Figure 1.

Tumor is a complex heterocellular microenvironment where cancer cells are in constant communications with the stromal cells, the extracellular matrix, and biochemical signaling molecules. Tumor stroma plays a major role in regulating functions of cancer cells and their responses to therapeutic compounds. (Adapted from Joyce JA and Pollard JW, Nat Rev Cancer 2009). (A color version of this figure is available in the online journal.)