Arvizo, Rochelle R.

Abstract Gold nanoparticles (AuNPs) have been widely studied for use in disease therapeutics as targeting and imaging agents, drug delivery vehicles and as self-therapeutics. When AuNPs interact with the biological milieu they form a corona layer, which is predominantly composed of proteins. The outer “soft” layer is dynamic and here proteins are free to exchange over time. The inner “hard” layer on the other hand consists of proteins firmly bound to the NP surface. The Vromans effect predicts that given a limited surface area, low affinity, high abundance proteins, that first attach to the surface, are over time replaced by high affinity, low abundance proteins. Our aim was to enrich low abundance proteins on the AuNP surface to probe for differentially expressed proteins that are not detected by traditional methods of protein identification. We studied the binding of ovarian cell lysates (cancerous and non cancerous) to 10 nm sized positively and negatively charged AuNPs. The formation of corona around the AuNPs was characterized by dynamic light scattering and zeta potential measurements. The composition of the protein corona was identified using mass spectrometry. Proteins were also identified from the cell lysate pool to serve as a control to assess protein enrichment on NP surface. Using this approach, Hepatoma Derived Growth Factor (HDGF) was identified as a low abundance protein that was detected by mass spectrometry in cancer cells only after enrichment on the surface of positively charged AuNPs. HDGF is overexpressed in multiple ovarian cancer cells lines and knock down using siRNA shows decrease in cell proliferation, G2/M arrest and apoptosis. This suggests an important role of HDGF in the tumorigenicity of ovarian cancer, which could serve as an important therapeutic target for the disease. Citation Format: Karuna Giri, Rochelle Arvizo. Detecting low abundance therapeutic targets for ovarian cancer using engineered gold 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 3215. doi:10.1158/1538-7445.AM2013-3215

Although biomedical applications of nanotechnology, which typically involve functionalized nanoparticles, have taken significant strides, biological characterization of unmodified nanoparticles remains underinvestigated. Herein we demonstrate that unmodified gold nanoparticles (AuNPs) inhibit the proliferation of cancer cells in a size- and concentration-dependent manner by abrogating MAPK-signaling. In addition, these AuNPs reverse epithelial-mesenchymal transition (EMT) in cancer cells by reducing secretion of a number of proteins involved in EMT, up-regulating E-Cadherin, and down-regulating Snail, N-Cadherin, and Vimentin. Inhibition of MAPK signaling and reversal of EMT upon AuNP treatment inhibits tumor growth and metastasis in two separate orthotopic models of ovarian cancer. Western blot analyses of tumor tissues reveal up-regulation of E-Cadherin and down-regulation of Snail and phospho-MAPK, confirming the reversal of EMT and inhibition of MAPK signaling upon AuNP treatment. The ability of a single self-therapeutic nanoparticle to abrogate signaling cascades of multiple growth factors is distinctive and purports possible medical applications as potential antitumor and antimetastatic agent.

Abstract Oncogenic activation of Bmi-1 is found in a wide variety of epithelial malignancies including ovarian cancer, yet a specific mechanism for overexpression of Bmi-1 has not been determined. Thus, realizing the immense pathologic significance of Bmi-1 in cancer, we wanted to investigate if microRNA (miRNA) aberrations played a role in the regulation of Bmi-1 in ovarian cancer. In this report, we identify two miRNAs, miR-15a and miR-16, that are underexpressed in ovarian cell lines and in primary ovarian tissues. We show that these miRNAs directly target the Bmi-1 3′ untranslated region and significantly correlate with Bmi-1 protein levels in ovarian cancer patients and cell lines. Furthermore, Bmi-1 protein levels are downregulated in response to miR-15a or miR-16 expression and lead to significant reduction in ovarian cancer cell proliferation and clonal growth. These findings suggest the development of therapeutic strategies by restoring miR-15a and miR-16 expression in ovarian cancer and in other cancers that involve upregulation of Bmi-1. [Cancer Res 2009;69(23):9090–5]