Abstract 1210: Activation of heterogeneous nuclear ribonucleoprotein K (HNRNPK) by ERBB2/ERBB3

Abstract

Abstract ERBB2 (HER2/neu) amplification constitute one of the most prominent oncogenic amplification event in breast cancer, and ERBB2 overexpression is well established as a predominantly proliferation and metastasis favoring signaling input. It is consequently the object of different targeted therapies (e.g. Trastuzumab, Pertuzumab or Lapatinib). We carried out 2-D difference gel electrophoresis based proteomics studies (DIGE) of early posttranslational protein modifications in MCF7 breast cancer cells in response to ligand induced activation. These studies have identified heterogeneous nuclear ribonucleoprotein K (HNRNPK) as a target for rapid tyrosine phosphorylation after ERBB2/ERBB3 activation by neuregulin β1. Upregulation of protein levels coupled with cytoplasmic accumulation of HNRNPK has been found to be associated with its oncogenic role in several types of cancer, and HNRNPK overexpression enhances the tumorigenicity of breast cancer cells in cell culture models. Previous studies have shown that HNRNPK levels are reduced in breast cancer cells after prolonged treatment with EGFR or ERBB2 directed therapeutic antibodies. However, while molecular mechanistic data exist on HNRNPK from a variety of model systems, we currently lack a coherent mechanistic framework of the crosstalk of ERBB2 and HNRNPK signaling in breast cancer. Following our DIGE analysis, we found that ligand induced and ERBB2/ERBB3 mediated tyrosine phosphorylation of HNRNPK in MCF7 cells is mediated by members of the SRC kinase family. Following ligand dependent stimulation, activation of HNRNPK coincides with a cytoplasmic relocalization of a relatively small portion of the predominantly nuclear HNRNPK pool. We compared our observations of ligand induced activation with the status of HNRNPK in ERBB2 over expressing breast cancer cell lines in presence or absence of ERBB2 targeted inhibitors. These studies are aimed at elucidating the interplay of HNRNPK and constitutive ERBB2 signaling in breast cancer cells and its role in cellular transformation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1210. doi:10.1158/1538-7445.AM2011-1210