The cause of p53 induction and single-cell dynamics in these contexts remains unclear. Prolonged mitotic arrest with the same drugs causes apoptosis during mitotic arrest in apoptosis-sensitive cell lines in less sensitive lines, cells undergo slippage without division into tetraploid G1, which may be followed by p53-dependent arrest, apoptosis, or another round of mitosis ( Rieder and Maiato, 2004 Gascoigne and Taylor, 2008 Orth et al., 2008). In noncancer cells, extension of prometaphase of mitosis from ∼30 min to 1.5–2 h with mitotic inhibitors, followed by washout and normal division, causes p53-dependent cell cycle arrest in the next G1 phase without obvious DNA damage ( Uetake and Sluder, 2010). Cells can sense perturbations of mitosis and initiate a response. Live imaging of cells undergoing normal mitosis revealed induction of a single pulse of p53 after mitotic exit in many cells, suggesting even normal mitosis can trigger the p53 circuit to some extent ( Loewer et al., 2010). Normal mitosis lasts ∼1 h, and the resulting daughter cells rapidly reenter the next cell cycle. Different stresses therefore encode different p53 dynamics, and these dynamics may determine cell fate ( Batchelor et al., 2011 Zhang et al., 2011).
#Icad antibody series#
p53 also induces MDM2, an E3 ligase that catalyzes p53 degradation, and together with other proteins, this circuit generates a series of uniform pulses of p53 in response to DNA damage induced by γ-irradiation and a graded pulse in response to UV irradiation ( Batchelor et al., 2008, 2011). These include key regulators of apoptosis (PUMA, NOXA) and cell cycle arrest (p21).
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When cells are stressed, for example by DNA damage, p53 becomes phosphorylated, resulting in its stabilization and induction of target genes that affect cell fate ( Jin and Levine, 2001). The tumor suppressor p53 is a central regulator of stress responses. A better understanding of the causal relationships among mitotic arrest, DNA damage, and p53 could help improve therapeutic strategies that employ antimitotic drugs. For example, DNA damage can result in the expression of ligands on the cell surface that in turn recruit natural killer cells to remove the damaged cells ( Gasser et al., 2005) and p53-driven senescence can up-regulate inflammatory cytokine production, resulting in tumor clearance via innate immune response ( Xue et al., 2007). These processes may all contribute to the therapeutic activities of a drug like Taxol (paclitaxel), but the causal relationships between them and their consequences in the tumor environment remain elusive. Prolonged mitotic arrest can lead to DNA damage and p53 induction ( Lanni and Jacks, 1998 Dalton et al., 2007 Quignon et al., 2007), followed by cell cycle arrest or apoptosis. More speculatively, partial activation of CAD may explain the DNA-damaging effects of diverse cellular stresses that do not immediately trigger apoptosis. Increased DNA damage via caspases and CAD may be an important aspect of antimitotic drug action. This partly activates CAD, causing limited DNA damage and p53 induction after slippage. We conclude that prolonged mitotic arrest partially activates the apoptotic pathway.
#Icad antibody full#
DNA damage was not due to full apoptosis, since most cytochrome C was still sequestered in mitochondria when damage occurred. These treatments also inhibited induction of p53 after slippage from prolonged arrest. This damage was inhibited by treatment with caspase inhibitors and by stable expression of mutant, noncleavable inhibitor of caspase-activated DNase, which prevents activation of the apoptosis-associated nuclease caspase-activated DNase (CAD). We detected DNA damage late in mitotic arrest and also after slippage. We investigated the cause of this induction.
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Live, single-cell imaging in human cancer cells responding to an antimitotic kinesin-5 inhibitor and additional antimitotic drugs revealed strong induction of p53 after cells slipped from prolonged mitotic arrest into G1. It can also cause DNA damage, but the relationship between these events has been unclear. Mitotic arrest induced by antimitotic drugs can cause apoptosis or p53-dependent cell cycle arrest.