2008 Barcelona - European Society of Human Genetics

Cancer genetics
P04.064
Dissection of allelic molecular pathology of the SEMA B gene
frequently altered in breast cancer
E. A. Pudova 1 , E. B. Kuznetsova 1,2 , L. E. Zavalishina 3 , G. A. Frank 3 , D. V. Zaletaev
1,2 , V. V. Strelnikov 1,2 ;
1 Research Centre for Medical Genetics, Moscow, Russian Federation, 2 Sechenov
Moscow Medical Academy, Moscow, Russian Federation, 3 Moscow
P.A.Gertsen Oncology Research Institute, Moscow, Russian Federation.
We have assessed promoter methylation, altered expression and allelic
imbalance of the SEMA6B gene in sporadic breast cancer and
report that at least one of these molecular alterations is found in 75%
of tumors . Taken separately, allelic imbalance was demonstrated in a
half of all tumor samples, reduced expression and abnormal promoter
methylation in 40% each . At the same time, the features supposed
to be in close relation to each other, such as allelic imbalance and
expression and/or promoter methylation and expression were poorly
correlated . Several samples demonstrated intact gene expression in
the presence of methylation and/or allelic imbalance and vice versa,
questioning functional interactions between these parameters . Similar
observations were made for several other candidate tumor suppressor
genes, including another member of the semaphorin family, SEMA3B .
We suggest that this may be a result of a nonallelic approach, where
each form of molecular pathology is analyzed in the sample as a
whole, without allelic discrimination . We have developed assays to
assess allelic alterations based on a minisequencing technique in its
SnaPshot modification (Applied Biosystems, USA). Having elaborated
a coding intragenic SNP rs2304213 with heterozygosity close to 50%
we have evaluated allelic imbalance and patterns of allelic methylation
and gene expression in 22 informative samples of breast cancer
versus adjacent control tissues . Data obtained from each individual
sample will be presented . The study is supported by Friends for an
Earlier Breast Cancer Test Foundation, USA.
P04.065
mutation screening of BRCA using Non-Radioactive PcR-sscP
analysis at 17q21 in breast carcinomas from non-familial cases
S. Ghorbanpoor1 , A. Bidmeshkipoor1 , M. H. Mirmomeni1 , S. khazaie2 ;
1 2 Razi university, Kermanshah, Islamic Republic of Iran, Imam Reza Hospital
Molecular pathology, Kermanshah, Islamic Republic of Iran.
BRCA1 is a well-established breast cancer susceptibility gene . Correlation
of breast cancer with BRCA1 mutation was studied in sporadic
breast cancers since this gene is implicated in the double strand DNA
repair and mitotic checkpoint, and loss of its function is speculated to
result in the accumulation of chromosomal instability . In the present
study, breast tumors of sporadic cancer were investigated for allelic
imbalance (AI) at the BRCA1locus . Furthermore, 30 breast carcinomas
from patients with sporadic disease were examined to detect BRCA1mutation(s),
including exons 5, 11A, and 11B by using non-radioactive
polymerase chain reaction-single-strand conformation polymorphism
(PCR-SSCP) technique followed by direct sequencing . Designed primers
were used to amplify three DNA fragments of 235, 300, and 296
bp for detection of these exons mutations, respectively . After the PCR
products were denatured, we have used SSCP technique to detect
BRCA1 mutations . We investigated mutations in 6 cases (20%); 4
cases (13 .3%) in exon 5, no case in exon 11A and 2 cases (6 .7%) in
exon 11B . Clinicopathological patients information was obtained from
their files and pathologic reports. The relationship between these exons
mutations and the clinicopathological variables was analyzed by
the Fisher’s exact test . Our results suggest that exon 5 and exon 11B
gene mutations contribute to the development of sporadic breast cancer
in kermanshah people .
P04.066
investigation of chromosomal radiosensitivity in the peripheral
blood of iranian women with sporadic Breast cancer: A pilot
study
F. Mojtahedi 1,2 , F. Seirati 3 , E. Keihani 1 , M. Karimloo 4 , S. Akhlaghpour 5 , A.
Saremi 2 , I. Bagherizadeh 1 , S. Ghasemi Firouzabadi 1 , M. Fallah 1 , J. Ansari 1 , F.
Behjati 1 ;
1 Genetic Research center, university of social welfare and rehabilitation sciences,
Tehran, Islamic Republic of Iran, 2 Dept. of Medical Genetics, Sarem Women’s
Hospital, Tehran, Islamic Republic of Iran, 3 Department of Surgery, Mehrad
Hospital, Tehran, Islamic Republic of Iran, 4 Department of Statistics, university
of social welfare and rehabilitation sciences, Tehran, Islamic Republic of Iran,
5 Novin Radation therapy Medical Center, Tehran, Islamic Republic of Iran.
Breast cancer is the most frequent malignancy and the main cause
of death amongst women worldwide and in Iran . Links between cancer
predisposition and cellular radiosensitivity are well established
and arose from investigations into chromosomal instability syndromes
such as ataxia-Telangiectasia .
It has been shown that sensitivity to ionizing radiation by induction
of chromosome aberration is, on average, higher in lymphocytes of
breast cancer patients compared to healthy controls . It is therefore important
to show that elevated chromosomal radiosensitivity may be a
marker for breast cancer predisposition . In addition to chromosomal instability
syndromes, approximately 40% of patients with breast cancer,
30% with colorectal cancer and 30% with head and neck cancer appear
to show evidence of cellular radiosensitivity compared to healthy
controls using the chromosomal G2 assay . Approximately 5-14% of
the normal population has been shown to be radiosensitive and the
connection between predisposition to cancer and radiosensitivity has
led to the suggestion that chromosomal radiosensitivity may be used
as an indicator of cancer proneness in the normal population .
In this study, 32 patients with sporadic breast cancer and 30 normal
women as controls were investigated for their Chromosome radiosensitivity
using gama irradiation for the cultured lymphocytes at G2 stage
of the cell cycle. Our results showed significant increase in chromosome
breakage in the patients compared to normal controls . There
was also heterogeneity in chromosome breakage rate within the normal
controls, which may suggest an increased risk for breast cancer in
some normal women with increased chromosome breakage .
P04.067
X inactivation analysis in BRcA1 carriers and in patients with
hereditary breast cancer
E. Beristain, C. Martínez-Bouzas, N. Puente-Unzueta, N. Viguera, M. I. Tejada;
Hospital de Cruces, Barakaldo, Spain.
One of the two X chromosomes in female mammalian cells is inactivated
in early embryonic life . The majority of females have a 50:50 distribution
of the two cell types . A deviation from this distribution (skewed
X inactivation) occur in female carriers of some X linked disorders . Furthermore,
recently it has been reported that early onset breast cancer
(BC) patients and BRCA1 carriers have a significant higher frequency
of skewed X inactivation than controls .
The aim of this work was to compare X inactivation in two groups of BC
women: BRCA1-carriers and BRCA1 negative cases with familial BC .
We have studied 14 women carrying a BRCA1 pathogenic mutation
(median 40 .6 years old); 48 women with non-BRCA1/BRCA2 mutation
(median 46.1 years) and a high familial history of BC (≥ 3 close
relatives with BC) . We also studied a control population of 56 women
without BC and with no history of X-linked pathologies (median 41 .9
years) .
DNA was extracted from peripheral blood and X inactivation pattern
was determined by PCR analysis of a polymorphic CAG repeat in the
first exon of the androgen receptor gene (AR).
One hundred and three women were heterozygous for the CAG repeat
(103/118=96%) . Skewed X inactivation appeared only in 1 woman of
the control population (1/50=2%) and in none of the BC women .
Data presented in this study does not support any association between
BRCA1 or breast cancer in inactive X heterochromatinisation, although
this interpretation could be limited by the sample size .
P04.068
in silico analysis of BRcA1 and BRcA2 sequence variants of
unknown clinical significance: application to variants found in
healthy women in croatia
P. Ozretic, M. Levacic Cvok, V. Musani, M. Cretnik, S. Levanat;
Rudjer Boskovic Institute, Zagreb, Croatia.
BRCA1 and BRCA2 are the major hereditary breast and/or ovarian
cancer predisposing genes and their mutations increase the risk of
developing cancer . At present, almost half of all BRCA1 and BRCA2
sequence variants found are unclassified variants (UVs) so their clinical
significance is unknown or uncertain. That represents problem for
risk assessment in genetic counselling . After revealing BRCA1 and
BRCA2 sequence variants in healthy Croatian females, our aim was to
find fast in silico method for assessing preliminary clinical significance
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