The relationship between tumor promoter binding and Epstein-Barr virus induction in human lymphoblastoid cell lines

The tumor promoter TPA (12-0-tetradecanoyl-phorbol-13-acetate) efficiently induces the synthesis of Epstein-Barr virus (EBV) antigens in EBV-genome-harboring human lymphoblastoid cells. We attempted to obtain information on the binding of TPA to cells and on the relationship between TPA-binding and EBV induction by the use of tritiated TPA (3H-TPA). Our data show: (1) In the absence of cells TPA can bind to serum completely within 60 minutes. (2) Cells can compete for a proportion of serum-bound TPA. (3) Binding of TPA to cells reaches equilibrium within 60 minutes and is higher at 37 degrees than 0 degrees C. In the absence of serum, the rate of binding is about twice as high as in the presence of serum. (4) Dissociation of TPA from cells also seems to be rapid. When the cells are incubated with cold TPA after prior treatment with 3H-TPA, followed by washing, a much higher rate of release of labeled TPA is observed than in cultures to which fresh medium is added exclusively. Dissociation is higher in the presence of serum than in the absence of it. If radiolabeled cells are analyzed after serial washing, the rate of cell-associated/noncell-associated radioactivity indicates that the proportion of molecules required for EBV induction is dissociated rapidly.