FIGURE 1.

A schematic overview of tumor microenvironments. Tumor microenvironment refers to the local biological environment where tumor cells exist, and are composed of tumor cells, stromal cells and immune cells. TME is involved in the initiation and maintenance of non-cell autonomous resistance by a variety of mechanisms, including hypoxia, low PH, shifts and polarizations in the immune cell population, vascular abnormalities and diverse stroma cells-derived secretomes, exosomes, soluble factors. TME serves as safeguard to tumor cells by providing mechanical support or secreting different cytokines to evade treatment. Treg, regulatory T lymphocytes; MSC, mesenchymal stem cells; T, T lymphocytes; B, B lymphocytes; DC, dendritic cells; N, neutrophils; M, macrophages; NK, natural killer cells; E, epithelial cells; F, fibroblasts; CAA, cancer-associated adipocytes; L, lymphatic endothelial cells; TEC, tumor endothelial cells; CSC, cancer stem cells; TAM, tumor-associated macrophages; CAF, cancer-associated fibroblasts; MDSC, myeloid-derived suppressor cells; EMT, epithelial-mesenchymal transition. The figure was created with BioRender.com.