Pharmacological inhibition of TGFβ as a strategy to augment the antitumor immune response.

There is considerable evidence suggesting that a variety of malignancies utilize the TGFβ cytokine to evade immune surveillance mechanisms to facilitate tumor growth and metastatic progression. The recently developed large- and small-molecule TGFβ inhibitors have demonstrated antitumor efficacy in several preclinical tumor models. Further investigation has revealed these agents to be critically dependent upon the host's immune system, suggesting that the inhibition of TGFβ may overcome the immunosuppressive tumor microenvironment and, ultimately, augment the antitumor immune response. These findings strongly support combining this strategy with other immunotherapeutic approaches for the treatment of metastatic cancer. This review discusses the immunoregulatory and antitumor properties of these pharmacological inhibitors of TGFβ signaling as either independent agents or in combination with various immunotherapeutic strategies, their potential side effects, as well as additional avenues of research that may be necessary for their eventual clinical application.