Abstract 2117: Epigenetic mechanisms control switching between metastatic and proliferative subtypes in the SW13 adrenal adenocarcinoma cell line

Abstract

Abstract The human adrenal carcinoma SW13 cell line can switch between a subtype which expresses the tumor-suppressor gene Brahma (BRM), SW13+, and one that does not, SW13-. Unlike many tumor supressor genes, which are often mutated, loss of BRM expression occurs post-transcriptionally and BRM expression can be restored via histone deacetylase (HDAC) inhibition. However, many of the previously characterized BRM inducing HDAC inhibitors are toxic, broad-spectrum inhibitors which have limited downstream use, and provide little insight into the specificity of BRM epigenetic suppression. In this work we sought to further characterize the oncogenic potential of the two SW13 subtypes, and to investigate the potential epigenetic regulators that contribute to the subtype switching. SW13 subtype morphology and growth rates were assessed by immunofluorescence and standard growth assays. Metastatic potential was characterized by measuring anchorage-independent growth with soft agar assays, collagenase activity with fluorescein-conjugated gelatin, and invasiveness into a 3D extracellular matrix. Differences in gene expression were measured by standard qRT-PCR and pathway-specific qRT-PCR profiling arrays. The capacity of specific HDAC inhibitors for their ability to induce switching between the SW13 subtypes was assessed by immunofluorescence and gene expression analyses. BRM deficient SW13- cells have both a faster doubling time and an increased rate of anchorage-independent growth, while SW13+ cells exhibit higher collagenase activity and invasive capacity. Significant differences in the expression of multiple genes involved in epigenetic chromatin remodeling as well as epigenetic chromatin modification were observed, indicating that these two subtypes also have unique gene expression profiles that could contribute to BRM regulation. Of those tested, inhibition of HDAC1 most efficiently increased the rate of conversion between SW13- and SW13+ cells, and did so in a dose dependent manner. After conversion to SW13+ subtype there is also increased acetylation on histone H3 but not histone H4 when compared to levels in SW13-, suggesting that the role of acetylation on the H3 tail may play an essential role in the subtype switch. These studies provide new insight into the functional consequences of BRM loss in the SW13 cell type and reveal potential targets for the reversal of BRM epigenetic silencing. Citation Format: McKale R. Davis, Elizabeth E. Hull. Epigenetic mechanisms control switching between metastatic and proliferative subtypes in the SW13 adrenal adenocarcinoma cell line. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2117. doi:10.1158/1538-7445.AM2015-2117