Low-power red laser and blue LED on circadian gene mRNA levels in human breast cancer cells

Low-power blue light-emitting diode (LED) and red laser have been used for therapeutic proposals based on photobiomodulation (PBM). This effect is trigged after absorption of radiation by photoacceptors, which lead to molecular, cellular and systemic responses. Cryptochromes are involved in circadian cycle control, and associated with development and progression of tumors. Despite such proteins are able to absorb violet-blue lights, there are few data on their participation in PBM. Thus, this work aims to evaluate the effects of radiations emitted by low-power blue LED (470 nm) and red laser (658 nm) on mRNA levels from cryptochromes genes as well as those from involved in their regulation in human breast cancer cells. The MCF-7 and MDA-MB-231 cells were exposed to low-power blue LED (470 nm, 640 J cm-2) and red laser (660 nm, 9 J cm-2), and relative mRNA levels from CRY1, CRY2, PER2, BMAL1 and CLOCK genes were evaluated by reverse transcription-quantitative polymerase chain reaction. The results suggested that exposure to low-power blue LED and red laser do not alter the mRNA levels from cryptochromes genes, and those involved in their regulation, in MCF-7 and MDA-MB-231 human breast cancer cells.