EFFECT OF POLYCHROMATIC VISIBLE LIGHT COMBINED WITH INFRARED RADIATION
ON TUMORIGENICITY OF MURINE HEPATOMA CELLS AND THEIR SENSITIVITY
TO LYTIC ACTIVITY OF NATURAL KILLERS
N.A. Filatova, N.A. Knyazev,1 V.V. Kosheverova, A.N. Shatrova, K.A. Samoilova
Institute of Cytology RAS, St. Petersburg;
1 e-mail: nickolayknz@gmail.com
Tumorigenicity of murine hepatoma cells (MH22a) and their sensitivity to lysis by natural killers (NKs) have been studied after exposure to polychromatic visible and infrared light
(VIS-IR, 480-3400 nm, 40 mW/cm2), similar to the terrestrial solar spectrum without its minor UV component, in order to elucidate the involvement of this important environmental
and physiotherapeutic factor in regulation of the anti-tumor defense system. The MH22 cells were in vitro exposed to VIS-IR light and their sensitivity to lytic activity of NKs was
evaluated. We found that sensitivity of MH22a cells to lysis by NKs after exposure to VIS-IR light at a dose of 4.8 J/cm2 increased 1.5-2 times, while it did not change after
exposure to a dose of 9.6 J/cm2 at all ratios (1 : 5-1 : 50) of the number of NKs (effectors) to that of hepatoma cells (targets). The increase in the sensitivity of hepatoma cells
to NKs was accompanied by structural changes of cell surface: the capability of supra-membraneous glycoproteins (glycocalix) to sorb the vital dye alcian blue (AB) was significantly lower
as compared with the unexposed cells of control group. However, no changes in AB sorption was revealed in hepatoma cells exposed to the light at a dose 9.6 J/cm2.
Tumorigenicity of photo-irradiated MH22a cells has been studied in the in vivo experiments. Light-exposed (4.8 and 9.6 J/cm2) and intact hepatoma cells were transplanted
into syngenic mice C3HA. Tumor volumes 25 days after transplantation proved to be smaller after exposure to the light at both doses than in the control group (4-4.5 times and 2.5-4 times,
respectively), which correlated with the increase in the sensitivity to lisys by NKs and decrease in the AB sorption only after light exposure at dose 4.8 J/cm2. Using the flow
cytometry method we could show that VIS-IR light at the applied doses did not interfere with the distribution of hepatoma cells over the cycle phases and thus deceleration of the tumor
growth was not associated with cytostatic effect of VIS-IR light. To evaluate effect of polychromatic light on the growth of the preformed tumors, the 5-day course of daily light exposures
oftumor bearing mice C3HA was carried out in 10 days after subcutaneous transplantation of 2 • 105 cells of syngene hepatoma when the tumors had developed in 100 %
animals. Like in the case of transplantation of the light-exposed cells, irradiation of the tumor bearing mice at doses 4.8-9.6 J/cm2 resulted in deceleration oftumor growth
(2.1-2.9 and 2.2 times respectively) for 4 weeks as compared with non-irradiated mice.
Key words: visible and infrared radiation, murine hepatoma 22a, natural killer cells, tumorogenity
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