Syntenin is overexpressed and promotes cell migration in metastatic human breast and gastric cancer cell lines Tae Hyeon Koo 1,3 , Jung-Joon Lee 1 , Eun-Mi Kim 1 , Kyu-Won Kim 2 , Han Do Kim 3 and Jeong-Hyung Lee* ,1 1 Anti-Cancer Research Laboratory, Korea Research Institute of Bioscience and Biotechnology, P.O. Box 115, Yuseong, Daejeon 305-600, Korea; 2 Research Institute of Pharmaceutical Science, College of Pharmacy, Seoul National University, Seoul 151-742, Korea; 3 Department of Molecular Biology, Pusan National University, Pusan 609-735, Korea Two human breast cancer cell lines of diering invasive and metastatic potential, MDA-MB-435 and MCF7, were examined using subtractive suppression hybridiza- tion in a search for any genes associated with metastasis. Of the 17 cDNAs identi®ed as being dierentially expressed genes, it was determined that syntenin was overexpressed in metastatic MDA-MB-435 cells. Ex- pression analysis showed that the expression level of syntenin was well correlated with invasive and metastatic potential in various human breast and gastric cancer cell lines. Moreover, gastric tumor tissues exhibited a much higher syntenin mRNA expression than their normal counterparts. Syntenin-transfected MCF7 cells migrated more actively, and showed an increased invasion rate relative to vector-transfectants or parental MCF7 in vitro, without evidencing any eect on the adhesion to ®bronectin, type I collagen and laminin. Similarly, the forced expression of syntenin to human gastric cancer cell line Az521 increased its migratory and invasive potential in vitro. Syntenin-expressing MCF7 cells were associated with the appearance of numerous cell surface extensions and with pseudopodia formation on collagen I, suggesting that syntenin may be involved in the signaling cascade to actin-reorganization. Mutation study sug- gested that PDZ2 domain of syntenin could be an essential role in its stimulatory eect on the cell migration. This is the ®rst demonstration that syntenin, a PDZ motif-containing protein, can be overexpressed during the metastatic progression of human breast and gastric cancer cells and that it can function as a metastasis-inducing gene. Oncogene (2002) 21, 4080 ± 4088. doi:10.1038/sj.onc. 1205514 Keywords: syntenin; migration; invasion; breast cancer; gastric cancer Introduction Since it was ®rst recognized that tumors had the ability to invade adjacent tissues and spread to distant organs, extensive research has been performed, expanding the body of knowledge concerning this basic hallmark of malignancy. Such spread and distant settlement of tumor cells is the major cause of human cancer deaths (Sporn, 1996). With their capability for invasion and metastasis cancer cells are able to escape the primary tumor mass and colonize new terrain in the body. It is now widely accepted that the stepwise malignant progression of human cancer is a consequence of multistage genetic alterations that have accumulated in cells (Yokota, 2000). Thus, to understand the mole- cular mechanisms of tumor progression, it is essential to identify the genes whose alterations have accumu- lated during the progression of the cancer as well as whose expression is responsible for the acquisition of metastatic potential in cancer cells. Various methods for comparing patterns of gene expression have been described in the literature (Byers et al., 2000). Of these, subtractive suppression hybridization (SSH) represents a simple and ecient technique for generating cDNAs that are highly enriched for dierentially expressed genes of both high and low abundance (Diatchenko et al., 1996). In the present study, we used SSH to identify metastasis- related genes by comparing their dierential gene expression pro®les between metastatic MDA-MB-435 and non-metastatic MCF7 breast cancer cell lines. Nine and eight dierent genes were identi®ed as being overexpressed in MCF7 and MDA-MB-435 cells, respectively. Of these, we ®rstly identi®ed syntenin as an overexpressed gene in MDA-MB-435 cells. Syntenin has two PDZ domains and interacts with the COOH termini of syndecans, class B ephrins, EphA7, pro-TGF-a, neurexins, neurofascin, and the anion exchanger AE2 (Grootjans et al., 1997, 2000; Cowan et al., 2000; Torres et al., 1998; Lin et al., 1999; Fernandez- Larrea et al., 1999; Koroll et al., 2001). Syntenin has been reported to be a component of cell adhesion sites and of micro®laments (Zimmermann et al., 2001), and it has also been identi®ed as a major structural component of apical early endosomes (Fialka et al., 1999). Oncogene (2002) 21, 4080 ± 4088 ã 2002 Nature Publishing Group All rights reserved 0950 ± 9232/02 $25.00 www.nature.com/onc *Correspondence: J-H Lee; E-mail: jhlee36@mail.kribb.re.kr Received 13 August 2001; revised 18 March 2002; accepted 22 March 2002