Tadashi Nomizu

Evaluation of the diagnostic accuracy of the stop codon (SC) assay for identifying protein-truncating mutations in the BRCA1 and BRCA2 genes in familial breast cancer

AbstractScreening for protein-truncating mutations of the BRCA1 and BRCA2 genes is useful in genetic testing for familial breast cancer because, first, the methods are usually simple and not expensive, and second, the detected mutations indicate pathogenic mutations in general. We evaluated the diagnostic accuracy of the stop codon (SC) assay for detecting protein-truncating mutations in the BRCA1 and BRCA2 genes by comparing the results with DNA sequencing in samples from 29 patients with breast cancer from 24 Japanese families with a history of breast cancer. Protein-truncating mutations were detected in 5 of the 24 families (20.8%; two in the BRCA1 gene and three in the BRCA2 gene). Among the 176 DNA fragments examined using the SC assay, the existence of three protein-truncating mutations (one in the BRCA1 gene and two in the BRCA2 gene) was predicted correctly by the assay. Only one reverse transcriptase-polymerase chain reaction fragment was positive for the SC assay but was negative using DNA sequencing. Our study showed clearly that the SC assay is sensitive (3 of 3, 100%) and specific (172 of 173, 99%) for detecting pathogenic protein-truncating mutations in the BRCA1 and BRCA2 genes, and that it could be useful for screening larger populations.

A case of familial breast cancer with double heterozygosity for BRCA1 and BRCA2 genes

We report an extremely rare case of familial breast cancer with deleterious germline mutations in both BRCA1 and BRCA2 genes, of which, to date, no such case has been reported among Japanese breast/ovarian cancer patients. Genetic testing of the family members indicated that the same double heterozygosity for BRCA1 and BRCA2 genes was transmitted to the paternal cousin, and the same BRCA2 mutation to the younger sister with bilateral breast cancer, younger brother with stomach cancer, and proband’s son and daughter without cancer. Immunohistochemical analysis of BRCA protein expression was performed using breast cancer tissues from the proband with double heterozygosity for BRCA1 and BRCA2 genes and from her sibling without BRCA1 mutation but with BRCA2 mutation. There was no staining of either BRCA in the proband and no staining of BRCA2 in the sibling.

Collaboration of breast cancer clinic and genetic counseling division for BRCA1 and BRCA2 mutation family in Japan.

BackgroundBRCA1 and BRCA2 mutations cause high breast cancer incidence rates as high as 80%. Although prophylactic therapy is still controversial, several prophylactic therapies have been proposed and tried for BRCA1 and BRCA2 mutation carriers. Prophylactic surgery, chemo-prevention and precise screening have been proposed as prophylactic therapy. All BRCA1 and BRCA2 mutation carriers need knowledge about their disease and the countermeasures that are used to protect against onset of disease. Counseling plays an important role in this regard for people with genetic diseases. Therefore, collaboration between breast cancer clinics and genetic counseling services is the most important issue in clinical practice. Our group consists of three national universities and a general hospital. In this article we describe our trial to construct a clinical system against hereditary breast cancer as an interim report for the Japanese Ministry of Health, Labour and Welfare.Patients and MethodsTwenty familial breast cancer patients were registered in this study. The whole sequence of BRCA1 and BRCA2 were analyzed. If pathological mutations were detected, their first degree families were introduced to the counseling division at each institute when candidates visited coun-seling divisions.Results and DiscussionFour cases of a deleterious mutation in BRCA1 or BRCA2 were detected among 20 cases. Their first degree relatives are now under consideration for visiting counseling divisions. The clinical system described in this study should play a role to protect BRCA1 or BRCA2 mutation carriers in Japan.

Molecular and clinical features of the TP53 signature gene expression profile in early-stage breast cancer

Purpose TP53 signature has a robust predictive performance for prognosis in early-stage breast cancer, but the experiment that reported this relied on public microarray data and fresh-frozen samples. Before TP53 signature can be used in a clinical setting, a simple and low-cost diagnostic system using formalin-fixed paraffin-embedded (FFPE) samples is needed. New treatments based on the biological characteristics of TP53 signature are expected to follow. Experimental Design TP53 signature was evaluated in 174 FFPE early breast cancer specimens using digital quantification via the nCounter technique (NanoString). Patients were classified as TP53 signature mutant type (n = 64) or wild type (n = 110). Predictive power of TP53 signature was compared with those of other gene expression signatures in 153 fresh-frozen samples of the same cohort by RNA-seq. The molecular features of TP53 signature were elucidated using TCGA omics data and RNA-seq data to explore new therapeutic strategies for patients with TP53 signature mutant type. Results TP53 signature was a strong predictor of prognosis and was also more accurate than other gene expression signatures and independent of other clinicopathological factors. TCGA data analysis showed that risk score of TP53 signature was an index of chromosomal and genomic instability and that TP53 signature mutant type was associated with higher PD-L1 expression, variation in copy numbers, and numbers of somatic mutations. Conclusions TP53 signature as diagnosed using the nCounter system is not only a robust predictor of prognosis but also a potential predictor of responsiveness to immune checkpoint inhibitors.