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Background: Immature truncated O-GalNAc glycosylation is an important feature of pancreatic ductal adenocarcinomas and is detected ith high frequency in premalignant lesions. Differential expression of O-GalNAc glycans Tn antigen and sialyl-Tn antigen is strongly associated ith decreased survival and poor prognosis and frequently occurs in pancreatic cancer due to hypermethylation of the COSMC C1GALT1C1 gene. COSMC knockdon experiments displayed reduced rate of apoptosis and enhanced migratory behavior, thereby promoting oncogenic properties in pancreatic cancer cells. Since the underlying biological processes are not ell understood, e investigated the impact of aberrant O-GalNAc glycosylation on AKTmTOR signaling in Panc-1 and L3.6pl COSMC knockdon cells. Methods: Lentiviral mediated COSMC knockdon cell lines ere subjected to stable isotope labeling by amino acids SILAC and subsequently analyzed by mass spectromic quantitative proteomics. Immunoprecipitation, Western blot analysis and real time PCR ere used to assess glycotype dependent signaling molecule expression and phosphorylation status. Results: In COSMC knockdon cells, quantitative proteomics identified proteins associated to IGF, EGF and PI3K pathays. We could further identify AKT as novel O-GalNAc-modified protein in Panc-1 pancreatic cancer cell line. AKT donstream substrates S6 ribosomal protein and GSK-3b displayed an enhanced phosphorylation and AKT upstream effectors, such as IGF-I receptor and mTORC2 complex shoed an enhanced activation in COSMC knockdon cells. Interestingly, aberrant O-glycosylation as able to modify mTOR S2448 phosphorylation in L3.6pl COSMC knockdon cells treated ith mTORC inhibitor AZD8055. Conclusions: Our study revealed an enhanced AKTmTOR signaling in pancreatic cancer COSMC knockdon cells, hich is driven by aberrant O-GalNAc glycosylation and substantiates the previously observed enhancement of oncogenic properties.,J Clin Oncol 34, 2016 suppl; abstr e15673 ,Publication Only Gastrointestinal Noncolorectal Cancer
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