Hypoxia promotes migration and invasion of pancreatic cancer cells via inducing calpain 2 expression / 肿瘤

ABSTRACT

Objective: To investigate the expressions of Calpain 1 and Calpain 2 proteins, as well as the effects of regulating Calpain 2 expression on the migration and invasion of pancreatic cancer PANC-1 cells in hypoxia microenvironment. Methods: The expressions of Calpain 1 and Calpain 2 mRNAs in pancreatic cancer tissues and their survival prognosis value were analyzed using GEPIA (Gene Expression Profiling Interactive Analysis) database online tool. The pancreatic cancer PANC-1 cells were cultured in normoxia (21% O2) and hypoxic (1% O2) environment, then the expressions of Calpain 1 and Calpain 2 mRNAs and proteins were detected by real-time fluorescent quantitative PCR and Western blotting, respectively. The siRNA targeting CAPN2gene(encoding Calpain 2) was transfected into pancreatic cancer PANC-1 cells, then the silencing effect of CAPN2 gene was detected by real-time fluorescent quantitative PCR and Western blotting. The PANC-1 cells with Calpain 2 low expression were cultured under the normoxia and hypoxic conditions, then the migration and invasion abilities of these cells were detected by wound healing test and Transwell chamber assay, the expressions of E-cadherin and Vimentin were detected by Western blotting, and the cell morphology was observed by inverted microscopy. Results: The expressions of Calpain 1 and Calpain 2 mRNAs in human pancreatic cancer tissues were higher than those in normal pancreatic tissues (both P < 0.01), and the high expression of Calpain 2 was associated with the poor prognosis of pancreatic cancer patients (P = 0.013). Compared with the normoxia, the expression levels of Calpain 2 mRNA and protein were increased in hypoxia microenvironment (both P< 0.01), but the expressions of Calpain 1 mRNA and protein were not changed. The Calpain 2 low-expressed PANC-1 cells were established successfully. Under normoxia condition, the down-regulation of Calpain 2 expression inhibited the migration and invasion of PANC-1 cells (both P < 0.05); hypoxia promoted the migration and invasion of PANC-1 cells (both P < 0.05); but the down-regulation of Calpain 2 expression could reverse the promotion effects of hypoxia on the migration and invasion of PANC-1 cells (both P < 0.05). Furthermore, the expression of E-cadherin increased, the expression of Vimentin decreased in PANC-1 cells after the down-regualtion of Calpain 2 expression under normoxia condition (both P < 0.05), while the size of irregular cells increased, and the part of cells had apoptotic change; but the expression of E-cadherin decreased, the expression of Vimentin increased in PANC-1 cells cultured under hypoxia condition (both P < 0.05), while the most of cells had mesenchymal-like changes, showing long shuttle type; but the down-regulation of Calpain 2 expression could reverse the effect of hypoxia on the epithelial-mesenchymal transition of PANC-1 cells (both P< 0.05). Conclusion: Stimulated by hypoxia microenvironment, the expression of Calpain 2 was increased, so as to promote the migration and invasion of PANC-1 cells via regulating E-cadherin and Vimentin expressions.