Reliable high-PAP-1-loaded polymeric micelles for cancer therapy: preparation, characterization, and evaluation of anti-tumor efficacy

The mitochondrial potassium channel Kv1.3 is a critical therapeutic target, as its blockade induces cancer cell apoptosis, highlighting its therapeutic potential. PAP-1, a potent and selective membrane-permeant Kv1.3 inhibitor, faces solubility challenges affecting its bioavailability and antitumor efficacy. To circumvent these challenges, we developed a tumor-targeting drug delivery system by encapsulating PAP-1 within pH-responsive mPEG-PAE polymeric micelles. These self-assembled micelles exhibited high entrapment efficiency (91.35%) and drug loading level (8.30%). As pH decreased, the micelles exhibited a significant increase in particle size and zeta potential, accompanied by a surge in PAP-1 release. Molecular simulations revealed that PAE's tertiary amine protonation affected the self-assembly process, modifying hydrophobicity and resulting in larger, loosely packed particles. Furthermore, compared to free PAP-1 or PAP-1 combined with MDR inhibitors, PAP-1-loaded micelles significantly enhanced cytotoxicity and apoptosis induction in Jurkat and B16F10 cells, through mechanisms involving decreased mitochondrial membrane potential and elevated caspase-3 activity. In vivo, while free PAP-1 failed to reduce tumor size in a B16F10 melanoma mouse model, PAP-1-loaded micelles substantially suppressed tumors, reducing volume by up to 94.26%. Fluorescent-marked micelles effectively accumulated in mouse tumors, confirming their targeting efficiency. This strategy holds promise for significantly improving PAP-1's antitumor efficacy in tumor therapy.