Study on the sensitizing effect of SM-1 combined with irradiation on head and neck squamous cell carcinoma.

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is globally prevalent with high recurrence, low survival rate, and poor quality of life for patients. Derived from PAC-1, SM-1 can activate procaspase-3 and induce apoptosis in cancer cells to exert anti-tumor effects. However, the inhibitory effect of SM-1 on HNSCC after combination with radiation are unclear. This study aims to investigate the radiosensitizing effect of SM-1 on HNSCC in vitro and in vivo.

METHODS

MTT method was used to detect the effect of SM-1 on the viability of HNSCC cell lines (HONE1, HSC-2, and CAL27). The effects of SM-1 combined with radiation on the survival index of HONE1, HSC-2, and CAL27 cell lines were determined by colony formation assay. Flow cytometry was used to investigate the effects of SM-1 and radiation combination on cell apoptosis and cell cycle, and western blot experiments were performed to detect the expression of apoptosis and cell cycle-related proteins. Finally, a xenograft tumor model of CAL27 was established to evaluate the anti-tumor effect of SM-1 combined with radiation in vivo.

RESULTS

In vitro, SM-1 effectively inhibited the activity of HNSCC cell lines HONE1, HSC-2, and CAL27 cells, and synergistically showed anti-proliferation activity during combined irradiation. Meanwhile, anti-tumor effect of SM-1 on HNSCC was higher than that of Debio1143, and the radiosensitivity of cells was greatly increased. Flow cytometry and western blot analysis showed that SM-1 induced G2/M phase arrest of head and neck squamous cell carcinoma cells via inhibiting the expression of CyclinB1 and CDC2. Moreover, SM-1 activated caspase-3 activity and up-regulated the cleaved form of PARP1 to induce cell apoptosis. In vivo, SM-1 combined irradiation showed a good anti-tumor effect.

CONCLUSION

SM-1 enhances HNSCC cell radiation sensitivity in vitro and in vivo, supporting its potential as a radiosensitizer for clinical trials in combination with radiotherapy.