Study On Genetic Susceptibility For Breast Cancer

In the present study, we performed the comprehensive mutation screening of BRCA1 and BRCA2 gene in the population of familial/early onset breast cancer patients to identify the potential "founder mutation" and "characteristic mutation" of Chinese people. Futhermore, based on the hereditary breast cancer population, case-control studies were carried out to explore the association of varients in the estrogen-related genes and CHEK2 gene with the risk of developing breast cancer and to identify the high-risk loci of genetic susceptibility for breast cancer.1. Mutational analysis of BRCA1 and BRCA2 genes in familial and early-on set breast cancer from ShanghaiTo investigate the prevalence of BRCA1 and BRCA2 mutations among familial and early-onset breast cancer patients in Shanghai. Methods Pathologically-confirmed breast cancer patients with positive family history and/or who were diagnosed with breast cancer before age of 35 years were recruited. A total of 72 cases were diagnosed between the years 2002-2004 in the department of breast surgery at Cancer Hospital/Institute, Fudan University, Shanghai, China and comprised of 35 patients having at least one first-degree relative affected with breast cancer and 37 early-onset breast cancer cases (age≤35yrs). Mutation screening of BRCA1 and BRCA2 were performed in the whole coding sequence through denaturing high-performance liquid chromatography (DHPLC) and subsequent DNA direct sequencing. Results Six deleterious mutations, including 2 novel frameshift mutations (3449insA, 5587-ldel8) and 2 novel splice-site mutations (IVS17-1G>T, IVS21+1G>C) in BRCA1 were identified. The identified mutation-5587-ldel8 and 5640delA all located adjacently in exon 24 of BRCA1 gene.Three deleterious mutations detected in BRCA2, including two frameshift mutation (5950delCT, 5802delAATT) and one novel missense mutation(5911G>C), all occurred on exon 11 adjacently. Additional 12 novel sequence variants were also detected, including one unclassified variant and 7 intronic variants in BRCA1, and 4 novel intronic variants in BRCA2, all causing no alteration of amino acid coding. In the total population of study, the prevalence of BRCA1 and BRCA2 mutations were 8.3% and 4.2%, respectively. The prevalence of BRCA1 and BRCA2 mutations in patients with early-onset breast cancer (age<40yrs) was 12% and 4%, respectively. The distribution of BRCA1 mutations in early-onset breast cacer patients with positive familial history (30.8%) was significantly higher than that in pureearly-onset breast cancer patients (5.4%). The frequency of BRCA1 mutations (11.4%) is higher than that of BRCA2 mutations (2.9%) in the setting of familial breast cancer group. No "founder mutation" has been found in the population. Conclusion Four novel mutations in BRCA1 and one novel mutation in BRCA2 may be mutations characterized of familial/early-onset breast cancer in Chinese population. Germline mutations in BRCA2 may contribute less than mutations in BRCA1 to hereditary breast cancer in Shanghai. The early-onset breast cancer patients with positive familiy history are more likely to carry BRCA1 mutations and therefore, genetic screening is needed to perform on their relatives. Our data contribute to information on spectrum of BRCA gene in Chinese population and also offer a recommended screening mode-DHPLC for clinical genetic testing programme in China.2. Role of CHEK2 c.1100delC on genetic susceptibility of hereditary breast cancer from ShanghaiTo investigate the prevalence of CHEK2 c.1100delC mutation among non-BRCAl/BRCA2 familial/early-onset breast cancer patients and Chinese population in Shanghai. Methods One hundred and fourteen hereditary breast cancer patients (BRCA1/BRCA2 mutation carriers excluded) diagnosed between the years 2000-2004 in the department of breast surgery at Cancer Hospital/Institute, Fudan University were analyzed as high-risk population. Among them, 76 patients had at least one first-degree relative affected with breast cancer and 38 patients were diagnosed with breast cancer before the age of 40 years without family history. 121 age-matched cancer-free healthy subjects were recruited as controls. Mutation genotyping of CHEK2 c.1100delC were carried out through long-range PCR of exon10-14, followed by amplification of exon 10 and subsequent DNA direct sequencing. Results No c.1100delC frame-shift mutation was identified in our study population. One novel missense mutation 1111C>T (p.His371Tyr), located in kinase catalytic domain, was found in 3 familial breast cancer cases and no one in control group. Conclusion CHEK2 c.1100delC is rare variant for Chinese population and may not contribute to predisposition for hereditary breast cancer in Shanghai. Novel variant-1111C>T could be in association with genetic susceptibility to hereditary breast cancer. A larger study is needed to confirm the results.3. The association of polymorphisms in estrogen-relating genes with genetic susceptibility of hereditary breast cancer from Shanghai3.1 Role of Vall58Met polymorphism in COMT gene on hereditary breastcancer from shanghaiCOMT play an important role in inactivation of catechol estrogen by methylation. The present study is to explore effect of Vall58Met polymorphism in COMT gene on genetic susceptibility for breast cancer. Methods 114 hereditary breast cancer patients from independent families (BRCA1/BRCA2 mutation carriers excluded) and 121 age-matched cancer-free healthy control subjects were analyzed. Genotype analysis was conducted by polymerase chain reaction (PCR) and then DNA direct sequencing. The odd-ratios (OR) and 95% confidence intervals (CI) was calculated by unconditional logistic regression model. Results A total of 112 cases and 110 controls were PCR amplified and sequenced successfully. The frequency of Vall58Met polymorphism GG, GA and AA genotype in case group and controls was 65 (58.1%), 36 (32.1%), 11 (9.8%) and 66(60.0%), 41 (37.3%), 3 (2.7%), respectively. The frequency of A allele-contained genotypes was statistically significantly higher in early-onset breast cancer patients (56.8%) than in familial ones (36.7%). Compared with GG (Val/Val) genotype, AA (Met/Met) genotype confered a statistically significantly increased risk for breast cancer (adjusted OR=3.15; 95%CI, 0.70-14.19), especially among premenopausal women (adjusted OR=9.98; 95%CI, 1.0-99.64). Borderline significantly association was found between AA genotype (adjusted OR=7.57; 95%CI, 0.57-101.28) and susceptibility for breast cancer in BMI≤23kg/m~2 group. Conclusion Vall58Met polymorphism in COMT gene could be a candidate locus for low penetrance breast cancer susceptibility in Chinese population, especially among premenopausal women and early-onset breast cancer patients, and also recommended as a marker in clinical genetic test. Prevalence of Val/Met or Met/Met genotype in Chinese is different from that in other ethnical population.3.2 Role of polymorphisms in ER-α gene on genetic susceptibility of hereditary breast cancer from shanghaiThe estrogen receptor alpha(ER-α) mediates the effect of estrogen on target tissue and plays an important role in the development and progression of breast cancer. The present study is to explore association of Pvu II and XbaI polymorphism in ER-α gene with genetic susceptibility for breast cancer. Methods 114 hereditary breast cancer patients from independent families (BRCA1/BRCA2 mutation carriers excluded) and 121 age-matched cancer-free healthy control subjects were analyzed. Genotype analysis was conducted by polymerase chain reaction (PCR) and then DNA direct sequencing. The odd-ratios (OR) and 95% confidence intervals (CI) was calculated by unconditionallogistic regression model. Results A total of 113 cases and 113 controls were PCR amplified and sequenced successfully. The frequency of Pvu II polymorphism CC(PP), CT(Pp), TT(pp) genotype in case group was 16 (14.2%), 58 (51.3%), 39 (34.5%), respectively. The distribution of AA (xx), AG (Xx), GG (XX) genotype of XbaI polymorphism were shown as 76(67.2%), 34(30.1%), 3(2.7%) among cases, respectively. The PvuII and XbaI genotype distribution did not shown any significant difference between cases and controls as a whole. But among premenopausal women, CT genotype of PvuII confered a significantly increased risk for breast cancer compared with CC genotype (adjusted OR=2.07; 95%CI, 0.68-6.30); carriers of GG of XbaI had a decreased risk for breast cancer (adjusted OR=0.11; 95%CI, 0.01-1.27) compared with AA genotype. Furthermore, combined analysis of two polymorphisms indicated individuals carrying PvuII CT and XbaI AA genotype were at more increased risk for breast cancer as compared with those with PvuII CC and XbaI GG genotype (OR=11.43, 95%CI, 1.12-116.7) among premenopausal women. Conclusion PvuII and XbaI polymorphisms in ER-α gene could be candidate locu for low penetrance breast cancer susceptibility in Chinese population, especially among premenopausal women and also recommended as markers in clinical genetic test.33 Effect of R264C polymorphism in CYP19A1 gene on genetic susceptibility of hereditary breast cancer from shanghaiAromatase, encoded by CYP19A1, play an important role in estrogens biosynthesis from androgens. The present study is to investigate effect of R264C single-nucleotide polymorphism in CYP19A1 gene on genetic susceptibility for hereditary breast cancer without BRCA1/2 mutant. Methods 114 hereditary breast cancer patients from independent families (BRCA1/BRCA2 mutation carriers excluded) and 121 age-matched cancer-free healthy control subjects were analyzed. Genotype analysis was performed through polymerase chain reaction (PCR) and then DNA direct sequencing. The odd-ratios (ORs) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression model. Results A total of 108 cases and 112 controls were PCR amplified and sequenced successfully. The distribution of CC, CT and TT genotypes of R264C polymorphism in cases and controls were 84 (77.8%), 22 (20.4%), 2 (1.8%) and 87 (77.7%), 24 (21.4%),1 (0.9%), respectively. CT genotype (OR=1.16, 95%CI 0.53-2.55) and TT genotype (OR=1.44, 95%CI 0.12-17.15) did not confer a significantly increased risk for breast cancer. No significant association was found between T allele and susceptibility for breast cancer under stratified analysis accordingto menopausal status and BMI. Conclusion R264C polymorphism in CYP19A1 gene is not a candidate locus for low penetrance breast cancer susceptibility in Shanghai group of Chinese population and not recommended as marker in clinical genetic test. Homozygous T allele of R264C is not common in Shanghai group of Chinese population.SummaryIn the present study, we performed the comprehensive mutation screening of BRCA1 and BRCA2 gene in the population of familial/early onset breast cancer. Futhermore, based on the hereditary breast cancer population that BRCA1/2 gene mutation carriers were excluded, case-control studies were performed to investigate the association of varients in the estrogen-related genes and CHEK2 gene with the risk of breast cancer and to identify the high-risk loci of genetic susceptibility for breast cancer. A further larger study to identify high-penetrance gene mutations and low-penetrance gene polymorphisms associated with breast cancer susceptibility is what we pursued and also in process.