TGFβ receptor inhibition unleashes interferon-β production by tumor-associated macrophages and enhances radiotherapy efficacy
BackgroundTransforming growth factor-beta (TGF{beta}) can limit the efficacy of cancer treatments, including radiotherapy (RT), by inducing an immunosuppressive tumor environment. The association of TGF{beta} with impaired T cell infiltration and antitumor immunity is known, but the mechanisms by which TGF{beta} participates in immune cell exclusion and limits the efficacy of antitumor therapies warrant further investigations. MethodsWe used the clinically relevant TGF{beta} receptor 2 (TGF{beta}R2)-neutralizing antibody MT1 and the small molecule TGF{beta}R1 inhibitor LY3200882 and evaluated their efficacy in combination with RT against murine orthotopic models of head and neck and lung cancer. ResultsWe demonstrated that TGF{beta} pathway inhibition strongly increased the efficacy of RT. TGF{beta}R2 antibody upregulated interferon beta (IFN{beta}) expression in tumor-associated macrophages (TAMs) within the irradiated tumors and favored T cell infiltration at the periphery and within the core of the tumor lesions. We highlighted that both the antitumor efficacy and inhibition of immune exclusion observed with the combination of MT1 and RT were dependent on type I interferon signaling. ConclusionsThese data shed new light on the role of TGF{beta} in limiting the efficacy of RT, identifying a novel mechanism involving the inhibition of macrophage-derived type I interferon production, and fostering the use of TGF{beta}R inhibition in combination with RT in therapeutic strategies for the management of head and neck and lung cancer.