Throughout the entire process of cancer aetiology, progression and metastasis, the microenvironment of the local host tissue can be an active participant. Invasion occurs within a tumour–host microecology, where stroma and tumour cells exchange enzymes and cytokines that modify the local extracellular matrix, stimulate migration, and promote proliferation and survival. A new class of cancer therapies that targets this pathological communication interface between tumour cells and host cells is currently under development.