Spectrum of germline mutations among Mexican patients with colorectal cancer.

78 Background: Colorectal cancer (CRC) is the third most common cancer in the world, and the second most frequent cause of death due to cancer. 5-10% of CRC cases are due to a hereditary predisposing syndrome, the most frequent being Lynch Syndrome (LS) followed by Familial Adenomatous Polyposis (FAP), characterized by loss of function of mismatch repair genes (MMR) and APC, respectively. The purpose of this study is to describe the spectrum of germline pathogenic variants among Mexican CRC patients using Next-generation sequencing (NGS). Methods: This study is original research approved by IRB; all patients signed the informed consent. 43 patients between 18-60 y/o with CRC were enrolled. NGS was performed using a panel which targeted a set of 94 genes and 284 SNPs known to play a role in cancer predisposing. Bioinformatics data analysis was carried out using Pediatric Cancer Variant Pathogenicity Information Exchange (PeCanPIE) and an in-silico analysis to classify variants according to the American College of Medical Genetics and Genomics (ACMG) guidelines. Results: Mean age 48.71 y/o, 62.6% men. Germline pathogenic and likely pathogenic variants (PV/LP) were identified in 69% of sample. A molecular diagnosis of LS (MLH1, MSH2, MSH6, and PMS2) was confirmed in 12 (28%), and FAP in 5 (11.6%). It is remarkably the presence of 5 PV in PRF1 (2 G149S; 3 A91V), among other unusual genes for CRC. Also 12 double heterozygotes were identified, including one with PRF1 and CHEK2 PV. Conclusions: NGS allow the discover of new pathogenic variants that would not be suspected in classic hereditary syndromes. The understanding of other genes involved in other pathways could expand our understanding in the heritability of CRC. PRF1 emerges as a new candidate gene associated with CRC, previous evidence supports the role of PRF1 in solid tumors beside hematologic malignancies.