Enhance Memory CD8 ⁺ T Cell Formation via Downregulation of Hematopoietic Progenitor Kinase 1 and Sustained Mitochondrial Fitness

Memory CD8 ⁺ T cells are pivotal for long-term anti-tumor immunity due to their longevity and rapid response upon encountering tumor cells. Hematopoietic progenitor kinase 1 (HPK1), a member of the Ste20 family of kinases, restricts proximal T cell receptor (TCR) signaling and plays critical roles in T cell priming and activation. However, the impact of HPK1 on CD8 ⁺ T cell differentiation is not well understood. Here, we demonstrate that chimeric antigen receptor (CAR) T cells derived from patients lacking HPK1 exhibit a stronger memory phenotype. HPK1 deletion promotes the formation of precursor and central memory CD8 ⁺ T cells, resulting in superior and long-lasting antitumor activity in murine cancer models compared to WT mice. Additionally, HPK1 knockout induces metabolic reprogramming by enhancing oxidative phosphorylation (OXPHOS) and mitochondrial respiration complex activity. Mechanistically, HPK1 deletion downregulates mTOR signaling by reducing the phosphorylation of mTOR and S6. Increased mitophagy activity is observed in HPK1-depleted cells, with upregulation of key mitophagy regulators, including Pink1 and Bnip3l, maintaining mitochondrial fitness. Our study reveals that HPK1 regulates CD8 ⁺ T cell metabolic reprogramming, guiding cell differentiation and antitumor responses.