S100A10 INCREASES PANCREATIC CANCER CELL RESISTANCE TO GEMCITABINE TREATMENT BY THE INHIBITION OF VMP1-MEDIANTED AUTOPHAGY

PARDO, R; GRASSO, D; MOLEJON MI; IOVANNA, JL; VACCARO, MI

Encuentro; 41st Annual Meeting of the American Pancreatic Association, November 3-6, 2010, Chicago, Illinois.; 2010

Autophagy is a degradation process of cytoplasmic cellular constituents. The pancreatitis-induced vacuole-membrane-protein-1 (VMP1) triggers autophagy in mammalian cells. Recently we showed that Gemcitabine, the standard chemotherapy agent for pancreatic cancer, induces VMP1-mediated autophagy in human pancreatic cancer cells leading to apoptotic cell death. To study this VMP1 pathway we used the two-hybrid strategy. We found that VMP1 interacts with S100A10, a member of the S100 family proteins, which is overeexpressed in pancreatic cancer. VMP1-S100A10 interaction was confirmed using pulldown assay. The real time RT-PCR assay showed that S100A10 mRNA expression is higher in MIAPaCa-2 cells than in HeLa cells. S100A10 was induced under starvation and gemcitabine treatment in HeLa cells, but not in MIAPaCa-2 cells, suggesting that its expression is unregulated in pancreatic cancer cells. The effect of S100A10 overexpression on VMP1-induced autophagy in MIAPaCa-2 cells was evidenced by the recruitment of microtubule-associated protein-1 light-chain-3 (LC3) and we found that S100A10 overexpression reduces the formation of autophagosomes induced by gemcitabine treatment or by VMP1 overexpression. Overexpression of S100A10 modified VMP1 subcellular localization, changing the punctated pattern to a reticular distribution resembling endoplasmic reticulum structure. S100A10 knockdown using shRNA increased apoptosis in gemcitabine-treated cells evidenced by flow cytometry after annexin V/7AAD labeling and by caspase-3 activity assay. We conclude that the expression of S100A10 reduces VMP1-mediated autophagy and increases human pancreatic cancer cell resistance to gemcitabine treatment.