The tumor microenvironment contributes to every aspect of carcinogenesis and therefore offers promising
targets for cancer therapy. Compared to chemotherapy alone, targeting tumor cells as well as key components of the
tumor microenvironment significantly improve the clinical outcomes of patients. A better understanding of the interaction
between tumor cells and the microenvironment could provide new therapeutic options and accelerate the development of
novel anti-cancer drugs. In this review, we first defined the tumor microenvironment and then discussed the role of the
tumor microenvironment in the initiation and progression of cancer focusing on three major pathways in a tumor cell life
cycle: 1) growth and intravasation; in this section, the epithelial-mesenchymal transition (EMT), tumor cell migration, and
tumor angiogenesis are reviewed. 2) dissemination; the activation and aggregation of platelets, as an important feature for
the survival of tumor cells in the circulation, are reviewed under this section. 3) arrest, extravasation and growth at the
secondary sites; the main contents of this section include tissue tropism in metastasis, the formation of the pre-metastatic
niche, tumor cell adhesion and extravasation, the mesenchymal to epithelial transition (MET), and the formation of
micrometastases and macrometastases. Finally, we briefly introduce the drug resistance mediated by the tumor
microenvironment, and also summarize potential drug targets based on the current knowledge of the tumor
microenvironment. Although the tumor microenvironment is equally important in the progression of carcinomas,
leukemias, and sarcomas, in this review we focus on the common form of malignancy, carcinomas, which represent the
malignancy derived from the epithelia.
Cancer therapy, carcinogenesis, drug resistance, inflammation, metastasis, microenvironment.
Clinical Medicine Research Center of Affiliated Hospital, Inner Mongolia Medical University, No.1 Tongdao North Street, 010050, Hohhot, Inner Mongolia, China.