Our results support that RAD51C is a rare breast and ovarian cancer susceptibility gene and may contribute to a small fraction of families including breast and ovarian cancer cases and families with only breast cancer.
Deleterious and missense mutations of RAD51C have recently been suggested to modulate the individual susceptibility to hereditary breast and ovarian cancer and unselected ovarian cancer, but not unselected breast cancer (BrC).
Paired analysis of tumour-derived versus blood-derived DNA to determine the prevalence of deleterious somatic variants in OC predisposition genes (<i>ATM</i>, <i>BRCA1/2, BRIP1</i>, <i>MSH2/6</i>, <i>PALB2</i>, <i>RAD51C/D</i> and <i>TP53</i>) and the <i>PIK3CA</i> and <i>PTEN</i> genes in individuals with OC (AGO-TR1 study, NCT02222883).
The analysis also showed a substantial difference in the profile of genes contributing to either BC or OC risk, including genes specifically associated with a high risk of OC but not BC (e.g., RAD51C, and RAD51D).
We performed complete sequencing of RAD51C in germline DNA of 286 female breast and/or ovarian cancer cases with a family history of breast and ovarian cancers, who had previously tested negative for mutations in BRCA1 and BRCA2.
Thirty-one percent of ovarian carcinomas had a deleterious germline (24%) and/or somatic (9%) mutation in one or more of the 13 homologous recombination genes: BRCA1, BRCA2, ATM, BARD1, BRIP1, CHEK1, CHEK2, FAM175A, MRE11A, NBN, PALB2, RAD51C, and RAD51D.
Our data confirm a consistent but low frequency (2/335 families) of inactivating RAD51C mutations among families with a history of both breast and ovarian cancer and an absence of mutations among breast cancer only families (0/1,053 families).
RAD51Cc.-13_14del27 was observed in one familial breast cancer case and c.774delT in one unselected ovarian cancer case, thus confirming that RAD51C mutations are implicated in breast and ovarian cancer predisposition, although their overall frequency seems to be low.
We have screened RAD51C sequence variants by HRMA in 492 breast cancer patients with family history of breast and/or ovarian cancer that were previously tested negative for BRCA1/2.
In 2010 an important finding was published showing that heterozygous mutations in RAD51C were highly penetrant and were able to confer an increased risk for breast and ovarian cancers.
In the Finnish population, we have identified two founder mutations in RAD51C that increase the risk of ovarian cancer but not breast cancer in the absence of ovarian cancer.
Population-based BRCA1/BRCA2/RAD51C/RAD51D/BRIP1/PALB2 testing can prevent 1.86%/1.91% of BC and 3.2%/4.88% of OC in UK/US women: 657/655 OC cases and 2420/2386 BC cases prevented per million.