Stimulation of Tumor Growth and Angiogenesis With Energy-Dependent Photobiomodulation

Photobiomodulation (PBM) has emerged as a supportive treatment for managing side effects of cancer radiation therapy. However, its safety and potential tumor-stimulating effects under specific irradiation conditions remain unclear. This study aims to evaluate the energy-dependent effects of 808 nm PBM on cellular proliferation, tumor growth, and angiogenesis in vitro and in vivo. B16F10 melanoma cells and tumor-bearing mice were irradiated with 808 nm laser at various energy densities of 0, 5, 10, and 50 J/cm2. In vitro tests revealed that 808 nm PBM significantly increased cell viability to 108% and 108% at 5 and 10 J/cm2, respectively, compared to the control group. In vivo tests demonstrated that 808 nm PBM at 5 J/cm2induced the greatest tumor growth, with a 100-fold increase in relative tumor volume 10 days after the laser irradiation. Histological and western blot analyses confirmed significantly upregulated expression of VEGF and HIF-1α, markers of angiogenesis, and ERK1/2, a key mediator of cell proliferation, in tumors exposed to 5 J/cm2. These findings suggest that 808 nm PBM at a low energy density can stimulate melanoma tumor progression by promoting angiogenesis and cellular proliferation, highlighting the significance of optimizing the energy density and the necessity for establishing safety guidelines for oncologic PBM applications.