A Potent inhibitor of protein phosphatases 1 and 2A in numerous cell types. Does not affect activity of acid phosphatase, alkaline phosphatase and tyrosine phosphatase. Non-phorbol type tumor promoter. Induces apoptosis in human breast carcinoma cells (MB-231 and MCF-7) and in myeloid cells, but inhibits glucocorticoid-induced apoptosis in T-cell hybridomas.