Ansamitocin p-3 (Maytansinol isobutyrate, NSC292222, Antibiotic C 15003P3) is a potent inhibitor of tubulin polymerization with IC50 of 3.4 μM.
Ansamitocin p-3 at 5 μM completely inhibits the polymerization of tubulin isolated from bovine brains, but in contrast to VCR, Ansamitocin p-3 at a high concentration of 80 μM does not leads to the aggregation of tubulin. Ansamitocin p-3 at 16 μM also potently depolymerizes the polymerized tubulin (IC50 = 3.8 μM). The addition of Ansamitocin p-3 to culture cells blocks the morphological alteration of AC cells from fibroepithelioid to a glial cell type caused by the exposure to a certain concentration of dibutyryl cyclic adenosine 3':5'-monophosphate. In addition, Ansamitocin p-3 treatment at 16 nM causes the well-defined network of cytoplasmic microtubules of A31 cells rapidly dispersed. Short-term Ansamitocin p-3 treatment also inhibits the synthesis of DNA in A31 cells or KB cells. These results confirm that Ansamitocin p-3 acts by interfering with the microtubule assembly system, thus resulting in an inhibition of mitotic spindle fiber formation and, ultimately, cytokilling. [1] Ansamitocin p-3 displays potent cytotoxicity against A-549, HT-29, and MCF-7 cells in a dose-dependent manner with ED50 of 4 ×10-7, 4 × 10-7, and 2 × 10-6 μg/mL, respectively. [2] Ansamitocin p-3 also exhibits cytotoxicity against HCT-116 cells with a much low EC50 of 0.081 nM. [3] Ansamitocin p-3 enhances the effect of radiation both in Drosophila cells and human cancer cells in a p53 dependent manner. [4]
Ansamitocin p-3 treatment (>1 μg) significantly suppresses the growth of leukemia SN36, and induces an increased arrest in metaphase of P388 leukemia cells. Ansamitocin p-3 treatment at 25 μg/kg/day significantly prolongs the survival time of mice bearing i.p. B16 melanoma by 130%. Ansamitocin p-3 treatment also significantly prolongs the survival time of mice bearing Ehrlich ascites carcinoma, Sarcoma 180, and P815 mastocytoma, while slightly prolongs the survival time of mice bearing ascites MOPC-104E myeloma,leukemia L1210, and leukemia C1498. [1]
[1] Ootsu K, et al. Cancer Res, 1980, 40(5), 1707-1717. [2] Suwanborirux K, et al. Experientia, 1990, 46(1), 117-120. [3] Young DH, et al. J Biomol Screen, 2006, 11(1), 82-89.