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POT1 (Protection of Telomeres 1) is a key component of the six-membered shelterin complex that plays a critical role in telomere protection and length regulation. Germline variants in the POT1 gene have been implicated in predisposition to cancer, primarily to melanoma and chronic lymphocytic leukemia (CLL). We report the identification of POT1 p.(I78T), previously ranked with conflicting interpretations of pathogenicity, as a founder pathogenic variant among Ashkenazi Jews (AJs) and describe its unique clinical landscape. A directed database search was conducted for individuals referred for genetic counselling from 2018 to 2023. Demographic, clinical, genetic, and pathological data were collected and analyzed. Eleven carriers, 25 to 67 years old, from ten apparently unrelated families were identified. Carriers had a total of 30 primary malignancies (range 1–6); nine carriers (82%) had recurrent melanoma between the ages of 25 and 63 years, three carriers (27%) had desmoid tumors, three (27%) had papillary thyroid cancer (PTC), and five women (63% of female carriers) had breast cancer between the ages of 44 and 67 years. Additional tumors included CLL; sarcomas; endocrine tumors; prostate, urinary, and colorectal cancers; and colonic polyps. A review of a local exome database yielded an allelic frequency of the variant of 0.06% among all ethnicities and of 0.25% in AJs. A shared haplotype was found in all carriers tested. POT1 p.(I78T) is a founder disease-causing variant associated with early-onset melanoma and additional various solid malignancies with a high tumor burden. We advocate testing for this variant in high-risk patients of AJ descent. The inclusion of POT1 in germline panels for various types of cancer is warranted. [ABSTRACT FROM AUTHOR]

Gene expression assays are widely used to predict risk of recurrence in early breast cancer (BC). We report the 21-gene expression assay (Oncotype Dx) recurrence score (RS) distribution of 27 BRCA carriers with estrogen receptor (ER) positive BCs, identified at Hadassah Medical Center, combined with 2 previous studies. Treatment decision and outcomes of the 27 BRCA carriers were compared with an Israeli cohort of 1594 patients published recently. We found Oncotype Dx RS low (<18), intermediate (18-30) and high (>30) among 12 (21.4%), 23 (41.1%) and 21 (37.5%) of 56 BRCA1 carriers compared with 15 (17.2%), 49 (56.3%) and 23 (26.4%) of 87 BRCA2 carriers ( p = 0.2). The corresponding distribution in a population of 82,434 women published by Genomic Health was 53.4%, 36.3% and 10.3% for low, intermediate and high RS ( p < 0.001 for BRCA1 and BRCA2). Treatment decision regarding chemotherapy according to RS was similar in BRCA1, BRCA2 and the control group. Two of 27 carriers had distant recurrence: a BRCA1 carrier with RS of 18 and a BRCA2 carrier with RS of 22; both have an excellent response to chemotherapy. We found an approximately ∼3 fold increased rate of high RS among BRCA1 and 2 carriers with ER positive BC compared with the general BC population. These data might indicate that hormone positive BC in BRCA carriers are molecularly unique. The surprisingly good response to chemotherapy in the metastatic setting in 2 patients may suggest that the predictive value of low-intermediate RS in carriers merits further studies. [ABSTRACT FROM AUTHOR]