Estrogen Receptors in Regulating Cell Proliferation of Esophageal Squamous Cell Carcinoma: Involvement of Intracellular Ca²⁺ Signaling

Esophageal cancer is a deadly disease in the esophagus with a poor prognosis. Over 90 % of esophageal cancer is esophageal squamous cell carcinoma (ESCC) and its pathogenic mechanisms remain unclear. Epidemiology study found a strong gender difference with a sex ratio of 8–9:1 in favor of males, but the molecular mechanisms for so striking gender difference are poorly understood so far. In the present study, we demonstrated the expression of estrogen receptors in human ESCC cells. 17β-E2 but not 17α-E2 was found to dose-dependently suppress the cell proliferation of human ESCC cells, which was attenuated by estrogen receptor antagonist ICI1 82,780. Furthermore, 17β -E2 but not 17α-E2 10 nM markedly induced both intracellular Ca²⁺ release and extracellular Ca²⁺ entry into ESCC cells, which was again attenuated by estrogen receptor antagonist ICI182,780. Taken together, our data clearly demonstrate that estrogen exerts anti-proliferative action on human ESCC cells likely through estrogen receptor-Ca²⁺ signaling pathway, which may provide a reasonable explanation on the striking male predominance of ESCC.