Immunotherapy Targets in Tumors
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ABSTRACT: Recent work has shown that cytotoxic T cells play a central role in immune-mediated control of cancers1-3, and monoclonal antibodies that target inhibitory receptors on T cells can induce significant clinical benefit in patients despite advanced disease4-6. However, many of the regulatory pathways that result in loss of T cell function within immunosuppressive tumors remain unknown. Here we show that such regulatory mechanisms can be systematically discovered in vivo in the tumor microenvironment. We devised a pool shRNA screening approach aimed at identifying genes that block the function of tumor-infiltrating CD8 T cells. We postulated that shRNAs targeting key inhibitors would enable robust T cell infiltration and proliferation in tumors, despite multiple inhibitory signals. Candidate shRNAs were discovered by transfer of shRNA-transduced T cells into tumor-bearing mice, followed by deep sequencing to quantify the representation of all hairpins in tumors and lymphoid organs. A subset of shRNAs induced T cell accumulation in tumors but not the spleen, demonstrating feasibility of discovering shRNAs with differential action across tissues. One of the targets was Ppp2r2d, a regulatory subunit of the family of PP2A phosphatases7. 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 reduced apoptosis. Ppp2r2d shRNAexpressing T cells also significantly delayed tumor growth. This in vivo approach has wide applications to dissect complex immune functions in relevant tissue microenvironments.
ORGANISM(S): Mus musculus
PROVIDER: GSE53388 | GEO | 2014/03/14
SECONDARY ACCESSION(S): PRJNA231899
REPOSITORIES: GEO
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