Tumor-infiltrating lymphocytes: opportunities to use their potential in clinical practice in breast cancer

Introduction. Tumor-infiltrating lymphocytes are currently considered as a prognostic biomarker of cancer patient survival and response to therapy, as well as a target for immunotherapy. However, tumor-infiltrating lymphocytes are only part of the tumor microenvironment, which consists of cellular and cytokine components. The cellular component also includes tumor-associated macrophages, neutrophils, fibroblasts and other cells. The cytokine component is represented by the products of the activity of all cells of the microenvironment, as well as tumor cells. The purpose of this review is to consider various subpopulations of tumor-infiltrating lymphocytes, show their interaction with tumor cells and other cell populations of the tumor microenvironment, and also evaluate the possibilities of clinical use of this cell population as a biomarker using the example of breast cancer. Material and research methods. Materials for evaluating the importance of tumor-infiltrating lymphocytes as one of the components of the tumor microenvironment for clinical practice were publications in domestic and foreign journals over the past 5-7 years. Results. This review examines various subpopulations of tumor-infiltrating lymphocytes, shows their interaction with tumor cells and other cell populations of the tumor microenvironment, and also describes the potential for clinical use of this cell population as a biomarker for predicting clinical outcomes and the possibility of their use to determine the most effective treatment for cbreast cancer. Conclusion. Obtaining new data on the previously poorly studied components of the tumor microenvironment and tumor-infiltrating lymphocytes, as well as the formation of ideas about the mutual influence of tumor microenvironment cells and tumor cells open up the prospect of developing innovative models of therapy. One of the modern directions is the search for molecular mechanisms of maintaining the antitumor activity of tumor-infiltrating lymphocytes, as well as the polarization of cells in the tumor microenvironment. Advances in the field of molecular oncology will make it possible to reduce the mortality rate of cancer patients to minimal levels while maintaining or even improving their standard of living.