EGF-dependent enhancement of invasive ability in squamous cell carcinoma of the breast.

Abstract

Abstract Abstract #2061 The factors promoting the clinical aggressiveness of squamous cell carcinoma of the breast is still not well understood. In order to examine whether the mechanism of cell motility is involved in the aggressive behavior of squamous cell carcinoma, we established a squamous cell carcinoma cell line from breast primary (HBC 9) and assayed its invasiveness. The number of HBC9 cells migrating through matrigel was significantly increased by stimulation with epidermal growth factor (EGF). This enhancement of cell motility was distinctly detected in comparison with four ductal carcinoma cell lines (MCF7, BT474, HBC5, and MDA-MB-231). EGF stimulation also induced surface protrusions of HBC9 cells. To examine the interaction between Arp2/3 complex and N-WASP which is the final intracellular signal of invadopodia formation that is downstream from EGF stimulation, we observed surface protrusion of HBC 9 by laser microscopy. Co-localization of Arp2 and N-WASP was detected with actin polymerization visualized by phalloidin. Furthermore, the localization of cortactin was found to agree with that of N-WASP and Arp2/3 complex in the invadopodia. The cortactin gene copy number was evaluated using real time PCR by comparison between 12 DNA samples extracted from primary mammary squamous cell cancer tissue and those from corresponding normal breast tissue. A higher level of cortactin was detected in cancer tissue than in normal tissue in 10 cases (83%). At a protein level, intense immunostaining of cortactin was detected in all 12 cases, among which expression was confirmed in 2 cases by Western blot analysis. These results suggest that one of the causes of clinical aggressiveness of squamous cell carcinoma of the breast is the enhancement of cell motility by invadopodial formation. Overexpression of cortactin may result in the formation of invadopodium. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2061.