Immunohistochemical study of uveal melanoma and its cellular microenvironment

Abstract

Introduction. Uveal melanoma pathogenesis is determined by a number of factors, including the tumor molecular genetics, the organism’s immune response, and other ones. One of the approaches to studying the peculiarities of pathogenesis of this cancer is to determine the local subpopulations of lymphocytes and macrophages in combination with the study of the proliferative activity of tumor cells.Objective – to study the immunohistochemical features of uveal melanoma and its cellular microenvironment.Materials and methods. 24 enucleated eyes with uveal melanoma (144 histological and 216 immunohistochemicalpreparations) without previous treatment were analyzed. Cells of the immune microenvironment were analyzed: lymphocyte subpopulations and CD 68+ and CD 163+ antigens expressed by macrophages in the melanoma stroma and 2–3 mm from it. The tumor cell proliferation index Ki-67 was diagnosed.Results. All tissue samples of uveal melanoma revealed the presence of lymphocytes in the microenvironment of tumor cells. A large proportion of the studied subpopulations of lymphocytes were T-cytotoxic CD28+ lymphocytes (absolute content: 607.3 ± 431.2, relative: 18.84 % ± 12.12 %) (p = 0.018). A smaller proportion, but in equal proportions, were T-helpers CD4+, T-cytotoxic CD8+ and CD25+ lymphocytes (p = 0.6). The absolute number of natural killer cells subpopulation CD16+ was lower compared to CD56+ (p = 0.05). However, an almost equal relative content of the studied subpopulations was noted (p = 0.9). Histological examination revealed the presence of uveal melanoma macrophages in the microenvironment of the tissue. The immunohistochemical study of CD68+ and CD163+ antigens expressed by anti-inflammatory and pro-tumor macrophages showed that their absolute and relative content in the uveal melanoma tissue is almost the same with a slight predominance of CD163+ (p = 0.7). Immunohistochemical analysis showed that the nuclei of melanoma cells contain, on average, 575.2 ± 388.5 significant cells of the Ki-67 proliferation protein. This protein was found in 16.69 ± 10.88 % of tumor cells.Conclusion. Immunohistochemical study allows to identify subpopulations of lymphocytes infiltrating the tumor, to determine the subtypes of macrophages and to estimate the Ki-67 index of tumor cell proliferation. The data obtained will make it possible to further evaluate the significance of individual immune cells (in particular, T-cytotoxic CD28+ lymphocytes) in the pathogenesis of uveal melanoma in order to develop targeted effects, substantiate new immunotherapeutic approaches to the treatment of primary tumors and reprogramming altered immune cells.

Keywords

• uveal melanoma
• immunohistochemical study
• lymphocyte subpopulations
• macrophage antigens
• proliferation index