Abstract 3447: APC truncating mutations in Middle Eastern population: Tankyrase inhibitor is an effective strategy to sensitize APC mutant CRC to 5-FU chemotherapy

Colorectal Cancer (CRC) is the leading cause of cancer related death and the most common cancer affecting Saudi males. Mutation of the adenomatous polyposis coli (APC) gene is considered as the initiating step of transformation in familial and sporadic CRC. The prevalence and prognostic role of APC mutation spectra are not well established in Middle Eastern CRC. Next generation sequencing of 412 CRC tumors was performed to determine mutations in APC. Association with protein expression and clinico-pathological correlation was performed. APC truncating mutation is found at a frequency of 58.2% (240/412) and is significantly associated with superior overall survival, whereas no difference in survival between short truncating and long truncating APC was noted. To test the hypothesis that APC mutations might influence 5- Fluorouracil (5-FU) therapy, which is the first line chemotherapy used in CRC, we compared CRC cell lines and showed that those expressing truncated APC exhibit limited response to 5-FU, unlike cells which were APC wild type. In COLO-320 DM and HCT-15, APC mutated CRC cells, we were able to increase sensitivity of APC truncated cells to 5-FU by inhibiting Tankyrase (TNKs) which are members of PARP family, using XAV939. In conclusion, the study identified the prognostic value of APC truncating mutation in Middle Eastern ethnicity. In vitro data further showed that APC mutation can be used as a molecular biomarker to predict response to 5-FU. Furthermore, Tankyrase inhibitor XAV939 selectively targeting APC-mutated CRC cells can be an effective strategy to overcome 5-FU resistance in these cells. Note: This abstract was not presented at the meeting. Citation Format: Sandeep K. Parvathareddy, Abdul K. Siraj, Rong Bu, Prateeshkumar Poyil, Tariq Masoodi, Divya Sasidharan Padmaja, Rica Concepcion, Rafia Begum, Maria A. Sabido, Roxanne Melosantos, Nasser Al-Sanea, Fouad Al-Dayel, Khawla S. Al-Kuraya. APC truncating mutations in Middle Eastern population: Tankyrase inhibitor is an effective strategy to sensitize APC mutant CRC to 5-FU chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3447.