Ovarian cancer: Status of homologous recombination pathway as a predictor of drug response.

Epithelial ovarian cancer (EOC), particularly high-grade serous subtype, is associated with germline mutations in BRCA1/BRCA2 genes in up to 20% of the patients. BRCA1/BRCA2 proteins are important components of the homologous recombination (HR) pathway, a vital DNA repair process that protects the genome from double-strand DNA damage. Recent studies revealed frequent somatic mutations of BRCA1/BRCA2 and hypermethylation of the promoter of BRCA1 in EOC, in addition to germline mutations. Comparison of DNA copy number changes in tumors with or without BRCA1/BRCA2 alterations, lead to the identification of several signatures that detect HR pathway defects, here named "HRness". These signatures predict platinum-sensitivity and survival in EOC, as it was previously shown for germline mutations of BRCA1/BRCA2. They are currently investigated in clinical trials as potential predictive biomarker for response to poly(ADP- ribose) polymerase inhibitors.

De Picciotto N ，Cacheux W ，Roth A ，Chappuis PO ，Labidi-Galy SI ... -  《-》

[BRCA1 and BRCA2 - pathologists starting kit].

Škapa P 《-》

Homologous recombination deficiency and ovarian cancer.

The discovery that PARP inhibitors block an essential pathway of DNA repair in cells harbouring a BRCA mutation has opened up a new therapeutic avenue for high-grade ovarian cancers. BRCA1 and BRCA2 proteins are essential for high-fidelity repair of double-strand breaks of DNA through the homologous recombination repair (HRR) pathway. Deficiency in HRR (HRD) is a target for PARP inhibitors. The first PARP inhibitor, olaparib, has now been licensed for BRCA-mutated ovarian cancers. While mutated BRCA genes are individually most commonly associated with HRD other essential HRR proteins may be mutated or functionally deficient potentially widening the therapeutic opportunities for PARP inhibitors. HRD is the first phenotypically defined predictive marker for therapy with PARP inhibitors in ovarian cancer. Several different PARP inhibitors are being trialled in ovarian cancer and this class of drugs has been shown to be a new selective therapy for high-grade ovarian cancer. Around 20% of high-grade serous ovarian cancers harbour germline or somatic BRCA mutations and testing for BRCA mutations should be incorporated into routine clinical practice. The expanded use of PARP inhibitors in HRD deficient (non-BRCA mutant) tumours using a signature of HRD in clinical practice requires validation.

Ledermann JA ，Drew Y ，Kristeleit RS 《-》

The clinical importance of BRCAness in a population-based cohort of Danish epithelial ovarian cancer.

Germline mutations in BRCA1/2 genes predict improved survival and sensitivity to treatment with poly(adenosine-diphosphate-ribose) polymerase inhibitors in epithelial ovarian carcinoma. The prognostic importance of other genetic alterations leading to homologous recombination deficiency, collectively BRCAness phenotype, is unresolved. The aim was to analyze the distribution of homologous recombination deficiency in epithelial ovarian carcinoma caused by mutations in a panel of homologous recombination genes (including BRCA1/2) or epigenetic alterations. A further aim was to investigate the prognostic importance of homologous recombination deficiency, the BRCAness phenotype. We assessed 380 patient specimens from a Danish population-based epithelial ovarian carcinoma cohort for germline and somatic mutations in 18 different homologous recombination genes, including BRCA1 and BRCA2, using next generation sequencing. Epigenetic alteration due to BRCA1 hypermethylation was assessed by pyrosequencing and BRCA1 protein expression was evaluated by immunohistochemistry. Seventeen percent of patients with epithelial ovarian carcinoma carried a germline (9.8%) and/or somatic (6.3%) mutation in 12 (BRCA1, BRCA2, CHEK2, ATM, RAD51D, EMSY, PALB2, BRIP1, ERCC1, RAD50, ATR, RAD51C) of 18 sequenced homologous recombination genes. The homologous recombination mutation rate was similar among the different histologic subtypes, however the type of mutation (BRCA1/2 and other homologous recombination mutations) differed, p=4×10-4. BRCA1 hypermethylation was present in 7.4% of patient specimens for a total BRCAness phenotype of 23.9%. The BRCAness phenotype was associated with improved overall survival in the high-grade serous carcinoma subgroup with a median overall survival of 4.4 years (95% CI 3.0 to 5.3) versus 2.2 years (95% CI 1.9 to 2.4) in BRCAness wildtype, p=0.0002. Multivariate analysis confirmed an independent prognostic value of the BRCAness phenotype among the high-grade serous carcinoma subgroup, hazard ratio 0.65 (95% CI 0.47 to 0.92), p=0.014. The BRCAness phenotype is present in almost one-fourth of epithelial ovarian carcinoma and holds important prognostic information. The implications of our findings in relation to poly(adenosine-diphosphate-ribose) polymerase inhibitor treatment call for further investigation.

Hjortkjær M ，Malik Aagaard Jørgensen M ，Waldstrøm M ，Ørnskov D ，Søgaard-Andersen E ，Jakobsen A ，Dahl-Steffensen K ... -  《-》

Effects of germline and somatic events in candidate BRCA-like genes on breast-tumor signatures.

Bodily WR ，Shirts BH ，Walsh T ，Gulsuner S ，King MC ，Parker A ，Roosan M ，Piccolo SR ... -  《PLoS One》