Effects of photobiomodulation in relation to HeLa Kyoto tumor cells exposed to ionizing radiation

The aim of the work was studying the effects of photobiomodulation of a red spectrum in doses of less than 1 J/cm2 in combination with gamma-irradiation to Hela Kyoto cells. Tumor cells were irradiated with 640 nm LED at different energy densities before and after to gamma-irradiation. Cells viability was determined 24 h after exposure for each gamma-irradiation dose and each PBM mode. There was a statistically significant decrease in a number of viable tumor cells for the samples that were exposed to low-intensity red light prior to gamma-irradiation and a statistically significant increase in a number of viable tumor cells for the samples that were exposed to low-intensity red light after gamma-irradiation. An increase in the number of viable tumor cells exposed to PBM after gamma irradiation correlates with a decrease in the number of cells with a depolarized mitochondrial membrane. The results of a current study need to take into consideration at further studies of PBM effects on tumor cells in vitro as far as clinical studies and clinical application of PBM during radiation therapy. [Display omitted] •Photobiomodulation prior to gamma-irradiation decreases the number of viable tumor cells comparing to the control.•Photobiomodulation after gamma-irradiation increases the number of viable tumor cells comparing to the control.•An increase of viable tumor cells correlates with a decrease of cells with a depolarized mitochondrial membrane.