Cisplatin induces apoptosis in a human ovarian carcinoma cell line without concomitant internucleosomal degradation of DNA

Copper(II) N,N,O-Chelating Complexes as Potential Anticancer Agents

Three novel dinuclear Cu(II) complexes based on a N,N,O-chelating salphen-like ligand scaffold and bearing varying aromatic substituents (−H, −Cl, and −Br) have been synthesized and characterized. The experimental and computational data obtained suggest that all three complexes exist in the dimeric form in the solid state and adopt the same conformation. The mass spectrometry and electron paramagnetic resonance results indicate that the dimeric structure coexists with the monomeric form in solution upon solvent (dimethyl sulfoxide and water) coordination. The three synthesized Cu(II) complexes exhibit high potentiality as ROS generators, with the Cu(II)/Cu(I) redox potential inside the biological redox window, and thus being able to biologically undergo Cu(II)/Cu(I) redox cycling. The formation of ROS is one of the most promising reported cell death mechanisms for metal complexes to offer an inherent selectivity to cancer cells. In vitro cytotoxic studies in two different cancer cell lines (HeLa and MCF7) and in a normal fibroblast cell line show promising selective cytotoxicity for cancer cells (IC₅₀ about 25 μM in HeLa cells, which is in the range of cisplatin and improved with respect to carboplatin), hence placing this N,N,O-chelating salphen-like metallic core as a promising scaffold to be explored in the design of future tailor-made Cu(II) cytotoxic compounds.

Three novel dinuclear Cu(II) complexes based on a N,N,O-chelating salphen-like ligand scaffold and bearing varying aromatic substituents (−H, −Cl, and −Br) have been synthesized and characterized. They three exhibit high potentiality as reactive oxygen species (ROS) generators, with the Cu(II)/Cu(I) redox potential inside the biological redox window. In vitro studies in two different cancer cell lines (HeLa and MCF7) and in a normal fibroblast cell line show promising selective cytotoxicity for cancer cells.

A Multi-action and Multi-target RuII -PtIV Conjugate Combining Cancer-Activated Chemotherapy and Photodynamic Therapy to Overcome Drug Resistant Cancers

Pt^II complexes are commonly used to treat cancer. To reduce their side effects and improve their pharmacological properties, Pt^IV complexes are being developed as prodrug candidates that are activated by reduction in cancer cells. Concomitantly, Ru^II polypyridine complexes have gained much attention as photosensitizers for use in photodynamic therapy due to their attractive characteristics. In this article, a novel Pt^IV -Ru^II conjugate, which combines cancer activated chemotherapy with PDT, is presented. Upon entering the cancer cell, the Pt^IV centre is reduced to Pt^II and the axial ligands including the Ru^II complex and phenylbutyrate are released. As each component has its individual targets, the conjugate exerts a multi-target and multi-action effect with (photo-)cytotoxicity values upon irradiation up to 595 nm in the low nanomolar range in various (drug resistant) 2D monolayer cancer cells and 3D multicellular tumour spheroids.

Dose-dependent regulation of superoxide anion on the proliferation, differentiation, apoptosis and necrosis of human hepatoma cells: the role of intracellular Ca2+

Dose-dependent regulation of cellular processes is one important characteristic of signaling molecules. Although recent studies suggest that reactive oxygen species (ROS) may act as in vivo signaling molecules, the dose-dependent regulation of ROS on cellular processes together in one system needs to be evaluated. After treating cells with gradually increased O(2)(-), generated by the hypoxanthine-xanthine oxidase system, it was found that: (i) the proliferation of hepatoma cells firstly increased at 1-2 microM O(2)(-), then decreased markedly as the concentration increased; (2) at 8 or 16 microM O(2)(-), re-differentiation of hepatoma cells was induced, as indicated by the indices relating to cell malignancy or differentiation, such as cell surface charge, alpha-fetoprotein, gamma-glutamyltranspeptidase, tyrosine-alpha-ketoglutarate transaminase, cAMP, and the tumor's clonogenic potential; (iii) at 16 microM O(2)(-), accompanied by the re-differentiation of cells, cell apoptosis was also simultaneously induced as indicated by the appearance of apoptotic bodies, detached cells, and other apoptotic morphological features, as well as specific DNA fragmentation; (iv) at the highest concentration of O(2)(-) (32 microM) in this study, cell necrosis was dramatically induced as shown by Trypan blue exclusion; (v), an increase of intracellular Ca(2+) ([Ca(2+)](i)) was observed at all concentrations of O(2)(-) treatment, and this [Ca(2+)](i) increase was found to be involved in the regulation of O(2)(-) on the cellular processes. In conclusion, these results indicate that O(2)(-) could dose-dependently regulate the processes of cells, where Ca(2+) is one of its molecular targets, and hence provide a direct support for the hypothesis that ROS themselves are important signaling molecules.

Apoptosis and beyond: cytometry in studies of programmed cell death

A cell undergoing apoptosis demonstrates multitude of characteristic morphological and biochemical features, which vary depending on the inducer of apoptosis, cell type and the "time window" at which the process of apoptosis is observed. Because the gross majority of apoptotic hallmarks can be revealed by flow and image cytometry, the cytometric methods become a technology of choice in diverse studies of cellular demise. Variety of cytometric methods designed to identify apoptotic cells, detect particular events of apoptosis and probe mechanisms associated with this mode of cell death have been developed during the past two decades. In the present review, we outline commonly used methods that are based on the assessment of mitochondrial transmembrane potential, activation of caspases, DNA fragmentation, and plasma membrane alterations. We also present novel developments in the field such as the use of cyanine SYTO and TO-PRO family of probes. Strategies of selecting the optimal multiparameter approaches, as well as potential difficulties in the experimental procedures, are thoroughly summarized.

Cytometry in cell necrobiology revisited. Recent advances and new vistas

Over a decade has passed since publication of the last review on "Cytometry in cell necrobiology." During these years we have witnessed many substantial developments in the field of cell necrobiology such as remarkable advancements in cytometric technologies and improvements in analytical biochemistry. The latest innovative platforms such as laser scanning cytometry, multispectral imaging cytometry, spectroscopic cytometry, and microfluidic Lab-on-a-Chip solutions rapidly emerge as highly advantageous tools in cell necrobiology studies. Furthermore, we have recently gained substantial knowledge on alternative cell demise modes such as caspase-independent apoptosis-like programmed cell death (PCD), autophagy, necrosis-like PCD, or mitotic catastrophe, all with profound connotations to pathogenesis and treatment. Although detection of classical, caspase-dependent apoptosis is still the major ground for the advancement of cytometric techniques, there is an increasing demand for novel analytical tools to rapidly quantify noncanonical modes of cell death. This review highlights the key developments warranting a renaissance and evolution of cytometric techniques in the field of cell necrobiology.

Novel 4,4'-diether-2,2'-bipyridine cisplatin analogues are more effective than cisplatin at inducing apoptosis in cancer cell lines

The synthesis and characterization of dichloro(4,4'-bis[methoxy]-2,2'-bipyridine)platinum (1) and dichloro(4,4'-bis[3-methoxy-n-propyl]-2,2'-bipyridine)platinum (2) are described. As analogues to CDDP, these 4,4'-disubstituted 2,2'-bipyridine complexes exhibit decreased EC(50) values of 10-100 times in cancer cell lines of the lung, prostate, and melanoma with several combinations of complex and cell line less than 10 microM. Flow cytometry data indicate 'blocks' of MDA-MD-435 cycle by 1 (G2/M) and 2 (S). Observed cell survival trends in the presence of 1, 2 under ionizing radiation mimic those of CDDP. Preliminary structure activity relationships are discussed for the 4,4'-substitutions made on the bipyridine ring.

Roscovitine up-regulates p53 protein and induces apoptosis in human HeLaS(3) cervix carcinoma cells

Exposure of human HeLaS(3) cervix carcinoma cells to high doses of conventional cytostatic drugs, e.g. cisplatin (CP) strongly inhibits their proliferation. However, most cytostatic agents are genotoxic and may generate a secondary malignancy. Therefore, therapeutic strategy using alternative, not cytotoxic drugs would be beneficial. Inhibition of cyclin-dependent kinases (CDKs) by pharmacological inhibitors became recently a promising therapeutic option. Roscovitine (ROSC), a selective CDK inhibitor, efficiently targets human malignant cells. ROSC induces cell cycle arrest and apoptosis in human MCF-7 breast cancer cells. ROSC also activates p53 protein. Activation of p53 tumor suppressor protein is essential for induction of apoptosis in MCF-7 cells. Considering the fact that in HeLaS(3) cells wt p53 is inactivated by the action of HPV-encoded E6 oncoprotein, we addressed the question whether ROSC would be able to reactivate p53 protein in them. Their exposure to ROSC for 24 h induced cell cycle arrest at G(2)/M and reduced the number of viable cells. Unlike CP, ROSC in the used doses did not induce DNA damage and was not directly cytotoxic. Despite lack of detectable DNA lesions, ROSC activated wt p53 protein. The increase of p53 levels was attributable to the ROSC-mediated protein stabilization. Further analyses revealed that ROSC induced site-specific phosphorylation of p53 protein at Ser46. After longer exposure, ROSC induced apoptosis in HeLaS(3) cells. These results indicate that therapy of HeLaS(3) cells by ROSC could offer an advantage over that by CP due to its increased selectivity and markedly reduced risk of generation of a secondary cancer.

Methods for simultaneous measurement of apoptosis and cell surface phenotype of epithelial cells in effusions by flow cytometry

We describe here a protocol for the detection of epithelial cells in effusions combined with quantification of apoptosis by flow cytometry (FCM). The procedure described consists of the following stages: culturing and induction of apoptosis by staurosporine in control ovarian carcinoma cell lines (SKOV-3 and OVCAR-8); preparation of effusion specimens and cell lines for staining; staining of cancer cells in effusions and cell lines for cell surface markers (Ber-EP4, EpCAM and CD45) and intracellular/nuclear markers of apoptosis (cleaved caspase-3 and caspase-8, and incorporated deoxyuridine triphosphates); and FCM analysis of stained cell lines and effusions. This protocol identifies a specific cell population in cytologically heterogeneous clinical specimens and applies two methods to measure different aspects of apoptosis in the cell population of interest. The cleaved caspase and deoxyuridine triphosphate incorporation FCM assays are run in parallel and require (including sample preparation, staining, instrument adjustment and data acquisition) 8 h. The culturing of cell lines requires 2-3 days and induction of apoptosis requires 16 h.

Cell proliferation, apoptosis and mitochondrial damage in rat B50 neuronal cells after cisplatin treatment

OBJECTIVES

Cisplatin (cisPt) is used as a chemotherapeutic agent for the treatment of a variety of human tumours; more recently, it has been demonstrated that tumour cell exposure to cisPt ultimately results in apoptosis, but the mechanism by which nuclear cisPt/DNA generates the cytoplasmic cascade of events involved has not been clarified. We have investigated the effects of cisPt on proliferation in the neuronal cell line B50, with particular attention being given to understand whether mitochondria are a target of cisPt and their involvement in the apoptotic process.

MATERIALS AND METHODS

Rat neuronal B50 cells were used to investigate the mechanisms of cisPt-induced cytotoxicity; this line has been used as a model system for neurotoxicity in vivo.

RESULTS

Changes in proliferation, induction of apoptosis, activation of caspase-3 and DNA fragmentation were observed in the cells, as well as morphological and biochemical alterations of mithocondria. Activation of caspase-9 confirmed that mitochondria are a target of cisPt.

CONCLUSION

CisPt exerts cytotoxic effects in the neuronal B50 cell line via a caspase-dependent pathway with mitochondria being central relay stations.

Mechanisms of induction of apoptosis by anthraquinone anticancer drugs aclarubicin and mitoxantrone in comparison with doxorubicin: relation to drug cytotoxicity and caspase-3 activation

We examined molecular events and morphological features associated with apoptosis induced by anthraquinone anticancer drugs aclarubicin, mitoxantrone and doxorubicin in two spontaneously immortalized cell lines (NIH 3T3 and B14) in relation to cytotoxicity of these drugs. The investigated cells showed similar sensitivity to aclarubicin but different sensitivity to doxorubicin and mitoxantrone: mitoxantrone was the most cytotoxic drug in both cell lines. All three drugs triggered both apoptosis and necrosis but none of these processes was positively correlated with their cytotoxicity. Apoptosis was the prevalent form of cell kill by aclarubicin, while doxorubicin and mitoxantrone induced mainly the necrotic mode of cell death. The extent and the timing of apoptosis were strongly dependent on the cell line, the type of the drug and its dose, and were mediated by caspase-3 activation. A significant increase in caspase-3 activity and the percentage of apoptotic cells, oligonucleosomal DNA fragmentation, chromatin condensation and formation of apoptotic bodies was observed predominantly in B14 cells. NIH 3T3 cells showed lesser changes and a lack of DNA fragmentation. Aclarubicin was the fastest acting drug, inducing DNA fragmentation 12 h earlier than doxorubicin, and 24 h earlier than mitoxantrone. Caspase-3 inhibitor Ac-DEVD-CHO did not show any significant effect on drug cytotoxicity and DNA nucleosomal fragmentation.

Clofibric Acid, a Peroxisome Proliferator-activated Receptor Alpha Ligand, Enhances a Suppressive Effect of Cis-diaminedichloroplatinum on Proliferation of Ovarian Carcinoma Cells

The purpose of this study was to elucidate the possible mechanism that clofibric acid (CA), a peroxisome proliferator-activated receptor α ligand, enhances a suppressive effect of cis-diaminedichloroplatinum (CDDP) on proliferation of the ovarian carcinoma line OVCAR-3. These cells was incubated with 0.5 μM/ml CDDP in the presence or absence of 50 μM CA or incubated with 50 μM CA alone for 72 hr. While treatment with CA alone did not affect proliferation of OVCAR-3 cells, simultaneous treatment with CDDP and CA significantly suppressed proliferation of the cells and significantly induced apoptosis compared to that with CDDP alone. Treatment with CDDP and CA significantly decreased the prostaglandin (PG) E2 level in the medium of the cells compared with treatment with CDDP alone. These results suggest the ability of CA to enhance a suppressive effect of CDDP on proliferation of the ovarian carcinoma cells through reduction of PGE2 level.

Characterization of the anti-Leishmania effect induced by cisplatin, an anticancer drug

The cis-diamminedichloroplatinum(II), known as cis-DDP or cisplatin is a widely used drug in cancer chemotherapy. Although a recent study has shown the anti-Leishmania activity of some cis-DDP derivatives, the cytotoxic properties were measured only on promastigotes, the insect vector form of the parasite. In this study the effect of cis-DDP on promastigotes and amastigotes, the vertebrate stage of the parasite is reported. The IC50, determined by flow cytometry, after 72 h of drug incubation was four times higher, 7.73+/-1.03 microM in the case of promastigotes compared to axenic amastigotes, 1.88+/-0.10 microM. In intracellular amastigotes the IC50, determined by counting the parasite index was 1.85+/-0.22 microM. By using flow cytometry, two patterns of cell cycle changes was observed: cis-DDP treated promastigotes and amastigotes accumulated in S phase and G2 phase, respectively. The cis-DDP response was also found to involve an "apoptosis-like" death of both promastigotes and amastigotes. However, DNA fragmentation was only detected in promastigote forms. In contrast mitochondrial transmembrane potential loss was observed for both stages of the parasite. Upon incubation of parasites with the drug an increase on GSH and GSSG levels and reactive oxygen species could be detected in the case of promastigote. Moreover, a slight increase of GSH level was detected on amastigote form. Taken together, these observations indicate that amastigotes are more sensitive to cis-DDP when compared to promastigotes. However, the signaling pathways leading to cell death could be different.

Aurintricarboxylic acid inhibits protein synthesis independent, sanguinarine-induced apoptosis and oncosis

Sanguinarine, a benzophenanthridine alkaloid, has anticancer potential through induction of cell death. We previously demonstrated that sanguinarine treatment at a low concentration (1.5 microg/ml) induced apoptosis in K562 human erythroleukemia cells, and a high concentration (12.5 microg/ml) induced the morphology of blister formation or oncosis-blister cell death (BCD). Treatment of cells at an intermediate sanguinarine concentration (6.25 microg/ml) induced diffuse swelling or oncosis-diffuse cell swelling (DCS). To assess the underlying mechanism of sanguinarine-induced apoptosis and oncosis-BCD in K562 cells, we studied their response to pre-treatment with two chemical compounds: aurintricarboxylic acid (ATA) and cycloheximide (CHX). The pretreatment effects of both chemical compounds on apoptosis and oncosis-BCD were evaluated by measuring multiple parameters using quantitative morphology, electron microscopy, terminal deoxynucleotidyl transferase (TdT) end-labeling and annexin-V-binding. ATA, a DNA endonuclease inhibitor, efficiently prevented DNA nicking and inhibited apoptosis almost completely and oncosis-BCD by about 40%, while CHX, a protein synthesis inhibitor, failed to inhibit both apoptosis and oncosis-BCD. These results demonstrate, first, the importance of endonuclease in sanguinarine-induced apoptosis and to some extent in oncosis-BCD and, second, that this inhibition does not require de novo protein synthesis.

Cisplatin cytotoxicity in organ of corti-derived immortalized cells

Cisplatin is an anticancer drug currently used in the treatment of genital and head and neck tumors. Its use in these and other types of tumors is narrowed by onset of chemoresistance and severe undesired side effects, like as nephro- and ototoxicity, whose mechanisms of action are only partially understood. In the present study we investigated the effects of cisplatin (cis-dichlorodiaminoplatin, CDDP) on a cell line (OC-k3) developed from organs of Corti of transgenic mice. We observed at 48 h that cell death due to cisplatin was time and concentration-dependent. The cell death displayed some morphological hallmarks of apoptosis, including nuclear fragmentation into several large nuclear fragments, surrounded by a rearranged and thickened actin cytoskeleton. No DNA laddering was detected, suggesting absence of endonuclease activity, nor annexin V positivity, suggesting absence of phosphatidylserine externalization. Several molecules protected the cells against CDDP induced cytotoxicity, including methionine, suramin and PD98059. Methionine reduced CDDP-uptake, while suramin, a polycathionic compound a specifically binding external proteins, did not. This finding suggested that suramin could exert its protective effect by acting on an intracellular transduction pathway. We tested this hypothesis by studying the effect of suramin and PD98059, a MEK inhibitor, on the mitogen activated protein kinase (MAPK) cascade. After CDDP treatment, we found an increase of phosphorylation of extracellular regulated kinases (ERK)1/2, that could be inhibited by PD98059 and suramin. These data suggest that ERK pathways can play a role in mediating the cell death induction in presence of a CDDP challenge.

A fluorine containing bipyridine cisplatin analog is more effective than cisplatin at inducing apoptosis in cancer cell lines

Novel cisplatin analogs dichloro[4,4'-bis(4,4,4-trifluorobutyl)-2,2'-bipyridine]platinum (1) and fac-tricarbonylchloro[4,4'-bis(4,4,4-trifluorobutyl)-2,2'-bipyridine]rhenium (3) were synthesized and evaluated for their cytotoxicity. While 3 was not cytotoxic, 1 was 14 to 125 times more lethal than cisplatin in breast, prostate, and lung cancer cell lines. Compound 1 was able to induce apoptosis and the presence of the platinum atom was essential to its function as a cytotoxin.

Antitumor activities of D-glucosamine and its derivatives

The growth inhibitory effects of D-glucosamine hydrochloride (GlcNH(2).HCl), D-glucosamine (GlcNH(2)) and N-acetyl glucosamine (NAG) on human hepatoma SMMC-7721 cells in vitro were investigated. The results showed that GlcNH(2).HCl and GlcNH(2) resulted in a concentration-dependent reduction in hepatoma cell growth as measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. This effect was accompanied by a marked increase in the proportion of S cells as analyzed by flow cytometry. In addition, human hepatoma SMMC-7721 cells treated with GlcNH(2).HCl resulted in the induction of apoptosis as assayed qualitatively by agarose gel electrophoresis. NAG could not inhibit the proliferation of SMMC-7721 cells. GlcNH(2).HCl exhibited antitumor activity against Sarcoma 180 in Kunming mice at dosage of 125-500 mg/kg, dose of 250 mg/kg being the best. GlcNH(2).HCl at dose of 250 mg/kg could enhance significantly the thymus index, and spleen index and could promote T lymphocyte proliferation induced by ConA. The antitumor effect of GlcNH(2).HCl is probably host-mediated and cytocidal.

The role of histone acetylation versus DNA damage in drug-induced senescence and apoptosis

The present study was undertaken to determine the significance of histone acetylation versus DNA damage in drug-induced irreversible growth arrest (senescence) and apoptosis. Cellular treatment with the DNA-damaging drugs doxorubicin and cisplatin or with the histone deacetylase inhibitor trichostatin A, led to the finding that all the three drugs induced senescence at concentrations significantly lower than those required for apoptosis. However, only doxorubicin and cisplatin induced activation of H2AX, a marker for double-strand break formation. Interestingly, this occurred mainly at apoptosis and not senescence-inducing drug concentrations, suggesting that non-DNA-damage pathways may be implicated in induction of senescence by these drugs. In agreement with this, chromatin immunoprecipitation experiments indicated that doxorubicin was able to induce acetylation of histone H3 at the promoter of p21/WAF1 only at senescence-inducing concentrations. Collectively, these findings suggest that alteration of chromatin structure by cytotoxic drugs may represent a key mediator of senescence.

Cisplatin sensitizes cancer cells to ionizing radiation via inhibition of nonhomologous end joining

The combination of cisplatin and ionizing radiation (IR) treatment represents a common modality for treating a variety of cancers. These two agents provide considerable synergy during treatment, although the mechanism of this synergy remains largely undefined. We have investigated the mechanism of cisplatin sensitization to IR using a combination of in vitro and in vivo experiments. A clear synergistic interaction between cisplatin and IR is observed in cells proficient in nonhomologous end joining (NHEJ) catalyzed repair of DNA double-strand breaks (DSB). In contrast, no interaction between cisplatin and IR is observed in NHEJ-deficient cells. Reconstituted in vitro NHEJ assays revealed that a site-specific cisplatin-DNA lesion near the terminus results in complete abrogation of NHEJ catalyzed repair of the DSB. These data show that the cisplatin-IR synergistic interaction requires the DNA-dependent protein kinase-dependent NHEJ pathway for joining of DNA DSBs, and the presence of a cisplatin lesion on the DNA blocks this pathway. In the absence of a functional NHEJ pathway, although the cells are hypersensitive to IR, there is no synergistic interaction with cisplatin.

Induction of apoptosis and necrosis in lymphocytes by the cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP

cis-Diamminedichloroplatinum(II) (cis-DDP) is one of the most widely administrated antitumor drugs. However, the use of cis-DDP is severely limited because of its toxic side effects. Therefore, efforts are concentrated on the development of improved platinum compounds with a broader activity spectrum and effectiveness in chemotherapy, but lower toxicity. Beneficial properties of flavonoids, e.g. their antitumor activity, encouraged scientists to synthesize cis-bis(3-aminoflavone)dichloroplatinum(II). Abilities of these compounds to induce apoptosis and necrosis were compared by use of trypan blue, fluorochrome staining (Hoechst 33258/propidium iodide double staining) and TUNEL assays. The cytotoxicity was evaluated by MTT. The results obtained show that the cis-Pt(II) complex of 3-aminoflavone is less toxic than cis-DDP. However, the former compound has a faster rate of apoptosis induction in lymphocytes than the latter. The cis-Pt(II) complex of 3-aminoflavone induces apoptosis in normal lymphocytes to a lesser degree and could be a potential antitumor drug.

Flow cytometry of apoptosis

Application of flow cytometry to the study of cell death has three goals: identification and quantification of dead and dying cells; discrimination between apoptotic and necrotic modes of cell death; and elucidation of mechanisms involved in cell death. This massively detailed unit by a pioneer in the field brings together the most common flow cytometric methods for the study of apoptosis, covering a wide variety of apoptotic indices, from loss of membrane potential, caspase activation, and phosphatidyl exposure to DNA fragmentation and tissue transglutaminase activation. The authors also present their recently developed protocol, analogous to the FLICA approach for caspases, for the detection of serine proteases ('serpases'). The protocols are accompanied by extensive commentary discussion of applicability, strategic planning, problems, and pitfalls, plus a comprehensive list of references.

Different apoptotic responses and patterns in adhering and floating neoplastic cell cultures: effects of microtubule antagonists

The relationship between apoptotic progression and cell cycle perturbation induced by microtubule-destabilising (vinblastine, Colcemid) and -stabilising (taxol) drugs was studied in two mesenchyme-derived neoplastic cell lines, growing as suspension (Jurkat) and monolayer (SGS/3A) culture, by morphocytochemical and biochemical approaches. The same kind of drug induced different effects on the cell kinetics (proliferation, polyploidisation, death) of the two cell lines. In floating cells, the drugs appeared more effective during the S phase, while in adherent cells they were more effective during the G2/M phase. Moreover two distinct neoplasia-associated apoptotic phenotypes emerged: the first pattern was the typical one and was found in cells with a low transition through the S/G2 phase (Jurkat), and the second one was mainly characterised by a cell death derived from micronucleated and mitotic cells, as a consequence of a low transition through the M/G1 phase (SGS/3A). Our data show that the machinery required for the trigger and progression of apoptosis is present in every cell cycle phase, also in conditions of karyological alterations (aneugenic micronucleations). On the other hand, a different sensitivity of the two microtubular components (interphasic network and mitotic spindle) appears to be related to the anchorage-dependence or -independence during the cell growth disturbances after exposure to antimicrotubular drugs.

Induction of cell cycle arrest and apoptosis in human cervix carcinoma cells during therapy by cisplatin

The aim of the therapy of human malignancies is the inhibition of cell proliferation and/or induction of apoptosis. We studied the kinetics of the morphological and biochemical changes in HeLa cells during chemotherapy by cisplatin (CP). Apoptosis was evaluated by scoring of cells exhibiting changes characteristic for early and late stages of apoptosis as determined by Hoechst 33258 staining and by examination of positive reaction for activated caspase-3. Expression and intracellular localization of distinct proteins was analyzed by immunoblotting of subcellular fractions and segregation of nucleoli by immunocytochemistry. Chromatin fragmentation characteristic for apoptosis was observed in single cells after 3h cisplatin. A strong cytoplasmic accumulation of cytochrome C detected by immunoblotting 6h post-treatment was accompanied by an activation of caspase-9. Neither inhibition of cell division nor blocking of DNA replication preceded the onset of apoptosis. Our results show that after short treatment by CP, cell proliferation and apoptosis concomitantly occurred.

Nuclear apoptosis detection by flow cytometry: influence of endogenous endonucleases

Nuclear apoptosis is characterized by chromatin condensation and progressive DNA cleavage into high-molecular-weight fragments and oligonucleosomes. These complex phenomena can be mediated by the activation of a multiplicity of enzymes, characterized by specific patterns of cation dependance, pH requirement, and mode of activation. The significance of this multiplicity of enzymes that cleave genomic DNA has been attributed to the need of death effector pathways specific for cell types/tissues, the level of cell differenciation, and the nature of the apoptotic stimuli. The activation of these factors contributes to the development of alterations that can be detected specifically by flow cytometric assays, namely, propidium iodide assays, acridine orange/ethidium bromide double staining, the TUNEL and ISNT techniques, and the assays of DNA sensitivity to denaturation. Although applicable to a wide spectrum of cell types, an increasing body of literature indicates that these techniques cannot be universally applied to all cell lines and apoptotic conditions: The requirement of a particular mediator(s) of nuclear apoptosis or the absence of endonuclease activity can limit the relevance of certain techniques. Finally, endonucleases recruited during primary necrosis can introduce nuclear alterations detected by some assays and raise the problem of their specificity. This review underlines the need for strategies to accurately detect and quantify nuclear apoptosis by flow cytometry when new cell systems and apoptotic conditions are considered.

Investigating the relationship between the cell cycle and apoptosis using flow cytometry

Methods for using flow cytometry to investigate the relationship between the induction of apoptosis and the cell cycle are discussed. Methods for following cell cycle progression are also briefly reviewed. The methods are illustrated using a specific example of the effect of withdrawing an essential growth factor from a cell line.

Using flow cytometry to follow the apoptotic cascade

Flow cytometry has been extensively used to follow the apoptotic cascade and to enumerate apoptotic cells, both in cell cultures and, to a lesser extent, in tissue biopsies. An overview of the apoptotic cascade and how flow cytometric measurements can be used to observe the different elements of this process is presented.

Using mRNA expression profiling to determine anticancer drug efficacy

Pharmacogenomics is a fast-growing field of investigations that aims to further elucidate the inherited nature of interindividual differences in drug disposition and effects, with the ultimate goal of providing a stronger scientific basis for selecting the optimal drug therapy. Providing the right drug for the right patient is an important problem in the treatment of cancer. This is mainly due to the lack of information about the sensitivity of the tumor for a specific treatment modality, such as either chemotherapy or radiation treatment. This presentation highlights two approaches to identify responsiveness to treatment. Both approaches are based on the identification of expression profiles. The first approach concentrates on drug resistance and the second on the signaling pathways leading up to the death of the cell. Both approaches provide expression profiles; however, the more dynamic expression profiling as used to determine the signaling in damage cells promises to be a better determinant for the pharmacogenomic changes in expression profiles and, consequently, a potential better determinant for drug efficacy.

STAT3 exerts two-way regulation in the biological effects of IL-6 in M1 leukemia cells

The signal transducer and activator of transcription (STAT) proteins have been implicated in cytokine-regulated proliferation, differentiation and cell survival. Interleukin-6 (IL-6), a pleiotropic cytokine, induces a robust and sustained activation of STAT3 in M1 acute myeloid leukemia cells, which in turn undergo growth arrest, terminal differentiation and apoptosis in response to IL-6. The roles of STAT3 activation in IL-6-mediated responses in M1 cells are not fully understood. We introduced STAT3 antisense cDNA into M1 cells. STAT3 antisense cDNA blocked the expression and IL-6-induced tyrosine phosphorylation and DNA binding of STAT3, and resulted in reduction of both IL-6-induced growth arrest at G(0)/G(1) phase and macrophage differentiation in the M1 transformants. This observation is in accordance with previous reports and confirms that STAT3 plays an essential role in IL-6-induced growth arrest and terminal differentiation in M1 leukemia cells. On the other hand, STAT3 antisense cDNA augmented IL-6-induced apoptosis of M1 cells, which was supported by the cell cycle assay, DNA fragmentation assay and detection of the p17 active fragment of Caspase 3. As proliferation inhibition and differentiation induction stands for a negative signal, while survival maintenance stands for a positive signal, we conclude that STAT3 exerts two-way regulation on the biological effects of IL-6 in M1 leukemia cells.

Flow cytometry in analysis of cell cycle and apoptosis

The capacity for multiparametric measurement of large cell populations rapidly and accurately offered by cytometry has made this methodology indispensable in studies of cell proliferation and cell death. The reviewed cell cycle applications include (1) the univariate analysis of cellular DNA content for identification of G(0/1) versus S versus G(2)/M cells; (2) discrimination between noncycling (G(0); quiescent) and proliferating cells, based on the presence of proliferation-associated proteins; (3) identification of mitotic cells by histone H3 phosphorylation; (4) bivariate analysis of expression of cyclins D, E, A, or B1 versus DNA content; and (5) detection of DNA replicating cells and analysis of cell kinetics from the bivariate distributions of 5-bromo-2'-deoxyuridine (BrdU) incorporation versus DNA content. For the identification of apoptotic cells and discrimination between apoptosis and necrosis, flow cytometry techniques are applied to evaluate for changes in cell morphology, the presence of phosphatidylserine on cell surface, collapse of mitochondrial transmembrane potential, DNA fragmentation, and evidence of caspase activation. Semin Hematol 38:179-193.

Identification of apoptotic cells by formamide-induced dna denaturation in condensed chromatin

In this article we describe a novel effect of formamide on DNA of apoptotic nuclei and present a method for specific detection of apoptotic cells based on this effect. Our observations show that formamide induces DNA denaturation in apoptotic nuclei but has no such effect on DNA of non-apoptotic cells. Formamide-induced DNA denaturation combined with detection of denatured DNA with a monoclonal antibody (MAb) against single-stranded DNA made it possible to specifically identify the apoptotic cells. This procedure produced intense staining of the condensed chromatin in the apoptotic nuclei. In contrast, necrotic cells from cultures treated with sodium azide, saponin, or hyperthermia did not bind this antibody, demonstrating the specificity of the formamide-MAb assay for the apoptotic cells. However, TUNEL stained 90-100% of necrotic cells in all three models of necrosis. Because the MAb did not stain cells with single- or double-stranded DNA breaks in the absence of apoptosis, we conclude that staining of the apoptotic nuclei is not influenced by DNA breaks and is induced by specific changes in condensed chromatin, such as damage to the DNA-histone interactions. Importantly, the formamide-MAb technique identified apoptotic cells in frozen sections and in histological sections of formalin-fixed, paraffin-embedded tissues.

Cell death beyond apoptosis

Though the term apoptosis was originated in pathology and developmental biology as an alternative to necrosis, the tissue necrosis with inflammation is irrelevant to cell culture conditions where apoptosis is mostly studied. Furthermore, no one single morphological feature is either necessary or sufficient to define apoptosis. The emerging biochemical definition, a cell death with caspase activation, allows the distinction of alternative forms of cell death. Thus, inhibition of caspases delays but does not prevent cell death. Slow cell death without caspase activation may nevertheless be associated with DNA fragmentation. Oncogenic Ras, Raf, and mitogen-activated kinases inhibit apoptosis by affecting the cytochrome C/caspase-9 pathway but may arrest growth and cause slow cell death with delayed DNA fragmentation. Such 'slow' cell death without caspase activation is often caused by chemotherapeutic drugs. Whether a cell will undergo apoptosis or slow death depends not only on a chemotherapeutic agent but also on the readiness of cellular caspases. Therefore, one can distinguish apoptosis-prone (eg leukemia) vs apoptosis-resistant cells. Cell susceptibilities to spontaneous, starvation-induced and drug-induced apoptosis are correlated and characterize an apoptosis-prone phenotype. Finally, distinction of slow cell death allows rephrasing of a question regarding the goal of cancer therapy: apoptosis vs slow cell death, or cancer cell-selectivity regardless of the mode of cell death.

Cleavage of Bax-alpha and Bcl-x(L) during carboplatin-mediated apoptosis in squamous cell carcinoma cell line

Although carboplatin (CBDCA) has been used for the treatment of several types of tumors, the complete response rate has been limited, probably because of inherent or CBDCA-induced resistance. As a first step to overcome these problems, we tried to elucidate the mechanisms of CBDCA-mediated cytotoxicity in the squamous cell carcinoma cell line MIT7. The treatment of cells with CBDCA resulted in apoptosis in a dose-dependent manner, as assessed by the propidium iodide staining method and DNA degradation in a nucleosomal pattern. The induction of apoptosis was accompanied by the decline of mitochondrial membrane potential (Deltapsi(m) ) at 12 h following CBDCA stimulation. Variant forms of p18 Bax-alpha and p16 Bcl-x(L) were generated with the down-regulation of both Bax-alpha (p21) and Bcl-x(L) (p31) at 36 and 48 h following CBDCA stimulation, suggesting that the modulation of Bcl-2 family proteins Bax-alpha and Bcl-x(L) play some role in CBDCA-mediated apoptosis. The activation of caspase-3 and -8 occurred at 12 and 24 h following the stimulation, respectively. The pretreatment of cells with pan-caspase inhibitor Z-VAD-fmk markedly prevented CBDCA-mediated cytotoxicity/apoptosis and the modulation of Bcl-2 family proteins (generation of p18 Bax-alpha and p16 Bcl-x(L) ) with only slight prevention of decline of Deltapsi(m). Taken together, these results may suggest that activation of several caspases, including caspase-3 and -8, plays some role in CBDCA-mediated apoptosis, probably through the modification of Bcl-2 family proteins, Bax-alpha and Bcl-x(L). Moreover, caspase activation may occur downstream of membrane depolarization.

Morphological features of Murray Valley encephalitis virus infection in the central nervous system of Swiss mice

We have examined the histological and ultrastructural features of CNS infection with Murray Valley encephalitis (MVE) virus in mice inoculated with a virulent parental strain (BH3479). Light microscopic examination revealed neuronal necrosis in the olfactory bulb and hippocampus of MVE-infected brains by 5 days post-infection (pi). Electron microscopy of these regions showed endoplasmic reticulum membrane proliferation, and tubular and spherical structures in the cisternae of the endoplasmic reticulum, Golgi complex and nuclear envelope. At seven to eight days pi, infected neurones exhibited chromatin condensation and extrusion, nuclear fragmentation, loss of segments of the nuclear envelope, reduced surface contact with adjacent cells and loss of cytoplasmic organelles. This cell injury was particularly noticeable in the proximal CA3 and distal CA1 regions of the hippocampus. The inflammatory cell profile consisted of macrophages, lymphocytes and especially neutrophils, and many of these inflammatory cells were apoptotic. High mortality rates in the BH3479-infected population of mice correlated with the intense polymorphonuclear and mononuclear leucocyte inflammatory infiltrate in the CNS.

Inhibition of apoptosis in human tumour cells by the tumour-associated serpin, SCC antigen-1

The squamous cell carcinoma antigen (SCC Ag) is a tumour-associated protein and a member of the serine protease inhibitor (serpin) family. The SCC Ag has been used as a serologic tumour marker for SCC progression, and its elevated serum levels are a risk factor for disease relapse. However, the biologic significance of this intracytoplasmic protein in cancer cells remains unknown. In this report, we demonstrated that apoptosis induced by 7-ethyl-10-hydroxycamptothecin, tumour necrosis factor-alpha (TNF-alpha) or interleukin (IL)-2-activated natural killer (NK) cells was significantly inhibited in tumour cells transduced with the SCC Ag-1 cDNA, as compared to control cells in vitro. Also, inhibition of the SCC Ag-1 expression in tumour cells by transfection of antisense SCC Ag-1 cDNA was accompanied by significantly increased sensitivity of these cells to apoptosis induced by etoposide or TNF-alpha. The mechanism of protection of tumour cells from apoptosis involved inhibition of caspase-3 activity and/or upstream proteases. In vivo, tumour cells overexpressing the SCC Ag-1 formed significantly larger tumours in nude mice than the SCC Ag-1-negative controls. Thus, overexpression of the SCC Ag-1, a member of the serpin family, in human cancer cells contributed to their survival by mediating protection from drug-, cytokine- or effector cell-induced apoptosis.

A Mycobacterium ulcerans toxin, mycolactone, causes apoptosis in guinea pig ulcers and tissue culture cells

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a tropical ulcerative skin disease. One of the most intriguing aspects of this disease is the presence of extensive tissue damage in the absence of an acute inflammatory response. We recently purified and characterized a macrolide toxin, mycolactone, from M. ulcerans. Injection of this molecule into guinea pig skin reproduced cell death and lack of acute inflammatory response similar to that seen following the injection of viable bacteria. We also showed that mycolactone causes a cytopathic effect on mouse fibroblast L929 cells that is characterized by cytoskeletal rearrangements and growth arrest within 48 h. However, these results could not account for the extensive cell death which occurs in Buruli ulcer. The results presented here demonstrate that L929 and J774 mouse macrophage cells die via apoptosis after 3 to 5 days of exposure to mycolactone. Treatment of cells with a pan-caspase inhibitor can inhibit mycolactone-induced apoptosis. We demonstrate that injection of mycolactone into guinea pig skin results in cell death via apoptosis and that the extent of apoptosis increases as the lesion progresses. These results may help to explain why tissue damage in Buruli ulcer is not accompanied by an acute inflammatory response.

Gene-specific repair of Pt/DNA lesions and induction of apoptosis by the oral platinum drug JM216 in three human ovarian carcinoma cell lines sensitive and resistant to cisplatin

JM216, an oral platinum drug entering into phase III clinical trial, exhibited comparable cytotoxicity to cisplatin in three human ovarian carcinoma cell lines: the sensitive (CH1), acquired resistant (CH1cisR) and intrinsically resistant (SKOV-3). Platinum accumulation and binding to DNA were similar in each of the three cell lines at equimolar doses, indicating that the resistant cell lines could tolerate higher intracellular platinum levels and platinum bound to DNA at IC50 concentrations of drug. Comparison with cisplatin demonstrated that intracellular platinum levels were marginally higher with JM216, but that platinum binding to DNA was similar for the two drugs in each of the cell lines. Each of the cell lines exhibited an ability to repair JM216 induced platinum/DNA lesions in the N-ras gene (gene-specific repair) at equitoxic concentrations of drug. However, this occurred to a greater extent in the two resistant cell lines such that by 24 h the CH1cisR and SKOV-3 had removed 72% and 67% respectively compared with approximately 32% for the CH1. Reduced gene-specific repair capacity in CH1 cells was also seen following incubation with 25 microM (or 5 microM - 2 x IC50) cisplatin, whereas the CH1cisR and SKOV-3 cell lines were repair proficient. JM216 induced apoptosis in the three cell lines following a 2h incubation with 2 x the IC50 of drug. Fluorescent microscopy of cells stained with propidium iodide showed that the detached cell population displayed typical apoptotic nuclei. Furthermore, field inversion gel electrophoresis demonstrated the presence of DNA fragments approximately 23-50 kb in size, indicative of apoptosis, in the detached cells. JM216 induced an S phase slow down in each of the three cell lines accompanied by a G2 block in the CH1 pair. Incubation with this concentration of JM216 also resulted in the induction of p53 in the CH1 and CH1cisR. These studies suggest that the relative sensitivity of the CH1 cell line to cisplatin and JM216 is at least partly attributable to a deficiency in gene-specific repair. The oral platinum drug, JM216, exerts its cytotoxic effects through the induction of apoptosis following a slow-down in S phase in both the sensitive and resistant lines.

The significance of apoptosis in the liver

Apoptosis is a form of cell death which occurs in normal as well as in pathological tissues. We provide a description of the morphological changes during apoptosis and an overview of the role of apoptosis dysregulation in the pathogenesis of non-neoplastic liver diseases.

Screening for inducers of apoptosis in apoptosis-resistant human carcinoma cells

Many anticancer agents are known to induce apoptosis in cultured cells, but human solid tumor cells are often resistant to apoptosis induction. Human pancreatic adenocarcinoma AsPC-1 cells were found to be resistant to apoptosis. So, we screened microbial culture filtrates and synthetic chemicals for their ability to induce apoptosis in AsPC-1 cells. Polyoxypeptin A was isolated from a Streptomyces culture broth as a potent inducer of apoptosis. Its cyclic hexadepsipeptide structure contains a simple but hitherto unreported amino acid, (2S,3R)-3-hydroxy-3-methylproline. Polyoxypeptin A induced early cell death, apoptotic morphology, and internucleosomal DNA fragmentation in AsPC-1 cells at low concentrations. Polyoxypeptin A can induce caspase 3 activation in human T cell leukemia Jurkat cells but not in AsPC-1 cells. The mechanism of apoptosis in AsPC-1 cells has not been elucidated yet. Less toxic derivatives of polyoxypeptin A are being prepared. A macrocyclic lactam called BE-14106 was also isolated from Streptomyces as an inducer of apoptosis in AsPC-1 cells. Histidine-pyridine-histidine-3 (HPH-3) is an oxygen-activating ligand derived from the structure of bleomycin, and it also induced apoptosis in AsPC-1 cells. Induction of apoptosis by HPH-3 was inhibited by zinc and copper ions, indicating that chelation with ferrous ion is responsible for induction of apoptosis, as is chelation by bleomycin to cleave DNA. Bleomycin A2 and its portion having no DNA-binding region, glycopeptide-3(GP-3), did not induce apoptosis in AsPC-1 cells. Thus, among the actions of bleomycin-related compounds, the induction of apoptosis is a unique characteristic of HPH-3.

Protein kinase C-dependent anti-apoptotic mechanism that is associated with high sensitivity to anti-Fas antibody in ovarian cancer cell lines

We compared the sensitivities to apoptosis via anti-Fas antibody of two human ovarian cancer cell lines, NOS4 and SKOV-3, both of which strongly express the Fas antigen on their cell surface. Treatment with anti-Fas antibody induced extensive DNA fragmentation in NOS4 cells but none in SKOV-3 cells. However; both cell lines underwent apoptosis in response to calcium ionophore A23187 or sphingomyelinase, demonstrating that the latter cell line is capable of DNA fragmentation. DNA fragmentation was not induced in either cell line by treatment with PKC activator PMA, however treatment with protein kinase C (PKC) inhibitor H-7 induced extensive DNA fragmentation in NOS4 cells, but again none in SKOV-3 cells. Protein kinase A inhibitor HA1004 treatment did not induce DNA fragmentation in either cell line. Correspondingly, treatment of cells with PMA before anti-Fas antibody or A23187 treatment partially inhibited induction of DNA fragmentation in NOS4 cells but not in SKOV-3 cells. Both NOS4 and SKOV-3 cell lines expressed isozymes of PKC at comparable levels. These results suggest the presence of a PKC-dependent anti-apoptotic mechanism in association with high sensitivity to anti-Fas antibody in these ovarian cancer cell lines.

Effects of methylprednisolone on human myeloid leukemic cells in vitro

We have demonstrated previously that high-dose methylprednisolone treatment induces differentiation and apoptosis of leukemic cells in patients with different morphological subtypes of acute myeloblastic leukemia (AML) in vivo. In the present study, we investigated the in vitro effects of high (10(-3) M) and low (10(-6) M) concentrations of methylprednisolone (MP) on freshly isolated bone marrow leukemic cells from nine newly diagnosed patients with AML by light and electron microscopy (EM) and agarose gel electrophoresis. A marked increase in MP-induced apoptosis of leukemic cells, with a maximum effect at 24 hr of exposure to both low and high concentrations of MP (10(-6) M and 10(-3) M), was demonstrated by light microscopy in cultures of four (three with AML-M1 and one with AML-M7) of the nine patients. In three cases, the increase in the number of apoptotic cells induced by high-concentration MP was approximately twice that observed when the lower concentration was used. A few apoptotic cells were detected in the cultures from the other five patients. However, a typical DNA ladder pattern of apoptosis was observed on gel electrophoresis of MP-treated leukemic cells from one patient (AML-M1) after 2 hr of incubation with both high- and low-MP concentrations. In two patients, a nonspecific DNA smear was observed only when high-concentration MP was used. The increase in differentiated leukemic cells induced by MP was also dose dependent, and was observed in cultures from all but one patient. Morphological features of apoptosis and differentiation were also confirmed by EM studies. The results of the present study, together with our previous clinical experience, suggest that MP, especially at high doses, could have a significant role in the treatment of some AML patients by inducing apoptosis and differentiation of leukemic cells.

Analysis of apoptosis by laser scanning cytometry

Flow cytometry techniques that are widely used in studies of cell death, and particularly in the identification of apoptotic cells, generally rely on the measurement of a single characteristic biochemical or molecular attribute. These methods fail to recognize cell death lacking that attribute, as in some examples of atypical apoptosis. Since apoptosis was originally defined by morphologic criteria, we suggest that for any new cell system the cytometry-defined apoptosis be confirmed by morphologic examination. This quality assurance measure is now provided by laser scanning cytometry (LSC). LSC measurements of cell fluorescence are precise and highly sensitive, comparable to flow cytometry (FCM), and can be carried out on cells on slides, permitting cell by cell correlation of fluorescence cytometry with visual microscopic morphology. In this report we describe adaptations of various flow cytometry techniques for detection of apoptosis by laser scanning cytometry. We also describe features unique to LSC that are useful in recognizing apoptosis. Hyperchromicity of DNA, reflecting chromatin condensation, is evidenced by high maximal pixel values for fluorescence of the DNA-bound fluorochrome. Mitochondrial probes that have been adapted to LSC to measure the drop in mitochondrial transmembrane potential that occurs early in apoptosis include rhodamine 123, 3,3'-dihexiloxadicarbocyanine [DiOC6(3)], and the aggregate dye 5,5',6,6'tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1). The changes in plasma membrane phospholipids and transport function, also early in apoptosis, are probed by a combination of the fluoresceinated annexin V and DNA fluorochromes such as propidium or 7-aminoactinomycin D. We also review methods of detection of apoptosis based on analysis of DNA fragmentation and their application to clinical oncology. Visual examination of the presumed apoptotic cells detected by cytometry makes it possible to discriminate those that are genuine from monocytes/macrophages that have ingested nuclear fragments via apoptotic bodies. Applications of flow cytometry and laser scanning cytometry in analysis of cell death are discussed and their respective advantages and disadvantages compared.