Increase in the synthesis of a Mr 32,000 protein in BALB/c 3T3 cells treated with tumor-promoting indole alkaloids or polyacetates.

The synthesis of a unique protein with a molecular weight of 32,000 (p32) in BALB/c 3T3 cells has been shown previously to increase after treatment with potent tumor-promoting phorbol esters (Hiwasa et al., Proc. Natl. Acad. Sci. U. S. A., 79: 1800, 1982). In the present study, two new classes of tumor promoters which are structurally different from phorbol esters were investigated for their potencies to enhance p32 synthesis. Teleocidin, dihydroteleocidin B, and lyngbyatoxin A, which are indole alkaloid tumor promoters, enhanced p32 synthesis to the same extent that 12-O-tetradecanoylphorbol-13-acetate did. However, no increase was observed by treatment with the biologically inactive hydrolysate of teleocidin. Polyacetate tumor promoters such as aplysiatoxin and debromoaplysiatoxin also stimulated p32 synthesis, but their effective concentrations were higher than those of 12-O-tetradecanoylphorbol-13-acetate. When 3T3 cells were treated with a combination of two of the three tumor promoters, TPA, teleocidin, and aplysiatoxin, no synergistic effect of p32 synthesis was observed. This implies that these tumor promoters enhance the synthesis of p32 through the same mechanism.