Enhanced Anti-Cancer Photodynamic Activity with Photobiomodulation Therapy at Different Wavelengths

Photodynamic therapy (PDT) is a non-invasive therapy that induces photochemical reactions for treating many diseases including cancer using the advantages of light. It is based on the interaction of light at a specific wavelength and light-sensitive chemical which does not have dark toxicity. Thus, PDT is an anticancer therapeutic modality yielding cancer cell death. As with other anticancer therapies, some drawbacks reduce or limit the efficacy of PDT. To eliminate the disadvantages resulting in increased efficacy of PDT, it is combined with other anticancer treatment methods. Together use of PDT with another light therapy that is not used for anticancer purposes normally called photobiomodulation (PBM) or low-level laser/light therapy (LLLT) is becoming popular. The application of PBM to cancer cells has been controversial due to its unwanted and negative effects on them such as increased cell proliferation and metastasis capacities. Nowadays, it has been shown that the application strategy of PBM to the cancer cells before the anticancer treatment has a positive impact on cancer cell death. But this result is highly influenced by cell type, energy densities, and wavelengths of light. In this study, the efficacy of PDT was tried to be increased on PC3 human prostate cancer by pre-treating cells with PBM therapy with 655 and 808-nm wavelengths at 1, 3, and 5 J/cm2 energy densities. PDT was conducted on the cells after incubation of indocyanine green (ICG) at 25, 50, and 100 μM and Chlorin (Ce6) at 2.5, 5, 10, and 25 μM concentrations. As a result, increased cell deaths were 4 observed especially with the PBM application at 808-nm wavelength followed by Ce6-mediated PDT at 50 J/cm2 energy density with maximum additional 63.44% cell death compared to only PDT while increased cell deaths were not observed with PBM application at 655-nm wavelength followed by ICG-mediated PDT at 100 J/cm2 energy density. In addition to the cell viability, the cellular uptake of ICG and Ce6 and amount of ATP produced after PBM with both wavelengths; live and death analysis via staining after Ce6-mediated PDT; the amount of nitric oxide released, reactive oxygen species produced, change in mitochondrial membrane potential after the PBM with both wavelengths and Ce6-mediated PDT were examined. Thus, it can be accomplished by PBM application at specific wavelength and energy density is a promising way to enhance cell death obtained from photodynamic action.