Synergistic Effects of Arsenic Trioxide and Silibinin on Apoptosis and Invasion in Human Glioblastoma U87MG Cell Line

N-acetylcysteine attenuates sodium arsenite-induced oxidative stress and apoptosis in embryonic fibroblast cells

In recent years, the increase in environmental pollutants has been one of the most important factors threatening human and environmental health. Arsenic, a naturally occurring element found in soil, water, and air, easily enters the human body and leads to many metabolic disorders. In this study, we focused on the possible protective effects of N-acetylcysteine (NAC) against sodium arsenite (As)-induced toxic effects on embryonic fibroblast cells. The effects of As and NAC treatment on cells were evaluated, including cytotoxicity, oxidative stress, and apoptosis. Embryonic fibroblast cells were exposed to As (ranging from 0.01 μM to 10 μM) and NAC (at a concentration of 2 mM) for 24 h. The assessment of cytotoxicity markers, such as cell viability and lactate dehydrogenase (LDH), showed that As significantly reduced cell viability and increased LDH levels. Furthermore, we observed that As increased the amount of reactive oxygen species (ROS) in the cell, decreased the activity of antioxidant enzymes, and triggered apoptosis in cells. Additionally, our research revealed that the administration of NAC mitigates the detrimental effects of As. The results showed that As exerted hazardous effects on embryonic fibroblast cells through the induction of oxidative stress and apoptosis. In this context, our study provides evidence that NAC may have a protective effect against the toxicity of As in embryonic fibroblast cells.

Protective effects of silymarin in glioblastoma cancer cells through redox system regulation

BACKGROUND

Glioblastoma multiforme, a deadly form of brain tumor, is characterized by aggressive growth and poor prognosis. Oxidative stress, a disruption in the balance between antioxidants and oxidants, is a crucial factor in its pathogenesis. Silymarin, a flavonoid extracted from milk thistle, has shown therapeutic potential in inhibiting cancer cell growth, promoting apoptosis, and reducing inflammation. It also regulates oxidative stress. This study aims to investigate the regulatory effects of silymarin on oxidative stress parameters, especially the transcription factor Nrf2 and its related enzymes in GBM cancer cells, to develop a new anti-cancer compound with low toxicity.

METHODS AND RESULTS

First, the cytotoxicity of silymarin on U-87 MG cells was investigated by MTT and the results showed an IC50 of 264.6 μM. Then, some parameters of the redox system were measured with commercial kits, and the obtained results showed that silymarin increased the activity of catalase and superoxide dismutase enzymes, as well as the total antioxidant capacity levels; while the malondialdehyde level that is an indicator of lipid peroxidation was decreased by this compound. The expression level of Nrf2 and HO-1 and glutaredoxin and thioredoxin enzymes were checked by real-time PCR method, and the expression level increased significantly after treatment.

CONCLUSIONS

Our findings suggest that silymarin may exert its cytotoxic and anticancer effects by enhancing the Nrf2/HO-1 pathway through antioxidant mechanisms in U-87 MG cells.

The importance of integrated therapies on cancer: Silibinin, an old and new molecule

In the landscape of cancer treatments, the efficacy of coadjuvant molecules remains a focus of attention for clinical research with the aim of reducing toxicity and achieving better outcomes. Most of the pathogenetic processes causing tumour development, neoplastic progression, ageing, and increased toxicity involve inflammation. Inflammatory mechanisms can progress through a variety of molecular patterns. As is well known, the ageing process is determined by pathological pathways very similar and often parallel to those that cause cancer development. Among these complex mechanisms, inflammation is currently much studied and is often referred to in the geriatric field as 'inflammaging'. In this context, treatments active in the management of inflammatory mechanisms could play a role as adjuvants to standard therapies. Among these emerging molecules, Silibinin has demonstrated its anti-inflammatory properties in different neoplastic types, also in combination with chemotherapeutic agents. Moreover, this molecule could represent a breakthrough in the management of age-related processes. Thus, Silibinin could be a valuable adjuvant to reduce drug-related toxicity and increase therapeutic potential. For this reason, the main aim of this review is to collect and analyse data presented in the literature on the use of Silibinin, to better understand the mechanisms of the functioning of this molecule and its possible therapeutic role.

Silibinin suppresses glioblastoma cell growth, invasion, stemness, and glutamine metabolism by YY1/SLC1A5 pathway

Background

Silibinin has been found to inhibit glioblastoma (GBM) progression. However, the underlying molecular mechanism by which Silibinin regulates GBM process remains unclear.

Methods

GBM cell proliferation, apoptosis, invasion, and stemness are assessed by cell counting kit-8 assay, EdU assay, flow cytometry, transwell assay, and sphere formation assay. Western blot is used to measure the protein expression levels of apoptosis-related markers, solute carrier family 1 member 5 (SLC1A5), and Yin Yang-1 (YY1). Glutamine consumption, glutamate production, and α-ketoglutarate production are detected to evaluate glutamine metabolism in cells. Also, SLC1A5 and YY1 mRNA levels are examined using quantitative real-time PCR. Chromatin immunoprecipitation assay and dual-luciferase reporter assay are used to detect the interaction between YY1 and SLC1A5. Mice xenograft models are constructed to explore Silibinin roles in vivo.

Results

Silibinin inhibits GBM cell proliferation, invasion, stemness, and glutamine metabolism, while promotes apoptosis. SLC1A5 is upregulated in GBM and its expression is decreased by Silibinin. SLC1A5 overexpression abolishes the anti-tumor effect of Silibinin in GBM cells. Transcription factor YY1 binds to SLC1A5 promoter region to induce SLC1A5 expression, and the inhibition effect of YY1 knockdown on GBM cell growth, invasion, stemness, and glutamine metabolism can be reversed by SLC1A5 overexpression. In addition, Silibinin reduces GBM tumor growth by regulating YY1/SLC1A5 pathway.

Conclusion

Silibinin plays an anti-tumor role in GBM process, which may be achieved via inhibiting YY1/SLC1A5 pathway.

Protective effects of macromolecular polyphenols, metals (zinc, selenium, and copper) - Polyphenol complexes, and different organs with an emphasis on arsenic poisoning: A review

For the potential health benefits and nutritional value, polyphenols are one of the secondary metabolites of plants that have received extensive research. It has anti-inflammatory and cytotoxicity-reducing properties in addition to a high antioxidant content. Macromolecular polyphenols and polysaccharides are biologically active natural polymers with antioxidant and anti-inflammatory potential. Arsenic is an ecologically toxic metalloid. Arsenic in drinking water is the most common way people come into contact with this metalloid. While arsenic is known to cause cancer, it is also used to treat acute promyelocytic leukemia (APL). The treatment's effectiveness is hampered by the adverse effects it can cause on the body. Oxidative stress, inflammation, and the inability to regulate cell death cause the most adverse effects. Polyphenols and other macromolecules like polysaccharides act as neuroprotectants by mitigating free radical damage, inhibiting nitric oxide (NO) production, lowering A42 fibril formation, boosting antioxidant levels, and controlling apoptosis and inflammation. To prevent the harmful effects of toxins, polyphenols and pectin lower oxidative stress, boost antioxidant levels, improve mitochondrial function, control apoptosis, and suppress inflammation. Therefore, it prevents damage to the heart, liver, kidneys, and reproductive system. This review aims to identify the effects of the polyphenols in conjugation with polysaccharides as an ameliorative strategy for arsenic-induced toxicity in various organs.

Anticancer Mechanism of Flavonoids on High-Grade Adult-Type Diffuse Gliomas

High-grade adult-type diffuse gliomas are the most common and deadliest malignant adult tumors of the central nervous system. Despite the advancements in the multimodality treatment of high-grade adult-type diffuse gliomas, the five-year survival rates still remain poor. The biggest challenge in treating high-grade adult-type diffuse gliomas is the intra-tumor heterogeneity feature of the glioma tumors. Introducing dietary flavonoids to the current high-grade adult-type diffuse glioma treatment strategies is crucial to overcome this challenge, as flavonoids can target several molecular targets. This review discusses the anticancer mechanism of flavonoids (quercetin, rutin, chrysin, apigenin, naringenin, silibinin, EGCG, genistein, biochanin A and C3G) through targeting molecules associated with high-grade adult-type diffuse glioma cell proliferation, apoptosis, oxidative stress, cell cycle arrest, migration, invasion, autophagy and DNA repair. In addition, the common molecules targeted by the flavonoids such as Bax, Bcl-2, MMP-2, MMP-9, caspase-8, caspase-3, p53, p38, Erk, JNK, p38, beclin-1 and LC3B were also discussed. Moreover, the clinical relevance of flavonoid molecular targets in high-grade adult-type diffuse gliomas is discussed with comparison to small molecules inhibitors: ralimetinib, AMG232, marimastat, hydroxychloroquine and chloroquine. Despite the positive pre-clinical results, further investigations in clinical studies are warranted to substantiate the efficacy and safety of the use of flavonoids on high-grade adult-type diffuse glioma patients.

Natural Products Targeting Hsp90 for a Concurrent Strategy in Glioblastoma and Neurodegeneration

Glioblastoma multiforme (GBM) is one of the most common aggressive, resistant, and invasive primary brain tumors that share neurodegenerative actions, resembling many neurodegenerative diseases. Although multiple conventional approaches, including chemoradiation, are more frequent in GBM therapy, these approaches are ineffective in extending the mean survival rate and are associated with various side effects, including neurodegeneration. This review proposes an alternative strategy for managing GBM and neurodegeneration by targeting heat shock protein 90 (Hsp90). Hsp90 is a well-known molecular chaperone that plays essential roles in maintaining and stabilizing protein folding to degradation in protein homeostasis and modulates signaling in cancer and neurodegeneration by regulating many client protein substrates. The therapeutic benefits of Hsp90 inhibition are well-known for several malignancies, and recent evidence highlights that Hsp90 inhibitors potentially inhibit the aggressiveness of GBM, increasing the sensitivity of conventional treatment and providing neuroprotection in various neurodegenerative diseases. Herein, the overview of Hsp90 modulation in GBM and neurodegeneration progress has been discussed with a summary of recent outcomes on Hsp90 inhibition in various GBM models and neurodegeneration. Particular emphasis is also given to natural Hsp90 inhibitors that have been evidenced to show dual protection in both GBM and neurodegeneration.

Honokiol attenuate the arsenic trioxide-induced cardiotoxicity by reducing the myocardial apoptosis

Despite advantages of arsenic trioxide (ATO) in oncological practice, its clinical applications have been hampered by severe cardiotoxicity. The general mechanism of ATO-induced cardiotoxicity has been attributed to its damage to mitochondria, resulting in cardiac remodeling. Honokiol (HKL) is a naturally occurring compound derived from Magnolia bark. Previous studies have demonstrated that HKL exerts cardio-protective effects on ischemia/reperfusion (I/R) or chemical-induced cardiotoxicity by counteracting the toxic effects on mitochondria. The present study was conducted to investigate whether HKL pretreatment protects against ATO-induced cardiac oxidative damage and cell death. For the in vitro study, we evaluated the effects of ATO and/or Honokiol on reactive oxygen species (ROS) production and apoptosis induction in primary cultured cardiomyocytes; for the in vivo study, BALB/c mice were administrated with ATO and/or HKL for a period of 4 weeks, myocardial apoptosis, cardiac function, and cardiac remodeling (cardiac hypertrophy and cardiac fibrosis) were assessed at the end of administration. Our results demonstrated Honokiol pretreatment alleviated the ATO-induced boost in ROS concentration and the following apoptosis induction in primary cultured cardiomyocytes. In the mouse model, Honokiol pretreatment ameliorated ATO-induced myocardial apoptosis, cardiac dysfunction, and cardiac remodeling. Collectively, these results indicated that Honokiol provide a protection against ATO-induced cardiotoxicity by reducing mitochondrial damage. In addition, given that Honokiol has shown considerable suppressive effects on leukemia cells, our data also imply that ATO and Honokiol combination may possibly be a superior avenue in leukemia therapy.

Current Advances of Nanomedicines Delivering Arsenic Trioxide for Enhanced Tumor Therapy

Arsenic trioxide (ATO) is one of the first-line chemotherapeutic drugs for acute promyelocytic leukemia. Its anti-cancer activities against various human neoplastic diseases have been extensively studied. However, the clinical use of ATO for solid tumors is limited, and these limitations are because of severe systemic toxicity, low bioavailability, and quick renal elimination before it reaches the target site. Although without much success, several efforts have been made to boost ATO bioavailability toward solid tumors without raising its dose. It has been found that nanomedicines have various advantages for drug delivery, including increased bioavailability, effectiveness, dose-response, targeting capabilities, and safety as compared to traditional drugs. Therefore, nanotechnology to deliver ATO to solid tumors is the main topic of this review, which outlines the previous and present medical applications of ATO. We also summarised ATO anti-cancer mechanisms, limitations, and outcomes of combinatorial treatment with chemo agents. As a result, we strongly recommend conducting pre-clinical and clinical studies of ATO, especially nano-system-based ones that might lead to a novel combination therapy for cancer treatment with high efficacy, bioavailability, and low toxicity for cancer patients.

Neuroimmunomodulatory Properties of Flavonoids and Derivates: A Potential Action as Adjuvants for the Treatment of Glioblastoma

Glioblastomas (GBMs) are tumors that have a high ability to migrate, invade and proliferate in the healthy tissue, what greatly impairs their treatment. These characteristics are associated with the complex microenvironment, formed by the perivascular niche, which is also composed of several stromal cells including astrocytes, microglia, fibroblasts, pericytes and endothelial cells, supporting tumor progression. Further microglia and macrophages associated with GBMs infiltrate the tumor. These innate immune cells are meant to participate in tumor surveillance and eradication, but they become compromised by GBM cells and exploited in the process. In this review we discuss the context of the GBM microenvironment together with the actions of flavonoids, which have attracted scientific attention due to their pharmacological properties as possible anti-tumor agents. Flavonoids act on a variety of signaling pathways, counteracting the invasion process. Luteolin and rutin inhibit NFκB activation, reducing IL-6 production. Fisetin promotes tumor apoptosis, while inhibiting ADAM expression, reducing invasion. Naringenin reduces tumor invasion by down-regulating metalloproteinases expression. Apigenin and rutin induce apoptosis in C6 cells increasing TNFα, while decreasing IL-10 production, denoting a shift from the immunosuppressive Th2 to the Th1 profile. Overall, flavonoids should be further exploited for glioma therapy.

Flavonoids Synergistically Enhance the Anti-Glioblastoma Effects of Chemotherapeutic Drugs

Flavonoids are polyphenolic plant secondary metabolites with pleiotropic biological properties, including anti-cancer activities. These natural compounds have potential utility in glioblastoma (GBM), a malignant central nervous system tumor derived from astrocytes. Conventional GBM treatment modalities such as chemotherapy, radiation therapy, and surgical tumor resection are beneficial but limited by extensive tumor invasion and drug/radiation resistance. Therefore, dietary flavonoids—with demonstrated anti-GBM properties in preclinical research—are potential alternative therapies. This review explores the synergistic enhancement of the anti-GBM effects of conventional chemotherapeutic drugs by flavonoids. Primary studies published between 2011 and 2021 on flavonoid–chemotherapeutic synergy in GBM were obtained from PubMed. These studies demonstrate that flavonoids such as chrysin, epigallocatechin-3-gallate (EGCG), formononetin, hispidulin, icariin, quercetin, rutin, and silibinin synergistically enhance the effects of canonical chemotherapeutics. These beneficial effects are mediated by the modulation of intracellular signaling mechanisms related to apoptosis, proliferation, autophagy, motility, and chemoresistance. In this light, flavonoids hold promise in improving current therapeutic strategies and ultimately overcoming GBM drug resistance. However, despite positive preclinical results, further investigations are necessary before the commencement of clinical trials. Key considerations include the bioavailability, blood–brain barrier (BBB) permeability, and safety of flavonoids; optimal dosages of flavonoids and chemotherapeutics; drug delivery platforms; and the potential for adverse interactions.

Improvement of cytotoxicity of mitoxantrone and daunorubicin by candidone, tephrosin, and bavachinin

BACKGROUND

Flavonoids have been demonstrated to have the ability of sensitizing cancer cells to chemotherapy and inverse multidrug resistance via various mechanisms, such as modulating of pumps. The therapeutic effect of candidone, tephrosin, and bavachinin in treatment of cancer, particularly to overcome multidrug resistance (MDR) is largely unknown. The capacity of these agents in sensitization of MDR cells is investigated in the current work.

METHODS AND RESULTS

We analyzed the impact of candidone, tephrosin, and bavachinin, as chemosensitizer on cell cytotoxicity, P-gp and ABCG2 mRNA expression level on two multidrug resistant cells, ABCG2 overexpressing human epithelial breast cancer cell line (MCF7/MX), and P-gp overexpressing human gastric adenocarcinoma cell line (EPG85.257RDB). The inhibitory concentration of 50% (IC50) of daunorubicin in EPG85.257RDB cells in combination with IC10 of Bavachinin, Tephrosin, and Candidone were 6159 ± 948, 4186 ± 665, 730 ± 258 nM, and this data in MCF7/MX cell were 1773 ± 534, 7160 ± 405 and 3340 ± 622 nM respectively. These three flavonoids dose-dependently decreased the viability of MCF7/MX and EPG85.257RDB and significantly (p < 0.05) decreased IC50 of daunorubicin and mitoxantrone except Tephrosin in MCF7/MX cells. Candidone and Bavachinin were the most potent chemosensitizer in EPG85.257RDB and MCF7/MX cells respectively. Flavonoids did not reduce mRNA expression of P-gp and ABCG2 after 72 h treatment, except Candidone in EPG85.257RDB and Bavachinin in MCF7/MX cells.

CONCLUSIONS

This effect is not time-dependent, and flavonoids have their own patterns that are cell-dependent. In general, tephrosin, candidone, and bavachinin had the potential of sensitizing MDR cells to mitoxantrone and daunorubicin.

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.

Silymarin and Cancer: A Dual Strategy in Both in Chemoprevention and Chemosensitivity

Silymarin extracted from milk thistle consisting of flavonolignan silybin has shown chemopreventive and chemosensitizing activity against various cancers. The present review summarizes the current knowledge on the potential targets of silymarin against various cancers. Silymarin may play on the system of xenobiotics, metabolizing enzymes (phase I and phase II) to protect normal cells against various toxic molecules or to protect against deleterious effects of chemotherapeutic agents on normal cells. Furthermore, silymarin and its main bioactive compounds inhibit organic anion transporters (OAT) and ATP-binding cassettes (ABC) transporters, thus contributing to counteracting potential chemoresistance. Silymarin and its derivatives play a double role, namely, limiting the progression of cancer cells through different phases of the cycle-thus forcing them to evolve towards a process of cell death-and accumulating cancer cells in a phase of the cell cycle-thus making it possible to target a greater number of tumor cells with a specific anticancer agent. Silymarin exerts a chemopreventive effect by inducing intrinsic and extrinsic pathways and reactivating cell death pathways by modulation of the ratio of proapoptotic/antiapoptotic proteins and synergizing with agonists of death domains receptors. In summary, we highlight how silymarin may act as a chemopreventive agent and a chemosensitizer through multiple pathways.

Enhancing the Therapeutic Efficacy of Daunorubicin and Mitoxantrone with Bavachinin, Candidone, and Tephrosin

The capability of flavonoids in sensitizing cancer cells was demonstrated in numerous works to chemotherapy and converse multidrug resistance by modulating efflux pumps and apoptosis mechanisms. Three flavonoids, namely, bavachinin, tephrosin, and candidone, have been recently introduced to cancer treatment research presenting various activities, such as antibacterial, immunomodulatory, cell death, and anticancer. Less information exists regarding the therapeutic significance of these flavonoids in cancer treatment, especially in overcoming multidrug resistance (MDR). Here, we tempted to investigate the potency of these agents in reversing MDR by analyzing their effects as chemosensitizers on cell cytotoxicity, P-gp and ABCG2 protein expression levels, and their function on two multidrug-resistant cell lines, P-gp-overexpressing human gastric adenocarcinoma cell line (EPG85.257RDB) and ABCG2-overexpressing human epithelial breast cancer cell line (MCF7/MX). The inhibitory concentration of 10% (IC₁₀) of bavachinin, tephrosin, and candidone in EPG85.257RDB cells was 1588.7 ± 202.2, 264.8 ± 86.15, and 1338.6 ± 114.11 nM, respectively. Moreover, these values in MCF7/MX cell were 2406.4 ± 257.63, 38.8 ± 4.28, and 27.9 ± 5.59 nM, respectively. Expression levels of ABCG2 and P-gp were not significantly downregulated by these flavonoids. Maximum levels of daunorubicin and mitoxantrone accumulations and minimum rates of drug efflux in both cell lines were detected 48 hrs posttreatment with tephrosin and bavachinin, respectively. Chemosensitization to mitoxantrone and daunorubicin treatments was, respectively, achieved in MCF7/MX and EPG85.257RDB cells in response to IC₁₀ of bavachinin and tephrosin, independently. These effects did not follow time-dependent manner, and each flavonoid had its cell-dependent patterns. Overall, bavachinin, tephrosin, and candidone showed potency to sensitize MDR cells to daunorubicin and mitoxantrone and could be considered as attractive MDR modulators for cancer treatment. However, their action was time and cell specific.

Blockade of JAK2/STAT3 intensifies the anti-tumor activity of arsenic trioxide in acute myeloid leukemia cells: Novel synergistic mechanism via the mediation of reactive oxygen species

Reactive oxygen species (ROS) are essential mediators of crucial cellular processes including apoptosis, proliferation, survival and cell cycle. Their regulatory role in cancer progression has seen in different human malignancies such as acute myeloid leukemia (AML). AML patients suffer from high resistance of the tumors against routine therapeutics including ATO. ATO enhance reactive oxygen species levels and induce apoptosis and suppresses proliferation in AML cells. However, some pathways such as JAK2/STAT3 ease anti-tumor activity of ATO by reducing reactive oxygen species amount and protecting the cell from apoptosis. In the present study, we use ruxolitinib (potent JAK2 inhibitor) to increase the sensitivity of AML cells to ATO treatment. We test, the effect of this combination on metabolic activity, proliferation, colony formation, cell cycle distribution, apoptosis, oxidative stress and DNA damage. Our results showed that combination of ATO with ruxolitinib synergistically reduced metabolic activity, proliferation and survival of AML cell lines. This combination induced G1/S cell cycle arrest because of reactive oxygen species elevation and GSH reduction. Besides, enhancement of reactive oxygen species increased apoptosis rate in combination samples. We uncovered that the synergistic anti-tumor effect of ATO and ruxolitinib in AML cells mediates via reactive oxygen species elevation and DNA damage. Overall, our results show that the combinatorial therapy of AML cells is more effective than solo-targeted therapy.

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.

Chrysin and silibinin sensitize human glioblastoma cells for arsenic trioxide

Arsenic trioxide (ATO) is highly efficient in treating acute promyelocytic leukemia. Other malignancies, however, are often less sensitive. Searching for compounds sensitizing arsenic resistant tumours for ATO the plant polyphenols, chrysin and silibinin, and the ATP binding cassette (ABC) transporter inhibitor MK-571, respectively, were investigated in human glioblastoma A-172 cells. The sensitivity of A-172 cells to ATO was characterized by a median cytotoxic concentration of 6 μM ATO. Subcytotoxic concentrations of chrysin, silibinin and MK-571, respectively, remarkably increased the sensitivity of the cells to ATO by factors of 4-6. Isobolographic analysis revealed synergistic interaction of the polyphenols and MK-571, respectively, with ATO. Sensitization by chrysin was associated with depletion of cellular glutathione and increased accumulation of arsenic. In contrast, silibinin and also MK-571 increased the accumulation of arsenic more strongly but without affecting the glutathione level. The increase of arsenic accumulation could be attributed to a decreased rate of arsenic export and, additionally, in the case of silibinin and MK-571, to an increasing amount of irreversibly accumulated arsenic. Direct interaction with ABC transporters stimulating export of glutathione and inhibiting export of arsenic, respectively, are discussed as likely mechanisms of the sensitizing activity of chrysin and silibinin.

Demethylation and alterations in the expression level of the cell cycle-related genes as possible mechanisms in arsenic trioxide-induced cell cycle arrest in human breast cancer cells

Arsenic trioxide (As₂O₃) has been used clinically as an anti-tumor agent. Its mechanisms are mostly considered to be the induction of apoptosis and cell cycle arrest. However, the detailed molecular mechanisms of its anti-cancer action through cell cycle arrest are poorly known. Furthermore, As₂O₃ has been shown to be a potential DNA methylation inhibitor, inducing DNA hypomethylation. We hypothesize that As₂O₃ may affect the expression of cell cycle regulatory genes by interfering with DNA methylation patterns. To explore this, we examined promoter methylation status of 24 cell cycle genes in breast cancer cell lines and in a normal breast tissue sample by methylation-specific polymerase chain reaction and/or restriction enzyme-based methods. Gene expression level and cell cycle distribution were quantified by real-time polymerase chain reaction and flow cytometric analyses, respectively. Our methylation analysis indicates that only promoters of RBL1 (p107), RASSF1A, and cyclin D2 were aberrantly methylated in studied breast cancer cell lines. As₂O₃ induced CpG island demethylation in promoter regions of these genes and restores their expression correlated with DNA methyltransferase inhibition. As₂O₃ also induced alterations in messenger RNA expression of several cell cycle-related genes independent of demethylation. Flow cytometric analysis revealed that the cell cycle arrest induced by As₂O₃ varied depending on cell lines, MCF-7 at G1 phase and both MDA-MB-231 and MDA-MB-468 cells at G2/M phase. These changes at transcriptional level of the cell cycle genes by the molecular mechanisms dependent and independent of demethylation are likely to represent the mechanisms of cell cycle redistribution in breast cancer cells, in response to As₂O₃ treatment.

Targeting Glioblastoma with the Use of Phytocompounds and Nanoparticles

Glioblastoma multiforme (GBM) are extremely lethal and still poorly treated primary brain tumors, characterized by the presence of highly tumorigenic cancer stem cell (CSC) subpopulations, considered responsible for tumor relapse. In order to successfully eradicate GBM growth and recurrence, new anti-cancer strategies selectively targeting CSCs should be designed. CSCs might be eradicated by targeting some of their cell surface markers and transporters, inducing their differentiation, impacting their hyper-glycolytic metabolism, inhibiting CSC-related signaling pathways and/or by targeting their microenvironmental niche. In this regard, phytocompounds such as curcumin, isothiocyanates, resveratrol and epigallocatechin-3-gallate have been shown to prevent or reverse cancer-related epigenetic dysfunctions, reducing tumorigenesis, preventing metastasis and/or increasing chemotherapy and radiotherapy efficacy. However, the actual bioavailability and metabolic processing of phytocompounds is generally unknown, and the presence of the blood brain barrier often represents a limitation to glioma treatments. Nowadays, nanoparticles (NPs) can be loaded with therapeutic compounds such as phytochemicals, improving their bioavailability and their targeted delivery within the GBM tumor bulk. Moreover, NPs can be designed to increase their tropism and specificity toward CSCs by conjugating their surface with antibodies specific for CSC antigens, with ligands or with glucose analogues. Here we discuss the use of phytochemicals as anti-glioma agents and the applicability of phytochemical-loaded NPs as drug delivery systems to target GBM. Additionally, we provide some examples on how NPs can be specifically formulated to improve CSC targeting.

SurvivinT34A increases the therapeutic efficacy of arsenic trioxide in mouse hepatocellular carcinoma models

Arsenic trioxide (ATO) has demonstrated clinical efficacy in acute promyelocytic leukemia (APL) and in vitro activity in various solid tumors. As2O3 as single agent exhibits poor efficacy for treatment of hepatocellular carcinoma (HCC) in phase II trial, suggesting that new modalities of treatment with enhanced therapeutic effect and alleviated toxicity are needed for application of As2O3 on patients with HCC. Survivin is the strongest inhibitor of apoptosis protein over-expressed in tumors, which has been proposed as an attractive target for new anticancer interventions. Disruption of survivin by the plasmid encoding the phosphorylation-defective mouse survivin threonine 34→alanine mutant (Msurvivin T34A plasmid) has proved a promising strategy for suppressing a variety of murine cancer. In the present study, we attempted to test Msurvivin T34A and arsenic trioxide (ATO) on a cell line and mice bearing subcutaneous tumors, with regard to their effects and mechanisms. We observed that the co-treatment with surivinT34A and ATO significantly enhanced the antitumor activity by induction of apoptosis in Hepa1-6 tumor cells in vitro, compared with control groups. The synergistic apoptosis-inducing effect of combination of these two drugs resulted in elevation of reactive oxygen species (ROS) level which could be antagonized by the antioxidant N-acetyl-l-cysteine. The combination treatment induced ROS-dependent collapse of the mitochondrial membrane potential. Moreover, the tumor growth in vivo was also remarkably inhibited by combination of surivinT34A and ATO when compared with control groups. Our findings demonstrate that the combination of surivinT34A and ATO exerted synergistic antitumor effects, providing a new perspective for clinical treatment of HCC.

Silibinin-induced glioma cell apoptosis by PI3K-mediated but Akt-independent downregulation of FoxM1 expression

The oncogenic transcription factor Forkhead box M1 (FoxM1) is overexpressed in many human tumors, including glioma. As a critical regulator of the cell cycle and apoptosis-related genes, FoxM1 is a potential therapeutic target against human malignant glioma. Silibinin, a flavonoid isolated from Silybum marianum, dose-dependently reduced glioma cell proliferation, promoted apoptosis, and downregulated FoxM1 expression. Knockdown of FoxM1 by small hairpin RNA (shRNA) transfection also promoted glioma cell apoptosis and augmented the antiproliferative and pro-apoptotic properties of silibinin. Moreover, silibinin increased caspase-3 activation, upregulated pro-apoptotic Bax, and suppressed anti-apoptotic Bcl-2 expression, effects enhanced by FoxM1 knockdown. Silibinin treatment suppressed U87 cell PI3K phospho-activation, and simultaneous silibinin exposure, FoxM1 knockdown, and PI3K inhibition additively increased U87 cell apoptosis. Furthermore, PI3K inhibition reduced FoxM1 expression. Akt activity was also suppressed by FoxM1 downregulation but Akt inhibition did not alter FoxM1 expression. Thus, silibinin likely inhibited glioma cell proliferation and induced apoptosis through inactivation of PI3K and FoxM1, leading to activation of the mitochondrial apoptotic pathway. FoxM1 may be a novel target for chemotherapy against human glioma.

CRM197 in Combination With shRNA Interference of VCAM-1 Displays Enhanced Inhibitory Effects on Human Glioblastoma Cells

CRM197 is a naturally nontoxic diphtheria toxin mutant that binds and inhibits heparin-binding epidermal growth factor-like growth factor. CRM197 serves as carrier protein for vaccine and other therapeutic agents. CRM197 also inhibits the growth, migration, invasion, and induces apoptosis in various tumors. Vascular cell adhesion molecule-1 (VCAM-1) is an important cell surface adhesion molecule associated with malignancy of gliomas. In this work, we aimed to investigate the role and mechanism of CRM197 combined with shRNA interference of VCAM-1 (shRNA-VCAM-1) on the migration, invasion, and apoptosis of glioblastoma cells. U87 and U251 human glioblastoma cells were treated with CRM197 (10 µg/ml) and shRNA interfering technology was employed to silence VCAM-1 expression. Cell viability, migration, invasiveness, and apoptosis were assessed with CCK8, Transwell and Annexin V-PE/7-AAD staining. Activation of cleaved caspase-3, 8, and 9, activity of matrix metalloproteinase-2/9 (MMP-2/9), and expression of phosphorylated Akt (p-Akt) were also checked. Results showed that CRM197 and shRNA-VCAM-1 not only significantly inhibited the cell proliferation, migration, invasion, but also promoted the apoptosis of U87 and U251 cells. Combined treatment of both displayed enhanced inhibitory effects on the malignant biological behavior of glioma cells. The activation of cleaved caspase-3, 8, 9 was promoted, activity of MMP-2 and MMP-9 and expression of p-Akt were inhibited significantly by the treatment of CRM197 and shRNA-VCAM-1 alone or in combination, indicating that the combination of CRM197 with shRNA-VCAM-1 additively inhibited the malignant behavior of human glioblastoma cells via activating caspase-3, 8, 9 as well as inhibiting MMP-2, MMP-9, and Akt pathway.

Promyelocytic leukemia protein induces arsenic trioxide resistance through regulation of aldehyde dehydrogenase 3 family member A1 in hepatocellular carcinoma

Clinical response of hepatocellular carcinoma (HCC) to arsenic trioxide (ATO) has been poor. Promyelocytic leukemia protein (PML) is central to ATO treatment efficacy of acute promyelocytic leukemia. We examine impacts of PML expression on the effectiveness of ATO treatment in HCC. We show that increased PML expression predicts longer survival and lower cancer recurrence rates after HCC resection. However, high PML expression dampens the anti-tumor effects of ATO in HCC cells. Gene microarray analysis shows that reduced PML expression significantly down-regulates expression of aldehyde dehydrogenase 3 family member A1 (ALDH3A1). ALDH3A1 depression facilitates accumulation of ATO-induced reactive oxygen species. Chromatin immunoprecipitation analysis and promoter activity assays confirm that PML regulates ALDH3A1 expression through binding to the promoter region of ALDH3A1. Clinically, ATO treatment decreases the disease progression rate in advanced HCC patients with negative PML expression. In conclusion, PML confers a favorable prognosis in HCC patients, but it induces ATO resistance through ALDH3A1 up-regulation in HCC cells. ATO is effective for HCC patients with negative PML expression. Combined with an ALDH3A1 inhibitor, ATO may be efficacious in patients with positive PML expression.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

Broad targeting of angiogenesis for cancer prevention and therapy

Deregulation of angiogenesis – the growth of new blood vessels from an existing vasculature – is a main driving force in many severe human diseases including cancer. As such, tumor angiogenesis is important for delivering oxygen and nutrients to growing tumors, and therefore considered an essential pathologic feature of cancer, while also playing a key role in enabling other aspects of tumor pathology such as metabolic deregulation and tumor dissemination/metastasis. Recently, inhibition of tumor angiogenesis has become a clinical anti-cancer strategy in line with chemotherapy, radiotherapy and surgery, which underscore the critical importance of the angiogenic switch during early tumor development. Unfortunately the clinically approved anti-angiogenic drugs in use today are only effective in a subset of the patients, and many who initially respond develop resistance over time. Also, some of the anti-angiogenic drugs are toxic and it would be of great importance to identify alternative compounds, which could overcome these drawbacks and limitations of the currently available therapy. Finding “the most important target” may, however, prove a very challenging approach as the tumor environment is highly diverse, consisting of many different cell types, all of which may contribute to tumor angiogenesis. Furthermore, the tumor cells themselves are genetically unstable, leading to a progressive increase in the number of different angiogenic factors produced as the cancer progresses to advanced stages. As an alternative approach to targeted therapy, options to broadly interfere with angiogenic signals by a mixture of non-toxic natural compound with pleiotropic actions were viewed by this team as an opportunity to develop a complementary anti-angiogenesis treatment option. As a part of the “Halifax Project” within the “Getting to know cancer” framework, we have here, based on a thorough review of the literature, identified 10 important aspects of tumor angiogenesis and the pathological tumor vasculature which would be well suited as targets for anti-angiogenic therapy: (1) endothelial cell migration/tip cell formation, (2) structural abnormalities of tumor vessels, (3) hypoxia, (4) lymphangiogenesis, (5) elevated interstitial fluid pressure, (6) poor perfusion, (7) disrupted circadian rhythms, (8) tumor promoting inflammation, (9) tumor promoting fibroblasts and (10) tumor cell metabolism/acidosis. Following this analysis, we scrutinized the available literature on broadly acting anti-angiogenic natural products, with a focus on finding qualitative information on phytochemicals which could inhibit these targets and came up with 10 prototypical phytochemical compounds: (1) oleanolic acid, (2) tripterine, (3) silibinin, (4) curcumin, (5) epigallocatechin-gallate, (6) kaempferol, (7) melatonin, (8) enterolactone, (9) withaferin A and (10) resveratrol. We suggest that these plant-derived compounds could be combined to constitute a broader acting and more effective inhibitory cocktail at doses that would not be likely to cause excessive toxicity. All the targets and phytochemical approaches were further cross-validated against their effects on other essential tumorigenic pathways (based on the “hallmarks” of cancer) in order to discover possible synergies or potentially harmful interactions, and were found to generally also have positive involvement in/effects on these other aspects of tumor biology. The aim is that this discussion could lead to the selection of combinations of such anti-angiogenic compounds which could be used in potent anti-tumor cocktails, for enhanced therapeutic efficacy, reduced toxicity and circumvention of single-agent anti-angiogenic resistance, as well as for possible use in primary or secondary cancer prevention strategies.

KML001, a telomere-targeting drug, sensitizes glioblastoma cells to temozolomide chemotherapy and radiotherapy through DNA damage and apoptosis

Standard treatment for glioblastoma comprises surgical resection, chemotherapy with temozolomide, and radiotherapy. Nevertheless, majority of glioblastoma patients have recurrence from resistance to the cytotoxic conventional therapies. We examined combinational effects of KML001, an arsenic compound targeting telomeres of chromosomes with temozolomide or irradiation, in glioblastoma cell lines and xenograft models, to overcome the therapeutic limitation of chemoradiation therapy for glioblastoma. Although KML001 alone showed little effects on in vitro survival of glioblastoma cells, cell death by in vitro temozolomide treatment or irradiation was synergistically potentiated by combination with KML001. Since phosphorylated γ-H2AX, cleaved casepase-3, and cleaved PARP were dramatically increased by KML001, the synergistic effects would be mediated by increased DNA damage and subsequent tumor cell apoptosis. Combinatorial effects of KML001 were observed not only in chemo- and radiosensitive glioblastoma cell line, U87MG, but also in the resistant cell line, U251MG. In the U87MG glioblastoma xenograft models, KML001 did not have systemic toxicity but showed synergistic therapeutic effects in combination with temozolomide or irradiation to reduce tumor volumes significantly. These data indicated that KML001 could be a candidate sensitizer to potentiate therapeutic effects of conventional cytotoxic treatment for glioblastoma.

Autophagy interplays with apoptosis and cell cycle regulation in the growth inhibiting effect of Trisenox in HEP-2, a laryngeal squamous cancer

Laryngeal squamous cell carcinoma (LSCC) is the most common among several types of head and neck cancers. Current treatments have a poor effect on early and advanced cases, and further investigations for novel agents against LSCCs are desirable. In this study, we elucidate the cytotoxic enhancing effect of arsenic trioxide (As2O3) combined with L-buthionine sulfoximine (BSO) in LSCC. The effect of BSO with As2O3 or Cisplatin (CDDP) on cell viability was examined using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The reactive oxygen species (ROS) levels, cell cycle, and apoptosis were measured by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), propidium iodide (PI) and annexin V/PI. The acidic vacuolar organelles were visualized by fluorescence microscope and quantified using flow cytometry. Neither CDDP nor As2O3 when used alone reduced the cell viability. BSO was found to enhance only As2O3 sensitivity, leading to G2/M arrest and autophagy with no correlation of ROS induction. This result suggests that modulation of glutathione enhances autophagy, which interplays with apoptosis. In this study, we obtained initial preclinical evidence for the potential efficacy of these drugs in a combined therapy protocol.

The natural flavonoid silybin improves the response to Photodynamic Therapy of bladder cancer cells

Photodynamic Therapy (PDT) is an anticancer treatment based on photosensitisation of malignant cells. The precursor of the photosensitiser Protoporphyrin IX, 5-aminolevulinic acid (ALA), has been used for PDT of bladder cancer. Silybin is a flavonoid extracted from Silybum marianum, and it has been reported to increase the efficacy of several anticancer treatments. In the present work, we evaluated the cytotoxicity of the combination of ALA-PDT and silybin in the T24 and MB49 bladder cancer cell lines. MB49 cells were more sensitive to PDT damage, which was correlated with a higher Protoporphyrin IX production from ALA. Employing lethal light doses 50% (LD50) and 75% (LD75) and additional silybin treatment, there was a further increase of toxicity driven by PDT in both cell lines. Using the Chou-Talalay model for drug combination derived from the mass-action law principle, it was possible to identify the effect of the combination as synergic when using LD75, whilst the use of LD50 led to an additive effect on MB49 cells. On the other hand, the drug combination turned out to be nearly additive on T24 cells. Apoptotic cell death is involved both in silybin and PDT cytotoxicity in the MB49 line but there is no apparent correlation with the additive or synergic effect observed on cell viability. On the other hand, we found an enhancement of the PDT-driven impairment of cell migration on both cell lines as a consequence of silybin treatment. Overall, our results suggest that the combination of silybin and ALA-PDT would increase PDT outcome, leading to additive or synergistic effects and possibly impairing the occurrence of metastases.

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.

Silybin-mediated inhibition of Notch signaling exerts antitumor activity in human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a global health burden that is associated with limited treatment options and poor patient prognoses. Silybin (SIL), an antioxidant derived from the milk thistle plant (Silybum marianum), has been reported to exert hepatoprotective and antitumorigenic effects both in vitro and in vivo. While SIL has been shown to have potent antitumor activity against various types of cancer, including HCC, the molecular mechanisms underlying the effects of SIL remain largely unknown. The Notch signaling pathway plays crucial roles in tumorigenesis and immune development. In the present study, we assessed the antitumor activity of SIL in human HCC HepG2 cells in vitro and in vivo and explored the roles of the Notch pathway and of the apoptosis-related signaling pathway on the activity of SIL. SIL treatment resulted in a dose- and time-dependent inhibition of HCC cell viability. Additionally, SIL exhibited strong antitumor activity, as evidenced not only by reductions in tumor cell adhesion, migration, intracellular glutathione (GSH) levels and total antioxidant capability (T-AOC) but also by increases in the apoptotic index, caspase3 activity, and reactive oxygen species (ROS). Furthermore, SIL treatment decreased the expression of the Notch1 intracellular domain (NICD), RBP-Jκ, and Hes1 proteins, upregulated the apoptosis pathway-related protein Bax, and downregulated Bcl2, survivin, and cyclin D1. Notch1 siRNA (in vitro) or DAPT (a known Notch1 inhibitor, in vivo) further enhanced the antitumor activity of SIL, and recombinant Jagged1 protein (a known Notch ligand in vitro) attenuated the antitumor activity of SIL. Taken together, these data indicate that SIL is a potent inhibitor of HCC cell growth that targets the Notch signaling pathway and suggest that the inhibition of Notch signaling may be a novel therapeutic intervention for HCC.

Differential sensitivity of p44/p42-MAPK- and PI3K/Akt-targeted neuroblastoma subtypes to arsenic trioxide

PI3K/Akt and MAPK/ERK pathways are differentially activated in neuroblastoma (NB) cell types. In an effort to enhance the effectiveness of the NB treatment, we designed experiments to evaluate the effects of ATO in combination with PI3K and MEK1/2 specific inhibitors, LY29004 and U0126, respectively, in SK-N-MC and SK-N-BE(2) cell lines. The results indicated that specific inhibition of PI3K and MEK1/2 significantly enhanced antiproliferative and proapoptotic effects of ATO in SK-N-BE(2), but not in SK-N-MC. Furthermore, in SK-N-BE(2), NF-κB activation was significantly suppressed by LY29004+ATO treatments as compared with ATO alone, indicating that inhibition of PI3K may enhance anti-neoplastic properties of ATO in I-type NB cells through suppression of NF-κB. Moreover, expressions of c-Myc, Bad, Bax and ATM in SK-N-BE(2) cell line were significantly increased by U0126+ATO treatment as compared to treatment with ATO alone. Expression of telomerase hTERT was almost depleted by U0126+ATO treatment. Regarding the fact that activation of PI3K and MAPK in SK-N-BE(2) is higher than in other NB subtypes, we hypothesize that growth of SK-N-BE(2) cell line is highly dependent on these pathways and inhibition of these pathways may has promise for the treatment of multi-drug resistant I-type NB cells by ATO. However, for successful strategies for the treatment of this heterogeneous tumor, other combinations approaches need to be considered to simultaneously target other NB cells.

Autocrine human growth hormone increases sensitivity of mammary carcinoma cell to arsenic trioxide-induced apoptosis

Human growth hormone (hGH) has been increasingly implicated in a variety of cancers; its up-regulation is observed in breast cancer and correlates with a poor outcome. Autocrine hGH promotes mammary carcinoma cell survival, proliferation, immortalization; it confers an invasive phenotype as a result of an epithelial-mesenchymal transition and contributes to chemoresistance and radioresistance. Arsenic trioxide (ATO) is being successfully used as a first and second line therapy for the treatment of patients with acute promyelocytic leukemia. It also inhibits tumor cell growth and induces apoptosis in a broad range of solid tumors. In the present study, we investigated the effect of hGH on sensitivity of a mammary adenocarcinoma cell to ATO, using a stable hGH-transfectant MCF-7 cell line, MCF7-hGH. Our results demonstrated for the first time that the overexpression of hGH increased sensitivity of the breast cancer cell line MCF-7 to ATO through apoptotic and anti-proliferative mechanisms. The effect of ATO on the transcriptional level of genes involved in survival (Bcl-2, Bax and Survivin), self-sufficiency in growth signals (c-Myc, ARF, Cdc25A, p53 and Bax), immortalization (hTERT) and invasion and metastasis (MMP-2 and MMP-9, uPA and uPAR and E-cadherin) was more pronounced in MCF7-hGH compared with its parental MCF-7 line. Our study may highlight the potential application of ATO for the treatment of patients with breast cancer, especially in those who have metastatic and chemoresistant tumor phenotype possibly due to the over expression of hGH.

Molecular mechanisms of silibinin-mediated cancer chemoprevention with major emphasis on prostate cancer

Despite advances in early detection, prostate cancer remains the second highest cancer mortality in American men, and even successful interventions are associated with enormous health care costs as well as prolonged deleterious effects on quality of patient life. Prostate cancer chemoprevention is one potential avenue to alleviate these burdens. It is a regime whereby long-term treatments are intended to prevent or arrest cancer development, in contrast to more direct intervention upon disease diagnosis. Based on this intention, cancer chemoprevention generally focuses on the use of nontoxic chemical agents which are well-tolerated for prolonged usage that is necessary to address prostate cancer's multistage and lengthy period of progression. One such nontoxic natural agent is the flavonoid silibinin, derived from the milk thistle plant (Silybum marianum), which has ancient medicinal usage and potent antioxidant activity. Based on these properties, silibinin has been investigated in a host of cancer models where it exhibits broad-spectrum efficacy against cancer progression both in vitro and in vivo without noticeable toxicity. Specifically in prostate cancer models, silibinin has shown the ability to modulate cell signaling, proliferation, apoptosis, epithelial to mesenchymal transition, invasion, metastasis, and angiogenesis, which taken together provides strong support for silibinin as a candidate prostate cancer chemopreventive agent.

The pterocarpanquinone LQB 118 induces apoptosis in tumor cells through the intrinsic pathway and the endoplasmic reticulum stress pathway

LQB 118 is a pterocarpanquinone compound synthesized by our group. It has already been shown that it acts against different leukemia cell lines. However, little is known about the pathway through which this compound induces the death of these cells. In this work, we analyzed the cell death process induced by LQB 118 in K562, a chronic myeloid leukemia cell line, and in Jurkat, a lymphoblastic acute leukemia cell line. For this, we carried out a cell viability assay by MTT, an apoptosis/necrosis assay through the annexin/propidium iodide label, cell cycle by flow cytometry, assessed changes in the mitochondrial membrane potential using DiOC6(3), cytoplasmic calcium analysis by Fluo-3-AM, and a caspase-9 and caspase-12 activity assay. We found that LQB 118 induced apoptosis in both cell lines, measuring caspase-12 and caspase-9 activation, phosphatidylserine externalization, and DNA fragmentation. The compound induced an increase in cytoplasmic calcium on both cell lines. However, the compound could only induce mitochondrial membrane depolarization on K562 cells. Our data show that LQB 118 may have potential therapeutic value for leukemia, being able to overcome multiple resistance mechanisms.

Silibinin induced the apoptosis of Hep-2 cells via oxidative stress and down-regulating survivin expression

Silibinin is an anticancer and chemopreventive natural compound, which is extracted from milk thistle (Silybum marianum). It is reported that silibinin has anticancer efficacy in many malignant tumors. Laryngeal carcinoma is the second most common head and neck squamous carcinoma. In the present work, we investigated the effects of silibinin on laryngeal squamous cell carcinoma (LSCC) cell line Hep-2 cells. We found that silibinin induced the decrease of cell viability in Hep-2 cells with a concentration- and time-dependent manner. Moreover, silibinin resulted in the apoptosis of Hep-2 cells and had synergy effects with arsenic trioxide. Intracellular reactive oxygen species (ROS) accumulation increased because of silibinin exposure. ROS scavenger NAC alleviated the cytotoxicity of silibinin to Hep-2 cells. The mitochondrial membrane potential (MMP) was lost in Hep-2 cells treated with silibinin. Subsequently, silibinin induced the activation of caspase-3 in Hep-2 cells and caspase inhibitor Z-VAD-FMK inhibited the cytotoxicity of silibinin in Hep-2 cells. The survivin expression decreased after Hep-2 cells were treated with silibinin. In conclusion, silibinin induced the apoptosis of Hep-2 cells via oxidative stress and down-regulating survivin expression. Therefore, silibinin is a potential therapeutical agent against LSCC in future.

Oleanolic acid potentiates the antitumor activity of 5-fluorouracil in pancreatic cancer cells

The antitumor activity of oleanolic (OA) has attracted attention due to its marked antitumor effects and pharmacological safety. In the present study, the effects of the combination of OA and 5-fluorouracil (5-FU) on Panc-28 human pancreatic cells were studied. The results showed that combined use of OA and 5-FU synergistically potentiated cell death effects on Panc-28 cells, and the pro-apoptotic effects were also increased. Further study revealed that the combined treatment could enhance mitochondrial depolarization, lysosomal membrane permeabilization (LMP) and leakage of cathepin D, while the release of cytochrome C did not display significant changes. The expression of apoptosis related proteins was also affected in cells treated with the combination of OA and 5-FU, including activation of caspases-3 and the expression of Bcl-2/Bax, survivin and NF-κB. Our results provide evidence that combination of OA and 5-FU may serve as a novel strategy for the treatment of pancreatic cancer.