Enhanced delivery of camptothecin to colorectal carcinoma using a tumor-penetrating peptide targeting p32

Abstract

Camptothesome, a sphingomyelin (SM)-conjugated camptothecin (CPT) vesicular nanotherapeutic, addresses the poor solubility and lactone instability of CPT while enhancing drug loading, pharmacokinetics, and tumor distribution compared to CPT physically entrapped in conventional liposomes. Despite these improvements, the tumor uptake remains limited. To further enhance the tumor delivery efficiency and minimize the off-target distribution, we functionalize Camptothesome with the LinTT1 peptide, a CendR motif, which binds to overexpressed p32 proteins on tumor cell surface, initiating effective transcytosis for deep tumor penetration. Via systematic screening, the optimal peptide ratio on Camptothesome is identified. LinTT1/Camptothesome significantly increases cancer cell uptake without affecting normal cell internalization, resulting in enhanced anti-colorectal cancer cells activity. Additionally, decorating Camptothesome with the LinTT1 cell-penetrating peptide enables effective transcytosis via a Golgi-dependent intracellular trafficking mechanism, significantly improving the intratumoral delivery while reducing distribution to normal tissues. In a human HCT116 xenograft colorectal cancer (CRC) mouse model, LinTT1/Camptothesome demonstrates superior antitumor efficacy compared to both Camptothesome and Onivyde by upregulating cleaved caspase-3 and γH2AX. Our study substantiates the potential of leveraging a tumor-penetrating peptide to enhance the tumor delivery efficiency of Camptothesome, maximizing its therapeutic index for improved treatment of human CRC.

Statement of significance

Despite the improved tumor delivery achieved by Camptothesome, its tumor distribution and penetration remain limited. This is because the enhanced permeability and retention effect only facilitates nanotherapeutic distribution to tumor periphery through leaky vasculature. The C-end Rule (CendR) motif-neuropilin receptor system enhances tumor-homing peptides by binding to cellular surface receptors, triggering transcytosis. Herein, LinTT1, the most potent CendR peptide that binds to the overexpressed p32 receptor on cancer cells, was effectively engineered onto Camptothesome using thiol-maleimide lipid chemistry. The LinTT1/Camptothesome significantly enhanced tumor uptake and penetration while minimizing accumulation in normal tissues, demonstrating remarkable anticancer efficacy in a human xenograft colorectal cancer model. Our findings highlight the critical role of tumor-homing peptides in unlocking the full therapeutic potential of Camptothesome.