Vacuole-Membrane-Protein-1 (VMP1) and p21 Expression Regulate Crosstalk Between Autophagy and Apoptosis in Human Pancreatic Cancer.

ROPOLO, A; LOZANO-LEON, A; BOGGIO, V; DOMINGUEZ-MUÑOZ, E; VACCARO, MI

New Orleans, LA, USA.

Congreso; Digestive Disease Week 2010; 2010

American Gastroenterological Association

Pancreatic ductal adenocarcinoma is one of the most aggressive human malignancies with 2-3 % five-year survival rate. Autophagy is a degradation process of cytoplasm constituents. In cancer, autophagy can either be a form of programmed cell death or play a cytoprotective role. VMP1 is a pancreatitis-induced protein whose expression triggers autophagy. We previously showed that VMP1-autophagy pathway promotes apoptotic cell death in PANC-1 and MIAPaCa-2 pancreatic cancer cells. Here, we evaluate the expression of VMP1 and its relationship with p21 and p53 in human pancreatic ductal adenocarcinoma. We also investigated autophagy evaluating LC3 expression, a classic marker of the autophagic process. Two different tissue microarrays were performed from tumor stage advanced; 50-pancreatic ductal adenocarcinomas and seven control samples were included. Immunohistochemistry assays revealed positive expression of VMP1 in glandular cells in 10 (20%) of the tumor samples and none of the controls. The same expression pattern was observed for LC3, suggesting VMP1-mediated autophagy in tumor samples. Tumor samples also showed loss expression of p21, and VMP1 expression in tumor tissue significantly correlated with p21 loss expression (p<0.001). In addition, significant correlation between p21 loss expression and p53 expression (p<0.03) were observed. Interestingly, patient´s survival was higher in VMP1-expressing pancreatic cancer samples. In order to analyze the relationship between VMP1 and p21 expression we used HCT116 and HCT116 p21-/- cells. Real time RT-PCR assay showed a significant increase of VMP1 expression in HCT116 p21-/- cells compared to HCT116 cells. Moreover, starvation-induced autophagy promoted higher activation of VMP1 expression in p21 deficient cells. Also, HCT116 p21-/- cells showed activation of autophagy evidenced by the recruitment of LC3. Finally we study apoptosis development by flow cytometry of anexin V. We found significant reduction of apoptosis levels in HCT116 p21-/- cells compared to HCT116 cells after starvation-induced autophagy. On the contrary, over expression of VMP1 in HCT116 cells showed significant increase of apoptosis after autophagy induction. Our results demonstrate a relationship between VMP1 and p21 expression in human pancreatic cancer and show that the expression of p21 allows apoptosis in VMP1-expressing cells under autophagic stimuli. On the contrary, loss of p21 reduces apoptosis and favors autophagy, disassembling VMP1-mediated autophagy from apoptosis.We conclude that VMP1 and p21 expression are involved in the crosstalk between autophagyand apoptosis in human pancreatic cancer.