TP53 deficiency in AML induces resistance to T-cell engagers through an immunosuppressive secretome

Bispecific T-cell engagers (BiTEs) have transformed the treatment of B-cell malignancies, yet clinical activity in AML has been modest at best, irrespective of the target antigen. Resistance is driven in part by the genetic heterogeneity of AML, most notably TP53 mutations, present in 10-15% of de novo and up to 25% of therapy-related AML. These mutations confer resistance to T-cell-based therapies, consistent with the dismal outcomes observed after allogeneic HSCT. Thus, we hypothesized that TP53 aberrations in AML contribute to cellintrinsic and extrinsic resistance against T-cell-based immunotherapy. To investigate this, we utilized the BiTE molecule AMG 330 (CD3×CD33) in co-cultures with primary AML cells (pAML) harboring TP53 deletions (DEL) and AML cell lines with a TP53 knockdown (KD). Cytotoxicity against TP53 DEL pAML and TP53 KD cell lines was reduced in co-cultures with T cells. In addition, T-cell proliferation and proinflammatory cytokine secretion was impaired in cocultures with TP53 KD cells. Transwell assays identified the secretome of TP53 KD AML cells as a key contributor to the observed immunosuppressive effect. Furthermore, proteomic analysis revealed TGF-β1 in TP53 KD co-cultures as a mediator of T-cell suppression. Lastly, RNA sequencing of T cells co-cultured with TP53 KD cells uncovered a transcriptional shift toward a senescent cell cycle profile. Our data collectively identify the immunosuppressive secretome of TP53-deficient AML as a key barrier to T-cell-engaging immunotherapies, underscoring an unmet clinical need for strategies able to restore T-cell function in TP53 KD AML.