Modulation of the antigenic phenotype of human breast carcinoma cells by modifiers of protein kinase C activity and recombinant human interferons

Summary In the present study we have analyzed the effect of a synthetic protein kinase C (PKC) activator 3-(N-acetylamino)-5-(N-decyl-N-methylamino)-benzyl alcohol (ADMB) and the natural PKC-activating tumor-promoting agents 12-O-tetradecanoylphorbol 13-acetate (TPA) and mezerein on the antigenic phenotype of T47D human breast carcinoma cells. All three agents increased the surface expression of the tumor-associated antigen BCA 225 and various cellular antigens, including HLA class II antigens, intercellular adhesion molecule 1 (ICAM-1) and c-erbB-2. Expression of the same antigens was also upregulated to various extents in T47D cells by recombinant fibroblast (IFN) and immune (IFN) interferon. Shedding of BCA 225 from T47D cells was induced by TPA, mezerein, IFN and IFN, whereas ADMB did not display this activity. The ability of ADMB, TPA and mezerein to modulate the antigenic phenotype of T47D cells appears to involve a PKC-mediated pathway, since the PKC inhibitor, H-7, eliminates antigenic modulation. In contrast, the ability of IFN and IFN to enhance the synthesis, expression and shedding of BCA 225, as well as to enhance HLA class II antigens, c-erbB-2 and ICAM-1 expression, was either unchanged or modestly reduced by simultaneous exposure to H-7. Analysis of steady-state mRNA levels for HLA class I antigens, HLA class II-DR antigen, ICAM-1 and c-erbB-2 indicated that the ability of H-7 to inhibit expression of these antigens in TPA-, mezerein- and ADMB-treated cells was not a consequence of a reduction in the steady-state levels of mRNAs for these antigens. The results of the present investigation indicate that the biochemical pathways mediating enhanced antigenic expression in T47D cells induced by TPA, mezerein and the synthetic PKC activator ADMB are different from those induced by recombinant interferons. Furthermore, up-regulation of antigenic expression in T47D cells can occur by a PKC-dependent or a PKC-independent pathway.