human ALL-1 gene are frequently encountered in acute
lymphocytic leukemias (ALL) and acute myeloid leukemias (AML). These
rearrangements are mostly due to chromosome translocations and result in
production of chimeric proteins composed of the N-terminal fragment of ALL-1 and
the C-terminal segments of the partner proteins. The most common chromosome
translocation involving ALL-1 is the t(4 : 11) associated with ALL. ALL-1 is the
human homologue of Drosophila trithorax and directly activates transcription of
multiple Hox genes. A preliminary DNA microarray screen indicated that the
Meis1, HoxA9 and AC133 genes were overexpressed in ALLs with t(4 : 11), compared
to ALLs with very similar phenotype but without the chromosomal abnormality.
These genes, as well as additional five Hox genes, were subjected to
comprehensive semi-quantitative or quantitative RT-PCR analysis in 57 primary
ALL and AML tumors. Meis1 and HoxA9 were found expressed in 13/14 of ALLs with
the t(4 : 11) and in 8/8 of AMLs with ALL-1 rearrangements. The two genes were
not consistently transcribed in other types of ALL. AC133 was transcribed in
13/14 of ALLs with t(4 : 11), but in only 4/8 of AMLs with ALL-1 rearrangements.
HoxA10 was expressed in most leukemias with ALL-1 alterations, but was also
transcribed in PrePreB CD10(-) ALLs lacking the t(4 : 11). Expression of HoxA5,
HoxA7, HoxC8 and HoxC10 did not correlate with ALL-1 rearrangements.
Coexpression of Meis1 and HoxA9, overexpression of HoxA10, and overexpression or
fusion of HoxA9 were previously implicated in certain acute myeloid leukemias in
mice and humans. The present work suggests that upregulation of Meis1, HoxA9,
and possibly HoxA10 might also play a role in pathogenesis of acute lymphocytic
and acute myeloid leukemias associated with ALL-1 fusions.

PMID: 11314021 [PubMed - indexed for MEDLINE]


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25: Genomics. 2001 Jan 15;71(2):214-21. 

The MEIS1 oncogene is highly expressed in neuroblastoma and amplified in cell
line IMR32.

Spieker N, van Sluis P, Beitsma M, Boon K, van Schaik BD, van Kampen AH, Caron
H, Versteeg R.

Department of Human Genetics, University of Amsterdam, Amsterdam, 1100DE, The
Netherlands.

Neuroblastoma is an embryonal tumor originating from neural crest-derived cells.
Here we present the serendipitous cloning of amplified sequences of chromosome
2p15 in neuroblastoma cell line IMR32. The amplified region was analyzed for
oncogene activation using a SAGE (serial analysis of gene expression) library of
IMR32. SAGE permits a quantitative analysis of all transcripts of a tissue or
cell line. The expression of genes and ESTs mapping within a 30-cR region
covering the amplicon was compared to 4 additional SAGE libraries of
neuroblastomas and 12 SAGE libraries of other tissues in the CGAP databases. The
IMR32 SAGE database revealed increased expression of the MEIS1 oncogene, whereas
other SAGE libraries showed little or no MEIS1 expression. MEIS1 turned out to
be highly amplified and overexpressed in IMR32. Analysis of 24 neuroblastoma
cell lines and 22 tumors showed high-level expression in about 25% of the cases.
The MEIS1 homeobox protein forms a complex with the HOXA9 and PBX proteins that
are implicated in human leukemia. MEIS1 is a target of retroviral insertion in
murine leukemia. This is the first report of a MEIS1 amplification and high
expression levels in human cancer and the first time that identification of a
candidate target of amplification is facilitated by high-throughput mRNA
expression profiling. Copyright 2001 Academic Press.

PMID: 11161815 [PubMed - indexed for MEDLINE]


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26: EMBO J. 2001 Feb 1;20(3):350-61. 

NUP98-HOXA9 expression in hemopoietic stem cells induces chronic and acute
myeloid leukemias in mice.

Kroon E, Thorsteinsdottir U, Mayotte N, Nakamura T, Sauvageau G.

Laboratory of Molecular Genetics of Hemopoietic Stem Cells, Clinical Research
Institute of Montreal, Montreal, Quebec, H2W 1R7, Canada.

Here we describe hemopoietic chimeras serving as a mouse model for
NUP98-HOXA9-induced leukemia, which reproduced several of the phenotypes
observed in human disease. Mice transplanted with bone marrow cells expressing
NUP98-HOXA9 through retroviral transduction acquire a myeloproliferative disease
(MPD) and eventually succumb to acute myeloid leukemia (AML). The NUP98 portion
of the fusion protein was shown to be responsible for transforming a clinically
silent pre-leukemic phase observed for Hoxa9 into a chronic, stem cell-derived
MPD. The co-expression of NUP98-HOXA9 and Meis1 accelerated the transformation
of MPD to AML, identifying a genetic interaction previously observed for Hoxa9
and Meis1. Our findings demonstrate the presence of overlapping yet distinct
molecular mechanisms for MPD versus AML, illustrating the complexity of leukemic
transformation.

PMID: 11157742 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


27: Mol Cell Biol. 2001 Jan;21(1):224-34. 

Defining roles for HOX and MEIS1 genes in induction of acute myeloid leukemia.

Thorsteinsdottir U, Kroon E, Jerome L, Blasi F, Sauvageau G.

Laboratory of Molecular Genetics of Hemopoietic Stem Cells, Clinical Research
Institute of Montreal, Montreal, Quebec H2W 1R7, Canada.

Complex genetic and biochemical interactions between HOX proteins and members of
the TALE (i.e., PBX and MEIS) family have been identified in embryonic
development, and some of these interactions also appear to be important for
leukemic transformation. We have previously shown that HOXA9 collaborates with
MEIS1 in the induction of acute myeloid leukemia (AML). In this report, we
demonstrate that HOXB3, which is highly divergent from HOXA9, also genetically
interacts with MEIS1, but not with PBX1, in generating AML. In addition, we show
that the HOXA9 and HOXB3 genes play key roles in establishing all the main
characteristics of the leukemias, while MEIS1 functions only to accelerate the
onset of the leukemic transformation. Contrasting the reported functional
similarities between PREP1 and MEIS1, such as PBX nuclear retention, we also
show that PREP1 overexpression is incapable of accelerating the HOXA9-induced
AML, suggesting that MEIS1 function in transformation must entail more than PBX
nuclear localization. Collectively, these data demonstrate that MEIS1 is a
common leukemic collaborator with two structurally and functionally divergent
HOX genes and that, in this collaboration, the HOX gene defines the identity of
the leukemia.

PMID: 11113197 [PubMed - indexed for MEDLINE]


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28: Leuk Res. 2000 Oct;24(10):849-55. 

MEIS1 and HOXA7 genes in human acute myeloid leukemia.

Afonja O, Smith JE Jr, Cheng DM, Goldenberg AS, Amorosi E, Shimamoto T, Nakamura
S, Ohyashiki K, Ohyashiki J, Toyama K, Takeshita K.

Department of Pediatrics, New York University School of Medicine, 550 First
Avenue, New York, NY 10016, USA.

Co-activation of Meisl with Hoxa7 or Hoxa9 homeobox genes by retroviral gene
insertion has recently been reported to be leukemogenic in murine myeloid
leukemia. In this study we determined their expression in human leukemia. Most
human myeloid leukemia cell lines co-expressed MEIS1 with HOXA7 and HOXA9. Among
patients with acute leukemia, 50% of AML patients expressed MEIS1, while the
majority of ALL patients were negative. A total of 89.5% of patients expressing
MEIS1 co-expressed HOXA7. In unadjusted models, poorer response to chemotherapy
was associated with expression of HOXA7 regardless of MEIS1 status and older
patients were more likely to express either gene.

PMID: 10996203 [PubMed - indexed for MEDLINE]


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29: Mol Cell Biol. 2000 May;20(9):3274-85. 

Hoxa9 immortalizes a granulocyte-macrophage colony-stimulating factor-dependent
promyelocyte capable of biphenotypic differentiation to neutrophils or
macrophages, independent of enforced meis expression.

Calvo KR, Sykes DB, Pasillas M, Kamps MP.

Department of Pathology, School of Medicine, University of California San Diego,
La Jolla, California 92093-0612, USA. krcalvo@ucsd.edu

The genes encoding Hoxa9 and Meis1 are transcriptionally coactivated in a subset
of acute myeloid leukemia (AML) in mice. In marrow reconstitution experiments,
coexpression of both genes produces rapid AML, while neither gene alone
generates overt leukemia. Although Hoxa9 and Meis1 can bind DNA as heterodimers,
both can also heterodimerize with Pbx proteins. Thus, while their coactivation
may result from the necessity to bind promoters as heterodimers, it may also
result from the necessity of altering independent biochemical pathways that
cooperate to generate AML, either as monomers or as heterodimers with Pbx
proteins. Here we demonstrate that constitutive expression of Hoxa9 in primary
murine marrow immortalizes a late myelomonocytic progenitor, preventing it from
executing terminal differentiation to granulocytes or monocytes in the presence
of granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3.
This immortalized phenotype is achieved in the absence of endogenous or
exogenous Meis gene expression. The Hoxa9-immortalized progenitor exhibited a
promyelocytic transcriptional profile, expressing PU.1, AML1, c-Myb, C/EBP
alpha, and C/EBP epsilon as well as their target genes, the receptors for
GM-CSF, G-CSF, and M-CSF and the primary granule proteins myeloperoxidase and
neutrophil elastase. G-CSF obviated the differentiation block of Hoxa9, inducing
neutrophilic differentiation with accompanying expression of neutrophil
gelatinase B and upregulation of gp91phox. M-CSF also obviated the
differentiation block, inducing monocytic differentiation with accompanying
expression of the macrophage acetyl-low-density lipoprotein scavenger receptor
and F4/80 antigen. Versions of Hoxa9 lacking the ANWL Pbx interaction motif
(PIM) also immortalized a promyelocytic progenitor with intrinsic biphenotypic
differentiation potential. Therefore, Hoxa9 evokes a cytokine-selective block in
differentiation by a mechanism that does not require Meis gene expression or
interaction with Pbx through the PIM.

PMID: 10757811 [PubMed - indexed for MEDLINE]


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30: Oncogene. 2000 Feb 3;19(5):608-16. 

HoxA9-mediated immortalization of myeloid progenitors requires functional
interactions with TALE cofactors Pbx and Meis.

Schnabel CA, Jacobs Y, Cleary ML.

Department of Pathology, Stanford University School of Medicine, California
94305, USA.

Specific Hox genes are implicated in leukemic transformation, and their
selective genetic collaboration with TALE homeobox genes, Pbx and Meis,
accentuates their oncogenic potential. The molecular mechanisms underlying these
coordinate functions, however, have not been characterized. In this study, we
demonstrate that HoxA9 requires its Pbx interaction motif as well as its amino
terminus to enhance the clonogenic potential of myeloid progenitors in vitro. We
further show that HoxA9 forms functional trimeric DNA binding complexes with Pbx
and Meis-like proteins on a modified enhancer. DNA binding complexes containing
HoxA9 and TALE homeoproteins display cooperative transcriptional activity and
are present in leukemic cells. Trimeric complex formation on its own, however,
is not sufficient for HoxA9-mediated immortalization. Rather, structure-function
analyses demonstrate that domains of HoxA9 which are necessary for cellular
transformation are coincident with those required for trimer-mediated
transcriptional activation. Furthermore, the amino terminus of HoxA9 provides
essential transcriptional effector properties and its requirement for myeloid
transformation can be functionally replaced by the VP16 activation domain. These
data suggest that biochemical interactions between HoxA9 and TALE homeoproteins
mediate cellular transformation in hematopoietic cells, and that their
transcriptional activity in higher order DNA binding complexes provides a
molecular basis for their collaborative roles in leukemogenesis.

PMID: 10698505 [PubMed - indexed for MEDLINE]


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31: Leukemia. 1999 Dec;13(12):1993-9. 

Frequent co-expression of the HOXA9 and MEIS1 homeobox genes in human myeloid
leukemias.

Lawrence HJ, Rozenfeld S, Cruz C, Matsukuma K, Kwong A, Komuves L, Buchberg AM,
Largman C.

Division of Hematology and Medical Oncology, Department of Medicine, University
of California VA Medical Center, San Francisco, CA, USA.

There is increasing evidence that HOX homeobox genes play a role in
leukemogenesis. Recent studies have demonstrated that enforced co-expression of
HOXA9 and MEIS1 in murine marrow leads to rapid development of myeloid leukemia,
and that these proteins exhibit cooperative DNA binding. However, it is unclear
whether co-activation of HOXA9 and MEIS genes is a common occurrence in human
leukemias. We surveyed expression of HOXA9 and MEIS1 in 24 leukemic cell lines
and 80 patient samples, using RNase protection analyses and
immunohistochemistry. We demonstrate that the expression of HOXA9 and MEIS1 in
leukemia cells is uniquely myeloid, and that these genes are commonly
co-expressed in myeloid cell lines and in samples of acute myelogenous leukemia
(AML) of all subtypes except in promyelocytic leukemia. While HOXA9 is expressed
in most cases of chronic myelogenous leukemia, MEIS1 is weakly expressed or not
at all. Immunohistochemical staining of selected AML samples showed moderate to
high levels of HOXA9 protein, primarily cytoplasmic, in leukemic myeloblasts,
with weaker and primarily nuclear staining for MEIS1. These data support the
concept that co-activation of HOXA9 and MEIS1 is a common event in AML, and may
represent a common pathway of many different oncogenic mutations.

PMID: 10602420 [PubMed - indexed for MEDLINE]


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32: Leukemia. 1999 May;13(5):687-98. 

Expression of HOX genes, HOX cofactors, and MLL in phenotypically and
functionally defined subpopulations of leukemic and normal human hematopoietic
cells.

Kawagoe H, Humphries RK, Blair A, Sutherland HJ, Hogge DE.

British Columbia Cancer Agency, and Department of Medicine, University of
British Columbia, Vancouver, Canada.

To explore the possibility that deregulated HOX gene expression might commonly
occur during leukemic hematopoiesis, we compared the relative levels of
expression of these and related genes in phenotypically and functionally defined
subpopulations of AML blasts and normal hematopoietic cells. Initially, a
semi-quantitative RT-PCR technique was used to amplify total cDNA from total
leukemic blast cell populations from 20 AML patients and light density cells
from four normal bone marrows. Expression of HOX genes (A9, A10, B3 and B4),
MEIS1 and MLL was easily detected in the majority of AML samples with the
exception of two samples from patients with AML subtype M3 (which expressed only
MLL). Low levels of HOXA9 and A10 but not B3 or B4 were seen in normal marrow
while MLL was easily detected. PBX1a was difficult to detect in any AML sample
but was seen in three of four normal marrows. Cells from nine AML patients and
five normal bone marrows were FACS-sorted into CD34+CD38-, CD34+CD38+ and
CD34-subpopulations, analyzed for their functional properties in long-term
culture (LTC) and colony assays, and for gene expression using RT-PCR. 93 +/-
14% of AML LTC-initiating cells, 92 +/- 14% AML colony-forming cells, and >99%
of normal LTC-IC and CFC were CD34+. The relative level of expression of the
four HOX genes in amplified cDNA from CD34- as compared to CD34+CD38- normal
cells was reduced >10-fold. However, in AML samples this down-regulation in HOX
expression in CD34- as compared to CD34+CD38- cells was not seen (P < 0.05 for
comparison between AML and normal). A similar difference between normal and AML
subpopulations was seen when the relative levels of expression of MEIS1, and to
a lesser extent MLL, were compared in CD34+ and CD34- cells (P < 0.05). In
contrast, while some evidence of down-regulation of PBX1a was found in comparing
CD34- to CD34+ normal cells it was difficult to detect expression of this gene
in any subpopulation from most AML samples. Thus, the down-regulation of HOX,
MEIS1 and to some extent MLL which occurs with normal hematopoietic
differentiation is not seen in AML cells with similar functional and phenotypic
properties.

PMID: 10374871 [PubMed - indexed for MEDLINE]


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33: Mol Cell Biol. 1999 Apr;19(4):3051-61. 

HOXA9 forms triple complexes with PBX2 and MEIS1 in myeloid cells.

Shen WF, Rozenfeld S, Kwong A, Kom ves LG, Lawrence HJ, Largman C.

Departments of Medicine, University of California VA Medical Center, San
Francisco, California, USA. largman@cgl.ucsf.edu

Aberrant activation of the HOX, MEIS, and PBX homeodomain protein families is
associated with leukemias, and retrovirally driven coexpression of HOXA9 and
MEIS1 is sufficient to induce myeloid leukemia in mice. Previous studies have
demonstrated that HOX-9 and HOX-10 paralog proteins are unique among HOX
homeodomain proteins in their capacity to form in vitro cooperative DNA binding
complexes with either the PBX or MEIS protein. Furthermore, PBX and MEIS
proteins have been shown to form in vivo heterodimeric DNA binding complexes
with each other. We now show that in vitro DNA site selection for MEIS1 in the
presence of HOXA9 and PBX yields a consensus PBX-HOXA9 site. MEIS1 enhances in
vitro HOXA9-PBX protein complex formation in the absence of DNA and forms a
trimeric electrophoretic mobility shift assay (EMSA) complex with these proteins
on an oligonucleotide containing a PBX-HOXA9 site. Myeloid cell nuclear extracts
produce EMSA complexes which appear to contain HOXA9, PBX2, and MEIS1, while
immunoprecipitation of HOXA9 from these extracts results in coprecipitation of
PBX2 and MEIS1. In myeloid cells, HOXA9, MEIS1, and PBX2 are all strongly
expressed in the nucleus, where a portion of their signals are colocalized
within nuclear speckles. However, cotransfection of HOXA9 and PBX2 with or
without MEIS1 minimally influences transcription of a reporter gene containing
multiple PBX-HOXA9 binding sites. Taken together, these data suggest that in
myeloid leukemia cells MEIS1 forms trimeric complexes with PBX and HOXA9, which
in turn can bind to consensus PBX-HOXA9 DNA targets.

PMID: 10082572 [PubMed - indexed for MEDLINE]


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34: EMBO J. 1998 Jul 1;17(13):3714-25. 

Hoxa9 transforms primary bone marrow cells through specific collaboration with
Meis1a but not Pbx1b.

Kroon E, Krosl J, Thorsteinsdottir U, Baban S, Buchberg AM, Sauvageau G.

Laboratory of Molecular Genetics of Hemopoietic Stem Cells, Clinical Research
Institute of Montreal, Montreal, Quebec, Canada H2W 1R7.

Hoxa9, Meis1 and Pbx1 encode homeodomaincontaining proteins implicated in
leukemic transformation in both mice and humans. Hoxa9, Meis1 and Pbx1 proteins
have been shown to physically interact with each other, as Hoxa9 cooperatively
binds consensus DNA sequences with Meis1 and with Pbx1, while Meis1 and Pbx1
form heterodimers in both the presence and absence of DNA. In this study, we
sought to determine if Hoxa9 could transform hemopoietic cells in collaboration
with either Pbx1 or Meis1. Primary bone marrow cells, retrovirally engineered to
overexpress Hoxa9 and Meis1a simultaneously, induced growth factor-dependent
oligoclonal acute myeloid leukemia in <3 months when transplanted into syngenic
mice. In contrast, overexpression of Hoxa9, Meis1a or Pbx1b alone, or the
combination of Hoxa9 and Pbx1b failed to transform these cells acutely within 6
months post-transplantation. Similar results were obtained when FDC-P1 cells,
engineered to overexpress these genes, were transplanted to syngenic recipients.
Thus, these studies demonstrate a selective collaboration between a member of
the Hox family and one of its DNA-binding partners in transformation of
hemopoietic cells.

PMID: 9649441 [PubMed - indexed for MEDLINE]


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35: Mol Cell Biol. 1997 Nov;17(11):6448-58. 

AbdB-like Hox proteins stabilize DNA binding by the Meis1 homeodomain proteins.

Shen WF, Montgomery JC, Rozenfeld S, Moskow JJ, Lawrence HJ, Buchberg AM,
Largman C.

Department of Medicine, University of California VA Medical Center, San
Francisco 94121, USA.

Recent studies show that Hox homeodomain proteins from paralog groups 1 to 10
gain DNA binding specificity and affinity through cooperative binding with the
divergent homeodomain protein Pbx1. However, the AbdB-like Hox proteins from
paralogs 11, 12, and 13 do not interact with Pbx1a, raising the possibility of
different protein partners. The Meis1 homeobox gene has 44% identity to Pbx
within the homeodomain and was identified as a common site of viral integration
in myeloid leukemias arising in BXH-2 mice. These integrations result in
constitutive activation of Meis1. Furthermore, the Hoxa-9 gene is frequently
activated by viral integration in the same BXH-2 leukemias, suggesting a
biological synergy between these two distinct classes of homeodomain proteins in
causing malignant transformation. We now show that the Hoxa-9 protein physically
interacts with Meis1 proteins by forming heterodimeric binding complexes on a
DNA target containing a Meis1 site (TGACAG) and an AbdB-like Hox site
(TTTTACGAC). Hox proteins from the other AbdB-like paralogs, Hoxa-10, Hoxa-11,
Hoxd-12, and Hoxb-13, also form DNA binding complexes with Meis1b, while Hox
proteins from other paralogs do not appear to interact with Meis1 proteins. DNA
binding complexes formed by Meis1 with Hox proteins dissociate much more slowly
than DNA complexes with Meis1 alone, suggesting that Hox proteins stabilize the
interactions of Meis1 proteins with their DNA targets.

PMID: 9343407 [PubMed - indexed for MEDLINE]


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36: Oncogene. 1996 Nov 21;13(10):2235-42. 

Identification of a new family of Pbx-related homeobox genes.

Nakamura T, Jenkins NA, Copeland NG.

ABL-Basic Research Program, NCI-Frederick Cancer Research and Development
Center, Frederick, Maryland 21702, USA.

The expression of Meis1 (a novel Pbx-related homeobox gene) and either Hoxa7 or
Hoxa9 are coactivated by retroviral integration in BXH2 murine myeloid leukemias
(T Nakamura, DA Largaespada, JD Shaughnessy Jr, NA Jenkins and NG Copeland
(1996) Nature Genet. 12: 149-153). As Pbx proteins are Hox cofactors, which
cooperatively bind DNA with Hox proteins to modulate the otherwise similar DNA
bind specificities of Hox proteins, these results suggested that Meis1 may
function as a cofactor for Hoxa7 and Hoxa9 in the induction of murine myeloid
leukemias. By DNA cross-hybridization we have identified two Meis1-related
genes, Meis2 and Meis3. Sequence analysis revealed extensive amino acid
similarity among the three Meis proteins both within and outside of the
homeodomain. Phylogenetic analysis showed that the Meis genes belong to a
distinct family of Pbx-related genes. Chromosome mapping studies indicated that
Meis2 and Meis3 are unlinked to Meis1 and map to mouse chromosome 2 and 7,
respectively. The Meis genes displayed distinct but overlapping patterns of
expression in normal tissues and were expressed in some cases of murine myeloid
leukemia. The identification of two additional Meis genes identifies a new
family of potential Hox cofactors as well as two new potential disease genes.

PMID: 8950991 [PubMed - indexed for MEDLINE]


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37: Nat Genet. 1996 Feb;12(2):149-53. 

Comment in:
    Nat Genet. 1996 Feb;12(2):113-4.

Cooperative activation of Hoxa and Pbx1-related genes in murine myeloid
leukaemias.

Nakamura T, Largaespada DA, Shaughnessy JD Jr, Jenkins NA, Copeland NG.

Mammalian Genetics Laboratory, NCI-Frederick Cancer Research and Development
Center, Maryland 21702, USA.

Retroviruses induce myeloid leukaemia in BXH-2 mice by the insertional mutation
of cellular proto-oncogenes or tumour suppressor genes. Disease genes can thus
be identified by proviral tagging through the identification of common viral
integration sites in BXH-2 leukaemia. Here, we describe a new approach for
proviral tagging that greatly facilitates the identification of BXH-2 leukaemia
genes. Using this approach, we identify three genes whose expression is
activated by proviral integration in BXH-2 leukaemias; Hoxa7, Hoxa9, and a
Pbx1-related homeobox gene, Meis1. Proviral activation of Hoxa7 or Hoxa9 is
strongly correlated with proviral activation of Meis1 implying that Hoxa7 and
Hoxa9 cooperate with Meis1 in leukaemia formation. These studies provide the
first genetic evidence that Pbx1-related genes cooperate with Hox genes in
leukaemia formation and identify a number of new murine myeloid leukaemia genes.

PMID: 8563752 [PubMed - indexed for MEDLINE]


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