CD28-Targeted Enzyme-Responsive Conformation-Switching Peptide Self-Assembly for Selective T-cell acute lymphoblastic leukemia (T-ALL) Therapy

T-cell acute lymphoblastic leukemia (T-ALL) is a highly aggressive hematologic malignancy with limited targeted therapies. CD28, a costimulatory receptor aberrantly overexpressed on T-ALL cells, presents a promising underexplored therapeutic target. In this study, we developed a modular enzyme-responsive self-assembling peptide, SAp-CD28, designed to selectively target CD28 and undergo receptor-mediated self-assembly in the tumor microenvironment. Upon dephosphorylation by overexpressed phosphatases, SAp-CD28 transitions from an α-helix to a β-sheet/β-turn rich structure, facilitating the formation of nano-oligomers that engage CD28 and activate cytotoxic pathways. Transcriptomic profiling revealed two key mechanisms: PLCγ1 pathway degradation and Akt signaling suppression, leading to calcium overload, cytoskeletal collapse, and necrotic cell death. Besides, confocal imaging suggested that the peptide self-assembly can enter the nucleus and disrupt it. In Jurkat xenograft models, SAp-CD28 demonstrated potent antitumor activity, and its combination with cytarabine resulted in near-complete tumor suppression, highlighting its potential for T-ALL treatment. This work introduces a CD28-targeted, enzyme-activated nanotherapeutic strategy that synergizes biochemical and mechanical mechanisms to selectively eliminate T-ALL cells. This multi-mechanistic tumor-killing strategy can also be extended to inspire therapeutic approaches for other diseases.