PD-1 therapy elevates Treg/Th balance and increases tumor cell pSmad3 that are both targeted by [alpha]-TGF[beta] antibody to promote durable rejection and immunity in squamous cell carcinomas

• Published in: Journal for immunotherapy of cancer 2019-03, Vol.7 (1)
• Main Authors: Dodagatta-Marri, E, Meyer, D. S, Reeves, M. Q, Paniagua, R, To, M. D, Binnewies, M, Broz, M. L, Mori, H, Wu, D, Adoumie, M, Del Rosario, R, Li, O, Buchmann, T, Liang, B, Malato, J, Arce Vargus, F, Sheppard, D, Hann, B. C, Mirza, A, Quezada, S. A, Rosenblum, M. D, Krummel, M. F, Balmain, A, Akhurst, R. J
• Format: Article
• Language: English
• Subjects: Anopheles; Antibodies; Antigens; Cancer; Cancer metastasis; Cancer treatment; Carcinoma; Care and treatment; Clinical trials; Gene expression; Gene mutation; Genes; Health aspects; Immunotherapy; Laboratory rats; Macrophages; Squamous cell carcinoma; Stem cells; T cells; Transforming growth factors; Tumors
• ISSN: 2051-1426; 2051-1426
• DOI: 10.1186/s40425-018-0493-9

Background Checkpoint blockade immunotherapy has improved metastatic cancer patient survival, but response rates remain low. There is an unmet need to identify mechanisms and tools to circumvent resistance. In human patients, responses to checkpoint blockade therapy correlate with tumor mutation load, and intrinsic resistance associates with pre-treatment signatures of epithelial mesenchymal transition (EMT), immunosuppression, macrophage chemotaxis and TGF[beta] signaling. Methods To facilitate studies on mechanisms of squamous cell carcinoma (SCC) evasion of checkpoint blockade immunotherapy, we sought to develop a novel panel of murine syngeneic SCC lines reflecting the heterogeneity of human cancer and its responses to immunotherapy. We characterized six Kras-driven cutaneous SCC lines with a range of mutation loads. Following implantation into syngeneic FVB mice, we examined multiple tumor responses to [alpha]-PD-1, [alpha]-TGF[beta] or combinatorial therapy, including tumor growth rate and regression, tumor immune cell composition, acquired tumor immunity, and the role of cytotoxic T cells and Tregs in immunotherapy responses. Results We show that [alpha]-PD-1 therapy is ineffective in establishing complete regression (CR) of tumors in all six SCC lines, but causes partial tumor growth inhibition of two lines with the highest mutations loads, CCK168 and CCK169. [alpha]-TGF[beta] monotherapy results in 20% CR and 10% CR of established CCK168 and CCK169 tumors respectively, together with acquisition of long-term anti-tumor immunity. [alpha]-PD-1 synergizes with [alpha]-TGF[beta], increasing CR rates to 60% (CCK168) and 20% (CCK169). [alpha]-PD-1 therapy enhances CD4 + Treg/CD4 + Th ratios and increases tumor cell pSmad3 expression in CCK168 SCCs, whereas [alpha]-TGF[beta] antibody administration attenuates these effects. We show that [alpha]-TGF[beta] acts in part through suppressing immunosuppressive Tregs induced by [alpha]-PD-1, that limit the anti-tumor activity of [alpha]-PD-1 monotherapy. Additionally, in vitro and in vivo, [alpha]-TGF[beta] acts directly on the tumor cell to attenuate EMT, to activate a program of gene expression that stimulates immuno-surveillance, including up regulation of genes encoding the tumor cell antigen presentation machinery. Conclusions We show that [alpha]-PD-1 not only initiates a tumor rejection program, but can induce a competing TGF[beta]-driven immuno-suppressive program. We identify new opportunities for [alph