Effect of Photobiomodulation on Viability and Proliferation of Squamous Cell Carcinoma in Vitro

Head and neck cancer has a multifactorial etiology and significant cellular heterogeneity, which makes treatment difficult and contributes to high mortality rates. The need to combine different therapeutic modalities, such as surgery, chemotherapy, and radiotherapy, increases patient toxicity and requires a multidisciplinary approach to optimize results and improve quality of life. In recent years, photobiomodulation (PBM) has gained ground in tissue rehabilitation and regeneration. However, its effect on squamous cell carcinoma tumor cells lacks investigation. This study evaluated the effects of PBM on head and neck squamous cell carcinoma (SCC) based on cell proliferation and viability. We explored the behavior of two cell lines, SCC09 and CAL27, under 5 sequential applications of PBM using the Fluence HTM® device and laser pens of different wavelengths (830 nm and 658 nm) with irradiation doses of 1, 3, and 6 J/cm². To ensure standardization and avoid unwanted reflections, a specific adapter was developed, maintaining a fixed distance of 20 mm between the light source and the cells in culture, on a black surface. Cell viability was measured through the MTT ([3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide]) experiment and proliferation was evaluated through the Sulforhodamine B (SR-B) assay. No significant effects on cell proliferation or viability of the evaluated cell lines were identified. PBM did not demonstrate a significant effect on cell proliferation and viability under the experimental conditions tested. However, the variability found in other studies highlights the need for additional research to elucidate the mechanisms of action of PBM and establish safe treatment protocols.