Cytoplasm of Cdc7-depleted HeLa cells, but not in p53-positive U2OS or HCT116 cells. The accumulation of CyclinB1 is as a consequence of 14-3-3s, and co-depletion of 14-3-3s results in abrogation of CyclinB1 accumulation too as partial rescue of viability. ATR-MK2, activated by Cdc7 depletion, is required for CyclinB1 accumulation. Abrogation of CyclinB1 accumulation by other techniques also resulted in much less cell death, indicating that the cytoplasmic sequestration/accumulation of CyclinB1 and the following abrupttransport into nuclei could be a predominant factor for cell death in p53-negative cells. It was reported in hematopoietic cells that ectopic overexpression of CyclinB1 causes apoptosis. In addition, the elevated amount of CyclinB1 stimulates c-irradiation induced cell death [40]. It was also reported that nuclear accumulation of CyclinB1 causes apoptosis in cancer cells [29]. We see more than half of your cell population die immediately after translocation with the accumulated CyclinB1 into nuclei, which causes transient but marked increases of nuclear CyclinB1, leading to aberrant chromosome separation and cell division. We also observed cell death in these cells accumulating CyclinB1 in cytoplasm (Fig. 2C). In p53-positive cells, in contrast, Cdc7 depletion led predominantly to death in the course of S phase. This may be because of p53-mediated G1 or S phase arrest, that ultimately leads to aberrant entry into S phase. FoxM1 is necessary for transcriptional up-regulation of mitotic regulators in Cdc7-depleted HeLa cells (Fig. eight). TAI-1 In stock p53mediated inhibition of FoxM1 may perhaps also contribute to decreased mitotic regulators in Cdc7-depleted p53-positive cancer cells.Addition of Dibromochloroacetaldehyde web standard anti-cancer drugs facilitates Cdc7 depletion-induced cancer cell deathCombinations of a number of anti-cancer drugs can sometimes be far more efficient and have much less side effects when treating cancer patients than the usage of single anti-cancer drugs. On the other hand, the rationale behind powerful multi-drug cancer therapy strategies hasPLoS One | plosone.orgCancer Cell Death Induced by Replication DefectFigure 10. Proposed pathways of cell death induced in cancer cells by inhibition of Cdc7 kinase. Inhibition of initiation of DNA replication by suppression of Cdc7 kinase leads to activation of ATM/ATR, which might lead to the activation of 3 checkpoint kinases, Chk1, MK2, and Chk2. Considering the fact that Cdc7 is actively necessary for activation of Chk1 [19,46], Chk1 will not be activated beneath this condition. Activated MK2 may phosphorylate Cdc2/Cyclin B1, which in turn may be recognized and bound by 14-3-3s protein and is sequestered in cytoplasm. Cdc7 depletion can induce DNA damages in cancer cells [19] and activated Chk2 would stabilize the FoxM1 transcription issue, which would induce the expression of CyclinB1 [47]. The accumulated CyclinB1 protein is abruptly transported into nuclei and mitotic catastrophe or post-mitotic cell death is induced. In p53-positive cancer cells, p53, activated via ATM/ATR, would induce G1 delay as well as S phase delay possibly by means of induction of p21. p53 inhibits transcription of FoxM1 [37,38], therefore preventing the induction of Cyclin B1. However, aberrant S phase progression within the absence of Cdc7 would induce cell death in p53-positive cancer cells. doi:10.1371/journal.pone.0036372.gnot been well established. We examined the effect of etoposide and 5FU, frequently-used anti-cancer agents, on Cdc7 inhibitioninduced cell death in p53-positive or p53-negative HCT116 cells. The Cdc7 inhib.
