Arsenic trioxide enhances the radiation sensitivity of androgen-dependent and -independent human prostate cancer cells

Arsenic-induced prostate cancer: an enigma

Arsenic exhibits varying degrees of toxicity depending on its many chemical forms. The carcinogenic properties of arsenic have already been established. However, the precise processes underlying the development of diseases following acute or chronic exposure to arsenic remain poorly known. Most of the existing investigation has focused on studying the occurrence of cancer following significant exposure to elevated levels of arsenic. Nevertheless, multiple investigations have documented diverse health consequences from prolonged exposure to low levels of arsenic. Inorganic arsenic commonly causes lung, bladder, and skin cancer. Some investigations have shown an association between arsenic in drinking water and prostate cancer, but few investigations have focused on exploring this connection. There is currently a lack of relevant animal models demonstrating a clear link between inorganic arsenic exposure and the development of prostate cancer. Nevertheless, studies using cellular model systems have demonstrated that arsenic can potentially promote the malignant transformation of human prostate epithelial cells in vitro. The administration of elevated levels of arsenic has been demonstrated to elicit cell death in instances of acute experimental exposure. Conversely, in cases of chronic exposure, arsenic prompts cellular proliferation and sustains cellular viability, thereby circumventing the constraints imposed by telomere shortening and apoptosis. Furthermore, cells consistently exposed to the stimulus exhibit an augmented ability to invade surrounding tissues and an enhanced potential to form tumors. This review aims to portray mechanistic insights into arsenic-induced prostate cancer.

Combination treatment with cyclosporin A and arsenic trioxide induce synergistic cell death via non-apoptotic pathway in uterine cervical cancer cells

Cyclosporin A is an immunosuppressive drug with anti-cancer effect. Arsenic trioxide (As₂O₃), a well-known cancer-inhibiting drug, induced cytotoxicity via apoptosis and autophagy. The aim of this study is to evaluate the effect of combinational treatment with cyclosporin A and arsenic trioxide on cell viability inhibition in cervical cancer cells. Using MTT assay and combination index, combinational treatment with cyclosporin A and arsenic trioxide induced a synergistic cytotoxic effect in Caski and SiHa cells. Cyclosporin A and arsenic trioxide triggered cell death via non-apoptotic pathway by using annexin V/propidium iodide (PI) assay. Cyclosporin A and arsenic trioxide combined treatment decreased mitochondrial membrane potential and increase reactive oxygen species (ROS) generation. This co-treatment increased LC3B-II expression and autophagosome formation in cervical cancer cells. This study first demonstrated that combinational treatment with cyclosporin A and As₂O₃ trigger synergistic cytotoxic effect via autophagy in cervical cancer cells.

Human prostate cancer cell epithelial-to-mesenchymal transition as a novel target of arsenic trioxide and curcumin therapeutic approach

BACKGROUND

Arsenic trioxide (As₂O₃) as an inorganic compound is used to treat various cancers and other diseases. It has been reported that arsenic trioxide induced cellular apoptosis in certain kinds of cancers, including prostate cancers. The present study aimed to elucidate the crucial cooperative role of arsenic trioxide and Curcumin and their ability to protect against prostate cancers by targeting the epithelial-to-mesenchymal transition and expression of apoptosis-related genes.

MATERIAL AND METHODS

The human prostate cell lines (LNCaP and PC3) were treated with different concentrations of Curcumin and As₂O₃ alone and combined to find effective doses and IC50 values. Percentages of apoptotic cells were evaluated by Annexin/P.I. staining, the proliferative inhibitory effect was assessed by Micro Culture Tetrazolium Test (MTT), and mRNA levels of KLK2, E-cadherin, SNAIL, angiogenesis genes (VEGFA and VEGFC), and apoptosis genes (BAX, Bcl₂, and P53) expression were investigated by the real-time PCR method. ANOVA and t-test were used to appraise the results.

RESULTS

For the first time, we presented that the combination therapy of Curcumin and As₂O₃ increases prostate cancer cell apoptosis and inhibits proliferation; Our data displayed that Curcumin (15 μM and 10 μM in PC3 and LNCap), As₂O₃ (8 μM and 5 μM in PC3 and LNCap), and also their combination (15 μM Curcumin and 8 μM As₂O₃ in PC3, 10 μM Curcumin and 5 μM As₂O₃ in LNCap cell lines) significantly increased the percentage of apoptotic cells and inhibited cell growth (P < 0.05) compared with each drug alone. Generally, both cell lines treated with the combination of Curcumin and As₂O₃ displayed decreased angiogenesis genes (VEGFA and VEGFC), apoptosis genes (BAX and Bcl2), and prostate cancer marker (KLK2), the zinc-finger protein (SNAIL); and an increase in expression (P < 0.05) of cell-cell adhesion molecule (E-cadherin) and tumor suppressor gene (P53) genes.

CONCLUSIONS

The antitumor effects of combination therapy with As₂O₃ and Curcumin have been displayed on prostate cancer cell lines (LNCaP and PC3), which probably originates from their potential to induce apoptosis and inhibit the growth of prostate cancer cells simultaneously.

Combined anticancer effects of simvastatin and arsenic trioxide on prostate cancer cell lines via downregulation of the VEGF and OPN isoforms genes

Arsenic trioxide (ATO) and statins have been demonstrated to have anti‐neoplastic properties; however, the data regarding their combination therapy is limited. Thus, we aimed to study the effects of ATO, Simvastatin and their combination in proliferation, apoptosis and pathological angiogenesis in prostate cancer cell lines. The human prostate cell lines were treated with different concentrations of Simvastatin and ATO alone and combined to find effective doses and IC50 values. In addition, the percentage of apoptotic cells was evaluated by annexin/PI staining, and mRNA expression levels of the apoptotic gene, including OPN isoforms and VEGF, were investigated using real‐time PCR. Our data displayed that Simvastatin (12 and 8 μM in PC3 and LNCaP cell lines respectively), ATO (8 and 5 μM in PC3 and LNCaP cell lines respectively), and also their combination (12 μM Simvastatin and 8 μM ATO in PC3, 8 μM Simvastatin and 5 μM ATO in LNCaP cell lines respectively) significantly increased the percentage of apoptotic cells. Also, we showed that the combination therapy by Simvastatin and ATO increased cell apoptosis and inhibited cell proliferation, providing anti‐proliferative and anti‐angiogenic properties, possibly via downregulation of the expression of VEGF and OPN genes. These results provide new perceptions regarding the anticancer roles of ATO and statins’ combination therapy in prostate cancer.

Positive Aspects of Oxidative Stress at Different Levels of the Human Body: A Review

Oxidative stress is the subject of numerous studies, most of them focusing on the negative effects exerted at both molecular and cellular levels, ignoring the possible benefits of free radicals. More and more people admit to having heard of the term "oxidative stress", but few of them understand the meaning of it. We summarized and analyzed the published literature data in order to emphasize the importance and adaptation mechanisms of basal oxidative stress. This review aims to provide an overview of the mechanisms underlying the positive effects of oxidative stress, highlighting these effects, as well as the risks for the population consuming higher doses than the recommended daily intake of antioxidants. The biological dose-response curve in oxidative stress is unpredictable as reactive species are clearly responsible for cellular degradation, whereas antioxidant therapies can alleviate senescence by maintaining redox balance; nevertheless, excessive doses of the latter can modify the redox balance of the cell, leading to a negative outcome. It can be stated that the presence of oxidative status or oxidative stress is a physiological condition with well-defined roles, yet these have been insufficiently researched and explored. The involvement of reactive oxygen species in the pathophysiology of some associated diseases is well-known and the involvement of antioxidant therapies in the processes of senescence, apoptosis, autophagy, and the maintenance of cellular homeostasis cannot be denied. All data in this review support the idea that oxidative stress is an undesirable phenomenon in high and long-term concentrations, but regular exposure is consistent with the hormetic theory.

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.

The role of autophagy in metal-induced urogenital carcinogenesis

Environmental and/or occupational exposure to metals such as Arsenic (As), Cadmium (Cd), and Chromium (Cr) have been shown to induce carcinogenesis in various organs, including the urogenital system. However, the mechanisms responsible for metal-induced carcinogenesis remain elusive. We and others have shown that metals are potent inducers of autophagy, which has been suggested to be an adaptive stress response to allow metal-exposed cells to survive in hostile environments. Albeit few, recent experimental studies have shown that As and Cd promote tumorigenesis via autophagy and that inhibition of autophagic signaling suppressed metal-induced carcinogenesis. In light of the newly emerging role of autophagic involvement in metal-induced carcinogenesis, the present review focuses explicitly on the mechanistic role of autophagy and potential signaling pathways involved in As-, Cd-, and Cr-induced urogenital carcinogenesis.

Autophagy and Pituitary Adenoma

Pituitary adenomas (PAs) are common, benign intracranial tumors that are usually effectively controlled with surgery, pharmacotherapy or radiotherapy. Some PAs against which conventional treatment is ineffective are great clinical challenges at present. Autophagy is a widespread physiological process in cells. Through autophagy, cells can degrade damaged or redundant proteins and organelles and achieve the recycling of intracellular substances to maintain the homeostasis of the intracellular environment. An increasing number of studies have demonstrated the importance of autophagy in tumor therapy. Both radiotherapy and chemotherapy can induce autophagy, which plays different roles in the course of therapy. In recent years, there has been growing interest in the role of autophagy during the treatment of PAs. This chapter reviews the recent progress of research on autophagy in PA and the autophagic mechanisms in the treatment of PA.

Biological and molecular modifications induced by cadmium and arsenic during breast and prostate cancer development

Breast and prostate cancer are two of the most common malignancies worldwide. Both cancers can develop into hormone -dependent or -independent subtypes and are associated to environmental exposure in the context of an inherited predisposition. As and Cd have been linked to the onset of both cancers, with the exception of As, which lacks a definitive association with breast carcinogenesis. The two elements exert an opposite effect dependent on acute versus chronic exposure. High doses of As or Cd were shown to induce cell death in acute experimental exposure, while chronic exposure triggers cell proliferation and viability, which is no longer limited by telomere shortening and apoptosis. The chronically exposed cells also increase their invasion capacity and tumorigenic potential. At molecular level, malignant transformation is evidenced mainly by up-regulation of BCL-2, MMP-2, MMP-9, VIM, Snail, Twist, MT, MLH and down-regulation of Casp-3, PTEN, E-CAD, and BAX. The signaling pathways most commonly activated are KRAS, p53, TGF-β, TNF-α, WNT, NRF2 and AKT. This knowledge could potentially raise public awareness over the health risks faced by the human population living or working in a polluted environment and smokers. Human exposure to As and Cd should be minimize as much as possible. Healthcare policies targeting people belonging to these risk categories should include analysis of: DNA damage, oxidative stress, molecular alterations, and systemic level of heavy metals and of essential minerals. In this review, we present the literature regarding cellular and molecular alterations caused by exposure to As or Cd, focusing on the malignant transformation of normal epithelial cells after long-term intoxication with these two carcinogens.

Bortezomib enhances radiosensitivity in oral cancer through inducing autophagy-mediated TRAF6 oncoprotein degradation

Background

Oral squamous cell carcinoma (OSCC) is a malignant tumor that may occur anywhere within the oral cavity. The survival rate of OSCC patients has not improved over the past decades due to its heterogeneous etiology, genetic aberrations, and treatment outcomes. We investigated the role of tumor necrosis factor receptor-associated factor 6 (TRAF6) in OSCC cells treated with bortezomib (a proteasome inhibitor) combined with irradiation (IR) treatment.

Methods

The effects of combined treatment in OSCC cells were investigated using assays of cell viability, autophagy, apoptosis, western blotting, and immunofluorescence staining. The ubiquitination of proteins was analyzed by immunoprecipitation. Stable knockdown of TRAF6 in OSCC cells was constructed with lentivirus. The xenograft murine models were used to observe tumor growth.

Results

We found synergistic effects of bortezomib and IR on the viability of human oral cancer cells. The combination of bortezomib and IR treatment induced autophagic cell death. Furthermore, bortezomib inhibited IR-induced TRAF6 ubiquitination and inhibited TRAF6-mediated Akt activation. Bortezomib reduced TRAF6 protein expression through autophagy-mediated lysosomal degradation. TRAF6 played an oncogenic role in tumorigenesis of human oral cancer cells and oral tumor growth was suppressed by bortezomib and IR treatment. In addition, OSCC patients with expression of TRAF6 showed a trend towards poorer cancer-specific survival when compared with patients without TRAF6 expression.

Conclusions

A combination of a proteasome inhibitor, IR treatment and TRAF6 inhibition could be a novel therapeutic strategy in OSCC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0760-0) contains supplementary material, which is available to authorized users.

Personalized therapy: CNS HGNET-BCOR responsiveness to arsenic trioxide combined with radiotherapy

High-grade neuroepithelial tumor of the central nervous system with BCOR alteration (HGNET-BCOR) is a rare, highly malignant tumor. At the time of this publication, no standard protocol exists to treat this tumor entity. In this work, we tested the responsiveness of the primary culture PhKh1 derived from tumor tissue from a pediatric HGNET-BCOR patient (P1) to inhibitors of the Sonic hedgehog pathway combined with radiation. The SMO inhibitors vismodegib and itraconazole had low effect on the proliferation of the PhKh1 cells. However, the GLI inhibitor arsenic trioxide reduced the expression of GLI target genes in the PhKh1 cells and in combination with radiotherapy significantly decreased their clonogenic potential. PhKh1 cells resistant to arsenic trioxide were characterized by the overexpression of molecular chaperones. We combined arsenic trioxide and radiation in the relapse therapy protocol of P1, achieving complete remission after seven weeks. Clinical remission lasted for six months, when P1 developed systemic metastases. Meanwhile, an increase in the concentration of circulating tumor DNA carrying a BCOR internal tandem duplication was observed. Molecular characterization of a second patient (P2) was also performed. In P2, we detected a larger tandem duplication and greater activation of the Sonic hedgehog pathway than in P1. These findings suggest that combining arsenic trioxide with radiotherapy may represent a new therapeutic approach. Moreover, peripheral blood analysis for circulating tumor DNA could help in the early detection of systemic metastases.

Synergistic Effects of Arsenic Trioxide and Radiation: Triggering the Intrinsic Pathway of Apoptosis

Background

Arsenic trioxide (ATO) has been reported as an effective anti-cancer and a US Food and Drug Administration (FDA) approved drug for treatment of some cancers. The aim of this study was to determine the underlying apoptosis molecular and cellular mechanisms of ATO in the presence or absence of ionizing radiation (IR) in vitro in the glioblastoma multiforme (GBM) cell line, U87MG.

Methods

Cells were treated by different concentrations of ATO either in presence or absence of IR. Viability and apoptosis pathway of both treated and control groups were evaluated using MTT assay and the expression analysis of Bax, Bcl-2, and caspase-3 genes, respectively. All treatments were performed on 100-μm diameter spheroids.

Results

Results showed a significant reduction in the survival of the cells in all treated groups. As expected, cell survival was much less in combination treatment than treatment with only ATO. Moreover, combination therapy made Bax and caspase-3 up-regulated and Bcl-2 down-regulated.

Conclusion

ATO and radiation had a synergistic apoptotic effect on GBM cells by up-regulation of caspase-3 and alteration of the Bax-Bcl-2 balance; therefore, ATO may act as a potential anti-cancer agent against GBM cells through triggering the mitochondrial pathway of apoptosis.

The protective role of autophagy in experimental osteoarthritis, and the therapeutic effects of Torin 1 on osteoarthritis by activating autophagy

Background

Recent studies have shown that autophagy was associated with the development of osteoarthritis (OA), the purpose of this research was to determine the exact role of autophagy in OA and investigate effective therapeutic drugs to inhibit the pathological progression of OA.

Methods

In this study, a cellular OA model was generated by stimulating SW1353 cells with IL-1β and a rabbit OA model was established by intra-articular injection of collagenase, followed by treatment with Torin 1 or 3-Methyladenine (3-MA). The mRNA expression levels of VEGF, MMP-13 and TIMP-1 were determined by quantitative real-time PCR. The caitilage degeneration was examined by histological evaluation, chondrocytes degeneration and autophagosomes were observed by transmission electron microscopy. Expression levels of Beclin-1 and LC3 were evaluated by western blotting and immunofluorescence.

Results

The degeneration of SW 1353 cells, cartilage and chondrocytes was related to the loss of autophagy in experimental OA. 3-MA increased the severity of degeneration of cells and cartilage by autophagy inhibition, while Torin 1 reduced that by autophagy activation.

Conclusions

The loss of autophagy is linked with the experimental OA and autophagy may play a protective role in the pathogenesis of OA. Treatment of Torin 1 can inhibit the degenerative changes of experimental OA by activating autophagy and it may be a useful therapeutic drug for OA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-0995-x) contains supplementary material, which is available to authorized users.

Arsenic trioxide inhibits viability and induces apoptosis through reactivating the Wnt inhibitor secreted frizzled related protein-1 in prostate cancer cells

Background

Growing evidence suggests that arsenic trioxide (As₂O₃) induces apoptosis and inhibits tumor cell growth in prostate cancer (PCa), although details of the mechanism are still inconclusive. We investigated the antitumor effect of As₂O₃ in human PCa cell lines LNCaP and PC3 and the underlying mechanisms by focusing on the Wnt signaling pathway.

Methods

The effect of As₂O₃ on the viability and apoptosis of PCa cells was investigated by cholecystokinin-8 and flow cytometry. The expression of the related proteins in the Wnt signaling pathway and the downstream target genes of the Wnt signaling pathway was examined by Western blot and quantitative real-time PCR assay. The methylation status of the SFRP1 gene promoter was assessed by bisulfite sequencing.

Results

As₂O₃ inhibited the viability of PCa cells and induced apoptosis of PCa cells in a dose-dependent manner. The protein level of phosphoglycogen synthase kinase-3β was upregulated, whereas the protein level of β-catenin and the mRNA levels of c-MYC, MMP-7, and COX-2 were downregulated in a dose-dependent manner in PCa cells treated with As₂O₃. In addition, As₂O₃ upregulated the protein and mRNA levels of secreted frizzled related protein-1, and increased the demethylation of the SFRP1 gene promoter.

Conclusion

Our results suggest that As₂O₃ may inhibit cell viability and induce apoptosis through reactivating the Wnt inhibitor secreted frizzled related protein-1 in both androgen-dependent and -independent human PCa.

Increased Oxidative Stress as a Selective Anticancer Therapy

Reactive oxygen species (ROS) are closely related to tumorgenesis. Under hypoxic environment, increased levels of ROS induce the expression of hypoxia inducible factors (HIFs) in cancer stem cells (CSCs), resulting in the promotion of the upregulation of CSC markers, and the reduction of intracellular ROS level, thus facilitating CSCs survival and proliferation. Although the ROS level is regulated by powerful antioxidant defense mechanisms in cancer cells, it is observed to remain higher than that in normal cells. Cancer cells may be more sensitive than normal cells to the accumulation of ROS; consequently, it is supposed that increased oxidative stress by exogenous ROS generation therapy has an effect on selectively killing cancer cells without affecting normal cells. This paper reviews the mechanisms of redox regulation in CSCs and the pivotal role of ROS in anticancer treatment.

Chinese medicines induce cell death: the molecular and cellular mechanisms for cancer therapy

Chinese medicines have long history in treating cancer. With the growing scientific evidence of biomedical researches and clinical trials in cancer therapy, they are increasingly accepted as a complementary and alternative treatment. One of the mechanisms is to induce cancer cell death. Aim. To comprehensively review the publications concerning cancer cell death induced by Chinese medicines in recent years and provide insights on anticancer drug discovery from Chinese medicines. Materials and Methods. Chinese medicines (including Chinese medicinal herbs, animal parts, and minerals) were used in the study. The key words including “cancer”, “cell death”, “apoptosis”, “autophagy,” “necrosis,” and “Chinese medicine” were used in retrieval of related information from PubMed and other databases. Results. The cell death induced by Chinese medicines is described as apoptotic, autophagic, or necrotic cell death and other types with an emphasis on their mechanisms of anticancer action. The relationship among different types of cell death induced by Chinese medicines is critically reviewed and discussed. Conclusions. This review summarizes that CMs treatment could induce multiple pathways leading to cancer cell death, in which apoptosis is the dominant type. To apply these preclinical researches to clinic application will be a key issue in the future.

Berberine inhibits the expression of hypoxia induction factor-1alpha and increases the radiosensitivity of prostate cancer

Abstract

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1519827543125021.

3-Methyl pyruvate enhances radiosensitivity through increasing mitochondria-derived reactive oxygen species in tumor cell lines

Considerable interest has recently been focused on the special characteristics of cancer metabolism, and several drugs designed to modulate cancer metabolism have been tested as potential anticancer agents. To date, however, very few studies have been conducted to investigate the combined effects of anticancer drugs and radiotherapy. In this study, to evaluate the role of mitochondria-derived reactive oxygen species (ROS) in the radiation-induced cell death of tumor cells, we have examined the effect of 3-methyl pyruvate (MP). MP is a membrane-permeable pyruvate derivative that is capable of activating mitochondrial energy metabolism in human lung carcinoma A549 cells and murine squamous carcinoma SCCVII cells. Pretreatment with MP significantly enhanced radiation-induced cell death in both cell lines, and also led to increases in the mitochondrial membrane potential, intracellular adenosine triphosphate content, and mitochondria-derived ROS production following the exposure of the cells to X-rays. In A549 cells, MP-induced radiosensitization was completely abolished by vitamin C. In contrast, it was partially abolished in SCCVII cells. These results therefore suggest that the treatment of the cells with MP induced radiosensitization via the production of excess mitochondria-derived ROS in tumor cells.

Redox-mediated and ionizing-radiation-induced inflammatory mediators in prostate cancer development and treatment

SIGNIFICANCE

Radiation therapy is widely used for treatment of prostate cancer. Radiation can directly damage biologically important molecules; however, most effects of radiation-mediated cell killing are derived from the generated free radicals that alter cellular redox status. Multiple proinflammatory mediators can also influence redox status in irradiated cells and the surrounding microenvironment, thereby affecting prostate cancer progression and radiotherapy efficiency.

RECENT ADVANCES

Ionizing radiation (IR)-generated oxidative stress can regulate and be regulated by the production of proinflammatory mediators. Depending on the type and stage of the prostate cancer cells, these proinflammatory mediators may lead to different biological consequences ranging from cell death to development of radioresistance.

CRITICAL ISSUES

Tumors are heterogeneous and dynamic communication occurs between stromal and prostate cancer cells, and complicated redox-regulated mechanisms exist in the tumor microenvironment. Thus, antioxidant and anti-inflammatory strategies should be carefully evaluated for each patient at different stages of the disease to maximize therapeutic benefits while minimizing unintended side effects.

FUTURE DIRECTIONS

Compared with normal cells, tumor cells are usually under higher oxidative stress and secrete more proinflammatory mediators. Thus, redox status is often less adaptive in tumor cells than in their normal counterparts. This difference can be exploited in a search for new cancer therapeutics and treatment regimes that selectively activate cell death pathways in tumor cells with minimal unintended consequences in terms of chemo- and radio-resistance in tumor cells and toxicity in normal tissues.

Enhancement of chondrocyte autophagy is an early response in the degenerative cartilage of the temporomandibular joint to biomechanical dental stimulation

Autophagy is a cell protective mechanism for maintaining cellular homeostasis. The present study aimed to investigate whether autophagy is enhanced in the biomechanically induced degenerative cartilage of the temporomandibular joint (TMJ) and the potential role of mitogen-activated protein kinase kinase kinase kinase 3 (MAP4K3) and mammalian Target of rapamycin (mTOR) in this observation. To induce degenerative changes in the TMJs, rats were subjected to biomechanical dental stimulation by moving 4 molars away from their original position as we previously reported. The ultrastructure of autophagosome was observed by transmission electron microscopy. The number of lysosomes was analyzed by flow cytometry. The expression levels of Beclin1 and LC3 and the involvement of MAP4K3 activity were detected by immunohistochemistry, real-time PCR and western blot. The activity of the mTOR pathway indicated by p-mTOR and p-p70S6 K was assayed by western blot. TMJ degeneration, characterized by irregular cell arrangement and cell-free area, was induced in the experimental groups. Under transmission electron microscopy, we observed the presence of autophagosomes, small patches of condensed chromatin, abundant rough endoplasmic reticulum and Golgi apparatus. The number of lysosomes and the expression levels of Beclin1 and LC3 increased, while the activity of mTOR and the expression level of MAP4K3 decreased in the experimental groups. Cartilage in TMJ which was induced to be degenerative biomechanically exhibited autophagy accompanied by reduced mTOR and MAP4K3 activity.

Impact of long-term exposure to sodium arsenite on cytogenetic radiation damage

The aim of this work was to investigate the impact of long-term exposure to low concentrations of sodium arsenite on the cellular response to ionising radiation. Human lymphoblastoid GM1899a cells were cultured in the presence of sodium arsenite for up to six months. Following chemical exposure, acute challenge doses of X-rays were given and chromosome damage (dicentrics, acentric fragments, translocations, micronuclei) as well as cell growth and changes in cell cycle kinetics were determined. Initial short-term chemical exposures determined 8 ng/ml (60 nM) sodium arsenite as a suitable concentration for chronic exposures, which is below the current World Health Organization limit for arsenic in drinking water. At this concentration, cell growth was slightly, but consistently, slower than in untreated cultures throughout the six-month exposure period. Long-term exposure to the chemical induced no dicentrics and did not significantly alter the yield of dicentrics induced by 1 Gy acute X-irradiation. Similar results were obtained for chromosome translocations. In contrast, exposure to 8 ng/ml sodium arsenite induced significant levels of acentric fragments and micronuclei. Fragment/micronuclei data in combined treatment samples compared with single treatments were consistent with an additive effect of chemical and radiation exposure. As for X-rays, micronuclei induced by sodium arsenite tended to show no centromere in situ hybridisation signal, indicating that they represent structural aberrations rather than mis-segregated chromosomes. Similar results were obtained in human peripheral lymphocytes following short-term exposure to sodium arsenite or X-rays. Overall, an additive effect was observed for all combined exposures. Cellular radiation responses therefore seem to operate without any modulatory effects from chronic low level exposure to sodium arsenite in the systems analysed here.

Oxidative stress and replication-independent DNA breakage induced by arsenic in Saccharomyces cerevisiae

Arsenic is a well-established human carcinogen of poorly understood mechanism of genotoxicity. It is generally accepted that arsenic acts indirectly by generating oxidative DNA damage that can be converted to replication-dependent DNA double-strand breaks (DSBs), as well as by interfering with DNA repair pathways and DNA methylation. Here we show that in budding yeast arsenic also causes replication and transcription-independent DSBs in all phases of the cell cycle, suggesting a direct genotoxic mode of arsenic action. This is accompanied by DNA damage checkpoint activation resulting in cell cycle delays in S and G2/M phases in wild type cells. In G1 phase, arsenic activates DNA damage response only in the absence of the Yku70-Yku80 complex which normally binds to DNA ends and inhibits resection of DSBs. This strongly indicates that DSBs are produced by arsenic in G1 but DNA ends are protected by Yku70-Yku80 and thus invisible for the checkpoint response. Arsenic-induced DSBs are processed by homologous recombination (HR), as shown by Rfa1 and Rad52 nuclear foci formation and requirement of HR proteins for cell survival during arsenic exposure. We show further that arsenic greatly sensitizes yeast to phleomycin as simultaneous treatment results in profound accumulation of DSBs. Importantly, we observed a similar response in fission yeast Schizosaccharomyces pombe, suggesting that the mechanisms of As(III) genotoxicity may be conserved in other organisms.

Human chorionic gonadotropin β induces migration and invasion via activating ERK1/2 and MMP-2 in human prostate cancer DU145 cells

We previously demonstrated that human chorionic gonadotropin β (hCGβ) induced migration and invasion in human prostate cancer cells. However, the involved molecular mechanisms are unclear. Here, we established a stable prostate cancer cell line overexpressing hCGβ and tested hCGβ-triggered signaling pathways causing cell migration and invasion. ELISA showed that the hCGβ amount secreted into medium increased with culture time after the hCGβ-transfected cells were incubated for 3, 6, 9, 12 and 24 h. More, hCGβ standards promoted MAPK (ERK1/2) phosphorylation and increased MMP-2 expression and activity in both dose- and time-dependent manners in hCGβ non-transfected cells. In addition, hCGβ promoted ERK1/2 phosphorylation and increased MMP-2 expression and activity significantly in hCGβ transfected DU145 cells. Whereas ERK1/2 blocker PD98059 (25 µM) significantly downregulated phosphorylated ERK1/2 and MMP-2. Particularly, hCGβ promoted cell migration and invasion, yet the PD98059 diminished the hCGβ-induced cell motility under those conditions. These results indicated that hCGβ induced cell motility via promoting ERK1/2 phosphorylation and MMP-2 upregulation in human prostate cancer DU145 cells.

Oxidative stress and cancer: an overview

Reactive species, which mainly include reactive oxygen species (ROS), are products generated as a consequence of metabolic reactions in the mitochondria of eukaryotic cells. In normal cells, low-level concentrations of these compounds are required for signal transduction before their elimination. However, cancer cells, which exhibit an accelerated metabolism, demand high ROS concentrations to maintain their high proliferation rate. Different ways of developing ROS resistance include the execution of alternative pathways, which can avoid large amounts of ROS accumulation without compromising the energy demand required by cancer cells. Examples of these processes include the guidance of the glycolytic pathway into the pentose phosphate pathway (PPP) and/or the generation of lactate instead of employing aerobic respiration in the mitochondria. Importantly, ROS levels can be used as a thermostat to monitor the damage that cells can bear. The implications for ROS regulation are highly significant for cancer therapy because commonly used radio- and chemotherapeutic drugs influence tumor outcome through ROS modulation. Moreover, the discovery of novel biomarkers that are able to predict the clinical response to pro-oxidant therapies is a crucial challenge to overcome to allow for the personalization of cancer therapies.

Arsenic trioxide inhibits cell growth and induces apoptosis through inactivation of notch signaling pathway in breast cancer

Arsenic trioxide has been reported to inhibit cell growth and induce apoptotic cell death in many human cancer cells including breast cancer. However, the precise molecular mechanisms underlying the anti-tumor activity of arsenic trioxide are still largely unknown. In the present study, we assessed the effects of arsenic trioxide on cell viability and apoptosis in breast cancer cells. For mechanistic studies, we used multiple cellular and molecular approaches such as MTT assay, apoptosis ELISA assay, gene transfection, RT-PCR, Western blotting, and invasion assays. For the first time, we found a significant reduction in cell viability in arsenic trioxide-treated cells in a dose-dependent manner, which was consistent with induction of apoptosis and also associated with down-regulation of Notch-1 and its target genes. Taken together, our findings provide evidence showing that the down-regulation of Notch-1 by arsenic trioxide could be an effective approach, to cause down-regulation of Bcl-2, and NF-κB, resulting in the inhibition of cell growth and invasion as well as induction of apoptosis. These results suggest that the anti-tumor activity of arsenic trioxide is in part mediated through a novel mechanism involving inactivation of Notch-1 and its target genes. We also suggest that arsenic trioxide could be further developed as a potential therapeutic agent for the treatment of breast cancer.