Apolipoprotein E2 inhibits mitochondrial apoptosis in pancreatic cancer cells through ERK1/2/CREB/BCL-2 signaling

Background: Apolipoprotein E2(ApoE2) is a pleiotropic protein that influences several aspects of cancer metabolism and development. Evading apoptosis is a vital factor for facilitating cancer cell growth. However, the role and mechanism of ApoE2 in regulating cell apoptosis of pancreatic cancer remain unclear. Methods: In this study, we firstly detected the m RNA and protein expressions of ApoE2 in PANC-1 and Capan-2 cells by real-time polymerase chain reaction and Western blotting. We then performed TUNEL and flow cytometric analyses to explore the role of recombinant human ApoE2, p CMV6-ApoE2 and si ApoE2 in the apoptosis of PANC-1 and Capan-2 cells. Furthermore, we investigated the molecular mechanism through which ApoE2 affected apoptosis in PANC-1 cells using immunofluorescence, immunoprecipitation, Western blotting and co-immunoprecipitation analysis. Results: ApoE2 phosphorylated ERK1/2 and inhibited pancreatic cancer cell apoptosis. In addition, our data showed that ApoE2/ERK1/2 altered the expression and mitochondrial localization of BCL-2 via activating CREB. ApoE2/ERK1/2/CREB also increased the total BCL-2/BAX ratio, inhibited the opening of the mitochondrial permeability transition pore and the depolarization of mitochondrial transmembrane potential, blocked the leakage of cytochrome-c and the formation of the apoptosome, and consequently, suppressed mitochondrial apoptosis. Conclusions: ApoE2 regulates the mitochondrial localization and expression of BCL-2 through the activation of the ERK1/2/CREB signaling cascade to evade the mitochondrial apoptosis of pancreatic cancer cells. ApoE2 may be a distinct prognostic marker and a potential therapeutic target for pancreatic cancer.

WNT5A modulates cell cycle progression and contributes to the chemoresistance in pancreatic cancer cells

BACKGROUND： Although there are many studies on the mechanism of chemoresistance in cancers, studies on the relations between WNT5 A and chemoresistance in pancreatic cancer are rare. The present study was to examine the role of WNT5 A in the regulation of cell cycle progression and in chemoresistance in pancreatic cancer tissues and cell lines.METHODS： Fresh pancreatic cancer and paracarcinoma tissues were obtained from 32 patients. The expressions of WNT5 A,AKT/p-AKT and Cyclin D1 were detected by immunohistochemistry,and the correlation between WNT5 A expression and clinicopathological characteristics was analyzed. The relationship between WNT5 A expression and gemcitabine resistance was studied in PANC-1 and MIAPaCa2 cell lines. The effect of WNT5 A on the regulation of cell cycle and gemcitabine cytotoxicity were investigated. The associations among the expressions of p-AKT,Cyclin D1 and WNT5 A were also analyzed in cell lines and the effect of WNT5 A on restriction-point（R-point） progression was evaluated.RESULTS： WNT5 A, p-AKT and Cyclin D1 were highly expressed in pancreatic cancer tissues, and the WNT5 A expression was correlated with the TNM stages. In vitroWNT5 A expression was associated with gemcitabine chemoresistance. The percentage of cells was increased in G0/G1 phase and decreased in S phase after knockdown of WNT5 A in PANC-1. WNT5 A promoted Cyclin D1 expression through phosphorylation of AKT which consequently enhanced G1-S transition and gemcitabine resistance. Furthermore, WNT5 A enhanced the cell cycle progression toward R-point through regulation ofretinoblastoma protein（pRb） and pRb-E2 F complex formation.CONCLUSIONS： WNT5 A induced chemoresistance by regulation of G1-S transition in pancreatic cancer cells. WNT5 A might serve as a predictor of gemcitabine response and as a potential target for tumor chemotherapy.