Abstract
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.
Highlights
Tongue squamous cell carcinoma (TSCC) is the most common malignancy of the oral cavity, and it is one of the most lethal head and neck cancers worldwide [1,2]
Cell culture Human TSCC cell lines SCC-9, CAL-27, and SCC-25 were bought from American Type Culture Collection (ATCC, USA), and human TSCC cell line HSC-4 was purchased from Japanese Collection of Research Bioresources Cell Bank (JCRB, Japan)
Function of hsa_circ_0002162 on cell proliferation, apoptosis, and invasion In CAL-27 cells, cell proliferation was inhibited in the Circ(–) group compared to the NC(–) group at 48 h (Po 0.05) and 72 h (Po0.01) (Figure 3A) and cell apoptosis was promoted in the Circ(–) group compared to the NC(–) group at 48 h (Po0.01) (Figure 3B and C)
Summary
Tongue squamous cell carcinoma (TSCC) is the most common malignancy of the oral cavity, and it is one of the most lethal head and neck cancers worldwide [1,2]. Investigation of molecular mechanisms underlying TSCC is necessary to aid in the development of novel therapy targets and improve the prognosis of TSCC patients. Previous studies reveal that multiple circRNAs are differentially expressed in several cancers, and their dysregulation contributes to tumor progression by promoting cell viability, cell mobility, epithelial mesenchymal transformation (EMT), and even cell stemness in various carcinomas (such as TSCC, hepatocellular cancer, and gastric cancer) [6,7,8]. As one of the newly discovered circRNAs, hsa_circ_0002162 has been reported to be highly expressed in TSCC tumor tissues compared to adjacent tissues according to a recent study with highthroughput sequencing (in three TSCC tissues and adjacent tissues). MiR-33a-5p, miR-302b-5p, and miR-545-5p are reported to be potential targets of hsa_circ_0002162 in TSCC [9], and these three
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