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Lynch syndrome is an inherited cancer predisposition syndrome caused by germline defects in any of the mismatch repair (MMR) genes. Diagnosis of carriers makes precision prevention, early detection, and tailored treatment possible. Herein we report a novel founder deletion of 18,758 bp, mediated by Alu repeats on both sides, detected in Ethiopian Jews. The deletion, which encompasses exon 9–10 of the MSH2 coding sequence, is associated mainly with early-onset MSH2/MSH6-deficient colorectal cancer (CRC) and liposarcoma. Testing of 35 members of 5 seemingly unrelated families of Ethiopian origin yielded 10/21 (48%) carriers, of whom 9 had CRC. Age at first tumor diagnosis ranged from 16 to 89 years. Carriers from the oldest generations were diagnosed after age 45 years (mean 57), and carriers from the younger generation were diagnosed before age 45 years (mean 30). Awareness of this founder deletion is important to improve patient diagnosis, institute surveillance from an early age, and refer patients for genetic counseling addressing the risk of bi-allelic constitutional MMR deficiency syndrome.

Pathological features and consequently, tumor response differ between BRCA1/2 carriers and sporadic breast cancer (BC) cases. It is expected that BRCA1/2 associated tumors will be more vulnerable to DNA damaging agents and irradiation due to their function in DNA repair. In addition, very high pathological complete response (pCR) rate of approximately 40-50% to neo-adjuvant chemotherapy were reported by two studies. We describe the clinical outcome, i.e.; complete response (cCR), major pathological response (more than 80% reduction in tumor mass), pathologiacl CR (pCR) and local control rates in 15 BRCA1 and 7 BRCA2 carriers, all diagnosed at stage III and treated with anthracyclin based chemotherapy, mastectomy, and irradiation. cCR were found in 6/15 carriers and in 1/7 BRCA2 carriers (P = 0.3). Rate of major pathological response were 4/15 (26.6%) in BRCA1 compared with none of BRCA2 carriers (P = 0.3). Of them, pCR was recorded in 2/15 of BRCA1 carriers. Clinical and pathological nodal involvements were lower in BRCA1 carriers. While all BRCA2 carriers remained node positive as compared to 50% of BRCA1 carriers (P = 0.047), overall survival was similar in both groups. However, approximately 1/3 of BRCA1 carriers did not respond to chemotherapy and 4/15 died within 5 years of diagnosis. We found a non-significant higher clinical and pathological response rate among BRCA1 carriers in response to neo-adjuvant chemotherapy compared with BRCA2 carriers. Our results suggest chemoresistance of approximately a 1/3 of BRCA1 associated tumors. Tumors of BRCA2 carriers are resistant to chemotherapy, while the estrogen receptor positive nature of tumors results in better post recurrence survival.

Mutations in DNA mismatch repair genes underlie lynch syndrome (HNPCC). Lynch syndrome resulting from mutations in MSH6 is considered to be attenuated in comparison to that caused by mutations in MLH1 and MSH2, thus more likely to be under diagnosed. In this study we report of a common mutation in the MSH6 gene in Ashkenazi Jews. Genetic counseling and diagnostic work-up for HNPCC was conducted in families who attended the high risk clinic for inherited cancer. We identified the mutation c.3984_3987dup in the MSH6 gene in 19 members of four unrelated Ashkenazi families. This mutation results in truncation of the transcript and in loss of expression of the MSH6 protein in tumors. Tumor spectrum among carriers included colon, endometrial, gastric, ovarian, urinary, and breast cancer. All but one family qualified for the Bethesda guidelines and none fulfilled the Amsterdam Criteria. Members of one family also co-inherited the c.6174delT mutation in the BRCA2 gene. The c.3984_3987dup in the MSH6 gene is a mutation leading to HNPCC among Ashkenazi Jews. This is most probably a founder mutation. In contrast to the c.1906G>C founder mutation in the MSH2 gene, tumors tend to occur later in life, and none of the families qualified for the Amsterdam criteria. c.3984_3987dup is responsible for 1/6 of the mutations identified among Ashkenazi HNPCC families in our cohort. Both mutations: c.3984_3987dup and c.1906G>C account for 61% of HNPCC Ashkenazi families in this cohort. These findings are of great importance for counseling, diagnosis, management and surveillance for Ashkenazi families with Lynch syndrome.

Hereditary non-polyposis colon cancer is caused by mutations in DNA mismatch repair genes. The mutation spectrum in the Israeli population is poorly documented except for the c.1906G>C Ashkenazi founder mutation in the hMSH2 gene. To report our experience in HNPCC screening, the mutations detected and the clinical features among a cohort of Israeli patients. Diagnostic work-up was done in a multi-step process guided by clinical and ethnic information. Tumors of suspected patients were tested for microsatellite instability and immunohistochemistry. Based on tumor analyses, we proceeded to mutation screening by DHPLC followed by sequence analysis and multiplex ligase dependent probe amplification. Ashkenazi Jews were first tested for the c.1906G>C founder mutation. Of the 240 families, 24, including Arabs and Jews from different ethnic origins, were tested positive. All tumors that lost expression of mismatch repair proteins also showed microsatellite instability. There was evidence for involvement of hMSH2 (15) hMLH1 (6) and hMSH6 (3) genes. Mutations were identified in 17/24 (71%) patients: 6 Ashkenazi families harbored the c.1906G>C mutation. Eleven other mutations (2 nonsense, 3 splice site and 6 small deletions) were detected. Three of the mutations are novel. No gross deletions or insertions were detected. This is the first report that characterizes the profile of HNPCC in a cohort of patients in Israel. Tumor testing indicated that the 3 main MMR genes are involved, and that mutation spectrum is broad.