The mechanism of COX-2 regulating HERG channel in gastric cancer cells

Abstract

Objectives: To elucidate the signal transduction pathway, by which cyclooxygenase-2 (COX-2) regulates human erg-related gene (HERG) current in gastric cancer cells. Methods: The HERG mRNA, protein and current in gastric cancer cells transfected with or without COX-2 antisense vector were measured by RT-PCR, Western blot and patch-clamp, respectively. Cyclic adenosine monophosphate (cAMP) concentration in gastric cancer cells transfected with or without COX-2 antisense vector was measured by ELISA. Results: Transfection with COX-2 antisense vector did not alter the expression of HERG mRNA and protein, but it diminished the amplitude of HERG current in gastric cancer cells (p < 0.05). The cAMP concentration in gastric cancer cells transfected with COX-2 antisense vector was lower than that in parental gastric cancer cells (p < 0.05). COX-2 inhibitor and PGE2 had infl uence on the HERG current in gastric cancer cells. COX-2 inhibitor reduced the amplitude of HERG current in gastric cancer cells and PGE2 enhanced the amplitude. However, in gastric cancer cells transfected with HERG mutant deleting cAMP-binding domain, both COX-2 inhibitor and PGE2 did not show signifi cant effects on HERG current. cAMP agonist enhanced the amplitude of HERG current and cAMP antagonist reduced the amplitude in gastric cancer cells. Both agonist and antagonist of cAMP had no signifi cant effect on HERG current in gastric cancer cells transfected with HERG mutant deleting cAMP binding domain. PKA inhibitor did not infl uence the HERG current whether in parental gastric cancer cells or in gastric cancer cells transfected with HERG mutant. Conclusions: COX-2 regulates HERG current through its catalytic product PGE2, which alters cAMP level in gastric cancer cells. cAMP interacts with HERG protein by binding with cAMP-binding domain of HERG protein and exerts impact on HERG current. PKA does not participate in this process.