Immunosuppressive networks in the tumour environment and their therapeutic relevance.

It is well known that many tumours are potentially immunogenic, as corroborated by the presence of tumour-specific immune responses in vivo. Nonetheless, spontaneous clearance of established tumours by endogenous immune mechanisms is rare. Therefore, the focus of most cancer immunotherapies is to supplement essential immunogenic elements to boost tumour-specific immunity. Why then has tumour immunotherapy resulted in a generally poor clinical efficiency? The reason might lie in the increasingly documented fact that tumours develop diverse strategies that escape tumour-specific immunity.