Abstract 1615: Inhibition of vascular endothelial cell tube formation by zinc nanoparticles.

Tumor angiogenesis, new blood vessel formation induced by cancer cells, is a rate-limiting step in cancer growth and metastasis, and is therefore an excellent target for therapy. Currently, the anticancer drugs based on anti-angiogenic strategies have limited efficacy, and often engender inherent or acquired resistance. Indeed, there is growing evidence to suggest that anti-angiogenic treatment of cancer using current inhibitors may trigger more invasive and metastatic tumors due to the fact that when one angiogenic signaling pathway is blocked, new signaling pathways are triggered. We have tackled the problem from a different angle by targeting the copper ion rather than the many angiogenesis inducing biomolecules. Copper is a co-factor for more than a dozen key angiogenic promoters essential for cancer angiogenesis. As such, depletion of copper should inactivate multiple angiogenic signaling pathways. Specifically, we have developed a nanoparticle-based drug to selectively sequester copper ions in order to disrupt tumor angiogenesis, resulting in inhibition of tumor growth and metastasis. Cellular uptake of nanoparticles (NPS) was documented by confocal microscopy of HuVEC and cancer cell lines treated with carboxyfluorescein tagged NPS. Copper levels were measured by atomic absorption spectrophotometry of lysates of CuCl2 treated cells, after 8-hr treatment with NPS or control diluent. Following treatment of HepG2 cells with copper depleting NPS, we observed that copper levels dropped from 402 fg/cell to undetectable levels. Although NPS significantly reduced copper levels of CuCl2 treated HepG2 cells, cell viability measured by trypan blue exclusion and MTT assays was > 89% (for 50 uM NPS). Similar viability was seen for the three cell lines tested. Using an in vitro model system for angiogenesis, we have examined induction of tube formation by human Vascular Endothelial cells (HuVEC) cultured on basement membrane extracts. Following induction by fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor (VEGF) treatment, outgrowth and branching of HuVEC cells was measured in the presence or absence of NPS. We observed that the copper depleting NPS suppressed FGF2 induction of tube formation and branching by HuVEC cells. Overall our results have demonstrated that these novel zinc NPS: (i) are highly effective copper depleting agents able to accumulate in endothelial cells; (ii) are non-toxic to vascular endothelial and cancer cells, and (iii) inhibit endothelial cell tube formation in vitro. We expect these novel copper-depleting agents will significantly impact tumor angiogenesis in vivo and dramatically enhance cancer therapy in the future. Citation Format: Vindya S. Perera, Haiwa Wu, Liu D. Yang, Songping D. Huang, Gail C. Fraizer. Inhibition of vascular endothelial cell tube formation by zinc nanoparticles. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1615. doi:10.1158/1538-7445.AM2013-1615