CAR-T-Cell-Based Cancer Immunotherapies: Potentials, Limitations, and Future Prospects

Abstract

Cancer encompasses various elements occurring at the cellular and genetic levels, necessitating an immunotherapy capable of efficiently addressing both aspects. T cells can combat cancer cells by specifically recognizing antigens on them. This innate capability of T cells has been used to develop cellular immunotherapies, but most of them can only target antigens through major histocompatibility complexes (MHCs). New gene-editing techniques such as clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (CRISPR-cas9) can precisely edit the DNA sequences. CRISPR-cas9 has made it possible to generate genetically engineered chimeric antigen receptors (CARs) that can overcome the problems associated with old immunotherapies. In chimeric antigen receptor T (CAR-T) cell therapy, the patient's T cells are isolated and genetically modified to exhibit synthetic CAR(s). CAR-T cell treatment has shown remarkably positive clinical outcomes in cancers of various types. Nevertheless, there are various challenges that reduce CAR-T effectiveness in solid tumors. It is required to address these challenges in order to make CAR-T cell therapy a better and safer option. Combining CAR-T treatment with other immunotherapies that target multiple antigens has shown positive outcomes. Moreover, recently generated Boolean logic-gated advanced CARs along with artificial intelligence has expanded its potential to treat solid tumors in addition to blood cancers. This review aims to describe the structure, types, and various methods used to develop CAR-T cells. The clinical applications of CAR-T cells in hematological malignancies and solid tumours have been described in detail. In addition, this discussion has addressed the limitations associated with CAR-T cells, explored potential strategies to mitigate CAR-T-related toxicities, and delved into future perspectives.

Keywords: Boolean-gated CARs; CAR-T therapy; CRISPR-Cas9; artificial intelligence.

Figure 1

CAR-T cell therapy. T cells are taken from a patient, engineered to target cancer with a CAR gene, and then multiplied. These CAR-T cells are returned to the patient to target and combat cancer cells.

Figure 2

Generations of CAR-T cells. CM, co-stimulatory molecule. IL, interleukin. CAR, chimeric antigen receptor. The figure shows the evolution of CAR-T cells over five successive generations. First-generation CARs exclusively have CD3ζ-derived signaling modules. Second-generation CARs include a CD3ζ-derived signaling module and a co-stimulatory domain. Third-generation CARs have a CD3ζ-derived signaling module and two co-stimulatory domains. Fourth-generation CARs have a CD3ζ-derived signaling module, a co-stimulatory domain, and IL-12 production module. Fifth-generation CAR-T cells are made up of CD3ζ-derived signaling module, a co-stimulatory domain, and IL 2Rβ production module that is also involved in JAK-STAT pathway.

Figure 3

Major steps in manufacturing and infusion of CAR-T cells. CAR-T cells are isolated from an autologous or allogenic donor. CAR-T cells are activated and genetically engineered to express the CAR genes. These modified CAR-T cells are grown in bioreactors and culture bags. CAR-T cells are stored at extremely low temperatures following quality control and characterization. Chemotherapy is used to decrease or eliminate lymphocytes in selected patients, and CAR-T cells are then delivered into their bloodstream.