Abstract 2112: A novel mechanism of NF-κB regulation in bladder cancer

Abstract

Abstract Protein methyltransferases (PMTs) methylate protein lysine and arginine residues and play an important role in regulating chromatin remodeling and gene transcription. Deregulation of SET-domain-containing PMTs has a crucial role in carcinogenesis (1). SETD6 is a novel methyltransferase that has been shown to monomethylate p65/RelA (a principal subunit of NF-κB) at Lys310. Monomethylated p65 recruits GLP (G9A-like protein), a histone dimethyl transferase to the NF-κB target genes, which results in transcriptional repression (2). The role of SETD6, in carcinogenesis in general and bladder cancer in particular is unknown. We identified SETD6 as a significantly upregulated gene in a screen of chromatin modifying genes that are differentially regulated in bladder cancer cells compared with normal urothelial cells. Subsequently qPCR and immunoblotting showed upregulation of SETD6 at the mRNA and protein level in bladder cancer cells and tissues relative to their normal counterparts. Surprisingly, we found that overexpression of SETD6 increased nuclear level of NF-κB, phosphorylation of NF-κB at Ser536 and the transcriptional activity of NF-κB. Overexpression of wild type SETD6 increased viability and proliferation of non-tumorigenic urothelial cells while overexpression of mutant SETD6 had no effect. Furthermore, knocking down SETD6 transiently with si-SETD6 significantly decreased viability and proliferation of bladder cancer cells suggesting that SETD6 may have a growth promoting role in bladder cancer. Our data shows for the first time that non-histone protein lysine methylation of NF-κB-p65 by SETD6 may be a novel way to regulate NF-κB pathway in bladder cancer. The lack of curative strategies for bladder cancer leads to recurrence rates of 45-70% with >15% of patients developing muscle invasive disease (3). These observations underscore the need to understand survival mechanism in bladder cancer. In this regard our findings are highly significant and could lead to targeting SETD6/ NF-κB axis in bladder cancer in the future.