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Cisplatin (DDP) is the first-line drug for the treatment of gastric cancer (GC). However, DDP resistance is common. Autophagy, which is closely related to chemoresistance, is a process of resolving and recycling proteins and damaged cellular organs. Additionally, O-6-methylguanine-DNA methyltransferase (MGMT) is responsible for alkylating drug resistance. However, the relationship between autophagy and MGMT in response to DDP in GC is still unknown. In the present study, we determined that autophagy induced by DDP decreases chemosensitivity in GC cell lines. DDP may have induced autophagy in GC by inhibiting MGMT to increase autophagy-related gene (ATG) 4B. Inhibition of MGMT-mediated ATG4B suppression resulted in autophagy induction and DDP resistance. In vivo, combined DDP and autophagy inhibitor chloroquine (CQ) enhanced the anti-tumor effect of DDP; additionally, the negative correlation of MGMT and ATG4B was confirmed. High expression of MGMT and low expression of ATG4B were significantly correlated with favorable five-year survival rate (P <  0.05) in 66 clinicopathologically characterized GC cases. Our study demonstrate that DDP inhibits MGMT-mediated autophagy suppression to decrease chemosensitivity in GC, which provides a novel therapeutic strategy to promote DDP chemosensitivity in GC., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2020 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Cancer stem cells (CSCs), which comprise a small proportion of total cancer cells, have special capacities for self-renewal, differentiation and tumor formation. Currently, CSCs are regarded as the major cause of the failure in anticancer therapy, such as chemoresistance and/or radioresistance, tumor recurrence and metastasis. Autophagy, a process of cellular self-digestion and response to stress, has a role in tumor formation and progression, and it may play a dual role in CSCs-related resistance to anticancer therapy. Most researchers believe that autophagy contributes to stemness maintenance of CSCs and is responsible for the failure of anticancer therapy. Unexpectedly, several studies have also suggested that loss of stemness in CSCs could be mediated by autophagy. Here, we review the recent advances in CSCs and autophagy, especially analyze the complex relationship between them, and hope to apply this new knowledge to the strategies for anticancer therapy., (Copyright © 2017 Elsevier B.V. All rights reserved.)