High prevalence of BRCA1 founder mutations in Greek breast/ovarian families.

We have screened 473 breast/ovarian cancer patients with family history, aiming to define the prevalence and enrich the spectrum of BRCA1/2 pathogenic mutations occurring in the Greek population. An overall mutation prevalence of 32% was observed. Six BRCA1 recurrent/founder mutations dominate the observed spectrum (58.5% of all mutations found). These include three mutations in exon 20 and three large genomic deletions. Of the 44 different deleterious mutations found in both genes, 16 are novel and reported here for the first time. Correlation with available histopathology data showed that 80% of BRCA1 carriers presented a triple-negative breast cancer phenotype while 82% of BRCA2 carriers had oestrogen receptor positive tumours. This study provides a comprehensive view of the frequency, type and distribution of BRCA1/2 mutations in the Greek population as well as an insight of the screening strategy of choice for patients of Greek origin. We conclude that the Greek population has a diverse mutation spectrum influenced by strong founder effects.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study.

BACKGROUND: The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity. METHODS: To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively. RESULTS: There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele. CONCLUSION: The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.