Enhancing chimeric antigen receptor T cell therapy by modulating the p53 signaling network with ?133p53a

Chimeric antigen receptor (CAR) T cell dysfunction is a major barrier to achieving lasting remission in hematologic cancers, especially in chronic lymphocytic leukemia. We have shown previously that ?133p53a, an endogenous isoform of the human TP53 gene, decreases in expression with age in human T cells, and that reconstitution of ?133p53a in poorly functional T cells can rescue proliferation. Although ?133p53a lacks a transactivation domain, it can form heterooligomers with full length p53 and modulate the p53-mediated stress response. Here, we show that constitutive expression of ?133p53a, potentiates the anti-tumor activity of CD19-directed CAR T cells, and limits dysfunction under conditions of high tumor burden and metabolic stress. We demonstrate that ?133p53a-expressing CAR T cells exhibit a robust metabolic phenotype, maintaining the ability to execute effector functions and continue proliferating under nutrient limiting conditions, in part due to upregulation of critical biosynthetic processes and improved mitochondrial function. Importantly, we show that our strategy to constitutively express ?133p53a improves the anti-tumor efficacy of CAR T cells generated from CLL patients that previously failed CAR T cell therapy. More broadly, our results point to the potential role of the p53-mediated stress response in limiting the prolonged antitumor functions required for complete tumor clearance in patients with high disease burden, suggesting that modulation of the p53 signaling network with ?133p53a may represent a translationally viable strategy for improving CAR T cell therapy. Overall design: To understand the impact of ?133p53a on CAR T cell function, we harvested RNA from CAR T cells isolated on day 3.5 of in vitro co-culture with nalm6 leukemia cells. To understand whether there are differences prior to co-culture we also harvested RNA from CAR T cells isolated from CAR product. All ?133p53a-CAR T cells were compared to WT control CAR T cells which transduced with mCherry. All samples were collected across three healthy human donors.