Overcoming TGFβ-mediated immune evasion in cancer

Abstract

This Review discusses the context-dependent functions of transforming growth factor-beta (TGF beta) with regard to the composition and behaviour of different cell populations in the tumour immune microenvironment, as well as emerging data that demonstrate that TGF beta inhibition can restore cancer immunity. Transforming growth factor-beta (TGF beta) signalling controls multiple cell fate decisions during development and tissue homeostasis; hence, dysregulation of this pathway can drive several diseases, including cancer. Here we discuss the influence that TGF beta exerts on the composition and behaviour of different cell populations present in the tumour immune microenvironment, and the context-dependent functions of this cytokine in suppressing or promoting cancer. During homeostasis, TGF beta controls inflammatory responses triggered by exposure to the outside milieu in barrier tissues. Lack of TGF beta exacerbates inflammation, leading to tissue damage and cellular transformation. In contrast, as tumours progress, they leverage TGF beta to drive an unrestrained wound-healing programme in cancer-associated fibroblasts, as well as to suppress the adaptive immune system and the innate immune system. In consonance with this key role in reprogramming the tumour microenvironment, emerging data demonstrate that TGF beta-inhibitory therapies can restore cancer immunity. Indeed, this approach can synergize with other immunotherapies - including immune checkpoint blockade - to unleash robust antitumour immune responses in preclinical cancer models. Despite initial challenges in clinical translation, these findings have sparked the development of multiple therapeutic strategies that inhibit the TGF beta pathway, many of which are currently in clinical evaluation.