Endoplasmic Reticulum Stress Promotes Autophagy and Apoptosis and Reduces Chemotherapy Resistance in Mutant p53 Lung Cancer Cells

Abstract

Lung cancer (LC) continues to be one of the most prevalent cancers around the world. During this study we aimed to investigate the involvement of endoplasmic reticulum stress (ERS) in autophagy, apoptosis, and chemotherapy resistance of mutant p53 LC cells. Immunohistochemistry was employed to help determine the p53 mutation status of cancer cells from 92 primary LC patients, who were subsequently assigned to either the mutant p53 (n = 39) or wild-type p53 group (n = 53). Mutant p53 cells exhibited increased expression of the C/EBP homologous protein (CHOP), glucose-regulated protein 78 (GRP78), and inositol-requiring enzyme-1α (IRE1α). The Mutant p53 cells were also found to be sensitive to chemotherapy and displayed decreased expression of PI3K, Akt, and mTOR. The mutant p53 cell lines were treated with tunicamycin to induce ERS and rapamycin in order to inhibit mTOR. Both agents increased the expression of CHOP, GRP78, IRE1α, LC3-II/LC3-I, Atg5, Atg7, caspase-3, caspase-12, cleaved caspase-3, cleaved caspase-12, as well as decreases in cell proliferation as well as the expression levels of PI3K, Akt, and mTOR. Enhanced levels of cell apoptosis and reduced chemotherapy resistance were also detected. The findings of our study suggest that ERS promotes autophagy and apoptosis, while acting to reduce chemotherapy resistance in mutant p53 LC cells by downregulating the PI3K/Akt/mTOR signaling pathway.