Pathogenic mutations in the tumour suppressor genes BRCA1 and BRCA2 confer increased risks for breast and ovarian cancer and account for approximately 15% of the excess familial risk of breast cancer amongst first-degree relatives of patients with breast cancer. There is considerable evidence indicating that these risks vary by other genetic and environmental factors clustering in families. In the past few years, based on the availability of genome-wide association data and samples from large collaborative studies, several common alleles have been found to modify breast or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. These common alleles explain a small proportion of the genetic variability in breast or ovarian cancer risk for mutation carriers, suggesting more modifiers remain to be identified. We review the so far identified genetic modifiers of breast and ovarian cancer risk and consider the implications for risk prediction. BRCA1 and BRCA2 mutation carriers could be some of the first to benefit from clinical applications of common variants identified through genome-wide association studies. However, to be able to provide more individualized risk estimates, it will be important to understand how the associations vary with different tumour characteristics and their interactions with other genetic and environmental modifiers.

The aim of the study is to investigate the relevance of rs1056663 and rs2708861 HUS1 polymorphisms, and rs104548, rs2981582 and rs2910164 polymorphisms of CASP8, FGFR2 and micro RNA 146A genes, respectively, as risk modifiers in hereditary breast or ovarian cancer (BC/OC) and risk factors in sporadic BC. We performed a case-control study in 189 healthy controls (CG) and 538 BC/OC cases, 340 with familial history of BC/OC (130 carriers of BRCA1/2 mutations and 210 non-carriers) and 198 sporadic BC/OC. The polymorphisms were assessed by real-time PCR using primers and fluorescent-labelled hybridization probes. We found statistically significant differences between familial BC/OC and CG for rs1056663 and rs2708861 HSU1 polymorphisms and rs2981582 FGFR2 polymorphism, particularly in non-carriers of BRCA1/2 mutations. In this group we found statistical differences for rs1056663 HSU1 and rs2981582 FGFR2 polymorphisms (p-trend<0.006). The logistic regression confirmed that rs2981582 FGFR2 polymorphism (OR=2.09; 95% CI 1.35, 3.20) and the interaction between rs1056663 and rs2708861 HUS1 polymorphisms increased the risk of cancer (OR=1.87; 95% CI 1.19, 2.92). Furthermore, we found that the presence of rs1056663 and rs2708861 HUS1 polymorphisms is associated with early age of presentation of BC (p=0.015) in the group of non-carriers of BRCA1/2 mutations. In addition, no association of the polymorphisms studied in sporadic BC was observed. In conclusion, the HUS1 and FGFR2 polymorphisms act as risk BC modifiers in familial BC/OC, particularly in the group of non-carriers of BRCA1/2 mutations.

Pathogenic mutations in the tumour suppressor genes BRCA1 and BRCA2 confer increased risks for breast and ovarian cancer and account for approximately 15% of the excess familial risk of breast cancer amongst first-degree relatives of patients with breast cancer. There is considerable evidence indicating that these risks vary by other genetic and environmental factors clustering in families. In the past few years, based on the availability of genome-wide association data and samples from large collaborative studies, several common alleles have been found to modify breast or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. These common alleles explain a small proportion of the genetic variability in breast or ovarian cancer risk for mutation carriers, suggesting more modifiers remain to be identified. We review the so far identified genetic modifiers of breast and ovarian cancer risk and consider the implications for risk prediction. BRCA1 and BRCA2 mutation carriers could be some of the first to benefit from clinical applications of common variants identified through genome-wide association studies. However, to be able to provide more individualized risk estimates, it will be important to understand how the associations vary with different tumour characteristics and their interactions with other genetic and environmental modifiers.