X-Message-Number: 25711 Date: Tue, 22 Feb 2005 19:06:57 -0800 (PST) From: Doug Skrecky <> Subject: microtubules implicated in cellular senescence Cell Cycle. 2005 Mar 18;4(3) [Epub ahead of print] The Microtubule Stabilizing Agent Discodermolide is a Potent Inducer of Accelerated Cell Senescence. Discodermolide is a microtubule stabilizing agent that suppresses dynamic instability and blocks cells in mitosis. Selection of A549 nonsmall cell lung carcinoma cells with increasing concentrations of discodermolide yielded a clone that proliferated in 8 nM. When these cells were exposed to any concentration greater than 8 nM, replication ceased and the cells developed a flattened, enlarged, granular morphology. Accelerated senescence was demonstrated by a functional beta-galactosidase activity at pH 6. When parental A549 cells were treated with IC(50)-concentrations of doxorubicin, Taxol or discodermolide, the latter two drugs quickly produced aberrant mitosis. However, discodermolide, but not Taxol, also produced a large increase in senescence-associated beta-galactosidase activity and altered levels of known senescence markers. Although some of these differences between Taxol and discodermolide were dose dependent, only discodermolide produced a doxorubicin-like induction of a senescence phenotype, including a senescence-associated beta-galactosidase activity, up-regulation of PAI-1 and p66Shc, and a strong, sustained, Erk1/2 activation. This research provides insights into the mechanism of action of discodermolide and provides the first demonstration of a microtubule stabilizing agent that inhibits tumor cell growth with a powerful induction of accelerated senescence. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=25711