Biomedical subjects

Hilmi Ozcelik

Publications and source records attributed to Hilmi Ozcelik.

At least 19 recordsLinked to original sources

PubMed2007

Type of TP53 mutation and ERBB2 amplification affects survival in node-negative breast cancer.

Alterations of TP53 and ERBB2 have been shown to play important roles in the prognosis of breast cancer. The primary objective of this study is to characterize TP53 mutation types in node negative breast cancer and investigate their prognostic value, alone and in combination with ERBB2 amplification status. TP53 mutational status (exons 2-10) and ERBB2 amplification status were determined in tumor specimens from a prospective cohort of 543 women with node-negative breast cancer. During a median follow-up of 120 months, there were 111 disease recurrences, and 81 disease-related deaths (3 with cancer; 78 from cancer). Of 543 women, 133 (24.5%) carried mutations in exons 4-9 of the TP53 gene. Seventy-one (53.4%) of these mutations were missense; whereas 62 (46.6%) were protein-truncating mutations. Women whose tumors had missense TP53 mutations were found to be at significantly higher risk of recurrence and death compared to those with wild type TP53, and they also tended to have worse prognosis compared to those with truncating mutations. Those with short truncated proteins tended to have good prognosis compared to those with long truncated proteins, but the risk of recurrence and death did not differ between those whose tumors exhibited conserved versus non-conserved mutations. Missense mutations, in combination with ERBB2 amplification, were observed in 4.6% of the tumors and dramatically affected the disease-specific survival (DSS) and disease-free survival (DFS) of the breast cancer patients. Our study suggests that the type of TP53 mutation, especially missense mutation, is a strong prognostic indicator for DFS and DSS in node-negative breast cancer, particularly in combination with ERBB2 amplification.

Breast Neoplasms↗

PubMed2006

Functional nonsynonymous single nucleotide polymorphisms from the TGF-beta protein interaction network.

Protein complexes mediated by protein-protein interactions are essential for many cellular functions. Transforming growth factor (TGF)-beta signaling involves a cascade of protein-protein interactions and malfunctioning of this pathway has been implicated in human diseases. Using an in silico approach, we analyzed the naturally occurring human genetic variations from the proteins involved in the TGF-beta signaling (10 TGF-beta proteins and 242 other proteins interacting with them) to identify the ones that have potential biological consequences. All proteins were searched in the dbSNP database for the presence of nonsynonymous single nucleotide polymorphisms (nsSNPs). A total of 118 validated nsSNPs from 63 proteins were retrieved and analyzed in terms of 1) evolutionary conservation status, 2) being located in a functional protein domain or motif, and 3) altering putative protein motif or phosphorylation sites. Our results indicated the presence of 31 nsSNPs that occurred at evolutionarily conserved residues, 37 nsSNPs were located in protein domains, motifs, or repeats, and 46 nsSNPs were predicted to either create or abolish putative protein motifs or phosphorylation sites. We undertook this study to analyze the human genetic variations that can affect the protein function and the TGF-beta signaling. The nsSNPs reported in here can be characterized by experimental approaches to elucidate their exact biological roles and whether they are related to human disease.

Computational Biology↗

PubMed2006

SNP-SNP interactions in breast cancer susceptibility.

BACKGROUND: Breast cancer predisposition genes identified to date (e.g., BRCA1 and BRCA2) are responsible for less than 5% of all breast cancer cases. Many studies have shown that the cancer risks associated with individual commonly occurring single nucleotide polymorphisms (SNPs) are incremental. However, polygenic models suggest that multiple commonly occurring low to modestly penetrant SNPs of cancer related genes might have a greater effect on a disease when considered in combination. METHODS: In an attempt to identify the breast cancer risk conferred by SNP interactions, we have studied 19 SNPs from genes involved in major cancer related pathways. All SNPs were genotyped by TaqMan 5'nuclease assay. The association between the case-control status and each individual SNP, measured by the odds ratio and its corresponding 95% confidence interval, was estimated using unconditional logistic regression models. At the second stage, two-way interactions were investigated using multivariate logistic models. The robustness of the interactions, which were observed among SNPs with stronger functional evidence, was assessed using a bootstrap approach, and correction for multiple testing based on the false discovery rate (FDR) principle. RESULTS: None of these SNPs contributed to breast cancer risk individually. However, we have demonstrated evidence for gene-gene (SNP-SNP) interaction among these SNPs, which were associated with increased breast cancer risk. Our study suggests cross talk between the SNPs of the DNA repair and immune system (XPD-[Lys751Gln] and IL10-[G(-1082)A]), cell cycle and estrogen metabolism (CCND1-[Pro241Pro] and COMT-[Met108/158Val]), cell cycle and DNA repair (BARD1-[Pro24Ser] and XPD-[Lys751Gln]), and within carcinogen metabolism (GSTP1-[Ile105Val] and COMT-[Met108/158Val]) pathways. CONCLUSION: The importance of these pathways and their communication in breast cancer predisposition has been emphasized previously, but their biological interactions through SNPs have not been described. The strategy used here has the potential to identify complex biological links among breast cancer genes and processes. This will provide novel biological information, which will ultimately improve breast cancer risk management.

Adult↗

PubMed2006

Genetic variation and the mitogen-activated protein kinase (MAPK) signaling pathway.

Non-synonymous single nucleotide polymorphisms (nsSNPs) are known to alter protein function, contributing to disease susceptibility. This report explores the nature of nsSNPs in the gene products of the highly conserved mitogen-activated protein kinase (MAPK) signaling pathways already implicated in cancer development. MAPK signaling pathways regulate cellular processes such as proliferation, differentiation, apoptosis, and survival mediated through interconnected signaling cascades. Using the dbSNP database, we have identified 25 nsSNPs in 17 out of 98 MAPK genes studied. Computational algorithms were used to predict whether the amino acid substitutions were evolutionarily tolerated, or affected putative functional units such as phosphorylation sites, protein motifs and domains. This study predicts that 36% of nsSNPs are likely to have functional consequences, based on evolutionary conservation analysis, and 36% based on phosphorylation prediction analysis. All such nsSNPs represent potentially functional and disease-causing/modifying alleles. More interestingly, the epistatic relationships discussed in this report represent potential synergistic/ antagonistic/additive effects of nsSNP combinations found within the same protein, or within members of the same protein complex and cascades. This strategy can effectively determine which nsSNPs potentially alter protein function, and can be utilized to study the genetic architecture and disease association of other biological protein complexes and networks.

Algorithms↗

PubMed2006

Human SNPs resulting in premature stop codons and protein truncation.

Single nucleotide polymorphisms (SNPs) constitute the most common type of genetic variation in humans. SNPs introducing premature termination codons (PTCs), herein called X-SNPs, can alter the stability and function of transcripts and proteins and thus are considered to be biologically important. Initial studies suggested a strong selection against such variations/mutations. In this study, we undertook a genome-wide systematic screening to identify human X-SNPs using the dbSNP database. Our results demonstrated the presence of 28 X-SNPs from 28 genes with known minor allele frequencies. Eight X-SNPs (28.6 per cent) were predicted to cause transcript degradation by nonsense-mediated mRNA decay. Seventeen X-SNPs (60.7 per cent) resulted in moderate to severe truncation at the C-terminus of the proteins (deletion of >50 per cent of the amino acids). The majority of the X-SNPs (78.6 per cent) represent commonly occurring SNPs, by contrast with the rarely occurring disease-causing PTC mutations. Interestingly, X-SNPs displayed a non-uniform distribution across human populations: eight X-SNPs were reported to be prevalent across three different human populations, whereas six X-SNPs were found exclusively in one or two population(s). In conclusion, we have systematically investigated human SNPs introducing PTCs with respect to their possible biological consequences, distributions across different human populations and evolutionary aspects. We believe that the SNPs reported here are likely to affect gene/protein function, although their biological and evolutionary roles need to be further investigated.

Codon, Terminator↗

PubMed2006

Functional nsSNPs from carcinogenesis-related genes expressed in breast tissue: potential breast cancer risk alleles and their distribution across human populations.

Although highly penetrant alleles of BRCA1 and BRCA2 have been shown to predispose to breast cancer, the majority of breast cancer cases are assumed to result from the presence of low-moderate penetrant alleles and environmental carcinogens. Non-synonymous single nucleotide polymorphisms (nsSNPs) are hypothesised to contribute to disease susceptibility and approximately 30 per cent of them are predicted to have a biological significance. In this study, we have applied a bioinformatics-based strategy to identify breast cancer-related nsSNPs from 981 carcinogenesis-related genes expressed in breast tissue. Our results revealed a total of 367 validated nsSNPs, 109 (29.7 per cent) of which are predicted to affect the protein function (functional nsSNPs), suggesting that these nsSNPs are likely to influence the development and homeostasis of breast tissue and hence contribute to breast cancer susceptibility. Sixty-seven of the functional nsSNPs presented as commonly occurring nsSNPs (minor allele frequencies > or =5 per cent), representing excellent candidates for breast cancer susceptibility. Additionally, a non-uniform distribution of the common functional nsSNPs among different human populations was observed: 15 nsSNPs were reported to be present in all populations analysed, whereas another set of 15 nsSNPs was specific to particular population(s). We propose that the nsSNPs analysed in this study constitute a unique resource of potential genetic factors for breast cancer susceptibility. Furthermore, the variations in functional nsSNP allele frequencies across major population backgrounds may point to the potential variability of the molecular basis of breast cancer predisposition and treatment response among different human populations.

Breast Neoplasms↗

PubMed2006

Are CYP17 genotypes a biomarker for ovarian cancer in patients with cancer history in their family?

BRCA1 and BRCA2 genes are responsible for 5-10% of breast and ovarian cancer cases. However, the vast majority of ovarian and breast cancer cases do not display the hereditary form of the disease. Estrogen-metabolizing genes may also contribute to the predisposition of breast or ovarian cancer. Polymorphic variants of the estrogen-metabolizing gene, CYP17, have been associated with the risk of hormone-related cancers. In this study we investigated the CYP17 polymorphisms in ovarian cancer patients harboring mutations in the BRCA1 and BRCA2 genes, patients displaying familial characteristics but not carrying mutations and patients with sporadic ovarian cancer. Association between the allele frequencies, the CYP17 genotype and tumor characteristics or clinical parameters was evaluated. Our data suggest evidence for an association between ovarian cancer risk and the CYP17 genotype in the subgroup of patients with familial disease in whom no mutations in the BRCA genes are found. Although there were no statistically significant differences in the genotype distribution between the control group and the subgroup of patients with BRCA mutations, the frequency of the CYP17 A2 allele was significantly higher in the subgroup of patients without BRCA mutations. We found a four- to eightfold higher risk in ovarian cancer patients with family history but without BRCA mutations. Our data indicate that the CYP17 A2 allele polymorphism may confer an increased risk and can provide a biomarker for ovarian cancer patients in whom no mutations in the BRCA genes are observed.

Adult↗

PubMed2005

Phosphorylation states of cell cycle and DNA repair proteins can be altered by the nsSNPs.

BACKGROUND: Phosphorylation is a reversible post-translational modification that affects the intrinsic properties of proteins, such as structure and function. Non-synonymous single nucleotide polymorphisms (nsSNPs) result in the substitution of the encoded amino acids and thus are likely to alter the phosphorylation motifs in the proteins. METHODS: In this study, we used the web-based NetPhos tool to predict candidate nsSNPs that either introduce or remove putative phosphorylation sites in proteins that act in DNA repair and cell cycle pathways. RESULTS: Our results demonstrated that a total of 15 nsSNPs (16.9%) were likely to alter the putative phosphorylation patterns of 14 proteins. Three of these SNPs (CDKN1A-S31R, OGG1-S326C, and XRCC3-T241M) have already found to be associated with altered cancer risk. We believe that this set of nsSNPs constitutes an excellent resource for further molecular and genetic analyses. CONCLUSION: The novel systematic approach used in this study will accelerate the understanding of how naturally occurring human SNPs may alter protein function through the modification of phosphorylation mechanisms and contribute to disease susceptibility.

Alleles↗

PubMed2005

Candidate nsSNPs that can affect the functions and interactions of cell cycle proteins.

Nonsynonymous single nucleotide polymorphisms (nsSNPs) alter the encoded amino acid sequence, and are thus likely to affect the function of the proteins, and represent potential disease-modifiers. There is an enormous number of nsSNPs in the human population, and the major challenge lies in distinguishing the functionally significant and potentially disease-related ones from the rest. In this study, we analyzed the genetic variations that can alter the functions and the interactions of a group of cell cycle proteins (n = 60) and the proteins interacting with them (n = 26) using computational tools. As a result, we extracted 249 nsSNPs from 77 cell cycle proteins and their interaction partners from public SNP databases. Only 31 (12.4%) of the nsSNPs were validated. The majority (64.5%) of the validated SNPs were rare (minor allele frequencies < 5%). Evolutionary conservation analysis using the SIFT tool suggested that 16.1% of the validated nsSNPs may disrupt the protein function. In addition, 58% of the validated nsSNPs were located in functional protein domains/motifs, which together with the evolutionary conservation analysis enabled us to infer possible biological consequences of the nsSNPs in our set. Our study strongly suggests the presence of naturally occurring genetic variations in the cell cycle proteins that may affect their interactions and functions with possible roles in complex human diseases, such as cancer.

Alleles↗

PubMed2004

Nonsense-mediated decay microarray analysis identifies mutations of EPHB2 in human prostate cancer.

The identification of tumor-suppressor genes in solid tumors by classical cancer genetics methods is difficult and slow. We combined nonsense-mediated RNA decay microarrays and array-based comparative genomic hybridization for the genome-wide identification of genes with biallelic inactivation involving nonsense mutations and loss of the wild-type allele. This approach enabled us to identify previously unknown mutations in the receptor tyrosine kinase gene EPHB2. The DU 145 prostate cancer cell line, originating from a brain metastasis, carries a truncating mutation of EPHB2 and a deletion of the remaining allele. Additional frameshift, splice site, missense and nonsense mutations are present in clinical prostate cancer samples. Transfection of DU 145 cells, which lack functional EphB2, with wild-type EPHB2 suppresses clonogenic growth. Taken together with studies indicating that EphB2 may have an essential role in cell migration and maintenance of normal tissue architecture, our findings suggest that mutational inactivation of EPHB2 may be important in the progression and metastasis of prostate cancer.

Cell Line, Tumor↗

PubMed2004

The combination of p53 mutation and neu/erbB-2 amplification is associated with poor survival in node-negative breast cancer.

PURPOSE: Increases in neu/erbB-2 have been implicated in breast cancer prognosis, but do not predict all recurrences. On the basis of evidence that p53 mutation is involved in the development of human neoplasia, we examined the prognostic value of p53 alterations in combination with neu/erbB-2 amplification. PATIENTS AND METHODS: A consecutive series of women were observed for recurrence and death (median follow-up of 85 months) and tumors from 543 individuals were analyzed for p53 mutation status and neu/erbB-2 amplification. Exons 4 through 10 of the p53 gene were analyzed by single-stranded conformational polymorphism and mutations were confirmed by DNA sequencing. The association of p53 mutation status and neu/erbB-2 amplification with risk of recurrence and death was examined in survival analyses with traditional and histologic markers as prognostic factors. RESULTS: p53 mutations occurred in 24.5% of the axillary node-negative breast carcinomas. Mutations were more frequent in carcinomas with neu/erbB-2 amplification: 38.9% compared with only 20.9% in those without neu/erbB-2 amplification. We found elevated risks of disease recurrence and overall mortality in patients with both p53 mutation and neu/erbB-2 amplification in their tumor compared with patients with neither or only one of the alterations. This increase persisted with adjustment for other prognostic factors (relative risk, 2.32; P =.002 for recurrence; relative risk, 2.22; P =.004 for death). CONCLUSION: Evaluation of tumors for p53 mutations may be beneficial to identify women at higher risk of disease recurrence and death when the tumor has neu/erbB-2 amplification, but in the absence of neu/erbB-2 amplification, the presence of p53 mutation may not provide additional independent prognostic information.

Adult↗

PubMed2004

Genetic variants of GPX1 and SOD2 and breast cancer risk at the Ontario site of the Breast Cancer Family Registry.

There are several genes that code for enzymes, including various forms of superoxide dismutase and glutathione peroxidase, that protect the cell against oxidative damage that, in turn, can lead to carcinogenesis. There are a few common genetic polymorphisms in these genes that lead to altered proteins. Three that have been identified are SOD2 Val-9Ala, GPX1 Pro198Leu, and the GPX1 GCG repeat (three alleles with four, five, or six repeats). The SOD2 variant has been associated with increased breast cancer risk in two studies. The GPX1 variants have not been studied with respect to breast cancer, but Pro198Leu has been associated with lung cancer. We conducted a case-control study of these three polymorphisms in incident, invasive breast cancer in Caucasian women under 55. There were 399 cases and 372 controls genotyped, of whom 488 were premenopausal, 208 postmenopausal, and 75 of unknown menopausal status. We were unable to replicate the previously observed association with SOD2 Val-9Ala and also found no association between breast cancer and GPX1 Pro198Leu. However, the allele of GPX1 containing four GCG repeats was significantly associated with breast cancer risk in premenopausal women (odds ratio, 1.55; 95% confidence interval, 1.04-2.30 for carriers versus noncarriers). There is a significant trend of increasing risk with increasing number of alleles with four GCG repeats (P = 0.03). This variant has not previously been reported to be associated with breast cancer.

Adult↗

PubMed2004

Polymorphisms XRCC1-R399Q and XRCC3-T241M and the risk of breast cancer at the Ontario site of the Breast Cancer Family Registry.

This study investigates the role of two nonsynonymous single nucleotide polymorphisms in DNA repair genes, X-ray repair cross-complementing group 1 (XRCC1)-R399Q and X-ray repair cross-complementing group 3 (XRCC3)-T241M, in breast cancer. Incident cases of invasive breast cancer in Caucasian women [n = 402, mean age = 45.7 (SD = 6.2) years] and female Caucasian controls [n = 402, mean age = 45.2 (6.5) years] frequency matched on 5-year age intervals were identified from the Ontario Familial Breast Cancer Registry. No evidence for a main effect of the XRCC1-R399Q genotype on breast cancer risk was observed. Estimates of risk for a family history (FH) of breast cancer compared with no FH differed by XRCC1-R399Q genotype (P value for interaction = 0.001). Homozygote XRCC1-399 R/R individuals and FH+ were at a 2.92-fold [95% confidence interval (95% CI) = 1.47-5.79] increased risk of disease compared with FH- individuals; the estimate of risk increased for R/Q heterozygotes with FH+ [odds ratio (OR) = 3.85, 95% CI = 1.94-7.65] but not for Q/Q homozygotes with FH+ (OR = 0.54, 95% CI = 0.20-1.47) compared with homozygous R/R and FH- individuals. A marginal positive association for XRCC3-241 M/M compared with T/T genotype was found (OR = 1.44, 95% CI = 0.94-2.19), but the heterozygous T/M was not associated with an increase in risk (OR = 0.96, 95% CI = 0.71-1.32). There was also some evidence for a combined effect of body mass index and XRCC3-T241M on estimates of risk. Our results suggest that these polymorphisms may influence breast cancer risk by modifying the effect of risk factors such as FH. There is a need for further study into the role of these polymorphisms as effect modifiers.

Adult↗

PubMed2004

Identifying functional genetic variants in DNA repair pathway using protein conservation analysis.

The role of DNA repair in initiation, promotion, and progression of malignancy suggests that variations in DNA repair genes confer altered cancer risk. Accordingly, DNA repair gene variants have been studied extensively in the context of cancer predisposition. Single nucleotide polymorphisms (SNPs) are the most common genetic variations in the human genome. A fraction of SNPs are located within the genes, which are likely to alter the gene expression and function. SNPs that change the encoded amino acid sequence of the proteins (non-synonymous; nsSNPs) are potentially genetic disease determinant variations. However, as not all amino acid substitutions are supposed to lead to a change in protein function, it will be necessary to have a priori prediction and determination of the functional consequences of amino acid substitutions per se, and then together with other genetic and environmental factors to study their possible association with a trait. Here we report the analysis of nsSNPs in 88 DNA repair genes and their functional evaluation based on the conservation of amino acids among the protein family members. Our analysis demonstrated that >30% of variants of DNA repair proteins are highly likely to affect the function of the proteins drastically. In this study, we have shown that three nsSNPs, which were predicted to have functional consequences (XRCC1-R399Q, XRCC3-T241M, XRCC1-R280H), were already found to be associated with cancer risk. The strategy developed and applied in this study has the potential to identify functional protein variants of DNA repair pathway that may be associated with cancer predisposition.

DNA Repair↗

PubMed2002

HER-2/neu status and tumor morphology of invasive breast carcinomas in Ashkenazi women with known BRCA1 mutation status in the Ontario Familial Breast Cancer Registry.

BACKGROUND: The prevalence of BRCA1 germline mutations is greater in the Ashkenazi Jewish population than in the general North American population. The Ontario Familial Breast Cancer Registry collects clinical and family history data in familial breast carcinoma cases, and unselected Ashkenazi breast carcinomas, and acts as a tumor tissue repository. METHODS: Using this resource, we examined the tumor morphology, hormone receptor status, and HER-2/neu protein overexpression in Canadian Ashkenazi breast carcinoma patients whose germline BRCA1 mutation status is known. RESULTS: Thirty-eight tumors from 32 BRCA1 carriers and 354 tumors from 334 noncarriers were analyzed. The tumors in BRCA1 mutation carriers were more likely to be high grade (P < 0.0001) and estrogen receptor negative (P < 0.004). There was an increased frequency of typical medullary carcinomas in mutation carriers when all tumors were analyzed. However, this difference did not remain statistically significant when only the first tumor diagnosed in each patient was included in the analysis. There was no difference in HER-2/neu protein overexpression between the two groups overall (P = 0.07). However, when the analysis was restricted to Grade III tumors, there were significantly fewer HER-2/neu-positive tumors in the mutation carriers versus noncarriers (3.1% vs. 21.5%, P = 0.012). No significant differences were found in the incidence of lymph node status, progesterone receptor status, lymphatic vessel invasion, degree of lymphocytic infiltration, or in the presence of ductal carcinoma in situ associated with the invasive tumors. CONCLUSIONS: Increasing awareness of the morphologic and immunophenotypic features more commonly found in BRCA1-associated breast carcinomas may lead to a wider use of these characteristics in genetic screening programs and provide further clues to their pathogenesis.

Adult↗

PubMed2002

BRCA1 and BRCA2 mutations in Turkish familial and non-familial ovarian cancer patients: a high incidence of mutations in non-familial cases.

Ovarian cancer is a clinically important cancer in Turkey. The contribution of BRCA1 and BRCA2 to ovarian cancer in Turkish patients has not previously been described. In this study we investigated the presence of BRCA1 and BRCA2 mutations in 102 consecutively ascertained, hospital-based, ovarian cancer cases. Four out of 15 (26.7%, 95% confidence interval (CI), 7.8%-55.1%) familial cases were found to carry mutations in BRCA1. Thirteen of the 87 (14.9%, 95% CI, 7.5%-22.4%) non-familial cases had BRCA1 and BRCA2 mutations, six in BRCA1, and seven in BRCA2. We have further studied the non-familial ovarian cancer cases to determine which subgroups have a likelihood of carrying clinically important mutations. Our study shows that those Turkish ovarian cancer patients with serous histopathology harbor a high proportion of mutations (12/58, 20.7%, 95% CI, 10.3%-31.1%) compared to all non-familial cases (14.9%) regardless of pathology. Within the serous sub-group, those that were also diagnosed below age 50 have an even greater percentage of mutations (8/28, 28.6%, 95% CI, 11.8%-45.3%). Our findings demonstrate that a substantial proportion of Turkish ovarian cancer patients, both with and without a family history, carry BRCA1 and BRCA2 mutations, demonstrating the importance of BRCA1 and BRCA2 in the development of ovarian cancer in this population.

Adult↗

PubMed2002

Comparison of DNA- and RNA-based methods for detection of truncating BRCA1 mutations.

A number of methods are used for mutational analysis of BRCA1, a large multi-exon gene. A comparison was made of five methods to detect mutations generating premature stop codons that are predicted to result in synthesis of a truncated protein in BRCA1. These included four DNA-based methods: two-dimensional gene scanning (TDGS), denaturing high performance liquid chromatography (DHPLC), enzymatic mutation detection (EMD), and single strand conformation polymorphism analysis (SSCP) and an RNA/DNA-based protein truncation test (PTT) with and without complementary 5' sequencing. DNA and RNA samples isolated from 21 coded lymphoblastoid cell line samples were tested. These specimens had previously been analyzed by direct automated DNA sequencing, considered to be the optimum method for mutation detection. The set of 21 cell lines included 14 samples with 13 unique frameshift or nonsense mutations, three samples with two unique splice site mutations, and four samples without deleterious mutations. The present study focused on the detection of protein-truncating mutations, those that have been reported most often to be disease-causing alterations that segregate with cancer in families. PTT with complementary 5' sequencing correctly identified all 15 deleterious mutations. Not surprisingly, the DNA-based techniques did not detect a deletion of exon 22. EMD and DHPLC identified all of the mutations with the exception of the exon 22 deletion. Two mutations were initially missed by TDGS, but could be detected after slight changes in the test design, and five truncating mutations were missed by SSCP. It will continue to be important to use complementary methods for mutational analysis.

BRCA1 Protein↗

PubMed2002

Recurrent BRCA1 and BRCA2 germline mutations in ovarian cancer: a founder mutation of BRCA1 identified in the Chinese population.

Previous mutational analysis for BRCA gene mutations in sporadic ovarian cancer occurring in Chinese patients in Hong Kong identified six germline BRCA1 mutations and one germline BRCA2 mutation, six of which were novel (Khoo et al., 2000). Knowledge of BRCA gene mutations in the Chinese population is relatively scant. In this study, we focussed on whether any of these mutations could be recurrent in our Chinese population, making use of archival paraffin embedded tissue. A consecutive series of 214 ovarian cancer cases, half of Southern Chinese origin from Hong Kong whilst the other half of Northern Chinese origin from Beijing were used for the study. We identified one further novel mutation, 1081delG, in BRCA1. This was found to occur in two unrelated individuals with shared haplotype as revealed by allelotype analysis, thus demonstrating founder effect. Two other recurrent mutations were also identified, the 2371-2372delTG mutation in BRCA1 and the 3337C>T mutation in BRCA2 recurring in two and three unrelated individuals respectively, giving an overall prevalence 4.7% of recurrent BRCA mutations in ovarian cancer in the Southern Chinese population. Most importantly, all our recurrent mutation carriers were identified from Southern Chinese patients from Hong Kong whilst such mutations were absent in samples from the Northern Chinese. Our findings indicate possible heterogeneity in the BRCA genotype between Northern and Southern Chinese. The identification of a founder mutation and two recurrent mutations moreover, has important implications towards screening strategies for breast and ovarian cancer among Chinese of southern ancestral origin who are now dispersed throughout the world.

Adult↗