EGF receptor antagonism inhibits in vivo angiogenesis and produces a survival benefit in pancreatic adenocarcinoma

Abstract

Purpose. The purpose of this study was to evaluate epidermal growth factor receptor (EGFR) inhibition as treatment for pancreatic adenocarcinoma and to correlate biologic activity of EGFR with vascular endothelial growth factor (VEGF) and tumor angiogenesis. Methods. In vitro, HPAC, a moderately differentiated pancreatic cancer cell line, was assayed for EGFR gene and gene product using rtPCR and immunohistochemistry (IHC). In vitro growth kinetics with erlotinib, a small molecule tyrosine kinase inhibitor specific for EGFR, were determined at 50 and 100 μM concentrations. In vivo, 38 nude mice underwent orthotopic implantation of 10 6 HPAC cells and were randomized to (1) control (vehicle only), or (2) erlotinib (100 mg/kg/QD ip). IHC staining for EGFR, activated EGFR, VEGF, and CD31 was undertaken. Serum VEGF production in control and erlotinib-treated mice was evaluated by ELISA. Results. HPAC expressed both gene and gene product for EGFR. In vitro inhibition of tumor growth was significant at 48 and 72 h ( P < 0.05, fig. Inset). Erlotinib-treated mice demonstrated a survival advantage, reduced tumor volume, weight, microvessel density, and decreased incidence of ascites, jaundice, and metastasis as compared to control (all P < 0.01). IHC showed decreased expression of EGFR, activated EGFR, and VEGF in erlotinib-treated mice. Conclusion. EGFR antagonism offers an in vivo survival benefit through EGFR inactivation and reduction in overall tumor angiogenesis possibly through decreased VEGF production.