Abstract 200: PDLIM2 phosphorylation in determining breast cancer phenotype

Abstract

Abstract Several genes that are involved in cancer progression are induced by Insulin-like Growth Factor-1 (IGF-1). One of them encodes the PDZ-LIM protein PDLIM2, which is localized at the cytoskeleton and nucleus in epithelial and hematopoietic cells. PDLIM2 is repressed in certain cancers including breast cancers, but it is highly expressed in invasive cancer cells in triple negative breast cancer (TNBC), where it has also been associated with poor survival. PDLIM2 regulates the stability and activity of transcription factors including beta catenin, STATs, NFκB and IRFs and has been associated with ubiquitination and destabilization of proteins such as NF-κB, E-cadherin, and p27KIP1. However, PDLIM2 itself is also regulated by posttranslational modifications, but how this controls PDLIM2 activity is still largely unclear. Therefore, this study aimed to investigate PDLIM2 phosphorylation and its effect on PDLIM2 sub-cellular location and function in transcription factor regulation. The PDLIM2 protein sequence includes multiple potential phosphorylation sites and it migrates as several distinct phosphatase-sensitive species in SDS PAGE and 2D electrophoresis, indicating phosphorylation at several residues. Using cellular fractionation and immunofluorescence we show that PDLIM2 accumulates in the nucleus in response to cell stimulation with IGF-1 or TGFβ. Moreover, we show that inhibitors of Rho Kinases suppress PDLIM2 phosphorylation in response to these stimuli. In addition, we demonstrate that mutation of the predicted Rho Kinase phosphorylation sites in PDLIM2 reduce protein stability, an effect that can be reversed by application of proteasomal inhibitor. Overall, our results indicate that phosphorylation by Rho kinases plays an important role in the subcellular location and regulation of PDLIM2 function, which opens a new avenue in targeting PDLIM2 activity in invasive cancer cells. Citation Format: Orla T. Cox, Janina Berghoff, Deirdre A. Buckley, Rosemary O’Connor. PDLIM2 phosphorylation in determining breast cancer phenotype. [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 200.