In particular, we and others have recently reported that the overexpression of EGFR of oesophageal reference 2 SCC, partially accounted for by gene amplification, is found in 50�C70% (Itakura et al, 1994; Hanawa et al, 2006), and is indicative of a poor prognosis (Ozawa et al, 1989; Yano et al, 1991). Moreover, we showed that the overexpression of HER-2 in oesophageal SCC was found in 30.3% (Mimura et al, 2005b). These results indicated that oesophageal SCC shows a relatively high incidence of EGFR and/or HER-2 overexpression. There are several potential strategies for anti-HER family targeting. Two anti-HER family-targeting therapies that have been in clinical development are small-molecule EGFR tyrosine kinase inhibitors such as gefitinib (Ranson et al, 2002; Fukuoka et al, 2003) and humanised antibodies against the HER family represented by cetuximab and trastuzumab (Herbst and Hong, 2002; Needle, 2002).

There are many mechanisms that are thought to contribute to the antitumour activity of cetuximab and trastuzumab, including a direct inhibition of EGFR tyrosine kinase activity (Sato et al, 1983; Sliwkowski et al, 1999), the inhibition of cell cycle progression (Wu et al, 1995; Peng et al, 1996), and increased levels and activities of pro-apoptotic molecules (Wu et al, 1995; Cuello et al, 2001; Liu et al, 2001). We recently reported the application of trastuzumab for oesophageal SCC with the analysis of antibody-dependent cellular cytotoxicity (ADCC) mediated by trastuzumab (Mimura et al, 2005a). These results encourage us to apply a combination therapy of cetuximab and trastuzumab for oesophageal SCC, aiming at a synergistic effect.

Thus, it is important to identify how expressions of EGFR and HER-2 are distributed in oesophageal SCC and if the combination of cetuximab and trastuzumab has a synergistic antitumour effect against oesophageal SCC. In the present study, we investigated (a) the distribution of EGFR and HER-2 expression in oesophageal SCC detected by immunohistochemistry (IHC) and (b) the biological activity (antiproliferative effect, apoptosis-inducing activity, and ADCC) of cetuximab and trastuzumab against oesophageal SCC cell lines with various levels of EGFR and HER-2. MATERIALS AND METHODS Patients We examined 66 cases of primary oesophageal SCCs that were histologically diagnosed and treated in the First Department of Surgery, University of Yamanashi Hospital. The patients had not received irradiation or chemotherapy before Dacomitinib surgery. All patients had undergone oesophagectomy with two-field (n=39) or three-field (n=27) lymph node dissection between 1994 and 1999. The patients were classified using the tumour node metastasis (TNM) classification. The characteristics of the patients are shown in Table 1.