PMID- 29554968 OWN - NLM STAT- MEDLINE DCOM- 20190509 LR - 20190509 IS - 1756-9966 (Electronic) IS - 0392-9078 (Print) IS - 0392-9078 (Linking) VI - 37 IP - 1 DP - 2018 Mar 20 TI - Metformin induces autophagy and G0/G1 phase cell cycle arrest in myeloma by targeting the AMPK/mTORC1 and mTORC2 pathways. PG - 63 LID - 10.1186/s13046-018-0731-5 [doi] LID - 63 AB - BACKGROUND: Metformin is a commonly used drug for the treatment of diabetes. Accumulating evidence suggests that it exerts anti-tumor effects in many cancers, including multiple myeloma (MM); however, the underlying molecular mechanisms have not been clearly elucidated. METHODS: The anti-myeloma effects of metformin were evaluated using human MM cell lines (RPMI8226 and U266) in vitro and in vivo NOD-SCID murine xenograft MM model. Cell viability was assessed with CCK8 and cell proliferation was measured by EdU incorporation assay. Cell cycle distribution and apoptosis were examined by flow cytometry. Transmission electron microscopy was used to visualized autophagosomes. Activation of AMPK and inhibition of mTORC1/C2 pathways was assessed by Western blot analysis. RPMI8226 cells and U266 cell lines with AMPK knockdown were generated by transfection with small interfering RNA targeting the AMPK-alpha1 and alpha2 subunits using Lipofectamine 2000 reagent. RESULTS: Metformin effectively inhibited the proliferation of MM cell lines, an effect that was associated with the induction of autophagy and G0/G1 cell cycle arrest, but not apoptosis. Metformin activated AMPK and repressed both mTORC1 and mTORC2 signaling pathways in myeloma cells as well as downstream molecular signaling pathways, such as p-4EBP1 and p-AKT. AMPK activation resulted in direct phosphorylation and activation of tuberous sclerosis complex 2 (TSC2), leading to inhibition of the mammalian target of rapamycin (mTOR). In addition, metformin inhibited myeloma cell growth in an AMPK-dependent manner. The xenograft mouse model further confirmed that metformin inhibited tumor growth by upregulation of AMPK and downregulation of mTOR. CONCLUSIONS: Metformin inhibits the proliferation of myeloma cells by inducing autophagy and cell-cycle arrest. Our results suggest that the molecular mechanism involves dual repression of mTORC1 and mTORC2 pathways via AMPK activation. Our study provides a theoretical basis for the development of novel strategies for the treatment of MM using metformin as an already approved and safe drug. FAU - Wang, Yan AU - Wang Y AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Xu, Wenbin AU - Xu W AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Yan, Zixun AU - Yan Z AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Zhao, Weili AU - Zhao W AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Mi, Jianqing AU - Mi J AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Li, Junmin AU - Li J AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. FAU - Yan, Hua AU - Yan H AD - Department of hematology, Rui Jin Hospital affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, No. 197 Rui-Jin Er Road, Shanghai, 200025, China. yanhua_candy@163.com. LA - eng GR - 81302038/National Natural Science Foundation of China/ GR - 81600155/National Natural Science Foundation of China/ PT - Journal Article DEP - 20180320 PL - England TA - J Exp Clin Cancer Res JT - Journal of experimental & clinical cancer research : CR JID - 8308647 RN - 9100L32L2N (Metformin) RN - EC 2.7.11.1 (Mechanistic Target of Rapamycin Complex 1) RN - EC 2.7.11.1 (Mechanistic Target of Rapamycin Complex 2) RN - EC 2.7.11.31 (AMP-Activated Protein Kinases) SB - IM MH - AMP-Activated Protein Kinases/*metabolism MH - Animals MH - Apoptosis/drug effects MH - Autophagy/*drug effects MH - Cell Line, Tumor MH - Cell Proliferation MH - Disease Models, Animal MH - G1 Phase Cell Cycle Checkpoints/*drug effects MH - Humans MH - Mechanistic Target of Rapamycin Complex 1/*metabolism MH - Mechanistic Target of Rapamycin Complex 2/*metabolism MH - Metformin/*pharmacology MH - Mice MH - Multiple Myeloma/*metabolism MH - Signal Transduction/*drug effects MH - Xenograft Model Antitumor Assays PMC - PMC5859411 OTO - NOTNLM OT - AMPK OT - Autophagy OT - Cell cycle arrest OT - Metformin OT - Myeloma OT - mTOR COIS- COMPETING INTERESTS: The authors declare that they have no competing interests. PUBLISHER'S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. EDAT- 2018/03/21 06:00 MHDA- 2019/05/10 06:00 PMCR- 2018/03/20 CRDT- 2018/03/21 06:00 PHST- 2017/10/28 00:00 [received] PHST- 2018/03/10 00:00 [accepted] PHST- 2018/03/21 06:00 [entrez] PHST- 2018/03/21 06:00 [pubmed] PHST- 2019/05/10 06:00 [medline] PHST- 2018/03/20 00:00 [pmc-release] AID - 10.1186/s13046-018-0731-5 [pii] AID - 731 [pii] AID - 10.1186/s13046-018-0731-5 [doi] PST - epublish SO - J Exp Clin Cancer Res. 2018 Mar 20;37(1):63. doi: 10.1186/s13046-018-0731-5.