Project Goal:

The research proposed here will identify DNA methylation programs that limit expansion and persistence of CAR T cells generated from a healthy donor. In pediatrics, a parent can serve as a T cell donor and our study will provide further insight into the epigenetic programs that restrict allogeneic CAR T cell survival after infusion into patients. Furthermore, our study will provide insight into leukemia-associated dysfunction of autologous T cells used for CAR T cell therapy in pediatric patients. Lastly, these studies will identify targetable molecular mechanisms that can be exploited to prolong CAR T cell anti-tumor responses.

Project Update 2024:

Chimeric antigen receptor (CAR) T cells are a promising immunotherapy for patients with relapsed/refractory leukemias. CD19 CAR T cells function by targeting the expression of CD19 which is on the surface of B-cells. We have shown that many patients who have received CD19-directed CAR T cell therapy relapse with CD19-positive cancer indicating that the CAR T cells lack functional persistence. Indeed, autologous CD19 CAR T cells (CAR T cells generated using T cells from the patient) acquire exhaustion-associated epigenetic programming which limits their function against tumor. We hypothesize that autologous-derived CAR T cells are more susceptible to exhaustion due to underlying leukemia-induced T cell dysfunction. In other words, the T cells used to generate the therapeutic CAR T cells are not healthy and therefore may not perform optimally against cancer. This grant proposes to explore the role of leukemia-induced T cell dysfunction on cellular therapy and circumvent this issue by using allogeneic CAR T cells derived from a healthy donor. We have now published our findings on autologous CD19 CAR T cell exhaustion that occurs in patients during an in vivo tumor response (Zebley et al. Cell Reports 2021). My proposal discusses examining these dysfunctional programs in allogeneic T cells from patients who received CAR T cells from a healthy haploidentical donor. While awaiting patient accrual on the clinical trial, we have focused our efforts on the T cell dysfunction present in AML patients compared to ALL patients. Specifically, we are looking deeper into the factors in the tumor microenvironment that are contributing to the underlying T cell dysfunction. Inflammatory danger associated molecular patterns (DAMPs) have been shown to be elevated in the plasma of adults with myeloid hematologic malignancies prompting our investigation into the role of extracellular inflammatory molecules in pediatric leukemias. Our preliminary data shows that the presence of DAMPs changes the phenotypic properties of healthy donor-derived T cells. We will next explore the plasma of leukemia patients to quantify the level of DAMPs and further investigate whether this proinflammatory environment can limit T cell function in pediatric ALL and AML. Furthermore, we have identified that disruption of the epigenetic regulator ASXL1 allows T cells to resist the immunosuppressive tumor microenvironment and maintain anti-tumor function. Results from these studies will provide a rationale to develop allogeneic CAR T cell protocols from healthy donors as well as genetically modified ASXL1 KO CAR T cells with the goal of establishing a sustained anti-tumor response that can prevent disease relapse.