Exploring the effects of low‐level laser therapy on fibroblasts and tumor cells following gamma radiation exposure

Abstract

Ionizing radiation (IR) induces DNA damage and low-level laser therapy (LLLT) has been investigated to prevent or repair detrimental outcomes resulting from IR exposure. Few in vitro studies, however, explore the biological mechanisms underlying those LLLT benefits. Thus, in this work, fibroblasts and tumor cells are submitted to IR with doses of 2.5 Gy and 10 Gy. After twenty-four-h, the cells are exposed to LLLT with fluences of 30 J cm , 90 J cm , and 150 J cm . Cellular viability, cell cycle phases, cell proliferation index and senescence are evaluated on days 1 and 4 after LLLT irradiation. For fibroblasts, LLLT promotes - in a fluence-dependent manner - increments in cell viability and proliferation, while a reduction in the senescence was observed. Regarding tumor cells, no influences of LLLT on cell viability are noticed. Whereas LLLT enhances cell populations in S and G /M cell cycle phases for both cellular lines, a decrease in proliferation and increase in senescence was verified only for tumor cells. Putting together, the results suggest that fibroblasts and tumor cells present different responses to LLLT following exposure to gamma-radiation, and these promising results should stimulate further investigations. Senescence of tumor cells and fibroblasts on the 4 day after ionizing radiation (IR) and low-level laser therapy (LLLT) exposures. The number of senescent cells increased significantly for tumor cells (a) while for fibroblasts no increment was observed (b). The blue collor indicates senescence activity.

Safety and efficacy of photobiomodulation therapy in oncology: A systematic review

“…A total of 43 in vitro studies examining the effect of PBMT on diverse cancer cells types with varying PBM parameters were included (Table 1). 19‐64 …”

Review on the Cellular Mechanisms of Low-Level Laser Therapy Use in Oncology

“…There were also reports that demonstrated the difference in responses between cancer cells and normal cells to LLLT. Silva et al ( 61 ) compared viability, proliferation and cell cycle phase changes between irradiated fibroblasts and breast cancer cells (MDA-MB-231), using 2.5 and 10 Gy ionizing radiation (IR) and LLLT (GaAlAs laser 660 nm, 30, 90, or 150 J/cm 2 ) at 24 h post-IR. LLLT promoted cell viability and proliferation with reduction of senescence in fibroblasts.…”

Conservative treatment of lymphedema: the state of the art

“…[60][61][62] Several studies using low-power sources and wavelengths have been published reporting the safety of red and NIR laser irradiation in terms of stimulation of tumor cell growth. [63][64][65][66][67][68][69] Cialdai et al 70 showed that irradiation with a highpower dual wavelength (808 nm and 905 nm) NIR laser did not affect the behavior of human dermal fibroblasts and breast adenocarcinoma cell lines in terms of proliferation, cell cycle progression, apoptosis, or cloning efficiency. These results are consistent with the possibility of safely administering NIR laser irradiation for management of secondary lymphedema due to cancer.…”