2008 Barcelona - European Society of Human Genetics

Cancer genetics
P04.029
characterisation of familial breast tumours using array-based
comparative genomic hybridisation technology: the common
heterogeneity with sporadic breast tumours
L. Melchor1 , E. Honrado1 , M. J. García1 , S. Álvarez2 , A. Osorio1 , K. L. Nathanson3
, J. Benítez1 ;
1Human Genetics Group, Human Genetics Programme, Spanish National
Cancer Centre (CNIO), Madrid, Spain, 2Molecular Cytogenetics Group, Human
Genetics Programme, Spanish National Cancer Centre (CNIO), Madrid, Spain,
3Division of Medical Genetics, Department of Medicine and Abramson Cancer
Center, University of Pennsylvania, Philadelphia, PA, United States.
Familial breast cancer (~5% of breast cancer cases) maybe due to
mutations at the BRCA1 and BRCA2 genes (~30% of families with
breast cancer) or to mutations in other unknown genes to date in the
non-BRCA1/2 or BRCAX families (~70%) . To characterise the genomic
differences amongst the distinct breast cancer classes using the
array-based comparative genomic hybridization technique, we have
collected 20 tumours associated with BRCA1 mutation, 24 tumours
from mutation carriers in BRCA2, 32 BRCAX-tumours, and 19 sporadic
samples .
Breast tumours associated with mutations in BRCA1 or BRCA2 had
greater genomic instability than BRCAX or sporadic samples, and a
trend to alter specific chromosomal regions. However, we have demonstrated
a common heterogeneity between familial and sporadic breast
cancer in terms of estrogen receptor (ER) status and breast cancer
subtypes . First, ER-negative tumours showed higher genomic instability
and a specific genomic aberration pattern compared with ER-positive
tumours. Second, familial breast tumours have been profiled into
molecular subtypes: basal, ERBB2, luminal A, and luminal B . BRCA1tumours
were associated with the basal phenotype, which presented
the highest genomic instability, whereas BRCAX samples were related
to the luminal A subtype . Luminal B tumours had the greatest number
of high-level DNA amplifications.
Two regions with high-level DNA amplifications in familial breast cancer
have also been studied: 8p11-p12 and 13q34 . The former one was
related to higher cell proliferation, whereas the latter one was characteristic
of basal tumours, had 1’6Mb length, and was correlated with
overexpression of candidate genes such as TFDP1 .
P04.030
BAX gene mutations and Breast carcinoma: A study of
phenotype-genotype correlation
M. Hosseini 1 , M. Houshmand 2 , K. Banihashemi 3 , M. Sayedhassani 4 ;
1 Islamic Azad University, Tehran, Islamic Republic of Iran, 2 National Institute for
Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran, Tehran, Islamic
Republic of Iran, 3 GPEF, MSRP, Tehran, Islamic Republic of Iran, 4 Research
and clinical center for infertility of Yazd, Yazd, Iran., Tehran, Islamic Republic
of Iran.
It has been known for a while that the proapoptotic BAX protein induces
cell death by acting on mitochondria and its gene is located
on 19q13 .3-q13 .4 . On the other hand it has been demonstrated that
BAX can be essential for death receptor-mediated apoptosis in cancer
cells
In this study a kind of phenotype-genotype correlation research for
breast carcinoma and BAX gene mutations has been done . The correlation
between breast cancer stage and its prognosis has been evaluated
with the mutation types of the BAX and their statistical analyses
were the matter of interest through a series of clinical and genetic
variables . The sample consists of 50 female patients with mean age
of 40-50 . who involved with Breast Cancer compared to a healthy control
group of the same race and ethnicity with approximately the same
mean age who also never had a history of breast cancer in their close
relatives .
Our study shows some basic findings to make a Bax mutation database
phenotypically interrelated with the clinical prognoses which
could be a fundamental guide to clinical treatment options through a
series of genetic screening .
P04.031
Preliminary genetic investigations of BRcA genes within
hereditary breast and ovarian cancer (HBOc) families in northeastern
Romania
L. Negura 1 , E. Carasevici 1 , A. Negura 2 , N. Uhrhammer 3 , Y. J. Bignon 3 ;
1 Gr. T. Popa Medicine and Pharmacy University, IASI, Romania, 2 Al. I. Cuza
University, IASI, Romania, 3 Jean Perrin Molecular Oncology Center, Clermont-
Ferrand, France.
BRCA1 and BRCA2 are major cancer predisposition genes, responsible
for a large percentage of hereditary breast and ovarian cancer
(HBOC) families . Screening for mutations in these genes is now standard
practice for HBOC cases in Europe, and permits medical followup
and genetic counselling adapted to the needs of individuals in such
families . As very little information is available in Romania, we started
the first characterization of hereditary breast and ovarian cancer risk
in north-eastern Romania . Our study consists in HBOC families identification
and recruitment, DNA collection achievement from these patients,
implementation of molecular technology for mutations analysis
and oncogenetic follow-up of mutations bearers .
We managed to identify and recruit so far several HBOC families with
unique features such as 5 ovarian plus 1 breast cancer, or 8 breast
cancer cases within the same family line . All recruited families are now
under systematic DNA sequencing for BRCA screening .
We also investigated, within HBOC families and sporadic cases, the
status of three known founder mutations (185delAG and 5382insC on
BRCA1 and 6174delT on BRCA2), by optimization and comparison
of several multiplex-PCR techniques . This part of our study showed
a very important random factor within all multiplex-PCR methods . We
demonstrate that although they are cheap, rapid and easy techniques,
they often generate false results like primer dimmers, undesirable amplification
products apparition or heteroduplexes. Therefore we always
recommend combining multiplex-PCR with other pre-screening methods
(SNP, heteroduplex analysis) for a good selection before DNA sequencing
.
Our study was possible by financial support from Romanian Academy
.
P04.032
implementation of a comprehensive strategy for mutational
analysis of BRCA and BRCA genes in our clinical setting:
Description of the algorithm and preliminary results
J. del Valle, L. Feliubadaló, E. Tornero, M. Menéndez, M. Mirete, E. Montes, M.
Calaf, G. Capellà, C. Lázaro;
Laboratori Recerca Translacional, Institut Català d’Oncologia, Hospitalet de
Llobregat, Barcelona, Spain.
We have recently set up an accurate and cost-effective strategy to
screen for variations in the BRCA1 and BRCA2 genes . Our algorithm
consists in a sequential cascade of complementary techniques using
genomic DNA . First, we study copy number variations by using commercial
MLPA kits (MRC-Holland) . Samples showing positive MLPA
results are always confirmed by a different approach. Samples with
no copy number variations undergo SNPlex analysis, designed specifically
to detect 38 Spanish common polymorphisms and 9 recurrent
mutations. Direct sequencing is applied to confirm recurrent mutations.
Negative samples for the previous steps are submitted to our chosen
technique for mutational search for nucleotide changes, the CSCE
approach (conformation sensitive capillary electrophoresis) . CSCE
analysis allows detecting altered electrophoresis patterns when DNA
changes are present in heterozygosis in a given fragment . The screening
of the whole coding region of both genes is performed by analysing
79 different fragments . Abnormal patterns are sequenced to determine
the DNA change responsible for the observed mobility shift . When a
DNA change is suspected to alter the correct splicing of the genes,
mRNA studies are performed . We are applying this comprehensive
approach since July 2007 in our routine setting and although numbers
are still too low, results are promising and comparable to those reported
in the literature . We detected about 2-3% copy number alterations,
3-5% recurrent mutations and 15-18% point mutations in a selected
population of high-risk patients . Several mutations affecting the splicing
have been also characterized at mRNA level .