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e15597 Background: Oncolytic virotherapy is developing intensively in modern oncology. Viruses demonstrate the ability to the direct oncolysis and to the stimulation of antitumor immune activity; this experiment was aimed at solving the question of the prevalence of one of them. Glial tumors are the most common brain tumors; oncolytic viruses show certain prospects in their treatment due to the ability to penetrate the blood-brain barrier. The aim of the study was to determine the possible oncolytic effect of new unclassified group K rotaviruses (RVK) on T98G and U87MG glioblastoma cells in vitro. Methods: T98G and U87MG cell cultures were received from Russian banks of cell lines of human and animal tissues. Standard culturing was performed with attenuated apatogenic RVK strains No. 100 and No. 228 at a concentration of 108, 107, 106 and 105 particles/mL. The cytotoxic effect was determined with MTT and Annexin V assays, cell morphology was evaluated by the light-optical method. Results: Both RVK strains demonstrated a dose-dependent cytotoxic activity; the maximal effect was observed in strain No.100 at a dose of 108 particles/mL on U87MG cells (predominantly apoptosis). Studies of cell morphology showed a pronounced effect of RVK on the cell culture: significant degenerative changes in cells, a tendency to a decrease in cluster size, a change in their shape and granularity. Cluster formation in culturing in the serum-free medium is considered in the literature as a property of cancer stem cells responsible in vivo for tumor recurrence and its chemo- and radio-resistance. T98G cells demonstrated morphological changes: nuclear segmentation, diffused cytoplasm, indistinct cell borders with signs of syncytium formation. Conclusions: The established oncolytic effect of RVK strain No. 100 in vitro on glioma cells, presumably with tumor stem cells, indicates a significant potential for the use of these rotaviruses in treatment of glial tumors.

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The purpose was to study antitumor effects of the group K rotaviruses strains No. 228 and No. 100 in the experiment on a model of transplantable murine melanoma. Material and methods. The study included 65 С57Black/6 mice with transplantable B16/F10 melanoma and two strains of the Reoviridae family members characterized as rotaviruses, not belonging to the known groups, with the working title “group K rotaviruses (RVK)”. Animals received RVK in “vaccination” (before tumor transplantation) and “treatment” (after tumor formation) modes. Live and inactivated strains were used. RVK were administered intramuscularly as 0.3 ml of virus-containing culture fluid with at least 5x109 viral particles per 1 ml, with a total of 4 injections. Life span of mice and morphological characteristics of tumors were evaluated. Results. Injections of both strains increased the survival of tumor-bearing mice by 1.7-1.9 times in 4 of 8 experimental groups, compared to controls. The modes of RVK administration showed some differences: the survival was longer in mice with the “vaccination” mode compared to the “treatment” mode. Morphological changes in tumors were similar after application of both modes and inclued dystrophic changes of tumor cells, formation of extensive necrosis areas, and leukocyte infiltration. Discussion. Live and inactivated RVK had unidirectional effects implying its association with immunomodulatory action rather than with a direct lytic effect on the tumor. Conclusions. Both studied strains of rotaviruses in the group K had antitumor effect in the model of transplantable В16/F10 murine melanoma in the «vaccination» mode.

e15272 Background: Significant increase of malignant tumors` incidence all over the world in spite of vast arsenal of anticancer drugs and their combinations challenges the oncologists to develop new approaches to tumor treatment. Application of oncolytic virus is considered to be rather promising. Here we studied two strains of the new group of non-classified rotavirus of Reoviridae family (RVK): 100 and 228 ( http://jbks.ru/archive/issue-10/article-6 ). RVK are attenuated non-pathogenic virus growing on pig embryo kidney cell culture with concentration 5·109 per 1 ml. The aim of the study was to assess the effect of two RVK strains (100 and 228) on the growth of human epidermoid carcinoma A431 transplanted to nude mice in vivo. Methods: Mice Balb/cNude 22-24 g body weight (n = 13) were injected with 4х106 cells of human epidermoid carcinoma A431 subcutaneously in SPF-area of vivarium. After formation of palpable tumors (1 week after transplantation) administration of alive RVK strains 100 and 228 was performed. The 3rd group was the control one and received 0.85% NaCl. The injections were performed once a week 0.3 ml. Tumor growth rate and its` volume were measured. 1 week after the completion of the course mice were sacrificed, tumors were weighted and their morphology was studied. Results: In mice injected with RVK tumor growth inhibition developed in early date after the injection and was statistically significant within 30 - 40 days of monitoring only after the administration of strain 100. In these animals tumor weight was 2.6 times lower than in control mice (6.3±3.0 и 16.6±2.3 g respectively, р < 0.05), in mice having received strain 228 it was 1.7 times less tan in controls. Layers of high-grade sqamous carcinoma cells without keratinization with inflammatory and necrotic foci were observed in tumors of control mice while in tumors inhibited by RVK dystrophic changes and fragmentation, inflammation in places severe and necrotic foci were seen. Implication of the strain 100 resulted in 2-3 time reduction of tumor size, decrease of tumor cells` layers, mononuclear infiltration. Conclusions: In the in vivo model of human epidermoid carcinoma A431 transplanted to nude mice the inhibition of tumor growth under RVK administration was established. Our results confirm the oncolytic activity in RVK, particularly in strain 100.