1 - Joint Session
Oral presentations Experimental hematology / oncology
Nov. 22, 2023, 8:30 a.m. - 10:00 a.m., Boston 1-2


Modulation of the cholesterol or Wnt signaling pathways overcomes TP53 deficiency-associated resistance to CAR T-cell therapy in AML
J. Mueller1, R. Schimmer1, F. Schneiter2, J. Fullin1, N. Klemm1, V. Lysenko1, C. Pellegrino1, R. Myburgh1, L. Volta1, C. Koch1, A. P. A. Theocharides1, K. J. Kurppa3, B. L. Ebert4, T. Schroeder2, M. G. Manz1, S. Boettcher1, Presenter: R. Schimmer1 (1Zurich, 2Basel, 3Turku, 4Boston)

TP53-mutant myeloid neoplasms are distinct clinicogenomic entities characterized by poor survival. Chimeric antigen receptor (CAR) T-cell therapy might be a promising therapeutic option for TP53mut AML/MDS. However, the AML-intrinsic determinants of efficacy of T-cell-based approaches are largely unknown. We here address the highly relevant question as to whether, and if so, how TP53 deficiency in AML cells might confer resistance to CAR T-cell therapy.
Taking advantage of a recently developed, CRISPR/Cas9-engineered TP53 isogenic AML cell line harboring TP53 null, missense, or wildtype alleles as well as making use of CD33- and CD123-directed second generation CAR T-cells, we use a combination of in vitro flow cytometry-based co-incubation assays, live-cell imaging, gene expression profiling and an in vivo therapeutic model to address our objective.
We observed increased resistance of TP53mut AML cells to CAR T-cells in vitro (Panel A). CAR T-cells engaging TP53mut AML cells upregulated exhaustion markers resulting in longer time-to-killing (Panel B-C). TP53mut AML xenografted immunodeficient mice treated with CAR T-cells exhibited shorter survival compared to wildtype controls (Panel D). Transcriptional profiling revealed upregulation of the cholesterol pathway in TP53mut AML cells under CAR T-cell attack (Panel E). Simultaneously, CAR T-cells engaging TP53mut AML demonstrated a downregulated Wnt pathway (Panel F). Rational pharmacological targeting of either of these pathways - using simvastatin and BIO-acetoxime, respectively - rescued TP53mut AML cell sensitivity to CAR T-cell-mediated killing (Panel G). Similarly, CRISPR/Cas9-engineering of CAR T-cells to upregulate Wnt pathway signaling constitutively via Regnase-1 knockout rescued TP53mut AML cell sensitivity (Panel H).
We demonstrate that TP53 deficiency in AML cells confers resistance to CAR T-cell therapy by inducing CAR T-cell exhaustion. Furthermore, we identified the cholesterol pathway as a potential therapeutic vulnerability of TP53mut AML cells, and the Wnt pathway as a promising avenue to enhance the efficacy of CAR T-cell therapy. Our data suggest that pharmacological co-interventions or genetic engineering of CAR T-cell therapies may be a strategy towards more efficacious and tolerable cellular therapies for patients with TP53mut myeloid neoplasms.
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