Metformin causes cancer cell death through downregulation of p53-dependent differentiated embryo chondrocyte 1

• Published in: Journal of biomedical science 2018-11, Vol.25 (1), p.81-81, Article 81
• Main Authors: Hsieh Li, Shu-Man, Liu, Shu-Ting, Chang, Yung-Lung, Ho, Ching-Liang, Huang, Shih-Ming
• Format: Article
• Language: English
• Subjects: Adenosine diphosphate; AMP; AMP-activated protein kinase; Annexin V; Antidiabetics; Antineoplastic Agents - pharmacology; Apoptosis; Apoptosis - drug effects; Autophagy; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - metabolism; Breast cancer; Cancer; Cancer cells; Cell cycle; Cell death; Cell division; Cell Line, Tumor; Cervical cancer; Cervical carcinoma; Cervix; Chondrocytes; Cycloheximide; Cytokines; Cytotoxicity; DEC1; Deoxyribonucleic acid; Diabetes; Diabetes mellitus; DNA; DNA damage; Dosage and administration; Down-Regulation - drug effects; Electron transport; Electron transport chain; Embryos; Flow cytometry; Fluorescein; Fluorescein isothiocyanate; Genes; Health aspects; HeLa Cells; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Humans; Hypoglycemic Agents - pharmacology; Kinases; Membrane potential; Metabolism; Metformin; Metformin - pharmacology; Mitochondria; Mitochondria - physiology; p53; p53 Protein; Penicillin; Proteins; Reactive oxygen species; Reactive Oxygen Species - metabolism; Ribose; Senescence; Stability analysis; Survival analysis; Toxicity; Transfection; Tumor cell lines; Tumor cells; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism
• ISSN: 1423-0127; 1021-7770; 1423-0127
• DOI: 10.1186/s12929-018-0478-5

Metformin is the most commonly used first-line medicine for type II diabetes mellitus. Acting via AMP-activated protein kinase, it has been used for more than 60 years and has an outstanding safety record. Metformin also offers protection against cancer, but its precise mechanisms remain unclear. We first examined the cytotoxic effects of metformin in the HeLa human cervical carcinoma and ZR-75-1 breast cancer cell lines using assays of cell viability, cleaved poly-ADP-ribose polymerase, and Annexin V-fluorescein isothiocyanate apoptosis, as well as flow cytometric analyses of the cell cycle profile and reactive oxygen species (ROS). We later clarified the effect of metformin on p53 protein stability using transient transfection and cycloheximide chase analyses. We observed that metformin represses cell cycle progression, thereby inducing subG1 populations, and had induced apoptosis through downregulation of p53 protein and a target gene, differentiated embryo chondrocyte 1 (DEC1). In addition, metformin increased intracellular ROS levels, but N-acetyl cysteine, a ROS scavenger, failed to suppress metformin-induced apoptosis. Further results showed that metformin disrupted the electron transport chain and collapsed the mitochondrial membrane potential, which may be the cause of the elevated ROS levels. Examination of the mechanisms underlying metformin-induced HeLa cell death revealed that reduced stability of p53 in metformin-treated cells leads to decreases in DEC1 and induction of apoptosis. The involvement of DEC1 provides new insight into the positive or negative functional roles of p53 in the metformin-induced cytotoxicity in tumor cells.