Cyclooxygenase-2 is up-regulated by interleukin-1β in human colorectal cancer cells via multiple signaling pathways

Overexpression of cyclooxygenase-2 (COX-2) has been observed in human colorectal cancer. COX-2 expression in human tumors can be induced by growth factors, cytokines, oncogenes, and other factors. The mechanisms regulating COX-2 expression in human colon cancer have not been completely elucidated. We hypothesized that the proinflammatory cytokine interleukin-1β (IL-1β) mediates COX-2 expression in HT-29 human colon cancer cells. Treatment of HT-29 cells with IL-1β induced expression of COX-2 mRNA and protein in a time- and dose-dependent manner. Inhibitors of the extracellular signal-regulated kinase 1/2, c-Jun NH₂-terminal kinase, P38 mitogen-activated protein kinase, and nuclear factor-κB (NF-κB) signaling pathways blocked the ability of IL-1β to induce COX-2 mRNA. In contrast, Wortmannin, a phosphoinositide 3-kinase inhibitor upstream of protein kinase B/Akt, led to a slight increase in COX-2 mRNA expression after IL-1β treatment. Electrophoretic mobility shift assay on nuclear extracts demonstrated that IL-1β induced NF-κB DNA binding activity in HT-29 cells, and the activated NF-κB complex was eliminated after treatment with an inhibitor of NF-κB. Supershift assay indicated that the two NF-κB subunits, p65 and p5O, were involved in activation of NF-κB complex by IL-1β stimulation. The stability of COX-2 mRNA was not altered by IL-1β to treatment. These data demonstrate that IL-1β induces COX-2 expression in HT-29 cells through multiple signaling pathways and NF-κB.