Cellular homeostasis and oncology safety of low pulse frequency laser for photobiomodulation in oral and dermal cells.

To evaluate the impact of low-level laser-based photobiomodulation (PBM) on cellular homeostasis and oncology safety by examining viability and proliferation in gingival fibroblasts (HGFs), human dermal fibroblasts (HDFs), and MCF-7 breast cancer cells under different irradiation conditions, and by assessing the signaling-related protein expression in HGFs. The HGFs, HDFs, and MCF-7 cells were exposed to 808 nm diode laser irradiation at 2 and 3 J/cm², applied immediately or 24 h after seeding or continuous dose specifically for MCF-7. Cell viability and metabolic activity were assessed using the MTT assay, and immunohistochemical analysis was performed in HGFs to evaluate the expression of Ki-67, focal adhesion kinase (FAK), integrin β1, COX-1, and COX-2. PBM did not induce cytotoxic effects or excessive proliferation in any cell line. Metabolic activity and growth trends were comparable to non-irradiated controls, preserving cellular homeostasis in fibroblast. Notably, PBM exhibited a neutral effect of MCF-7 cells, supporting its in vitro oncologic safety under the tested conditions. While no significant upregulation of proliferative or inflammatory markers was observed in HGFs. PBM at conservative parameters (2-3 J/cm²) preserves cellular homeostasis and suggests a neutral in vitro effect on neoplastic cells. These findings suggest that these specific protocols are safe for adjunctive clinical applications without promoting undesirable proliferative or inflammatory responses.