Abstract:

Objective To investigate the effect of miR-21-3p on the radiosensitivity of oral squamous cell carcinoma (OSCC) cells. Methods OSCC-related omics data were screened from the GEO database, and bioinformatics analysis was performed to identify differential expression of miR-21-3p. Thirty pairs of tumor tissue samples (cancer and adjacent tissues) were collected from OSCC patients. CAL27 and HN30 cell lines were cultured and irradiated with varying doses of X-rays using an irradiator. qRT-PCR was used to detect miR-21-3p expression level and analyze the effect of different radiation doses, as well as its differential expression in OSCC patients. CAL27 and HN30 cells were divided into groups: Control group, X-ray + control, X-ray + miR-21-3p mimics, and X-ray + miR-21-3p inhibitor. Cell proliferation was assessed by CCK-8 and EdU assays; cell migration was evaluated by wound healing assay; cell invasion was measured by Transwell assay, and clonogenic survival assay was used to detect colony-forming ability. Bioinformatics analysis was conducted to predict the downstream target genes of miR-21-3p; qRT-PCR and dual-luciferase reporter gene assays were used to validate the regulatory effect of miR-21-3p on target genes. Western blot was used to detect phosphorylation levels of key proteins in the PI3K/AKT signaling pathway. Results Bioinformatics analysis revealed that miR-21-3p was highly expressed in OSCC patients. This was further confirmed by qRT-PCR in the 30 collected clinical samples, consistent with the database results. Following irradiation of CAL27 and HN30 cells with increasing doses of X-rays, miR-21-3p expression levels significantly decreased. A significant negative correlation was observed between X-ray dose and miR-21-3p expression. After 10 Gy X-ray irradiation, cell proliferation, colony formation, invasion capacity, and wound healing ability were significantly reduced. Downregulation of miR-21-3p further decreased cell proliferation, invasion, and migration capacity, while upregulation of miR-21-3p significantly attenuated the inhibitory effects of X-ray irradiation on these cellular processes. Bioinformatics analysis identified FBP1 as a downstream target gene of miR-21-3p. qPCR results showed that FBP1 expression was negatively correlated with miR-21-3p levels. The dual-luciferase reporter assay confirmed that miR-21-3p directly targeted the 3' untranslated region(3'UTR) of FBP1. Further investigation revealed that the ratios of p-AKT/AKT and p-PI3K/PI3K decreased following miR-21-3p downregulation and increased following its upregulation. The ratios of p-AKT/AKT and p-PI3K/PI3K were significantly higher in tumor tissues compared to adjacent tissues from OSCC patients. Conclusion miR-21-3p is aberrantly highly expressed in OSCC patients. miR-21-3p reduces the radiosensitivity of OSCC and promotes the proliferation and metastasis of OSCC cells. The molecular mechanism involves targeting FBP1 and activating the PI3K/AKT signaling pathway via phosphorylation.

Key words: oral squamous cell carcinoma, miR-21-3p, radiosensitivity