Arsenite Delays Progression through Each Cell Cycle Phase and Induces Apoptosis following G₂/M Arrest in U937 Myeloid Leukemia Cells

Abstract

Arsenic is a well known toxicant and carcinogen that is also effective as a chemotherapeutic in the treatment of acute promyelocytic leukemia. Although its effects on humans are well documented, arsenic's mechanism of action is not well understood. Its ability to act as a carcinogen and as a chemotherapeutic seems paradoxical. However, cancer cell transformation and cancer cell destruction can both occur through perturbations of the cell cycle machinery, making cell cycle function a likely target of arsenic action. Arsenic has previously been shown to inhibit cancer cell cycle progression, but the targeted cell cycle phase has been debated. This study was designed to identify the cell cycle phase at which U937 cells are most sensitive to arsenite-induced growth inhibition. Centrifugal elutriation was used to divide asynchronous cell cultures into specific cell cycle phase-enriched fractions. These fractions were monitored for cell cycle phase progression in the presence and absence of sodium arsenite. We found an overall reduction in cell cycle progression rather than induction of arrest at one specific checkpoint. G 2 /M is the phase most sensitive to arsenite-induced apoptosis. However, arsenite profoundly affects U937 cell growth by increasing the length of time it takes cells to transit each phase of the cell cycle. Future study of cell cycle inhibition by arsenic should consider that the effect may not be mediated by the major cell cycle checkpoints.

Protective effect of curcumin against arsenic-induced apoptosis in murine splenocytesin vitro

“…Thus, the results in the present investigation demonstrated a somewhat clear line of toxicity progression in the murine splenocytes, i.e., excessive NaAsO 2 -induced generation of ROS led to an increase in the size of the sub-G 1 cell populations. Such outcomes are in accordance with those of previous in vitro studies by McCollum et al (2005) and Zhao et al (2008).…”

Genistein selectively potentiates arsenic trioxide‐induced apoptosis in human leukemia cells via reactive oxygen species generation and activation of reactive oxygen species‐inducible protein kinases (p38‐MAPK, AMPK)

“…In addition, genistein caused G 2 /M blockade, and cells at G 2 were reported to be especially sensitive to the toxic action of ATO. 56 These and other possibilities are under investigation.…”

p53 Suppression of Arsenite-Induced Mitotic Catastrophe Is Mediated by p21CIP1/WAF1

“…Cells were then stained with 10 g/ml propidium iodide in the presence of RNase A (100 U/ml final) for at least 30 min at room temperature. Cell cycle/mitotic index analysis was performed as described previously (McCollum et al, 2005). Cell cycle analysis [bivariate plots of BrdU incorporation (FITC) and DNA content or TG-3 (allophycocyanin) staining and DNA content] was performed on a FACSCalibur (BD Biosciences).…”

“…In NB4 cells, an acute promyelogenous leukemia cell line, arsenic induces apoptosis and down-regulates Bcl-2 expression at concentrations of 2 to 4 M and causes arrest in early M phase and induction of apoptosis (Cai et al, 2003). In cells lacking functional p53, such as SV40-transformed human fibroblasts (States et al, 2002) and in HeLa, KB (Huang and Lee, 1998), or U937 cells (McCabe et al, 2000;McCollum et al, 2005) arsenic induces mitotic arrest and apoptosis. In contrast, these moderate concentrations slow the growth of diploid human fibroblasts and telomeraseimmortalized human fibroblasts (S. C. McNeely and J. C. States, unpublished data) but do not induce cell death through mitotic catastrophe (Yih et al, 1997;States et al, 2002).…”