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Purpose: Cis-acting regulatory SNPs resulting in differential allelic expression (DAE) may, in part, explain the underlying phenotypic variation associated with many complex diseases. To investigate whether common variants associated with DAE were involved in breast cancer susceptibility among BRCA1 and BRCA2 mutation carriers, a list of 175 genes was developed based of their involvement in cancer-related pathways., Methods: Using data from a genome-wide map of SNPs associated with allelic expression, we assessed the association of ~320 SNPs located in the vicinity of these genes with breast and ovarian cancer risks in 15,252 BRCA1 and 8211 BRCA2 mutation carriers ascertained from 54 studies participating in the Consortium of Investigators of Modifiers of BRCA1/2., Results: We identified a region on 11q22.3 that is significantly associated with breast cancer risk in BRCA1 mutation carriers (most significant SNP rs228595 p = 7 × 10 -6 ). This association was absent in BRCA2 carriers (p = 0.57). The 11q22.3 region notably encompasses genes such as ACAT1, NPAT, and ATM. Expression quantitative trait loci associations were observed in both normal breast and tumors across this region, namely for ACAT1, ATM, and other genes. In silico analysis revealed some overlap between top risk-associated SNPs and relevant biological features in mammary cell data, which suggests potential functional significance., Conclusion: We identified 11q22.3 as a new modifier locus in BRCA1 carriers. Replication in larger studies using estrogen receptor (ER)-negative or triple-negative (i.e., ER-, progesterone receptor-, and HER2-negative) cases could therefore be helpful to confirm the association of this locus with breast cancer risk., Competing Interests: The authors declare that they have no conflict of interest. Ethical approval Study participants were recruited through the CIMBA Initiative, following the approval of the corresponding protocol by the Institutional Review Board or Ethics Committee at each participating center. Written informed consent was obtained from all study participants.

Background: The rarity of mutations in PALB2, CHEK2 and ATM make it difficult to estimate precisely associated cancer risks. Population-based family studies have provided evidence that at least some of these mutations are associated with breast cancer risk as high as those associated with rare BRCA2 mutations. We aimed to estimate the relative risks associated with specific rare variants in PALB2, CHEK2 and ATM via a multicentre case-control study., Methods: We genotyped 10 rare mutations using the custom iCOGS array: PALB2 c.1592delT, c.2816T>G and c.3113G>A, CHEK2 c.349A>G, c.538C>T, c.715G>A, c.1036C>T, c.1312G>T, and c.1343T>G and ATM c.7271T>G. We assessed associations with breast cancer risk (42 671 cases and 42 164 controls), as well as prostate (22 301 cases and 22 320 controls) and ovarian (14 542 cases and 23 491 controls) cancer risk, for each variant., Results: For European women, strong evidence of association with breast cancer risk was observed for PALB2 c.1592delT OR 3.44 (95% CI 1.39 to 8.52, p=7.1×10 -5 ), PALB2 c.3113G>A OR 4.21 (95% CI 1.84 to 9.60, p=6.9×10 -8 ) and ATM c.7271T>G OR 11.0 (95% CI 1.42 to 85.7, p=0.0012). We also found evidence of association with breast cancer risk for three variants in CHEK2, c.349A>G OR 2.26 (95% CI 1.29 to 3.95), c.1036C>T OR 5.06 (95% CI 1.09 to 23.5) and c.538C>T OR 1.33 (95% CI 1.05 to 1.67) (p≤0.017). Evidence for prostate cancer risk was observed for CHEK2 c.1343T>G OR 3.03 (95% CI 1.53 to 6.03, p=0.0006) for African men and CHEK2 c.1312G>T OR 2.21 (95% CI 1.06 to 4.63, p=0.030) for European men. No evidence of association with ovarian cancer was found for any of these variants., Conclusions: This report adds to accumulating evidence that at least some variants in these genes are associated with an increased risk of breast cancer that is clinically important., Competing Interests: Conflicts of Interest: None declared., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Mosaic truncating mutations in the protein phosphatase, Mg(2+)/Mn(2+)-dependent, 1D (PPM1D) gene have recently been reported with a statistically significantly greater frequency in lymphocyte DNA from ovarian cancer case patients compared with unaffected control patients. Using massively parallel sequencing (MPS) we identified truncating PPM1D mutations in 12 of 3236 epithelial ovarian cancer (EOC) case patients (0.37%) but in only one of 3431 unaffected control patients (0.03%) (P = .001). All statistical tests were two-sided. A combination of Sanger sequencing, pyrosequencing, and MPS data suggested that 12 of the 13 mutations were mosaic. All mutations were identified in post-chemotherapy treatment blood samples from case patients (n = 1827) (average 1234 days post-treatment in carriers) rather than from cases collected pretreatment (less than 14 days after diagnosis, n = 1384) (P = .002). These data suggest that PPM1D variants in EOC cases are primarily somatic mosaic mutations caused by treatment and are not associated with germline predisposition to EOC., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Importance: Limited information about the relationship between specific mutations in BRCA1 or BRCA2 (BRCA1/2) and cancer risk exists., Objective: To identify mutation-specific cancer risks for carriers of BRCA1/2., Design, Setting, and Participants: Observational study of women who were ascertained between 1937 and 2011 (median, 1999) and found to carry disease-associated BRCA1 or BRCA2 mutations. The international sample comprised 19,581 carriers of BRCA1 mutations and 11,900 carriers of BRCA2 mutations from 55 centers in 33 countries on 6 continents. We estimated hazard ratios for breast and ovarian cancer based on mutation type, function, and nucleotide position. We also estimated RHR, the ratio of breast vs ovarian cancer hazard ratios. A value of RHR greater than 1 indicated elevated breast cancer risk; a value of RHR less than 1 indicated elevated ovarian cancer risk., Exposures: Mutations of BRCA1 or BRCA2., Main Outcomes and Measures: Breast and ovarian cancer risks., Results: Among BRCA1 mutation carriers, 9052 women (46%) were diagnosed with breast cancer, 2317 (12%) with ovarian cancer, 1041 (5%) with breast and ovarian cancer, and 7171 (37%) without cancer. Among BRCA2 mutation carriers, 6180 women (52%) were diagnosed with breast cancer, 682 (6%) with ovarian cancer, 272 (2%) with breast and ovarian cancer, and 4766 (40%) without cancer. In BRCA1, we identified 3 breast cancer cluster regions (BCCRs) located at c.179 to c.505 (BCCR1; RHR = 1.46; 95% CI, 1.22-1.74; P = 2 × 10(-6)), c.4328 to c.4945 (BCCR2; RHR = 1.34; 95% CI, 1.01-1.78; P = .04), and c. 5261 to c.5563 (BCCR2', RHR = 1.38; 95% CI, 1.22-1.55; P = 6 × 10(-9)). We also identified an ovarian cancer cluster region (OCCR) from c.1380 to c.4062 (approximately exon 11) with RHR = 0.62 (95% CI, 0.56-0.70; P = 9 × 10(-17)). In BRCA2, we observed multiple BCCRs spanning c.1 to c.596 (BCCR1; RHR = 1.71; 95% CI, 1.06-2.78; P = .03), c.772 to c.1806 (BCCR1'; RHR = 1.63; 95% CI, 1.10-2.40; P = .01), and c.7394 to c.8904 (BCCR2; RHR = 2.31; 95% CI, 1.69-3.16; P = .00002). We also identified 3 OCCRs: the first (OCCR1) spanned c.3249 to c.5681 that was adjacent to c.5946delT (6174delT; RHR = 0.51; 95% CI, 0.44-0.60; P = 6 × 10(-17)). The second OCCR spanned c.6645 to c.7471 (OCCR2; RHR = 0.57; 95% CI, 0.41-0.80; P = .001). Mutations conferring nonsense-mediated decay were associated with differential breast or ovarian cancer risks and an earlier age of breast cancer diagnosis for both BRCA1 and BRCA2 mutation carriers., Conclusions and Relevance: Breast and ovarian cancer risks varied by type and location of BRCA1/2 mutations. With appropriate validation, these data may have implications for risk assessment and cancer prevention decision making for carriers of BRCA1 and BRCA2 mutations.

Background: Penetrance for breast cancer, ovarian cancer, or both in carriers of BRCA1/BRCA2 mutations is disproportionately high. Sex hormone dysregulation and altered end-organ hormone sensitivity might explain this organ-specific penetrance. We sought to identify differences in hormone regulation between carriers of BRCA1/2 and women who are negative for BRCA1/2 mutations., Methods: We assessed endometrial thickness for each menstrual cycle day (as an index of hormone regulation) in 393 scans from 228 women in the UK Familial Ovarian Cancer Screening Study (UK FOCSS) known to carry either mutation and 1573 scans from 754 women known to be negative for the mutations. To quantify differences in endometrial thickness we focused on days 10-14 and days 21-26, and calculated the area under the curve. We then compared serum oestradiol and progesterone titres during these days of the menstrual cycle in the same groups. Follicular and luteal oestradiol and progesterone serum titres were grouped into quartiles and odds ratios were calculated with logistic regression., Findings: Follicular phase endometrial thickness of carriers of the mutations adjusted for age and day of the menstrual cycle was higher (odds ratio [OR] 1·11, 95% CI 1·03-1·20; p=0·0063) and luteal phase endometrial thickness lower (0·90, 0·83-0·98; p=0·027) than for women negative for the mutations. Median luteal phase titres of progesterone were 121% higher (p=0·00037) in carriers than in women negative for the mutations, and for oestradiol were 33% higher (p=0·007)-ie, 59% of carriers had concentrations of serum progesterone that would have been in the top quartile of concentrations in the control group (OR 8·0, 95% CI 2·1-52·57; p=0·008)., Interpretation: Carriers of BRCA1/BRCA2 mutations are exposed to higher titres of oestradiol and progesterone-known risk-factors for breast cancer. Higher titres of oestradiol in carriers are compatible with this hormone having a role in ovarian carcinogenesis in such women. Our findings could not be explained by differential contraceptive pill use., (Copyright © 2013 Widschwendter et al. Open Access article distributed under the terms of CC BY. Published by Elsevier Ltd. All rights reserved.)

Germline mutations in BRCA1 and BRCA2 are associated with increased risks of breast and ovarian cancer. A genome-wide association study (GWAS) identified six alleles associated with risk of ovarian cancer for women in the general population. We evaluated four of these loci as potential modifiers of ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. Four single-nucleotide polymorphisms (SNPs), rs10088218 (at 8q24), rs2665390 (at 3q25), rs717852 (at 2q31), and rs9303542 (at 17q21), were genotyped in 12,599 BRCA1 and 7,132 BRCA2 carriers, including 2,678 ovarian cancer cases. Associations were evaluated within a retrospective cohort approach. All four loci were associated with ovarian cancer risk in BRCA2 carriers; rs10088218 per-allele hazard ratio (HR) = 0.81 (95% CI: 0.67-0.98) P-trend = 0.033, rs2665390 HR = 1.48 (95% CI: 1.21-1.83) P-trend = 1.8 × 10(-4), rs717852 HR = 1.25 (95% CI: 1.10-1.42) P-trend = 6.6 × 10(-4), rs9303542 HR = 1.16 (95% CI: 1.02-1.33) P-trend = 0.026. Two loci were associated with ovarian cancer risk in BRCA1 carriers; rs10088218 per-allele HR = 0.89 (95% CI: 0.81-0.99) P-trend = 0.029, rs2665390 HR = 1.25 (95% CI: 1.10-1.42) P-trend = 6.1 × 10(-4). The HR estimates for the remaining loci were consistent with odds ratio estimates for the general population. The identification of multiple loci modifying ovarian cancer risk may be useful for counseling women with BRCA1 and BRCA2 mutations regarding their risk of ovarian cancer., (© 2012 Wiley Periodicals, Inc.)

Mutations in the BRCA1 gene substantially increase a woman's lifetime risk of breast cancer. However, there is great variation in this increase in risk with several genetic and non-genetic modifiers identified. The BRCA1 protein plays a central role in DNA repair, a mechanism that is particularly instrumental in safeguarding cells against tumorigenesis. We hypothesized that polymorphisms that alter the expression and/or function of BRCA1 carried on the wild-type (non-mutated) copy of the BRCA1 gene would modify the risk of breast cancer in carriers of BRCA1 mutations. A total of 9874 BRCA1 mutation carriers were available in the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) for haplotype analyses of BRCA1. Women carrying the rare allele of single nucleotide polymorphism rs16942 on the wild-type copy of BRCA1 were at decreased risk of breast cancer (hazard ratio 0.86, 95% confidence interval 0.77-0.95, P = 0.003). Promoter in vitro assays of the major BRCA1 haplotypes showed that common polymorphisms in the regulatory region alter its activity and that this effect may be attributed to the differential binding affinity of nuclear proteins. In conclusion, variants on the wild-type copy of BRCA1 modify risk of breast cancer among carriers of BRCA1 mutations, possibly by altering the efficiency of BRCA1 transcription.

Germline BRCA1 mutations predispose to breast cancer. To identify genetic modifiers of this risk, we performed a genome-wide association study in 1,193 individuals with BRCA1 mutations who were diagnosed with invasive breast cancer under age 40 and 1,190 BRCA1 carriers without breast cancer diagnosis over age 35. We took forward 96 SNPs for replication in another 5,986 BRCA1 carriers (2,974 individuals with breast cancer and 3,012 unaffected individuals). Five SNPs on 19p13 were associated with breast cancer risk (P(trend) = 2.3 × 10⁻⁹ to P(trend) = 3.9 × 10⁻⁷), two of which showed independent associations (rs8170, hazard ratio (HR) = 1.26, 95% CI 1.17-1.35; rs2363956 HR = 0.84, 95% CI 0.80-0.89). Genotyping these SNPs in 6,800 population-based breast cancer cases and 6,613 controls identified a similar association with estrogen receptor-negative breast cancer (rs2363956 per-allele odds ratio (OR) = 0.83, 95% CI 0.75-0.92, P(trend) = 0.0003) and an association with estrogen receptor-positive disease in the opposite direction (OR = 1.07, 95% CI 1.01-1.14, P(trend) = 0.016). The five SNPs were also associated with triple-negative breast cancer in a separate study of 2,301 triple-negative cases and 3,949 controls (P(trend) = 1 × 10⁻⁷) to P(trend) = 8 × 10⁻⁵; rs2363956 per-allele OR = 0.80, 95% CI 0.74-0.87, P(trend) = 1.1 × 10⁻⁷

The Ovarian Cancer Association Consortium selected 7 candidate single nucleotide polymorphisms (SNPs), for which there is evidence from previous studies of an association with variation in ovarian cancer or breast cancer risks. The SNPs selected for analysis were F31I (rs2273535) in AURKA, N372H (rs144848) in BRCA2, rs2854344 in intron 17 of RB1, rs2811712 5' flanking CDKN2A, rs523349 in the 3' UTR of SRD5A2, D302H (rs1045485) in CASP8 and L10P (rs1982073) in TGFB1. Fourteen studies genotyped 4,624 invasive epithelial ovarian cancer cases and 8,113 controls of white non-Hispanic origin. A marginally significant association was found for RB1 when all studies were included [ordinal odds ratio (OR) 0.88 (95% confidence interval (CI) 0.79-1.00) p = 0.041 and dominant OR 0.87 (95% CI 0.76-0.98) p = 0.025]; when the studies that originally suggested an association were excluded, the result was suggestive although no longer statistically significant (ordinal OR 0.92, 95% CI 0.79-1.06). This SNP has also been shown to have an association with decreased risk in breast cancer. There was a suggestion of an association for AURKA, when one study that caused significant study heterogeneity was excluded [ordinal OR 1.10 (95% CI 1.01-1.20) p = 0.027; dominant OR 1.12 (95% CI 1.01-1.24) p = 0.03]. The other 5 SNPs in BRCA2, CDKN2A, SRD5A2, CASP8 and TGFB1 showed no association with ovarian cancer risk; given the large sample size, these results can also be considered to be informative. These null results for SNPs identified from relatively large initial studies shows the importance of replicating associations by a consortium approach., ((c) 2008 Wiley-Liss, Inc.)

Purpose: To evaluate the prevalence of BRCA1 and BRCA2 mutations and associations with clinical correlates of disease in a population-based series of ovarian cancer cases from Denmark., Methods: DNA sequencing and multiplex ligation-dependent probe amplification analysis were used to analyze the BRCA1 and BRCA2 genes for coding sequence mutations and large genomic rearrangements in 445 confirmed cases of ovarian cancer. We evaluated associations between mutation status and clinical characteristics, including cancer risks for first-degree relatives and clinicopathologic features of tumors., Results: Deleterious BRCA1 or BRCA2 mutations were identified in 26 cases; thus, mutations in these genes are responsible for at least 5.8% of ovarian cancer cases in this population. Five different mutations were identified in more than one individual, suggesting that they may be founder mutations in Denmark. We identified several differences between mutation carriers and noncarriers: mutation carriers were diagnosed at a significantly early age (median, 49 and 61 years, respectively; P = 0.0001); the frequency of BRCA1 mutation carriers was 23% for women diagnosed <40 years, 15% for 40 to 49 years, 4% for 50 to 59 years, and 2% for > or =60 years (P = 0.00002); ovarian cancer in carriers was diagnosed at a later stage (P = 0.002) and tumors were of poorer grade (P = 0.0001); and first-degree relatives of mutation carriers had greater relative risks of both ovarian cancer [10.6 (95% confidence interval, 4.2-26.6); P < 0.0001] and breast cancer <60 years [8.7 (95% confidence interval, 3.0-25.0); P < 0.0001]., Conclusion: These data may have a significant effect on risk assessment and clinical management of individuals from Denmark who are predisposed to ovarian cancer because they carry a BRCA1 or BRCA2 mutation.

A total of 283 epithelial ovarian cancer families from the United Kingdom (UK) and the United States (US) were screened for coding sequence changes and large genomic alterations (rearrangements and deletions) in the BRCA1 and BRCA2 genes. Deleterious BRCA1 mutations were identified in 104 families (37%) and BRCA2 mutations in 25 families (9%). Of the 104 BRCA1 mutations, 12 were large genomic alterations; thus this type of change represented 12% of all BRCA1 mutations. Six families carried a previously described exon 13 duplication, known to be a UK founder mutation. The remaining six BRCA1 genomic alterations were previously unreported and comprised five deletions and an amplification of exon 15. One of the 25 BRCA2 mutations identified was a large genomic deletion of exons 19-20. The prevalence of BRCA1/2 mutations correlated with the extent of ovarian and breast cancer in families. Of 37 families containing more than two ovarian cancer cases and at least one breast cancer case with diagnosis at less than 60 years of age, 30 (81%) had a BRCA1/2 mutation. The mutation prevalence was appreciably less in families without breast cancer; mutations were found in only 38 out of 141 families (27%) containing two ovarian cancer cases only, and in 37 out of 59 families (63%) containing three or more ovarian cancer cases. These data indicate that BRCA1 and BRCA2 are the major susceptibility genes for ovarian cancer but that other susceptibility genes may exist. Finally, it is likely that these data will be of clinical importance for individuals in families with a history of epithelial ovarian cancer, in providing accurate estimates of their disease risks., ((c) 2007 Wiley-Liss, Inc.)

Objective: To date, most mtDNA mutations in cancer have been identified in the control region (D-loop) containing the major promoters. However, almost all studies used one sample per tumor and there is no clear evidence whether metastatic deposits harbor different mtDNA variants. To establish whether different mtDNA variants can be found in the same cancer but at different sites, we analyzed a series of unilateral and bilateral primary epithelial ovarian cancers as well as paired metastatic tumor deposits., Methods: We sequenced the D-loop region in 52 different tumor samples of 35 ovarian cancer cases, as well as matched normal tissues. Seventeen of those 35 cases had bilateral ovarian cancer, with a sample from each tumor analyzed., Results: Eighty-six polymorphisms (4 new in ovarian cancer) were detected, and 9 different somatic mtDNA mutations were found in 26% (9 of 35) of ovarian cancer cases; all were homoplasmic in nature. Six of the mutations were novel in ovarian cancer. In 24% (4 of 17) of cases with bilateral ovarian tumors, different mtDNA variants were found between paired tumors, suggesting the presence of different clonal populations of cancer cells. Metastatic tumor deposits showed identical mtDNA variants to those found in at least one of the ovarian tumors in cases with bilateral ovarian cancer., Conclusion: Our data demonstrate that multiple tumor samples from the same patient may harbor different mtDNA variants.

Germline mutations in the BRCA1 gene cause inherited susceptibility to breast and ovarian cancers. However, somatic mutations of BRCA1 are rare in sporadic breast and ovarian tumours. To establish whether BRCA1 is altered during the development of sporadic ovarian cancer by mechanisms other than somatic mutation, we have analysed 57 sporadic epithelial ovarian tumours for BRCA1 protein and RNA expression. Reduced or absent protein expression was observed in 90% of tumours. Decreased protein expression was significantly associated with a reduction in the levels of RNA expression. Somatic mutations of BRCA1 and LOH at the BRCA1 locus were detected in 3.5% and 44% of informative tumours, respectively; there was no significant correlation between the levels of protein and RNA expression and the DNA mutation and/or LOH status. Together, these data suggest that expression of BRCA1 is down-regulated at the level of transcription during the development of sporadic ovarian cancers., (Copyright 2000 Wiley-Liss, Inc.)

The EP300 protein is a histone acetyltransferase that regulates transcription via chromatin remodelling and is important in the processes of cell proliferation and differentiation. EP300 acetylation of TP53 in response to DNA damage regulates its DNA-binding and transcription functions. A role for EP300 in cancer has been implied by the fact that it is targeted by viral oncoproteins, it is fused to MLL in Leukaemia and two missense sequence alterations in EP300 were identified in epithelial malignancies. Nevertheless, direct demonstration of the role of EP300 in tumorigenesis by inactivating mutations in human cancers has been lacking. Here we describe EP300 mutations, which predict a truncated protein, in 6(3%) of 193 epithelial cancers analysed. Of these six mutations, two were in primary tumours (a colorectal cancer and a breast cancer) and four were in cancer cell lines (colorectal, breast and pancreatic). In addition, we identified a somatic in-frame insertion in a primary breast cancer and missense alterations in a primary colorectal cancer and two cell lines (breast and pancreatic). Inactivation of the second allele was demonstrated in five of six cases with truncating mutations and in two other cases. Our data show that EP300 is mutated in epithelial cancers and provide the first evidence that it behaves as a classical tumour-suppressor gene.

We screened 81 ovarian tumours (30 BRCA1 associated, 18 BRCA2 associated, and 33 sporadic) for somatic TP53 mutations using both DNA analysis and immunostaining. TP53 mutations were significantly more frequent in tumours with mutations in BRCA1 (70% by immunostaining and 60% by DNA analysis) and BRCA2 (67% and 50%) compared to sporadic controls (39% and 30%) (P = 0.009). A higher proportion of tumours with BRCA1 and BRCA2 mutations were poorly differentiated, and TP53 mutant tumours in all categories were also more likely to be poorly differentiated. The poor differentiation of tumours with BRCA1 and BRCA2 mutations may be directly related to the role of these genes in DNA repair, and the need to overcome cell cycle checkpoints, often through loss of TP53. These results are consistent with the model of BRCA-induced tumorigenesis in which loss of checkpoint control is necessary for tumour development.

Two cancer susceptibility genes, BRCA1 on chromosome 17q12-21 and BRCA2 on chromosome 13q12-13, are thought to be responsible for approximately 80% of families containing multiple cases of early-onset female breast cancer. Germline mutations of BRCA1 are also associated with ovarian cancer and mutations of BRCA2 are associated with an increased risk of male breast cancer, ovarian cancer, prostate cancer and pancreatic cancer. The recent isolation of both genes should make possible the identification of the genetic defect that predisposes affected individuals to breast and ovarian cancer and might lead to the use of genetic information for predictive testing.

A population-based series of 54 male breast cancer cases from Southern California were analyzed for germ-line mutations in the inherited breast/ovarian cancer genes, BRCA1 and BRCA2. Nine (17%) of the patients had a family history of breast and/or ovarian cancer in at least one first-degree relative. A further seven (13%) of the patients reported breast/ovarian cancer in at least one second-degree relative and in no first-degree relatives. No germ-line BRCA1 mutations were found. Two male breast cancer patients (4% of the total) were found to carry novel truncating mutations in the BRCA2 gene. Only one of the two male breast cancer patients carrying a BRCA2 mutation had a family history of cancer, with one case of ovarian cancer in a first-degree relative. The remaining eight cases (89%) of male breast cancer with a family history of breast/ovarian cancer in first-degree relatives remain unaccounted for by mutations in either the BRCA1 gene or the BRCA2 gene.

The breast and ovarian cancer susceptibility gene BRCA2 has recently been isolated. A role for BRCA2 in sporadic breast and ovarian cancer has been suggested by loss of heterozygosity (LOH) studies which show frequent LOH in the BRCA2 region at chromosome 13q12. In addition, the observation of nonrandom loss of the wild-type chromosome in a breast/ovarian cancer family which shows linkage to BRCA2 suggests it may act as a tumor suppressor gene. To determine the extent of somatic alteration involving BRCA2 in sporadic ovarian cancer, 50 tumors were analyzed for mutations throughout the entire BRCA2 coding region. Mutations predicted to result in truncation of the BRCA2 protein were detected in four tumors. Analysis of germline DNA revealed two of these alterations to be of somatic origin. In addition, all four tumors exhibited loss of the second BRCA2 allele as predicted by Knudson's hypothesis for a tumor suppressor gene. These results suggest that, as is the case with BRCA1, somatic mutations of BRCA2 are infrequent in sporadic ovarian cancer, despite the relatively high frequency of LOH detected around the BRCA2 locus.

The characteristic tumours of MEN 2 are medullary thyroid carcinoma (MTC) and phaeochromocytoma. Somatic RET mutations have been found in only 23-40% of sporadic MTC and 10% of sporadic phaeochromocytomas. Thus, we sought other genes which may play a role in the pathogenesis of these tumours. We carried out direct sequence analysis of human c-mos and human ENRB in a series of sporadic MTC and phaeochromocytomas to determine if somatic mutations in these two genes could account for some of the sporadic MEN 2-related tumours in which no RET mutations are detected. No somatic mutations were found.

An atypically high frequency of loss of heterozygosity at chromosome 5q22 in small adenomas from a severely affected new mutation patient with adenomatous polyposis coli was recently reported. DNA homoduplex analysis has now been used to show that the deletion in the adenomas extends to include the APC locus and that the normal allele is lost. These data also prove the maternal origin of the mutation.

Germline mutation in APC at 5q21-22 results in the dominantly inherited syndrome adenomatous polyposis coli (APC). Somatic mutation in this gene is an early event in colorectal tumourigenesis. Both types of mutation are concentrated in the 5' half of exon 15. We have used single strand conformational polymorphism (SSCP) and heteroduplex analysis to screen for variants in this region of the gene in a total of 45 affected but unrelated individuals. Eighteen patients had no family history of the disease; of these 11 were classified as having a severe phenotype, based on an early age at presentation or cancer development. This compared with 6 of 27 familial cases. A 5 bp deletion at codon 1309 reported to occur in 10-15% of unselected APC patients worldwide, was found in 5 of the 18 new mutation cases and 4 of the 27 familial cases: all nine were classed as severe. A further 3 new mutations and 1 familial mutation were located downstream from codon 1309, these individuals similarly being classed as phenotypically severe. In contrast all of the APC mutations detected in affected individuals with an average phenotype were located prior to codon 1309. The frequent association of a severe phenotype with fresh mutation may explain the apparent conflict of a high mutation rate (20-30%) in a condition, which on average, is lethal at a post-reproductive age.