The variable penetrance of breast cancer in BRCA1 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. The C to T transition in the 3' untranslated region of the prohibitin (PHB) gene alters mRNA function and has been shown to be associated with an increased breast cancer risk among young North-American women who have one first-degree relative with breast cancer. To investigate whether the PHB 3'UTR polymorphism acts as a modifier of hereditary breast cancer risk we performed a case-control study among female BRCA1 mutation carriers, which included 258 cases and 258 controls who were unaffected by ovarian cancer, in situ breast carcinoma or any other type of cancer. Controls were matched to cases by year of birth and BRCA1 mutation (5382insC, 300 T > G, 4153delA). Genotyping analysis was performed using RFLP-PCR. Odds ratios (OR) were calculated using conditional and penalised univariable and multivariable logistic regression. Multivariable penalised logistic regression revealed CT (OR(adj), 2.03; 95% CI, 1.17-3.59) and combined CT + TT (OR(adj), 2.12; 95% CI, 1.23-3.70) genotypes as significant modifiers of breast cancer risk. Breast cancer risk did not differ between carriers of the 300 T > G and 5382insC mutation. Our results suggest that the PHB 3'UTR T allele increases the risk of breast cancer in patients who are already at increased risk of disease.

The prevalence and spectrum of germline mutations in BRCA1 and BRCA2 have been reported in single populations, with the majority of reports focused on White in Europe and North America. The Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) has assembled data on 18,435 families with BRCA1 mutations and 11,351 families with BRCA2 mutations ascertained from 69 centers in 49 countries on six continents. This study comprehensively describes the characteristics of the 1,650 unique BRCA1 and 1,731 unique BRCA2 deleterious (disease-associated) mutations identified in the CIMBA database. We observed substantial variation in mutation type and frequency by geographical region and race/ethnicity. In addition to known founder mutations, mutations of relatively high frequency were identified in specific racial/ethnic or geographic groups that may reflect founder mutations and which could be used in targeted (panel) first pass genotyping for specific populations. Knowledge of the population-specific mutational spectrum in BRCA1 and BRCA2 could inform efficient strategies for genetic testing and may justify a more broad-based oncogenetic testing in some populations.

The prevalence and spectrum of germline mutations in BRCA1 and BRCA2 have been reported in single populations, with the majority of reports focused on White in Europe and North America. The Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) has assembled data on 18,435 families with BRCA1 mutations and 11,351 families with BRCA2 mutations ascertained from 69 centers in 49 countries on six continents. This study comprehensively describes the characteristics of the 1,650 unique BRCA1 and 1,731 unique BRCA2 deleterious (disease-associated) mutations identified in the CIMBA database. We observed substantial variation in mutation type and frequency by geographical region and race/ethnicity. In addition to known founder mutations, mutations of relatively high frequency were identified in specific racial/ethnic or geographic groups that may reflect founder mutations and which could be used in targeted (panel) first pass genotyping for specific populations. Knowledge of the population-specific mutational spectrum in BRCA1 and BRCA2 could inform efficient strategies for genetic testing and may justify a more broad-based oncogenetic testing in some populations.