Tumor-promoting phorbol diesters inhibit in vitro antibody synthesis

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate prevents the synthesis of antibodies directed against sheep red blood cells in an in vitro system. The inhibitory effect of 3 phorbol diesters on this immune response was positively correlated with their tumor-promoting activity. The effect did not appear to be mediated through the inhibition of cell proliferation. Results suggest that the tumor promoter may alter the differentiation of the precursor cells to antibody-producing cells.