Photobiomodulation and Oxidative Stress in Oral Squamous Carcinoma Cells

Objectives: Photobiomodulation therapy (PBMT) has been shown to increase mitochondrial membrane potential of non-cancerous cells while decreasing cancer cell survival when coupled with cytotoxic therapies and oxidative damage. We hypothesized that addition of PBMT will create a synergistic effect on decreasing cellular viability in the presence of reactive oxygen species (ROS) in the oral squamous carcinoma cell line SCC-25.
Methods: Hydrogen peroxide (H₂O₂) was used to induce ROS in SCC-25 and evaluated using a CellROX fluorescent probe in live cells. ROS-induced fluorescence was analyzed on an epifluorescence microscope and quantified using a microplate reader. Cells were grown for 72 hr in the presence of increasing concentrations of hydrogen peroxide at 10, 100, 500 µM. Media and treatments were replaced every 72 hr and cells were treated with or without PBMT using a 660 nm, 75 mW laser probe at 24, 48 and 72 hr after plating with 3 J/cm² energy density. Cellular viability using MTT reagent and mitochondrial membrane potential using JC1 reagent were quantified at 72 hr using a microplate reader and analyzed using two-way ANOVA with Tukey post hoc analysis.
Results: The H₂O₂ dosing strategy effectively maintained an environment of oxidative stress when used at 500 µM. This dose of H₂O₂ resulted in a significant decrease in cellular viability and mitochondrial membrane potential in SCC-25 cells (p<0.05). Addition of PBMT alone, or in combination with H₂O₂ did not alter the effects of H₂O₂ on viability, mitochondrial polarity or cellular morphology.
Conclusions: H₂O₂-induced oxidative stress reduced cellular viability and mitochondrial membrane potential in SCC-25 cells and these results were unaffected by PBMT. PBMT alone did not exhibit effects on viability or mitochondrial membrane polarity. These results provide insight to the use of PBMT to benefit normal oral mucosa during cancer treatment.