Detection of antitumor promoting activity in Raji cells carrying Epstein-Barr virus genome by immunoblotting analysis.

Extract of Raji cells treated with sodium n-butyrate (1 mM) and a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA, 40 ng/ml), was analyzed by immunoblotting using ten human sera with different antibody titers against Epstein-Barr virus early antigens. Two human sera reacted with one induced polypeptide of 48 kDa and its induction was inhibited by curcumin (4 micrograms/ml), an antitumor promoter from turmeric. A mouse antiserum against P3HR-1 cells treated with TPA and sodium n-butyrate also detected the 48-kDa polypeptide in Raji cells treated with TPA at concentrations of 2.5 to 80 ng/ml. These results indicate that the immunoblotting analysis can be used in a confirmation test for detection of antitumor promoting activity.