RESUMEN
Objective:To investigate the influence and mechanism of micro RNA (miR)-373-3p in autophagy and sunitinib sensitivity of glioblastoma cells.Methods:U251 cells were routinely cultured in vitro; and some U251 cells were subjected to 50 μmol/L sunitinib treatment for 72 h to construct sunitinib-resistant U251 cell line. (1) Real-time reverse transcription quantitative PCR (RT-qPCR) was used to detect the miR-373-3p expression in U251 and sunitinib-resistant U251 cells. Sunitinib-resistant U251 cells were divided into blank control group, nonsense sequence group and miR-373-3p mimic group; cells in the latter 2 groups were transfected with nonsense sequence and miRNA-337-3p mimic, respectively; miR-373-3p expression was detected by RT-qPCR. Cells were divided into U251 group, sunitinib-resistant U251 group, sunitinib-resistant U251+nonsense sequence group, and sunitinib-resistant U251+miR-373-3p mimic group; after each transfection, CCK-8 assay was used to evaluate the cell viability; TUNEL was used to detect the apoptotic rate; immunofluorescent assay was used to detect the expression of microtubule-associated protein light chain 3 (LC3); Western blotting was used to detect the expressions of apoptosis- and autophagy-associated proteins. (2) The pGL3-autophagy-related gene 7 (ATG7) wild-type (WT) and pGL3-ATG7 mutant type (MUT) plasmids were established; dual-luciferase reporter system was used to detect the cell luciferase activity in the miR-373-3p mimic group and nonsense sequence group. Cells were divided into U251 group, sunitinib-resistant U251 group, sunitinib-resistant U251+nonsense sequence group, and sunitinib-resistant U251+miR-373-3p mimic group; after each transfection, RT-qPCR and Western blotting were used to detect the mRNA and protein expressions of ATG7 in the cells. (3) The sunitinib-resistant U251 cells were divided into blank control group, ATG7 negative control group, and ATG7 overexpression group; after each transfection, RT-qPCR and Western blotting were used to detect the ATG7 mRNA and protein expressions. U251 and sunitinib-resistant U251 cells were divided into U251 group, sunitinib-resistant U251 group, sunitinib-resistant U251+nonsense sequence group, sunitinib-resistant U251+miR-373-3p mimic group, sunitinib-resistant U251+miR-373-3p mimic+ATG7 negative control group, and sunitinib-resistant U251+miR-373-3p mimic+ATG7 overexpression group; after each transfection, CCK-8 assay was used to evaluate the cell apoptosis, TUNEL was used to examine the apoptotic rate, and Western blotting was employed to detect the expressions of apoptosis- and autophagy-associated proteins. Results:(1) As compared with that in the U251 cells, miR-373-3p was lowly expressed in sunitinib-resistant U251 cells, with statistic difference ( P<0.05). As compared with that in the blank control group and nonsense sequence group, miR-373-3p expression was significantly elevated in the miR-373-3p mimic group ( P<0.05). As compared with the U251 group, the sunitinib-resistant U251 group had significantly increased cell viability, significantly decreased cell apoptotic rate, statistically increased B lymphocytoma-2 (Bcl-2) and Beclin 1 protein expressions, and significantly increased LC3II/LC3I values, significantly decreased Bcl-2 associated X protein (Bax) and p62 protein expressions and cleaved Caspase3/Caspase 3 values ( P<0.05). As compared with the sunitinib-resistant U251+nonsense sequence group, the sunitinib-resistant U251+miR-373-3p mimic group had significantly decreased cell viability, significantly increased cell apoptotic rate, statistically decreased Bcl-2 and Beclin 1 protein expressions, and significantly decreased LC3II/LC3I values, significantly increased Bax and p62 protein expressions and cleaved Caspase3/Caspase 3 values ( P<0.05). As compared with the U251 group, the sunitinib-resistant U251 group had increased number of fluorescent particles labeled with LC3 and enhanced fluorescent intensity; as compared with the sunitinib-resistant U251+nonsense sequence group, the sunitinib-resistant U251+miR-373-3p mimic group had decreased number of fluorescent particles labeled with LC3 and reduced fluorescent intensity. (2) The luciferase activity of pGL3-ATG7 WT plasmids in the miR-373-3p mimic group was signficantly lower than that in nonsense sequence group ( P<0.05). As compared with those in the U251 group, ATG7 mRNA and protein expressions were both significantly increased in the sunitinib-resistant U251 group ( P<0.05); as compared with those in the sunitinib-resistant U251+nonsense sequence group, ATG7 mRNA and protein expressions were both significantly decreased in the sunitinib-resistant U251+miR-373-3p mimic group ( P<0.05). (3) As compared with the blank control group and ATG7 negative control group, the ATG7 overexpression group had significantly increased ATG7 mRNA and protein expressions ( P<0.05). As compared with the sunitinib-resistant U251+nonsense sequence group, the sunitinib-resistant U251+miR-373-3p mimic group had significantly decreased cell viability, significantly increased cell apoptotic rate, statistically decreased Bcl-2 and Beclin 1 protein expressions, significantly decreased LC3II/LC3I values, significantly increased Bax and p62 protein expressions, and significantly increased cleaved Caspase3/Caspase 3 values ( P<0.05). As compared with the sunitinib-resistant U251+miR-373-3p mimic+ATG7 negative control group, the sunitinib-resistant U251+miR-373-3p mimic+ATG7 overexpression group had significantly increased cell viability, significantly decreased apoptotic rate, statistically increased Bcl-2 and Beclin 1 protein expressions, significantly increased LC3II/LC3I values, significantly decreased Bax and p62 protein expressions, and significantly decreased cleaved Caspase3/Caspase 3 values ( P<0.05) Conclusion:MiR-373-3p can enhance sunitinib sensitivity by regulating autophagy in glioblastoma cells, whose mechanism might be related to targeting ATG7.