In vitro and in vivo synergistic anti-tumor effect of LIN28 inhibitor and metformin in oral squamous cell carcinoma

Cancer stem cell therapy is becoming a focal point for oral squamous cell carcinoma (OSCC). They can be regulated by tumor glucose metabolism, whereas the regulation is not fully investigated in OSCC. Herein, we studied the synergistic anti-tumor effect of a LIN28 inhibitor C1632 and hypoglycemic medication metformin in OSCC. In this study, OSCC cell lines SCC9 and CAL27 were treated with C1632 and metformin respectively or synergistically. First, western blotting was performed to detect the expression level of LIN28 and its downstream molecule HMGA2. Second, MTT assay was conducted to assess cell proliferation. Next, wound healing assay and transwell assay were applied to evaluate cell migration. Then, xenograft mouse experiment was done to explore anti-tumor effect in vivo. Finally, western blotting was used to investigate the pharmacological mechanisms of the synergistic effect oft he two medication. Results showed that LIN28 and HMGA2 expression decreased significantly in SCC9 and CAL27 cells under 240 mu M C1632 treatment for 72 h. These effects were synergized under combined treatment for 24 h. Cell proliferation ability and migration ability of both cell lines decreased significantly under respective and combined treatment. In xenograft mouse experiment, tumor weights decreased by 48% under 40 mg/kg/3d C1632 treatment, 53% under 250 mg/kg/d metformin treatment and 91% under combined treatment for 18 days. Tumor volumes decreased by 32%, 57% and 47% under C1632, metformin and combined treatment respectively. These results indicated that C1632 and metformin exerts synergistic anti-tumor effects in OSCC cell lines SCC9 and CAL27, and also inhibits xenograft tumor growth in vivo.