Efeitos da fotobiomodulação com LED azul no comportamento maligno e fenótipo tronco de câncer em linhagens celulares derivadas de carcinoma epidermóide de boca

Abstract

Oral squamous cell carcinoma (OSCC) is a highly aggressive malignant neoplasm characterized by poor prognosis and resistance to conventional therapies. Studies have demonstrated that OSCC tumors contain a subpopulation of cancer stem cells (CSCs), which are responsible for sustaining tumor growth, metastasis, and contributing to treatment failure. Recently, photobiomodulation with blue light has demonstrated antitumor effects; however, its impact on OSCC, particularly on the CSC population, remains largely unexplored. The aim of this study was to evaluate the effect of blue LED photobiomodulation on tumor behavior and CSC properties in OSCC. Two OSCC cell lines, SCC9 and HSC3, were irradiated with blue LED (460 nm, 350 mW, 105, 168, and 210 J/cm²). After 24 hours, cell viability was evaluated using MTS and crystal violet assays. Necrosis and apoptosis were analyzed through Annexin V and DAPI staining by flow cytometry; migration capacity was assessed through a wound-healing assay; and CSC properties were examined through colony and sphere formation assays, RT-qPCR for CSC biomarkers (BMI1, CD44, OCT4, and NANOG), and flow cytometry for CD44 and ESA expression. Cell viability in both cell lines was reduced after blue LED irradiation. Apoptosis increased in SCC9 cells after blue LED exposure but remained unchanged in HSC3 cells. Conversely, blue LED significantly reduced the migratory capacity of both cell lines. Regarding CSC-related properties, blue LED decreased the number of colonies only in SCC9 cells at both irradiation parameters (105 J/cm² and 210 J/cm²), whereas sphere formation was reduced in both cell lines. The expressions of BMI1, OCT4, NANOG and CD44 remained unchanged after blue LED irradiation. Blue LED also did not affect the frequency of CD44high/ESAhigh cells in either cell line; however, at 210 J/cm², the frequency of CD44low cells in SCC9 increased, which is associated with a more differentiated phenotype. Altogether, the results indicate that blue LED photobiomodulation exerts antitumor effects in OSCC by reducing viability, migration, and tumor cell self-renewal, in addition to increasing apoptosis. It also decreased sphere and colony formation, particularly in the SCC9 cell line. These findings suggest that blue LED may modulate tumor behavior in OSCC without significantly altering CSC-associated gene expression, highlighting its potential as a complementary therapy for controlling OSCC progression and supporting further investigation in preclinical and clinical settings.