Beyond the Antigen Receptor: Editing the Genome of T-Cells for Cancer Adoptive Cellular Therapies

Abstract

Recent early stage clinical trials evaluating the adoptive transfer of patient CD8+ T-cells re-directed with antigen receptors recognizing tumors have shown very encouraging results. These reports provide strong support for further development of the therapeutic concept as a curative cancer treatment. In this respect combining the adoptive transfer of tumor-specific T-cells with therapies that increase their anti-tumor capacity is viewed as a promising strategy to improve treatment outcome. The ex vivo genetic engineering step that underlies T-cell re-direction offers a unique angle to combine antigen receptor delivery with the targeting of cell-intrinsic pathways that restrict T-cell effector functions. Recent progress in genome editing technologies such as protein- and RNA-guided endonucleases raise the possibility of disrupting gene expression in T-cells in order to enhance effector functions or to bypass tumor immune suppression. This approach would avoid the systemic administration of compounds that disrupt immune homeostasis, potentially avoiding autoimmune adverse effects, and could improve the efficacy of T-cell based adoptive therapies.

CRISPR-Cas9-mediated disruption of PD-1 on human T cells for adoptive cellular therapies of EBV positive gastric cancer

“…In this way, systemic administration of compounds that disrupt immune homeostasis could be avoided. 22 The CRISPRCas9 system confers targeted gene editing through use of small guide RNAs that lead the Cas9 nuclease to the target site through base pairing. This new method has been demonstrated as an easy-to-handle, yet highly specific and efficient approach for engineering eukaryotic genomes.…”

Synthetic biology in cellular immunotherapy

“…Transcription activator-like effector nucleases (TALENs) are derived from the DNAbinding domain of TAL effectors, bacterial proteins whose base specificity can be altered by changing two specific amino acids [95]. An array of these proteins can be generated to target a desired sequence and then fused to the catalytic domain of the Fok1 nuclease to confer the ability to cut the target sequence.…”

Synthetic biology in cell-based cancer immunotherapy

“…Genome editing for targeted disruption of genes, such as HLAs or inhibitory receptors [95, 96], can render T cells safer and more powerful for adoptive immunotherapy. Several genome editing systems are available that rely on the same underlying mechanism: a nuclease targets a sequence and creates a double stranded break.…”

“…Several genome editing systems are available that rely on the same underlying mechanism: a nuclease targets a sequence and creates a double stranded break. The break is then repaired using either the error-prone non-homologous end joining (NHEJ) or homology directed repair (HDR), which will disrupt expression of the gene [95]. To contend with the potential of off-target cutting [97, 98], tools have been developed to predict off-target cleavage for several of these systems [99, 100].…”