OBJECTIVE: To probe into the influence of miR-21 on the proliferation as well as apoptosis of oral squamous cell carcinoma (OSCC) and its causative role. STUDY DESIGN: We adopted microarray for detecting the differentially expressed genes in OSCC tumor tissues and paracancerous tissues. We assessed the link of miR-21 expression with tumor size, lymph node metastasis, and tumor differentiation. We employed CCK-8 and EdU assay for detecting the impact of miR-21 inhibitor and miR-21 mimic on Cal-27 cell proliferation, as well as TUNEL and AnnexinV-FITC/PI double staining for detecting miR-21 expression on cell apoptosis. We forecasted the possible target of miR-21 via TargetScan, as well as detected the interaction of miR-21 with PTEN via luciferase reporter experiment. The function of miR-21 expression in PTEN signaling pathway was monitored via western blot. We constructed PTEN overexpression plasmid and conducted rescue experiment to evaluate overexpressed PTEN on miR-21–induced proliferation. RESULTS: Microarray and RT-qPCR indicated that miR-21 expression increased demonstrably in OSCC. Subsequently, statistical analysis showed that miR-21 expression was plainly correlated with tumor size, lymph node metastasis, tumor differentiation, and smoking history. CCK-8 and EdU method exhibited that miR-21 mimics manifestly promoted Cal-27 cell proliferation, while miR-21 inhibitor blatantly inhibited Cal-27 cell proliferation. TUNEL and V-FITC/PI double staining assay showed that miR-21 inhibitor conspicuously promoted Cal-27 cell apoptosis. CCK-8 and EdU assay exhibited that overexpressed PTEN abolished the pro-proliferation influence of miR-21 mimic. TUNEL and V-FITC/PI experiments pointed out that knocking down PTEN abrogated the pro-apoptosis impact of miR-21 inhibitor. CONCLUSION: miR-21 contributes to OSCC cell proliferation via targeting PTEN and inhibits its apoptosis. © Science Printers and Publishers, Inc.