291 Mutations in DNA Polymerase Genes (POLD1 & POLE) in Individuals Having Early-Onset Colorectal Cancer and/or Multiple Adenomas

Colorectal cancer (CRC) screening has been shown to reduce CRC incidence and mortality through the endoscopic detection and removal of colorectal adenomas. Still, these patients are at increased risk for developing metachronous adenomas or even cancer, with the recurrence rate reaching the 50%. The pleiotropic effects of higher levels of PGE2 contribute to key steps of cancer development, including cell proliferation, angiogenesis, invasiveness and migration, inhibition of apoptosis and immunosurveillance as a refletion of deregulation of ATP-binding cassete sub-family c member 4 (ABCC4) and solute carrier organic anion transporter family, member 2A1 (SLCO2A1) genes responsable for carrying PGE2 accross the membrane. To evaluate the influence of genetic polymorphisms in ABCC4 and SLCO2A1 on the risk and time for colorectal adenoma recurrence a retrospective case-cohort study was designed gathering 195 patients diagnosed with colorectal adenomas. Adenoma reccurence was defined has the diagnosis of an adenoma after a total normal colonoscopy at least one year after the initial diagnosis. Thirty-three tagSNPs were characterized using the MassARRAY iPLEX Gold technology based on multiplex amplification followed by mass-spectrometric product separation. Three tagSNPs were identified as susceptibility biomarkers for colorectal adenoma recurrence after a bootstrap analysis. The rs1131598GG homozygous genotype of SLCO2A1 gene was associated with an enhanced risk of 6.3 (95%CI:1.31-30.0, P=0.021). In contrast and under a dominant model of inheritance, the rs1751031 and rs9524821 polymorphisms in ABCC4 gene displayed a protective behaviour (OR=0.29, 95%CI:0.12-0.72, P=0.007 and OR=0.42, 95%CI:0.19-0.93, P=0.033, respectively). Furthermore, when stratifying patients considering the endoscopic findings at baseline colonoscopy, low-risk individuals carriers of rs2274403AA genotype in ABCC4 gene had a lower interval until recurrence (85 (29140) vs 122 (109-135), P=0.011) with 44% of metachronous tumors developing by 36 months (vs 23% for AG/GG). This study demonstrates for the first time the involvement of genetic variants in PGE2 transporters in colorectal adenoma recurrence. The incorporation of genetically-based approaches might allow an optimization of current risk models for the development of metachronous colorectal adenomas or even more advanced lesions possible laeding to a decrease in CRC burden and mortality.