2008 Barcelona - European Society of Human Genetics

Concurrent Sessions
MYCN , E2F3 and CDH11) . Our results showed that some genomic
rearrangements thought to belong only to RB (Dup6p including E2F3,
gains of MDM4 and MYCN) are already present in retinoma . Tumor
tissues show a higher level of genomic instability, with additional rearrangements
and progressive amplification of E2F3 and MYCN . Interestingly,
in one of the two RB cases, we found a deletion in 16q12 .1-
16q12, absent in retinoma . This region includes RBL2 (p130), an efficient
inducer of cellular senescence when the major arrest pathway
determined by pRb/p16INK4a is abolished . In conclusion, these data
confirm the pre-malignant nature of retinoma and indicate interesting
candidate genes that could have a key role in the progression to malignancy
.
c10.3
High resolution analysis of chromosomal changes in colorectal
tumors matched with normal tissues from the same patients
using 500,000 sNPs
G. Brown 1,2 , D. L. Worthley 3,4 , G. P. Young 3 , D. Brookes 1,2 , J. Ross 1,2 , G. N.
Hannan 1,2 ;
1 CSIRO Preventative Health Flagship, North Ryde, NSW, Australia, 2 CSIRO
Molecular and Health Technologies, North Ryde, NSW, Australia, 3 Flinders
Medical Centre, Bedford Park, SA, Australia, 4 Queensland Institute of Medical
Research, Herston, Qld, Australia.
Previous studies have identified many chromosomal abnormalities
which occur amongst common colorectal cancers (CRCs) . Until now
these have been observed using fairly low resolution screening technologies
so that it has been difficult to match changes to specific genes
or to specific pathways. Another confounding issue has been the use
of composite reference sets of “normal” DNAs to identify changes in
tumor DNAs, leading to greater background noise in the estimations
of copy number (CN) and loss of heterozygosity (LOH) . We have used
microarrays containing probes for 500,000 single nucleotide polymorphisms
(SNPs) in genome wide scans to provide very high resolution
estimations of CN change and LOH for each of five pairs of common
colorectal tumors, pair-wise matched with normal tissues from the
same patients. We show that pair-wise matching gave better definition
of CN changes and regions of LOH than by comparing the tumor
genome profiles against a composite genome profile derived from a
reference set of 40 normal individuals . Our high resolution data allowed
precise identification of many chromosomal changes in CRC
tumors. We also report improved definition of some changes that have
been observed previously using lower resolution methods . We show
the importance of having LOH data as well as CN data to better understand
the mechanisms involved in chromosomal rearrangements
in CRC . These include likely instances of hemizygous deletions, gene
conversions and uniparental disomy . We also present our analysis of
regions gained, lost or showing LOH, that contain genes potentially
involved in CRC .
c10.4
Leukemia biochip analysis of chromosomal translocations in
childhood leukemia in Russia using hybridization and on-chip
PcR approaches.
N. A. Guseva, O. S. Nurutdinova, A. V. Chudinov, E. N. Timofeev, S. V. Pankov,
A. S. Zasedatelev, T. V. Nasedkina;
Engelhardt Institute of Molecular Biology RAS, Moscow, Russian Federation.
Leukemia is a clinically and genetically heterogeneous disease that
requires accurate molecular diagnostic approaches to generate treatment
strategies and to minimize toxicity of therapies .
Here we present biochip diagnostic tool to detect 14 most significant
translocations of childhood leukemia together with quantitative
approach to evaluate minimal residual disease (MRD) . Biochips are
three-dimensional oligonucleotide microchips consisting of gel pads
attached to a hydrophobic plastic surface . For diagnostics of primary
leukemia, the multiplex RT-PCR was used in combination with hybridization
on biochips . The quantitative method was based on real-time
on-chip PCR, which allowed identification of chimeric transcript copies,
as measured by PCR-synchronized fluorescent microscope. The data
obtained by on-chip PCR method for t(8;21) patients was validated by
conventional real-time PCR . Leukemia biochip was used to screen 753
children from newborn up to 17 years . In total of 501 primary ALL children
we found translocations in 23% of cases (69 children with t(12;21)
TEL/AML, 23 with t(9;22) BCR/ABL p190, 12 with t(1;19) E2A/PBX,
12 with (4;11) MLL/AF4, 4 with t(10;11) MLL/AF10), 1 with t(11;19)
MLL/ELL and 1 with t(11;19) MLL/ENL); in total of 201 AML patients
there were 33% with translocations (21 with t(9;11) MLL/AF9, 19 with
t(8;21) AML/ETO, 16 with t(15;17) PML/RARA, 8 with inv16 and 4 with
t(6;11) MLL/AF6); 24 children with CML had t(9;22) BCR/ABL p210
and of 27 with non-Hodgkin lymphomas 4 (15%) had t(2;5) NPM/ALK .
In conclusion, we developed a biochip platform to diagnose primary
leukemia and to monitor MRD that is fast, accurate, convenient and
cost-effective .
c10.5
Disruption of Ikaros function by the CALM/AF10 fusion protein
might be responsible for abortive lymphoid development in
CALM/AF10 positive leukemia
P. A. Greif, B. Tizazu, A. Krause, E. Kremmer, S. K. Bohlander;
HelmholtzZentrum München, München, Germany.
The t(10;11)(p13;q14) translocation leads to the fusion of the CALM
and AF10 genes . This translocation can be found as the sole cytogenetic
abnormality in acute lymphoblastic leukemia, acute myeloid
leukemia and in malignant lymphomas . The expression of CALM/AF10
in primary murine bone marrow cells results in the development of an
aggressive myeloid leukemia that is propagated by cells with lymphoid
traits (Deshpande et al, Cancer Cell, 2006) . Using a yeast two-hybrid
screen, we identified the lymphoid regulator Ikaros as an AF10 interacting
protein . Interestingly, Ikaros is required for normal development
of lymphocytes, and aberrant expression of Ikaros has been found in
leukemia . In a murine model, the expression of a dominant negative
isoform of Ikaros causes leukemias and lymphomas . The Ikaros interaction
domain of AF10 was mapped to the leucine zipper domain
of AF10, which is required for malignant transformation both by the
CALM/AF10 and the MLL/AF10 fusion proteins . The interaction between
AF10 and Ikaros was confirmed by GST pull down and co-immunoprecipitation
. Coexpression of CALM/AF10 but not of AF10 alters
the subcellular localization of Ikaros in murine fibroblasts (Greif et al,
Oncogene, in Press) . The transcriptional repressor activity of Ikaros is
reduced by AF10 . These results suggest that CALM/AF10 might interfere
with normal Ikaros function, and thereby block lymphoid differentiation
in CALM/AF10 positive leukemias .
c10.6
Assessment of X chromosome inactivation Pattern in BRCA
mutation carriers: Evidence for an Effect of chemotherapy
M. Miozzo 1 , C. Allemani 2 , F. R. Grati 3,1 , S. M. Tabano 1 , B. Peissel 4 , P. Antonazzo
5 , V. Pensotti 6 , S. M. Sirchia 1 , P. Radice 6,7 , S. Manoukian 4 ;
1 Medical Genetics, Department of Medicine, Surgery and Dentistry, University
of Milan, Milan, Italy, 2 Analytical Epidemiology Unit, Department of Preventive
and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori,
Milan, Italy, 3 Units of Research and Development, Cytogenetics and Molecular
Biology, TOMA Laboratory, Busto Arsizio, Italy, 4 Medical Genetics Unit, Department
of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei
Tumori, Milan, Italy, 5 Institute of Obstetrics and Gynecology I “L. Mangiagalli”,
University of Milan, Fondazione IRCCS Policlinico, Mangiagalli and Regina
Elena, Milan, Italy, 6 Fondazione Istituto FIRC di Oncologia Molecolare, Milan,
Italy, 7 Genetic Susceptibility to Cancer Unit, Department of Experimental Oncology,
Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
BRCA1, a major breast/ovarian cancer predisposing gene, has been
suggested to play a role in the mechanisms leading to X chromosome
inactivation (XCI) in female cells . In addition, a high frequency of nonrandom
(skewed) XCI was reported in carriers of BRCA1 mutations affected
with ovarian cancer . To verify whether constitutional alterations
of the gene may influence XCI status, we analyzed the occurrence of
skewed XCI in blood cells from 224 female BRCA1 mutations carriers,
both with and without cancer, and 177 healthy controls. Significant reduced
odds of skewed XCI respect to controls were found in younger
carriers (