The tumour microenvironment and implications for cancer immunotherapy.

Tumour cells exist in a complex milieu of cellular and non-cellular components comprising fibroblasts, endothelial cells, immune cells and metabolites of cellular respiration. An elaborate interplay between these components and tumour cells exists with implications for immunological recognition of tumour cells. Tumours have been shown to alter their antigen and cytokine profiles, desensitise and impair immune defences, signal fibroblasts to facilitate metastasis, and take advantage of acidic and hypoxic conditions that impede normal cells. This paper aims to review the roles of the stroma, extracellular matrix and chemistry of the microenvironment on tumour growth, with particular emphasis on interactions with the immune system, and to highlight some of the novel therapeutic strategies that target the tumour microenvironment.