Targeting urokinase and the transferrin receptor with novel, anti-mitotic N-Alkylisatin cytotoxin conjugates causes selective cancer cell death and reduces tumor growth

Authors

K L. Vine, University of WollongongFollow
V. Indira Chandran, University of Wollongong
J M. Locke, University of WollongongFollow
L Matesic, University of WollongongFollow
J Lee, University of WollongongFollow
D Skropeta, University of WollongongFollow
J B. Bremner, University of WollongongFollow
M Ranson, University of WollongongFollow

RIS ID

49486

Publication Details

Vine, K. L., Chandran, V., Locke, J. M., Matesic, L., Lee, J., Skropeta, D., Bremner, J. B. & Ranson, M. (2012). Targeting urokinase and the transferrin receptor with novel, anti-mitotic N-Alkylisatin cytotoxin conjugates causes selective cancer cell death and reduces tumor growth. Current Cancer Drug Targets, 12 (1), 64-73.

Abstract

Tumor-specific delivery of ligand-directed prodrugs can increase the therapeutic window of chemotherapeutics by maintaining efficacy whilst decreasing toxic side effects. We have previously described a series of synthetic N-alkylated isatin cytotoxins that destabilize microtubules and induce apoptosis with 10-fold greater potency than conventional anti-mitotics in vitro. Here, we report the characterization, in vitro cytotoxicity and in vivo efficacy of a lead compound, 5,7-dibromo-N-(p-hydroxymethylbenzyl)isatin (N-AI) conjugated via an esterase-labile linker (N-AIE) to two proven targeting ligands, transferrin (Tf) and plasminogen activator inhibitor type 2 (PAI-2/serpinB2). N-AI was released from N-AIE and the targeting ligands Tf/PAI-2 in an esterase-dependent manner at 37 °C and both Tf- and PAI-2-N-AIE conjugates were stable at physiological pH. Human cancer cell lines which vary in their expression levels of Tf receptor (TfR/CD71) and PAI-2 target, receptor bound urokinase (uPA) selectively internalized the conjugates. Tf-N-AIE was up to 24 times more active than the free drug and showed clear selectivity patterns based on TfR levels. PAI-2-N-AIE showed equivalent activity compared to the parent drug and strong selectivity patterns for uPA levels. In preliminary in vivo experiments, the PAI-2- and Tf-N-AIE conjugates were efficacious at 1/20th and 1/10th of the dose of the free N-AI, respectively, in a metastatic, orthotopic human breast tumor xenograft mouse model. Thus, this strategy specifically delivers and concentrates a novel class of isatin-based, tubulin destabilizing agents to tumors in vivo and warrants further detailed preclinical investigation.