Giri, Karuna

Ovarian cancer is the eighth most common cancer and the fifth leading cause of cancer death among US women. Hepatoma‐derived growth factor (HDGF) is a heparin binding, secreted mitogen with prognostic value in multiple cancers. We previously reported that HDGF is overexpressed in ovarian cancer. Surprisingly, the mechanisms by which HDGF acts in any cell type remains to be fully elucidated. We hypothesized that overexpression of HDGF in ovarian cancer cells is functionally relevant and that HDGF confers pro‐survival and proliferative properties, promoting cancer growth. To elucidate intracellular and extracellular signaling mechanisms, we examined the effect of HDGF knockdown via siRNA, overexpression of HDGF and stimulation by full‐length recombinant protein. Immunofluorescence image analysis showed nuclear localization of HDGF in OV202 cell line. Additionally, HDGF was minimally secreted but passively released in greater amounts by necrotic cells. Extracellular HDGF stimulated phosphorylation of ERK and p38. In contrast, modulating intracellular HDGF did not affect MAPK pathways. In fact, intracellular HDGF functioned in a distinct manner by regulating cellular metabolism. This suggests that HDGF acts in ovarian cancer cells via two distinct mechanisms, both of which could be exploited for ovarian cancer therapy. Supported by the Mayo Graduate School (Giri) and the Department of Anesthesiology, Mayo Clinic (Prakash).

Bacterial biofilms are associated with persistent infections and antibiotics resistance which substantially complicate patient care. Surface engineering of nanoparticles represents a novel and unconventional approach to disrupt biofilms and target bacterial pathogens.

Cationic quantum dots effectively penetrate biofilms, providing insight for targeting and imaging applications.

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

Abstract Hydrogen sulfide (H2S), the third gasotransmitter, has recently attracted a lot of attention for its cytoprotective action and role in angiogenesis. Dysregulation of the major enzymes which produces H2S namely, cystathionine beta synthase (CBS), cystathionine gamma lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) have also been implicated in a large number of pathological conditions that range from neurological disorders to cardiovascular diseases. Surprisingly, studies on the role of these enzymes in cancer is scarce, especially, that of CBS. Relapse with a drug resistant and aggressive phenotype is a common occurrence in ovarian cancer with an overall 5-year survival of approximately 30%. Here we report that, CBS, a key enzyme required for sulphur amino acid metabolism, plays a critical role in promoting ovarian cancer growth, metastasis and drug resistance. Overexpression of CBS was observed in a majority of ovarian cancer cell lines utilized in our study compared to normal ovarian surface epithelial cells. Silencing CBS in A2780 cells using siRNA or a CBS-specific inhibitor, aminooxyacetic acid reduced proliferation of ovarian cancer cells by dramatically reducing total glutathione levels, H2S levels and thereby enhancing oxidative stress. Downregulation of CBS reduced activation of NF-kB and upregulated p53 protein levels thereby inactivating the antioxidant network of the cells. A deeper insight into the intracellular localization of CBS by confocal fluorescence microscopy demonstrated a mitochondria specific distribution and silencing CBS caused mitochondrial superoxide accumulation that resulted in decreased mitochondrial respiration, reduced ATP production and increased ADP-to-ATP ratio. Furthermore, silencing CBS, augmented the activity of cisplatin in vitro in A2780 cells and in vivo in an orthotopic model of advanced ovarian cancer. Nanoliposomal delivery of CBS siRNA significantly reduced the number of tumor nodules in a chemoresistant orthotopic mouse model of ovarian cancer. To our knowledge, this is the first study demonstrating the importance of CBS in ovarian cancer progression and drug resistance and therefore is a viable target for future anti-cancer therapies. Citation Format: Sounik Saha, Sanjib Bhattacharyya, Karuna Giri, Ian R. Lanza, K. Sreekumar Nair, Nicholas B. Jennings, Rakesh Kumar, Anil K. Sood, Resham Bhattacharya, Priyabrata Mukherjee. Role of cystathionine beta-synthase in ovarian cancer growth, metastasis and drug sensitivity. [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 1882. doi:10.1158/1538-7445.AM2013-1882