Polychromatic light (480-3400 nm) upregulates sensitivity of tumor cells to lysis by natural killers

Objective: This study evaluates the participation of immunological mechanisms of downregulation of murine hepatoma cells MH22a after direct exposure to polychromatic polarized light. Background data: Previous studies have shown that exposure to a combination of visible (VIS) and infrared (IR) light leads to decreased tumorigenicity of the murine hepatoma cells MH22a, which correlated with an increase in the amount of cells with reorganized cytoskeleton in the submembrane region. The mechanism of tumor inhibition and elimination has not been determined. Materials and methods: Polychromatic light (480-3400 nm) has been used at doses of 4.8 and 9.6 J/cm² to determine the sensitivity of murine MH22a cells and human erythroleukemia cells K562 exposed to this light, to lysis by effector cells of innate immunity (NK cells), and enhancement of the glycocalyx of the studied tumor cells. This was determined using flow cytometry, the H³-uridine cytotoxic test followed by spectrophotometry. Results: VIS-IR light increases the sensitivity of MH-22a cells at a dose 4.8 J/cm² and K562 cells at 9.6 J/cm². The enhancement of sensitivity of tumor cells to NK lysis changed their ability to absorb alcian blue, reflecting a change in the expression of the glycocalyx. Conclusions: Increasing the sensitivity of the murine tumor cells MH22a and human K562 irradiated VIS-IR light correlated with a change in the expression of their glycocalyx. The results of the present study demonstrate that the reduction of tumorigenicity of irradiated tumor cells is due to their sensitivity to lysis by NK cells of the immune system.