Abstract 4420: Heparan sulfate proteoglycans mediate SW13 oncogenic potential and response to granulin

Abstract

Abstract The SW13 adrenal adenocarcinoma cell line exists as two epigenetically and phenotypically distinct subtypes. One is a highly proliferative epithelial subtype lacking the expression of key tumor suppressor proteins, Brm and Brg1, the intermediate filament protein vimentin, and the cell cycle check point protein CD44 (SW13-), while the other is a slow growing, mesenchymal-like subtype which expresses all of these proteins (SW13+). Evidence strongly suggests that subtype determination is epigenetic in nature, as HDAC inhibitors can induce an SW13- to SW13+ subtype switch, but the cellular and environmental factors that regulate cellular phenotype have yet to be characterized. We performed a comprehensive microarray analysis and identified heparan sulfate proteoglycan (HSPG) binding as a primary pathway affected between these two subtypes. HSPGs are glycoproteins present in the extracellular matrix that can have tumor-promoting or tumor-suppressing activities depending on the number and sulfation status of attached sugar chains known as glycosaminoglycans (GAGs). Quantitative RT-PCR was then used to confirm the increased expression of the HSPGs, serglycin and glypican-3, as well as the HSPG-binding growth factors granulin and fibroblast growth factors-1 and -2 in SW13+ cells. Furthermore, HDAC inhibition was also shown to increase the expression of these genes in a time-dependent manner. As granulin over-production is associated with cancer progression in a number of human cancers, we were interested in examining the role of this HSPG binding growth factor further. A pro-granulin ELISA showed that SW13+ cells secrete significantly more granulin than SW13- cells. Intriguingly however, treatment with exogenous granulin increases growth rates in the already highly proliferative SW13- subtype, but had no effect on SW13+ growth. We hypothesized that the pleiotropic response of SW13 cells to growth factor treatment may be the result of HSPG post-translational modifications, so we assessed total GAG sulfation was by dimethylmethylene blue assay, and indeed the SW13+ cells were found to have significantly higher levels of total GAG sulfation than SW13- cells. Thus, transcriptional and post-translational modifications of HSPGs may contribute to SW13 phenotype control, and ultimately may affect tumorigenesis. Citation Format: McKale Davis, Elizabeth Hull. Heparan sulfate proteoglycans mediate SW13 oncogenic potential and response to granulin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4420.