Valproic acid sensitizes human glioma cells to gefitinib-induced autophagy.
Autophagy and apoptosis represent important cellular processes involved in cancer cell killing mechanisms. Epidermal growth factor receptor inhibitor gefitinib and valproic acid have been implicated in the treatment of malignancies including glioma involving autophagic and apoptotic mechanisms. Therefore, it is interesting to investigate whether a combination of gefitinib and valproic acid shows better cancer cell killing effect on human glioma cells. We found that a nontoxic concentration of valproic acid sensitized U87 and T98G glioma cells to gefitinib cytotoxicity by inhibiting cell growth and long-term clonogenic survival. The augmented consequences were accompanied by the formation of autophagic vacuoles, conversion of microtubule-associated protein-1 light chain 3-II (LC3-II), and degradation of p62. Autophagy inhibitor 3-methyladenosine and chloroquine and genetic silencing of LC3 but not broad-spectrum caspase inhibitor attenuated gefitinib/valproic acid-induced growth inhibition. Gefitinib/valproic acid-induced autophagy was accompanied by the activation of liver kinase-B1 (LKB1)/AMP-activated protein kinase (AMPK)/ULK1. Silencing of AMPK and ULK1 suppressed gefitinib/valproic acid-induced autophagy and growth inhibition. Mechanistic studies showed that gefitinib/valproic acid increased intracellular reactive oxygen species generation and N-acetyl cysteine attenuated gefitinib/valproic acid-caused autophagy and growth inhibition. In addition to demonstrating the autophagic mechanisms of gefitinib/valproic acid, the results of this study further suggest that intracellular oxidative stress and the LKB1/AMPK signaling might be a potential target for the development of therapeutic strategy against glioma.
Department of Surgery, Feng Yuan Hospital, Taichung, Taiwan.|Graduate Institute of Pharmaceutical Science and Technology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
Cheng-Yi
CY
Chang
Division of Urology, Taichung Veterans General Hospital, Taichung, Taiwan.
Jian-Ri
JR
Li
Department of Anesthesiology, Taichung Veterans General Hospital, Taichung, Taiwan.|Department of Financial and Computational Mathematics, Providence University, Taichung, Taiwan.
Chih-Cheng
CC
Wu
Division of Urology, Taichung Veterans General Hospital, Taichung, Taiwan.|Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan.
Yen-Chuan
YC
Ou
Department of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan.
Wen-Ying
WY
Chen
Department of Pharmacology, Chung Shan Medical University, Taichung, Taiwan.|Department of Pharmacy, Chung Shan Medical University Hospital, Taichung, Taiwan.
Yu-Hsiang
YH
Kuan
Department of Nursing, HungKuang University, Taichung, Taiwan.
Wen-Yi
WY
Wang
Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan.|Department of Nursing, HungKuang University, Taichung, Taiwan.|Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan.
Chun-Jung
CJ
Chen
D000263:Adenylate Kinase / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D004789:Enzyme Activation; D000077156:Gefitinib; D005910:Glioma / Q000188:drug therapy*; D006801:Humans; D018384:Oxidative Stress; D011799:Quinazolines / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014635:Valproic Acid / Q000494:pharmacology*
D000970:Antineoplastic Agents; D011799:Quinazolines; D017382:Reactive Oxygen Species; D014635:Valproic Acid; D000263:Adenylate Kinase; D000077156:Gefitinib
EGFR; autophagy; gefitinib; glioma; valproic acid