Fig. 3.

Circ-SCMH1 functioned as a sponge of miR-338-3p in OSCC cells. A The circinteractome algorithm showed the complementary binding sites among wild-type of circ-SCMH1 (WT-circ-SCMH1), miR-338-3p and mutant-type of circ-SCMH1 (MUT-circ-SCMH1). B, C Dual-luciferase reporter assay examined luciferase activity of SCC-15/DDP and CAL-27/DDP cells co-transfected with WT/MUT-circ-SCMH1 and miR-338-3p mimic (miR-338-3p) or the negative control (miR-NC). D, E RNA immunoprecipitation (RIP) assays of IgG and Ago2 examined RNA levels of circ-SCMH1 and miR-338-3p in cell extracts of SCC-15/DDP and CAL-27/DDP cells. F, G RNA pull-down assay measured circ-SCMH1 enrichment in cell extracts of SCC-15/DDP and CAL-27/DDP cells transfected with biotin-labelled miR-338-3p (bio-miR-338-3p) or bio-miR-NC. H, I RT-qPCR measured miR-338-3p level in OSCC tissues in Resistant and Sensitive groups (N = 31) and cell lines HOK, SCC-15, SCC-15/DDP, CAL-27, and CAL-27/DDP with normalization to GAPDH. J Pearson’s correlation (r) analysis evaluated the relationship between circ-SCMH1 and miR-338-3p expression in DDP-resistant OSCC tissues (N = 31). K RT-qPCR detected circ-SCMH1 level in SCC-15/DDP and CAL-27/DDP cells transfected with circ-SCMH1-overexpression vector (circ-SCMH1) or vehicle vector (pcDNA) with normalization to GAPDH. L RT-qPCR detected miR-338-3p level in SCC-15/DDP and CAL-27/DDP cells transfected with si-NC, si-circ-SCMH1, pcDNA, or circ-SCMH1 with normalization to U6. *P < 0.05 and ****P < 0.0001 from three separate assays