12-O-TETRADECANOYLPHORBOL-13-ACETATE (TPA) DOWN-REGULATES EXPRESSION OF CD30 IN ERYTHROLEUKEMIA CELL-LINE K562

CD30, a member of the tumour necrosis factor/nerve growth factor recep tor superfamily, has been thought to have pleiotropic functions on imm une response. However, there has been only a little information about the mechanism of CD30 expression. In this study, modulation of the CD3 0 molecule was investigated by the treatment with 12-O-tetradecanoyl-p horbol-13-acetate (TPA). When cultures were supplemented with TPA, CD3 0 transcript was downregulated in a dose-and time-dependent manner in the erythroleukemia cell line K562. Half reduction of CD30 transcript, precursor protein and surface protein was at 3 h, 6 h, and 40 h, resp ectively, by Northern blot and Western blot analyses. This consecutive reduction of both the transcript and proteins suggests that TPA direc tly inhibits the transcriptional step of CD30, and subsequently CD30 m olecules would decrease on the cell surface. To determine whether the protein kinase C (PKC) pathway is involved in this reduction, a PKC in hibitor, 10 mu M H-7, was added to the K562 culture. The addition of H -7 recovered the inhibitory effect of TPA, indicating that PKC is invo lved in the transcription of CD30. When either 2 mu g/ml actinomycin D or 20 mu g/ml cycloheximide was added simultaneously with TPA to the culture, the repressive effect of TPA on CD30 was abolished. These res ults showed that the repression would also partly involve ongoing mRNA and protein synthesis under TPA treatment. (C) 1997 John Wiley & Sons , Ltd.