Tumor suppressor genes BRCA1 and BRCA2 are the two main breast and ovarian cancer susceptibility genes, and their genetic testing has been used to evaluate the risk of hereditary breast and ovarian cancer (HBOC). While several studies have reported the prevalence of BRCA1 and BRCA2 mutations in Japanese populations, there is insufficient information about deleterious mutations compared with western countries. Moreover, because many rare variants are found in BRCA1 and BRCA2, both of which encode large proteins, it is difficult to sequence all coding regions using the Sanger method for mutation detection. In this study, therefore, we performed next-generation sequencing (NGS) analysis of the entire coding regions of BRCA1 and BRCA2 in 135 breast and/or ovarian cancer patients. Deleterious BRCA1 and BRCA2 mutations were detected in 10 patients (7.4%) by NGS analysis. Of these, one mutation in BRCA1 and two in BRCA2 had not been reported previously. Furthermore, a BRCA2 mutation found in a proband was also identified in two unaffected relatives. These data suggest the utility of screening BRCA1 and BRCA2 mutations by NGS in clinical diagnosis.

Approximately 5–10% of all breast and/or ovarian cancer cases are considered as inherited. BRCA1 and BRCA2 tumor suppressor genes account for a high penetrance of hereditary cases, but familial cases without mutations in these genes can also occur. Despite their low penetrance, other hereditary cancer-related genes are known to be associated with breast and ovarian cancer risk. However, the extent to which these genes prevail in breast and ovarian cancer remains to be elucidated. To estimate the frequency of mutations in these predisposition genes, we analyzed the germline mutations of 25 hereditary cancer-related genes in 155 patients using targeted next-generation sequencing. These subjects included 11 BRCA1/2 mutation-positive cases and 144 negative cases. Of these, three patients (1.9%) had pathogenic mutations in ATM, MRE11A, or MSH6, all of which have a central role in DNA repair and the mismatch repair pathway. The MSH6 splice-site mutation (IVS6+1G>T) was predicted to be pathogenic, as demonstrated by in vitro and immunohistochemical analyses. These results suggested deficiencies in cellular DNA repair functions result in the development of breast and ovarian cancer.

BACKGROUND:The contribution of BRCA1 and BRCA2 to ovarian cancer in Japanese patients is still unclear. This study investigated the frequency of germline mutations in BRCA1/2 in Japanese patients with ovarian, peritoneal, or fallopian tube cancer, regardless of their family histories, which were suggestive of hereditary breast and ovarian cancer. METHODS: Ninety-five unselected women with ovarian cancer who were seen from 2013 to 2015 at Yamanashi Prefectural Central Hospital were enrolled. Analyses of BRCA1/2 gene mutations were performed with next-generation sequencing. RESULTS: Twelve of the 95 patients (12.6%), including 5 in the BRCA1 (5.3%) and 7 in the BRCA2 (7.4%), had deleterious mutations. Among the 36 cases with a family history, 6 (16.7%) were found to carry mutations in BRCA1 and BRCA2. Notably, 6 of the 59 cases (10.2%) without a family history also had BRCA1/2 germline mutations. There was no statistical difference between the 2 groups (P 5 .36). The presence of mutations and their clinical relevance were studied. Mutation carriers were diagnosed at advanced stages (100% of positive cases among stage III or IV cases) and had poor prognostic histological subtypes (100% of positive cases had high-grade serous adenocarcinomas). CONCLUSIONS: In this unselected Japanese population, approximately 13% of the cases with ovarian cancer appeared to be associated with an inherited risk, regardless of a family history. This finding indicates that BRCA1/2 genetic testing should be performed for all patients with ovarian cancers. Cancer 2016;122:84-90.

This is the first report on PALB2 mutations in Japan, revealing two missense mutations as "deleterious and probably damaging" by in silico analyses, but no PALB2 premature truncation mutations were identified. The sample size is relatively small and a larger cohort study is needed in Japan.

Utility of combined annotation‐dependent depletion (CADD) score was recently reported to rank pathogenicity as C‐scores ranging 1‐99 for both confirmed deleterious mutation. Using C‐scores for BRCA1/2 variants, we tried to constitute the classification system for variant of uncertain significance (VUS), which had been a major problem of genetic testing for hereditary breast and/or ovarian cancer. We analyzed BRCA1/2 genes for 283 patients with breast and/or ovarian cancer. The deleterious mutation and missesne mutations, minor variant, and wild type of BRCA1 and ‐2 were 5, 27, 251 and 15, 85, 183, respectively. Meanwhile, the variants with C‐score ≥10 were involved in 19/283 (6.7%) in BRCA1 and 34/283 (12%) in BRCA2. All deleterious mutations were included in this group. Frequency of personal history and family history of ovarian cancer were significantly high, and frequency of serous adenocarcinoma of ovary and triple negative breast cancer was relatively high in the group with deleterious mutations. Similar findings were seen in patients with variants of C‐score ≥10. According to the C‐score and population frequency, we could define VUS for 11 patients out of 283 patients (3.9 CADD is useful to classify the variant of BRCA1/2 and selecting the patient who needs further segregation studies.