Cell cycle arrest in early mitosis and induction of caspase-dependent apoptosis in U937 cells by diallyltetrasulfide (Al2S4)

Abstract

Naturally occurring organic sulfur compounds (OSCs), such as linear allylsulfides from Allium species, are attracting attention in cancer research, since several OSCs were shown to act beneficially both in chemoprevention and in chemotherapy, while hardly exerting any harmful side effects. Hence, we investigated the possible role of different OSCs in the treatment of leukemia. Thereby, we found that the compounds tested in this study induced apoptosis in U937 cells, with an efficiency depending on the number of sulfides, and selected the most promising candidate, diallyltetrasulfide (Al2S4), for detailed mechanistic studies. Here we show that Al2S4 induced an accumulation of cells in early mitosis (G2/M phase), followed by the activation of caspase-dependent apoptosis. The compound counteracted different anti-apoptotic Bcl-2 family members (Bcl-xL, phospho-Bad and Bcl-2), promoted activation of Bax and Bak and induced the release of cytochrome c into the cytoplasm. Treatment by Al2S4 let to the identification of early apoptotic events including Bcl-xL degradation, Bak activation and release of cytochrome c followed by late events including Bcl-2 proteolysis, Bax activation, Bad dephosphorylation, caspase activation, nuclear fragmentation and phosphatidylserine exposure.

Naturally Occurring Organic Sulfur Compounds: An Example of a Multitasking Class of Phytochemicals in Anti-Cancer Research

“…In line with the importance of sulfur, recent reports provided evidence that the biological activity of polysulfides directly correlates with their number of sulfur atoms, even if this relationship is not linear (Anwar et al, 2008). Thus, we found DATTS being the most active diallylsulfide in inducing apoptosis in U937 lymphoma cells, followed by DATS, whereas DAS and DADS instead were rather inactive (Cerella et al, 2009). Similarly, DATTS showed the highest antibiotic activity against Staphylococcus aureus (Tsao & Yin, 2001).…”

“…Some OSCs derived from Allium have been reported to possess an antioxidant activity (Borek, 2001). Due to their sulfur atoms, which can appear in up to ten different oxidation states (-2 to +6), these compounds can undergo redox-reactions (Cerella et al, 2009). Nishimura et al reported that Allium-derived organic sulfides and sulfoxides form in vivo sulfoxides and sulfones, respectively, by scavenging free hydroxyl (OH) or OOH radicals (Nishimura et al, 2000).…”

“…The accumulation of cyclin B1 correlates with the down-regulation of CDC25B and 25C, which control the phosphorylation status and the activation of cyclin-dependent kinase (Cdk1) (see section 5.2). Besides, treated cells present a high positivity to the phosphorylated form of histone H3, at the level of ser 10 (H3P) (Cerella et al, 2009;HermanAntosiewicz & Singh, 2005). The degradation of cyclin B1 and H3P is an indispensable event to progress during mitosis into the anaphase.…”

Heteronemin, a spongean sesterterpene, inhibits TNFα-induced NF-κB activation through proteasome inhibition and induces apoptotic cell death

“…Percentage of apoptotic cells was quantified as the fraction of apoptotic nuclei, as previously described assessed by fluorescence microscopy (Leica-DM IRB microscope, Lecuit, Luxemburg) upon staining with the DNA-specific dye Hoechst 33342 (Sigma) [37]. The fraction of cells with nuclear apoptotic morphology was counted (at least 300 cells in at least three independent fields).…”

Antiproliferative effect of natural tetrasulfides in human breast cancer cells is mediated through the inhibition of the cell division cycle 25 phosphatases

“…For instance, reactive oxygen species (ROS) generation seems to be one of the antiproliferative mechanisms of such compounds in cancer cells, but ROS levels seem to be closely dependent of the cell lines tested. For example, Cerella et al have reported that polysulfides induced a caspase-dependent apoptosis in U937 leukemia cells by activation of pro-apoptotic Bcl-2 family members and the release of the cytochrome c into the cytoplasm without ROS production (24). In contrast, Hosono et al showed that DAS 3 led to the formation of ROS in colon cancer cells, causing ß-tubulin oxidation and the disruption of the microtubule network, thus affecting the formation of --------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------a Effects of DAS 4 and DPS 4 (50 μM) on MCF-7 and Vcr-R cell cycle distribution after 24 h exposure.…”