Guided “chemosensitizers” for treating recurrent metastatic breast cancer Free

2200

INTRODUCTION: Metastatic dissemination of cancer cells remains the primary challenge in the management of neoplastic disease. The metal-binding domain (MBD) of IGFBP-3 can serve as a guidance system for therapeutic molecules in the treatment of disseminated disease. EXPERIMENTAL PROCEDURES AND DATA: We have shown that a 22-amino acid MBD domain from the C-terminus of IGFBP-3 directs in vivo targeting and intracellular delivery of marker proteins GFP and horseradish peroxidase to selected tissues in rodents. The local mechanism of uptake into target cells involves surface markers characteristic of malignancy such as transferrin receptor and beta-3 integrins. Using a panel of 54 cancer cell lines and paired gene arrays, we show that upregulated stress mechanisms within target cells also correlate with the efficiency of MBD-mediated cell uptake. In addition, we show that systemic delivery of MBD is mediated by red blood cells. Based on our hypothesis that (a) metastatic cells exhibit upregulated stress-coping and survival mechanisms (hsp70, NF-kappa-B, Akt, survivin, MDM2) (b) interventions designed to simultaneously inhibit several of these mechanisms will exhibit discriminant cytotoxicity for metastatic cells and broader spectrum, and (c) MBD can effectively and selectively deliver inhibitors to disseminated cancer cells in vivo, inhibitor peptide sequences tagged with MBD were designed and tested successfully in cytotoxicity assays in vitro against panels of breast, prostate and leukemia cells. In murine models short-term treatment with cocktails of these peptides significantly reduces MDA-MB-435 breast cancer cell burden in bone marrow and CCRF-CEM leukemia cell burden in spleen as measured by human-PCR specific amplification of whole tissue genomic DNA (both models p <0.05). We show that peptide cocktails produce synergy with paclitaxel and 5-fluorouracil in vitro. Synergy between MBD-guided peptides and paclitaxel treatment has been confirmed in murine models. CONCLUSION: MBD-tagged inhibitory peptides can serve as guided “chemosensitizers” for co-administration with low-dose paclitaxel or 5-fluorouracil, in recurrent metastatic settings. Key features of this designed intervention include its combinatorial complexity and low toxicity as well as its ability to directly access privileged compartments such as bone marrow and spleen.