Abstract 2413: POLE gene mutations in African Americans colorectal cancer

Abstract Background: Most focus in genetic instability in colon carcinogenic transformation was on DNA Mismatch Repair (MMR) genes alterations as they relate to the microsatellite instability phenotype. However, POLE gene mutations can also be instrumental in triggering genetic instability, at even higher magnitude of genome mutation rate. Aim: To assess POLE gene mutations in African Americans with colorectal cancer (CRC). Methods: Data from Whole exome sequencing of 12 CRC African American tumors was searched to scan POLE gene mutations. All detected mutations were checked in tumors and matched normal. The detected mutations were validated in a second set of samples that were sequenced using POLE gene targeted sequencing. Detected and validated mutations were checked in available databases such as COSMIC and dbSNP to determine novel mutations in our population that is at high risk of aggressive CRC. Results: Six out of 12 patients (50%) displayed mutations in POLE gene. There were 41 detected mutations, 11 are novel mutations and 15 are amino-acid changing. Nine of these were non-synonymous and predicted to have deleterious effects. All these mutations were validated using targeted sequencing. In comparison to DNA MMR, POLE gene has four folds more mutations than MSH2gne (10 mutations and MSH6 (11 mutations and two fold more than MSH3 gene (20 mutations) in the same set of 12 cancer/matched normals. The POLE mutations heterozygous/homozygous status was overall similar in normal and matched normal. However, most of the mutations were homozygous. Conclusion: POLE gene mutations are increasingly recognized as another important element in genetic instability. Our data shows that mutations affecting this gene are likely more significant than those affecting DNA MMR genes. Moreover, POLE mutations might be more consequential, especially those affecting its exonuclease domain of polymerase epsilon, proofreading catalytic subunit. Microsatellite-stable, hypermutated CRCs might need to be explored for POLE gene mutations to track the origin of high mutation rates. Citation Format: Hassan Brim, Babak Shokrani, Hamed Azimi, Sudhir Varma, Edward Lee, Hassan Ashktorab. POLE gene mutations in African Americans colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2413.