Identification of novel BRCA founder mutations in Middle Eastern breast cancer patients using capture and Sanger sequencing analysis.

Ethnic differences of breast cancer genomics have prompted us to investigate the spectra of BRCA1 and BRCA2 mutations in different populations. The prevalence and effect of BRCA 1 and BRCA 2 mutations in Middle Eastern population is not fully explored. To characterize the prevalence of BRCA mutations in Middle Eastern breast cancer patients, BRCA mutation screening was performed in 818 unselected breast cancer patients using Capture and/or Sanger sequencing. 19 short tandem repeat (STR) markers were used for founder mutation analysis. In our study, nine different types of deleterious mutation were identified in 28 (3.4%) cases, 25 (89.3%) cases in BRCA 1 and 3 (10.7%) cases in BRCA 2. Seven recurrent mutations identified accounted for 92.9% (26/28) of all the mutant cases. Haplotype analysis was performed to confirm c.1140 dupG and c.4136_4137delCT mutations as novel putative founder mutation, accounting for 46.4% (13/28) of all BRCA mutant cases and 1.6% (13/818) of all the breast cancer cases, respectively. Moreover, BRCA 1 mutation was significantly associated with BRCA 1 protein expression loss (p = 0.0005). Our finding revealed that a substantial number of BRCA mutations were identified in clinically high risk breast cancer from Middle East region. Identification of the mutation spectrum, prevalence and founder effect in Middle Eastern population facilitates genetic counseling, risk assessment and development of cost-effective screening strategy.

A very low incidence of BRAF mutations in Middle Eastern colorectal carcinoma.

BACKGROUND: Recent studies emphasize the role of BRAF as a genetic marker for prediction, prognosis and risk stratification in colorectal cancer. Earlier studies have reported the incidence of BRAF mutations in the range of 5-20% in colorectal carcinomas (CRC) and are predominantly seen in the serrated adenoma-carcinoma pathway characterized by microsatellite instability (MSI-H) and hypermethylation of the MLH1 gene in the setting of the CpG island methylator phenotype (CIMP). Due to the lack of data on the true incidence of BRAF mutations in Saudi Arabia, we sought to analyze the incidence of BRAF mutations in this ethnic group. METHODS: 770 CRC cases were analyzed for BRAF and KRAS mutations by direct DNA sequencing. RESULTS: BRAF gene mutations were seen in 2.5% (19/757) CRC analyzed and BRAF V600E somatic mutation constituted 90% (17/19) of all BRAF mutations. BRAF mutations were significantly associated with right sided tumors (p = 0.0019), MSI-H status (p = 0.0144), CIMP (p = 0.0017) and a high proliferative index of Ki67 expression (p = 0.0162). Incidence of KRAS mutations was 28.6% (216/755) and a mutual exclusivity was noted with BRAF mutations (p = 0.0518; a trend was seen). CONCLUSION: Our results highlight the low incidence of BRAF mutations and CIMP in CRC from Saudi Arabia. This could be attributed to ethnic differences and warrant further investigation to elucidate the effect of other environmental and genetic factors. These findings indirectly suggest the possibility of a higher incidence of familial hereditary colorectal cancers especially Hereditary non polyposis colorectal cancer (HNPCC) syndrome /Lynch Syndrome (LS) in Saudi Arabia.