Arsenic Trioxide Induces Apoptosis in Chronic Myelogenous Leukemia K562 Cells:Possible Involvement of p38 MAP Kinase

Disease-associated metabolic pathways affected by heavy metals and metalloid

Increased exposure to environmental heavy metals and metalloids and their associated toxicities has become a major threat to human health. Hence, the association of these metals and metalloids with chronic, age-related metabolic disorders has gained much interest. The underlying molecular mechanisms that mediate these effects are often complex and incompletely understood. In this review, we summarize the currently known disease-associated metabolic and signaling pathways that are altered following different heavy metals and metalloids exposure, alongside a brief summary of the mechanisms of their impacts. The main focus of this study is to explore how these affected pathways are associated with chronic multifactorial diseases including diabetes, cardiovascular diseases, cancer, neurodegeneration, inflammation, and allergic responses upon exposure to arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), and vanadium (V). Although there is considerable overlap among the different heavy metals and metalloids-affected cellular pathways, these affect distinct metabolic pathways as well. The common pathways may be explored further to find common targets for treatment of the associated pathologic conditions.

Arsenic in medicine: past, present and future

Arsenicals are one of the oldest treatments for a variety of human disorders. Although infamous for its toxicity, arsenic is paradoxically a therapeutic agent that has been used since ancient times for the treatment of multiple diseases. The use of most arsenic-based drugs was abandoned with the discovery of antibiotics in the 1940s, but a few remained in use such as those for the treatment of trypanosomiasis. In the 1970s, arsenic trioxide, the active ingredient in a traditional Chinese medicine, was shown to produce dramatic remission of acute promyelocytic leukemia similar to the effect of all-trans retinoic acid. Since then, there has been a renewed interest in the clinical use of arsenicals. Here the ancient and modern medicinal uses of inorganic and organic arsenicals are reviewed. Included are antimicrobial, antiviral, antiparasitic and anticancer applications. In the face of increasing antibiotic resistance and the emergence of deadly pathogens such as the severe acute respiratory syndrome coronavirus 2, we propose revisiting arsenicals with proven efficacy to combat emerging pathogens. Current advances in science and technology can be employed to design newer arsenical drugs with high therapeutic index. These novel arsenicals can be used in combination with existing drugs or serve as valuable alternatives in the fight against cancer and emerging pathogens. The discovery of the pentavalent arsenic-containing antibiotic arsinothricin, which is effective against multidrug-resistant pathogens, illustrates the future potential of this new class of organoarsenical antibiotics.

Cellular and molecular alterations induced by low‑dose fisetin in human chronic myeloid leukemia cells

The present study aimed to evaluate the cellular and molecular effects of low concentrations of the flavonoid, fisetin, on K562 human chronic myeloid leukemia cells, in the context of both potential anti-proliferative and anti-metastatic effects. Thiazolyl blue tetrazolium bromide assay, Trypan blue exclusion assay, Annexin V/propidium iodide test, cell cycle analysis, Transwell migration and invasion assays, the fluorescence staining of β-catenin and F-actin as well as reverse transcription-quantitative polymerase chain reaction were performed to achieve the research goal. Furthermore, the nature of the interaction between fisetin and arsenic trioxide in the K562 cells was analyzed according to the Chou-Talalay median-effect method. We found that low concentrations of fisetin had not only a negligible effect on the viability and apoptosis of the K562 cells, but also modulated the mRNA levels of selected metastatic-related markers, accompanied by an increase in the migratory and invasive properties of these cancer cells. Although some markers of cell death were significantly elevated in response to fisetin treatment, these were counterbalanced through anti-apoptotic and pro-survival signals. With decreasing concentrations of fisetin and arsenic trioxide, the antagonistic interactions between the 2 agents increased. On the whole, the findings of this study suggest that careful consideration should be taken when advising cancer patients to take fisetin as a dietary supplement and when considering fisetin as a potential candidate for the treatment of chronic myeloid leukemia. Further more detailed studies are required to confirm our findings.

Double-Sided Personality: Effects of Arsenic Trioxide on Inflammation

In 1992, arsenic trioxide (As₂O₃, ATO) was demonstrated to be an effective therapeutic agent against acute promyelocytic leukemia (APL), rekindling attention to ATO applications in U.S. Food and Drug Administration clinical trials for the treatment of cancers, such as leukemia, lymphomas, and solid tumors. ATO is a potent chemotherapeutic drug that can also be used to treat other diseases, such as autoimmune diseases, because it affects multiple pathways including apoptosis induction, differentiation stimulation, and proliferation inhibition. As inflammation is a critical component of disease progression, ATO is a feasible treatment option based on its ability to protect against inflammation. However, ATO is also a well-known carcinogen because of its pro-inflammatory effect. This review will focus on the double-sided effects of ATO on inflammation as well as the relevant mechanisms underlying these effects, aiming to provide a rational understanding of how ATO effects the immune system. We especially aim to provide a comprehensive overview of our current knowledge of how ATO influences inflammation.

Trisenox induces cytotoxicity through phosphorylation of mitogen-activated protein kinase molecules in acute leukemia cells

Trisenox (TX) has been used successfully for the treatment of acute promyelocytic leukemia (APL) patients. TX-induced cytotoxicity in APL cells remains poorly understood. In this study, we investigated the molecular mechanism of TX cytotoxicity using APL cell lines. We assessed TX toxicity by quantitatively measuring lactate dehydrogenase levels. Inhibition of cell cycle progression was assessed by confocal microscopy of Ki-67 expression. Apoptosis was evaluated by Western blot analysis of apoptotic proteins expression, immunocytochemistry, and confocal imaging of annexin V and propidium iodide. Mitogen-activated protein kinase (MAPK) signaling cascade was analyzed by Western blot analysis and inhibitor-based experiments with APL cells. We found that TX-induced cytotoxicity inhibited APL cell cycle progression. TX also induced significant (P < 0.05) changes in the expression levels of apoptotic molecules and activated the phosphorylation of MAPK signaling pathways in APL cells. Understanding the mechanism of TX cytotoxicity would be helpful in the design of new APL drugs.

Evaluation of Arsenic Trioxide Potential for Lung Cancer Treatment: Assessment of Apoptotic Mechanisms and Oxidative Damage

Background

Lung cancer is one of the most lethal and common cancers in the world, causing up to 3 million deaths annually. The chemotherapeutic drugs that have been used in treating lung cancer include cisplatin-pemetrexed, cisplastin-gencitabinoe, carboplatin-paclitaxel and crizotinib. Arsenic trioxide (ATO) has been used in the treatment of acute promyelocytic leukemia. However, its effects on lung cancer are not known. We hypothesize that ATO may also have a bioactivity against lung cancer, and its mechanisms of action may involve apoptosis, DNA damage and changes in stress-related proteins in lung cancer cells.

Methods

To test the above stated hypothesis, lung carcinoma (A549) cells were used as the test model. The effects of ATO were examined by performing 6-diamidine-2 phenylindole (DAPI) nuclear staining for morphological characterization of apoptosis, flow cytometry analysis for early apoptosis, and western blot analysis for stress-related proteins (Hsp70 and cfos) and apoptotic protein expressions. Also, the single cell gel electrophoresis (Comet) assay was used to evaluate the genotoxic effect.

Results

ATO-induced apoptosis was evidenced by chromatin condensation and formation of apoptotic bodies as revealed by DAPI nuclear staining. Cell shrinkage and membrane blebbing were observed at 4 and 6 µg/ml of ATO. Data from the western blot analysis revealed a significant dose-dependent increase (p < 0.05) in the Hsp 70, caspase 3 and p53 protein expression, and a significant (p < 0.05) decrease in the cfos, and bcl-2 protein expression at 4 and 6 µg/ml of ATO. There was a slight decrease in cytochrome c protein expression at 4 and 6 µg/ ml of ATO. Comet assay data revealed significant dose-dependent increases in the percentages of DNA damage, Comet tail lengths, and Comet tail moment.

Conclusion

Taken together our results indicate that ATO is cytotoxic to lung cancer cells and its bioactivity is associated with oxidative damage, changes in cellular morphology, and apoptosis.

Resveratrol protects against arsenic trioxide-induced oxidative damage through maintenance of glutathione homeostasis and inhibition of apoptotic progression

Arsenic trioxide (As2 O3 ) is commonly used to treat acute promyelocytic leukemia and solid tumors. However, the clinical application of the agent is limited by its cyto- and genotoxic effects on normal cells. Thus, relief of As2 O3 toxicity in normal cells is essentially necessary for improvement of As2 O3 -mediated chemotherapy. In this study, we have identified a series of protective effects of resveratrol against As2 O3 -induced oxidative damage in normal human bronchial epithelial (HBE) cells. We showed that treatment of HBE cells with resveratrol significantly reduced cellular levels of DNA damage, chromosomal breakage, and apoptosis induced by As2 O3 . The effect of resveratrol against DNA damage was associated with a decreased level of reactive oxygen species and lipid peroxidation in cells treated by As2 O3 , suggesting that resveratrol protects against As2 O3 toxicity via a cellular anti-oxidative stress pathway. Further analysis of the roles of resveratrol demonstrated that it modulated biosynthesis, recycling, and consumption of glutathione (GSH), thereby promoting GSH homeostasis in HBE cells treated by As2 O3 . This was further supported by results showing that resveratrol prevented an increase in the activities and levels of caspases, Fas, Fas-L, and cytochrome c proteins induced by As2 O3 . Our study indicates that resveratrol relieves As2 O3 -induced oxidative damage in normal human lung cells via maintenance of GSH homeostasis and suppression of apoptosis.

The effect of nilotinib plus arsenic trioxide on the proliferation and differentiation of primary leukemic cells from patients with chronic myoloid leukemia in blast crisis

Aim

To determine the effects of arsenic trioxide (ATO) and nilotinib (AMN107, Tasigna) alone or in combination on the proliferation and differentiation of primary leukemic cells from patients with chronic myeloid leukemia in the blast crisis phase (CML-BC).

Methods

Cells were isolated from the bone marrow of CML-BC patients and were treated with 1 μM ATO and 5 nM nilotinib, either alone or in combination. Cell proliferation was evaluated using a MTT assay. Cell morphology and the content of hemoglobin were examined with Wright-Giemsa staining and benzidine staining, respectively. The expression of cell surface markers was determined using flow cytometric analysis. The levels of mRNA and protein were analyzed using RT-PCR and Western blotting, respectively.

Results

ATO and nilotinib alone or in combination suppressed cell proliferation in a dose- and time-dependent pattern (P < 0.01 vs. control). Drug treatments promoted erythroid differentiation of CML-BC cells, with a decreased nuclei/cytoplasm ratio but increased hemoglobin content and glycophorin A (GPA) expression (P < 0.01 compared with control). In addition, macrophage and granulocyte lineage differentiation was also induced after drug treatment. The mRNA and protein levels of basic helix-loop-helix (bHLH) transcription factor T-cell acute lymphocytic leukemia protein 1 (TAL1) and B cell translocation gene 1 (BTG1) were both upregulated after 3 days of ATO and Nilotinib treatment.

Conclusions

Our findings indicated that ATO and nilotinib treatment alone or in combination greatly suppressed cell proliferation but promoted the differentiation of CML-BC cells towards multiple-lineages. Nilotinib alone preferentially induced erythroid differentiation while combined treatment with ATO preferentially induced macrophage and granulocyte lineage differentiation.

The two opposite facets of arsenic: toxic and anticancer drug

Arsenic compounds have been known and used for centuries but their effects in living organisms still represent a large unknown. Arsenic compounds have paradoxical effects: they are threatening to human health, especially upon long-term exposure that can induce the development of cancer; however, they are used as drugs against cancer. This review focuses on the effects shown by clinically and environmentally relevant arsenic compounds in living organisms with a focus on the calcium–apoptosis link.

SUMO1 negatively regulates the transcriptional activity of EVI1 and significantly increases its co-localization with EVI1 after treatment with arsenic trioxide

Aberrant expression of the proto-oncogene EVI1 (ecotropic virus integration site1) has been implicated not only in myeloid or lymphoid malignancies but also in colon, ovarian and breast cancers. Despite its importance in oncogenesis, the regulatory factors and mechanisms that potentiate the function of EVI1 and its consequences are partially known. Here we demonstrated that EVI1 is post-translationally modified by SUMO1 at lysine residues 533, 698 and 874. Although both EVI1 and SUMO1 were found to co-localize in nuclear speckles, the sumoylation mutant of EVI1 failed to co-localize with SUMO1. Sumoylation abrogated the DNA binding efficiency of EVI1 and also affected EVI1 mediated transactivation. The SUMO ligase PIASy was found to play a bi-directional role on EVI1, PIASy enhanced EVI1 sumoylation and augmented sumoylated EVI1 mediated repression. PIASy was also found to interact with EVI1 and impaired EVI1 transcriptional activity independent of its ligase activity. Arsenic trioxide (ATO) known to act as an antileukemic agent for acute promyelocytic leukemia (APL) not only enhanced EVI1 sumoylation but also enhanced the co-localization of EVI1 and SUMO1 in nuclear bodies distinct from PML nuclear bodies. ATO treatment also affected the Bcl-xL protein expression in EVI1 positive cell line. Thus, the results showed that arsenic treatment enhanced EVI1 sumoylation, deregulated Bcl-xL, which eventually may induce apoptosis in EVI1 positive cancer cells. The study for the first time explores and reports sumoylation of EVI1, which plays an essential role in regulating its function.

Arsenic trioxide induces cardiac fibroblast apoptosis in vitro and in vivo by up-regulating TGF-β1 expression

Arsenic trioxide (As2O3; ATO) is clinically effective in treating acute promyelocytic leukemia (APL); however, it frequently causes cardiotoxic effects. This study was designed to investigate whether ATO could induce apoptosis of cardiac fibroblasts (CFs) that play very important roles in maintaining the structure integrity and function of the heart. Cardiac fibroblasts from guinea pigs administered with ATO (1mg/kgbw) were used to test the pro-apoptotic role of ATO in vivo. The current study demonstrated that ATO induced morphological characteristics of apoptosis and Caspase-3 activation in CFs of guinea pigs along with a significant up-regulation in TGF-β1 protein expression, Bax/Bcl-2 ratio and ERK1/2 phosphorylation. In vitro MTT assay showed that ATO remarkably reduced the viability of cultured cardiac fibroblasts (NRCFs) from neonatal rat in a concentration- and time-dependent manner. Consistent with the notions in vivo, ATO significantly induced the apoptosis in NRCFs, dramatically up-regulated TGF-β1 protein level and Bax/Bcl-2 ratio in a time-dependent fashion and activated Caspase-3 and ERK1/2. Finally, pretreatment with LY364947, an inhibitor of TGF-β signaling could apparently reverse these changes. We therefore conclude that TGF-β is functionally linked to ERK1/2 and that TGF-β signaling is responsible for ATO-induced CFs apoptosis, which provides a novel mechanism of ATO related cardiac toxicology.

Therapeutic effect of Arsenicum album on leukocytes

The therapeutic effects of homoeopathic Arsenicum album potencies were investigated in-vitro, using a continuous cell line (MT4), pre-intoxicated with arsenic trioxide (As(2)O(3)), and then treated with succussed and unsuccussed homoeopathic potencies, 6CH, 30CH and 200CH. This study aimed to verify the homoeopathic law of similars and to determine whether potencies diluted beyond Avogadro's constant had physiological effects on cells; whether various potencies would cause different effects as suggested by the concept of hormesis; whether succussed and unsuccussed homoeopathic potencies had different effects on the cells; and to establish whether a biotechnological method could be used to evaluate the above. As(2)O(3) was used to pre-intoxicate and the MTT assay was used to measure the percentage cytotoxicity and half maximal inhibitory concentration (IC(50)) of the cells. The homoeopathic potencies of Arsenicum album (6CH, 30CH and 200CH) were prepared by either succussing or allowing to diffuse for 30 s. After pre-intoxication of the MT4 cells with the IC(50) As(2)O(3) and treatment with succussed and unsuccussed Arsenicum album (6CH-200CH), the cell viability increased with increasing potency from 81% to 194% (over 72 h). The treatments and the times of exposure were found to be statistically significant determinants of cell viability, whereas succussion did not cause any significant variation in the results. The study provided evidence that a biotechnological method (namely cell viability) may be used to scientifically evaluate the physiological effects of homoeopathic potencies on human cells; it confirmed that the homoeopathic potencies did have therapeutic effects; and that succussion was not required in the potentization method in order to produce a curative remedy.

Effect of size and processing method on the cytotoxicity of realgar nanoparticles in cancer cell lines

In this study, the effects of the size and Chinese traditional processing (including elutriation, water cleaning, acid cleaning, alkali cleaning) on realgar nanoparticles (RN)-induced antitumor activity in human osteosarcoma cell lines (MG-63) and hepatoma carcinoma cell lines (HepG-2) were investigated. The human normal liver cell line (L-02) was used as control. RN was prepared by high-energy ball milling technology. The results showed that with the assistance of sodium dodecyl sulfate, the size of realgar could be reduced to 127 nm after 12 hours’ ball milling. The surface charge was decreased from 0.83 eV to −17.85 eV and the content of As₂O₃ clearly increased. Except for elutriation, the processing methods did not clearly change the size of the RN, but the content of As₂O₃ was reduced dramatically. In vitro MTT tests indicated that in the two cancer cell lines, RN cytotoxicity was more intense than that of the coarse realgar nanoparticles, and cytotoxicity was typically time- and concentration-dependent. Also, RN cytotoxicities in the HepG-2 and L-02 cells all increased with increasing milling time. Due to the reduction of the As₂O₃ content, water cleaning, acid cleaning, and alkali cleaning decreased RN cytotoxicity in HepG-2, but RN after elutriation, with the lowest As₂O₃ (3.5 mg/g) and the smallest size (109.3 nm), showed comparable cytotoxicity in HepG-2 to RN without treatment. Meanwhile, RN-induced cytotoxicity in L-02 cells was clearly reduced. Therefore, it can be concluded that RN may provide a strong antiproliferation effect in the MG-63 and HepG-2 cells. Elutriation processing is a suitable approach to limit the dangerous side-effects of As₂O₃, while maintaining the effectiveness of RN.

Arsenic-induced alteration in intracellular calcium homeostasis induces head kidney macrophage apoptosis involving the activation of calpain-2 and ERK in Clarias batrachus

We had earlier shown that exposure to arsenic (0.50 μM) caused caspase-3 mediated head kidney macrophage (HKM) apoptosis involving the p38-JNK pathway in Clarias batrachus. Here we examined the roles of calcium (Ca(2+)) and extra-cellular signal-regulated protein kinase (ERK), the other member of MAPK-pathway on arsenic-induced HKM apoptosis. Arsenic-induced HKM apoptosis involved increased expression of ERK and calpain-2. Nifedipine, verapamil and EGTA pre-treatment inhibited the activation of calpain-2, ERK and reduced arsenic-induced HKM apoptosis as evidenced from reduced caspase-3 activity, Annexin V-FITC-propidium iodide and Hoechst 33342 staining. Pre-incubation with ERK inhibitor U 0126 inhibited the activation of calpain-2 and interfered with arsenic-induced HKM apoptosis. Additionally, pre-incubation with calpain-2 inhibitor also interfered with the activation of ERK and inhibited arsenic-induced HKM apoptosis. The NADPH oxidase inhibitor apocynin and diphenyleneiodonium chloride also inhibited ERK activation indicating activation of ERK in arsenic-exposed HKM also depends on signals from NADPH oxidase pathway. Our study demonstrates the critical role of Ca(2+) homeostasis on arsenic-induced HKM apoptosis. We suggest that arsenic-induced alteration in intracellular Ca(2+) levels initiates pro-apoptotic ERK and calpain-2; the two pathways influence each other positively and induce caspase-3 mediated HKM apoptosis. Besides, our study also indicates the role of ROS in the activation of ERK pathway in arsenic-induced HKM apoptosis in C. batrachus.

Arsenic trioxide reduces drug resistance to adriamycin in leukemic K562/A02 cells via multiple mechanisms

The present study aimed to study the mechanisms by which low dose arsenic trioxide (As(2)O(3)) reduces multidrug resistance. The potential influence of As(2)O(3) on cytotoxicity was examined by methyl thiazolyl tetrazolium (MTT) assay and the intracellular mean fluorescence intensity (MFI) of Adriamycin (ADM) was examined by flow cytometry. The gene expression of mdr1 mRNA was determined by RT-PCR. The change of cellular expression levels of drug resistant-related proteins, including P-gp, bcl-2, Topo-II, and GST-π, were measured by Western-blotting or immunocytochemistry assay. Data showed As(2)O(3) at non-cytotoxic concentration (2μM) significantly increased the cytotoxicity of ADM on K562/A02 cells. Cotreatment of As(2)O(3) and ADM significantly increased the ADM MFI than ADM alone (P<0.01). Following pretreatment of K562/A02 cells with As(2)O(3), the expression of Topo-II was increased while the expression of GST-π and bcl-2 was decreased. No obvious alternation of expression of mdr1 mRNA or P-gp was observed. Thus, low dose As(2)O(3) partially reduced drug resistance to ADM in K562/A02 cells via multiple mechanisms, which selectively inhibited the efflux pump GST-π but not P-gp, as well as modulated the expression of MDR-related proteins such as Topo-II and bcl-2, in line with previous studies. In conclusions: The effect of As(2)O(3) on reducing MDR may have wide clinical application in chemotherapy regimens for leukemia.

Proliferation-attenuating and apoptosis-inducing effects of tryptanthrin on human chronic myeloid leukemia K562 cell line in vitro

Tryptanthrin, a kind of indole quinazoline alkaloid, has been shown to exhibit anti-microbial, anti-inflammation and anti-tumor effects both in vivo and in vitro. However, its biological activity on human chronic myeloid leukemia cell line K562 is not fully understood. In the present study, we investigated the proliferation-attenuating and apoptosis-inducing effects of tryptanthrin on leukemia K562 cells in vitro and explored the underlying mechanisms. The results showed that tryptanthrin could significantly inhibit K562 cells proliferation in a time- and dose-dependent manner as evidenced by MTT assay and flow cytometry analysis. We also observed pyknosis, chromatin margination and the formation of apoptotic bodies in the presence of tryptanthrin under the electron microscope. Nuclei fragmentation and condensation by Hoechst 33258 staining were detected as well. The amount of apoptotic cells significantly increased whereas the mitochondrial membrane potential decreased dramatically after tryptanthrin exposure. K562 cells in the tryptanthrin treated group exhibited an increase in cytosol cyt-c, Bax and activated caspase-3 expression while a decrease in Bcl-2, mito cyt-c and pro-caspase-3 contents. However, the changes of pro-caspase-3 and activated caspase-3 could be abolished by a pan-caspase inhibitor ZVAD-FMK. These results suggest that tryptanthrin has proliferation-attenuating and apoptosis-inducing effects on K562 cells. The underlying mechanism is probably attributed to the reduction in mitochondria membrane potential, the release of mito cyt-c and pro-caspase-3 activation.

Analysis of genomic dose-response information on arsenic to inform key events in a mode of action for carcinogenicity

A comprehensive literature search was conducted to identify information on gene expression changes following exposures to inorganic arsenic compounds. This information was organized by compound, exposure, dose/concentration, species, tissue, and cell type. A concentration-related hierarchy of responses was observed, beginning with changes in gene/protein expression associated with adaptive responses (e.g., preinflammatory responses, delay of apoptosis). Between 0.1 and 10 microM, additional gene/protein expression changes related to oxidative stress, proteotoxicity, inflammation, and proliferative signaling occur along with those related to DNA repair, cell cycle G2/M checkpoint control, and induction of apoptosis. At higher concentrations (10-100 microM), changes in apoptotic genes dominate. Comparisons of primary cell results with those obtained from immortalized or tumor-derived cell lines were also evaluated to determine the extent to which similar responses are observed across cell lines. Although immortalized cells appear to respond similarly to primary cells, caution must be exercised in using gene expression data from tumor-derived cell lines, where inactivation or overexpression of key genes (e.g., p53, Bcl-2) may lead to altered genomic responses. Data from acute in vivo exposures are of limited value for evaluating the dose-response for gene expression, because of the transient, variable, and uncertain nature of tissue exposure in these studies. The available in vitro gene expression data, together with information on the metabolism and protein binding of arsenic compounds, provide evidence of a mode of action for inorganic arsenic carcinogenicity involving interactions with critical proteins, such as those involved in DNA repair, overlaid against a background of chemical stress, including proteotoxicity and depletion of nonprotein sulfhydryls. The inhibition of DNA repair under conditions of toxicity and proliferative pressure may compromise the ability of cells to maintain the integrity of their DNA.

Arsenic trioxide enhances the therapeutic efficacy of radiation treatment of oral squamous carcinoma while protecting bone

Therapeutic radiation is commonly used in the treatment of squamous cell carcinoma of the oral cavity and pharynx. Despite the proven efficacy of this form of anticancer therapy, high-dose radiation treatment is invariably associated with numerous unwanted side effects. This is particularly true for bone, in which radiation treatment often leads to osteoradionecrosis. The aim of this study was to investigate if treatment with arsenic trioxide (As(2)O(3)) could enhance the antitumor effect of radiotherapy whereas minimizing the destructive effects of radiation on bone. As(2)O(3) treatment induced a dose-dependent (1-20 mumol/L) inhibition of endothelial and tumor cell (OSCC-3 and UM-SCC-74A) survival and significantly enhanced radiation-induced endothelial cell and tumor cell death. In contrast, As(2)O(3) treatment (0.5-7.5 mumol/L) induced the proliferation of osteoblasts and also protected osteoblasts against radiation-induced cell death. Furthermore, As(2)O(3) treatment was able to significantly enhance radiation-induced inhibition of endothelial cell tube formation and tumor cell colony formation. To test the effectiveness of As(2)O(3) and radiation treatment in vivo, we used a severe combined immunodeficiency mouse model that has a bone ossicle and tumor growing side by side subcutaneously. Animals treated with As(2)O(3) and radiation showed a significant inhibition of tumor growth, tumor angiogenesis, and tumor metastasis to the lungs as compared with As(2)O(3) treatment or radiation treatment alone. In contrast, As(2)O(3) treatment protected bone ossicles from radiation-induced bone loss. These results suggest a novel strategy to enhance the therapeutic efficacy of radiation treatment while protecting bone from the adverse effects of therapeutic radiation.

Arsenic trioxide (As2O3) induced calcium signals and cytotoxicity in two human cell lines: SY-5Y neuroblastoma and 293 embryonic kidney (HEK)

Arsenic trioxide (As(2)O(3)) has anticancer properties; however, its use also leads to neuro-, hepato- or nephro-toxicity, and therefore, it is important to understand the mechanism of As(2)O(3) toxicity. We studied As(2)O(3) influence on intracellular calcium ([Ca(2+)](i)) homeostasis of human neuroblastoma SY-5Y and embryonic kidney cells (HEK 293). We also relate the As(2)O(3) induced [Ca(2+)](i) modifications with cytotoxicity. We used Ca(2+) sensitive dyes (fluo-4 and rhod-2) combined with laser scanning microscopy or fluorescence activated cell sorting to measure Ca(2+) changes during the application of As(2)O(3) and we approach evaluation of cytotoxicity. As(2)O(3) (1 microM) increased [Ca(2+)](i) in SY-5Y and HEK 293 cells. Three forms of [Ca(2+)](i)-elevations were found: (1) steady-state increases, (2) transient [Ca(2+)](i)-elevations and (3) Ca(2+)-spikes. [Ca(2+)](i) modifications were independent from extracellular Ca(2+) but dependent on internal calcium stores. The effect was not reversible. Inositol triphosphate (IP(3)) and ryanodine (Ry) receptors are involved in regulation of signals induced by As(2)O(3). 2-APB and dantrolene significantly reduced the [Ca(2+)](i)-rise (p<0.001, t-test) but did not completely abolish [Ca(2+)](i)-elevation or spiking. This indicates that other Ca(2+) regulating mechanisms are involved. In cytotoxicity tests As(2)O(3) significantly reduced cell viability in both cell types. Staining with Hoechst 33342 showed occurrence of apoptosis and DNA damage. Our data suggest that [Ca(2+)](i) is an important messenger in As(2)O(3) induced cell death.

GATA-1 and Gfi-1B interplay to regulate Bcl-xL transcription

The induction of Bcl-x(L) is critical for the survival of late proerythroblasts. The erythroid-specific transcriptional network that regulates Bcl-x(L) expression in erythropoiesis remains unclear. The activation of the central erythropoietic transcriptional factor, GATA-1, leads to the early, transient induction of a transcription repressor, Gfi-1B, followed by the late induction of Bcl-x(L) during erythroid maturation in G1ER cells. Chromatin immunoprecipitation assays demonstrated that a constant level of GATA-1 binds to the Bcl-x promoter throughout the entire induction period, while Gfi-1B is transiently associated with the promoter in the early phase. The sustained expression of Gfi-1B abolished GATA-1-induced Bcl-x(L) expression. Here, we present evidence that GATA-1 binds to the noncanonical GATT motif of the Bcl-x promoter for trans-activation. Gfi-1B expressed at increased levels is recruited to the Bcl-x promoter through its association with GATA-1, suppressing Bcl-x(L) transcription. Therefore, the down-regulation of Gfi-1B in the late phase of erythroid maturation is necessary for Bcl-x(L) induction. Furthermore, we show that the inhibition of Bcr-Abl kinase by treatment with imatinib caused the up-regulation of Gfi-1B in K562 cells, where Gfi-1B also cooperated with GATA-1 to repress Bcl-x(L) transcription. Gfi-1B knockdown by RNA interference diminished imatinib-induced apoptosis, while the overexpression of Gfi-1B sensitized K562 cells to arsenic-induced death. These findings illuminate the role of Gfi-1B in GATA-1-mediated transcription in the survival aspect of erythroid cells.

Buthionine sulfoximine enhancement of arsenic trioxide-induced apoptosis in leukemia and lymphoma cells is mediated via activation of c-Jun NH2-terminal kinase and up-regulation of death receptors

The mechanism of apoptosis induced by treatment with As(2)O(3) alone or in combination with buthionine sulfoximine (BSO) was studied in NB4, U937, Namalwa, and Jurkat cells. As(2)O(3) at concentrations <2 micromol/L induced apoptosis in NB4 cells and Namalwa cells but not in U937 and Jurkat cells. As(2)O(3)-induced apoptosis in NB4 cells and Namalwa cells correlated with increase of H(2)O(2) and caspase activation without activation of c-Jun NH(2)-terminal kinase (JNK). BSO (10 micromol/L) depleted the reduced form of intracellular glutathione without inducing apoptosis but synergized with 1 micromol/L As(2)O(3) to induce apoptosis in all four cell lines. This synergy correlated with JNK activation. Treatment with As(2)O(3) plus BSO, but not with As(2)O(3) alone, increased the levels of death receptor (DR) 5 protein and caspase-8 cleavage. The JNK inhibitor SP600125 inhibited the increase in DR5 protein and attenuated apoptosis induced by treatment with As(2)O(3) plus BSO. These observations suggest that a DR-mediated pathway activated by JNK is involved in apoptosis induced by treatment with As(2)O(3) plus BSO.

Inhibition of mitogen-activated protein kinase kinase enhances apoptosis induced by arsenic trioxide in human breast cancer MCF-7 cells

Arsenic trioxide (As2O3) has recently been used to treat acute promyelocytic leukaemia and has activity in vitro against several solid tumour cell lines where the induction of differentiation and apoptosis are the prime effects. The mechanism of As2O3-induced cell death has yet to be clarified, especially in solid cancers. In the present study, the human breast cancer cell line MCF-7 was examined as a cellular model for As2O3 treatment. The involvement of extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) was investigated in As2O3-induced cell death. 3. It was found that As2O3 activates the prosurvival mitogen-activated protein kinase kinase (MEK)/ERK pathway in MCF-7 cells, which, conversely, may compromise the efficacy of As2O3. Hence, a combination treatment of As2O3 and MEK inhibitors was investigated to determine whether this treatment could lead to enhanced growth inhibition and apoptosis in MCF-7 cells. 4. Inhibition of MEK/ERK with the pharmacological inhibitors U0126 (10 micromol/L) or PD98059 (20 micromol/L) together with As2O3 (2 and 5 micromol/L) resulted in a significant enhancement of growth inhibition in breast cancer MCF-7 cells as determined by the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide assay and [Methyl-3H]-thymidine incorporation. Furthermore, the results demonstrated that combined treatment with As2O3 and the MEK1/2 inhibitor U0126 could augment breast cancer MCF-7 cell apoptosis approximately twofold compared with the effects of the two drugs alone, as determined by Hoechst 33258 or annexin V/propidium iodide (PI) staining and flow cytometry. 5. In addition, As2O3 activated p38 in a dose-dependent manner, but had no effect on JNK1/2. Treatment with a p38 inhibitor did not prevent As2O3-induced apoptosis. 6. In conclusion, the results of the present study showed that enhanced apoptosis is detected in breast cancer MCF-7 cells in the presence of As2O3 and an MEK inhibitor, which may be a new promising adjuvant to current breast cancer treatments.

Arsenic trioxide: an anti cancer missile with multiple warheads

The proven efficacy of ATO in the treatment of APL and the emerging importance of ATO in other diseases prompted extensive studies of the mechanisms of action of ATO in APL and in other types of cancers. In this review we will focus on downstream events in ATO-induced intrinsic and extrinsic apoptotic pathways with an emphasis on the role of pro-apoptotic and anti-apoptotic proteins and the role of p53 in ATO-induced apoptosis including its effect on cell cycle, its anti-mitotic effect and the role of apoptosis inducing factors (AIF) in ATO-induced apoptosis, chromatin condensation and nuclear fragmentation in myeloma cells as a model.

Curcumin Derivatives Inhibit the Formation of Jun-Fos-DNA Complex Independently of their Conserved Cysteine Residues

Curcumin, a major active component of turmeric, has been identified as an inhibitor of the transcriptional activity of activator protein-1 (AP-1). Recently, it was also found that curcumin and synthetic curcumin derivatives can inhibit the binding of Jun-Fos, which are the members of the AP-1 family, to DNA. However, the mechanism of this inhibition by curcumin and its derivatives was not disclosed. Since the binding of Jun-Fos dimer to DNA can be modulated by redox control involving conserved cysteine residues, we studied whether curcumin and its derivatives inhibit Jun-Fos DNA binding activity via these residues. However, the inhibitory mechanism of curcumin and its derivatives, unlike that of other Jun-Fos inhibitors, was found to be independent of these conserved cysteine residues. In addition, we investigated whether curcumin derivatives can inhibit AP-1 transcriptional activity in vivo using a luciferase assay. We found that, among the curcumin derivatives examined, only inhibitors shown to inhibit the binding of Jun-Fos to DNA by Electrophoretic Mobility Shift Assay (EMSA) inhibited AP-1 transcriptional activity in vivo. Moreover, RT-PCR revealed that curcumin derivatives, like curcumin, downregulated c-jun mRNA in JB6 cells. These results suggest that the suppression of the formation of DNA-Jun-Fos complex is the main cause of reduced AP-1 transcriptional activity by curcuminoids, and that EMSA is a suitable tool for identifying inhibitors of transcriptional activation.

Regulating expressions of cyclin D1, pRb, and anti-cancer effects of deguelin on human Burkitt's lymphoma Daudi cells in vitro

AIM

To investigate anticancer effects and molecular mechanism of deguelin on human Burkittos lymphoma Daudi cells in vitro and compare the cytotoxicities of deguelin on Daudi cells and human peripheral blood monocular cells (PBMC).

METHODS

The effects of deguelin on the growth of Daudi cells were studied by 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium (MTT) assay. Apoptosis were detected through Hoechst 33258 staining and Annexin V/PI double-labeled cytometry. The effect of deguelin on the cell cycle of Daudi cells were studied by a propidium iodide method. The expressions of cyclin D1 and pRb were checked by Western blot.

RESULTS

The proliferation of Daudi cells were decreased in deguelin-treated group with a 24-h IC50 value of 51.55 nmol/L. Deguelin induced Daudi cells apoptosis was in a time- and dose-dependent manner. G0/G1 phase increased and S phase decreased in Daudi cells treated with deguelin. With deguelin 0, 5, 10, 20, and 40 nmol/L treatment for 24 h, G0/G1 phase increased from 37.34% to 56.56%, whereas S phase decreased from 37.72% to 21.36%. PBMC was less sensitive to the cytotoxic effect of deguelin than Daudi cells. The expression of cyclin D1 and pRb protein were decreased sharply in Daudi cells treated with deguelin.

CONCLUSION

Deguelin is able to inhibit the proliferation of Daudi cells by regulating the cell cycle that arrested cells at G0/G1 phase and inducing the cell apoptosis. Moreover, deguelin selectively induced apoptosis of Daudi cells with low toxicity in PBMC. The antitumor effects of deguelin were related to down-regulating the expression of cyclin D1 and pRb protein.

Arsenic trioxide therapy in acute promyelocytic leukemia and beyond: from bench to bedside

Arsenic trioxide (As2O3) has a long history of use in medicine. However, it was almost forgotten in Western medicine in the recent centuries. Prompted by reports from China about successful treatment of acute promyelocytic leukemia (APL) with As2O3, there was again increasing interest in this drug in the 1990s. This review summarizes the considerable knowledge about the mechanisms of action of As2O3 that was gained during the last 5-10 years. It is focused in particular on the effects of As2O3 in non-APL cells. Since As2O3 seems to induce apoptosis and inhibits growth in a large variety of cellular targets, it might become an alternative or adjunct drug to conventional chemotherapy. As2O3 can even be effective in cells resistant to conventional cytostatic agents. Insight into the cellular mechanisms, in particular the impact of the redox state on sensitivity towards As2O3 opens the possibility to enhance As2O3 effects by appropriate combination therapies.

Morin inhibits 12-O-tetradecanoylphorbol-13-acetate-induced hepatocellular transformation via activator protein 1 signaling pathway and cell cycle progression

Flavonoids are constituents of fruits, vegetables, and plant-derived beverages, as well as components in herbal containing dietary supplements. They exhibit a remarkable spectrum of biochemical and pharmacological activities. In this study, we examined morin (3,5,7,2',4'-pentahydroxyflavone) for its effect on 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated human hepatocytes. Morin inhibited TPA-induced cellular transformation in Chang liver cells in a dose-dependent manner. Luciferase assay and electrophoretic mobility shift assay revealed that morin suppressed TPA-induced AP-1 activity, and the inhibition of AP-1 activity by morin was mediated through the inhibition of p38 kinase. Moreover, morin induced the S-phase arrest and inhibited the DNA synthesis in TPA-treated hepatocytes, suggesting that a cell cycle checkpoint was activated by morin to block DNA synthesis in S phase. In conclusion, our results suggested that morin was a potent anti-hepatocellular transformation agent that inhibited cellular transformation by suppressing the AP-1 activity and inducing the S-phase arrest in human hepatocytes.

Rasagenthi lehyam (RL) a novel complementary and alternative medicine for prostate cancer

PURPOSE

The use of complementary and alternative medicine (CAM) in cancer has been increasing. The therapeutic modalities which originated from India, viz., Ayurveda and Siddha, have phytotherapy as their fundamental basis and, therefore, produce few side effects. They are among the most ancient medicinal systems and are still being practiced in India and elsewhere, to cure cancer and other diseases. Many Siddha practitioners in the southern parts of India prescribe rasagenthi lehyam (RL) as a drug for cancer. RL contains 38 different botanicals, many of which have been shown to possess therapeutic efficacy, and 8 inorganic compounds, all prepared into a paste in a palm sugar and hen's egg base. The efficacy of RL in killing prostate cancer cells in vitro was investigated in this study to determine whether RL could be recommended as a CAM for prostate cancer.

METHODS

In order to scientifically validate the anticancer activity of RL on prostate cancer, a methanolic extract of RL was serially extracted with four organic solvents, and the extracts were tested for clonogenic inhibition and induction of apoptosis in PC-3 prostate cancer cells, with and without irradiation. n-Hexane, ethyl acetate and chloroform extracts of RL effectively killed PC-3 cells.

RESULTS

The IC(50) values of n-hexane, ethyl acetate and chloroform extracts of RL were 3.84 microg/ml, 3.68 microg/ml and 75 ng/ml, respectively. All three extracts induced apoptosis in PC-3 cells. Further, all the three extracts when combined with radiation, caused enhanced effect on killing of PC-3 cells. Among the three extracts, the chloroform extract showed the most significant radiation-sensitizing effect.

CONCLUSION

RL, either in its original formulation prepared under strict quality control or its chloroform extract, could potentially be an alternative medicine for prostate cancer, and also a sensitizing agent in the context of radiation therapy for prostate cancer, as a complementary medicine. A more directed study could lead to the identification of the active principle(s) in the chloroform extract of RL for use in prostate cancer therapy.

Caspase-mediated cell death in hematological malignancies: theoretical considerations, methods of assessment, and clinical implications

Apoptosis, the caspase-mediated cell death, plays an important role in the etiology, pathogenesis and therapy of a variety of diseases. Abnormalities of apoptosis regulation, resulting in either its inhibition or enhancement, play a key role in the development of various malignant hematological disorders. Several routine and new therapeutic strategies in Oncohematology are based on apoptosis modulation. Cytotoxic effects of most antineoplastic drugs are based on induction of apoptosis. The accurate estimate of incidence of apoptosis, therefore, is of importance in Oncohematology. In this review we provide an overview of the methods designed to measure the incidence of apoptosis, including the recently developed assays that are based on detection of caspases activation. We also review recent findings on the role of caspase-mediated cell death in hematological malignancies and discuss their clinical implications, including new therapeutical strategies that evolve from these findings.

PDTC, metal chelating compound, induces G1 phase cell cycle arrest in vascular smooth muscle cells through inducing p21Cip1 expression: Involvement of p38 mitogen activated protein kinase

Pyrrolidine dithiocarbamate (PDTC), a metal chelating compound, is known to induce cell death in vascular smooth muscle cells (VSMC). However, the molecular mechanism for PDTC-induced VSMC death is not well understood. Addition of PDTC reduced cell growth and DNA synthesis on VSMC in low density conditions. However, in serum depleted medium, PDTC did not affect the cell viability, suggesting that certain factors in serum may mediate the cytotoxic effect of PDTC. Several metal chelators prevented the cell death induced by PDTC. In a serum-deprived condition, addition of exogenous metals, copper, iron, and zinc, restored the cytotoxic effect of PDTC. These data indicate that metals such as copper, iron, and zinc in serum may mediate the cytotoxic effect of PDTC. At low VSMC density in 10% FBS, treatment of PDTC, which induced a cell-cycle block in G1-phase, induced down-regulation of cyclins and CDKs and up-regulation of the CDK inhibitor p21 expression, whereas up-regulation of p27 or p53 by PDTC was not observed. Finally, we determined PDTC-mediated signaling pathway involved in VSMC death. Among relevant pathways, PDTC induced marked activation of p38MAPK and JNK. Expression of dominant negative p38MAPK and SB203580, a p38MAPK specific inhibitor, blocked PDTC-dependent p38MAPK, growth inhibition, and p21 expression. These data demonstrate that the p38MAPK pathway participates in p21 induction, which consequently leads to decrease of cyclin D1/cdk4 and cyclin E/cdk2 complexes and PDTC-dependent VSMC growth inhibition. In conclusion, an understanding of the molecular mechanisms of PDTC in VSMC provides a theoretical basis for clinical approaches using antioxidant therapies in atherosclerosis.