ENGINEERING OF DIFFERENT T-CELL POPULATION FOR EFFECTIVE CAR T-CELL IMMUNOTHERAPY Pooja Bharali (M.Sc in Molecular Medicine), Central University of Punjab ABSTRACT
Background
Chimeric antigen receptor (CAR) T-cell therapy is a novel adoptive cell transfer (ACT) immunotherapy that has emerged as a revolutionary avenue for cancer treatment especially for malign hematological malignancies. The success of CAR T-cell therapy is due to its efficient directed engineering of Tlymphocytes with synthetic receptors known as chimeric antigen receptors (CAR) targeted against cancer cells. The CAR-T cell therapy has shown unparallel clinical efficacy in treatment of hematological malignancies, including acute lymphoblastic leukemia, chronic lymphocytic leukemia, and lymphoma. Drugs such as KYMRIAH (tisagenlecleucel) and Yescarta (axicabtagene ciloleucel) are two most successful drugs developed against relapsed aggressive leukaemias. After efficiently treating leukaemia now the spectrum of ACT has been broadened towards targeting these engineered T-cells against solid tumors. To make ACT a success for treating solid tumors, various pools of T-cell populations are screened to engineer a potent T-cell which could effectively target the solid tumor through its unique receptor binding capability as well as manifesting strong cytolytic activity without causing any toxicity. The hunt for efficient T-cells has led scientist to discover many new unconventional T cells such as Mucosal associated Invariant T cells (MAIT), Natural killer T cells (NK T-cells) and Memory T Stem Cells (TSCM) in targeting solid tumors. Exploiting these unique subpopulations of T-cells will definitely help scientist to achieve the goal of treating hard to kill solid tumors. In this review, recently identified potential cancer targeting Tcells has been elucidated in a concise manner.
In 1993, Israeli Immunologist Zelig Eshhar, had engineered the first chimeric T-cell receptor. These genetically encoded artificial fusion molecules can reprogram the specificity of peripheral blood monoclonal T-cells against a selected cell surface target. The engineered expression of CARs on the surface of T cells enables the redirection of T-cell specificity. The first CAR T-cell was developed against human CD19 to kill leukemia cells in 2003 which later becomes the first FDA approved CAR T-cell called tisagenlecleucel in 2017 against relapsed/refractory acute lymphoblastic leukemia showcasing 80% efficacy in young adults and children. (mkscc.org)
Keywords: CAR T-Cell Therapy, Solid Tumor, MAIT; NK T-cells; TSCM
How T cells are engineered for CAR T-cell therapy?
In CAR T-cell therapy, patients T-cells were isolated from peripheral circulation and CD8+ T cells were sorted using magnetic beads isolation or by using FACS which are further processed and are genetically engineered to express a chimeric antigen receptor. Then these engineered T-cells are expanded in IL-2 and are reintroduced in the patient. Ideal CAR T- cell construct consist of 3 domains: - the ectodomain (single T cell activating domain (scFv) with anti CD19), the transmembrame (CD8) linker molecule and the endodomain (consisting costimulatory molecules such as CD28/4-1BB, CD3 zeta generating response via its 3 immuno receptors of ITAM). Many new modifications are made in the CAR T-cell construct. Till date, 4th generation of CAR T-cells were developed.
Different populations of T cells for CAR T-cell therapy
Memory T stem cells (TSCM) Multipotent, self-renewal T-cells capable of maintenance, proliferation and expansion of CAR T-cells after reintroduction. Half-life of 14 years Human TSCM cells possess high proliferative and long‐term survival abilities in vivo Expresses naïve T‐lymphocyte surface markers,CD45RA+CD45RO−CCR7 +CD62L+ in humans
POOJA BHARALI CENTRAL UNIVERSITY OF PUNJAB Email: poojabharali02@gmail.com Phone:9706572485 Source: Wang et al., 2012
Although its rapid success, the achillea’s heel in CAR T-cell therapy includes On-Target, Off-Tumor Toxicity, low persistence and universal targeting systems. To overcome these challenges, different pool of unique Tcells were identified and are modified according to the needs. MAIT cells overcome the problem of off site cytotoxicity. TSCM stimulated the proliferative capacity and NK T cells are best defined to target and destroy cancer cells effectively.
Future prospect MAIT (Mucosal Associated Invariant T cells) MAIT TCR is raised against MR-1 receptors present in melanoma cells. HLA independent mode of action Target pan cancer pan population No off-target cytotoxicity Works efficiently in multiple cancer cell lines in-vitro.
NATURAL KILLER T-CELLS Succesful in treatment of neuroblastoma. Capable of targeting tumorassociated macrophages (TAM). activated Natural Killer (aNK) are designed to kill cancer cells by the players of innate immunity They are universal rather than personalized in their killing potential
CONTACT
Discussion
These unconventional T cells shows potential to be used in CAR T cell therapy by overcoming HLA independent action Less off target cytotoxicity Pan cancer pan populations directed. Kills multiple hard to kill cancer cells invitro Showcasing high proliferative and persistence capacity with long lived CAR T cells in the patients.
References •Wang, X, Naranjo, A, Brown, CE, Bautista, C, Wong, CW, Chang, WC et al. (2012). Phenotypic and functional attributes of lentivirus-modified CD19-specific human CD8+ central memory T cells manufactured at clinical scale. J Immunother Fesnak A, Lin C, Siegel DL, Maus MV. Transfus Med Rev. 2016;30:139-145. •Genome-wide CRISPR–Cas9 screening reveals ubiquitous T cell cancer targeting via the monomorphic MHC class I-related protein MR1 •Heczey A, et al. Abstract 1301. Presented at: ASGCT Annual Meeting; May 11-15, 2020