EGFR activation results in enhanced expression of COX-2 and tumor growth through activation of β2-Adrenergic receptor in esophageal squamous cell carcinoma

We previously reported that epidermal growth factor (EGF)-induced esophageal cancer cell proliferation required transactivation of beta-adrenoceptor. In the present study, we further investigated whether beta(2)-adrenoceptor was involved in the modulation of cyclooxygenase-2 (COX-2) expression and cell proliferation by EGF in esophageal squamous cell carcinoma (ESCC). Human ESCC cell line KYSE-30 was treated with EGF, EGFR inhibitor (AG1478), beta(2)-selective antagonist (ICI-118,551) and highly selective cyclooxygenase-2 inhibitor (nimesulide). Cell survival was tested by MTT assay. The expression of COX-2 was detected by Western blot and real-time reverse transcription polymerase chain reaction (PCR). ESCC xenograft in nude mice was administered with EGF combining or not combining EGFR inhibitor, beta(2)-selective antagonist and cyclooxygenase-2 inhibitor. Tumor growth was observed and COX-2 expression was detected by Western blot and PCR. EGFR, beta(2)-adrenergic receptor and COX-2 was expressed in KYSE-30 cells. EGF stimulated KYSE-30 cell proliferation in a dose-dependent manner. AG1478, ICI-118,551, and nimesulide attenuated cell proliferation induced by EGF. AG1478 and ICI-118,551 also abrogated EGF-induced up-regulation of COX-2 expression in the mRNA and protein level. Animal model indicated that EGF significantly stimulated the growth of ESCC xenograft in nude mice, which was attenuated by AG1478, ICI-118,551, and nimesulide. Moreover, AG1478 and ICI-118,551 abrogated EGF-induced up-regulation of COX-2 expression in the tumor xenograft. These data provided the first evidence that EGFR activation resulted in enhanced expression of COX-2 and tumor growth through activation of beta(2)-adrenergic receptor in ESCC. This novel finding shed new light on combination of EGFR blocker and COX-2 inhibitor for the treatment of ESCC.