Abstract: Abstract: Tumor microenvironment (TME) plays a key role in the development and progression of tumors, such as pro⁃ moting local drug resistance, immune escape, and distal metastasis. According to the TME of different individuals, accurate evaluation and selection of clinical medication can effectively control the malignant transformation of carcinoma in situ and metastatic cancer. At present, the main method to treat cancer is chemotherapy, TME can regulate the reaction of the tumor cells to the standard chemotherapy and target drug therapy, so the combination of the targeted TME therapy and chemothera⁃ py will achieve better clinical efficacy. In this review, we summarized the mechanisms of TME in breast cancer, including ex⁃ tracellular matrix, carcinoma-associated fibroblasts, carcinoma-associated macrophages, regulatory T cells and bone marrow mesenchymal stem cells, which providing a theoretical basis for the development of TME targeted therapy.

Key words: tumor microenvironment, breast cancer, extracellular matrix, carcinoma-associated fibroblasts, carcinoma- associated macrophages, regulatory T cells, bone marrow mesenchymal stem cells