miR‑4486 reverses cisplatin‑resistance of colon cancer cells via targeting ATG7 to inhibiting autophagy

Abstract

Cisplatin (DDP) resistance is one of the main causes of treatment failure in patients with colon cancer (CC). Autophagy is a key mechanism of resistance to chemotherapy. Since autophagy-related 7 (ATG7) has been reported to be involved in the regulation of autophagy and DDP resistance for lung and esophageal cancer, the present study aimed to explore the functions of microRNA (miR)-4486 in the autophagy-mediated DDP resistance of CC. The expression level of miR-4486 in HCT116, DDP-resistant HCT116 cells (HCT116/DDP), SW480 and DDP-resistant SW480 cells (SW480/DDP) was quantified by reverse transcription-quantitative PCR. Western blotting was utilized to analyze the expression of ATG7, autophagy-related proteins Beclin 1 and LC3-I/II, as well as apoptosis-related proteins Bcl-2, Bax and cleaved-caspase 3 in HCT116/DDP and SW480/DDP cells. The half maximal inhibitory concentration of DDP on all cell lines and the cell viability of HCT116/DDP and SW480/DDP cells were measured using Cell Counting Kit 8 assay. Luciferase assay was used to examine the potential targets of miR-4486 and ATG7. The effects of upregulating mimic miR-4486 expression on the apoptosis and autophagy of HCT116/DDP and SW480/DDP cells were determined by flow cytometry and electron microscopy, respectively. It was found that miR-4486 expression was significantly decreased in HCT116/DDP and SW480/DDP cells compared with that in HCT116 and SW480 cells. Overexpression of miR-4486 could increase the sensitivity of HCT116/DDP and SW480/DDP cells to DDP by reducing cell viability, promoting apoptosis and inhibiting autophagy through downregulating Beclin 1 expression and the LC3-II/LC3-I ratio. Additionally, ATG7 was identified to be a target gene of miR-4486, where ATG7 overexpression could partially reverse the effects of miR-4486 on cell viability and apoptosis by promoting the formation of autophagosomes. In conclusion, the present results demonstrated that miR-4486 could reverse DDP resistance in HCT116/DDP and SW480/DDP cells by targeting ATG7 to inhibit autophagy.

Contribution of MicroRNAs in Chemoresistance to Cisplatin in the Top Five Deadliest Cancer: An Updated Review

“…et al, 2019 ; Pan et al, 2019 ; Wang et al, 2020c ). Likewise, miR-4486 was also decreased in colorectal cancer cells ( Wang W. et al, 2021 ). Moreover, miR-4443 is also upregulated in lung cancer cells.…”

“…et al, 2019 ; Pan et al, 2019 ; Wang et al, 2020c ). In addition, miR-4486 also enhances autophagy by targeting ATG7 in colorectal carcinoma cells ( Wang W. et al, 2021 ). ATG3 is another key gene involved in autophagy and it is targeted by miR-1 in NSCLC cells ( Hua et al, 2018 ).…”

“…In this way, enhanced ATG7 levels promote the conversion of LC3-I into LC3-II and improve Beclin-1 expression, supporting autophagy and chemoresistance of lung cancer ( Huang FX. et al, 2019 ; Wang et al, 2020c ) and colorectal cancer cells ( Wang W. et al, 2021 ). Beclin-1 also plays an important role in autophagy-induced tumorigenesis and drug resistance, altering cell growth, cellular microenvironment and cell division ( Usman et al, 2021 ).…”