Abstract
Esophageal cancer is the sixth most common cause of cancer‐related death worldwide. Because of very poor 5‐year survival new therapeutic approaches are mandatory. Erlotinib (Tarceva™), an inhibitor of epidermal growth factor receptor tyrosine kinase (EGFR‐TK), potently suppresses the growth of various tumors but its effect on esophageal carcinoma, known to express EGFR, remains unexplored. We therefore studied the antineoplastic potency of erlotinib in human esophageal cancer cells. Erlotinib induced growth inhibition of the human esophageal squamous cell carcinoma (ESCC) cell lines Kyse‐30, Kyse‐70 and Kyse‐140, and the esophageal adenocarcinoma cell line OE‐33, as well as of primary cell cultures of human esophageal cancers. Combining erlotinib with the EGFR‐receptor antibody cetuximab, the insulin‐like growth factor receptor tyrosine kinase inhibitor tyrphostin AG1024, or the 3‐hydroxy‐3‐methylglutaryl coenzyme. A reductase (HMG‐CoAR) inhibitor fluvastatin resulted in additive or even synergistic antiproliferative effects. Erlotinib induced cell cycle arrest at the G1/S checkpoint. The erlotinib‐mediated signaling involved the inactivation of EGFR‐TK and ERK1/2, the upregulation of the cyclin‐dependent kinase inhibitors p21^Waf1/CIP1^ and p27^Kip1^, and the downregulation of the cell cycle promoter cyclin D1. However, erlotinib did not induce immediate cytotoxicity or apoptosis in esophageal cancer cells. The inhibition of EGFR‐TK by erlotinib appears to be a promising novel approach for innovative treatment strategies of esophageal cancer, as it powerfully induced growth inhibition and cell cycle arrest in human esophageal cancer cells and enhanced the antineoplastic effects of other targeted agents. © 2005 Wiley‐Liss, Inc.