Using CRISPR to enhance T cell effector function for therapeutic applications

Abstract

T cells are critical to fight pathogenic microbes and combat malignantly transformed cells in the fight against cancer. To exert their effector function, T cells produce effector molecules, such as the pro-inflammatory cytokines IFN-γ, TNF-α and IL-2. Tumors possess many inhibitory mechanisms that dampen T cell effector function, limiting the secretion of cytotoxic molecules. As a result, the control and elimination of tumors is impaired. Through recent advances in genomic editing, T cells can now be successfully modified via CRISPR/Cas9 technology. For instance, engaging (post-)transcriptional mechanisms to enhance T cell cytokine production, the retargeting of T cell antigen specificity or rendering T cells refractive to inhibitory receptor signaling can augment T cell effector function. Therefore, CRISPR/Cas9-mediated genome editing might provide novel strategies for cancer immunotherapy. Recently, the first-in-patient clinical trial was successfully performed with CRISPR/Cas9-modified human T cell therapy. In this review, a brief overview of currently available techniques is provided, and recent advances in T cell genomic engineering for the enhancement of T cell effector function for therapeutic purposes are discussed.

Exploiting HIV‐1 tropism to target CD4+ T cells for CRISPR

“…The employment of T cells with transgenic T‐cell receptors (TCRs) or chimeric antigen receptors (CARs) specific to tumor antigens in combination with CRISPR‐mediated genome editing is particularly promising. This has resulted in stabilized transgene expression, enhanced T‐cell effector function and/or increased efficacy in murine models of both blood cancers and solid tumors 4 . Nonetheless, the generation of T cells with both knockouts and knock‐ins is a laborious process.…”

“…Therefore, many groups have tried to enhance T‐cell effector function by making use of CRISPR/Cas9‐mediated genome editing in order to maximize T‐cell killing potential. Ranging from direct augmentation of cytokine production by modulating TCR or costimulatory signaling to fine‐tuning post‐transcriptional regulation, or by simply knocking out inhibitory receptors such as PD‐1, 4 many of these approaches utilize a two‐step process and required sequential genome editing and introduction of tumor antigen‐specific CARs or TCRs. Instead, the novel method from the Doudna laboratory is able to do both simultaneously 5 .…”

“…The VLP‐mediated delivery of both the Cas9 machinery and transgene of interest could have significantly streamlined and optimized the production of the therapeutic T‐cell product. Lastly, by targeting β2 microglobulin and/or T‐cell receptor alpha chain (TRAC), as exemplified by Hamilton et al ., 5 VLPs could also be used to produce “off‐the‐shelf” (CAR) T‐cell products for adoptive therapy 4 …”

“…CRISPR-mediated genome editing has been garnering interest in cancer therapy, particularly as a tool to generate "off-the-shelf" T-cell products that do not express major histocompatibility complex molecules, or to render T cells refractory to inhibitory signaling. 4 The employment of T cells with transgenic T-cell receptors (TCRs) or chimeric antigen receptors (CARs) specific to tumor antigens in combination with CRISPR-mediated genome editing is particularly promising. This has resulted in stabilized transgene expression, enhanced T-cell effector function and/or increased efficacy in murine models of both blood cancers and solid tumors.…”

“…This has resulted in stabilized transgene expression, enhanced T-cell effector function and/or increased efficacy in murine models of both blood cancers and solid tumors. 4 Nonetheless, the generation of T cells with both knockouts and knock-ins is a laborious process. Furthermore, for targeting specific T-cell subsets, enrichment or cell sorting is required prior to genetic engineering.…”