Expression of miR-21 in renal clear cell carcinoma and its effects on cell proliferation and apoptosis / 西安交通大学学报(医学版)

ABSTRACT

Objective To investigate the expression of miR-21 in renal clear cell carcinoma and its clinical significance as well as how miR-21 regulates the proliferation and apoptosis of 786-O renal clear cell carcinoma cell line through regulating programmed cell death 4 (PDCD4).Methods By analyzing the data of renal clear cells cancer in The Cancer Genome Atlas (TCGA)database,we compared the expression of miR-21 in renal cancer tissues and adjacent normal tissues and explored the differences in miR-21 level in renal cancer at different clinicopathological stage,T stage,N stage and M stage.We also analyzed the association between miR-21 level and survival of patients by Kaplan-Meier method and Log-rank test.786-O cells were transfected with AS-miR-21 to deplete miR-21. MTT assay and flow cytometry were applied to measure cell proliferation and apoptosis, respectively.We then measured the mRNA and protein levels of PDCD4 in 786-O cells depleted for miR-21 by qRT-PCR and Western blot,respectively,and performed a dual-luciferase assay to detect the direct regulation of PDCD4 by miR-21.Results Expression of miR-21 was significantly higher in renal cancer tissues than in adjacent tissues(P <0.0001).The expression levels of miR-21 at stage Ⅲ and stage Ⅳ renal cancer were significantly higher than that at stage Ⅰ (both P <0.0001).Moreover,miR-21 expression was positively correlated with clinicopathological stages of renal cancer by correlation analysis (r =0.262,P <0.0001 ).The correlation test indicated that miR-21 level was also positively correlated with T stage of renal cancer (r =0.250,P <0.0001 ),lymph node metastasis (N1)and distant metastasis (all P <0.0002).Patients with high miR-21 expression had significantly shorter median survival time than those with low miR-21 expression (Log-rank P < 0.001 ).Compared with control cells,786-O cells depleted for miR-21 showed significantly decreased cell proliferation (P <0.05 )and increased cell apoptosis rate (P =0.005 ).PDCD4 mRNA (P = 0.002 )and protein levels were significantly elevated in 786-O cells with down-regulated miR-21 levels.In addition,the dual-luciferase reporter assay showed that the relative luciferase intensity of PDCD4 reporter in cells transfected with AS-miR-21 was significantly higher than that of control cells (P =0.003).Conclusion miR-21 expression was up-regulated in renal cancer and correlated with clinicopathological stage and survival of patients.miR-21 promoted 786-O cell proliferation and inhibited apoptosis probably through regulating PDCD4 expression. These results indicate that miR-21 plays an important role in formation and development of renal cancer.