Characterization of the timing and prevalence of receptor tyrosine kinase expression changes in oesophageal carcinogenesis

Despite being common in epithelial malignancies, the timing of receptor tyrosine kinase (RTK) up-regulation is poorly understood and therefore hampers the identification of the receptor to target for effective treatment. We aimed to determine if RTK expression changes were early events in carcinogenesis. Oesophageal adenocarcinoma and its pre-invasive lesion, Barrett's oesophagus, were used for immunohistochemical analysis of the RTK panel, EGFR, ErbB2, ErbB3, Met, and FGFR2, by utilizing a cohort of patients with invasive disease ($n = 367$) and two cohorts with pre-invasive disease, one cross-sectional ($n = 110$) and one longitudinal in time ($n = 91$). The results demonstrated that 51% of oesophageal adenocarcinomas overexpressed at least one of the RTK panel, with 21% of these overexpressing multiple receptors. Up-regulation of RTK expression was an early event corresponding with low-grade dysplasia development (25% in areas without dysplasia versus 63% in low-grade dysplasia, $p < 0.001$). There was a trend for an increase in the prevalence of concomitant overexpression of multiple receptors as intestinal metaplasia progressed to low-grade dysplasia, 7% versus 10%; and from low-grade dysplasia to high-grade dysplasia, 10% versus 19% ($p = 0.06$ and 0.24, respectively). The timing of receptor up-regulation varied; FGFR, ErbB2, and Met overexpression occurred as dysplasia first developed, whilst EGFR overexpression was predominately seen in invasive disease and ErbB3 overexpression was uniformly rare. We provide evidence for a frequent and early role for multiple different RTKs in oesophageal carcinogenesis. Given the early timing of receptor deregulation, inhibiting RTKs in pre-invasive disease may also represent a novel and effective chemopreventive strategy. Copyright (c) 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.