Abstract B73: Unraveling the role of a novel endoplasmic reticulum protein in cancer cell migration

Abstract

Abstract Although considerable progress has been made in our understanding of cancer cell invasion, much of this complex cellular process remains a mystery, ultimately hindering advancements in treatment strategies targeting metastasis. Here we report, for the first time, the vital role of a novel endoplasmic reticulum (ER) resident protein identified by a PCR-subtraction hybridization technique, designated Cancer ER Invasion Gene (CERIG), in cancer cell migration and invasion. Clinical relevance of CERIG is highlighted by upregulation of CERIG in human invasive breast cancer specimens examined by immunohistochemistry and real-time RT-PCR, as well as increased expression in various other forms of human cancer as determined by data mining. This up-regulation of CERIG correlates with poor prognosis of patients with breast cancer assessed by a DNA microarray data-mining approach from three publicly available cohorts containing a total of 696 breast cancer patients. Silencing of CERIG in metastatic MDA-MB-435 cancer cells disrupted mesenchymal morphogenesis in vitro, resulting in a mesenchymal-to-epithelial transition, and interfered with cancer metastasis in vivo. Employing both gain- and loss-of-function approaches, CERIG was found to induce cancer cell migration and invasion. Enhanced cell migration required retention of CERIG within the ER, where this protein forms a stable complex with the ER chaperone protein, GRP78/BiP. Mutagenesis studies identified a novel ER retention motif within CERIG required for its ER localization, BiP interaction, and enhanced migration. Furthermore, fusion of the ER-retention domain to a soluble matrix metalloproteinase (MMP) prevents the secretion of the MMP by retaining it in the ER. Mechanistically, overexpression of CERIG results in ER calcium leakage via the inositol trisphosphate receptor (IP3R) and a subsequent increase in cytosolic calcium, ultimately resulting in activation of PKCα and cell migration. Moreover, chelating intracellular calcium abrogates CERIG induced PKCα activation and cell migration. Taken together, our data indicate that CERIG, as a novel ER resident protein, plays an important role in cancer progression, serving as a novel cell migration-promoting gene. Citation Format: Nikki Ann Evensen, Cem Kuscu, Antoine Dufour, Stanley Zucker, Jian Cao. Unraveling the role of a novel endoplasmic reticulum protein in cancer cell migration. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B73.