Cumulative effect of photobiomodulation by blue and red light on tumor cells: in vitro study with mammary adenocarcinoma cells - MCF-7.

Although the mechanism of action of photobiomodulation (PBM) on tumor cells is already well described in the literature, its cumulative effect is not. The purpose of this study was to evaluate the cumulative effect of photobiomodulation (PBM) with blue (470 nm) and red (658 nm) light at doses of 6 J/cm² and 19 J/cm², respectively, in mammary adenocarcinoma (MCF-7) tumor cells. The study analyzed how single and sequential exposures to these lights modulated cell viability, proliferation, dsDNA release, nitric oxide (NO) production, and reactive oxygen species (ROS). Experimental analyses were carried out to verify cell viability and proliferation, release of dsDNA into the extracellular environment, production of nitric oxide (NO), and formation of reactive oxygen species (ROS). Exposures caused a reduction in cell viability and/or proliferation and there was no increase in mitosis at any of the wavelengths tested. Blue light promoted a reduction in the production of NO and ROS in all analyses. Red light, in a single irradiation at 6 J/cm², was able to promote an increase in NO rates and two cumulative doses at 19 J/cm² increased the formation of ROS. In this study, PBM with blue and red LED, at doses of 6 J/cm² and 19 J/cm² did not cause an increase in cell proliferation but rather reduced the viability and division capacity of breast adenocarcinoma cells.