Photobiomodulation is associated with a decrease in cell viability and migration in oral squamous cell carcinoma

The treatment of squamous cell carcinoma (SCC) involves surgery, chemotherapy, and/or radiotherapy, which can cause mucositis (inflammation of the oral mucosa that causes considerable pain and can compromise the continuity of oncological treatment). Photobiomodulation (PBM) has been successfully used in the treatment of mucositis, but doubts arise regarding the use of laser for areas in which tumor cells may remain. In this study, the effect of PBM on the viability, mitochondrial activity, proliferation, apoptosis, and migration of cells derived from oral SCC was evaluated. SCC9 cells were irradiated with laser (660 and 780 nm, using 11 dosimetric parameters) and submitted to mitochondrial and caspase 3 activity tests after 1 and 3 days. Based on the results, cell viability (neutral red assay), proliferation (BrdU assay), and migration (scratch-wound assay) were evaluated using only the dosimetric parameters recommended for mucositis. Non-irradiated cells served as the control. The experiments were performed in triplicate. The 11 parameters diminished mitochondrial activity and induced tumor cell apoptosis. Using the parameters recommended for mucositis, irradiation with 780 nm (70 mW, 4 J/cm²) proved to be the safest and led to a reduction in cell viability, the induction of apoptosis, and a reduction in the migration capacity of the tumor cells.