Biochem/physiol Actions Prostratin, an unusual non-tumorigenic phorbol ester, is an activator of protein kinase C (PKC) and also an activator of nuclear factor KB (NF-KB) mediated through activation of the IKKs (IKB kinases). Prostratin exhibits potent in vitro activity by inducing HIV expression in latently infected cell lines and primary cells, thus antagonizing HIV latency. Activation of PKC and NF-kB has been proposed as the mechanism of action. Prostratin also inhibits HIV entry into target cells by down-regulating CD4 and CXCR4 receptors.