Tarhan, N. | bioRxiv Science

bioRxiv2023

Phytohemagglutinin-Activated CAR-T Cells: Prolonged Persistence and Enhanced Anti-Tumor Response in CD19-Specific Acute Lymphoblastic Leukemia

In recent times, chimeric antigen receptor (CAR)-T cell therapy has shown rapid advancements and gained clinical approval for use in cancer immunotherapy. CAR, a synthetic receptor integrated into autologous T cells, has yielded highly successful results in patients with leukemia. The significant potential of CAR-T cells has been validated through clinical trials in adult and pediatric cancer treatments. Our therapy developed specifically for CD19-specific Acute Lymphoblastic Leukemia (ALL) has shown promising results in in vitro and in vivo tests. To enhance the response against cancer, provide a bistimulatory effect, and increase stability, we designed two different CAR structures specific to CD19. These designs incorporate the CD28 and 41BB costimulatory domains. Through in vitro analysis, we evaluated the population ratios and cytotoxic activities of Central Memory T cells (TCM) and Stem Cell Memory T cells (TSCM) in CAR-T (CAR1928-T and CAR19BB-T) cells. Our initial design, CAR1928-T, produced an effective anti-tumor response. With our second design, CAR19BB-T, we not only achieved an anti-tumor effect but also conferred memory capabilities, leading to a comprehensive treatment approach. We demonstrated that CAR-T cells produced using Phytohemagglutinin (PHA) exhibited increased persistence in vitro and in vivo compared to anti-CD3 and anti-CD28 stimulation. The use of PHA to activate CAR19BB-T cells developed a long-lasting and effective CAR-T cell production method in vivo using cancerous animal models. CAR-T cell-treated mice survived tumor-free for up to 60 days, surpassing the survival of mice that received tumors only. Additionally, CAR19BB-T cell production with PHA remained stable over time. These results highlight a novel CAR-T cell production approach with a high-memory T cell profile capable of delaying or preventing cancer relapse. We optimized the method for the production of long-term and effective CAR-T cells and tested it in preclinical experiments. As a result, it was demonstrated that CAR-T cells generated with PHA, when administered as a co-stimulatory dose, can provide continuous proliferation and long-term persistence without compromising their anti-cancer efficacy. Preclinical studies have been completed to obtain valuable data for enhancing the long-term effectiveness of CAR-T therapy in clinical trials and transitioning to clinical applications.

immunology↗

bioRxiv2022

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

The 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 therapys 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.

cancer biology↗