Blue light photobiomodulation attenuates aggressiveness and stemness features in oral squamous carcinoma cells

This study aimed to evaluate the effect of blue light therapy on tumor behavior and cancer stem cells properties in oral squamous cell carcinoma (OSCC).

The OSCC cell lines SCC9 and HSC3 were exposed to blue light irradiation at 105, 168, and 210 J/cm². After 24 h, cell viability was evaluated using MTS and crystal violet assays. Apoptosis and necrosis were analyzed by Annexin V and DAPI staining through flow cytometry; migration was assessed by wound-healing assay; and cancer stem cells properties were examined by colony and sphere formation assays, RT-qPCR for cancer stem cells biomarkers (BMI1, CD44, OCT4, NANOG), and flow cytometry for CD44 and ESA expression.

Blue light irradiation reduced cellular viability in both cell lines and increased apoptosis in SCC9 cells, while no change was observed in HSC3. Blue light irradiation significantly decreased migration in both cell lines. Regarding cancer stem cells characteristics, blue light reduced colony formation in SCC9 at 105 and 210 J/cm² and sphere formation in both cell lines. Expression of BMI1, OCT4, NANOG, and CD44 genes was not altered, as well as the frequency of CD44^high/ESA^high cells. However, at 210 J/cm², SCC9 showed an increase in CD44^low cells, associated with a more differentiated phenotype.

Blue light irradiation reduced viability and migration in both OSCC cell lines and induced apoptosis only in non-metastatic SCC9 cells. Blue light exerted anti-tumor effects without promoting cancer stem cells properties, while decreasing their ability to self-renew.