Fibroblast growth factor signaling and chemotherapy resistance in esophageal adenocarcinoma cell lines

A185 Despite increasing use of chemotherapy in the clinical management of esophageal adenocarcinoma (EAC), outcomes remain poor largely due to the development of chemoresistance. To explore potential mechanisms, we studied the growth characteristics of two human EAC cell lines (Bic-1 and Seg-1) and one normal esophageal epithelial cell line (Het-1A), following repeated intermittent exposure to cisplatin, a chemotherapeutic agent widely used in current clinical practice. The chemosensitivity of surviving clones isolated at various cycles of drug exposure were studied under hypoxic conditions and in the presence of basic fibroblast growth factor (FGF-2), which is expressed at high levels in Seg-1 but undetectable in Bic-1. Signaling pathways were studied using selective pharmacologic inhibitors. Compared to HET-1A and Seg-1, Bic-1 cells were resistant to cisplatin, which is further enhanced by hypoxia and exogenous FGF-2 (10 ng/ml). The chemoprotective effect of FGF-2 was completely blocked by the specific FGF receptor (FGF-R) inhibitor, PD173074. The less specific FGF-R inhibitor SU5402 showed similar inhibition, but required significantly higher concentrations. Further blockade was achieved by two selective MEK-1 inhibitors (U0126 and PD9809), whereas no effect was seen with inhibitors of p38 Map kinase (SB203580 and SB202190), phospholipase C (U73122) or protein kinase C (chelerythrine chloride). Compared to parent cell lines, surviving clones were not more chemoresistant, but with increasing cycles of treatment, displayed gene expression profiles more similar to that of resistant Bic-1 cells, including a reduction of FGF-2 expression and up-regulation of FGF-R especially FGFR1. We conclude that FGFR signaling through the mitogen-activated protein kinase-extracellular signal regulated kinase (MAPK-ERK) pathway is important in acquire chemoresistance to cisplatin in EAC cell lines, and FGFR1 up-regulation may be a first step towards developing drug resistance. As FGF-2 was recently shown to have prognostic significance in human EAC, the stratification of patients to receive chemotherapy based on tumor FGFR expression, and the potential for modulation of chemotherapeutic efficacy represents a novel therapeutic strategy that warrants exploratory clinical study.