CAR-T Cells with Phytohemagglutinin (PHA) Provide Anti-Cancer Capacity with Better Proliferation, Rejuvenated Effector Memory, and Reduced Exhausted T Cell Frequencies

Abstract

ABSTRACTThe development of genetic modification techniques has led to the opening of a new era in cancer treatments that have been limited to conventional treatments such as chemotherapy. Since not only cancerous cells but also healthy cells are damaged by the drugs, intensive efforts are made to develop cancer-targeted techniques. The most promising approach is genetically modified CAR-T cell therapy. The high central memory T cell (Tcm) and stem cell-like memory T cell (Tscm) ratios in the CAR-T cell population increase the effectiveness of immunotherapy. Therefore, it is important to increase the populations of CAR-expressing Tcm and Tscm cells to ensure that CAR-T cells remain long-term and have cytotoxic (anti-tumor) efficacy. In this study, we aimed to improve CAR-T cell therapy’s time-dependent efficacy and stability, increasing the survival time and reducing the probability of cancer cell growth. To increase the subpopulation of Tcm and Tscm in CAR-T cells, we investigated to produce a long-term stable and cytotoxic efficient CAR-T cell by modifications in the cell activation-dependent production method using Phytohemagglutinin. Phytohemagglutinin (PHA), a lectin that binds to the membranes of T cells and increases metabolic activity and cell division, is studied to increase the Tcm and Tscm population. Although it is known that PHA significantly increases Tcm cells, B-lymphocyte antigen CD19 specific CAR-T cell expansion, its anti-cancer and memory capacity has not yet been tested compared to aCD3/aCD28. Two different types of CAR (aCD19 scFv CD8- (CD28 or 41BB)-CD3z-EGFRt) expressing T cells were generated and their immunogenic phenotype, exhausted phenotype, Tcm-Tscm populations, and cytotoxic activities were determined in this study. The proportion of T cell memory phenotype in the CAR-T cell populations generated by PHA was observed to be higher than that of aCD3/aCD28-amplified CAR-T cells with similar cytotoxic (anti-tumor) and higher proliferation capacity. Here, we show that PHA provides long-term and efficient CAR-T cell production, suggesting a potential alternative to aCD3/aCD28-amplified CAR-T cells.