MiR-21-3p promotes hepatocellular carcinoma progression through regulating Smad7/Yap1

Background Hepatocellular carcinoma (HCC) remains the global burden due to its high prevalence and mortality. Emerging evidence confirms that microRNAs (miRNAs) play a vital role in cancer initiation and progression. MiRNAs are widely involved in the regulation of signaling pathways by targeting downstream genes. MiR-21-3p as a liver-enriched miRNA has not been fully investigated. Abnormal activation of TGF-β transduction pathway promoted by deletion of Smad7 matters since HCC occurrence. While the relation between miR-21-3p and Smad7 has not yet been confirmed. We aimed to explore the influence of miR-21-3p on HCC initiation and progression by targeting Smad7 and further facilitating the expression of Yap1. Methods MicroRNA (miRNA) microarray analysis was performed for miRNA screening. Dual-luciferase assay was adopted for target verifying. The expressions of miRNA and related genes were quantified by qRT-PCR, western blotting, and immunohistochemical staining. Flow cytometry and transwell assay were used to discover cell apoptosis, invasion and metastasis abilities. Rat models were established to explore the axis's role in hepatocarcinogenesis. Bioinformatics analysis was performed for analyzing clinical significance. Results ­ MiR-21-3p was significantly increased in HCC, indicating a poor overall survival (OS) rate. High miR-21-3p was associated with advanced stages (P=0.029), especially T stages (P=0.026). Low Smad7/high Yap1 was verified in HCCs and rat models. Smad7 was proved to be the direct target of miR-21-3p. MiR-21-3p's effect on tumor malignant phenotypes and promotion of Yap1 could be partly reversed through transfecting Smad7. Overexpressed Yap1 promoted the downstream effector connective tissue growth factor (CTGF). Co-survival analysis indicated that lower miR-21-3p/higher Smad7 (P=0.0494) and lower miR-21-3p/lower Yap1 group (P=0.0379) patients had better OS rates. GSVA analysis of miR-21-3p and Smad7 related gene sets displayed strong relation with TGF-β signaling pathway in HCC. Conclusions MiR-21-3p promotes HCC migration and invasion via directly inhibiting Smad7 and further improving the expression of Yap1.