Hsa_circ_0002162 has a critical role in malignant progression of tongue squamous cell carcinoma through targeting miR-33a-5p

The aim of this study was to explore the effect of hsa_circ_0002162 on regulating cell proliferation, apoptosis, and invasion, and investigate its potential target microRNA (miRNA) in tongue squamous cell carcinoma (TSCC). Hsa_circ_0002162 expression was detected in human TSCC cell lines and human oral keratinocytes (HOK) cell line. Cell proliferation, apoptosis, invasion, and candidate target miRNA expressions were detected in hsa_circ_0002162 knockdown-treated CAL-27 cells and hsa_circ_0002162 overexpression-treated SCC-9 cells. In the rescue experiment, miR-33a-5p knockdown plasmid was transfected into hsa_circ_0002162 knockdown-treated CAL-27 cells, while miR-33a-5p overexpression plasmid was transfected into hsa_circ_0002162 overexpression-treated SCC-9 cells. Subsequently, cell proliferation, apoptosis, and invasion were detected, and then luciferase reporter assay was performed. Hsa_circ_0002162 expression was increased in human TSCC cell lines SCC-9, CAL-27, HSC-4, and SCC-25 compared with HOK. In CAL-27 cells, hsa_circ_0002162 knockdown inhibited cell proliferation and invasion and promoted apoptosis. In SCC-9 cells, hsa_circ_0002162 overexpression enhanced cell proliferation and invasion and suppressed apoptosis. Furthermore, a negative regulation of hsa_circ_0002162 on miR-33a-5p (but not miR-302b-5p and miR-545-5p) was observed. In the rescue experiment, miR-33a-5p knockdown increased cell proliferation and invasion, and decreased apoptosis in hsa_circ_0002162 knockdown-treated CAL-27 cells, whereas miR-33a-5p overexpression decreased cell proliferation and invasion, but increased apoptosis in hsa_circ_0002162 overexpression-treated SCC-9 cells. The luciferase reporter assay showed the direct binding of hsa_circ_0002162 to miR-33a-5p. In conclusion, hsa_circ_0002162 had an important role in malignant progression of TSCC through targeting miR-33a-5p.