BRCA1 and BRCA2 mutation frequency in women evaluated in a breast cancer risk evaluation clinic

MICA-129 Met/Val polymorphism could be a genetic biomarker for Familial Breast Cancer in the Tunisian population

Identification of candidate genes associated with susceptibility of breast cancer can have a significant impact at a cancer management national healthcare systems level, making genetic testing more affordable and cost-effective. We have previously shown that the major histocompatibility complex class I-related chain A (MICA) was related to breast cancer and plays an important role in modulating immune response mechanisms through NKG2D receptor activation. Compared to our previous study, in this work, we recruited a new cohort composed of 354 unrelated Tunisian women affected by breast cancer and 380 age-matched women as controls, all genotyped for MICA-129 Met/Val (rs 1051792). Subsequently, we exanimated the distribution of this polymorphism in ten families. As a result, an association was found between the Val allele and Val/Val genotype and the risk of breast cancer (p = 2.5 × 10^-15 ; OR = 2.40; p = 6.5 × 10^-13 ; OR = 3.03, respectively). Stratified analysis with age and family history of cancer revealed an association between the Val/Val genotype and younger patients <40 years (p = .003; OR = 2.03). Among those patients having a family history of cancer, 68% had a Val/Val genotype (p = .02; OR = 1.82). In the family study, an analyse of pedigrees revealed that the majority of families showed the development of breast cancer at a young age. Moreover, all patients diagnosed with early-onset breast cancer had a Val/Val genotype. Our results lead us to propose that this polymorphism may be an inherited genetic biomarker contributing to an increased breast cancer risk in Tunisian women.

Identification of germline pathogenic variants in DNA damage repair genes by a next-generation sequencing multigene panel in BRCAX patients

BACKGROUND

Approximately 5-10% of breast carcinomas have been related to hereditary conditions and are attributable to pathogenic variants in the BRCA1 and BRCA2 genes, which is referred to as hereditary breast and ovarian cancer (HBOC) syndrome. The inclusion of additional genes that can be related to HBOC syndrome is under intense evaluation due to the high proportion of patients with HBOC criteria who do not present pathogenic mutations in BRCA genes, named BRCAX, despite having high clinical suspicion of hereditary cancer. The main aim is to identify new potentially pathogenic gene variants that may contribute to HBOC to improve the efficiency of routine diagnostic tests in this hereditary condition.

METHODS

A retrospective cohort of 77 HBOC BRCAX patients was analyzed by next-generation sequencing using a targeted multigene panel composed of 25 genes related to hereditary cancer and deficiencies in DNA repair pathways.

RESULTS

We found 9 variants in 7 different genes, which were confirmed by automated sequencing. Six variants were classified as pathogenic or likely pathogenic. Three of them were located in the PALB2 gene, one in the BRIP1 gene, one in the BARD1 gene and 1 in the RAD50 gene. In addition, three variants of uncertain significance (VUS) were detected in the TP53, CHEK2, and CDH1 genes.

CONCLUSIONS

We identified that 8% of BRCAX patients were carriers of pathogenic variants in genes other than BRCA1 and BRCA2. Therefore, wide gene panels, including clinically actionable genes, should be routinely used in the screening of HBOC in our population. We observed differences from other studies in the prevalence of mutated genes, most likely due to differences in the selection criteria of the probands and in the population analyzed. The high incidence of deleterious variant detection in PALB2 supports its significant role in breast cancer susceptibility and reinforces its inclusion in the HBOC genetic diagnostic process.

High-frequency actionable pathogenic exome variants in an average-risk cohort

Exome sequencing is increasingly utilized in both clinical and nonclinical settings, but little is known about its utility in healthy individuals. Most previous studies on this topic have examined a small subset of genes known to be implicated in human disease and/or have used automated pipelines to assess pathogenicity of known variants. To determine the frequency of both medically actionable and nonactionable but medically relevant exome findings in the general population we assessed the exomes of 70 participants who have been extensively characterized over the past several years as part of a longitudinal integrated multiomics profiling study. We analyzed exomes by identifying rare likely pathogenic and pathogenic variants in genes associated with Mendelian disease in the Online Mendelian Inheritance in Man (OMIM) database. We then used American College of Medical Genetics (ACMG) guidelines for the classification of rare sequence variants. Additionally, we assessed pharmacogenetic variants. Twelve out of 70 (17%) participants had medically actionable findings in Mendelian disease genes. Five had phenotypes or family histories associated with their genetic variants. The frequency of actionable variants is higher than that reported in most previous studies and suggests added benefit from utilizing expanded gene lists and manual curation to assess actionable findings. A total of 63 participants (90%) had additional nonactionable findings, including 60 who were found to be carriers for recessive diseases and 21 who have increased Alzheimer's disease risk because of heterozygous or homozygous APOE e4 alleles (18 participants had both). Our results suggest that exome sequencing may have considerably more utility for health management in the general population than previously thought.

Revisiting breast cancer patients who previously tested negative for BRCA mutations using a 12-gene panel

PURPOSE

BRCA mutations contribute to about 20% of all hereditary breast cancers. With full-genome sequencing as the emerging standard for genetic testing, other breast cancer susceptibility genes have been identified and may collectively contribute to up to 30% of all hereditary breast cancers. We re-assessed women who had previously tested negative for a BRCA mutation when outdated techniques were used, and discuss the implications of identifying a mutation several years after initial genetic testing.

METHODS

We evaluated the prevalence of mutations in 12 breast cancer susceptibility genes (including BRCA1 and BRCA2) in 190 breast cancer patients with a strong family history of breast cancer. These women had previously tested negative for mutations in the large coding exons of BRCA1 and BRCA2 using the protein truncation test (PTT) between the years of 1996 and 2013.

RESULTS

We identified pathogenic mutations in 17 of 190 (9%) women. Six mutations were detected in BRCA1 (n = 2) and BRCA2 (n = 4). Eleven mutations were found in other breast cancer susceptibility genes including CHEK2 (n = 5), PALB2 (n = 2), BLM (n = 2), ATM (n = 1) and TP53 (n = 1).

CONCLUSION

Among 190 breast cancer patients with a family history of the disease, and who previously received a negative result for BRCA mutations using the PTT, 17 (9%) women were found to carry a high-risk pathogenic mutation in a breast cancer susceptibility gene. Six of these women were BRCA mutation carriers who were missed previously. These findings support the rationale for updated genetic testing in patients who tested BRCA mutation negative using outdated techniques.

Implications of multigene testing for hereditary breast cancer in primary care

Approximately 1 in 8 women will develop breast cancer during their lifetime and the risk factors include age, family history, and reproductive factors. In women with a family history of breast cancer, there is a proportion in which a gene mutation can be the cause of the predisposition for breast cancer. A careful assessment of family and clinical history should be performed in these women in order to determine if a genetic counseling referral is indicated. In cases of hereditary breast cancer, genetic testing with a multigene panel can identify specific genetic mutations in over 100 genes. The most common genes mutated in hereditary breast cancer are the high-penetrance BRCA1 and BRCA2 genes. In addition, other mutations in high-penetrance genes in familial cancer syndromes and mutations in DNA repair genes can cause hereditary breast cancer. Mutations in low-penetrance genes and variants of uncertain significance may play a role in breast cancer development, but the magnitude and scope of risk in these cases remain unclear, thus the clinical utility of testing for these mutations is uncertain. In women with high-penetrance genetic mutations or lifetime risk of breast cancer > 20%, risk-reducing interventions, such as intensive screening, surgery, and chemoprevention, can decrease the incidence and mortality of breast cancer.

The CpG island methylator phenotype in breast cancer is associated with the lobular subtype

BACKGROUND

Aberrations in DNA methylation patterns are well-described in human malignancies. However, the existence of the 'CpG island methylator phenotype' (CIMP) in human breast cancer is still controversial.

MATERIALS & METHODS

Illumina's HumanMethylation 450K BeadChip was used to analyze genome-wide DNA methylation patterns. Chromosomal abnormalities were determined by array-based CGH.

RESULTS

Invasive lobular breast carcinomas exhibit the highest number of differentially methylated CpG sites and a strong inverse correlation of aberrant DNA hypermethylation and copy number alterations. Nine differentially methylated regions within seven genes discriminating the investigated subgroups were identified and validated in an independent validation cohort and correlated to a better relapse-free survival.

CONCLUSION

These results depict a clear difference between genetically and epigenetically unstable breast carcinomas indicating different ways of tumor progression and/or initiation, which strongly supports the association of CIMP with the lobular subtype and provide new options for detection and therapy.

Prospective study of high-risk, BRCA1/2-mutation negative women: the 'negative study'

Background

We previously reported that women from high-risk families who tested negative for a BRCA1 or BRCA2 (BRCA1/2) mutation were four times more likely to develop breast cancer compared to women in the general population. Preventive measures and risk factors for breast cancer development in these high-risk women have not been evaluated to the same extent as BRCA1/2 positive women. Further, there is virtually no scientific evidence about best practices in their management and care. The proposed study will examine a role of genetic and non-genetic factors and develop the systems and parameters for the monitoring and surveillance necessary to help establish guidelines for the care of this high-risk population.

Methods/Design

To achieve our goals, we will assemble and follow a Canadian cohort of 1,000 cancer-free women with a strong family history breast cancer (defined as two or more relatives affected by breast cancer under the age of 50, or three or more relatives diagnosed with breast cancer at any age from one side of the family and with no BRCA1/2 mutation in the family). All eligible participants will be mailed a study package including invitation to participate, consent form, a research questionnaire to collect data regarding family history, reproductive and lifestyle factors, as well as screening and surgery. Usual dietary intake will be assessed by a diet history questionnaire. Biological samples including toenail clippings, urine and blood samples will be collected. These women will be followed every two years by questionnaire to update exposure information, screening practices, surgical and chemoprevention, and disease development.

Discussion

Findings from this study will serve to help establish clinical guidelines for the implementation of prevention, counseling, and treatment practices for women who face an elevated risk of breast cancer due to family history, but who do not carry a BRCA1/2 mutation.

CHEK2 1100delC variant and breast cancer risk in Caucasians: a meta-analysis based on 25 studies with 29,154 cases and 37,064 controls

Links between the CHEK2 1100delC heterozygote and breast cancer risk have been extensively explored. However, both positive and negative associations with this variant have been reported in individual studies. For a detailed assessment of the CHEK2 1100delC heterozygote and breast cancer risk, relevant studies published as recently as May 2012 were identified using PUBMED and EMBASE and selected using a priori defined criteria. The strength of the relationship between the CHEK2 1100delC variant and breast cancer risks was assessed by odds ratios (ORs) under the fixed effects model. A total of 29,154 cases and 37,064 controls from 25 case-control studies were identified in this meta-analysis. The CHEK2 1100delC heterozygote was more frequently detected in cases than in controls (1.34% versus 0.44%). A significant association was found between CHEK2 1100delC heterozygote and breast cancer risk (OR=2.75, 95% CI: [2.25, 3.36]). The ORs and CIs were 2.33 (95% CI: [1.79, 3.05]), 3.72 (95% CI: [2.61, 5.31]) and 2.78 (95% CI: [2.28, 3.39]) respectively in unselected, family, early-onset breast cancer subgroups. The CHEK2 1100delC variant could be a potential factor for increased breast cancer risk in Caucasians. However, more consideration is needed in order to apply it to allele screening or other clinical work.

BRCA1/BRCA2 gene mutations/SNPs and BRCA1 haplotypes in early-onset breast cancer patients of Indian ethnicity

We examined BRCA1/2 mutations and single nucleotide polymorphisms (SNPs) for identification of BRCA1 haplotypes, in early-onset breast cancer patients and their relatives, sporadic breast cancer patients, and unrelated normal healthy females, of Indian ethnicity. Peripheral blood DNA was amplified by polymerase chain reaction, at BRCA1/2 coding exons and subject to nucleotide sequencing using ABI 3100 Genetic Analyzer. We observed BRCA1/BRCA2 mutations in 52 % early-onset breast cancer patients and in 57 % relatives. Deleterious mutations detected in early-onset patients and relatives were 187delAG, 632insT, 1052delT, Q759X, Q780X, R1203X, 5154delC, IVS14 + 1G > A, IVS17 + 1G > T, and 632insT in BRCA1 gene; and 4075delGT, 5076delAA, 6079delAGTT, and W3127X in BRCA2 gene. A high degree of penetrance of BRCA1/2 gene mutations was observed in the relatives. BRCA1/2 SNPs were identified in the Indian population, and association of BRCA1 haplotypes with breast cancer was investigated. A significantly increased frequency of the SNPs 203G/A, 3624A/G and 7470A/G SNPs in BRCA2 gene was observed in normal controls indicative of a protective effect of the SNPs. BRCA1 haplotype 2 was most frequently observed in our population. Our study indicates a high incidence of BRCA1/BRCA2 gene mutations in the Indian patients. The BRCA1/2 mutations and SNPs are detailed on our website http://relibrca.rellife.com .

Selecting for BRCA1 testing using a combination of homogeneous selection criteria and immunohistochemical characteristics of breast cancers

Background

BRCA1 gene-related tumours are more frequently estrogen receptor (ER) and progesterone receptor (PR) negative with a lower prevalence of human epidermal growth factor receptor 2 (HER2) overexpression or amplification. We evaluated the effectiveness of a combination of homogeneously selected criteria and immunohistochemical (IHC) characteristics of Familial Breast Cancers (FBCs) in detecting BRCA1 mutation carriers.

Methods

Primary breast tumours from 93 FBC patients defined by specific eligibility criteria, based on personal and familial tumour history, were evaluated by Allred's method. The BRCA1 molecular analysis, including Multiplex Ligation-dependent Probe Amplification (MLPA), was considered as the gold standard assay.

Results

A total of 10 BRCA1 pathogenetic mutations was found. With the exclusion of the tumours characterized by double positive receptorial status and/or strong HER2 positivity (3+), we identified 22 patients, 10 of whom resulted as BRCA1 mutation carriers. The sensitivity, specificity, positive and negative predictive values were 100%, 83.3%, 45.4% and 100% respectively.

Conclusion

Our findings suggest that the IHC analysis by Allred's method improves our ability to select patients for BRCA1 testing.

Is Chlamydia-infected tubal fimbria the origin of ovarian cancer?

Ovarian cancer is a highly lethal disease and its underlying biology is poorly understood. Prophylactic salpingo-oophorectomies in BRCA + women have recently implicated the fimbria as a site of origin for high-grade serous carcinoma and its intraepithelial precursors. This suggests that at least some ovarian cancers, probably the most aggressive ones, may not originate in the ovary itself, but rather may arise in the uterine tubes. Chronic inflammation is associated with carcinogenesis in several tissues, including liver, esophagogastric junction (cardia), and the uterine cervix. The mechanisms underlying the relationship between inflammation and cancer are complex and involve common pathways, in addition to DNA damage. A critical source of uterine tube inflammation is infection with Chlamydia trachomatis. We hypothesize that C.trachomatis infection may be involved in chronic tubal inflammation and subsequent fimbrial carcinogenesis. Fimbrial intraepithelial precursors can evolve into high grade serous carcinomas that spread rapidly to the ovarian surface and peritoneum; such tumors may appear to be primary ovarian neoplasia, though in reality being a secondary malignancy. This hypothesis must be further investigated to understand the intracellular signaling pathways involved in Chlamydia infection and its healing, and their relationship to carcinogenesis in order to discover potential therapeutic molecular targets. If our hypothesis were confirmed, salpingectomy instead of ovariectomy may also become the recommended surgery for high risk women.

Genetic susceptibility for breast cancer: How many more genes to be found?

Today, breast cancer is the most commonly occurring cancer among women. It accounts for 22% of all female cancers and the estimated annual incidence of breast cancer worldwide is about one million cases. Many risk factors have been identified but a positive family history remains among the most important ones established for breast cancer, with first-degree relatives of patients having an approximately two-fold elevated risk. It is currently estimated that approximately 20-25% of this risk is explained by known breast cancer susceptibility genes, mostly those conferring high risks, such as BRCA1 and BRCA2. However, these genes explain less than 5% of the total breast cancer incidence, even though several studies have suggested that the proportion of breast cancer that can be attributed to a genetic factor may be as high as 30%. It is thus likely that there are still breast cancer susceptibility genes to be found. It is presently not known how many such genes there still are, nor how many will fall into the class of rare high-risk (e.g. BRCAx) or of common low-risk susceptibility genes, nor if and how these factors interact with each other to cause susceptibility (a polygenic model). In this review we will address this question and discuss the different undertaken approaches used in identifying new breast cancer susceptibility genes, such as (genome-wide) linkage analysis, CGH, LOH, association studies and global gene expression analysis.

Large genomic rearrangement in BRCA1 and BRCA2 and clinical characteristics of men with breast cancer in the United States

PURPOSE

Male breast cancer has been linked extensively to mutations of BRCA2 and, to a lesser extent, BRCA1. The aim of this study was to perform a comprehensive analysis of point mutations and genomic rearrangements in the BRCA1 and BRCA2 genes in 41 men with breast cancer.

PATIENTS AND METHODS

Deleterious point mutations were identified in 15 men (37%): 4 (10%) and 11 (27%) in BRCA1 and BRCA2, respectively. In the remaining 26 men, we screened for large genomic rearrangements in BRCA1 and BRCA2 using multiplex ligation-dependent probe amplification.

RESULTS

We did not detect any large genomic rearrangements. Men with BRCA1 or BRCA2 mutations were more likely to have a family history of prostate cancer (P = 0.025). Three of 4 male breast tumors with BRCA1 mutations (75%) were estrogen receptor positive. Whereas some studies have reported an 8%-0 rate of large BRCA2 genomic rearrangement in familial male breast cancer cases, we did not detect any such genomic rearrangements in BRCA1 or BRCA2 for our cohort.

CONCLUSION

Despite this negative finding, our study, to the best of our knowledge, is one of the first to comprehensively screen for mutations, including large genomic rearrangement mutations, in BRCA1 and BRCA2 in men with breast cancer in the United States.

Phenotypic features and genetic characterization of male breast cancer families: identification of two recurrent BRCA2 mutations in north-east of Italy

BACKGROUND

Breast cancer in men is an infrequent occurrence, accounting for approximately 1% of all breast tumors with an incidence of about 1:100,000. The relative rarity of male breast cancer (MBC) limits our understanding of the epidemiologic, genetic and clinical features of this tumor.

METHODS

From 1997 to 2003, 10 MBC patients were referred to our Institute for genetic counselling and BRCA1/2 testing. Here we report on the genetic and phenotypic characterization of 10 families with MBC from the North East of Italy. In particular, we wished to assess the occurrence of specific cancer types in relatives of MBC probands in families with and without BRCA2 predisposing mutations. Moreover, families with recurrent BRCA2 mutations were also characterized by haplotype analysis using 5 BRCA2-linked dinucleotide repeat markers and 8 intragenic BRCA2 polymorphisms.

RESULTS

Two pathogenic mutations in the BRCA2 gene were observed: the 9106C>T (Q2960X) and the IVS16-2A>G (splicing) mutations, each in 2 cases. A BRCA1 mutation of uncertain significance 4590C>G (P1491A) was also observed. In families with BRCA2 mutations, female breast cancer was more frequent in the first and second-degree relatives compared to the families with wild type BRCA1/2 (31.9% vs. 8.0% p = 0.001). Reconstruction of the chromosome phasing in three families and the analysis of three isolated cases with the IVS16-2A>G BRCA2 mutation identified the same haplotype associated with MBC, supporting the possibility that this founder mutation previously detected in Slovenian families is also present in the North East of our Country. Moreover, analysis of one family with the 9106C>T BRCA2 mutation allowed the identification of common haplotypes for both microsatellite and intragenic polymorphisms segregating with the mutation. Three isolated cases with the same mutation shared the same intragenic polymorphisms and three 5' microsatellite markers, but showed a different haplotype for 3' markers, which were common to all three cases.

CONCLUSION

The 9106C>T and the IVS16-2A>G mutations constitute recurrent BRCA2 mutations in MBC cases from the North-East of Italy and may be associated with a founder effect. Knowledge of these two recurrent BRCA2 mutations predisposing to MBC may facilitate the analyses aimed at the identification of mutation carriers in our geographic area.

Histopathology of BRCA1- and BRCA2-associated breast cancer

Hereditary breast carcinomas that are attributable to BRCA1/2 mutations have their own morphological and immunohistochemical characteristics. BRCA1-associated carcinomas are poorly differentiated infiltrating ductal carcinomas that frequently show morphological features of typical or atypical medullary carcinoma. BRCA2-associated breast carcinomas tend to be of higher grade than sporadic age-matched controls. BRCA1tumors have been found to be more frequently estrogen receptor- and progesterone receptor-negative, and p53-positive than are age-matched controls, whereas these differences are not usually found in BRCA2-associated tumors. In addition, BRCA1- and BRCA2-associated breast carcinomas show a low frequency of HER2 expression. Most BRCA1 breast carcinomas are characterized by the expression of basal (myoepithelial) markers, such as cytokeratin 5/6 and or P-cadherin. These features could be used to distinguish patients who are likely to carry a BRCA1 or BRCA2 germline mutation, thus indicating which gene should be screened for first in families with a high incidence of breast and ovarian cancer.

Hormone replacement therapy is more prevalent among Jewish BRCA1/2 mutation carriers

The aim of this study was to compare reproductive factors, use of oral contraceptives (OC) and hormone replacement therapy (HRT) in consecutive Jewish Ashkenazi breast cancer patients, with and without BRCA1/BRCA2 mutations. Jewish Israeli women with breast cancer (n=385) were genotyped for the three predominant Jewish mutations in BRCA1 and BRCA2, and data on reproductive factors, OC and HRT use, were analyzed using logistic regression analyses. Overall, 28/385 (7.3%) of participants were mutation carriers, the majority of whom were Ashkenazi (n=22; 78.6%) and were diagnosed with breast cancer at or under age 49 years (n=18; 64.3%). Mutation carriers were more likely than non-carriers to ever use OC (39.3% vs. 20.2%; P=0.053), HRT (35.7% vs. 13.7%; P=0.007), and have first menarche at or below 12 years of age (71.4% vs. 40.6%; P=0.03). Multivariate analysis showed that Ashkenazi women diagnosed with breast cancer under 40 years of age, with a family history of breast/ovarian cancer, who ever used HRT were more likely to be mutation carriers. This study has shown that HRT use is more prevalent among Jewish Ashkenazi mutation carriers, but its role in modifying breast cancer risk in mutation carriers remains unknown.

BRCA1–2 mutations in breast cancer: Identification of nine new variants of BRCA1–2 genes in a population from central Western Spain

We carried out a mutational analysis of BRCA1 and BRCA2 genes in 103 individuals from a population in Western Central Spain and we identified nine new variants: two truncating mutations in BRCA2 [2604C>A (Y792X), 8873del4], three missense mutations in BRCA2 [677A>G (H150R), 958G>A (D224N) and 3398A>G (K1057R], and four silent mutations, two in BRCA1 [1115T>G (R332R) and IVS24+36 C>G], and two in BRCA2 [2583T>A (I785I) and 7854G>A (T2542T)]. In two unrelated families of our population, we identified the BRCA1 1806C>T (Q563X) mutation, which is considered to be a Swedish founder mutation. BRCA1 1806C>T (Q563X) and BRCA2 3036del4 gene mutations were the most frequent in our series.

A prospective study on predictive factors linked to the presence of BRCA1 and BRCA2 mutations in breast cancer patients

We prospectively screened a hospital-based population of 1000 successive breast cancer patients receiving adjuvant radiotherapy for predictive factors associated with the presence of BRCA1 and BRCA2 mutations. We offered genetic counseling and DNA analysis to selected patients. About 52% of patients showed at least one presumed predictive factor. Hundred and thirty-seven patients underwent DNA analysis. We identified 14 deleterious mutations (10.2%, 95% CI: 5.2-15.3%): 8 BRCA1 mutations and 6 BRCA2 mutations and 14 variants of uncertain clinical significance. Ovarian cancer in the family history was the only factor significantly associated with the presence of a disease-causing mutation (P < 0.01). Eight of the 14 (57%) mutation carriers had no affected first-degree relatives and in 4 of these there was no family history of breast or ovarian cancer. Clinicians should offer genetic counseling and DNA testing to breast cancer patients from families with breast and ovarian cancer, and to patients who are younger than 45 years when they are diagnosed with breast cancer.

Analysis of BRCA1 and BRCA2 genes in Spanish breast/ovarian cancer patients: a high proportion of mutations unique to Spain and evidence of founder effects

We screened index cases from 410 Spanish breast/ovarian cancer families and 214 patients (19 of them males) with breast cancer for germ-line mutations in the BRCA1 and BRCA2 genes, using SSCP, PTT, CSGE, DGGE, and direct sequencing. We identified 60 mutations in BRCA1 and 53 in BRCA2. Of the 53 distinct mutations observed, 11 are novel and 12 have been reported only in Spanish families (41.5%). The prevalence of mutations in this set of families was 26.3%, but the percentage was higher in the families with breast and ovarian cancer (52.1%). The lowest proportion of mutations was found in the site-specific female breast cancer families (15.4%). Of the families with male breast cancer cases, 59.1% presented mutations in the BRCA2 gene. We found a higher frequency of ovarian cancer associated with mutations localized in the 5' end of the BRCA1 gene, but there was no association between the prevalence of this type of cancer and mutations situated in the ovarian cancer cluster region (OCCR) region of exon 11 of the BRCA2 gene. The mutations 187_188delAG, 330A>G, 5236G>A, 5242C>A, and 589_590del (numbered after GenBank U14680) account for 46.6% of BRCA1 detected mutations whereas 3036_3039del, 6857_6858del, 9254_9258del, and 9538_9539del (numbered after GenBank U43746) account for 56.6% of the BRCA2 mutations. The BRCA1 330A>G has a Galician origin (northwest Spain), and BRCA2 6857_6858del and 9254_9258del probably originated in Catalonia (northeast Spain). Knowledge of the spectrum of mutations and their geographical distribution in Spain will allow a more effective detection strategy in countries with large Spanish populations.

Defective mismatch-repair in patients with multiple primary tumours including colorectal cancer

Individuals with an inherited predisposition to cancer development are at an increased risk of developing multiple tumours. Hereditary non-polyposis colorectal cancer (HNPCC) is one of the most common hereditary cancer syndromes and is estimated to account for approximately 2% of colorectal cancers. However, HNPCC individuals are at an increased risk of developing other tumour types such as cancers of the endometrium, urothelium and small intestine. We have utilised a population-based regional cancer registry to identify all patients with double primary colorectal cancers and at least one additional malignancy and characterised the tumour spectrum in this patient group. We subsequently selected those 47 individuals who had developed at least four malignancies, including two colorectal cancers, for studies of the tumour characteristics associated with HNPCC. In total, these individuals developed 209 tumours, 156 of which were successfully retrieved. Microsatellite instability (MSI), a phenomenon caused by defective mismatch-repair (MMR), was identified in 63/154 (41%) evaluable tumours with a MSI-high pattern in 59 and a MSI-low pattern in four tumours. All tumours were immunohistochemically stained for the MMR proteins MLH1 and MSH2, with loss of expression in 55/63 (87%) MSI tumours and in 2/89 (2%) microsatellite stable (MSS) tumours. This loss affected MLH1 in 24 tumours and MSH2 in 33 tumours. A concordant loss of expression for the same MMR protein in several tumours from the same individual, a pattern that strongly suggests an underlying germline MMR gene mutation, was found in 17/45 (38%) patients and affected MLH1 in 8 patients and MSH2 in 9 patients. We conclude that the development of multiple primary tumours, including synchronous or metachronous colorectal cancers, is associated with an increased frequency of MSI and loss of immunohistochemical expression of MLH1 and MSH2.

BRCA2 T2722R is a deleterious allele that causes exon skipping

Patients with a strong family history of breast cancer are often counseled to receive genetic screening for BRCA1 and BRCA2 mutations, the strongest known predictors of breast cancer. A major limitation of genetic testing is the number of inconclusive results due to unclassified BRCA1 and BRCA2 sequence variants. Many known deleterious BRCA1 and BRCA2 mutations affect splicing, and these typically lie near intron/exon boundaries. However, there are also potential internal exonic mutations that disrupt functional exonic splicing enhancer (ESE) sequences, resulting in exon skipping. Using previously established sequence matrices for the scoring of putative ESE motifs, we have systematically examined several BRCA2 mutations for potential ESE disruption mutations. These predictions revealed that BRCA2 T2722R (8393C-->G), which segregates with affected individuals in a family with breast cancer, disrupts three potential ESE sites. Reverse-transcriptase polymerase chain reaction analysis confirms that this mutation causes exon skipping, leading to an out-of-frame fusion of BRCA2 exons 17 and 19. This represents the first BRCA2 missense mutation shown to be a predicted deleterious protein-truncating mutation and suggests a potentially useful method for determining the clinical significance of a subset of the many unclassified variants in BRCA1 and BRCA2.