Arsenic trioxide induces different gene expression profiles of genes related to growth and apoptosis in glioma cells dependent on the p53 status

Inheritance of paternal lifestyles and exposures through sperm DNA methylation

Many different lifestyle factors and chemicals present in the environment are a threat to the reproductive tracts of humans. The potential for parental preconception exposure to alter gametes and for these alterations to be passed on to offspring and negatively affect embryo growth and development is of concern. The connection between maternal exposures and offspring health is a frequent focus in epidemiological studies, but paternal preconception exposures are much less frequently considered and are also very important determinants of offspring health. Several environmental and lifestyle factors in men have been found to alter sperm epigenetics, which can regulate gene expression during early embryonic development. Epigenetic information is thought to be a mechanism that evolved for organisms to pass on information about their lived experiences to offspring. DNA methylation is a well-studied epigenetic regulator that is sensitive to environmental exposures in somatic cells and sperm. The continuous production of sperm from spermatogonial stem cells throughout a man's adult life and the presence of spermatogonial stem cells outside of the blood-testis barrier makes them susceptible to environmental insults. Furthermore, altered sperm DNA methylation patterns can be maintained throughout development and ultimately result in impairments, which could predispose offspring to disease. Innovations in human stem cell-based spermatogenic models can be used to elucidate the paternal origins of health and disease.

Phase I/II trial of local interstitial chemotherapy with arsenic trioxide in patients with newly diagnosed glioma

Background

Glioma is the most common primary brain tumor in adults with poor prognosis. The glioma patients benefit from STUPP strategy, including maximum and safe resection and adjuvant radiotherapy and chemotherapy. Arsenic trioxide could inhibit various tumors. However, it is a challenge to evaluate the efficiency and safety of srsenic trioxide in glioma patients.

Objective

The arsenic trioxide has the potent therapeutic effect on glioma. However, the safety and efficacy of local interstitial chemotherapy with arsenic trioxide in newly diagnosed glioma patients is unclear.

Methods

All patients received partial or complete tumor resection and intraoperative implantation of Ommaya reservoirs followed by standard radiotherapy. Arsenic trioxide with the starting dose 0.3 mg was administered via an Ommaya reservoir catheter inserted into the tumor cavity for 5 consecutive days every 3 months for a total of eight cycles unless tumor progression or excessive toxicity was observed.

Results

No hematological or grade 4 non-hematological toxicity was observed in any patient during arsenic trioxide treatment. The maximum tolerated dose of 1.5 mg of arsenic trioxide was safe and well tolerated. The median overall survival for WHO grade 3 glioma was 33.6 months, and for glioblastoma was 13.9 months. The median progression-free survival for WHO grade 2 glioma was 40.3 months, for grade 3 glioma was 21.5 months, and for glioblastoma was 9.5 months.

Conclusion

These results suggest that arsenic trioxide is safe and well tolerated with local delivery into the tumor cavity of the brain, and the dose recommended for a phase II trial is 1.5 mg.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Deciphering the Key Pharmacological Pathways and Targets of Yisui Qinghuang Powder That Acts on Myelodysplastic Syndromes Using a Network Pharmacology-Based Strategy

Background

Yisui Qinghuang powder (YSQHP) is an effective traditional Chinese medicinal formulation used for the treatment of myelodysplastic syndromes (MDS). However, its pharmacological mechanism of action is unclear.

Materials and Methods

In this study, the active compounds of YSQHP were screened using the traditional Chinese medicine systems pharmacology (TCMSP) and HerDing databases, and the putative target genes of YSQHP were predicted using the STITCH and DrugBank databases. Then, we further screened the correlative biotargets of YSQHP and MDS. Finally, the compound-target-disease (C-T-D) network was conducted using Cytoscape, while GO and KEGG analyses were conducted using R software. Furthermore, DDI-CPI, a web molecular docking analysis tool, was used to verify potential targets and pathways. Finally, binding site analysis was performed to identify core targets using MOE software.

Results

Our results identified 19 active compounds and 273 putative target genes of YSQHP. The findings of the C-T-D network revealed that Rb1, CASP3, BCL2, and MAPK3 showed the most number of interactions, whereas indirubin, tryptanthrin, G-Rg1, G-Rb1, and G-Rh2 showed the most number of potential targets. The GO analysis showed that 17 proteins were related with STPK activity, PUP ligase binding, and kinase regulator activity. The KEGG analysis showed that PI3K/AKT, apoptosis, and the p53 pathways were the main pathways involved. DDI-CPI identified the top 25 proteins related with PI3K/AKT, apoptosis, and the p53 pathways. CASP8, GSK3B, PRKCA, and VEGFR2 were identified as the correlative biotargets of DDI-CPI and PPI, and their binding sites were found to be indirubin, G-Rh2, and G-Rf.

Conclusion

Taken together, our results revealed that YSQHP likely exerts its antitumor effects by binding to CASP8, GSK3B, PRKCA, and VEGFR2 and by regulating the apoptosis, p53, and PI3K/AKT pathways.

Arsenic trioxide as a novel anti-glioma drug: a review

Arsenic trioxide has shown a strong anti-tumor effect with little toxicity when used in the treatment of acute promyelocytic leukemia (APL). An effect on glioma has also been shown. Its mechanisms include regulation of apoptosis and autophagy; promotion of the intracellular production of reactive oxygen species, causing oxidative damage; and inhibition of tumor stem cells. However, glioma cells and tissues from other sources show different responses to arsenic trioxide. Researchers are working to enhance its efficacy in anti-glioma treatments and reducing any adverse reactions. Here, we review recent research on the efficacy and mechanisms of action of arsenic trioxide in the treatment of gliomas to provide guidance for future studies.

Oncogenomic disruptions in arsenic-induced carcinogenesis

Chronic exposure to arsenic affects more than 200 million people worldwide, and has been associated with many adverse health effects, including cancer in several organs. There is accumulating evidence that arsenic biotransformation, a step in the elimination of arsenic from the human body, can induce changes at a genetic and epigenetic level, leading to carcinogenesis. At the genetic level, arsenic interferes with key cellular processes such as DNA damage-repair and chromosomal structure, leading to genomic instability. At the epigenetic level, arsenic places a high demand on the cellular methyl pool, leading to global hypomethylation and hypermethylation of specific gene promoters. These arsenic-associated DNA alterations result in the deregulation of both oncogenic and tumour-suppressive genes. Furthermore, recent reports have implicated aberrant expression of non-coding RNAs and the consequential disruption of signaling pathways in the context of arsenic-induced carcinogenesis. This article provides an overview of the oncogenomic anomalies associated with arsenic exposure and conveys the importance of non-coding RNAs in the arsenic-induced carcinogenic process.

Multifactorial Modes of Action of Arsenic Trioxide in Cancer Cells as Analyzed by Classical and Network Pharmacology

Arsenic trioxide is a traditional remedy in Chinese Medicine since ages. Nowadays, it is clinically used to treat acute promyelocytic leukemia (APL) by targeting PML/RARA. However, the drug's activity is broader and the mechanisms of action in other tumor types remain unclear. In this study, we investigated molecular modes of action by classical and network pharmacological approaches. CEM/ADR5000 resistance leukemic cells were similar sensitive to As2O3 as their wild-type counterpart CCRF-CEM (resistance ratio: 1.88). Drug-resistant U87.MG ΔEGFR glioblastoma cells harboring mutated epidermal growth factor receptor were even more sensitive (collateral sensitive) than wild-type U87.MG cells (resistance ratio: 0.33). HCT-116 colon carcinoma p53-/- knockout cells were 7.16-fold resistant toward As2O3 compared to wild-type cells. Forty genes determining cellular responsiveness to As2O3 were identified by microarray and COMPARE analyses in 58 cell lines of the NCI panel. Hierarchical cluster analysis-based heat mapping revealed significant differences between As2O3 sensitive cell lines and resistant cell lines with p-value: 1.86 × 10-5. The genes were subjected to Galaxy Cistrome gene promoter transcription factor analysis to predict the binding of transcription factors. We have exemplarily chosen NF-kB and AP-1, and indeed As2O3 dose-dependently inhibited the promoter activity of these two transcription factors in reporter cell lines. Furthermore, the genes identified here and those published in the literature were assembled and subjected to Ingenuity Pathway Analysis for comprehensive network pharmacological approaches that included all known factors of resistance of tumor cells to As2O3. In addition to pathways related to the anticancer effects of As2O3, several neurological pathways were identified. As arsenic is well-known to exert neurotoxicity, these pathways might account for neurological side effects. In conclusion, the activity of As2O3 is not restricted to acute promyelocytic leukemia. In addition to PML/RARA, numerous other genes belonging to diverse functional classes may also contribute to its cytotoxicity. Network pharmacology is suited to unravel the multifactorial modes of action of As2O3.

Arsenic-induced S phase cell cycle lengthening is associated with ROS generation, p53 signaling and CDC25A expression

Cellular response to arsenic is strongly dependent on p53 functional status. Primarily arresting the cell cycle in G1 or G2/M phases, arsenic treatment also induces an increase in the S-phase time in wild-type p53 cells. In contrast, cells with a non-functional p53 display only a subtle increase in the S phase, indicating arsenic differentially affects the cell cycle depending on p53 status. Importantly, it has been reported that arsenic induces reactive oxygen species (ROS), a process counteracted by p53. To evaluate the participation of p53 in the lengthening of the S phase and the connection between the transient cell cycle arrest and oxidative stress, we evaluated the cell response to arsenic in MCF-7 and H1299 cells, and analyzed p53's role as a transcription factor in regulating genes involved in ROS reduction and S phase transition. Herein, we discovered that arsenic induced an increase in the population of S phase cells that was dependent on the presence and transcriptional activity of p53. Furthermore, for the first time, we demonstrate that arsenic activates p53-dependent transcription of ROS detoxification genes, such as SESN1, and by an indirect mechanism involving ATF3, genes that could be responsible for the S phase cell cycle arrest, such as CDC25A.

ANXA1 silencing increases the sensitivity of cancer cells to low-concentration arsenic trioxide treatment by inhibiting ERK MAPK activation

AIMS AND BACKGROUND

Arsenic trioxide (ATO), an antitumor agent, is widely used for treating acute promyelocytic leukemia (APL), in which it induces apoptosis. In most solid tumors, ATO disturbs the cell cycle instead of inducing apoptosis. We aimed to determine the exact mechanism underlying the different response of APL to ATO compared with the response of solid tumors.

METHODS

A proteomics-based screening was used to identify the ATO-associated proteins in the human esophageal squamous cell carcinoma cell line, Eca109. The expression levels of Annexin A1 (ANXA1) in 4 different types of cancer cells were determined by quantitative reverse transcription polymerase chain reaction and Western blotting. Human esophageal squamous cell carcinoma cell line Eca109 and pancreatic carcinoma cell line BxPC3 cells were transfected with siRNAs targeting ANXA1 and scrambled control siRNA. Cell proliferation was evaluated by methyl thiazolyl tetrazolium assay.

RESULTS

After verification of the mRNA and protein levels in 4 cancer cell lines, ANXA1 and lamin A/B were validated to have increased expression levels after low-concentration ATO treatment. Lower concentrations of ATO, which has no effect on proliferation of cancer cells, induced apoptosis after ANXA1 silencing. Furthermore, overexpression of ANXA1 induced by ATO resulted in activation of extracellular signal-regulated kinase (ERK) mitogen-activated protein kinases (MAPKs), rendering cancer cells resistant to the agent. In addition, PD98059, a specific ERK inhibitor, increased the sensitivity of cancer cells to a lower concentration of ATO treatment.

CONCLUSIONS

Taken together, these data indicate that overexpression of ANXA1 induced by low-concentration ATO makes cancer cells more resistant to the agent via activated ERK MAPKs. Specific silencing of ANXA1 increased the sensitivity of cancer cells to ATO treatment.

Arsenic sulfide, the main component of realgar, a traditional Chinese medicine, induces apoptosis of gastric cancer cells in vitro and in vivo

Background

Arsenic sulfide (As₄S₄), the main component of realgar, a traditional Chinese medicine, has shown antitumor efficacy in several tumor types, especially for acute promyelocytic leukemia. In this study, we aimed to explore the efficacy and mechanism of As₄S₄ in gastric cancer.

Methods

The effect of As₄S₄ on cell proliferation and apoptosis of gastric cancer cells was investigated by MTT assay, 4′,6-diamidino-2-phenylindole (DAPI) staining, and annexin V–fluorescein isothiocyanate/propidium iodide staining using gastric cancer cell lines AGS (harboring wild-type p53) and MGC803 (harboring mutant p53) in vitro. The expression of apoptosis-related proteins was measured by Western blotting, real-time polymerase chain reaction, and immunohistochemistry analysis. Mouse xenograft models were established by inoculation with MGC803 cells, and the morphology and the proportion of apoptotic cells in tumor tissues were detected by hematoxylin and eosin staining and TdT-mediated dUTP nick end labeling (TUNEL) assay, respectively.

Results

As₄S₄ inhibited the proliferation and induced apoptosis of AGS and MGC803 cells in a time- and dose-dependent manner. As₄S₄ upregulated the expression of Bax and MDM2 while downregulated the expression of Bcl-2. The expression of p53 increased significantly in the AGS cells but did not readily increase in the MGC803 cells, which harbored mutant p53. Pifithrin-α, a p53 inhibitor, blocked the modulation of As₄S₄ on AGS cells, but not on MGC803 cells. Using xenograft as a model, we showed that As₄S₄ suppressed tumor growth and induced apoptosis in vivo and that the expression of p53 increased accordingly.

Conclusion

As₄S₄ is a potent cytotoxic agent for gastric cancer cells, as it induced apoptosis both in vitro and in vivo through a p53-dependent pathway. Our data indicate that As₄S₄ may have therapeutic potential in gastric cancer.

Imprinted genes and the environment: links to the toxic metals arsenic, cadmium, lead and mercury

Imprinted genes defy rules of Mendelian genetics with their expression tied to the parent from whom each allele was inherited. They are known to play a role in various diseases/disorders including fetal growth disruption, lower birth weight, obesity, and cancer. There is increasing interest in understanding their influence on environmentally-induced disease. The environment can be thought of broadly as including chemicals present in air, water and soil, as well as food. According to the Agency for Toxic Substances and Disease Registry (ATSDR), some of the highest ranking environmental chemicals of concern include metals/metalloids such as arsenic, cadmium, lead and mercury. The complex relationships between toxic metal exposure, imprinted gene regulation/expression and health outcomes are understudied. Herein we examine trends in imprinted gene biology, including an assessment of the imprinted genes and their known functional roles in the cell, particularly as they relate to toxic metals exposure and disease. The data highlight that many of the imprinted genes have known associations to developmental diseases and are enriched for their role in the TP53 and AhR pathways. Assessment of the promoter regions of the imprinted genes resulted in the identification of an enrichment of binding sites for two transcription factor families, namely the zinc finger family II and PLAG transcription factors. Taken together these data contribute insight into the complex relationships between toxic metals in the environment and imprinted gene biology.

Inactivation of Akt by arsenic trioxide induces cell death via mitochondrial-mediated apoptotic signaling in SGC-7901 human gastric cancer cells

Arsenic trioxide (As2O3) has been recognized as a potential chemotherapeutic agent, yet the details concerning its mechanism of action in solid cancers remain undetermined. The present study assessed the role of Akt in the cell death induced by As2O3. The MTT assay showed that As2O3 suppressed the proliferation of SGC-7901 cells in a dose- and time-dependent manner. Characteristic apoptotic changes were observed in the As2O3‑treated cells by Hoechst 33342 staining, and FACS analysis showed that As2O3 caused dose-dependent apoptotic cell death. As2O3 activated caspase-3 and -9, and PARP cleavage in a dose-dependent manner. Compromised mitochondrial membrane potential and an increased protein level of Bax indicated involvement of mitochondia. As2O3 decreased the levels of p-Akt (Ser473), p-Akt (Thr308) and p-GSK-3β (Ser9), suggesting that As2O3 inactivated Akt kinase. In addition, LY294002 (a PI3 kinase inhibitor) augmented the apoptosis induced by As2O3. These results demonstrated that inhibition of PI3K/Akt signaling was involved in As2O3-induced apoptosis of gastric cancer SGC-7901 cells.

The impact of arsenic trioxide and all-trans retinoic acid on p53 R273H-codon mutant glioblastoma

Glioblastoma (GBM) is the most common primary brain tumor in adults and demonstrates a 1-year median survival time. Codon-specific hotspot mutations of p53 result in constitutively active mutant p53, which promotes aberrant proliferation, anti-apoptosis, and cell cycle checkpoint failure in GBM. Recently identified CD133(+) cancer stem cell populations (CSC) within GBM also confer therapeutic resistance. We studied targeted therapy in a codon-specific p53 mutant (R273H) created by site-directed mutagenesis in U87MG. The effects of arsenic trioxide (ATO, 1 μM) and all-trans retinoic acid (ATRA, 10 μM), possible targeted treatments of CSCs, were investigated in U87MG neurospheres. The results showed that U87-p53(R273H) cells generated more rapid neurosphere growth than U87-p53(wt) but inhibition of neurosphere proliferation was seen with both ATO and ATRA. U87-p53(R273H) neurospheres showed resistance to differentiation into glial cells and neuronal cells with ATO and ATRA exposure. ATO was able to generate apoptosis at high doses and proliferation of U87-p53(wt) and U87-p53(R273H) cells was reduced with ATO and ATRA in a dose-dependent manner. Elevated pERK1/2 and p53 expression was seen in U87-p53(R273H) neurospheres, which could be reduced with ATO and ATRA treatment. Additionally, differential responses in pERK1/2 were seen with ATO treatment in neurospheres and non-neurosphere cells. In conclusion, codon-specific mutant p53 conferred a more aggressive phenotype to our CSC model. However, ATO and ATRA could potently suppress CSC properties in vitro and may support further clinical investigation of these agents.

Arsenic trioxide induces apoptosis in B-cell chronic lymphocytic leukemic cells through down-regulation of survivin via the p53-dependent signaling pathway

Arsenic trioxide (As2O3) can induce apoptosis in many tumors. However, the associated mechanisms are not clearly understood. We found that As2O3 significantly inhibited the proliferation of WSU-CLL cells and induced apoptosis in dose- and time-dependent manners. WSU-CLL cells treated with 2μM As2O3 showed survivin down-regulation and p53 up-regulation. Survivin siRNA combined with As2O3 further inhibited the proliferation of WSU-CLL cells. p53 inhibition by siRNA prevented the down-regulation of survivin by As2O3 and prevented the As2O3-induced cytotoxicity of WSU-CLL cells. These results suggest that As2O3 may be of therapeutic value for chronic lymphocytic leukemia.

Arsenic trioxide depletes cancer stem-like cells and inhibits repopulation of neurosphere derived from glioblastoma by downregulation of Notch pathway

Notch signaling has been demonstrated to have a central role in cancer stem-like cells (CSLCs) in glioblastoma multiforme (GBM). We have recently demonstrated the inhibitory effect of arsenic trioxide (ATO) on CSLCs in glioblastoma cell lines. In this study we used neurosphere recovery assay that measured neurosphere formation at three time points to assess the capacity of the culture to repopulate after ATO treatment. Our results provided strong evidence that ATO depleted CSLCs in GBM, and inhibited neurosphere recovery and secondary neurosphere formation. ATO inhibited the phosphorylation and activation of AKT and STAT3 through Notch signaling blockade. These data show that the ATO is a promising new approach to decrease glioblastoma proliferation and recurrence by downregulation of Notch pathway.

Factors determining sensitivity and resistance of tumor cells to arsenic trioxide

Previously, arsenic trioxide showed impressive regression rates of acute promyelocytic leukemia. Here, we investigated molecular determinants of sensitivity and resistance of cell lines of different tumor types towards arsenic trioxide. Arsenic trioxide was the most cytotoxic compound among 8 arsenicals investigated in the NCI cell line panel. We correlated transcriptome-wide microarray-based mRNA expression to the IC(50) values for arsenic trioxide by bioinformatic approaches (COMPARE and hierarchical cluster analyses, Ingenuity signaling pathway analysis). Among the identified pathways were signaling routes for p53, integrin-linked kinase, and actin cytoskeleton. Genes from these pathways significantly predicted cellular response to arsenic trioxide. Then, we analyzed whether classical drug resistance factors may also play a role for arsenic trioxide. Cell lines transfected with cDNAs for catalase, thioredoxin, or the anti-apoptotic bcl-2 gene were more resistant to arsenic trioxide than mock vector transfected cells. Multidrug-resistant cells overexpressing the MDR1, MRP1 or BCRP genes were not cross-resistant to arsenic trioxide. Our approach revealed that response of tumor cells towards arsenic trioxide is multi-factorial.

Protective effect of curcumin against arsenic-induced apoptosis in murine splenocytes in vitro

Arsenic is a potent environmental pollutant and immunotoxic agent. Curcumin is a natural anti-oxidant used to treat a broad variety of diseases. Here, the effects were investigated of curcumin on sodium arsenite-induced apoptosis in murine splenocytes in vitro. Cells were exposed to sodium arsenite (NaAsO₂, 5 µM) with and without curcumin (5 and 10 µg/ml) and incubated at 37°C for 12 h. NaAsO₂ caused a decrease in cell viability and induction of apoptosis. These outcomes were concurrent with increases in the numbers of cells with reactive oxygen species generation, loss of mitochondrial transmembrane potential, an increase in the frequency of cells with sub-G₁ DNA content, and DNA fragmentation. Co-administration of curcumin with the NaAsO₂ caused significant recoveries in cell viability values and mitigation of the induced apoptosis-related molecular changes. A significant protection against apoptosis parameters in murine splenocytes simultaneously treated with NaAsO₂ and curcumin suggested a protective efficacy of curcumin. From the results it is concluded that the immuno-modulation exerted by curcumin might be attributed to its multifaceted effects including its anti-oxidative and anti-apoptotic properties. These findings have implications not only for the under-standing of the toxicity of arsenic to murine splenocytes in vitro but are also potentially important for developing preventive and/or corrective strategies against/during chronic arsenicosis.

The use of in vitro systems to assess cancer mechanisms and the carcinogenic potential of chemicals

Carcinogenesis is a highly complex, multi-stage process that can occur over a relatively long period before its clinical manifestation. While the sequence in which a cancer cell acquires the necessary traits for tumour formation can vary, there are a number of mechanisms that are common to most, if not all, cancers across the spectrum of possible causes. Many aspects of carcinogenesis can be modelled in vitro. This has led to the development of a number of mechanistically driven, cell-based assays to assess the pro-carcinogenic and anti-carcinogenic potential of chemicals. A review is presented of the current in vitro models that can be used to study carcinogenesis, with examples of cigarette smoke testing in some of these models, in order to illustrate their potential applications. We present an overview of the assays used in regulatory genotoxicity testing, as well as those designed to model other aspects that are considered to be hallmarks of cancer. The latter assays are described with a view to demonstrating the recent advances in these areas, to a point where they should now be considered for inclusion in an overall testing strategy for chemical carcinogens.

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.

Arsenic trioxide-induced apoptosis in TM4 Sertoli cells: the potential involvement of p21 expression and p53 phosphorylation

Arsenic is a toxic metalloid that exists ubiquitously in the environment, and exhibits carcinogenicity. Conversely, arsenic trioxide (AsTO) has successfully been employed in the treatment of acute promyelocytic leukemia (APL). It has been shown that AsTO efficiently induces apoptosis in the malignant cells of APL in vitro. Although the mechanisms underlying AsTO-induced apoptosis in certain types of cancer cells, such as APL cells, have been delineated, the mechanism underlying AsTO-induced cell death in non-cancer cells remains unknown. In the present study, we examined AsTO-provoked cytotoxicity and cell death mechanism(s) in TM4 Sertoli cells. Exposure of these cells to AsTO generates reactive oxygen species and alters mitochondrial apoptosis, inducing cell death via both caspase-dependent and caspase-independent pathways. AsTO-induced apoptosis was concomitant with the downregulation of p53, phosphorylation of p53 at serine residues, and G2/M cell cycle arrest. Particularly, the interaction of p21 with caspase-3 proteins during AsTO treatment suggested an antiapoptotic role of p21 against genotoxic stresses in TM4 Sertoli cells. However, clinically relevant concentrations of AsTO failed to induce cell death in TM4 Sertoli cells, indicating that these cells could be resistant to cancer treatment. The results presented herein may not represent the actual effect of AsTO on Sertoli cells in vivo. Thus, further studies on the exposure effects of AsTO on the morphology and function of Sertoli cells in animal experiments will provide a more precise knowledge of AsTO cytotoxicity on male reproduction.

Inhibition of heme oxygenase-1 enhances anti-cancer effects of arsenic trioxide on glioma cells

We have previously reported that arsenic trioxide (ATO) could inhibit glioma growth both in vitro and in vivo, and demonstrated its potent therapeutic effects on gliomas. In this study we showed that ATO induced cell damage and heme oxygenase-1 (HO-1) expression in glioma cells via ROS generation. HO-1 inducer clearly protected from ATO-induced cell death and ROS generation, and HO-1 inhibitor led to a significant increase in cell death and ROS generation induced by ATO. In addition, knockdown of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) strongly inhibited HO-1 expression induced by ATO, and significantly enhanced ATO-induced oxidative damage. Our results demonstrated, for the first time, that HO-1 inhibition or Nrf2 knockdown significantly potentiated ATO's effects on glioma cells. Considering that HO-1 is highly expressed in glioma tissues, administration of ATO in combination with either HO-1 inhibitor or Nrf2 knockdown may act as a new approach to the treatment of glioma.

TP53 codon 72 polymorphism and colorectal cancer susceptibility: a meta-analysis

Colorectal cancer constitutes a significant proportion of the global burden of cancer morbidity and mortality. A number of studies have been conducted to explore whether TP53 codon 72 polymorphism is associated with colorectal cancer susceptibility. However, controversial results were obtained. In order to derive a more precise estimation of the relationship, we systematically searched Medline, Google scholar, and Ovid database for studies reported before May 2010. A total of 3603 colorectal cancer cases and 5524 controls were included. TP53 codon 72 polymorphism was not associated with colorectal cancer risk in all genetic models (for dominant model: OR = 0.99, 95% CI: 0.86-1.15; for recessive model: OR = 1.00, 95% CI: 0.81-1.23; for Arg/Pro vs. Arg/Arg: OR = 1.00, 95% CI: 0.87-1.15; for Pro/Pro vs. Arg/Arg: OR = 0.97, 95% CI: 0.76-1.25). In the subgroup analyses by ethnic groups and sources of controls, no significant associations were found in all models. Taken together, this meta-analysis suggested that the biologically usefulness of TP53 codon 72 polymorphism as a selection marker in colorectal cancer susceptibility may be very limited.

Expression of genes related to apoptosis, cell cycle and signaling pathways are independent of TP53 status in urinary bladder cancer cells

Urinary bladder cancer is the fourth most common malignancy in the Western world. Transitional cell carcinoma (TCC) is the most common subtype, accounting for about 90% of all bladder cancers. The TP53 gene plays an essential role in the regulation of the cell cycle and apoptosis and therefore contributes to cellular transformation and malignancy; however, little is known about the differential gene expression patterns in human tumors that present with the wild-type or mutated TP53 gene. Therefore, because gene profiling can provide new insights into the molecular biology of bladder cancer, the present study aimed to compare the molecular profiles of bladder cancer cell lines with different TP53 alleles, including the wild type (RT4) and two mutants (5637, with mutations in codons 280 and 72; and T24, a TP53 allele encoding an in-frame deletion of tyrosine 126). Unsupervised hierarchical clustering and gene networks were constructed based on data generated by cDNA microarrays using mRNA from the three cell lines. Differentially expressed genes related to the cell cycle, cell division, cell death, and cell proliferation were observed in the three cell lines. However, the cDNA microarray data did not cluster cell lines based on their TP53 allele. The gene profiles of the RT4 cells were more similar to those of T24 than to those of the 5637 cells. While the deregulation of both the cell cycle and the apoptotic pathways was particularly related to TCC, these alterations were not associated with the TP53 status.

Abrogating HSP response augments cell death induced by As2O3 in glioma cell lines

OBJECTIVES

We previously reported that Arsenic trioxide (ATO) can inhibit glioma growth both in vitro and in vivo. While the use of ATO alone for solid tumor treatment sometimes was found to be ineffective which may be due to the protective pathways including heat shock proteins (HSPs) response induced by ATO. In this study, we modified HSPs expression to investigate whether HSPs had some effect on ATO induced glioma cell death.

METHODS

Trypan bule exclusion assay, mitochondrial membrane potential (MMP) Assay, and SubG1 detection were used to evaluate cell viability and western-blot was employed to detect HSPs and some apoptosis markers expression induced by ATO. Heat pre-treatment, HSPs inhibitor, or Heat Shock factor-1 (HSF1) knockdown by SiRNA was employed to modify HSPs levels.

RESULTS

It was showed that KNK437 (HSPs inhibitor) or HSF1 knockdown significantly enhanced cell death, MMP disruption, JNK phosphorylation and caspase-3 cleavage induced by ATO, which was accompanied by abrogation of HSPs induction, while heat pre-treatment with clear HSPs induction had strong protection on the effects mentioned above.

CONCLUSION

Those data suggested that HSPs play protective roles on ATO induced cell death in glioma. Inhibition of HSPs may have a synergistic effect with ATO on glioma treatment.

Differential role of cathepsins B and L in autophagy-associated cell death induced by arsenic trioxide in U87 human glioblastoma cells

Arsenic trioxide (arsenite) was the first chemotherapeutic drug to be described and is now being rediscovered in cancer treatment, including glioblastoma multiforme. Arsenite toxicity triggers autophagy in cancer cells, although final stages of the process involve executive caspases, suggesting an interplay between autophagic and apoptotic pathways that awaits to be explained at a molecular level. We evaluated the contribution of the lysosomal cathepsins (Cat) L and B, which are upregulated in glioblastomas, in the mechanism of arsenite toxicity in human glioblastoma cells. Arsenite treatment induced autophagosome formation and permeabilization of mitochondria, followed by caspase 3/7-mediated apoptosis. The autophagy inhibitor 3-methyladenine protected from arsenite toxicity, whereas bafilomycin A1 did not. Furthermore, arsenite significantly decreased CatB levels and selectively inhibited its cellular and recombinant protein activity, while not affecting CatL. However, downregulation of CatL greatly enhanced apoptosis by arsenite. Our results show that arsenite toxicity involves a complex interplay between autophagy and apoptosis in human glioblastoma cells and is associated with inhibition of CatB, and that this toxicity is highly exacerbated by simultaneous CatL inhibition. The latter points to a synergy that could be used in clinical treatment to lower the therapeutic dose, thus avoiding the toxic side effects of arsenite in glioblastoma management.

Effects of thymoquinone on isolated and cellular proteasomes

Thymoquinone, a naturally derived agent, has been shown to possess antioxidant, antiproliferative and proapoptotic activities. In the present study, we explored thymoquinone effects on the proteasomal complex, the major system involved in the removal of damaged, oxidized and misfolded proteins. In purified 20S complexes, subunit-dependent and composition-dependent inhibition was observed, and the chymotrypsin-like and trypsin-like activities were the most susceptible to thymoquinone treatment. U87 MG and T98G malignant glioma cells were treated with thymoquinone, and 20S and 26S proteasome activity was measured. Inhibition of the complex was evident in both cell lines, but predominantly in U87 MG cells, and was accompanied by accumulation of ubiquitin conjugates. Accumulation of p53 and Bax, two proteasome substrates with proapoptotic activity, was observed in both cell lines. Our results demonstrate that thymoquinone induces selective and time-dependent proteasome inhibition, both in isolated enzymes and in glioblastoma cells, and suggest that this mechanism could be implicated in the induction of apoptosis in cancer cells.

Sodium arsenite mediated immuno-disruption through alteration of transcription profile of cytokines in chicken splenocytes under in vitro system

Arsenic is a ubiquitously found metalloid that commonly contaminates drinking water and agricultural food. To understand the ecotoxicological effects of arsenic in environment, it is essential to ameliorate the deleterious effects on human and animal health, particularly on the immune response. We investigated the effects of inorganic arsenic (iAs) on the immune response of chicken splenocytes. Both 1 and 10 mM concentrations of sodium arsenite treatment significantly reduced (P<0.001) splenocyte proliferation and phagocytic activity compared to concanavalin A (ConA) stimulated cells at 24, 48 and 72 h of incubation. Nitrous oxide (NO) production was significantly higher (P<0.001) at 24 h and subsequently declined in the higher dose group, while there was a gradual decline from 24 to 72 h in the lower dose group. Comparison of two different concentration of arsenic treatment also revealed time dependent differences. Relative quantification of expression of IFNγ and IL2 revealed that both genes were significantly down regulated (P<0.001) at both concentrations at each time point. iNOS gene was rapidly down regulated in splenocytes at 24 h at the high doses of As treated splenocyte, a gradual decreasing trend at low doses. Down regulation of IL-2 gene expression in response to As was further evidenced by a significant reduction (P<0.001) in the release of IL-2 into the splenocyte culture medium. We suggest that arsenic, a potent immunotoxic agent, modulates non-specific immune responses and alters the expression of cytokines in a dose and time dependent manner.

Inhibition of ADP-ribosylation factor-like 6 interacting protein 1 suppresses proliferation and reduces tumor cell invasion in CaSki human cervical cancer cells

ADP-ribosylation factor-like 6 interacting protein 1 (ARL6IP1) is an apoptotic regulator. To investigate the role of ARL6IP1 in human cervical cancer progression, we designed and used short hairpin RNA (shRNA) to inhibit ARL6IP1 expression in CaSki cells and validated its effect on cell proliferation and invasion. Changes in gene expression were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) or western blot. Down-regulation of ARL6IP1 expression by infection with ARL6IP1-specific RNAi-expressing vector inhibited CaSki cell proliferation and colony formation. In addition, down-regulation of ARL6IP1 expression arrested CaSki cell cycling at the G0/G1 phase and mitigated CaSki cell migration, determined by wound healing assays. ARL6IP1 was involved in cervical cancer cell growth, cell cycle progression, and invasion through regulation of gene expression, such as Caspase-3, Caspase-9, p53, TAp63, NF-κB, MAPK, Bcl-2, and Bcl-xL, suggesting that ARL6IP1 could have important implications in cervical cancer biology. Our findings illustrate the biological significance of ARL6IP1 in cervical cancer progression, and provide novel evidence that ARL6IP1 may serve as a therapeutic target in the prevention of human cervical cancer.

Arsenic trioxide and cisplatin synergism increase cytotoxicity in human ovarian cancer cells: therapeutic potential for ovarian cancer

Drug resistance is a major concern in the successful treatment of ovarian cancer. In the present study we report a combinational drug regime using arsenic trioxide (ATO) and cisplatin (CDDP) to increase therapeutic potentiality in ovarian cancer cells. ATO-mediated growth inhibition and apoptosis in human suspension ovarian cancer COC1 cells were evaluated by MTT assay and annexin V assay using flow cytometry, respectively. cDNA arrays were performed to screen ATO-mediated gene expression. Treatment of COC1 cells with ATO alone resulted in growth inhibition and apoptosis with a dose-and time-dependent fashion; further cDNA arrays showed that 34 genes (23 up-regulated genes and 11 down-regulated genes) may strongly associate with the antiproliferative and pro-apoptotic effects induced by ATO. Furthermore, Chou-Talalay analysis was used to evaluate the combinational effect of ATO and CDDP as well as dose-reduction index (DRI) in a panel of ovarian cancer cells including CDDP-sensitive and -resistant cell lines. The combination index (CI) analysis indicated that the interaction effect of ATO/CDDP exhibited a wide range of synergism in all the adherent ovarian cancer cells (A2780, IGROV-1, SKOV-3, and R182) as well as 0.93 to 0.69 for IC(50) to IC(90) in suspension COC1 cells where CI < 1, =1, and >1, define synergism, additive effect, and antagonism, respectively. More intriguingly, the combination of ATO and CDDP yielded favorable DRIs ranging from 1.23-fold to 13.51-fold dose reduction. These results suggest that ATO and its combination with CDDP present therapeutic potential for ovarian cancer, and deserve further preclinical and clinical studies.

Arsenic trioxide induces apoptosis and G2/M phase arrest by inducing Cbl to inhibit PI3K/Akt signaling and thereby regulate p53 activation

Arsenic trioxide (ATO) strongly induces apoptosis in acute promyelocytic leukemia (APL), but it induces cell cycle arrest in most solid tumors. In this study, we investigated the mechanism of ATO action on APL-derived NB4 cells and gastric cancer cell lines. ATO decreased the viability of both cell lines, but gastric cancer cells were much less susceptible. ATO-induced G2/M phase arrest and p53 degradation in gastric cancer MGC803 cells. In contrast, ATO-induced apoptosis in NB4 cells without degradation of p53. Both processes were accompanied by transient activation of Akt. The PI3K/Akt inhibitor LY294002 significantly increased the amount of p53 protein and ATO-induced apoptosis in both cell lines and decreased G2/M phase arrest of MGC803 cells. In addition, ATO up-regulated the expression of Cbl proteins in both cell lines. Inhibition of Cbl with the proteasome inhibitor Ps341 decreased apoptosis in NB4 cells and increased the G2/M phase arrest of MGC803 cells, and it also prolonged the activation of PI3K/Akt by ATO. Consistent results with those in MGC803 cells were showed in gastric cancer cell BGC823 and SGC7901 after ATO treatment. These results demonstrate that inhibition of PI3K/Akt signaling by Cbl is involved in both ATO-induced apoptosis of NB4 cells and ATO-induced G2/M phase arrest of gastric cancer cells. Cbl achieved these effects probably via its regulating PI3K/Akt pathway, and thereby modulated p53 activation.

Arsenic trioxide induces the apoptosis in vascular smooth muscle cells via increasing intracellular calcium and ROS formation

The present study was designed to investigate whether arsenic trioxide induced the apoptosis in rat mesenteric arterial smooth muscle cells (SMCs), which provides new insights into mechanisms of arsenic-related vascular diseases. Here, we found that arsenic trioxide significantly decreased the viability of SMCs in a dose-dependent manner. In addition, higher level of arsenic trioxide directly caused cellular necrosis. The Hoechst and AO/EB staining demonstrated that apoptotic morphological change was presented in SMCs exposed to arsenic trioxide. The TUNEL assay displayed that more positive apoptotic signal appeared in SMCs treated with arsenic trioxide. The following result showed that ROS formation was markedly increased in arsenic trioxide-treated SMCs. Pretreatment with N-acetylcysteine, an anti-oxidant reagent, obviously attenuated the enhancement of ROS production and the reduction of cell viability induced by arsenic trioxide in SMCs. Arsenic trioxide also enhanced free intracellular Ca(2+) level in SMCs. BAPTA also significantly prevented the increased intracellular Ca(2+) and decreased cell viability induced by arsenic trioxide in SMCs. These results suggested that arsenic trioxide obviously induced apoptosis in SMCs, and its mechanism was partially associated with intracellular ROS formation and free Ca(2+) increasing.