Priming cancer cells via photobiomodulation at NIR wavelength to enhance photodynamic action: Insights into mechanistic alterations and cellular migration.

Photodynamic therapy (PDT) is a successful therapy for cancer treatment, especially for the superficial and easily reachable types, such as prostate cancer. During photodynamic activation, the light-sensitive chemical, which generally does not have a toxic effect on cells, can induce oxidative stress by producing reactive oxygen species (ROS). Nevertheless, the outcome of the therapy may be diminished by certain drawbacks. For this, PDT can be coupled with other therapies. Different light therapies can also serve as effective anticancer strategies. The combination of photobiomodulation (PBM) with PDT has become increasingly popular in cancer management. In the present study, PBM, which lacks anticancer activity, was combined with Chlorin e6 (Ce6)-mediated PDT. Underlying causes of additional deaths were elucidated by various mechanistic analyses, including ROS, nitric oxide (NO), mitochondrial membrane potential (ΔΨm), etc. PBM priming at an energy density of 5 J/cm resulted in up to 64 % additional cell death, as demonstrated by colorimetric and dual-staining analyses, and nearly a 100 % decrease in cell migration compared to PDT alone. Besides, PBM priming induced an additional 0.5-fold reduction in NO levels, a 19.4 % increase in ROS levels, and a 1.2 % reduction in ΔΨm compared to only PDT applications. Thus, combining PDT with PBM priming can provide a more effective therapeutic approach and significantly diminish the invasiveness of cancer cells.