Induction of B-cell differentiation antigens in interferon- or phorbol ester-treated Daudi cells is impaired by inhibitors of ADP-ribosyltransferase.

Treatment of the Daudi Burkitt lymphoma-derived cell line with human interferon alpha, which inhibits cell proliferation in this system, induces differentiation of these B-lymphoid cells into cells with a plasmacytoid phenotype. This differentiation, quantified by the appearance of surface antigens characteristic of mature plasma cells, is impaired by addition to the culture medium of the ADP-ribosyltransferase (ADPRT; EC 2.4.2.30) inhibitors 3-methoxybenzamide or 3-aminobenzamide. These agents also protect the cells against the inhibition of proliferation induced by low doses of interferon alpha. In contrast, the large inhibition of thymidine incorporation into DNA caused by interferon treatment is not affected by the ADPRT inhibitors. The phorbol ester phorbol 12-tetradecanoate 13-acetate induces the same plasma cell surface antigens that are induced by interferon treatment, and this effect is also impaired by the ADPRT inhibitors. These results suggest that interferons and phorbol esters share a mechanism of action that requires ADPRT activity. Protection of the cells against the antiproliferative effect of interferons by the ADPRT inhibitors suggests that growth inhibition may be a consequence of cell differentiation. In contrast, the inhibition of thymidine incorporation alone is not sufficient for the cessation of cell proliferation and is not a true reflection of the rate of DNA synthesis.