Epidermal growth factor receptor and HER-2/neu status by immunohistochemistry and fluorescence in situ hybridization in adenocarcinomas of the biliary tree and gallbladder

Summary

Adenocarcinomas of the biliary tract and gallbladder are aggressive tumors with a poor prognosis. Standard chemotherapy often offers minimal benefit. Because epidermal growth factor receptor and HER-2/neu antagonists have been successfully used in adenocarcinomas from other sites, their use in cholangiocarcinoma can be potentially beneficial. This study examines the epidermal growth factor receptor and HER-2/neu expression and the epidermal growth factor receptor gene copy number in biliary tract adenocarcinomas. Fifty-one formalin-fixed, paraffin-embedded cases of adenocarcinomas (26 intrahepatic, 19 extrahepatic, 6 gallbladder) were stained with monoclonal antibodies against epidermal growth factor receptor and HER-2/neu. Fluorescence in situ hybridization analysis was performed in 37 cases using probes directed against epidermal growth factor receptor and centromeric region of chromosome 7. Epidermal growth factor receptor expression was present in 41 (80%) cases, with moderate or strong epidermal growth factor receptor staining in 30 (59%) cases. HER-2/neu was positive in 2 (4%) cases. Fluorescence in situ hybridization analysis showed gain in epidermal growth factor receptor gene copy number in 17 (46%) tumors. Of the latter, 1 showed gene amplification, whereas all others showed gain in chromosome 7, indicating balanced polysomy. Epidermal growth factor receptor overexpression by immunohistochemistry correlated significantly with epidermal growth factor receptor copy number by fluorescence in situ hybridization (P = .02). HER2/neu expression is uncommon in these tumors.

Introduction

Cholangiocarcinoma is an aggressive tumor with an extremely poor prognosis. The 5-year survival rates are 10% to 40% for resectable tumors and less than 5% for unresectable disease [1], [2]. The worldwide incidence of these tumors is increasing [3]. Adenocarcinomas of the gallbladder also have a poor prognosis, with median overall survival of 10 months and 5-year survival of less than 30% [4]. Surgical resection is the only potentially curative option for these tumors. Systemic chemotherapy using 5-fluorouracil combined with cisplatin, and gemcitabine can improve the quality of life; but the impact on survival is minimal [1], [2], [5], [6]. New modalities of therapy need to be explored for these tumors to improve patient outcome.

Bile acids can activate epidermal growth factor receptor (EGFR), which in turn induces COX-2 expression via MAP-kinase cascade that may play a role in progression of cholangiocarcinoma [7]. Inhibition of EGFR signaling pathway activates apoptosis, inhibits angiogenesis, and induces antimetastatic properties [8]. The efficacy of EGFR antagonists like small-molecule tyrosine kinase inhibitors (EGFR-TKI) and anti-EGFR antibodies has been demonstrated in many tumors [8], [9], [10]. Cetuximab and panitumumab, monoclonal antibodies to EGFR, have been approved by the US Food and Drug Administration for colorectal carcinoma [10], [11]. Cetuximab and gefitinib, a TKI, have been approved for non–small cell lung cancer [10].

EGFR inhibition leads to suppression of tumor growth in cholangiocarcinoma cell lines and chimeric mouse model [12]. Addition of cetuximab to gemcitabine or radiation has yielded improved results in preliminary studies [13], [14], [15]. Therapeutic benefit has been reported with erlotinib in advanced cholangiocarcinomas in a phase II trial [16].

Several studies have demonstrated somatic mutations [17] and immunohistochemical overexpression of EGFR in cholangiocarcinomas and gallbladder adenocarcinomas [16], [18], [19], [20], [21], [22], [23], [24], [25]. EGFR gene amplification is a rare event in these tumors [14], [23]; however, the increase in EGFR copy number without amplification has not been systematically studied in these tumors This study examines the EGFR expression by immunohistochemistry and EGFR gene copy number by fluorescence in situ hybridization (FISH) in cholangiocarcinomas and gallbladder adenocarcinomas. The correlation of EGFR expression and gene copy number with clinical and pathologic parameters is examined. Because there are varying results in the cholangiocarcinoma literature regarding the status of HER-2/neu [23], [24], [26], [27], [28], another receptor in the EGFR family, we also evaluated HER-2/neu expression by immunohistochemistry in these tumors.