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Synthesis and In Vitro Efficacy of MMP9-Activated NanoDendrons

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journal contribution
posted on 05.08.2013, 00:00 by Lynn E. Samuelson, Randy L. Scherer, Lynn M. Matrisian, J. Oliver McIntyre, Darryl J. Bornhop
Chemotherapeutics such as doxorubicin (DOX) and paclitaxel (PXL) have dose-limiting systemic toxicities, including cardiotoxicity and peripheral neuropathy. Delivery strategies to minimize these undesirable effects are needed and could improve efficacy, while reducing patient morbidity. Here, DOX and PXL were conjugated to a nanodendron (ND) through an MMP9-cleavable peptide linker, producing two new therapies, ND2DOX and ND2PXL, designed to improve delivery specificity to the tumor microenvironment and reduce systemic toxicity. Comparative cytotoxicity assays were performed between intact ND-drug conjugates and the MMP9 released drug in cell lines with and without MMP9 expression. While ND2DOX was found to lose cytotoxicity due to the modification of DOX for conjugation to the ND; ND2PXL was determined to have the desired properties for a prodrug delivery system. ND2PXL was found to be cytotoxic in MMP9-expressing mouse mammary carcinoma (R221A-luc) (53%) and human breast carcinoma (MDA-MB-231) (66%) at a concentration of 50 nM (in PXL) after 48 h. Treating ND2PXL with MMP9 prior to the cytotoxicity assay resulted in a faster response; however, both cleaved and intact versions of the drug reached the same efficacy as the unmodified drug by 96 h in the R221A-luc and MDA-MB-231 cell lines. Further studies in modified Lewis lung carcinoma cells that either do (LLCMMP9) or do not (LLCRSV) express MMP9 demonstrate the selectivity of ND2PXL for MMP9. LLCMMP9 cells were only 20% viable after 48 h of treatment, while LLCRSV were not affected. Inclusion of an MMP inhibitor, GM6001, when treating the LLCMMP9 cells with ND2PXL eliminated the response of the MMP9 expressing cells (LLCMMP9). The data presented here suggests that these NDs, specifically ND2PXL, are nontoxic until activated by MMP9, a protease common in the microenvironment of tumors, indicating that incorporation of chemotherapeutic or cytostatic agents onto the ND platform have potential for tumor-targeted efficacy with reduced in vivo systemic toxicities.