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, ND2(DOX) and ND2(PXL), 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 ND2(DOX) was found to lose cytotoxicity due to the modification of DOX for conjugation to the ND; ND2(PXL) was determined to have the desired properties for a
prodrug delivery system. ND2(PXL) 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 ND2(PXL) 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 (LLC(MMP9)) or do not (LLC(RSV)) express MMP9 demonstrate the selectivity of ND2(PXL) for MMP9. LLC(MMP9) cells were only 20% viable after 48 h of treatment, while LLC(RSV) were not affected. Inclusion of an
MMP inhibitor,
GM6001, when treating the LLC(MMP9) cells with ND2(PXL) eliminated the response of the MMP9 expressing cells (LLC(MMP9)). The data presented here suggests that these
NDs, specifically ND2(PXL), 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.