Arsenic trioxide induces apoptosis in pancreatic cancer cells via changes in cell cycle, caspase activation, and GADD expression

Iron-Dependent Cell Death: A New Treatment Approach against Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a devastating tumor type where a very high proportion of people diagnosed end up dying from cancer. Surgical resection is an option for only about 20% of patients, where the 5-year survival increase ranges from 10 to 25%. In addition to surgical resection, there are adjuvant chemotherapy schemes, such as FOLFIRINOX (a mix of Irinotecan, oxaliplatin, 5-Fluorouraci and leucovorin) or gemcitabine-based treatment. These last two drugs have been compared in the NAPOLI-3 clinical trial, and the NALIRIFOX arm was found to have a higher overall survival (OS) (11.1 months vs. 9.2 months). Despite these exciting improvements, PDAC still has no effective treatment. An interesting approach would be to drive ferroptosis in PDAC cells. A non-apoptotic reactive oxygen species (ROS)-dependent cell death, ferroptosis was first described by Dixon et al. in 2012. ROS are constantly produced in the tumor cell due to high cell metabolism, which is even higher when exposed to chemotherapy. Tumor cells have detoxifying mechanisms, such as Mn-SOD or the GSH-GPX system. However, when a threshold of ROS is exceeded in the tumor cell, the cell's antioxidant systems are overwhelmed, resulting in lipid peroxidation and, ultimately, ferroptosis. In this review, we point out ferroptosis as an approach to consider in PDAC and propose that altering the cellular ROS balance by combining oxidizing agents or with inhibitors of the main cellular detoxifiers triggers ferroptosis in PDAC.

Genome-wide DNA methylation pattern in whole blood of patients with coal-burning arsenic poisoning

Exposure to coal-burning arsenic leads to an increased risk of cancer, multi-systems damage and chronic diseases, with DNA methylation one potential mechanism of arsenic toxicity. There are few studies on genome-wide methylation in the coal-burning arsenic poisoning population. Illumina 850 K methylation beadchip is the most suitable technology for DNA methylation of epigenome-wide association analysis. This study used 850 K to detect changes in Genome-wide DNA methylation in whole blood samples of 12 patients with coal-burning arsenic poisoning ( Arsenic poisoning group) and four healthy control participants (Healthy control group). There is clearly abnormal genome-wide DNA methylation in coal-burning arsenic poisoning, with 647 significantly different methylation positions, 524 different methylation regions and 335 significantly different methylation genes in arsenic poisoning patients compared with healthy controls. Further functional analysis of Gene ontology (GO) and Kyoto encyclopedia of genes (KEGG) found 592 GO items and 131 KEGG pathways between patients of coal-burning arsenic poisoning and healthy control. Then, analysis of gene degree and combined-score identified NAPRT1, NT5C3B, NEDD4L, SLC22A3 and RAB11B as target genes. Further validation by qRT-PCR indicates that mRNA expression of five genes changes significantly in the arsenic poisoning group (n = 72) compared to the healthy control group (n = 72). These results showed the genome-wide methylation pattern and highlighted five critical genes within the coal-burning arsenic poisoning population that involve Nicotinate and nicotinamide metabolism, Choline metabolism in cancer, and Ubiquitin mediated proteolysis. Next, the methylation profile of coal burning arsenic poisoning will be further excavation and the mechanism of coal burning arsenic poisoning will be further explored from five genes related pathways and functions.

Sodium arsenite and dimethylarsenic acid induces apoptosis in OC3 oral cavity cancer cells

Although arsenic is an environmental toxicant, arsenic trioxide (ATO) is used to treat acute promyelocytic leukemia (APL) with anticancer effects. Studies have demonstrated oral cancer is in the top 10 cancers in Taiwan. High rate of oral cancers is linked to various behaviors, such as excessive alcohol consumption and tobacco use. Similarly, betel chewing is a strong risk factor in oral cancer. In the present study, oral squamous carcinoma OC3 cells were investigated with the treatments of sodium arsenite (NaAsO2) and dimethylarsenic acid (DMA), respectively, to examine if arsenic compounds have anti‑cancer efforts. It was found that 1 µM NaAsO2 and 1 mM DMA for 24 h induced rounded contours with membrane blebbing phenomena in OC3 cells, revealing cell apoptotic characteristics. In addition, NaAsO2 (10‑100 µM) and DMA (1‑100 mM) significantly decreased OC3 cell survival. In cell cycle regulation detected by flow cytometry, NaAsO2 and DMA significantly augmented percentage of subG1 and G2/M phases in OC3 cells, respectively. Annexin V/PI double staining assay was further used to confirm NaAsO2 and DMA did induce OC3 cell apoptosis. In mechanism investigation, western blotting assay was applied and the results showed that NaAsO2 and DMA significantly induced phosphorylation of JNK, ERK1/2 and p38 and then the cleavages of caspase‑8, ‑9, ‑3 and poly ADP‑ribose polymerase (PARP) in OC3 cells, dynamically. In conclusion, NaAsO2 and DMA activated MAPK pathways and then apoptotic pathways to induce OC3 oral cancer cell apoptosis.

Network controllability solutions for computational drug repurposing using genetic algorithms

Control theory has seen recently impactful applications in network science, especially in connections with applications in network medicine. A key topic of research is that of finding minimal external interventions that offer control over the dynamics of a given network, a problem known as network controllability. We propose in this article a new solution for this problem based on genetic algorithms. We tailor our solution for applications in computational drug repurposing, seeking to maximize its use of FDA-approved drug targets in a given disease-specific protein-protein interaction network. We demonstrate our algorithm on several cancer networks and on several random networks with their edges distributed according to the Erdős-Rényi, the Scale-Free, and the Small World properties. Overall, we show that our new algorithm is more efficient in identifying relevant drug targets in a disease network, advancing the computational solutions needed for new therapeutic and drug repurposing approaches.

Arsenic compounds induce apoptosis by activating the MAPK and caspase pathways in FaDu oral squamous carcinoma cells

For a number of years, oral cancer has remained in the top ten most common types of cancer, with an incidence rate that is steadily increasing. In total, ~75% oral cancer cases are associated with lifestyle factors, including uncontrolled alcohol consumption, betel and tobacco chewing, and the excessive use of tobacco. Notably, betel chewing is highly associated with oral cancer in Southeast Asia. Arsenic is a key environmental toxicant; however, arsenic trioxide has been used as a medicine for the treatment of acute promyelocytic leukemia, highlighting its anticancer properties. The present study aimed to investigate the role of arsenic compounds in the treatment of cancer, using FaDu oral squamous carcinoma cells treated with sodium arsenite (NaAsO₂) and dimethyl arsenic acid (DMA). The results demonstrated that FaDu cells exhibited membrane blebbing phenomena and high levels of apoptosis following treatment with 10 µM NaAsO₂ and 1 mM DMA for 24 h. The results of cell viability assay demonstrated that the rate of FaDu cell survival was markedly reduced as the concentration of arsenic compounds increased from 10 to 100 µM NaAsO₂, and 1 to 100 mM DMA. Moreover, flow cytometry was carried out to further examine the effects of arsenic compounds on FaDu cell cycle regulation; the results revealed that treatment with NaAsO₂ and DMA led to a significant increase in the percentage of FaDu cells in the sub‑G1 and G2/M phases of the cell cycle. An Annexin V/PI double staining assay was subsequently performed to verify the levels of FaDu cell apoptosis following treatment with arsenic compounds. Furthermore, the results of the western blot analyses revealed that the expression levels of caspase‑8, ‑9 and ‑3, and poly ADP‑ribose polymerase, as well the levels of phosphorylated JNK and ERK1/2 were increased following treatment with NaAsO₂ and DMA in the FaDu cells. On the whole, the results of the present study revealed that treatment with NaAsO₂ and DMA promoted the apoptosis of FaDu oral cancer cells, by activating MAPK pathways, as well as the extrinsic and intrinsic apoptotic pathways.

Novel Mechanistic Insights into the Anti-cancer Mode of Arsenic Trioxide

Arsenic, a naturally-occurring toxic element, and a traditionally-used drug, has received a great deal of attention worldwide due to its curative anti-cancer properties in patients with acute promyelocytic leukemia. Among the arsenicals, arsenic trioxide has been most widely used as an anti-cancer drug. Recent advances in cancer therapeutics have led to a paradigm shift away from traditional cytotoxic drugs towards the targeting of proteins closely associated with driving the cancer phenotype. Due to the diverse anti-cancer effects of ATO on different types of malignancies, numerous studies have made efforts to uncover the mechanisms of ATO-induced tumor suppression. From in vitro cellular models to studies in clinical settings, ATO has been extensively studied. The outcomes of these studies have opened doors to establishing improved molecular-targeted therapies for cancer treatment. The efficacy of ATO has been augmented by combination with other drugs. In this review, we discuss recent arsenic-based cancer therapies and summarize the novel underlying molecular mechanisms of the anti-cancer effects of ATO.

Therapeutic strategy of arsenic trioxide in the fight against cancers and other diseases

Arsenic trioxide (ATO) has been recognized as a drug for the treatment of various diseases in traditional medicine for more than two thousand years. Although ATO has recently shown excellent efficacy for the treatment of acute promyelocytic leukemia (APL), it could not provide satisfactory outcomes as a single-agent for the management of non-APL leukemia or different solid tumors. Nevertheless, combination treatment strategies, e.g., ATO with other agents, have shown promising results against different diseases. Here, we introduce in depth the latest evidence and detailed insights into ATO-mediated cures for APL by targeting PML/RARα chimeric protein, followed by the preclinical and clinical efficacy of ATO on various non-APL malignancies and solid tumors. Likewise, the antiviral activity of ATO against human immunodeficiency virus (HIV) and hepatitis C virus (HCV) was also discussed briefly. Our review would provide a clear prospect for the combination of ATO with other agents for treatment of numerous neoplastic diseases, and open a new era in the clinically applicable range of arsenicals.

Skp2 Expression Is Inhibited by Arsenic Trioxide through the Upregulation of miRNA-330-5p in Pancreatic Cancer Cells

Arsenic trioxide (ATO) has been found to exert its anti-cancer activity in various human malignancies. In our previous report, we have shown that ATO inhibited cell growth and invasion via downregulation of Skp2 in pancreatic cancer (PC) cells. It has been extensively demonstrated that microRNAs (miRNAs) play a pivotal role in tumorigenesis. ATO might induce PC cell apoptosis and regulate Skp2 downregulation through the regulation of miRNAs. One study has demonstrated that miR-330-5p exerts a tumor-suppressive function in PC cell lines. Here, we investigated the role of miRNA-330-5p in ATO-mediated anti-tumor activity and explored whether ATO could regulate miR-330-5p in PC cells. We found that ATO treatment upregulated the expression of miR-330-5p. Moreover, miR-330-5p inhibitor rescued the ATO-mediated tumor-suppressive function. The combination of miR-330-5p mimic with ATO reduced cell growth, motility, and invasion, and enhanced apoptosis to a greater degree in PC cells. This study suggests that the combination of miR-330-5p mimic with ATO may be a potential therapeutic strategy for the treatment of PC.

The crosstalk between trace elements with DNA damage response, repair, and oxidative stress in cancer

DNA damage response (DDR) is a regulatory system responsible for maintaining genome integrity and stability, which can sense and transduce DNA damage signals. The severity of damage appears to determine DDRs, which can include damage repair, cell-cycle arrest, and apoptosis. Furthermore, defective components in DNA damage and repair machinery are an underlying cause for the development and progression of various types of cancers. Increasing evidence indicates that there is an association between trace elements and DDR/repair mechanisms. In fact, trace elements seem to affect mediators of DDR. Besides, it has been revealed that oxidative stress (OS) and trace elements are associated with cancer development. In this review, we discuss the role of some critical trace elements in the risk of cancer. In addition, we provide a brief introduction on DDR and OS in cancer. Finally, we will further review the interactions between some important trace elements including selenium, zinc, chromium, cadmium, and arsenic, and DDR, and OS in cancer.

Identification of Key Potential Targets and Pathway for Arsenic Trioxide by Systemic Bioinformatics Analysis in Pancreatic Cancer

Arsenic trioxide is an approved chemotheraputic agent for the treatment of acute promyelocytic leukemia (APL). Recently, numerous studies suggested that arsenic trioxide acts as anti-cancer roles in various human malignancies. However, the molecular mechanisms are not fully elucidated. In this study, we explored the critical targets of arsenic trioxide and their interaction network systematically by searching the publicly available published database like DrugBank (DB) and STRING. Seven direct protein targets (DPTs) and 111 DPT-associated genes were identified. The enrichment analysis of arsenic trioxide associated genes/proteins revealed 10 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Among these pathways, phosphatidylinositol-4,5-bisphosphate-3-kinase -Akt (PI3K-Akt) single pathway and pancreatic cancer pathway are highly correlated with arsenic trioxide and have 5 overlapped targets. Then we investigated the gene alternation of selected critical genes in pancreatic cancer studies using cBio portal. These results indicated that arsenic trioxide could act anti-tumor function through PI3K-Akt single pathway and identified critical genes might be therapeutic targets for pancreatic cancer.

Mitochondrial dysfunction, oxidative stress and apoptotic induction in microglial BV-2 cells treated with sodium arsenate

The treatment of microglial BV-2 cells with sodium arsenate (As(V): 0.1-400μmol/L - 48hr) induces a dose-dependent response. The neurotoxic effects of high concentrations of As(V) (100, 200 and 400μmol/L) are characterized by increased levels of mitochondrial complexes I, II, and IV followed by increased superoxide anion generation. Moreover, As(V) triggers an apoptotic mode of cell death, demonstrated by an apoptotic SubG1 peak, associated with an alteration of plasma membrane integrity. There is also a decrease in transmembrane mitochondrial potential and mitochondrial adenosine triphosphate ATP. It is therefore tempting to speculate that As(V) triggers mitochondrial dysfunction, which may lead to defective oxidative phosphorylation subsequently causing mitochondrial oxidative damage, which in turn induces an apoptotic mode of cell death.

Arsenic Trioxide Inhibits Cell Growth and Invasion via Down- Regulation of Skp2 in Pancreatic Cancer Cells

Arsenic trioxide (ATO) has been found to exert anti-cancer activity in various human malignancies. However, the molecular mechanisms by which ATO inhibits tumorigenesis are not fully elucidated. In the current study, we explored the molecular basis of ATO-mediated tumor growth inhibition in pancreatic cancer cells. We used multiple approaches such as MTT assay, wound healing assay, Transwell invasion assay, annexin V-FITC, cell cycle analysis, RT-PCR and Western blotting to achieve our goal. We found that ATO treatment effectively caused cell growth inhibition, suppressed clonogenic potential and induced G2-M cell cycle arrest and apoptosis in pancreatic cancer cells. Moreover, we observed a significant down-regulation of Skp2 after treatment with ATO. Furthermore, we revealed that ATO regulated Skp2 downstream genes such as FOXO1 and p53. These findings demonstrate that inhibition of Skp2 could be a novel strategy for the treatment of pancreatic cancer by ATO.

Integrative nanomedicine: treating cancer with nanoscale natural products

Finding safer and more effective treatments for specific cancers remains a significant challenge for integrative clinicians and researchers worldwide. One emerging strategy is the use of nanostructured forms of drugs, vaccines, traditional animal venoms, herbs, and nutraceutical agents in cancer treatment. The recent discovery of nanoparticles in traditional homeopathic medicines adds another point of convergence between modern nanomedicine and alternative interventional strategies. A way in which homeopathic remedies could initiate anticancer effects includes cell-to-cell signaling actions of both exogenous and endogenous (exosome) nanoparticles. The result can be a cascade of modulatory biological events with antiproliferative and pro-apoptotic effects. The Banerji Protocols reflect a multigenerational clinical system developed by homeopathic physicians in India who have treated thousands of patients with cancer. A number of homeopathic remedy sources from the Banerji Protocols (eg, Calcarea phosphorica; Carcinosin-tumor-derived breast cancer tissue prepared homeopathically) overlap those already under study in nonhomeopathic nanoparticle and nanovesicle tumor exosome cancer vaccine research. Past research on antineoplastic effects of nano forms of botanical extracts such as Phytolacca, Gelsemium, Hydrastis, Thuja, and Ruta as well as on homeopathic remedy potencies made from the same types of source materials suggests other important overlaps. The replicated finding of silica, silicon, and nano-silica release from agitation of liquids in glassware adds a proven nonspecific activator and amplifier of immunological effects. Taken together, the nanoparticulate research data and the Banerji Protocols for homeopathic remedies in cancer suggest a way forward for generating advances in cancer treatment with natural product-derived nanomedicines.

Redirecting apoptosis to aponecrosis induces selective cytotoxicity to pancreatic cancer cells through increased ROS, decline in ATP levels, and VDAC

Pancreatic cancer cell lines with mutated ras underwent an alternative form of cell death (aponecrosis) when treated concomitantly with clinically achievable concentrations of arsenic trioxide, ascorbic acid, and disulfiram (Antabuse; AAA). AAA's major effects are mediated through generation of intracellular reactive oxygen species (ROS) and more than 50% decline in intracellular ATP. N-acetyl cysteine and a superoxide dismutase mimetic prevented aponecrosis and restored intracellular ATP levels. DIDS (4,4'-diisothiocyanatostilbene-2, 2' disulfonic acid), the pan- Voltage-Dependent Anion Channel (VDAC), -1, 2, 3 inhibitor and short hairpin RNA (shRNA) to VDAC-1 blocked cell death and ROS accumulation. In vivo exposure of AAA led to a 62% reduction in mean tumor size and eliminated tumors in 30% of nude mice with PANC-1 xenografts. We concluded that early caspase-independent apoptosis was shifted to VDAC-mediated "targeted" aponecrosis by the addition of disulfiram to arsenic trioxide and ascorbic acid. Conceptually, this work represents a paradigm shift where switching from apoptosis to aponecrosis death pathways, also known as targeted aponecrosis, could be utilized to selectively kill pancreatic cancer cells resistant to apoptosis.

Gadd45 proteins: relevance to aging, longevity and age-related pathologies

The Gadd45 proteins have been intensively studied, in view of their important role in key cellular processes. Indeed, the Gadd45 proteins stand at the crossroad of the cell fates by controlling the balance between cell (DNA) repair, eliminating (apoptosis) or preventing the expansion of potentially dangerous cells (cell cycle arrest, cellular senescence), and maintaining the stem cell pool. However, the biogerontological aspects have not thus far received sufficient attention. Here we analyzed the pathways and modes of action by which Gadd45 members are involved in aging, longevity and age-related diseases. Because of their pleiotropic action, a decreased inducibility of Gadd45 members may have far-reaching consequences including genome instability, accumulation of DNA damage, and disorders in cellular homeostasis - all of which may eventually contribute to the aging process and age-related disorders (promotion of tumorigenesis, immune disorders, insulin resistance and reduced responsiveness to stress). Most recently, the dGadd45 gene has been identified as a longevity regulator in Drosophila. Although further wide-scale research is warranted, it is becoming increasingly clear that Gadd45s are highly relevant to aging, age-related diseases (ARDs) and to the control of life span, suggesting them as potential therapeutic targets in ARDs and pro-longevity interventions.

Arsenic oxide targets stem cell marker CD133/prominin-1 in gallbladder carcinoma

CD133+ tumor cells are responsible for the initiation, propagation and recurrence of tumors, which raises the question of how to effectively target CD133+ tumor cells. Arsenic trioxide (As2O3) has considerable efficacy in treating solid tumors with induction of apoptosis. Here, we found that purified CD133+ gallbladder carcinoma cells are highly resistant to conventional chemotherapy. However, As2O3 effectively induces CD133+ gallbladder carcinoma cells apoptosis. Treatment with As2O3 reduces CD133 expression at transcriptional levels. Furthermore, the ectopic expression of CD133 attenuated the apoptotic effect of As2O3 on cells through activation of AKT signaling pathways. Collectively, As2O3 effectively targets CD133 in gallbladder carcinoma, providing a new mechanism of As2O3-induced cell apoptosis and a better understanding of drug resistance in gallbladder carcinoma.

IKKβ downregulation is critical for triggering JNKs-dependent cell apoptotic response in the human hepatoma cells under arsenite exposure

Arsenite has a long history in treating leukemia, which might be also effective in the therapy of other cancers. Our previous published data have demonstrated that arsenite exposure induces apoptosis in the HepG2 human hepatoma cells via activating JNKs/AP-1 pathway, but the upstream signaling events responsible for JNKs (c-Jun N-terminal kinase) cascade activation have not been fully discovered. Since cross-talk between IKK/NF-κB and JNKs pathways under stress conditions is a hot topic, in this article, we investigate the potential roles of IKKα and IKKβ, the catalytic subunits of IKK complexes, in the arsenite-induced JNKs pathway activation in the HepG2 cells. We found that arsenite exposure induced JNKs and AP-1 activation accompanying with a significant reduction of both IKKα and IKKβ expressions. Overexpression of IKKβ, but not of IKKα, inhibited arsenite-induced MKK7/JNKs/AP-1 pathway activation as well as the apoptotic response. Therefore, we conclude that the downregulation of IKKβ expression is the prerequisite signaling event for mediating JNKs pathway activation and the cellular apoptotic response in the HepG2 cells under arsenite exposure. Targeting IKKβ might be helpful to enhance the tumor therapeutic effect of arsenite.

Arsenic trioxide regulates the apoptosis of glioma cell and glioma stem cell via down-regulation of stem cell marker Sox2

Knowledge of the mechanism by which arsenic trioxide exerts the anti-tumor effects may help in designing a more effective regimen for therapy. Transcription factor Sox2, a key gene implicated in maintaining the "stemness" of embryonic and adult stem cells, plays an important role in the carcinogenesis and maintenance of glioblastoma. Here, we found that the expression of Sox2 at transcriptional level was decreased during As(2)O(3)-induced glioma cell apoptosis. And, the ectopic expression of Sox2 attenuated the apoptotic effect of As(2)O(3) on glioma cell. Furthermore, As(2)O(3) inhibited the self-renewal of glioma stem cells, and efficiently induces the apoptosis of glioma stem cells, at least, partly through down-regulation of Sox2. These data identify a previously unrecognized mechanism of the anti-tumor effects of arsenic trioxide.

Melatonin induces pro-apoptotic signaling pathway in human pancreatic carcinoma cells (PANC-1)

Pancreatic cancer is a highly lethal disease with a poor prognosis for long-term survival rate at all stages of invasiveness. It responds poorly to radio- and chemotherapy because the tumor cells are resistant to apoptosis. Melatonin has been reported to inhibit pancreatic cancer growth in experimental studies in animals but the effect of melatonin on cultured human pancreatic carcinoma cells has not been tested. Moreover, we have recently shown that melatonin stimulates production of two major anti-apoptotic heat shock proteins, HSP27 and HSP 90, in pancreatic carcinoma cells. This study investigated the changes in intrinsic pathway of apoptosis at the mitochondrial level and cascade of caspases in human pancreatic carcinoma cells (PANC-1) cells subjected to melatonin and/or luzindole. Melatonin (10⁻⁸ -10⁻¹² m), the nonselective melatonin receptor antagonist, luzindole (10⁻⁸ -10⁻¹² m) or a combination of both agents were added to PANC-1 cell cultures. Cells were harvested, and the cytoplasmic proteins were isolated after 24 and 48 hr of incubation and analyzed employing co-immunoprecipitation and western blot. Administration of melatonin to the PANC-1 cells resulted in the stimulation of Bcl-2/Bax and caspase-9 proteins levels. The strongest signal of these pro-apoptotic factors was observed at the low concentration (10⁻¹² m) of melatonin. Pretreatment with luzindole alone and prior to the addition of melatonin reversed the stimulatory effect of this indoloamine on Bcl-2/Bax and caspase-9 proteins expression in PANC-1 cells. This is the first study to demonstrate a pro-apoptotic effect of low (physiological) concentration of melatonin on the pancreatic carcinoma cells. In conclusion, melatonin induced pro-apoptotic pathways in human pancreatic carcinoma, probably by interaction with the Mel-1 A/B receptors.

Arsenite stabilizes HIF-1α protein through p85α-mediated up-regulation of inducible Hsp70 protein expression

Hypoxia-inducible factor-1α (HIF-1α) has been reported to regulate over 100 gene expressions in response to hypoxia and other stress conditions. In the present study, we found that arsenite could induce HIF-1α protein accumulation in both mouse epidermal Cl41 cells and mouse embryonic fibroblasts (MEFs). Knockout of p85α, a regulatory subunit of PI-3K, in MEFs (p85α(-/-)) dramatically decreased the arsenite-induced HIF-1α accumulation, indicating that p85α is crucial for arsenite effects on the stabilization of HIF-1α protein. Our further studies suggest that arsenite could induce inducible Hsp70 expression, and transfection of inducible Hsp70 into p85α(-/-) MEFs could restore HIF-1α protein accumulation. Moreover, the results using EMSA and Supershift assays indicate that p85α is crucial for arsenite-induced activation of the heat-shock transcription factor 1 (HSF-1), which is responsible for transcription of inducible Hsp70. Taken together, p85α-mediated HIF-1α stabilization upon arsenite exposure is specifically through HSF-1 activation and subsequent up-regulation of the inducible Hsp70 expression.

Regulation of the human CHOP gene promoter by the stress response transcription factor ATF5 via the AARE1 site in human hepatoma HepG2 cells

AIMS

Activating transcription factor (ATF) 5 is a member of the cAMP response element-binding protein (CREB)/ATF family of transcription factors. We have shown that ATF5 is a stress response transcription factor that responds to amino acid limitation, arsenite exposure, or cadmium exposure. In this study we investigated whether ATF5 is involved in the regulation of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) gene expression.

MAIN METHODS

We used a transient transfection system to express ATF5 and analyzed the regulation of CHOP gene promoter in human hepatoma, HepG2 cells. We also studied the effect of ATF5 knockdown on arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.

KEY FINDINGS

We showed that ATF5 activates the CHOP gene promoter in HepG2 cells. Both deletion analysis and point mutations of the promoter revealed that amino acid response element (AARE) 1 is responsible for ATF5-dependent promoter activation. Furthermore, the existence of either AARE1 or activating protein-1 (AP-1) site is sufficient for transcriptional activation of the CHOP gene promoter by arsenite exposure, although complete induction requires the existence of both elements. We also demonstrated that knockdown of ATF5 reduced arsenite-induced CHOP protein expression and arsenite-induced cell death of HepG2 cells.

SIGNIFICANCE

These results suggested that the CHOP gene is a potential target for ATF5, and that ATF5 raises the arsenite-induced CHOP gene expression level via the AARE1 site in HepG2 cells.

GADD45alpha mediates arsenite-induced cell apoptotic effect in human hepatoma cells via JNKs/AP-1-dependent pathway

Arsenite (As(III)), an effective chemotherapeutic agent for the acute promyelocytic leukemia (APL) and multiple myeloma (MM), might be also a promise for the therapy of other cancers, including the solid tumors. However, the molecular bases of arsenite-induced cytotoxicity in the tumor cells have not been fully defined. In this study, we have disclosed that arsenite effectively induces the apoptotic response in the HepG2 human hepatoma cells by triggering GADD45alpha induction and the subsequent activation of JNKs/AP-1 cell death pathway. However, signaling events relating to GADD45alpha/JNKs/AP-1 pathway activation have not been observed in HL7702 human diploid hepatic cells under the same arsenite exposure condition. Our results thus have illustrated the selective pro-apoptotic role of arsenite in the hepatoma cells by activating GADD45alpha-dependent cell death pathway whereas with little effect on the normal hepatic cells. The approaches to up-regulate GADD45alpha levels might be helpful in improving the chemotherapeutic action of arsenite on certain solid tumors including hepatoma.

Immunotoxicity and biodistribution analysis of arsenic trioxide in C57Bl/6 mice following a 2-week inhalation exposure

In these studies the immunotoxicity of arsenic trioxide (ATO, As(2)O(3)) was evaluated in mice following 14 days of inhalation exposures (nose only, 3 h per day) at concentrations of 50 microg/m(3) and 1 mg/m(3). A biodistribution analysis performed immediately after inhalation exposures revealed highest levels of arsenic in the kidneys, bladder, liver, and lung. Spleen cell levels were comparable to those found in the blood, with the highest concentration of arsenic detected in the spleen being 150 microg/g tissue following the 1 mg/m(3) exposures. No spleen cell cytotoxicity was observed at either of the two exposure levels. There were no changes in spleen cell surface marker expression for B cells, T cells, macrophages, and natural killer (NK) cells. There were also no changes detected in the B cell (LPS-stimulated) and T cell (Con A-stimulated) proliferative responses of spleen cells, and no changes were found in the NK-mediated lysis of Yac-1 target cells. The primary T-dependent antibody response was, however, found to be highly susceptible to ATO suppression. Both the 50 microg/m(3) and 1 mg/m(3) exposures produced greater than 70% suppression of the humoral immune response to sheep red blood cells. Thus, the primary finding of this study is that the T-dependent humoral immune response is extremely sensitive to suppression by ATO and assessment of humoral immune responses should be considered in evaluating the health effects of arsenic containing agents.

Gadd45 proteins as critical signal transducers linking NF-kappaB to MAPK cascades

The growth arrest and DNA damage-inducible 45 (Gadd45) proteins are a group of critical signal transducers that are involved in regulations of many cellular functions. Accumulated data indicate that all three Gadd45 proteins (i.e., Gadd45alpha, Gadd45beta, and Gadd45gamma) play essential roles in connecting an upstream sensor module, the transcription Nuclear Factor-kappaB (NF-kappaB), to a transcriptional regulating module, mitogen-activated protein kinase (MAPK). This NF-kappaB-Gadd45(s)-MAPK pathway responds to various kinds of extracellular stimuli and regulates such cell activities as growth arrest, differentiation, cell survival, and apoptosis. Defects in this pathway can also be related to oncogenesis. In the first part of this review, the functions of Gadd45 proteins, and briefly NF-kappaB and MAPK, are summarized. In the second part, the mechanisms by which Gadd45 proteins are regulated by NF-kappaB, and how they affect MAPK activation, are reviewed.

Arsenic trioxide in patients with adenocarcinoma of the pancreas refractory to gemcitabine: a phase II trial of the University of Chicago Phase II Consortium

OBJECTIVES

There is no effective therapy for patients with metastatic pancreatic cancer who fail initial therapy with gemcitabine. Arsenic trioxide has potent antiproliferative and proapoptotic effects in pancreatic cancer cell lines. We conducted a multicenter phase II trial in patients with advanced pancreatic cancer who experienced disease progression on or after a gemcitabine-containing regimen.

METHODS

Arsenic trioxide 0.3 mg/kg was administered intravenously over 1 hour daily for 5 consecutive days every 28 days. Restaging computed tomography scans were obtained every 2 cycles.

RESULTS

Thirteen patients were enrolled between December 2002 and November 2003. Twenty-four cycles were administered (median 2; range 1-2). There were no grade 3/4 hematologic toxicities; grade 1/2 anemia and leukopenia occurred in 50% and 25% of patients, respectively. Grade 3 toxicities included fatigue and thrombosis in 17% of patients. Only 1 patient developed a prolongation of the QTc interval. There were no objective responses. Median progression-free survival was 1.6 months (95% confidence interval, 1.2-1.9). Median survival was 3.8 months (95% confidence interval, 1.6-6.8).

CONCLUSIONS

Despite promising in vitro data, arsenic trioxide has no activity in pancreatic cancer patients who develop progressive disease after gemcitabine. Multicenter phase II trials are feasible in this patient population, and novel agents are clearly needed.

Arsenic trioxide sensitizes human glioma cells, but not normal astrocytes, to TRAIL-induced apoptosis via CCAAT/enhancer-binding protein homologous protein-dependent DR5 up-regulation

The current study shows that treatment of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant glioma cells with a combination of TRAIL and subtoxic doses of arsenic trioxide (As(2)O(3)) induces rapid apoptosis. Whereas TRAIL-mediated proteolytic processing of procaspase-3 was partially blocked in glioma cells, treatment with As(2)O(3) efficiently recovered TRAIL-induced activation of caspases. We also found that As(2)O(3) treatment of glioma cells significantly up-regulated DR5, a death receptor of TRAIL. Furthermore, suppression of DR5 expression by small interfering RNA (siRNA) inhibited As(2)O(3)/TRAIL-induced apoptosis of U87MG glioma cells, suggesting that DR5 up-regulation is critical for As(2)O(3)-induced sensitization of glioma cells to TRAIL-mediated apoptosis. Our results also indicate that an increase in CCAAT/enhancer binding protein homologous protein (CHOP) protein levels precedes As(2)O(3)-induced DR5 up-regulation. The involvement of CHOP in this process was confirmed by siRNA-mediated CHOP suppression, which not only attenuated As(2)O(3)-induced DR5 up-regulation but also inhibited the As(2)O(3)-stimulated TRAIL-induced apoptosis. These results therefore suggest that the CHOP-mediated DR5 up-regulation, brought about by As(2)O(3), stimulates the TRAIL-mediated signaling pathway. This in turn leads to complete proteolytic processing of caspase-3, which is partially primed by TRAIL in glioma cells. In contrast to human glioma cells, astrocytes were very resistant to the combined administration of As(2)O(3) and TRAIL, demonstrating the safety of this treatment. In addition, As(2)O(3)-mediated up-regulation of CHOP and DR5, as well as partial proteolytic processing of procaspase-3 by TRAIL, was not induced in astrocytes. Taken together, the present results suggest that the combined treatment of glioma cells with As(2)O(3) plus TRAIL may provide an effective and selective therapeutic strategy.

Arsenical-based cancer drugs

Arsenic is a semi-metal or metalloid with two biologically important oxidation states, As(III) and As(V). As(III), in particular, reacts with closely spaced protein thiols, forming stable cyclic dithioarsinite complexes in which both sulfur atoms are bound to arsenic. It is this reaction that is mostly responsible for arsenics cytotoxicity. Arsenic compounds have been used as medicinal agents for many centuries for the treatment of diseases such as psoriasis, syphilis, and rheumatosis. From the 1700's until the introduction of and use of modern chemotherapy and radiation therapy in the mid 1900's, arsenic was a mainstay in the treatment of leukemia. Concerns about the toxicity of arsenical compounds led eventually to their abandonment for the treatment of cancer. The discovery in the 1980's that arsenic trioxide induces complete remission in a high percentage of patients with acute promyelocytic leukemia has awakened interest in this metalloid for the treatment of human disease. In particular, a new class or organoarsenicals are being trialed for the treatment of hematological malignancies and solid tumors. In this review, we discuss the arsenical-based compounds used in the past and present for the treatment of various forms of cancer. Mechanisms of action and selectivity and acute and chronic toxicities are discussed along with the prospects of this class of molecule.

Induction of cyclin D1 by submicromolar concentrations of arsenite in human epidermal keratinocytes

Arsenic is a prevalent environmental carcinogen but arsenic is not directly mutagenic and the mechanism by which arsenite brings about oncogenic transformation is poorly understood. To gain insight into the oncogenic properties of arsenic, we studied the expression of cyclin D1 in cultured human epidermal keratinocytes treated with submicromolar concentrations of sodium arsenite. Arsenite at concentrations between 200 and 800 nM over a 3-day period brought about an increase in cell growth rate. Uptake of the vital stain, neutral red, arsenite at 200 and 400 nM concentrations brought about a parallel increase in cell viability over the same treatment period. Analysis of cell cycle parameters by flow cytometry showed that the growth stimulation was accompanied by a concomitant shift from the G1 into the S/G2 cell cycle compartment in the arsenite-treated cells. Real-time PCR analysis of cyclin D1 transcription showed that there was an induction of more than three-fold in cells exposed to 400 nM arsenite for 3 days. Quantitation of cyclin D levels in Western blots showed that arsenite treatment caused a time-dependent induction of cyclin D proteins representing an induction of about 2.0-fold after a 7 day treatment period. Electrophoretic mobility shift assays (EMSA) showed that arsenite also stimulated binding of the transcription factors, AP1 and CREBP to their respective binding motifs within 3 days. This supports a mechanism of oncogenesis based on persistent upregulation of D type cyclins leading to a concomitant loss of G1/S checkpoint control.

ATM/ATR-related checkpoint signals mediate arsenite-induced G2/M arrest in primary aortic endothelial cells

Epidemiological studies have demonstrated a high association of inorganic arsenic exposure with vascular disease. Our recent in vitro studies have linked this vascular damage to vascular endothelial dysfunction induced by arsenic exposure. However, cell-cycle arrest induced by arsenic and its involvement in vascular dysfunction remain to be clarified. In this study, we employed primary porcine aortic endothelial cells to investigate regulatory mechanisms of G2/M phase arrest induced by arsenite. Our study revealed that lower concentrations of arsenite (1 and 3 microM) increased cell proliferation, whereas higher concentrations of arsenite (10, 20, and 30 microM) inhibited cell proliferation together with correlated increases in G2/M phase arrest. We found that this arsenite-induced G2/M phase arrest was accompanied by accumulation and/or phosphorylation of checkpoint-related molecules, including p53, Cdc25B, Cdc25C, and securin. Inhibition of activations of these checkpoint-related molecules by caffeine significantly attenuated the 30-microM arsenite-induced G2/M phase arrest by 93%. Our data suggest that the DNA damage responsive kinases ATM (ataxia-telangiectasia mutated) and ATR (ATM and Rad3-related) play critical roles in arsenite-induced G2/M phase arrest in aortic endothelial cells possibly via regulation of checkpoint-related signaling molecules including p53, Cdc25B, Cdc25C, and securin.

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

Arsenic trioxide, an acute promyelocytic leukemia chemotherapeutic, may be an efficacious treatment for other cancers. Understanding the mechanism as well as genetic and molecular characteristics associated with sensitivity to arsenite-induced cell death is key to providing effective chemotherapeutic usage of arsenite. Arsenite sensitivity correlates with deficient p53 pathways in multiple cell lines. The role of p53 in preventing arsenite-induced mitotic arrest-associated apoptosis (MAAA), a form of mitotic catastrophe, was examined in TR9-7 cells, a model cell line with p53 exogenously regulated in a tetracycline-off expression system. Arsenite activated G1 and G2 cell cycle checkpoints independently of p53, but mitotic catastrophe occurred preferentially in p53- cells. Cyclin B/CDC2(CDK1) stabilization and caspase-3 activation persisted in arsenite-treated p53- cells consistent with MAAA/mitotic catastrophe. N-Benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, a pan-caspase inhibitor, completely abolished arsenite-induced MAAA/mitotic catastrophe and greatly increased the mitotic index. WEE1 and p21CIP1/WAF1 inhibit cyclin B/CDC2 by CDC2 tyrosine-15 phosphorylation and direct binding, respectively. CDC2-Y15-P was transiently elevated in arsenite-treated p53+ cells but persisted in p53- cells. Arsenite induced p53-S15-P and p21CIP1/WAF1 only in p53+ cells. P21CIP1/WAF1-siRNA-treated p53+ cells were similar to p53- cells in mitotic index and cell cycle protein levels. p53-inducible proteins GADD45alpha and 14-3-3sigma are capable of inhibiting cyclin B/CDC2 but did not play a p53-dependent role in mitotic escape in TR9-7 cells. The data indicate that p53 mediates cyclin B/CDC2 inactivation and mitotic release directly via p21CIP1/WAF1 induction.

Tetraarsenic oxide-mediated apoptosis in a cervical cancer cell line, SiHa

PURPOSE

Diarsenic oxide, As(2)O(3), has been reported to be effective in treating acute leukemia, and induce apoptosis in many tumor cells. In this study, the ability of a novel arsenical compound, As(4)O(6) (tetraarsenic oxide), along with As(2)O(3), for its ability to induce cell growth inhibition, as well as apoptosis, in human cervical cancer cells, SiHa cells, were evaluated in vitro.

MATERIALS AND METHODS

To examine the levels of apoptosis, SiHa cells were given two sensitive doses, 0.5 and 1 microM, of arsenical compounds, and a DNA fragmentation assay and FACS analysis were then conducted. In addition, a Western blotting assay was performed to identify target molecules for apoptosis.

RESULTS

Both As(2)O(3) and As(4)O(6) induced dosedependent inhibition of SiHa cell proliferation. In particular, As(4)O(6) was more effective at suppressing SiHa cell growth than As(2)O(3). In parallel with the inhibition of cell proliferation, As(4)O(6) caused a significantly greater increase in the sub-G1 cell population than As(2)O(3), as determined by propidium iodide DNA staining. This was confirmed by a DNA fragmentation assay and annexin V staining. The Western blotting analysis also showed that the expression of proliferating cell nuclear antigen (PCNA) was suppressed to a significantly greater extent by As(4)O(6) than As(2)O(3) at a dose of 0.5 microM. However, the apoptosis-related protein, Bax, was expressed to a significantly greater extent due to As(4)O(6) than As(2)O(3).

CONCLUSION

Taken together, these findings suggest that a novel arsenic compound, As(4)O(6), possesses more potent anti-proliferative effects on human cervical cancer cells, with the induction of apoptosis also, at least via the activation of Bax protein in vitro.

Cell cycle inhibition by sodium arsenite in primary embryonic rat midbrain neuroepithelial cells

Arsenite (As3+) exposure during development has been associated with neural tube defects and other structural malformations, and with behavioral alterations including altered locomotor activity and operant learning. The molecular mechanisms underlying these effects are uncertain. Because arsenic can cross the placenta and accumulate in the developing neuroepithelium, we examined cell cycling effects of sodium arsenite (As3+ 0, 0.5, 1, 2, and 4 microM) on embryonic primary rat midbrain (gestational day [GD] 12) neuroepithelial cells over 48 h. There was a concentration- and time-dependent As3+-induced reduction in cell viability assessed by neutral red dye uptake assay but minimal apoptosis at concentrations below 4 microM. Morphologically, apoptosis was not apparent until 4 microM at 24 h, which was demonstrated by a marginal but statistically significant increase in cleaved caspase-3/7 activity. Cell cycling effects over several rounds of replication were determined by continuous 5-bromo-2'-deoxyuridine (BrdU) labeling and bivariate flow cytometric Hoechst-Propidium Iodide analysis. We observed a time- and concentration-dependent inhibition of cell cycle progression as early as 12 h after exposure (> or =0.5 microM). In addition, data demonstrated a concentration-dependent increase in cytostasis within all cell cycle phases, a decreased proportion of cells able to reach the second cell cycle, and a reduced cell cycle entry from gap 1 phase (G1). The proportion of affected cells and the severity of the cell cycle perturbation, which ranged from a decreased transition probability to complete cytostasis in all cell cycle phases, were also found to be concentration-dependent. Together, these data support a role for perturbed cell cycle progression in As3+ mediated neurodevelopmental toxicity.

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.

Cell cycle arrest and apoptotic cell death in cultured human gastric carcinoma cells mediated by arsenic trioxide

AIM: To investigate the effect of arsenic trioxide on human gastric cancer cell line MKN45 with respect to both cytotoxicity and induction of apoptosis in vitro.

METHODS: MKN45 cells were treated with arsenic trioxide (As₂O₃) at the concentration of 1, 5, and 10 µmol/L, respectively, for three successive days. Cell growth and proliferation were observed by cell counting and trypan blue exclusion. Cytotoxicity of As₂O₃ was determined by MTT assay. Morphologic changes were studied with light microscopy. Flow cytometry was used to assay cell DNA distribution and apoptotic cells were confirmed with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and DNA electrophoresis.

RESULTS: The growth of MKN45 cells was significantly inhibited by As₂O₃ which was confirmed by colony-forming assay. After 7 d of culture with various concentrations of As₂O₃, colony-forming capacity of MKN45 cells decreased with As₂O₃ increment in comparison with that of control group. The inhibitory rate of colony-formation was 38.5%, 99.1%, and 99.5% when the concentration of As₂O₃ was 1, 5, and 10 μmol/L in culture medium, respectively. The cell number of a single colony in drug treatment groups was less than that of control group. The cell-killing rate of As₂O₃ to MKN45 cells was both dose- and time-dependent with an IC₅₀ of (11.05±0.25) µmol/L. After incubation in 10 μmol/L As₂O₃ for 24 h, the cell-killing rate was 27.1%, and it was close to 50% after 48 h. The results showed that As₂O₃ induced time- and dose-dependent apoptosis in MKN45 cells, blocked at G2/M phase. The apoptotic peak (sub-G1 phase) appeared and cell apoptotic rate in MKN45 cells was 18.3-32.5% after treatment by 10 μmol/L As₂O₃ for 48 h. The percentage of G2/M cell of the experimental groups was 2.0-5.0 times than that of the control group. Gel electrophoresis of DNA from cells treated with each concentration of As₂O₃ for 48 h revealed a “ladder” pattern, indicating preferential DNA degradation at the internucleosomal, linker DNA sections. TUNEL also demonstrated strand breaks in DNA of MKN45 cells treated with As₂O₃, while control cells showed negative labeling.

CONCLUSION: As₂O₃ can induce apoptosis of human gastric carcinoma cells MKN45, which is the basis of its effectiveness. It shows great potential in the treatment of gastric carcinoma.

Preferential action of arsenic trioxide in solid-tumor microenvironment enhances radiation therapy

PURPOSE

To investigate the effect of arsenic trioxide, Trisenox (TNX), on primary cultures of endothelial cells and tumor tissue under varying pH and pO(2) environments and the effects of combined TNX and radiation therapy on experimental tumors.

METHODS AND MATERIALS

Human dermal microvascular endothelial cells were cultured in vitro and exposed to TNX under various combinations of aerobic, hypoxic, neutral, or acidic conditions, and levels of activated JNK MAP kinase were assessed by Western blotting. FSaII fibrosarcoma cells grown in the hind limb of female C3H mice were used to study the effect of TNX on tumor blood perfusion and oxygenation. The tumor-growth delay after a single or fractionated irradiation with or without TNX treatment was assessed.

RESULTS

A single intraperitoneal injection of 8 mg/kg TNX reduced the blood perfusion in FSaII tumors by 53% at 2 hours after injection. To increase the oxygenation of the tumor vasculature during TNX treatment, some animals were allowed to breathe carbogen (95% O(2)/5% CO(2)). Carbogen breathing alone for 2 hours reduced tumor perfusion by 33%. When carbogen breathing was begun immediately after TNX injection, no further reduction occurred in tumor blood perfusion at 2 hours after injection. In vitro, TNX exposure increased activity JNK MAP kinase preferentially in endothelial cells cultured in an acidic or hypoxic environment. In vivo, the median oxygenation in FSaII tumors measured at 3 or 5 days after TNX injection was found to be significantly elevated compared with control tumors. Subsequently, radiation-induced tumor-growth delay was synergistically increased when radiation and TNX injection were fractionated at 3-day or 5-day intervals.

CONCLUSIONS

Trisenox has novel vascular-damaging properties, preferentially against endothelium in regions of low pH or pO(2), which leads to tumor cell death and enhancement of the response of tumors to radiotherapy.

Induction of reactive oxygen species renders mutant and wild-type K-ras pancreatic carcinoma cells susceptible to Ad.mda-7-induced apoptosis

Pancreatic cancer is exceptionally aggressive with no long-term effective therapy. Current interventional approaches, including surgery, radiation and/or chemotherapy, have done little to quell the mortality associated with this malignancy. Subtraction hybridization identified a cancer-specific apoptosis-inducing cytokine gene, melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), with a broad range of selective antitumor activity in diverse cancers both in vitro and in vivo in nude mice and recently in patients with advanced carcinomas and melanomas. Unlike most neoplasms, pancreatic cancers display innate resistance to mda-7/IL-24-induced apoptosis, which correlates with a diminished capacity to convert mda-7/IL-24 mRNA into protein. We presently demonstrate that this translational block can be reversed by treatment with agents that elevate reactive oxygen species (ROS). Induction of apoptosis in vitro and suppression of tumorigenesis in vivo in nude mice are induced in pancreatic cancers, irrespective of the status of their K-ras gene, only when tumor cells simultaneously express mda-7/IL-24 and are treated with a ROS-inducer, such as arsenic trioxide (ARS), N-(4-hydroxyphenyl) retinamide (HPR) or dithiophene (NSC656240 (NSC)). In pancreatic cancer cells constitutively expressing mda-7/IL-24 mRNA, a single treatment with arsenic trioxide, HPR or NSC656240 induces apoptosis, which correlates with production of MDA-7/IL-24 protein. The specificity of this action is documented by the ability of ROS inhibitors, including N-acetyl-L-cysteine and Tiron, to block this killing effect. Of potential clinical significance, similar treatment of normal cells does not elicit significant changes in growth nor does it induce apoptosis. Analysis of signal transduction changes in pancreatic carcinoma cells infected with Ad.mda-7 in combination with a ROS-inducer indicate that cell death correlates with modulation of discrete cassettes of multiple signaling pathways in a pancreatic cancer cell-specific manner, supporting global signaling dysregulation as a potential mediator of apoptosis induction. These findings suggest a promising combinatorial approach for safely promoting cell death in pancreatic tumors that provides a rational framework for developing a selective and effective therapy for this invariably fatal cancer.

NAD+/NADH and/or CoQ/CoQH2 ratios from plasma membrane electron transport may determine ceramide and sphingosine-1-phosphate levels accompanying G1 arrest and apoptosis

To elucidate possible biochemical links between growth arrest from antiproliferative chemotherapeutic agents and apoptosis, our work has focused on agents (EGCg, capsaicin, cis platinum, adriamycin, anti-tumor sulfonylureas, phenoxodiol) that target tNOX. tNOX is a cancer-specific cell surface NADH oxidase (ECTO-NOX protein), that functions in cancer cells as the terminal oxidase for plasma membrane electron transport. When tNOX is active, coenzyme Q(10) (ubiquinone) of the plasma membrane is oxidized and NADH is oxidized at the cytosolic surface of the plasma membrane. However, when tNOX is inhibited and plasma membrane electron transport is diminished, both reduced coenzyme Q(10) (ubiquinol) and NADH would be expected to accumulate. To relate inhibition of plasma membrane redox to increased ceramide levels and arrest of cell proliferation in G(1) and apoptosis, we show that neutral sphingomyelinase, a major contributor to plasma membrane ceramide, is inhibited by reduced glutathione and ubiquinone. Ubiquinol is without effect or stimulates. In contrast, sphingosine kinase, which generates anti-apoptotic sphingosine-1-phosphate, is stimulated by ubiquinone but inhibited by ubiquinol and NADH. Thus, the quinone and pyridine nucleotide products of plasma membrane redox, ubiquinone and ubiquinol, as well as NAD(+) and NADH, may directly modulate in a reciprocal manner two key plasma membrane enzymes, sphingomyelinase and sphingosine kinase, potentially leading to G(1) arrest (increase in ceramide) and apoptosis (loss of sphingosine-1-phosphate). As such, the findings provide potential links between coenzyme Q(10)-mediated plasma membrane electron transport and the anticancer action of several clinically-relevant anticancer agents.

The induction of cell cycle regulatory and DNA repair proteins in cisplatin-induced acute renal failure

The purpose of this study was to evaluate the expressions and the roles of proteins involved in cell cycle regulation and DNA repair in cis-diamminedichloroplatinum (II) (cisplatin or CDDP)-induced acute renal failure (ARF). Treatment with CDDP (6 mg/kg, iv) induced tubular damage and increased serum creatinine (Scr) and the number of TUNEL-positive cells in the outer stripe of the outer medulla in rats, which reached peak levels at 5 days after CDDP. The expressions of cyclin-dependent kinase inhibitors (p21 and p27), cyclin B1, cyclin D1, PCNA, GADD 45, and GADD 153 were significantly increased in the outer medulla, reaching peak levels at 3 days after CDDP. Increments of p27 and PCNA were observed in the same nuclei. Sodium arsenite (SA), a heavy metal, attenuated tubular damage and increased Scr- and TUNEL-positive cells at 5 days after CDDP. SA augmented CDDP-induced increment of p27 but suppressed the increased expression of cyclin B1 and cyclin D1 at 3 days after CDDP. SA-induced attenuation of nephrotoxicity was associated with enhanced expression of proliferating cell nuclear antigen (PCNA) and growth-arrest and DNA damage (GADD) 153 in damaged tubular cells. Our findings indicated that (1) proteins related to cell cycle regulation and DNA repair are induced in CDDP nephrotoxicity, (2) the SA-induced attenuation of CDDP nephrotoxicity is associated with increased expression of p27 and decreased expression of cyclin B1 and cyclin D1, they all induce cell cycle arrest at G1/S and G2/M, and (3) enhanced expression of DNA repair-related proteins is also associated with attenuation of CDDP-nephrotoxicity.

Molecular mechanism of arsenic trioxide inducing apoptosis in human large intestinal carcinoma cell line

AIM: To study the possible apoptosis-inducing effect of arsenic trioxide (As₂O₃) on the different types of human large intestinal carcinoma cell, and its molecular mechanisms.

METHODS: As₂O₃'s action on the cell growth, apoptosis, periodic return and the expression of related genes of the two human large intestinal carcinoma cell lines LoVo and CoLo-320 in vitro was observed by MTT assay, acridine orange (AO)/ethidiumbromide (EB) flurescent staining, electron microscopy detection, DNA gel electrophoresis, flow cytometry, and immunohistochemical staining.

RESULTS: After treated by As₂O₃ at different concentration(0.5, 1.0, 2.0, 4.0 mg/L) for various times (24, 48, 72 h), the human large intestinal carcinoma cell LoVo and CoLo-320 showed strongly inhibitory effect on growth (P < 0.05) and also the cells showed typical morphological and biochemical characteristic changes of apoptosis, with bcl-2 gene expression down-regulated, and bax and Fas gene expression up-regulated (P < 0.01).

CONCLUSION: As₂O₃ has significant apoptosis-inducing effect on large intestinal carcinoma cells, which is regulated by several genes.