EMS1

Oncogene EMS1
Cortactin

Gene: EMS1 maps to 11q13, a region frequently amplified in breast cancer. Three other genes located in this region are INT-2, HST-1, and CCND1, coding for FGF3, FGF4, and cyclin D1, respectively.
mRNA: size: 3.8 kb (Campbell D.H. et al., 1996).
Protein: EMS1 gene product cortactin is a 80/85-kDa c-src tyrosine kinase substrate. Cortactin is overexpressed in carcinoma cells with an amplification of 11q13 and is found in 2 forms, designated p80 and p85. Their N-terminal portion consists of 5(p80) or 6(p85) repeats of a 37 amino acid motif predicted to form a helix-turn-helix structure. Cortactin binds filamentous actin (F-actin) via this repeat region (Wu H. and Parsons J.T., 1993). At the C-terminus of the protein is an src homology (SH3) domain. SH3 domains are frequently found in signalling molecules (c-src, Grb2,...) as well as in cytoskeletal proteins, such as alpha-spectrin, and bind to short proline-rich sequences within the target molecule (Pawson T., 1995). Therefore, cortactin might play a role in linking signalling events to cytoskeletal reorganisation.
It was shown that p85 is produced from p80 by posttranslational modification. Treatment of cells with epidermal growth factor or vanadate caused conversion of p80 to p85 and enhanced phosphorylation of the p85 form. Both overexpression and posttranslational modification of cortactin coincided with its redistribution from the cytoplasm to cell-matrix contact sites, implying a role for cortactin in the modulation of cellular adhesive properties (van Damme H. et al., 1997).

Cell lines:
- EMS1 gene amplification and expression were characterized in a panel of breast cancer cell (BCC) lines. The EMS1 gene was amplified 2-fold or greater in MDA-MB-134 (9.5-fold amplification), -157, -175 (5-fold amplification), -453, ZR-75-1, and MCF-7 BCC. Except for MDA-MB-157 BCC, these cell lines over-expressed EMS1 mRNA relative to normal breast epithelial cells to levels corresponding to that of the respective gene amplification. They also exhibited increased levels of EMS1 protein. All other BCC lines studied (BT-20, -474, -483, -549, DU-4475, HBL-100, Hs578T, MDA-MB-231, -330, -361, -436, -468, SK-BR-3, T-47D) did not exhibit EMS1 gene amplification or increased EMS1 mRNA levels. Of these, BT-474 was the only one containing increased EMS1 protein levels. EMS1 and CCND1 genes both map to 11q13. They were found to be co-amplified in MDA-MB-134, -175, -453, and ZR-75-1, whilst 4 BCC lines showed amplification of one gene alone: MDA-MB-157 and MCF-7 (EMS1) and MDA-MB-330 and -361 (CCND1, see Buckley M.F. et al., 1993). The level of tyrosine phosphorylation of EMS1 was variable among BCC lines, with a high level in BT-474 and T-47D cells, which exhibited relatively high total src activity coupled with expression of both c-fyn and c-yes. These observations demonstrate gene amplification to be the predominant mechanism underlying EMS1 over-expression in human BCC lines and identify tyrosine phosphorylation as a further level at which regulation of this protein may be perturbed (Campbell D.H. et al., 1996).

- Invasive BCC have the ability to extend membrane protrusions, invadopodia, into the extracellular matrix. These structures are associated with sites of active matrix degradation, an event correlated with invasive potential. Cortactin, paxillin and protein kinase C-µ (PKCµ) were co-immunoprecipitated as a complex from invadopodia-enriched MDA-MB-231 BCC membranes. This complex of three proteins was also observed in two other highly invasive, Hs578T and MCF-7/ADR, but not in four less invasive BCC lines (MCF-7, SKBR3, MDA-MB-453, MDA-MB-468). In MDA-MB-231 BCC, microinjection of polyclonal anti-cortactin antibodies blocked matrix invasion at invadopodia, supporting the hypothesis that cortactin has a direct role in invasive behavior of BCC (Bowden E.T. et al., 1999).

Tumors:
- In breast carcinomas, the majority of tumors showing an 11q13 overamplification also show an increase in expression of cortactin, and this has been correlated with poor patient prognosis (Schuuring E. et al., 1992).

Bowden E.T. et al. (1999) An invasion-related complex of cortactin, paxillin and PKCµ associates with invadopodia at sites of extracellular matrix degradation. Oncogene 18, 4440-4449.
Buckley M.F. et al. (1993) Expression and amplification of cyclin genes in human breast cancer. Oncogene 8, 2127-2133.
Campbell D.H. et al. (1996) Expression and tyrosine phosphorylation of EMS1 in human breast cancer cell lines. Int. J. Cancer 68, 485-492.
Hui R. et al. (1998) EMS1 gene expression in primary breast cancer: relationship to cyclin D1 and oestrogen receptor expression and patient survival. Oncogene 17, 1053-1059.
Pawson T. (1995) Protein modules and signalling networks. Nature 373, 573-580.
Schuuring E. et al. (1992) Identification and cloning of two overexpressed genes, U21B31/PRAD1 and EMS1, within the amplified chromosome 11q13 region in human carcinomas. Oncogene 7, 355-361.
Schuuring E. et al. (1993) The product of the EMS1 gene, amplified and overexpressed in human carcinomas, is homologous to a v-src substrate and is located in cell-substratum contact sites. Mol. Cell. Biol. 13, 2891-2898.
Schuuring E. et al. (1998) Characterization of the EMS1 gene and its product, human cortactin. Cell Adhes. Commun. 6, 185-209.
van Damme H. et al. (1997) The redistribution of cortactin into cell-matrix contact sites in human carcinoma cells with 11q13 amplification is associated with both overexpression and post-translational modification. J. Biol. Chem. 272, 7374-7380.
Wu H. and Parsons J.T. (1993) Cortactin, an 80/85-kilodalton pp60src substrate, is a filamentous actin-binding protein enriched in the cell cortex. J. Cell Biol. 120, 1417-1426.