Epinephrine stimulates esophageal squamous-cell carcinoma cell proliferation via beta-adrenoceptor-dependent transactivation of extracellular signal-regulated kinase/cyclooxygenase-2 pathway

Abstract

Esophageal cancer is the sixth leading causes of cancer-related death in the world. It is suggested that beta-adrenoceptor is involved in the control of cell proliferation, but its role in the pathogenesis of esophageal cancer remains unknown. We therefore studied the role of beta-adrenergic signaling in the regulation of growth of an esophageal squamous-cell carcinoma cell line HKESC-1. Results showed that both beta(1)- and beta(2)-adrenoceptors were expressed in HKESC-1 cells. Stimulation of beta-adrenoceptors with epinephrine significantly increased HKESC-1 cell proliferation accompanied by elevation of intracellular cyclic AMP levels, which were abolished by beta(1)- or beta(2)-selective antagonists. Epinephrine also increased extracellular signal-regulated kinase-1/2 (ERK1/2) phosphorylation as well as cyclooxygenase-2 (COX-2) and cytosolic phospholipase A(2) expression, which were blocked by beta(1)- or beta(2)-selective antagonists. Moreover, epinephrine increased cyclin D(1), cyclin E(2), cyclin-dependent kinase (CDK)-4, CDK-6, and E(2)F-1 expression and retinoblastoma protein phosphorylation at Ser807/811, all of which were abrogated by beta(1)-adrenoceptor antagonist. Furthermore, epinephrine increased the expression of vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR)-1 and -2 in a beta(2)-adrenoceptor-, mitogen-activated protein kinase/ERK kinase (MEK)-, and COX-2-dependent manner. MEK or COX-2 inhibitor also significantly inhibited HKESC-1 cell proliferation induced by epinephrine. Collectively, we demonstrate that epinephrine stimulates esophageal squamous-cell carcinoma cell proliferation via beta-adrenoceptor-dependent transactivation of ERK/COX-2 pathway. Stimulation of beta(1)- and beta(2)-adrenoceptors also elicits a differential response on the expression of cell cycle regulators. These novel findings may shed new light on the understanding of beta-adrenergic signaling in the control of esophageal cancer cell growth.