Epidermal growth factor induces expression of decay-accelerating factor inhuman colonic cancer cells via the mitogen-activated protein kinase pathway

The expression of decay-accelerating factor (DAF), a complement regulatory protein, is enhanced in colorectal cancer. In this study, to elucidate mech anisms for enhanced DAF expression, we studied the effects of growth factor s on DAF expression in HT-29 human colonic cancer cells. Cells were treated with epidermal growth factor (EGF), insulin-like growth factor-I, platelet -derived growth factor, and transforming growth factor-beta. DAF protein ex pression and mRNA expression were determined with enzyme immunoassay and No rthern blot analysis. The signaling pathways that target DAF expression in response to growth factor stimulation were characterized by using various I nhibitors of the signal transduction pathway. EGF induced significant incre ases in DAF protein and mRNA expression in HT-29 cells; the other growth fa ctors had a weak effect or no effect. The EGF-induced DAF expression was in hibited by mitogen-activated protein (MAP) kinase kinase inhibitor PD 98059 but not by phosphatidylinositol-3 kinase inhibitor, phospholipase Cy inhib itor, or protein kinase C inhibitor. When we analyzed the phosphorylation s tate of the MAP kinase by immunoblot analysis, phosphorylated p44/p42 MAP k inase was detected in EGF-stimulated HT-29 cells, and the addition of PD 98 059 abrogated the phosphorylation. These results indicate that EGF regulate s DAF expression in HT-29 cells via the signaling pathway that depends on t he activation of MAP kinase.