Hypoxia-Regulated miR-146a Targets Cell Adhesion Molecule 2 to Promote Proliferation, Migration, and Invasion of Clear Cell Renal Cell Carcinoma.

Background/aims: miR-146a has recently been shown to promote cell proliferation, migration, and invasion in many cancers, but the role of miR-146a in clear cell renal cell carcinoma (ccRCC) remains unclear.

Methods: Reverse transcription quantitative PCR (RT-qPCR) was performed to investigate the mRNA expression of miR-146a and CADM2 in ccRCC tissues. The luciferase reporter assay, Western blotting, and ChIP assay were carried out to explore the promoter and the transcription factor of miR-146a. Moreover, the effect of miR-146a and CADM2 on ccRCC cells was explored using methyl thiazolyl tetrazolium, colony formation, and migration and invasion assays. The luciferase reporter assay, RT-qPCR, western blotting, and immunofluorescence assay were carried out to investigate whether CADM2 is directly regulated by miR-146a. A tumor xenograft model and immunohistochemical staining were used to examine the carcinogenic effect of miR-146a and CADM2 in vivo.

Results: miR-146a has been shown to promote cell proliferation, migration, and invasion. Here, we found that miR-146a is highly expressed in ccRCC tissues, whereas CADM2 is down-regulated. Hypoxia can induce the expression of miR-146a by stimulating its promoter. In addition, we demonstrated that miR-146a promoted and CADM2 inhibited proliferation, migration, and invasion of ccRCC cells. The 3' untranslated region (UTR) luciferase reporter assay identified that miR-146a targeted the 3' UTR of CADM2 and negatively regulated its expression. Ectopic expression of CADM2 counteracted the promoting effect of miR-146a on cell proliferation, migration, invasion, and the epithelial-mesenchymal transition process.

Conclusion: Together, the finding of down-regulation of CADM2 by miR-146a can provide new insights into ccRCC pathogenesis and might contribute to the development of novel therapeutic strategies.