Human KIAA0090 (EMC1) is an evolutionarily conserved and ubiquitously expressed gene that maps to a chromosomal region (1p36.13) with frequent aberrations in several types of cancer. The RefSeq mRNA (isoform 1) of human EMC1 encodes a highly conserved protein of 993 amino acids whose yeast ortholog was recently proposed to function in unfolded protein response (UPR) and/or endoplasmic reticulum-associated degradation (ERAD). Deletion of the gene in yeast and C. elegans leads to slow growth (reduced fitness), and studies using genetic approaches or affinity capture in yeast, human and flies have revealed interactors of EMC1 involved in multiple pathways, including cell cycle, secretory pathway, UPR, ERAD, ion transport, cytoskeleton, transcription factors, cell signaling and mitochondrial electron transfer. Accumulated evidence on the requirement of UPR components for tumor growth and maintenance besides potential involvement of human EMC1 in cancer as suggested by global gene-expression analyses prompted us to investigate the role of this protein in breast cancer progression. Using antibodies raised, in our laboratory, against the N-terminal half of human EMC1, we showed staining mostly restricted to the basal layer of mammary epithelium in normal tissues, whereas in breast cancer tissues strong staining especially of what appears to be invasive cells and associated vasculature was observed. Additionally, using a tissue microarray with 96 samples of invasive primary breast tumor, we observed staining for EMC1 predominantly in zones of invasion and of variable levels of intensity, that we classified in weak, moderate and strong. Most cases (80/96, 83%) showed moderate to strong intensity, and strong expression was more frequent in tumors of grade II. Also, we observed a positive correlation of EMC1 with estrogen and progesterone receptor expression. Furthermore, we stably transfected SKBR-3 cells, which bear HER-2 gene amplification, with full length EMC1 cloned into the pcDNA3 vector, and protein overexpression was confirmed by immunostaining and qRT-PCR. SKBR-3 cells, which have a typical epithelial feature of cuboidal shape and grow grouped together with one another, underwent a noticeable morphological change after EMC1 overexpression, characterized by a more flattened, mesenchymal-like morphology and sparse distribution. Prominent filopodia, revealed by phalloidin labeling, was also observed after EMC1 exogenous expression. Additionally, EMC1 overexpression also enhanced motility and proliferation of SKBR-3 cells through ERK1/2 activation. Citation Format: Roberto Augusto Silva Molina, Rodrigo Ribeiro Silva, Josane Freitas Souza, Milene Mantovani Lopes, Daniel Guimaraes Tiezzi, Enilza Maria Espreafico. EMC1/KIAA0090 overexpression enhances proliferation and motility in breast cancer cells. [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 C6.

Endoplasmic Reticulum Membrane Complex protein 1 (EMC1), also named KIAA0090, was recently identified as part of a complex with six proteins (EMC1-EMC6) proposed to participate in the folding/maturation of membrane proteins, but the mechanisms remains unclear. High throughput studies reveal that EMC1 gene is up-regulated in many types of cancer and up-regulation correlates to poor survival rates. It has been known that there is a close relationship between proteins involved in the unfolded protein response (UPR) and tumor maintenance. Here, we investigated the involvement of EMC1 in breast cancer cell proliferation and migration. We showed by qPCR that EMC1 gene is overexpressed in breast cancer cell lines in comparison to immortalized epithelial breast cells. Next, we stably overexpressed EMC1 in MCF-7 and SKBR-3 cell lines. Overexpression led to an increase in proliferation rates, clonogenic capacity, and migration in wound-healing assays. Consistently, EMC1 knockdown in SKBR-3 cells led to a decrease of cell migration and clonogenic capacity. Furthermore, we assessed by Fluo3 the involvement of EMC1 in the regulation of intracellular calcium levels in SKBR-3 cells in response to thapsigargin treatment, which inhibits the endoplasmic reticulum Ca2+ ATPase. SKBR-3 control cells showed an expected increment in cytosolic calcium levels following thapsigargin addition. Interestingly, cytosolic calcium increments were about 50% higher in EMC1 overexpressing cells and nearly 10-fold lower in knockdown cells, suggesting a role for EMC1 in the control of cellular calcium homeostasis. EMC1 could function in the maturation/assembly of calcium channels or calcium pumps, thereby promoting breast cancer cell migration and maintenance. Citation Format: Roberto Augusto Silva Molina, Rodrigo Ribeiro Silva, Roberta Ribeiro Costa, Silmara Reis Banzi, Enilza Maria Espreafico. EMC1 influences cellular calcium homeostasis and promotes breast cancer cell migration and proliferation. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B41.