Anticancer Effects of Combined Blue Light and Ionizing Irradiation.

While there have been reports indicating the potential anticancer benefits of blue light irradiation and its enhanced effectiveness when combined with anticancer drugs, no studies have explored its combined use with radiation therapy. In this study, the anticancer effects of blue light irradiation alone and in combination with radiation therapy were investigated in vitro. Blue light was applied using a transilluminator (470 nm). For combination experiments, cells were exposed to X-rays 24 h after blue light irradiation. Cell viability was assessed using the trypan blue exclusion method, and protein expression was analyzed by Western blotting. Blue light irradiation suppressed the proliferation of human head and neck squamous cell carcinoma (HNSCC) cells. Furthermore, combined blue light and X-ray irradiation more effectively inhibited the proliferation of human HNSCC cells compared to either irradiation alone. Mechanistically, the irradiation of HNSCC cell line SAS with blue light suppressed the activity of extracellular signal-regulated kinase (ERK1/2), which is an important kinase that is involved in cell proliferation. Collectively, these findings suggest that blue light suppresses the proliferation of HNSCC cells, at least in part through ERK1/2 inactivation observed in SAS cells, and that its combination with radiation may represent a promising therapeutic approach.