A novel genetic screen to identify genes that enhance T cell trafficking into solid tumors

Abstract

Abstract T cell mediated cancer immunotherapies, including anti-PD-1 and CAR-T, are becoming standard of care for a variety of cancer types. However, patients with tumors that lack T cell infiltration generally do not respond well to immunotherapy. One potential strategy to overcome immunotherapy resistance is to enhance the ability of T cells to traffic into the tumor. The objective of this study was to develop an in vivo genetic screen in endogenous T cells using the Sleeping Beauty (SB) mutagenesis system to identify candidate genes that drive intratumoral T cell accumulation. Mutations in one candidate gene, Aak1, were identified in intratumoral T cells of multiple tumor models, including those treated with anti-PD-1. Insertions were highly clustered, suggesting that a gain-of-function Aak1 mutation may be favorable for driving T cells into the tumor. This gain-of-function is likely dominant-negative, as inhibition of Aak1 kinase activity enhanced intratumoral T cell infiltration. Surprisingly, inhibition of Aak1 kinase activity also abolished the therapeutic effect of anti-PD-1 in mouse models of lymphoma and melanoma. Our data demonstrates that our SB mutagenesis approach can be used to identify target genes that could be therapeutically modified to enhance T cell infiltration into tumors. Our innovative method can be adapted to other immune cell types. At least one candidate gene we identified (Aak1) deserves further evaluation as a potential therapeutic target, though a better understanding of the antagonistic relationship between anti-PD-1 action and Aak1 kinase activity is needed. Immediate next steps also include assessing the impact of candidate gene modification in CAR-T cells on their ability to traffic into solid tumors.