Docosahexaenoic acid-containing phosphatidylethanolamine enhances HL-60 cell differentiation by regulation of c-jun and c-myc expression

18:1/docosahexaenoic acid (DHA)-containing phosphatidylethanolamine (PE) enhanced cell differentiation and growth inhibition of HL-60 induced by dibutyryl cAMP (dbcAMP) in a dose-dependent manner. The combined treatment of 200 microM dbcAMP and 50 microM 18:1/DHA-PE increased the NBT reducing activity, which is as an indicator of cell differentiation, to more than 75% from 40% of cells treated with 200 microM dbcAMP alone. In HL-60 cells treated with 50 microM 18:1/DHA-PE and 200 microM dbcAMP for 24 h, the expression level of c-Jun mRNA and c-Jun protein were remarkably elevated compared to cells treated with dbcAMP alone. In contrast, there was no difference in the expression levels of c-Fos mRNA and c-Fos protein between the combination of 18:1/DHA-PE + dbcAMP or dbcAMP alone. On the Other hand, the combine treatment of 18:1/DHA-PE and dbcAMP markedly reduced the expression level of c-Myc oncogene during 48 h incubation. The decreases of c-Myc mRNA by 18:1/DHA-PE and/or dbcAMP was correlated with growth inhibition effect. Thus, 18:1/DHA-PE might enhance dbcAMP-induced HL-60 cell differentiation and growth inhibition by regulation of c-Jun and c-Myc mRNA and their products.