Efeito do laser de baixa intensidade sobre a viabilidade, invasividade e potencial osteoclastogênico de células de carcinoma epidermóide de boca

Abstract

Squamous cell carcinoma accounts for 95% of cases oral cancer and treatment normally involves surgery, radiotherapy and/or chemotherapy. Oral

mucositis is the most common complication in patients who receive chemotherapy and radiotherapy. Depending on the severity, this condition can compromise the continuity of cancer treatment. Low-level laser therapy (LLLT) has been used for the treatment and prevention of oral mucositis, but divergent findings are reported regarding the effects of this form of treatment on unintentionally irradiated tumor cells that may remain after cancer treatment. The aim of the present study was to analyze the effect of LLLT (with dosimetric parameters recommended for the treatment of oral mucositis) on the viability, invasiveness and osteoclastogenic potential of a line of oral squamous cell carcinoma (SCC9). The cells were cultured in DMEM/F12 medium supplemented with bovine fetal serum (10%) and hydrocortisone (400ng/mL). The cultures were irradiated with InGaAlP (660nm, 40mW, 4J/cm²) and GaAlAs (780nm, 40 and 70mW, 4J/cm²) lasers. Viability was evaluated after 1 and 3 days using MTT assays, crystal violet, neutral red and caspase 3 activity. Invasiveness was evaluated using the wound assay and osteoclastogenic potential was evaluated after 2 and 9 days based on the expression of IL-11 and PTHrP as well as after 7, 14 and 21 days based on the induction of TRAP activity in monocytes. Non- irradiated cultures served as the control for all evaluations. Statistical analysis involved ANOVA complemented by Tukey’s test. Low-level laser with irradiance at a fluence of 4 J/cm², both wavelengths (660 and 780nm) and both output powers (40 and 70mW) led to a reduction in viability as well as induced apoptosis in SCC9 cells. Cells irradiated with 780 nm at output powers of 40 and 70 mW demonstrated less invasive capacity in comparison to the control group. All dosimetric parameters investigated led to a reduction in the ability of SCC9 cells to induce TRAP activity and express IL-11. The expression of PTHrP was only diminished when cells were irradiated at a wavelength of 780nm and output power of 70mW. The present findings demonstrate that laser irradiation at 780nm, 70 mW and 4J/cm2 reduced the viability, osteoclastogenic potential and invasiveness of SCC9 cells. In contrast, infrared laser (780 nm) at a lower output power (40 mW and 4J/cm2) and red laser (660 nm, 40mW and 4J/cm2) did not demonstrate the same inhibition capacity. The findings underscore the importance of the choice of dosimetric parameters to the efficacy and safety of phototherapy for the treatment of oral mucositis.