Inostamycin A is a bacterial metabolite that has been found in Streptomyces and has anticancer activity.1 It is an inhibitor of CDP-diacylglycerol:inositol 3-phosphatidyltransferase (IC50 = 0.02 µg/ml in A431 cell membranes) and is selective for CDP-diacylglycerol:inositol 3-phosphatidyltransferase over phospholipase C (PLC) and phosphatidylinositol kinase at 10 µg/ml.2 Inostamycin A decreases viability of YCU-T892, KCC-TC873, KB, HSC-4, and YCU-T891 oral squamous cell carcinoma (OSCC) cells in a concentration-dependent manner.3 It induces cell cycle arrest in the G1 phase in HSC-4 cells when used at a concentration of 250 ng/ml and induces apoptosis in Ms-1 small cell lung cancer cells at 300 ng/ml.3,4 Inostamycin A also reduces levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 and inhibits EGF-induced migration of HSC-4 cells.5

1.Imoto, M., Umezawa, K., Takahashi, Y., et al.Isolation and structure determination of inostamycin, a novel inhibitor of phosphatidylinositol turnoverJ. Nat. Prod.53(4)825-829(1990) 2.Imoto, M., Taniguchi, Y., and Umezawa, K.Inhibition of CDP-DG: inositol transferase by inostamycinJ. Biochem.112(2)299-302(1992) 3.Baba, Y., Tsukuda, M., Mochimatsu, I., et al.Cytostatic effect of inostamycin, an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase, on oral squamous cell carcinoma cell linesCell Biol. Int.25(7)613-620(2001) 4.Imoto, M., Tanabe, K., Simizu, S., et al.Inhibition of cyclin D1 expression and induction of apoptosis by inostamycin in small cell lung carcinoma cellsJpn. J. Cancer Res.89(3)315-322(1998) 5.Baba, Y., Tsukuda, M., Mochimatsu, I., et al.Inostamycin, an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): Inositol transferase, suppresses invasion ability by reducing productions of matrix metalloproteinase-2 and -9 and cell motility in HSC-4 tongue carcinoma cell lineClin. Exp. Metastasis18(3)273-279(2000)