Cellular therapies: Gene editing and next-gen CAR T cells

Abstract

Gene therapy has emerged as a promising method to improve patient care and ideally cure genetic diseases. Gene editing methods have allowed cancer target identification and efficient drug screenings. Cancer cell lines or animal models can be created using a series of genome edits or chromosomal rearrangements. The use of engineered nucleases has greatly facilitated gene editing for research and is showing promise for therapy in many fields. Recent advances in delivery, and increases in activity and specificity will allow clinical gene correction in tumor or susceptible cells. Significant advances have been made using zinc finger nucleases (ZFNs) and TAL effector nucleases (TALENs). Clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-associated proteins (Cas) have similar capabilities, with some additional features including simpler design and cloning, and the capability of targeting multiple loci in the same cell. As cancer develops from multiple genetic and epigenetic changes, CRISPR/Cas systems and other nucleases are showing great promise in cancer modeling and therapy. Adoptive cell therapy using T cells that have been edited to express engineered chimeric antigen receptors (CARs) or T-cell receptors (TCRs) have succeeded in targeting patient tumors. Second and third generation CAR T cells have more modifications, including the addition of costimulatory molecules, and have shown improved results. A number of systems have been used for efficient knockin of the CAR or TCR and in the added gene editing steps, such as knocking out the endogenous TCR. As with therapeutic gene editing, improving delivery and reducing the possibility of off-target events are important criteria for optimizing ZFN, TALEN, and CRISPR/Cas nuclease editing.