A60

It has previously been shown that additional local electromagnetic impact on the tumor en-hances the systemic antitumor effect of low-intensity electromagnetic radiation (EMR) used in the activation therapy regimes designed by Garkavi L.H. et al. (1990–2008). At the same time the question of the influence of weak EMR, applied to the peritumoral area, on the tumor development has not been studied. The aim of the study was to investigate the changes in the tumor caused by low-intensity microwave electromagnetic radiation of bioeffective frequency that acted on the head and peritumoral zone. Materials and methods: The effects of resonance radiation (RR) with frequency corresponding to that of one of the water-containing medium radiations – 1 GHz (“SPE-effect”) – were studied on 53 adult male outbred white rats with transplantable sarcoma 45. Special anticancer agents were not used. The power flux density of RR was less than 1 μW/cm2, surface area of the emitter – 4 cm2, 3–10 min. exposure depending on algorithms of the activation therapy. RR exposure in different groups of animals was localized to the head only, or to the peri-tumoral area only, or successively to the head and peritumoral area (“double” exposure). The course lasted for 4 weeks. The exposure effect was assessed according to the dynamics of the tumor size and results of the light and electron microscopy analysis of tumor changes (JEOL JEM-1011, Japan). Results: The effect of RR in different groups of animals depended on the exposure localization. Central systemic exposure was decisive. The group receiving RR localized to the head showed regression of the tumor or inhibition of its growth in 60% of animals – almost complete tumor regression in 10% and tumor growth inhibition by 70% in the rest cases. RR to the peritumoral area did not show significant influence on the tumor development, while it increased antitumor effect of the central exposure (p < 0.01–0.05). Antitumor effect was registered in 77% of the animals receiving the “double” RR exposure: 30% – morphologically verified complete regression, 24% – partial regression (tumor shrinkage by 2–2.5 times) and tumor growth inhibition by 40% was detected in 23% of animals. Regressing tumor, unlike sarcoma 45 with an active growth, was characterized by significant thickening of the capsule (by 7 times, p < 0.01) and increased intensity of lymphoplasmacytic infiltration (p < 0.01). Immune system cells were present in the capsule, subcapsular zone and as leukocytic barrier in peritumoral area of the conjunctive tissue of up to 170 μm width. Different numbers of lymphocytes and plasma cells were noted in tumor cells. Macrophages were found. Migrating lymphocytes were often noted in the vessels among tumor cells. Electron microscopy showed multiple contacts of lymphocytes with the surface of tumor cells through cytoplasmic excrescences. Such lymphocytes had distinct signs of activation. Simultaneous contacts of lymphocytes and macrophages among themselves and with tumor cells were found. Analysis of ultrastructural characteristics of cells in regressing tumors and detection of collagen in intercellular spaces during histochemical examination of tumor tissues showed the increase in the degree of differentiation of some sarcoma 45 cells. Conclusion: Possibility to increase the systemic antitumor effect of the low-intensity microwave radiation with an additional weak exposure on the peritumoral area was demonstrated for the first time. Damaging effect of RR on tumor was mediated by the changes in composition and activity of elements of the tumor’s immune microenvironment and by the increase in the degree of differentiation of some tumor cells, probably under the influence of bioactive factors of leukocytic origin