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Systematic identification of immunotherapy targets using genome-scale in vivo CRISPR screens in CD8+ cytotoxic T cells [scRNA-Seq]

ABSTRACT: CD8+ cytotoxic T cells play essential roles in anti-tumor immune responses. Here, we performed in vivo screens in CD8+ T cells and identified regulators of tumor infiltration and killing, which are directly relevant to cancer immunotherapy. Unlike in vitro screens, the in vivo screen robustly re-identified canonical immunotherapy targets such as PD-1 and Tim-3, along with genes that have not been characterized in T cells. The infiltration and degranulation screens converged on an RNA helicase Dhx37. Dhx37 knockout enhanced the efficacy of antigen-specific CD8+ T cells against cancer in vivo. Immunological characterization in mouse and human CD8+ T cells revealed that DHX37 suppresses effector function, cytokine production, and T cell activation. Transcriptomic profiling and biochemical interrogation revealed a role for DHX37 in modulating the NF-kB pathway. These data demonstrated the power of high-throughput in vivo genetic screens for immunotherapy target discovery, and uncovered DHX37 as a functional regulator of CD8+ T cells.

ORGANISM(S): Mus musculus

PROVIDER: GSE132959 | GEO | 2019/08/22

REPOSITORIES: GEO

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Project description:Exhaustion markers are expressed by T lymphocytes in Follicular Lymphoma (FL). Through these, TIM-3 has been recently identified as a poor pronostic factor when expressed by FL CD4+ T cells. Before this study, there was no molecular characterization of unstimulated CD8+ T cells, expressing - or not - TIM-3. We used microarrays to compare the global gene expression profile between CD8+TIM-3+ T cells and CD8+TIM-3- T cells freshly sorted from follicular lymphoma biopsies. Abstract from the associated publication: Up-regulation of T-cell immunoglobulin-3 (TIM-3) has been associated with negative regulation of the immune response in chronic infection and cancer, including lymphoma. Here, we investigated the possible correlation between TIM-3 expression by ex vivo cytotoxic T cells (CTL) from follicular lymphoma (FL) biopsies and their functional unresponsiveness that could limit the favorable impact of CTL on disease progression. We report a high percentage of CD8+TIM-3+ T cells in lymph nodes of FL patients. When compared to their CD8+TIM-3- counterparts, CD8+TIM-3+ T cells exhibited defective cytokine production following TCR engagement. Furthermore CD8+TIM-3+ T cells display ex vivo markers of lytic granule release and remain unresponsive to further TCR-induced activation of the lytic machinery. Although confocal microscopy showed that TIM-3 expression on CD8+ T cells correlated with minor alterations of immunological synapse, a selective reduction of ERK signaling in CD8+TIM-3+ T cells was observed by phospho-flow analysis. Finally, short relapse free survival despite rituximab(R)-chemotherapy was observed in patients with high content of TIM-3+ cells and a poor infiltrate of granzyme B+ T cells in FL lymph nodes. Together, our data indicate that, besides selective TCR early signaling defects, TIM-3 expression correlates with unresponsiveness of ex vivo CD8+ T cells in FL. They show that scores based on the combination of exhaustion and cytolytic markers in FL microenvironment might be instrumental to identify patients at early risk of relapses following R-chemotherapy.

Project description:Natural killer (NK) cells are an innate immune cell type that serves at the first level of defense against pathogens and cancer. NK cells have clinical potential; However, multiple current limitations exist that naturally hinder the successful implementation of NK cell therapy against cancer, including their effector function, persistence, and tumor infiltration. To unbiasedly identify genes underlying critical NK cell characteristics against cancer, we perform functional mapping of tumor infiltrating NK (TINK) cells by both in vivo AAV-CRISPR screens and single-cell sequencing. We establish a strategy with AAV-SleepingBeauty(SB)-CRISPR screening leveraging a focused high-density sgRNA library, and perform four independent in vivo tumor infiltration screens of primary NK cells in mouse models of melanoma, breast cancer, pancreatic cancer, and glioblastoma. In parallel, we characterize single-cell transcriptomic landscapes of tumor-infiltrating NK cells, which identifies previously unexplored sub-populations of NK cells with distinct expression profiles, a shift from immature to mature NK (mNK) cells in the tumor microenvironment (TME), and decreased expression of mature marker genes in mNK cells. CALHM2, a calcium homeostasis modulator previously not linked to NK function, emerges as a convergent hit from both CRISPR screen and single-cell data. CALHM2 knockout NK cells show enhancement of in vitro cytotoxicity and in vivo tumor infiltration in both mouse primary NK and human chimeric antigen receptor (CAR)-NK cells. Re-introduction of CALHM2 mRNA reverses CALHM2 knockout phenotype of NK cytotoxicity and degranulation. Importantly, in a solid tumor model that is completely resistant to adoptive cell therapy of unmodified CAR-NK cells, CALHM2 knockout CAR-NK cells show potent in vivo anti-tumor efficacy. Human primary NK cell study with multiple donors reveals that CALHM2 knockout enhances cytotoxicity, degranulation and cytokine production of NK cells. Transcriptomics profiling of human primary NK cells reveal multiple enriched pathways of downstream genes upon CALHM2 knockout in both baseline and stimulated conditions. These data identify endogenous cellular genetic checkpoints that naturally limit NK cell function, and pinpoint CALHM2 as a key factor in which genetic modification can be engineered to enhance NK cell-based immunotherapies.

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Systematic identification of immunotherapy targets using genome-scale in vivo CRISPR screens in CD8+ cytotoxic T cells [scRNA-Seq]

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