A novel isoform of human fibroblast growth factor 8 is induced by androgens and associated with progression of esophageal carcinoma

Human esophageal carcinomas occur more frequently in males, suggesting that androgens may play a role in the regulation of gene expression associated with malignant transformation. We previously established an androgen-sensitive squamous cell carcinoma line, KSE-1, from a male patient with esophageal cancer; recently a novel isoform of human fibroblast growth factor 8 (FGF8f, isoform FGF8b) was identified and expressed following androgen stimulation of KSE-1 cells. The predicted amino acid sequence of FGF8f contained an additional 29 amino acids when compared to FGF8b. Flutamide, an androgen antagonist, inhibited both FGF8b and FGF8f transcription in a dose-dependent manner. Tissue analysis from tumors revealed FGF8b expression in 24 of 41 male, but in 0 of 9 female esophageal carcinomas (58.5%), and none in adjacent normal esophageal mucosa. In addition, FGF8f was detected in 9 of 24 FGF8b-positive tumors (37.5%), and this observation was significantly associated with a poor prognosis (P < 0.001). Our observations suggest that androgenic exposure will induce FGF isoforms in tumor cells, and expression of these growth factors is associated with the prevalence and prognosis of esophageal carcinoma in males.