ASSESSMENT OF THE EXPRESSION OF MMР-2, MMР-9 AND FIBRONECTIN MARKERS AS PROGRESSION PREDICTORS IN THE PRIMARY TUMOR TISSUE OF LOCALIZED AND GENERALIZED FORMS OF EWING’S SARCOMA IN CHILDREN AND ADOLESCENTS

Despite processes of epithelial-mesenchymal transition (EMT) that underlie the development of malignant tumors are described widely, the mesenchymal-epithelial transition (MET), which in its turn promotes the metastasis of various tumors, including Ewing's sarcoma (ES), had been studied very little as yet. Within the framework of pediatric oncopathology, ES is one of the most aggressive and metastatic tumors of bones and soft tissues. The purpose of this research was to analyze the features of the expression of markers of the metastatic phenotype of tumor cells MMP2, MMP9 and FN1 in the tissue of the primary tumor in children and adolescents with various forms of ES prevalence. Materials and methods used: 67 patients with localized (n=26) and generalized (n=41) forms of ES aged 0 to 18 y/o, who have been treated at the Pediatric Oncology Department of the National Medical Research Center for Oncology of the Ministry of Healthcare of Russia (Rostov-on-Don, Russia) in Jan. 2009-Dec. 2019. MMP2, MMP9 and FN1 markers were studied by immunohistochemical method in the primary tumor tissue obtained at the stage of process verification and radical surgical treatment after multi-course polychemotherapy (PCT). Results: MMP2 expression in groups with localized and generalized ES before treatment was 4 (p=0.018) and 4.4 (p=0.001) times higher compared to those after treatment. MMP9 expression in the group with generalized ES before treatment prevailed 1.5 times (p=0.020) in comparison with the group after treatment. The median FN1 expression, on the contrary, was 1.2 times lower in the group with generalized ES before treatment than after (p=0.799). Conclusions: determining the expression level of the MMP2 marker in the primary tumor of ES patients can be used to predict the course of the disease and to evaluate the effect of treatment. Whilst markers MMP9 and FN1 require further expanded research.