- Bryostatin 1, an activator of protein kinase C, mimics as well as inhibits biological effects of the phorbol ester TPA in vivo and in vitro. Gschwendt, M., Fürstenberger, G., Rose-John, S., Rogers, M., Kittstein, W., Pettit, G.R., Herald, C.L., Marks, F. Carcinogenesis (1988)