Okadaic acid ammonium salt, a marine toxin, serves as an inhibitor of protein phosphatases (PP), displaying a higher affinity for PP2A (IC 50 =0.1-0.3 nM) alongside inhibitory effects on PP1 (IC 50 =15-50 nM), PP3 (IC 50 =3.7-4 nM), PP4 (IC 50 =0.1 nM), and PP5 (IC 50 =3.5 nM), but does not affect PP2C. By inhibiting PPs, this compound promotes protein phosphorylation and acts as a tumor promoter. Additionally, it is involved in inducing tau phosphorylation.
Cytostatin is a natural antitumor inhibitor of cell adhesion to extracellular matrix, blocking adhesion of B16 melanoma cells to laminin and collagen type IV in vitro (IC50s = 1.3 and 1.4 μg ml, respectively) and B16 cells metastatic activity in mice. It induces apoptosis of FS3 mouse fibrosarcoma cells (IC50 = 3.1 μg ml). Cytostatin potently and selectively inhibits protein phosphatase 2A (PP2A; IC50 = 29 nM against the catalytic subunit), while having no effect against PP1, PP2B, or PP5.
Cytostatin (sodium salt) is a natural antitumor inhibitor of cell adhesion to extracellular matrix, blocking adhesion of B16 melanoma cells to laminin and collagen type IV in vitro (IC50s = 1.3 and 1.4 μg/ml, respectively) and B16 cells metastatic activity in mice. It induces apoptosis of FS3 mouse fibrosarcoma cells (IC50 = 3.1 μg/ml). Cytostatin (sodium salt) potently and selectively inhibits protein phosphatase 2A (PP2A; IC50 = 29 nM against the catalytic subunit), while having no effect against PP1, PP2B, or PP5.