Transcript HOX A9 in Acute Myeloid Leukemia (AML)

HOX A9: Connections to
Acute Myeloid Leukemia
Doug Ornoff
BIOL 169
03 21 06
Summary
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Acute myeloid leukemia (AML) is a cancer of the bone
marrow that produces WBCs, and results in a proliferation of
nonfunctional leukocytes that interfere with normal blood
cell function.
HOXA9 normally functions in skeletal patterning along the
anteroposterior (A-P) axis, and in proper natural
hematopoiesis.
Various chromosomal translocations result in either
upregulation of the HOXA9 gene or creation of a fusion
protein.
Result is a transcriptional increase in hematopoietic
proliferative proteins and a decrease in proteins promoting
leukocyte differentiation
Future treatment options lie in regulating cofactors necessary
for HOXA9 function.
Acute Myeloid Leukemia (AML)
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A leukemia, thus affecting
the blood and bloodforming organs
Leukemias cause an
abnormal increase in the
number of leukocytes,
specifically the
neutrophils, eosinophils,
basophils, and monocytes
Results in a population of
immature white blood cells
that fail to respond to
death signals, accumulate,
spill out into the blood,
travel to other areas, and
interfere with normal cell
function.
Above: Normal human leukocytes. Univ. of Western Australia
Below: Leukocytes from bone marrow of AML patient. UVA Medical.
AML Symptoms
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Pallid complexion
Anemia, due to disrupted erythrocyte function
Mild fever, frequent mild infections
Prolonged bleeding from gums and from
minor cuts due to platelet disruption
Fatigue and shortness of breath
Excessive bruising and spotting of the skin
Hematological Signs of AML
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Crowding of normal bone
marrow by proliferating
nonfunctional WBCs
Anemia, as evid. by low
hemoglobin & hematocrit
Neutropenia / granulocytopenia
(not enough granulocytes), as
evid. by increased susceptibility
to normal infections
Thrombocytopenia (too few
platelets)
Shortage of normal WBC
(leukopenia), but high numbers
of nonfunctional undifferentiated
WBCs (leukocytosis)
www.lymphomation.org
Current Treatment Options
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Surgery not an option, since leukemia cells not confined to
any one body region
Chemotherapy utilizes drugs aimed at disrupting cell
division; affects diseased bone marrow and mutated
hematopoietic cells especially
Common chemo drugs are cytarabine (ara-C) and an
anthracycline, such as daunorubicin or idarubicin.
Bone marrow or peripheral blood stem cell transplantation
used to recover hematopoiesis
Immunotherapy using monoclonal antibodies targeted at
AML cells becoming useful, and new methods use Abs with
radioactive or toxic groups attached.
Normal HOXA9 Function – Skeletal Patterning
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HOXA9 is involved in
mice in skeletal patterning
and development along the
anteroposterior (A-P) axis.
Double mutant phenotype
features supernumerary
ribs, as well as
anteriorization of the lower
thoracic and lumbar and
saccral vertebrae.
Fromental-Ramain et al.
Normal HOXA9 Function – Skeletal Patterning
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Murine vertebrae
Left column: HOXA9 -/Right column: WT
Fromental-Ramain et al.
HOXA9 at the subcellular level
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First and foremost, it’s a
transcription factor!
Interactions with cofactors
Meis1 and Pbx1 help recruit
other coactivators or
corepressors that turn on/off
genes
One important role involves the
coactivator CBP, which allows
CREB to bind and stimulate
RNA PolII
Above: HoxA9 (H) recruiting coactivator (CoA) along with cofactor (Co).
Below: HoxA9 (H) recruiting corepressor (CoR) or inhibiting coactivator (CoA).
Owens et al. Stem Cells 2002; 20:364-379.
Normal HOXA9 Function –Hematopoiesis
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Within the
organism,
HOXA9 is
further involved
in hematopoiesis,
playing a role in
the regulation of
both blood stem
cell proliferation
AND
differentiation.
Gilliland, Gary. “Molecular Paradigims/Mechanisms in Acute Myeloid
Leukemia.” State of the Science Leukemia Conference. National Cancer
Institute, 2000
Normal HOXA9 Function –Hematopoiesis
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Proliferation,
followed by
differentiation,
produces
mature
functional
leukocytes.
Dr. Thomas Graf, Albert Einstein
College of Medicine
Normal HOXA9 Function –Hematopoiesis
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Lawrence et al
constructed
knockout mice
and noted that
the mice had
disrupted
hematopoiesis
and lower
numbers of
WBCs,
lymphocytes,
and
granulocytes
Lawrence et al.
Abnormal HOXA9 Gene Function
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Abnormal gene function is
almost always related to a
chromosomal translocation
The translocation affects
HOXA9 gene in one of three
ways:
upregulation due to
MLL overexpression
overexpression due to
promoter placement
overlay resulting in
fusion protein
EX. HOXA9-NUP98 fusion
Progression to Cancer – Human/Mouse
Homologies in HOXA9
Mus musculus (top)
Homo sapiens (bottom)
1 mattgalgny yvdsfllgad aadelgagry apgtlgqppr qaaAlaehpd fspcsfqska
1 mattgalgny yvdsfllgad aadelsvgry apgtlgqppr qaaTlaehpd fspcsfqska
61 avfgaswnpv haaganavpa avyhhhhhpy vhpqapvaaa apdgrymrsw leptpgalsf
61 tvfgaswnpv haaganavpa avyHhhhhhpy vhpqapvaaa apdgrymrsw leptpgalsf
121 aglpssrpyg ikpeplsarr gdcptldtht lsltdyacgs ppvdrekqps egafsennae
121 aglpssrpyg ikpeplsarr gdcptldtht lsltdyacgs ppvdrekqps egafsennae
181 nesggdkppi dpnnpaanwl harstrkkrc pytkhqtlel ekeflfnmyl trdrryevar
181 nesggdkppi dpnnpaanwl harstrkkrc pytkhqtlel ekeflfnmyl trdrryevar
241 llnlterqvk iwfqnrrmkm kkinkdrakd e
241 llnlterqvk iwfqnrrmkm kkinkdrakd e
Progression to Cancer – HOXA9 and Pbx1
Progression to Cancer – NUP98-HOXA9 fusion
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Kroon et al. went on to demonstrate that mice
transfected with bone marrow containing a
NUP98-HOXA9 fusion were induced into an
AML phenotype.
They also found that when fusion transfection
was done alongside overexpression of Meis1,
AML onset was accelerated.
Progression to Cancer – An Rb Analogy
Structural Insights
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Further structural studies on a
HOXA9/Pbx1/DNA complex
by LaRonde-LeBlanc et al.
revealed that the HOXA9/Pbx1
pair binds to DNA with high
affinity
Binding is stronger than other
HOX/DNA complexes due to
major and minor groove
interactions.
DNA recognition sequences
are also embedded in the
HOXA9/Pbx1 structure.
HOXA9 and PBX 1 bound to DNA. 1.90A.
RCSB Protein Data Bank
Structural Insights
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Additionally, Kasper et al found that the 38
conserved FG repeats in a domain of NUP98
were responsible for CBP binding and
subsequent recruitment of CREB.
Their studies showed that in fusion with
HOXA9, the FG repeats were preserved.
Interestingly, the fusion results in a deletion of
a portion of the HOXA9 N-terminus that has
transcription repression properties.
Current Research and Future Treatment Options
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Further elucidate the interaction between the NUP98-HOXA9
fusion and Meis1
Understand the role between HOXA9 expression and MLL
Continue investigations on the Core Binding Factor subunit
(CBFα, aka AML1, and CBFβ) (CBF recruits CRB, which
recruits CREB)
The large number of ways that the HOXA9 pathway can
become improperly activated also provides a large number of
ways that it can be therapeutically targeted.
Work is underway to try to disrupt the co-activator and corepressor systems.
Perhaps another option is to consider disrupting the
HOXA9/DNA binding, or to hyperactivate the differentiation
pathway.
Summary
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Acute myeloid leukemia (AML) is a cancer of the bone
marrow that produces WBCs, and results in a proliferation
of nonfunctional leukocytes that interfere with normal
blood cell function.
HOXA9 normally functions in skeletal patterning along the
anteroposterior (A-P) axis, and in proper natural
hematopoiesis.
Various chromosomal translocations result in either
upregulation of the HOXA9 gene or creation of a fusion
protein.
Result is a transcriptional increase in hematopoietic
proliferative proteins and a decrease in proteins promoting
leukocyte differentiation
Future treatment options lie in regulating cofactors
necessary for HOXA9 function.
References
American Cancer Society. “Acute Myeloid Leukemia.” Cancer Reference Information.
http://www.cancer.org/docroot/CRI/CRI_2_1x.asp?rnav=criov&dt=82
Leukemia and Lymphoma Society. “Acute Myeloid Leukemia.” Disease Information.
http://www.leukemia-lymphoma.org/all_page?item_id=8459
Cancer Genetics Web. HoxA9 lookup. http://www.cancerindex.org/geneweb/HOXA9.htm
Gilliland, Gary. “Molecular Paradigims/Mechanisms in Acute Myeloid Leukemia.” State of the Science
Leukemia Conference. National Cancer Institute, 2000.
http://www.webtie.org/sots/Meetings/Leukemia/02-01-2000/transcripts/gilliland/Transcript.htm
Owens, Bronwyn M. and Hawley, Robert H. HOX and Non-HOX Homeobox Genes in Leukemic
Hematopoiesis. Stem Cells 20: 364-379. 2002
Fromental-Ramain, Catherine et al. Specific and redundant functions of the paralogous Hoxa-9 and
Hoxd-9 genes in forelimb and axial skeleton patterning. Development 122, 461-472. 1996
Kasper, LH. et al. CREB binding protein interacts with nucleoporin…Mol Cell Bio. 1999, 19: 764-776.
LaRonde-LeBlanc et al. Structure of HoxA9 and Pbx1 bound to DNA: Hox hexapeptide and DNA
recognition anterior to posterior. Genes and Development 17:2060-2072, 2003
Lawrence, HJ et al. Mice bearing a targeted disruption… Blood 1997;89:1922-1930.
Nakamura et al. Cooperative activation of HOXA and Pbx1-related genes in murine myeloid leukemias.
Nat Genetics 1996;12:149-153
Kroon E et al. NUP98-HOXA9 expression in hematopoietic stem cells induces chronic and acute myeloid
leukemias in mice. EMBO J 2001;20;350-361.