Staurosporine induces telophase arrest and apoptosis blocking mitosis exit in human Chang liver cells

RalBP1 and p19-VHL play an oncogenic role, and p30-VHL plays a tumor suppressor role during the blebbishield emergency program

Cancer stem cells evade apoptotic death by blebbishield emergency program, which constructs blebbishields from apoptotic bodies and drives cellular transformation. Von Hippel-Lindau (VHL) plays both tumor suppressor and oncogenic roles, and the reason behind is poorly understood. Here we demonstrate that dimers and trimers of p19-VHL interact with RalBP1 to construct blebbishields. Expression of RalBP1, p19-VHL, and high-molecular weight VHL is required to evade apoptosis by blebbishield-mediated transformation. In contrast, p30-VHL plays a tumor suppressor role by inhibiting blebbishield-mediated transformation. Furthermore, target genes of VHL that suppress oxidative stress were elevated during blebbishield-mediated cellular transformation. Thus, RalBP1 and p19-VHL play an oncogenic role, whereas p30-VHL plays a tumor suppressor role during the blebbishield emergency program by regulating oxidative stress management genes.

Stuck in division or passing through: what happens when cells cannot satisfy the spindle assembly checkpoint

Cells that cannot satisfy the spindle assembly checkpoint (SAC) are delayed in mitosis (D-mitosis), a fact that has useful clinical ramifications. However, this delay is seldom permanent, and in the presence of an active SAC most cells ultimately escape mitosis and enter the next G1 as tetraploid cells. This review defines and discusses the various factors that determine how long a cell remains in mitosis when it cannot satisfy the SAC and also discusses the cell's subsequent fate.

Effect of staurosporine on cycle human gastric cancer cell

AIM: To study the effect of staurosporine (ST) on the cell cycle of human gastric cancer cell lines MGC803 and SGC7901.

METHODS: Cell proliferation was evaluated by trypan blue dye exclusion method. Apoptotic morphology was observed under a transmission electron microscope. Changes of cell cycle and apoptotic peaks of cells were determined by flow cytometry. Expression of P21^WAF1 gene was examined using immunohistochemistry and RT-PCR.

RESULTS: The growth of MGC803 and SGC7901 cells was inhibited by ST. The inhibitory concentrations against 50% cells (IC₅₀) at 24 h and 48 h were 54 ng/ml and 23 ng/ml for MGC803, and 61 ng/ml and 37 ng/ml for SGC7901. Typical apoptotic bodies and apoptotic peaks were observed 24 h after cells were treated wth ST at a concentration of 200 ng/ml. The percentage of cells at G₀/G₁ phase was decreased and that of cells at G₂/M was increased significantly in the group treated wth ST at the concentrations of 40 ng/ml, 60 ng/ml, 100 ng/ml for 24 h, compared with the control group (P < 0.01). The expression levels of P21^WAF1 gene in both MGC803 and SGC7901 cells were markedly up-regulated after treatment with ST.

CONCLUSION: ST can cause arrest of gastric cancer cells at G₂/M phase, which may be one of the mechanisms that inhibit cell proliferation and cause apoptosis in these cells. Effect of ST on cells at G₂/M phase may be attributed to the up-regulattion of P21^WAF1 gene.

Apoptotic mechanisms in T47D and MCF-7 human breast cancer cells

To investigate the mechanisms underlying apoptosis in breast cancer cells, staurosporine was used as an apoptotic stimulus in the human breast cancer cell lines MCF-7 and T47D. Staurosporine induced dose and time dependent increases in DNA fragmentation which was abrogated by z-VAD-fmk. MCF-7 cells did not express caspase-3, suggesting that DNA fragmentation occurred in the absence of caspase-3 and that other caspases may be involved. Staurosporine induced DEVDase activity in T47D cells suggesting the involvement of caspase-3 and/or caspase-7, yet there was no DEVDase activity in MCF-7 cells, probably ruling out the involvement caspase-7. However, staurosporine induced the cleavage of pro-caspase-6 in MCF-7 cells, but not in T47D cells. Caspase dependent PARP cleavage was detected in MCF-7 cells at 3 h, whereas only partial PARP cleavage was detected in T47D cells and then only after 24 h. Moreover, staurosporine led to cytochrome c release at 2 h in MCF-7 cells and 6 h in T47D cells. In addition, a time dependent and caspase-independent reduction of the mitochondrial transmembrane potential was observed; which appeared to occur after the release of cytochrome c. Translocation of Bax from the cytosol to mitochondria was observed in both cell types, and this preceded cytochrome c release in both T47D and MCF-7 cells. Apoptotic events in both cell types differ temporally, involving activation of different caspases and mitochondrial changes.

Necrosis has orderly DNA fragmentations

Necrosis from freezing manifested an orderly pattern of DNA fragmentations, including the apoptosis signature of 200 bp ladder, in three different cell populations, despite pancaspase suppression by zVAD-fmk. Immediately on thawing, all three populations had 100% dead cell indices and 2.2, 1.6, and 1.1 megabase fragmentations, which marked the point of death. Kilobase and 200 bp DNA ladder fragmentations manifested later together with overt necrotic morphologies. CpG oligodeoxynucleotides (ODNs) complementary to highly conserved GCn(x)GC motifs inhibited the megabase fragmentations and retarded their electrophoretic mobility (gel shift), indicating ODN-DNA binding, which is known to confer site-specific resistance to cleavage. Cleavage specificity was confirmed using EDTA-CpG ODN conjugates to direct free-radical-producing transitional element, vanadyl(4), to the binding sites to reproduce the megabase fragmentations in normal cells. Specific orderly fragmentations in necrosis suggested a necrosis-apoptosis convergence after death has been committed.

Anti-proliferative effects of new staurosporine derivatives isolated from a marine ascidian and its predatory flatworm

Nine indolocarbazole alkaloids of the staurosporine type, including three new derivatives, were evaluated for their potential as inhibitors of cell proliferation and macromolecule synthesis. Four derivatives were tested as inhibitors of cell proliferation with twelve human leukemia cell lines and demonstrated powerful antiproliferative activities, with 3-hydroxystaurosporine being the most potent. IC(50) values were determined using the cell line MONO-MAC-6 and with an IC(50) of 13 ng/ml, 3-hydroxystaurosporine turned out to be one of the most active staurosporine-type inhibitors described so far. All derivatives, except 3-hydroxy-3'-demethoxy-3'-hydroxystaurosporine and 4'-N-methylstaurosporine very strongly reduced RNA and DNA synthesis with 3-hydroxystaurosporine again being the strongest inhibitor. Analysis of structure-activity relationships demonstrated that hydroxylation of staurosporine at position 3 of the indolocarbazole moiety caused an increase in anti-proliferative activity, while hydroxylation at carbon 11 resulted in a decrease in activity. Our results suggest that not only the presence or absence of hydrophilic substitutions, but also the position of the alteration within the molecule, is important in the antiproliferative properties of the various staurosporine analogues.

Antitumor activity of benzamide riboside and its combination with cisplatin and staurosporine

Benzamide riboside (BR), a new synthetic nucleoside analogue, has demonstrated a potent cytotoxic activity in murine leukemia in vitro. The purpose of the present investigation was to examine the antitumor activity of BR in mice bearing leukemia L1210. The results revealed that BR possesses a potent antitumor activity in vivo. It increases life-span of mice with leukemia. Synergistic cytotoxicity of BR with select DNA damaging agents, cisplatin (cis-Pt) and staurosporine (STP) was examined in MTT chemosensitivity assay, FACS analyses and apoptotic DNA fragmentation on L1210 cells in culture. A simultaneous treatment of leukemia L1210 cells with the combination of BR and STP resulted in synergistic cytotoxicity that correlated with increased apoptotic activity in those cells. On the other hand, treatment of L1210 cells with combination of BR and cis-Pt resulted in antagonistic cytotoxic effect. Finally, to elucidate the synergistic effect of BR and STP in inducing apoptosis, the attention was directed to the activation of cell death processes through various cell cycle signals. This is the first report describing in vivo antitumor activity of BR and its utilization in combination chemotherapy.

Fas-mediated apoptosis in T cells involves the dephosphorylation of the retinoblastoma protein by type 1 protein phosphatases

Apoptosis is triggered by a number of different stimuli including the activation of Fas antigen, a member of the TNF family, by the Fas ligand. The signal transduction events implicated in apoptosis are complex and remain only partially understood. In this study, we used calyculin A, a potent inhibitor of serine/threonine (ser/thr) phosphatases types 1 and 2A, to investigate the role of ser/thr phosphatases in Fas-induced apoptosis. We showed that calyculin A inhibited Fas-induced DNA fragmentation and cytolysis in Jurkat cells and that this inhibition was not due to the modulation of Fas. Okadaic acid also inhibited Fas-induced apoptosis of Jurkat cells, but at much higher concentrations (microM level), thus implicating that type 1 phosphatases rather than type 2A are inhibited at nM concentrations. Cross-linking Fas led to the dephosphorylation of the retinoblastoma gene product (Rb) within 5 min, and to PARP cleavage within 2 h. Both events were inhibited by calyculin A indicating that apoptotic death triggered by Fas cross-linking involves the activation of type 1 ser/thr phosphatases.

Lineage-related susceptibility of human hemopoietic cell lines to apoptosis

Apoptosis plays a fundamental role in shaping normal hematopoiesis. We have investigated the relationship existing between susceptibility to apoptosis and lineage commitment in hemopoietic cells. The presence and degree of apoptosis were investigated in myeloid (HL-60 and K562), T (Jurkat and MOLT-4), and B (CESS and Raji) lymphoid cell lines by using a variety of techniques-transmission electron and light microscopy, flow cytometry and DNA gel electrophoresis. The major achievement of this study is that hematopoietic cells respond to different chemical (staurosporin, tiazofurin, camptothecin) and physical (hyperthermia or hypothermia) stimuli by apoptosis in a lineage-related way. Moreover, with respect to the methods used to detect apoptosis, a strong correlation was observed between the presence of the hypodiploid peak determined by flow cytometry and the DNA laddering evaluated by gel electrophoresis, but both techniques failed to demonstrate the presence of apoptosis in some cases. We conclude that cells of different hematopoietic lineages mostly show a lineage-related behaviour in their apoptotic response to different stimuli, suggesting that the lineage commitment and the stage of differentiation can confer different sensitivities to specific apoptotic stimuli. Moreover, morphological techniques still represent the most reliable approach to detect apoptosis in hemopoietic cells.

Euchromatin megabase cleavages and conjoint apoptotic-autophagic death expression with nucleolar ball-and-socket joint dislocations in human Chang liver cells arrested in S-phase by etoposide

Etoposide induced a megabase (Mb) fragmentation pattern identical with that from genomic digestion by NotI restriction endonuclease which specifically cleaves CpG islands in euchromatin domains. Redigestion by NotI produced no change, suggesting cleavage in the same or closely related sites in euchromatin domains. Preferential euchromatin cleavage was further suggested by harvested metaphase chromosomes showing self-inflicted resolution of light G-bandings (R-bandings), the euchromatin domains. Autodegeneration following Mb euchromatin fragmentations was shown by their degradation into 200 bp ladders, and expressions of apoptotic and "non-apoptotic" active death morphologies that were also seen conjointly in the same cell. The endstage further showed heterochromatin masses anchored to the nucleolus by novel ball-and-socket joints where dislocations occurred with nuclear leakage.

G-band expression and megabase fragmentations in apoptosis

Apoptosis seems characterized by a cascade of megabase to 200-bp fragmentations and by a commitment to perish at the initial level. How that could be achieved seems unclear. Preferential cleavage of transcriptionally active chromatin by apoptotic nuclease activity has long been suggested. We show here the manifestation of self-inflicted G-banding patterns in mitotic chromosomes, or G-band expression, occurring concurrently with a pattern of megabase fragmentations in two apoptotic systems that we have established in human Chang liver cells using (a) staurosporine and (b) vanadyl(4) prepulsing. We further show that rare-cutting NotI and MluI restriction endonucleases with C-G dinucleotide sequence specificity had produced similar G-bandings and megabase fragmentations cascading down to the 200-bp ladder fragmentation that were also associated with the expression of characteristic apoptotic morphologies by the digested cells. CpG-specific methylation using the methylase SssI abolished the DNA fragmentation cascade, G-banding, and apoptotic expressions induced by NotI and MluI, implicating endonuclease cleavage of active chromatin, where CpG islands are concentrated, as the initiating event. Reproducing the G-bandings and megabase fragmentations by directly applying NotI and MluI endonucleases to fixed chromosomes and extracted genomic DNA, respectively, further confirmed the notion of endonucleolytic cleavage of active chromatin as the causation. Nuclease-digested light G-band regions of chromosomes appeared to be the chromosome sites providing the megabase fragments. Transcriptionally active genes of the genome are known to be preferentially cleaved by nuclease activity and are established as being concentrated in the light G-bandings that correspond to R-bandings, which are also known to be the sites of more frequent cytogenetic breakpoints. Manifestation of self-inflicted G-banding patterns (G-banding expression) in apoptosis would then imply cleavage of the transcriptionally active genes in every light G-band site of every chromosome in the genome. This must be suicidal.