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In vivo Discovery of Immunotherapy Targets in the Tumor Microenvironment

Zhou,, Penghui, Shaffer, Donald, Alvarez Arias, Diana A., Nakazaki,, Yukoh, Pos, Wouter, Torres, Alexis J., Cremasco, Viviana, Dougan, Stephanie K., Cowley, Glenn S., Elpek, Kutlu, Brogdon, Jennifer, Lamb, John, Ploegh, Hidde L., Root, David E., Love, Christopher, Dranoff, Glenn, Hacohen, Nir, Cantor, Harvey and Wucherpfennig, Kai W. (2014) In vivo Discovery of Immunotherapy Targets in the Tumor Microenvironment. Nature.


Recent work has shown that cytotoxic T cells play a central role in immune-mediated control of cancers, and treatment with monoclonal antibodies that target inhibitory receptors on T cells can result in significant clinical benefit in patients with advanced disease. However, many of the regulatory mechanisms within T cells that result in loss of function within immunosuppressive tumor microenvironments remain unknown. Here we show that regulatory molecules operating within tumor-infiltrating T cells can be systematically discovered in vivo in the tumor microenvironment. We devised a pool shRNA approach aimed at identification of shRNAs that release the functional block within tumor-infiltrating CD8 T cells. We postulated that shRNAs targeting key inhibitory molecules within T cells would enable robust T cell accumulation within tumors, despite multiple inhibitory signals. This hypothesis was tested by infecting tumor-specific T cells with pool shRNA libraries, which were then injected into mice bearing subcutaneous melanomas. After one week, T cells were purified from tumors and lymphoid organs, and the representation of all shRNAs was quantified in different organs by deep sequencing of the shRNA cassette. This approach resulted in the identification of a large number of potential targets for cancer immunotherapy. One of the targets was Ppp2r2d, a regulatory subunit of the PP2A phosphatase. Control shRNA transduced T cells underwent apoptosis upon recognition of melanoma cells, while Ppp2r2d shRNA transduced T cells accumulated in tumors due to enhanced proliferation and resistance to apoptosis. Ppp2r2d transduced T cells also significantly delayed tumor growth. This in vivo approach has wide-spread applications to dissect complex immune functions in relevant tissue microenvironments.

Item Type: Article
Keywords: DDP work, incoming DFCI MTA # 6113. ID has been filed at DFCI. Provisional patent has been filed
Date Deposited: 13 Oct 2015 13:13
Last Modified: 13 Oct 2015 13:13