Figure 1. Tripartite interaction within tumour ecosystem.

Tumour cell behaviour is strongly influenced by the dynamic interactions between the cancer cells themselves, the cells of the immune system, and the tumour stroma—a broad category containing the extracellular matrix (ECM), stromal cells, and intracellular signalling species. The cancer cells, through aberrant signalling and uncontrolled growth, produce a unique microenvironment which results in differential behaviours on the part of both immune and stromal cells. Stromal cells act to reshape the microenvironment in favour of continued tumour progression and express growth factors and inflammatory cytokines. Additionally, cancer cells engage the ECM physically and reshape the ECM mechanically and enzymatically through MMPs and other ECM-remodelling enzymes. Through signalling interactions with immune cells the tumour is able to suppress the anti-cancer immune response and induce the immune cells to secrete pro-inflammatory factors, as well as growth and survival signals which aid tumour progression.