Pironetin is a bacterial metabolite originally isolated from Streptomyces that has diverse biological activities, including anti-proliferative, immunosuppressive, and plant growth regulatory properties.1,2,3,4 It binds to tubulin with a Kd value of 0.33 μM and increases the critical concentration (CrC) for tubulin assembly in glycerol-assembling buffer (GAB) at a concentration of 25 μM.2,3 It also induces G2/M phase cell cycle arrest in 3Y1 rat fibroblasts and apoptosis in HL-60 human leukemia cells when used at concentrations of 50 ng/ml and 33 nM, respectively.2,5 It inhibits the growth of HT-29 human colorectal and MCF-7 human breast cancer cells (IC50s = 6.4 and 6 nM, respectively) but also of non-cancerous human HEK293 cells (IC50 = 17 nM). It also inhibits the growth of A2780 human ovarian carcinoma cells, as well as of the drug-resistant, P-glycoprotein-expressing A2780AD subline (IC50s = 8 and 25 nM, respectively). Pironetin (5 mg/kg) decreases the generation of cytotoxic T lymphocytes in mice in response to immunization by EL4 allogeneic mouse T lymphocytes.4 It also inhibits rice plant growth by 23% when applied nine days prior to heading.1
1.Kobayashi, S., Tsuchiya, K., Harada, T., et al.Pironetin, a novel plant growth regulator produced by Streptomyces sp. NK10958. I. Taxonomy, production, isolation and preliminary characterizationJ. Antibiot. (Tokyo)47(6)697-702(1994) 2.Kondoh, M., Usui, T., Nishikiori, T., et al.Apoptosis induction via microtubule disassembly by an antitumour compound, pironetinBiochem. J.340(Pt 2)411-416(1999) 3.Vilanova, C., Díaz-Oltra, S., Murga, J., et al.Design and synthesis of pironetin analogue/colchicine hybrids and study of their cytotoxic activity and mechanisms of interaction with tubulinJ. Med. Chem.57(24)10391-10403(2014) 4.Yasui, K., Tamura, Y., Nakatani, T., et al.Chemical modification of PA-48153C, a novel immunosuppressant isolated from Streptomyces prunicolor PA-48153J. Antibiot. (Tokyo)49(2)173-180(1996) 5.Kondoh, M., Usui, T., Kobayashi, S., et al.Cell cycle arrest and antitumor activity of pironetin and its derivativesCancer Lett.126(1)29-32(1998)