A team at Cardiff University in the U.K. has used CRISPR/Cas9 genome editing to generate engineered killer T cells that are up to a thousand times more sensitive to cancer cell antigens than T cells engineered using more conventional approaches, and which allowed far better targeting of T cells to cancer cell lines and patient-derived leukemia cells.
The new approach exploits the genome editing technology to remove the T cells’ endogenous T cell receptors, and simultaneously replace them with cancer antigen-specific TCRs. The researchers, led by Cardiff University School of Medicine’s Professor Andrew Sewell and Dr. Matesuz Legut, hope that the new method will enable the development of far more effective anticancer immunotherapies, and offer up a new experimental system for identifying novel cancer targets.
Traditional approaches to engineering T cells for cancer immunotherapy involve the transduction of cells with a chimeric antigen receptor or a TCR for a specified antigen.
Rather than just adding the new cancer-specific TCRs to T cells, the University of Cardiff researchers instead used CRISPR/Cas9 editing to simultaneously knock out the cells’ endogenous TCR, and replace it with a cancer antigen-specific TCRs. “This approach enhanced the expression of the transduced TCR at the T-cell surface and resulted in TCR transductants that displayed substantially improved antigen sensitivity,” they report.
When tested in the laboratory, the CRISPR-edited and transduced T cells demonstrated far better in vitro and ex vivo reactivity to primary blood cancers, compared with T cells expressing both endogenous and transgenic TCRs. “Transduction with a pan-cancer reactive TCR used in conjunction with CRISPR/Cas9 knockout of the endogenous TCR resulted in more efficient redirection of CD4+ and CD8+ T-cells against a panel of established blood cancers and primary, patient-derived B acute lymphoblastic leukemia blasts compared to standard TCR transfer,” the team states.
“The improvement in the sensitivity of cancer recognition that can be achieved by editing out the existing natural receptor and then replacing it with one that sees cancer cells is remarkable,” professor Sewell adds.
“TCR replacement is preferable to TCR transfer for functional characterizations of TCRs of interest especially where these TCRs compete poorly with endogenous TCRs for surface expression or have a relatively low affinity for cognate antigen.” The system could in addition be used to generate high-throughput, whole genome screens to identify new TCR ligands and potential therapeutic targets.