CD44-Targeted Polymer-Paclitaxel Conjugates to Control the Spread and Growth of Metastatic Tumors.

One of the greatest challenges in cancer therapy is to control metastatic spread, seeding, and growth of tumors in distant organs. Recently, we reported on the design of a novel "drug-free" therapeutic copolymer bearing the antimigratory A5G27 peptide, designated P-(A5G27)-FITC, that shows excellent specificity to cancer cells overexpressing CD44v3 and CD44v6 and inhibits cancer cell migration and invasion. We demonstrated that P-(A5G27)-FITC accumulated preferentially in subcutaneous (sc) implanted 4T1 tumors following parenteral administration. Moreover, we showed that pretreatment of mice with P-(A5G27)-FITC prior to 4T1 cell inoculation inhibited colonization of circulating 4T1 cells in the lungs. In this study, we designed a new polymer-peptide-drug conjugate to inhibit vigorously growing primary tumors and control invasive behavior of cancer cells. To this end, the antimitotic drug (paclitaxel, PTX) was conjugated to P-(A5G27)-FITC. The targeted polymer-drug conjugate (P-(A5G27)-PTX) was significantly more toxic toward CD44-overexpressing cancer cells than the nontargeted copolymer. In vivo, a single iv injection of P-(A5G27)-PTX prolonged the survival of C57BL/6 mice with established B16-F10 lung metastases. When injected intraperitoneally into BALB/c mice implanted sc with 4T1 tumors, P-(A5G27)-PTX significantly decreased the rate of primary tumor growth, increased the median survival of mice, and reduced the number of 4T1 metastases in the lungs when compared to nontargeted copolymer. Most interestingly, the CD44-targeted "drug-free" copolymer P-(A5G27) (without PTX) significantly inhibited the rate of tumor growth and further prolonged the median survival time of mice to the same extent as the PTX-containing formulations (P-(A5G27)-PTX or free PTX). Overall, this study highlights the therapeutic potential of the HPMA copolymer-A5G27 conjugates ("drug-free" and PTX-bearing copolymers) to control the metastatic spread of cancer.

Complexation of cell-penetrating peptide-polymer conjugates with polyanions controls cells uptake of HPMA copolymers and anti-tumor activity.

PURPOSE: Cell penetrating peptides (CPPs) can mediate effective delivery of their associated drugs and drug carriers intracellularly, however their lack of cell specificity remains a major obstacle for their clinical development. We aimed at improving the cell specificity and therapeutic efficacy of HPMA copolymer-octaarginine (R8) conjugate (P-R8) in cells at the tumor micro-environment. METHODS: To avoid premature cell-penetration, the positively charged R8 moieties were masked via electrostatic complexation with various polyanionic molecules (heparin sulfate, hyaluronic acid, fucoidan and poly-glutamic acid). We followed the kinetics of the FITC-labeled P-R8 penetration into endothelial and cancer cells over-time after its complexation in vitro and further tested whether the in situ addition of a stronger polycation can trigger the release of P-R8 from the complexes to resume cell penetration activity. A murine model of B16-F10 lung metastasis was then used as an in vivo model for assessing the therapeutic efficacy of the P-R8, loaded with doxorubicin (P-R8-DOX), after its complexation with PGA. RESULTS: The intracellular penetration of P-R8-FITC was reversibly inhibited by forming electrostatic interactions with counter polyanions, and can be restored either gradually over time by dissociation from the polyanions, or promptly following the addition of protamine sulfate. Mice injected with B16-F10 cells and treated with P-R8-DOX/PGA complexes, exhibited a significant prolonged survival times when compared with DOX-treated mice or relative to mice treated with either P-R8-DOX or P-DOX alone. CONCLUSIONS: The gradual release of P-R8 from P-R8-DOX/PGA may improve the therapeutic efficacy of water-soluble based nanomedicines for the treatment of solid lung tumors.