Abstract 3362: PBRM1 regulates the transcription of cell adhesion genes in ccRCC

Abstract

Abstract Advances in parallel sequencing have facilitated the recent identification of Polybromo-1 (PBRM1), a component of the PBAF (Polybromo-associated-BRG1- or BRM-associated factors) chromatin remodeling complex, as the second most frequently mutated gene in clear-cell renal cell Carcinoma (ccRCC). While several studies have described the diversity of PBRM1 mutations in ccRCC and established the mutation of PBRM1 as a “driver” of ccRCC carcinogenesis, little is known about the biological significance of PBRM1. With the intent of shedding light on the mechanistic roles of PBRM1, we have employed Next Generation Sequencing to delineate the transcriptional profile of cellular models of ccRCC with or without PBRM1 expression and identified genes associated with cell adhesion to be regulated by PBRM1 in 2D monolayer cultures. Since 2D cultures lack the architectural complexities to support studies pertaining to cellular adhesion, we evaluated the role of PBRM1 in 3D culture on Basement Membrane Matrix to provide a physiologically relevant analysis of gene expression and the resulting cellular phenotype. The results showed that of the 97 cell adhesion genes identified to be upregulated by PBRM1 in 2D cultures, 45 were also upregulated in 3D cultures and a subset of 32/45 genes underwent increased gene expression in 3D with respect to 2D cultures. The gene expression profile of candidate genes were verified by qPCR and Western Blotting. Mining The Cancer Genome Atlas (TCGA) publicly available data, we were able to correlate the gene expression profiles of cell adhesion genes identified in 3D cultures with those of ccRCC patients bearing at least 1 copy of the PBRM1 gene. Furthermore, we performed a PBRM1-ChIP-seq to map the genome-wide targets of PBRM1 and revealed the association of PBRM1 occupancy at proximal regulatory regions of 8/45 cell adhesion genes. All of these taken together, indicate a role for PBRM1 in regulating the gene expression of cell adhesion genes which act as important players in cellular morphogenesis and responsiveness to changes in the external environment. Disruption of cell adhesion is believed to affect signal transduction and pave the way facilitating metastasis in neoplastic cells. Currently we are investigating the effect of loss-of-PBRM1 on Epithelial to Mesenchymal Transition (EMT) and metastasis in ccRCC. Note: This abstract was not presented at the meeting. Citation Format: Basudev Chowdhury. PBRM1 regulates the transcription of cell adhesion genes in ccRCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3362. doi:10.1158/1538-7445.AM2017-3362