The APC gene encodes a tumor suppressor protein that acts as an antagonist of the Wnt signaling pathway. APC promotes rapid degradation of beta-catenin and participates in Wnt signaling as a negative regulator. APC is also involved in other processes including cell migration, cell adhesion, transcriptional activation and apoptosis. Germline defects in this gene cause familial adenomatous polyposis (FAP), an autosomal dominant pre-malignant disease that usually progresses to malignancy. Disease-associated mutations tend to be clustered in a small region designated the mutation cluster region (MCR) and result in a truncated protein product. Codon I1307 lies within a regulatory region of the APC protein mediated by ubiquitination. Germline APC I1307K is associated with increased colorectal cancer risk by making the gene unstable and prone to acquire mutations during normal cell division. The germline APC I1307K gene mutation is most commonly found in people of Ashkenazi Jewish descent. Therefore, routine colorectal screening is very important in these individuals. One study showed that males had significantly increased I1307K carrier prevalence in lung, urologic, pancreatic, and skin cancers. APC somatic mutations are found 4% of lung adenocarcinomas. The I1307K has not been reported as a somatic mutation in lung adenocarcinomas to date. The prognostic and therapeutic implications of somatic APC mutations in lung adenocarcinomas remain to be fully elucidated. Correlation with other clinical and lab findings is recommended.
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Frayling IM, et al. The APC variants I1307K and E1317Q are associated with colorectal tumors, but not always with a family history. Proc Natl Acad Sci U S A 1998;95(18):10722-7.
Zauber P, et al. Colorectal tumors from APC*I1307K carriers principally harbor somatic APC mutations outside the A8 tract. PLoS One 2014;9(1):e84498.
Leshno, A. et al. The APC I1307K allele conveys a significant increased risk for cancer. Int J Cancer. 2016 Mar 15;138(6):1361-7.
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