Tumor microenvironment biomarkers in breast cancer

Breast cancer is the most common malignant tumor in women. The tumor structure in breast cancer is characterized not only by morphological heterogeneity of tumor cells, but also by a high degree of heterogeneity of tumor microenvironment, which contains immune cells, cell matrix elements, and other components that may have procarcinogenic or anticarcinogenic effects. Therefore, personalized approaches to selecting the most effective breast cancer treatment protocols cannot be used without comprehensive analysis of the target cancer markers and cellular microenvironment biomarkers. This review is aimed at systematizing the data on tumor microenvironment biomarkers and evaluating the prognostic value of the analysis of tumor microenvironment biomarkers in breast cancer. Biomarkers of the tumor microenvironment are important prognostic factors. Molecular genetic analysis of the profile of these biomarkers, as well as immunohistochemical studies of the mutual arrangement of tumor cells and tumor microenvironment can be used for high-accuracy cancer diagnosis and for the selection of effective personalized therapy in breast cancer. This comprehensive research is necessary because of the plasticity of tumor microenvironment cells, which can either support tumor growth, block immune response, and provide resistance to drugs, or exhibit antitumor activity. The key elements of the tumor microenvironment in breast cancer have been analyzed, and examples of interaction between tumor cells and the microenvironment, as well as data on the prognostic and diagnostic values of tumor microenvironment biomarkers, have been summarized. The tumor microenvironment has been shown to affect the formation of drug resistance and the efficiencies of various breast cancer therapies.