Shi-Wei Huang1, Shu-Hao Chang2, Szu-Wei Mu3, Hsin-Yi Jiang3, Sin-Ting Wang3, Jun-Kai Kao4, Jau-Ling Huang5, Chun-Ying Wu6, Yi-Ju Chen7, Jeng-Jer Shieh8. 1. Department of Education and Research, Taichung Veterans General Hospital, Taichung, Taiwan. 2. Institute of Clinical Medicine, National Yang Ming University, Taipei, Taiwan. 3. Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan. 4. Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan; Department of Pediatrics, Children's Hospital, Changhua Christian Hospital, Changhua, Taiwan. 5. Department of Bioscience Technology, Chang Jung Christian University, Tainan, Taiwan. 6. Division of Gastroenterology and Hepatology, Taichung Veterans General Hospital, Taichung, Taiwan. 7. Department of Dermatology, Taichung Veterans General Hospital, Taichung, Taiwan. 8. Department of Education and Research, Taichung Veterans General Hospital, Taichung, Taiwan; Institute of Biomedical Sciences, National Chung Hsing University, Taichung, Taiwan; Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, Taichung, Taiwan. Electronic address: shiehjj@vghtc.gov.tw.
Abstract
BACKGROUND: The tumor suppressor p53 controls DNA repair, cell cycle, apoptosis, autophagy and numerous other cellular processes. Imiquimod (IMQ), a synthetic toll-like receptor (TLR) 7 ligand for the treatment of superficial basal cell carcinoma (BCC), eliminates cancer cells by activating cell-mediated immunity and directly inducing apoptosis and autophagy in cancer cells. OBJECTIVE: To evaluate the role of p53 in IMQ-induced cell death in skin cancer cells. METHODS: The expression, phosphorylation and subcellular localization of p53 were detected by real-time PCR, luciferase reporter assay, cycloheximide chase analysis, immunoblotting and immunocytochemistry. Using BCC/KMC1 cell line as a model, the upstream signaling of p53 activation was dissected by over-expression of TLR7/8, the addition of ROS scavenger, ATM/ATR inhibitors and pan-caspase inhibitor. The role of p53 in IMQ-induced apoptosis and autophagy was assessed by genetically silencing p53 and evaluated by a DNA content assay, immunoblotting, LC3 puncta detection and acridine orange staining. RESULTS: IMQ induced p53 mRNA expression and protein accumulation, increased Ser15 phosphorylation, promoted nuclear translocation and up-regulated its target genes in skin cancer cells in a TLR7/8-independent manner. In BCC/KMC1 cells, the induction of p53 by IMQ was achieved through increased ROS production to stimulate the ATM/ATR-Chk1/Chk2 axis but was not mediated by inducing DNA damage. The pharmacological inhibition of ATM/ATR significantly suppressed IMQ-induced p53 activation and apoptosis. Silencing of p53 significantly decreased the IMQ-induced caspase cascade activation and apoptosis but enhanced autophagy. Mutant p53 skin cancer cell lines were more resistant to IMQ-induced apoptosis than wildtype p53 skin cancer cell lines. CONCLUSION: IMQ induced ROS production to stimulate ATM/ATR pathways and contributed to p53-dependent apoptosis in a skin basal cell carcinoma cell line BCC/KMC1.
BACKGROUND: The tumor suppressor p53 controls DNA repair, cell cycle, apoptosis, autophagy and numerous other cellular processes. Imiquimod (IMQ), a synthetic toll-like receptor (TLR) 7 ligand for the treatment of superficial basal cell carcinoma (BCC), eliminates cancer cells by activating cell-mediated immunity and directly inducing apoptosis and autophagy in cancer cells. OBJECTIVE: To evaluate the role of p53 in IMQ-induced cell death in skin cancer cells. METHODS: The expression, phosphorylation and subcellular localization of p53 were detected by real-time PCR, luciferase reporter assay, cycloheximide chase analysis, immunoblotting and immunocytochemistry. Using BCC/KMC1 cell line as a model, the upstream signaling of p53 activation was dissected by over-expression of TLR7/8, the addition of ROS scavenger, ATM/ATR inhibitors and pan-caspase inhibitor. The role of p53 in IMQ-induced apoptosis and autophagy was assessed by genetically silencing p53 and evaluated by a DNA content assay, immunoblotting, LC3 puncta detection and acridine orange staining. RESULTS:IMQ induced p53 mRNA expression and protein accumulation, increased Ser15 phosphorylation, promoted nuclear translocation and up-regulated its target genes in skin cancer cells in a TLR7/8-independent manner. In BCC/KMC1 cells, the induction of p53 by IMQ was achieved through increased ROS production to stimulate the ATM/ATR-Chk1/Chk2 axis but was not mediated by inducing DNA damage. The pharmacological inhibition of ATM/ATR significantly suppressed IMQ-induced p53 activation and apoptosis. Silencing of p53 significantly decreased the IMQ-induced caspase cascade activation and apoptosis but enhanced autophagy. Mutant p53skin cancer cell lines were more resistant to IMQ-induced apoptosis than wildtype p53skin cancer cell lines. CONCLUSION:IMQ induced ROS production to stimulate ATM/ATR pathways and contributed to p53-dependent apoptosis in a skin basal cell carcinoma cell line BCC/KMC1.
Authors: Eva Villamón; Javier González-Fernández; Esperanza Such; José Vicente Cervera; Daniel Gozalbo; M Luisa Gil Journal: Cancer Cell Int Date: 2018-01-30 Impact factor: 5.722
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