Involvement of cellular senescence in the effect of X-irradiated human lung fibroblast WI-38 cells on human lung cancer A549 cell clonogenic potential

Ionizing radiation not only affects irradiated but also non-irradiated surrounding cells through intercellular communication, indicating that the former cells could affect the latter. The present study investigated the effect of X-irradiated normal human lung fibroblast WI-38 cells on the clonofenic potential of human lung cancer A549 cells by co-culturing them. Moreover, the relationship between the effects of co-culturing on the clonogenic potential of A549 cells and cellular senescence in WI-38 cells was investigated. The co-culture with 10-Gy-irradiated WI-38 cells and A549 cells enhanced the clonogenic potential of non- or X-irradiated A549 cells. Irradiated WI-38 cells exhibited high SA-β-gal activity, a cellular senescence hallmark. Importantly, treatment with senolytic drugs, which eliminate senescent cells, not only influenced high-SA-β-gal-activity cell percentages among the irradiated WI-38 cells but also the effect of irradiated WI-38 cells on the clonogenic potential of A549 cells. In conclusion, our results suggest that irradiated WI-38 cells promote A549 cell clonogenic potential and irradiated senescent WI-38 cells contribute to this effect.