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2009 Vienna - European Society of Human Genetics

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Cancer genetics<br />

P06.177<br />

somatically acquired JAK mutations in adult acute<br />

lymphoblastic leukemia<br />

E. Flex 1 , V. Petrangeli 1 , L. Stella 2 , S. Chiaretti 3 , T. Hornakova 4 , L. Knoops 4 , F.<br />

Paoloni 3 , V. Cordeddu 1 , M. Sanchez 1 , G. Cazzaniga 5 , A. Tornesello 6 , M. Vignetti<br />

3 , J. Renauld 4 , A. Biondi 5 , S. N. Constantinescu 4 , R. Foà 3 , M. Tartaglia 1 ;<br />

1 Istituto Superiore di Sanità, Rome, Italy, 2 Università “Tor Vergata”, Rome, Italy,<br />

3 Università “La Sapienza”, Rome, Italy, 4 Université catholique de Louvain, Bruxelles,<br />

Belgium, 5 Università di Milano Bicocca, Monza, Italy, 6 Università Cattolica<br />

del Sacro Cuore, Rome, Italy.<br />

Aberrant signal transduction contributes substantially to leukemogenesis.<br />

Here, we report that somatic mutations in the Janus kinase 1<br />

(JAK1) gene, which encodes a cytoplasmic tyrosine kinase that noncovalently<br />

associates with a variety <strong>of</strong> cytokine receptors and plays<br />

a nonredundant role in lymphoid cell precursor proliferation, survival<br />

and differentiation, occur in individuals with acute lymphoblastic leukemia<br />

(ALL). JAK1 mutations were more prevalent among adult subjects<br />

with T-cell precursor ALL, where they accounted for 18% <strong>of</strong> cases,<br />

and were associated with advanced age at diagnosis, poor response<br />

to therapy and overall prognosis. All mutations were missense, some<br />

predicted to destabilize interdomain interactions controlling the activity<br />

<strong>of</strong> the kinase. Three mutations that were studied promoted JAK1 gain<br />

<strong>of</strong> function, and conferred interleukin 3-independent growth in Ba/F3<br />

cells and/or interleukin 9-independent resistance to dexamethasoneinduced<br />

apoptosis in T cell lymphoma BW5147 cells. Such effects<br />

were associated with variably enhanced activation <strong>of</strong> multiple downstream<br />

signaling pathways. Leukemic cells with mutated JAK1 alleles<br />

shared a gene expression signature characterized by transcriptional<br />

upregulation <strong>of</strong> genes positively controlled by JAK signaling. Our findings<br />

implicate dysregulated JAK1 function in ALL, particularly <strong>of</strong> T-cell<br />

origin, and point to this kinase as a target for the development <strong>of</strong> novel<br />

anti-leukemic drugs.<br />

P06.178<br />

study <strong>of</strong> the effect <strong>of</strong> mRP1 gene polymorphisms on its mRNA<br />

expression in acute leukemic patients<br />

S. Rezvani, F. Mahjubi, M. Montazeri;<br />

National Institute <strong>of</strong> Genetic Engineering&Biotechnology(NIGEB), Tehran, Islamic<br />

Republic <strong>of</strong> Iran.<br />

One <strong>of</strong> the major problems in treating cancer cells is that they can<br />

acquire drug resistance (so called Multidrug Resistance: MDR). There<br />

are several mechanisms responsible for MDR. One <strong>of</strong> the most important<br />

is the overexpression <strong>of</strong> ABC transporter genes. One <strong>of</strong> the most<br />

extensively studied genes involved in MDR is multidrug resistance protein<br />

1 (MRP1). We have shown that the overexpression <strong>of</strong> this gene is<br />

associated with the MDR in Iranian leukemic patients. However, MRP1<br />

gene amplification could not be identified in any <strong>of</strong> those patients. Another<br />

mechanism is the influence <strong>of</strong> the MRP1 gene polymorphisms on<br />

the expression level <strong>of</strong> the gene.<br />

We aimed to investigate the possible association between the expression<br />

level <strong>of</strong> MRP1 and occurrence <strong>of</strong> MDR in leukemic patients. Furthermore,<br />

we wished to test the hypothesis that MRP1 polymorphisms<br />

would be predictive <strong>of</strong> MDR in patients with acute leukemia. mRNA<br />

level <strong>of</strong> MRP1 was determined in 111 patients with acute leukemia<br />

(including 52 patients with AML and 59 patients with ALL) by quantitative<br />

real time RT-PCR and compared to the type <strong>of</strong> response to<br />

chemotherapy.<br />

We typed G816A,T825C,G2168A,C2217T,G2268A,G1299T,G-260C,<br />

A-275G MRP1 polymorphisms in those patients classified either drugresistant.<br />

We found that high expression <strong>of</strong> MRP1 was associated with<br />

MDR phenotype in both AML and ALL patients. There was no effect <strong>of</strong><br />

a particular genotype on the expression level <strong>of</strong> the MRP1 gene. This<br />

could show the lack <strong>of</strong> dependency <strong>of</strong> any <strong>of</strong> these genotypes on the<br />

chemosensivity in this group <strong>of</strong> patients.<br />

P06.179<br />

Expression analysis <strong>of</strong> the mitogenic growth factor receptors<br />

in childhood acute myeloid leukemia; increased Expression <strong>of</strong><br />

Vascular Endothelial Growth Factor Receptor-1 and the Loss <strong>of</strong><br />

Estrogen Receptor beta<br />

F. Atalar 1 , T. A. Tekiner 2 , S. Anak 3 , U. Ozbek 4 ;<br />

1 Istanbul University, Istanbul Medical Faculty, Child Health Institute, Pediatric<br />

Endocrinology Department, Istanbul, Turkey, 2 Istanbul Technical University,<br />

Molecular Biology and <strong>Genetics</strong> Department, Istanbul, Turkey, 3 Istanbul University,<br />

Istanbul Medical Faculty, Department <strong>of</strong> Pediatric Hematology and Oncology,<br />

Istanbul, Turkey, 4 Istanbul University, Institute <strong>of</strong> Experimental Medical<br />

Research (DETAE), <strong>Genetics</strong> Department, Istanbul, Turkey.<br />

Constitutive PI3K/Akt/mTOR signaling is upregulated by the activating<br />

mutations <strong>of</strong> receptor tyrosine kinases, autocrine/paracrine secretion<br />

<strong>of</strong> growth factors and estrogens triggering the binding <strong>of</strong> ERα to<br />

PI3K and ERβ to AKT.Mutational analysis <strong>of</strong> FLT3 together with the<br />

expression analysis <strong>of</strong> VEGF receptors, estrogen receptors and IGF<br />

system were performed in pediatric AML (pAML) patients and controls,<br />

CD33+ cells isolated from healthy bone marrows.FLT3/ITD and FLT3/<br />

D835 mutations have been identified in 12% and 2 % <strong>of</strong> 50 pAML<br />

patients respectively.Flt-1 and KDR expression were determined to be<br />

significantly higher in pAML patients.ERα expression was observed in<br />

54.5% <strong>of</strong> the patients where diminished ERβ expression was determined.The<br />

results <strong>of</strong> the IGF system genes expression studies indicated<br />

higher IGF-1 expression(16.3 fold), and significantly lower IGF-2<br />

and IGF-1R expressions in pAML patients.IGFBP-rP1 expression was<br />

10.48 fold lower in pAML patients.Expression studies <strong>of</strong> initiator caspases,<br />

caspase8 and caspase9 revealed low level <strong>of</strong> caspase9 and<br />

increased level <strong>of</strong> caspase8(13.6 fold) expression in pAML patients.<br />

IGFBP-rP1 and caspase8 expressions were also evaluated by western<br />

blot analysis in pAML samples.Upregulation <strong>of</strong> PI3K/Akt pathway<br />

through altered expression levels <strong>of</strong> upstream mitogenic growth factors<br />

and their receptors were also confirmed by altered expression<br />

levels <strong>of</strong> Akt downstream genes; c-myc and cyclin D1 as a result <strong>of</strong><br />

GSK3ß phosphoinhibition in pAML patients.To our knowledge this is<br />

the first data representing the loss <strong>of</strong> ERβ gene expression in pediatric<br />

AML patients.Our study showed that IGF-1 and caspase8 could be<br />

potential antiapoptotic markers and IGFBP-rP1 a new tumor suppressor<br />

in pAML.<br />

P06.180<br />

study <strong>of</strong> suz12 gene expression in chronic myelogenous<br />

leukemia patient<br />

M. Ghalandary 1 , B. Hassannia 1 , M. Behmanesh 1 , M. T. Akbari 2 ;<br />

1 Department <strong>of</strong> <strong>Genetics</strong>, Faculty <strong>of</strong> Basic Science,Tarbiat Modares University,<br />

Tehran, Islamic Republic <strong>of</strong> Iran, 2 Department <strong>of</strong> Medical <strong>Genetics</strong>, Faculty <strong>of</strong><br />

Basic Science,Tarbiat Modares University, Tehran, Islamic Republic <strong>of</strong> Iran.<br />

Polycomb group proteins are transcriptional repressors that play a<br />

central role in the establishment and maintenance <strong>of</strong> gene expression<br />

patterns during development. Trimethylation <strong>of</strong> histone H3 on lysine<br />

27, mediated by a PcG protein complex consisting <strong>of</strong> Eed, Ezh2, and<br />

Suz12, is integral in differentiation, stem cell self-renewal, and tumorigenesis.<br />

Deregulated activity <strong>of</strong> the chromatin remodeling Polycomb<br />

Repressive Complex 2 (PRC2) has recently been shown to be a frequent<br />

event in human tumors. Recent study shows that loss <strong>of</strong> Suz12, a<br />

core component <strong>of</strong> Polycomb Repressive Complex 2 (PRC2), function<br />

enhances hematopoietic stem cell (HSC) activity. Their study suggests<br />

that PRC2 is required to maintain a specific gene expression pattern<br />

in hematopoiesis that is indispensable to normal stem cell function.<br />

Chronic myelogenous leukemia (CML) is a clonal myeloproliferative<br />

disorder <strong>of</strong> the hematopoeitic stem cell (HSC).<br />

In this study the expression level <strong>of</strong> Suz12 gene was compared between<br />

CML patiens and control group. In this report we will present the<br />

obtained results.<br />

P06.181<br />

Fluorescence in situ Hybridization Analysis <strong>of</strong> the htERc<br />

Region in Acute myeloid Leukemia Patients<br />

O. Ozer, T. Bulakbasi Balci, Z. Yilmaz, F. I. Sahin;<br />

Baskent University Faculty <strong>of</strong> Medicine Department <strong>of</strong> Medical <strong>Genetics</strong>, Ankara,<br />

Turkey.<br />

Telomerase is a ribonucleoprotein complex consisting <strong>of</strong> reverse<br />

transcriptase (hTERT), proteins (hTP1) and RNA template for telomeric<br />

DNA synthesis (hTERC). The telomerase RNA component<br />

(TERC) gene is located at 3q26. Increased TERC gene dosage has<br />

been detected frequently in a variety <strong>of</strong> human cancers, suggesting<br />

a growth advantage in cells with increased gene dosage. Amplification<br />

was shown by fluorescence in situ hybridization (FISH) in different<br />

cancers. It has been suggested that the activation <strong>of</strong> telomerase<br />

in leukemic cells may be connected with amplification <strong>of</strong> hTERT and<br />

hTERC genes. The aim <strong>of</strong> this study was to investigate whether there<br />

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