The tumor microenvironment: adding pieces to the puzzle

In the tumor microenvironment, malignant cells coexist and interact with each other and with stromal, immune, and endothelial cells, as well as with extracellular matrix proteins. The interaction occurs through membrane contact or the production of multiple soluble factors. The composition of tumor and matrix cells changes continuously during tumor development, along with the infiltration of immune cells, forming heterogeneous niches that vary in space and time. We integrate current knowledge about the complex interaction between heterogeneous cell populations in the TME and the impact of these networks in supporting immune defense, which paradoxically promotes tumor progression. We summarize the involvement…