Arsenic trioxide (As2O3) inhibits invasion of HT1080 human fibrosarcoma cells: Role of nuclear factor-κB and reactive oxygen species

Bi-directional regulation of TGF-β/Smad pathway by arsenic: A systemic review and meta-analysis of in vivo and in vitro studies

BACKGROUND

Arsenic exposure can cause fibrosis of organs including the liver, heart and lung. It was reported that TGF-β/Smad pathway played a crucial role in the process of fibrosis. However, the mechanism of arsenic-induced fibrosis through TGF-β/Smad signaling pathway has remained controversial.

OBJECTIVE

A systematic review and meta-analysis was performed to clarify the relationship between arsenic and TGF-β/Smad pathway, providing a theoretical basis of fibrosis process caused by arsenic.

METHODS

A meta-analysis was used to reveal a correlation between arsenic and fibrosis markers of TGF-β/Smad pathway, including 47 articles of both in vivo and in vitro studies. (Standardized Mean Difference) SMD was employed to compare and analyze the combined effects. When I2 > was 50%, random effect model was selected and subgroup analysis was used to explore the source of heterogeneity.

RESULTS

Arsenic exposure up-regulated the expression of TGF-β1, p-Smad2/3, α-SMA, Collagen1/3 and FN. The dose-response relationship showed that low dose (≤5 μmol/L) arsenic exposure up-regulated the expression of TGF-β1, whereas high doses had a tendency to down-regulate that of TGF-β1. Subgroup analysis showed that low or short-term arsenic exposure induced the expression of TGF-β1 and fibrosis markers.

CONCLUSION

The results indicated that arsenic activates the TGF-β/Smad pathway and induced fibrosis. The mechanism is related to the up-regulation of NADPH oxidase and ROS accumulation. However, high-dose arsenic exposure may inhibit this pathway.

A novel RGDyC/PEG co-modified PAMAM dendrimer-loaded arsenic trioxide of glioma targeting delivery system

Background

The Traditional Chinese Medicine, arsenic trioxide (ATO, As₂O₃) could inhibit growth and induce apoptosis in a variety of solid tumor cells, but it is severely limited in the treatment of glioma due to its poor BBB penetration and nonspecifcity distribution in vivo.

Purpose

The objective of this study was encapsulating ATO in the modified PAMAM den-drimers to solve the problem that the poor antitumor effect of ATO to glioma, which provide a novel angle for the study of glioma treatment.

Methods

The targeting drug carrier (RGDyC-mPEG-PAMAM) was synthesized based on Arg-Gly-Asp (RGDyC) and αvβ3 integrin targeting ligand, and conjugated to PEGylated fifth generation polyamidoamine dendrimer (mPEG-PAMAM). It was characterized by nuclear magnetic resonance, fourier transform infrared spectra, Nano-particle size-zeta potential analyzer,etc. The in vitro release characteristics were studied by dialysis bag method. MTT assay was used to investigate the cytotoxicity of carriers and the antitumor effect of ATO formulation. In vitro blood-brain barrier (BBB) and C6 cell co-culture models were established to investigate the inhibitory effect of different ATO formulation after transporting across BBB. Pharmacokinetic and antitumor efficacy studies were investigated in an orthotopic murine model of C6 glioma.

Results

The prepared RGDyC-mPEG-PAMAM was characterized for spherical dendrites, comparable size (21.60±6.81 nm), and zeta potential (5.36±0.22 mV). In vitro release showed that more ATO was released from RGDyC-mPEG-PAMAM/ATO (79.5%) at pH 5.5 than that of pH 7.4, during 48 hours. The cytotoxicity of PEG-modified carriers was lower than that of the naked PAMAM on both human brain microvascular endothelial cells and C6 cells. In in vitro BBB model, modification of RGDyC heightened the cytotoxicity of ATO loaded on PAMAM, due to an increased uptake by C6 cells. The results of cell cycle and apoptosis analysis revealed that RGDyC-mPEG-PAMAM/ATO arrested the cell cycle in G2-M and exhibited threefold increase in percentage of apoptosis to that in the PEG-PAMAM/ATO group. Compared with ATO-sol group, both RGDyC-mPEG-PAMAM/ATO and mPEG-PAMAM/ATO groups prolonged the half-life time, increased area under the curve, and improved antitumor effect, significantly. While the tumor volume inhibitory of RGDyC-mPEG-PAMAM/ATO was 61.46±12.26%, it was approximately fourfold higher than the ATO-sol group, and twofold to the mPEG-PAMAM/ATO group.

Conclusion

In this report, RGDyC-mPEG-PAMAM could enhance the antitumor of ATO to glioma, it provides a desirable strategy for targeted therapy of glioma.

Tetraarsenic oxide-induced inhibition of malignant glioma cell invasion in vitro via a decrease in matrix metalloproteinase secretion and protein kinase B phosphorylation

OBJECT

Local invasiveness of malignant glioma is a major reason for the failure of current treatments including surgery and radiation therapy. Tetraarsenic oxide (As4O6 [TAO]) is a trivalent arsenic compound that has potential anticancer and antiangiogenic effects in selected cancer cell lines at a lower concentration than arsenic trioxide (As2O3 [ATO]), which has been more widely tested in vitro and in vivo. The authors tried to determine the cytotoxic concentration of TAO in malignant glioma cell lines and whether TAO would show anti-invasive effects under conditions independent of cell death or apoptosis.

METHODS

The human phosphatase and tensin homolog (PTEN)-deficient malignant glioma cell lines U87MG, U251MG, and U373MG together with PTEN-functional LN428 were cultured with a range of micromolar concentrations of TAO. The invasiveness of the glioma cell lines was analyzed. The effect of TAO on matrix metalloproteinase (MMP) secretion and membrane type 1 (MT1)-MMP expression was measured using gelatin zymography and Western blot, respectively. Akt, or protein kinase B, activity, which is a downstream effector of PTEN, was assessed with a kinase assay using glycogen synthesis kinase-3β (GSK-3β) as a substrate and Western blotting of phosphorylated Akt.

RESULTS

Tetraarsenic oxide inhibited 50% of glioma cell proliferation at 6.3-12.2 μM. Subsequent experiments were performed under the same TAO concentrations and exposure times, avoiding the direct tumoricidal effect of TAO, which was confirmed with apoptosis markers. An invasion assay revealed a dose-dependent decrease in invasiveness under the influence of TAO. Both the gelatinolytic activity of MMP-2 and MT1-MMP expression decreased in a dose-dependent manner in all cell lines, which was in accordance with the invasion assay results. The TAO decreased kinase activity of Akt on GSK-3β assay and inhibited Akt phosphorylation in a dose-dependent manner in all cell lines regardless of their PTEN status.

CONCLUSIONS

These results showed that TAO effectively inhibits proliferation of glioblastoma cell lines and also exerts an anti-invasive effect via decreased MMP-2 secretion, decreased MT1-MMP expression, and the inhibition of Akt phosphorylation under conditions devoid of cytotoxicity. Further investigations using an in vivo model are needed to evaluate the potential role of TAO as an anti-invasive agent.

Arsenic trioxide attenuates the invasion potential of human liver cancer cells through the demethylation-activated microRNA-491

Hepatocellular carcinoma (HCC) represents the third leading cause of cancer-related mortality worldwide. Current standard practices for treatment of HCC are less than satisfactory because of metastasis and recurrence. In addition to treating acute promyelocytic leukemia (APL), arsenic trioxide (As2O3) also suppresses other solid tumors, such as HCC. However, the effects of As2O3 on the migration/invasion potential of liver cancer cells and the molecular mechanisms underlying in remain unclear. Here we found that As2O3 attenuated the migration/invasion potential of HCC cell lines by blocking matrix metalloproteinases (MMPs) activities and inducing a mesenchymal to epithelial transition (MET). Indeed, As2O3 elevated the expression of microRNA-491 (miR-491) via demethylation. On one hand, as a target miRNA of MMP9, miR-491 decreased the MMP9 expression. On the other hand, miR-491 blocked the activation of nuclear factor κB (NF-κB), which transcriptionally inactivated MMP2 and induced a MET (as determined by the increased expression of E-cadherin and decreased expressions of snail, slug, and vimentin). Knockdown of miR-491 abolished the As2O3-induced MMPs inactivation, MET, and the migration/invasion potential of HCC cell lines. By understanding a novel mechanism how As2O3 inhibits the migration/invasion potential of liver cancer cells, our study may help to identify potential therapeutic targets for liver cancer.

Investigation of the mechanism involved in the As2O3-regulated decrease in MDR1 expression in leukemia cells

Arsenic trioxide (As2O3) inhibits the expression of P-glycoprotein (P-gp) in leukemia cells; however, the mechanism behind this inhibition is unclear. The present study aimed to explore the effect of As2O3 on the expression and regulation of P-gp in leukemia cells, and elucidate the mechanism of the reversal of drug resistance. In the present study, electrophoretic mobility shift assay results indicated that p65 binds to the NF-κB binding site of MDR1, specifically in K562/D cells. Expression of p65 and phosphorylated IκB was reduced, while the expression of IκB was increased in K562/D cells treated with As2O3. The activity of luciferase increased up to 9-fold with 40 ng/ml TNF-α, and it was suppressed by ~25% following treatment with 1 µM As2O3. These findings suggest that As2O3 reverses the P-gp-induced drug resistance of leukemia cells through the NF-κB pathway. As2O3 may inhibit the activity of phosphorylase to inhibit IκB phosphorylation, thereby inhibiting NF-κB activity and MDR1 gene expression, leading to reversal of drug resistance.

(-)-Epigallocatechin-3-gallate blocks nicotine-induced matrix metalloproteinase-9 expression and invasiveness via suppression of NF-κB and AP-1 in endothelial cells

Cigarette smoke, specifically the nicotine contained within, has been shown to correlate closely with cell invasion and strategies to downregulate their expression may ultimately be of clinical utility. Matrix metalloproteinase-9 (MMP-9) is critically involved in the cell invasion and metastasis processes. Since nicotine plays a crucial role in the regulation of MMP-9 expression, the investigation of plant-derived compounds capable of modulating nicotine-induced signaling is an issue of concern. In this study, the effects of (-)-epigallocatechin-3-gallate (EGCG), a major green tea catechin, on nicotine-induced cell invasion and MMP-9 activity in ECV304 human endothelial cells were examined. EGCG treatment was found to reduce the MMP-9 expression and transcriptional activity in a dose-dependent manner. EGCG inhibited nicotine-activated production of reactive oxygen species (ROS), which are known as important signaling molecules to activate MMP-9. To further study the mechanisms for the EGCG-mediated regulation of MMP-9, the transcription factors NF-κB and AP-1 activities were examined. EGCG suppressed the nicotine-induced NF-κB and AP-1 activation. Studies with expression vectors encoding mutated NF-κB signaling molecules and AP-1 decoy confirmed that NF-κB and AP-1 were essential for the nicotine-stimulated MMP-9 expression. EGCG also abrogated the nicotine-induced activation of AP-1 subunits c-fos and c-jun. The above studies demonstrate that EGCG may exert at least part of its anti-invasive effect in ECV304 human endothelial cells by controlling MMP-9 expression through the suppression of ROS, NF-κB and AP-1.

The behavior of matrix metalloproteinases and their inhibitors in colorectal cancer

Matrix metalloproteinases (MMPs) play an important role in the degradation of extracellular matrix components crucial for tumor growth, invasion and metastasis. MMPs are controlled by natural inhibitors called tissue inhibitors of metalloproteinases (TIMPs). We and others have demonstrated that MMPs and TIMPs are especially important in the process of tumor invasion, progression and the metastasis of colorectal cancer (CRC). It has been proposed that MMPs and TIMPs might play a part not only in tumor invasion and initiation of metastasis but also in carcinogenesis from colorectal adenomas. Several recent studies demonstrated that high preoperative serum or plasma MMP-2, MMP-9 and TIMP-1 antigen levels are strong predictive factors for poor prognosis in patients with CRC and their determination might be useful for identification of patients with higher risk for cancer recurrence. MMP-9 and TIMP-1 have significant potential tumor marker impact in CRC. Their diagnostic sensitivity is consistently higher than those of conventional biomarkers. The pharmacological targeting of CRC by the development of a new generation of selective inhibitors of MMPs, that is highly specific for certain MMPs, is a promising and challenging area for the future.

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.

Arsenic trioxide inhibits Ewing's sarcoma cell invasiveness by targeting p38(MAPK) and c-Jun N-terminal kinase

Ewing's sarcoma is the second most frequent primary malignant bone tumor, mainly affecting children and young adults. The notorious metastatic capability of this tumor aggravates patient mortality and remains a problem to be overcome. We investigated the effect of arsenic trioxide (As₂O₃) on the metastasis capability of Ewing's sarcoma cells. We performed 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide assays to choose appropriate concentrations of As₂O₃ for the experiments. Migration, invasion, and adhesion assays were performed to assess the effect of As₂O₃ on the metastasis of Ewing's sarcoma. Immunofluorescent staining was used to observe cytoskeleton reorganization in Ewing's sarcoma cells treated with As₂O₃. Changes in matrix metalloproteinase-9 expression and the mitogen-activated protein kinase (MAPK) pathway were investigated using western blot. Inhibitors of p38(MAPK) (sb202190) and c-Jun NH₂-terminal kinase (JNK, sp600125) were used in invasion assays to determine the effect of p38(MAPK) and JNK. We found that As₂O₃ may markedly inhibit the migration and invasion capacity of Ewing's sarcoma cells with structural rearrangements of the actin cytoskeleton. The expressions of matrix metalloproteinase-9, phosphor-p38(MAPK), and phosphor-JNK were suppressed by As₂O₃ treatment in a dose-dependent manner. The inhibitors of p38(MAPK) (sb202190) and JNK (sp600125) enhanced the inhibition induced by As₂O₃, which was counteracted by anisomycin, an activating agent of p38(MAPK) and JNK. Taken together, our results demonstrate that As₂O₃ can inhibit the metastasis capability of RD-ES and A-673 cells and may have new therapeutic value for Ewing's sarcoma.

Cannabinoids, endocannabinoids, and cancer

The endocannabinoid system consists of an array of endogenously produced bioactive lipids that activate cannabinoid receptors. Although the primary focus of endocannabinoid biology has been on neurological and psychiatric effects, recent work has revealed several important interactions between the endocannabinoid system and cancer. Several different types of cancer have abnormal regulation of the endocannabinoid system that contributes to cancer progression and correlates to clinical outcomes. Modulation of the endocannabinoid system by pharmacological agents in various cancer types reveals that it can mediate antiproliferative and apoptotic effects by both cannabinoid receptor-dependent and -independent pathways. Selective agonists and antagonists of the cannabinoid receptors, inhibitors of endocannabinoid hydrolysis, and cannabinoid analogs have been utilized to probe the pathways involved in the effects of the endocannabinoid system on cancer cell apoptosis, proliferation, migration, adhesion, and invasion. The antiproliferative and apoptotic effects produced by some of these pharmacological probes reveal that the endocannabinoid system is a promising new target for the development of novel chemotherapeutics to treat cancer.

Antiproliferative and anti-invasive effects of inorganic and organic arsenic compounds on human and murine melanoma cells in vitro

OBJECTIVES

For patients with advanced melanoma, no treatment options are available at present that provide either sufficient response rates or a significant prolongation of overall survival. The present study examines the effects of two inorganic and six organic arsenic compounds on cell proliferation and cell invasion of melanoma cells in vitro.

METHODS

The effects of arsenic compounds on proliferation of human melanoma A375 cells and murine melanoma B16F10 cells were examined by MTT assay and 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, and the effects of the compounds on cell invasion were examined by the Boyden chamber invasion assay. The amounts of active matrix metalloproteinase (MMP)-2 and pro-MMP-2 in the culture supernatant of A375 cells were determined by an MMP-2 activity assay system.

KEY FINDINGS

Arsenate and arsenic trioxide (As(2) O(3) ) inhibited the proliferation of A375 and B16F10 cells significantly at concentration ranges of 0.1-20µg/ml (P<0.001), while the organic compounds arsenobetaine, arsenocholine, dimethylarsinic acid, methylarsonic acid, tetramethylarsonium and trimethylarsine oxide did not show any inhibitory effects even at 20µg/ml. Cell invasion of A375 and B16F10 cells through a layer of collagen IV was significantly inhibited by 0.1-20 µg/ml of arsenate or As(2) O(3) (P<0.05), while the organic compounds did not inhibit cell invasion. Arsenate or As(2) O(3) at 0.2-10µg/ml significantly inhibited the amount of active MMP-2 and pro-MMP-2 secreted into the A375 cell culture supernatant (P<0.05).

CONCLUSIONS

Our findings show that the inorganic arsenic compounds arsenate and As(2) O(3) inhibit cell proliferation and prevent the invasive properties of melanoma cells, possibly by decreasing MMP-2 production from the cells.

Cisplatin and PI3kinase inhibition decrease invasion and migration of human ovarian carcinoma cells and regulate matrix-metalloproteinase expression

Targeting of the PI3K (phosphoinositide3-kinase)/Akt/mTOR pathway in human ovarian cancer cells is a promising novel therapeutic strategy. We investigated the effects of cisplatin and the PI3K inhibitor LY294002 on invasion, migration and the expression of essential matrix metalloproteinases (MMPs) in ovarian cancer cells. SKOV3, OVCAR5 and IGROV1 human ovarian cancer cell lines were treated with cisplatin, LY294002 and a combination of both drugs. Invasion and migration of treated cells was assessed using Matrigel and uncoated PET membrane assays. Expression levels of pro-MMP2, MMP2, TIMP1, TIMP2 and MT1-MMP were determined using Western Blotting. Gel zymography was used to quantitate the functional levels of active MMP2. All three cell lines showed significantly reduced invasion and migration after treatment with cisplatin, LY294002, and the combination of both drugs compared to untreated controls. In SKOV3 cells, cisplatin alone and in combination with LY294002 resulted in a 6.3 and 7.1-fold reduction in the total amount of activated MMP2. TIMP1 expression decreased by 5.0, 6.6 and 28.4-fold with cisplatin, LY294002 and the combination respectively (P < 0.05). In contrast, only cisplatin and the combination of both drugs resulted in a significant, 3.7 and 5.1-fold reduction in the level of TIMP2. Expression levels of MT1-MMP remained unchanged. These observations were corroborated in IGROV1 cell lines that showed similar changes of activated MMP2 and TIMP2 expression, but no significant decrease in TIMP1 levels. Our data suggests that inhibition of ovarian cancer cell motility is mediated via down-regulation of activated MMP2, TIMP1 and TIMP2 expression under these treatment conditions.

Involvement of ROS in chlorogenic acid-induced apoptosis of Bcr-Abl+ CML cells

Chlorogenic acid (Chl) has been reported to possess a wide range of biological and pharmacological properties including induction of apoptosis of Bcr-Abl(+) chronic myeloid leukemia (CML) cell lines and clinical leukemia samples via inhibition of Bcr-Abl phosphorylation. Here we studied the mechanisms of action of Chl in greater detail. Chl treatment induced an early accumulation of intracellular reactive oxygen species (ROS) in Bcr-Abl(+) cells leading to downregulation of Bcr-Abl phosphorylation and apoptosis. Chl treatment upregulated death receptor DR5 and induced loss of mitochondrial membrane potential accompanied by release of cytochrome c from the mitochondria to the cytosol. Pharmacological inhibition of caspase-8 partially inhibited apoptosis, whereas caspase-9 and pan-caspase inhibitor almost completely blocked the killing. Knocking down DR5 using siRNA completely attenuated Chl-induced caspase-8 cleavage but partially inhibited apoptosis. Antioxidant NAC attenuated Chl-induced oxidative stress-mediated inhibition of Bcr-Abl phosphorylation, DR5 upregulation, caspase activation and CML cell death. Our data suggested the involvement of parallel death pathways that converged in mitochondria. The role of ROS in Chl-induced death was confirmed with primary leukemia cells from CML patients in vitro as well as in vivo in nude mice bearing K562 xenografts. Collectively, our results establish the role of ROS for Chl-mediated preferential killing of Bcr-Abl(+) cells.

Signal transduction pathways and transcription factors triggered by arsenic trioxide in leukemia cells

Arsenic trioxide (As(2)O(3)) is widely used to treat acute promyelocytic leukemia (APL). Several lines of evidence have indicated that As(2)O(3) affects signal transduction and transactivation of transcription factors, resulting in the stimulation of apoptosis in leukemia cells, because some transcription factors are reported to associate with the redox condition of the cells, and arsenicals cause oxidative stress. Thus, the disturbance and activation of the cellular signaling pathway and transcription factors due to reactive oxygen species (ROS) generation during arsenic exposure may explain the ability of As(2)O(3) to induce a complete remission in relapsed APL patients. In this report, we review recent findings on ROS generation and alterations in signal transduction and in transactivation of transcription factors during As(2)O(3) exposure in leukemia cells.

Subtractive proteomic approach to the endometrial carcinoma invasion front

Tumor invasion defines the transition between tissue-restricted carcinomas, related to good outcome as optimal surgery becomes possible, and metastatic tumors associated with poor prognosis and a dramatic decrease in survival. In endometrial cancer, myometrial infiltration represents a determinant parameter highly valuable in prognosis. To date, the identification of proteins involved in endometrial carcinoma invasion has been essentially conducted by immunohistochemical methods, without a global perception on the invasive front. Laser microdissection presents nowadays limitations to the profound spatiotemporal regulation from both the tumor and the surrounding stroma occurring at the invasive front. In this work, we attempted an alternative proteomic approach to characterize specific components of the tumor invasive front or its reactive stroma, by comparing the invasive area of an endometrial carcinoma with the noninvasive superficial tumor area and normal tissue from the same patients. This strategy led us to identify proteins involved in cellular morphology, assembly and movement, differentially expressed at the invasive front, as well as pathways like cell-to-cell signaling and interaction and a modulated response to oxidative stress as events related to endometrial carcinoma invasion. In conclusion, we could identify new players of myometrial infiltration by applying a subtractive proteomic approach to the endometrial carcinoma invasion front.

Antitumorigenic effects of cannabinoids beyond apoptosis

According to the World Health Organization, the cases of death caused by cancer will have been doubled until the year 2030. By 2010, cancer is expected to be the number one cause of death. Therefore, it is necessary to explore novel approaches for the treatment of cancer. Over past years, the antitumorigenic effects of cannabinoids have emerged as an exciting field in cancer research. Apart from their proapoptotic and antiproliferative action, recent research has shown that cannabinoids may likewise affect tumor cell angiogenesis, migration, invasion, adhesion, and metastasization. This review will summarize the data concerning the influence of cannabinoids on these locomotive processes beyond modulation of cancer cell apoptosis and proliferation. The findings discussed here provide a new perspective on the antitumorigenic potential of cannabinoids.

Paeonol exerts anti-angiogenic and anti-metastatic activities through downmodulation of Akt activation and inactivation of matrix metalloproteinases

Paeonol (2'-hydroxy-4'-methoxyacetophenone) is known to possess anti-inflammatory and anti-proliferative activities. Recently there is evidence that anti-inflammatory agents may be useful in the setting of angiogenesis-related diseases. Thus in the present study the anti-angiogenic activity of paeonol and its mechanism were investigated in vitro and in vivo. Paeonol significantly inhibited proliferation of basic fibroblast growth factor (bFGF)-stimulated human umbilical vein endothelial cells (HUVECs). Paeonol also significantly inhibited migration and tube formation of bFGF-stimulated HUVECs in vitro. In addition, paeonol significantly suppressed neovessel formation on bFGF-treated chick chorioallantoic membrane (CAM) and disrupted bFGF-induced neovascularization in Matrigel plug assay in vivo. Furthermore, paeonol downregluated Akt phosphorylation in bFGF-stimulated HUVECs and reduced expression of matrix metalloproteinases-2 and -9 in HT1080 human fibrosarcoma cells. The Akt inhibitor LY294002 synergistically potentiated paeonol-induced inactivation of Akt and vascular endothelial growth factor in bFGF-treated HUVECs. Taken together, these findings suggest that paeonol can be a potent suppressor of angiogenesis and metastasis partially through inhibition of Akt signaling pathway and matrix metalloproteinase activity.

Arsenic trioxide induces apoptosis in NB-4, an acute promyelocytic leukemia cell line, through up-regulation of p73 via suppression of nuclear factor kappa B-mediated inhibition of p73 transcription and prevention of NF-kappaB-mediated induction of XIAP, cIAP2, BCL-XL and survivin

The purpose of the present study is to evaluate the effects of arsenic trioxide (ATO) on human acute promyelocytic leukemia NB-4 cells. Microculture tetrazolium test, bromodeoxyuridine (BrdU) cell proliferation assay, caspase 3 activity assay, cell-based nuclear factor kappa B (NF-kappaB) phosphorylation measurement by ELISA and real-time RT-PCR were employed to appraise the effects of ATO on metabolic activity, DNA synthesis, induction of programmed cell death and NF-kappaB activation. The suppressive effects of ATO on metabolic potential, cell proliferation and NF-kappaB activation were associated with induction of apoptosis in NB-4 cells. In addition, an expressive enhancement in mRNA levels of p73, cyclin-dependent kinase inhibitor 1A (p21), tumor protein 53-induced nuclear protein 1 (TP53INP1), WNK lysine deficient protein kinase 2 (WNK2) and lipocalin 2 coupled with a significant reduction in transcriptional levels of NF-kappaB inhibitor beta (IKK2), Nemo, BCL2-like 1 (BCL-X(L)), inhibitor of apoptosis protein 1 (cIAP2), X-linked inhibitor of apoptosis protein (XIAP), survivin, Bcl-2, TIP60, ataxia telangiectasia (ATM), SHP-2 and sirtuin (SIRT1) were observed. Altogether, these issues show for the first time that ATO treatment could trammel cell growth and proliferation as well as induces apoptosis in NB-4 cells through induction of transcriptional levels of p73, TP53INP1, WNK2, lipocalin 2 as well as suppression of NF-kappaB-mediated induction of BCL-X(L), cIAP2, XIAP and survivin. Furthermore, the inductionary effects of ATO on transcriptional stimulation of p73 might be through cramping the NF-kappaB module (through suppression of p65 phosphorylation as well as transcriptional hindering of IKK2, ATM and Nemo) along with diminishing the mRNA expression of TIP60, SHP-2 and SIRT1.

Involvement of matrix metalloproteinase 2 and 9 in gambogic acid induced suppression of MDA-MB-435 human breast carcinoma cell lung metastasis

Cancer cell invasion is one of the crucial events in local spreading, growth, and metastasis of tumors. The present study investigated the antiinvasive and antimetastatic action of gambogic acid (GA) in MDA-MB-435 human breast carcinoma cells. GA caused a concentration-dependent suppression of cell invasion through Matrigel and significantly inhibited lung metastases of the cells transplanted in vivo. The potent effects of GA have been attributed to its ability to reduce the expression of matrix metalloproteinases (MMP) 2 and 9 in vitro and in vivo both at the protein and mRNA levels, which were associated with protein kinase C (PKC) signaling pathway as supported by the diminished antiinvasive effect of GA in the presence of specific activator of the pathway. Collectively, our data demonstrated that GA exhibited antiinvasion properties on highly invasive cancer cells via PKC mediated MMP-2/9 expression inhibition. This indicated that GA can be served as a potential novel therapeutic candidate for the treatment of cancer metastasis.

Emodin upregulates urokinase plasminogen activator, plasminogen activator inhibitor-1 and promotes wound healing in human fibroblasts

Urokinase plasminogen activator (uPA) system is important for several biological processes that call for extracellular proteolysis, fibrinolysis, cell migration, proliferation and angiogenesis. The current study highlights the fibrinolytic and wound healing potential of emodin, an anthraquinone, with relevance to the uPA system. Emodin increased the fibrinolytic activity of fibroblast cells in a dose-dependent manner. Zymography linked the activity to increased uPA activity. Subsequent RT-PCR and western analyses demonstrated uPA gene upregulation. Interestingly, PAI-1, the inhibitor of uPA was also upregulated. EMSA showed the upregulation occurred independent of emodin's effect on nuclear factor kappa B (NFkappaB). The effect on uPA system is supposedly via generation of reactive oxygen species (ROS) since cotreatment with ascorbic acid, an anti-oxidant, attenuated the activity. In addition to profibrinolytic potential, emodin also demonstrated wound healing activity in in vitro wound models. Presence of emodin in the medium enhanced the rate of migration of fibroblasts into the wounded region. These in vitro experiments reveal that emodin is a potent profibrinolytic and wound healing agent.

Genetic and epigenetic mechanisms in metal carcinogenesis and cocarcinogenesis: nickel, arsenic, and chromium

Chronic exposure to nickel(II), chromium(VI), or inorganic arsenic (iAs) has long been known to increase cancer incidence among affected individuals. Recent epidemiological studies have found that carcinogenic risks associated with chromate and iAs exposures were substantially higher than previously thought, which led to major revisions of the federal standards regulating ambient and drinking water levels. Genotoxic effects of Cr(VI) and iAs are strongly influenced by their intracellular metabolism, which creates several reactive intermediates and byproducts. Toxic metals are capable of potent and surprisingly selective activation of stress-signaling pathways, which are known to contribute to the development of human cancers. Depending on the metal, ascorbate (vitamin C) has been found to act either as a strong enhancer or suppressor of toxic responses in human cells. In addition to genetic damage via both oxidative and nonoxidative (DNA adducts) mechanisms, metals can also cause significant changes in DNA methylation and histone modifications, leading to epigenetic silencing or reactivation of gene expression. In vitro genotoxicity experiments and recent animal carcinogenicity studies provided strong support for the idea that metals can act as cocarcinogens in combination with nonmetal carcinogens. Cocarcinogenic and comutagenic effects of metals are likely to stem from their ability to interfere with DNA repair processes. Overall, metal carcinogenesis appears to require the formation of specific metal complexes, chromosomal damage, and activation of signal transduction pathways promoting survival and expansion of genetically/epigenetically altered cells.

Inhibition of cancer cell invasion by cannabinoids via increased expression of tissue inhibitor of matrix metalloproteinases-1

BACKGROUND

Cannabinoids, in addition to having palliative benefits in cancer therapy, have been associated with anticarcinogenic effects. Although the antiproliferative activities of cannabinoids have been intensively investigated, little is known about their effects on tumor invasion.

METHODS

Matrigel-coated and uncoated Boyden chambers were used to quantify invasiveness and migration, respectively, of human cervical cancer (HeLa) cells that had been treated with cannabinoids (the stable anandamide analog R(+)-methanandamide [MA] and the phytocannabinoid delta9-tetrahydrocannabinol [THC]) in the presence or absence of antagonists of the CB1 or CB2 cannabinoid receptors or of transient receptor potential vanilloid 1 (TRPV1) or inhibitors of p38 or p42/44 mitogen-activated protein kinase (MAPK) pathways. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were used to assess the influence of cannabinoids on the expression of matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs). The role of TIMP-1 in the anti-invasive action of cannabinoids was analyzed by transfecting HeLa, human cervical carcinoma (C33A), or human lung carcinoma cells (A549) cells with siRNA targeting TIMP-1. All statistical tests were two-sided.

RESULTS

Without modifying migration, MA and THC caused a time- and concentration-dependent suppression of HeLa cell invasion through Matrigel that was accompanied by increased expression of TIMP-1. At the lowest concentrations tested, MA (0.1 microM) and THC (0.01 microM) led to a decrease in invasion (normalized to that observed with vehicle-treated cells) of 61.5% (95% CI = 38.7% to 84.3%, P < .001) and 68.1% (95% CI = 31.5% to 104.8%, P = .0039), respectively. The stimulation of TIMP-1 expression and suppression of cell invasion were reversed by pretreatment of cells with antagonists to CB1 or CB2 receptors, with inhibitors of MAPKs, or, in the case of MA, with an antagonist to TRPV1. Knockdown of cannabinoid-induced TIMP-1 expression by siRNA led to a reversal of the cannabinoid-elicited decrease in tumor cell invasiveness in HeLa, A549, and C33A cells.

CONCLUSION

Increased expression of TIMP-1 mediates an anti-invasive effect of cannabinoids. Cannabinoids may therefore offer a therapeutic option in the treatment of highly invasive cancers.

Adenovirus-mediated REIC/Dkk-3 gene transfer inhibits tumor growth and metastasis in an orthotopic prostate cancer model

We had previously reported that REIC/Dkk-3, a member of the Dickkopf (Dkk) gene family, works as a tumor suppressor. In this study, we evaluated the therapeutic effects of an intratumoral injection with adenoviral vector encoding REIC/Dkk-3 gene (Ad-REIC) using an orthotopic mouse prostate cancer model of RM-9 cells. We also investigated the in vivo anti-metastatic effect and in vitro anti-invasion effect of Ad-REIC gene delivery. We demonstrated that the Ad-REIC treatment inhibited prostate cancer growth and lymph node metastasis, and prolonged mice survival in the model. These therapeutic responses were consistent with the intratumoral apoptosis induction and in vitro suppression of cell invasion/migration with reduced matrix metalloprotease-2 activity. We thus concluded that in situ Ad-REIC/Dkk-3 gene transfer may be a promising therapeutic intervention modality for the treatment of prostate cancer.

Upregulation of tissue inhibitor of matrix metalloproteinases-1 confers the anti-invasive action of cisplatin on human cancer cells

Cancer cell invasion is one of the crucial events in local spreading, growth and metastasis of tumors. The present study investigates the mechanism underlying the anti-invasive action of the chemotherapeutic cisplatin. In human cervical carcinoma cells (HeLa), cisplatin caused a time- and concentration-dependent suppression of cell invasion through Matrigel. Inhibition of invasion was accompanied by upregulation of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), whereas levels of matrix metalloproteinase-2 (MMP-2), MMP-9 and TIMP-2 remained unchanged. Cisplatin's effects on TIMP-1 expression and invasion were associated with phosphorylations of p38 and p42/44 mitogen-activated protein kinases and were abrogated by specific inhibitors of both pathways. The impact of TIMP-1 in the anti-invasive action of cisplatin was proven by transfecting cells with small interfering RNA targeting TIMP-1, which completely reversed suppression of invasion by cisplatin. A functional relevance of TIMP-1 upregulation was substantiated by findings showing a concentration-dependent inhibition of Matrigel invasion by recombinant TIMP-1. The essential role of TIMP-1 in the anti-invasive action of cisplatin was confirmed using another human cervical carcinoma cell line (C33A) and human lung carcinoma cells (A549). Altogether, our data demonstrate a hitherto unknown mechanism by which cisplatin exerts its antimetastatic properties on highly invasive cancer cells.

Interleukin-1β increases expression and activity of matrix metalloproteinase-2 in cardiac microvascular endothelial cells: role of PKCα/β1and MAPKs

Matrix metalloproteinases (MMPs), a family of extracellular endopeptidases, are implicated in angiogenesis because of their ability to selectively degrade components of the extracellular matrix. Interleukin-1β (IL-1β), increased in the heart post-myocardial infarction (post-MI), plays a protective role in the pathophysiology of left ventricular (LV) remodeling following MI. Here we studied expression of various angiogenic genes affected by IL-1β in cardiac microvascular endothelial cells (CMECs) and investigated the signaling pathways involved in the regulation of MMP-2. cDNA array analysis of 96 angiogenesis-related genes indicated that IL-1β modulates the expression of numerous genes, notably increasing the expression of MMP-2, not MMP-9. RT-PCR and Western blot analyses confirmed increased expression of MMP-2 in response to IL-1β. Gelatin in-gel zymography and Biotrak activity assay demonstrated that IL-1β increases MMP-2 activity in the conditioned media. IL-1β activated ERK1/2, JNKs, and protein kinase C (PKC), specifically PKCα/β1, and inhibition of these cascades partially inhibited IL-1β-stimulated increases in MMP-2. Inhibition of PKCα/β1failed to inhibit ERK1/2. However, concurrent inhibition of PKCα/β1and ERK1/2 almost completely inhibited IL-1β-mediated increases in MMP-2 expression. Inhibition of p38 kinase and nuclear factor-κB (NF-κB) had no effect. Pretreatment with superoxide dismutase (SOD) mimetic, MnTMPyP, increased MMP-2 protein levels, whereas pretreatment with SOD and catalase mimetic, EUK134, partially inhibited IL-1β-stimulated increases in MMP-2 protein levels. Exogenous H2O2significantly increased MMP-2 protein levels, whereas superoxide generation by xanthine/xanthine oxidase had no effect. This in vitro study suggests that IL-1β modulates expression and activity of MMP-2 in CMECs.

Peroxynitrite-modified collagen-II induces p38/ERK and NF-kappaB-dependent synthesis of prostaglandin E2 and nitric oxide in chondrogenically differentiated mesenchymal progenitor cells

OBJECTIVE

Peroxynitrite (ONOO(-)) is formed in the inflamed and degenerating human joint. Peroxynitrite-modified collagen-II (PMC-II) was recently discovered in the serum of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Therefore we investigated the cellular effects of PMC-II on human mesenchymal progenitor cells (MPCs) as a model of cartilage and cartilage repair cells in the inflamed and degenerating joint.

DESIGN

MPCs were isolated from the trabecular bone of patients undergoing reconstructive surgery and were differentiated into a chondrogenic lineage. Cells were exposed to PMC-II and levels of the proinflammatory mediators nitric oxide (*NO) and prostaglandin E(2) (PGE(2)) measured. Levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), phosphorylated mitogen activated protein kinases (MAPKs) and nuclear factor kappa B (NF-kappaB) activation were measured by enzyme linked immunosorbent assay (ELISA) together with specific MAPK and NF-kappaB inhibitors.

RESULTS

PMC-II induced ()NO and PGE(2) synthesis through upregulation of iNOS and COX-2 proteins. PMC-II also lead to the phosphorylation of MAPKs, extracellularly regulated kinase 1/2 (ERK1/2) and p38 [but not c-Jun NH(2)-terminal kinase (JNK1/2)] and the activation of proinflammatory transcription factor NF-kappaB. Inhibitors of p38, ERK1/2 and NF-kappaB prevented PMC-II induced ()NO and PGE(2) synthesis, iNOS and COX-2 protein expression and NF-kappaB activation.

CONCLUSION

iNOS, COX-2, NF-kappaB and MAPK are known to be activated in the joints of patients with OA and RA. PMC-II induced iNOS and COX-2 synthesis through p38, ERK1/2 and NF-kappaB dependent pathways suggesting a previously unidentified pathway for the synthesis of the proinflammatory mediators, ()NO and PGE(2), further suggesting that inhibitors of these pathways may be therapeutic in the inflamed and degenerating human joint.

Arsenic trioxide (As(2)O(3)) inhibits peritoneal invasion of ovarian carcinoma cells in vitro and in vivo

OBJECTIVES

To study the role of arsenic trioxide (As(2)O(3)) in regulating peritoneal invasive activity of ovarian carcinoma cells in vitro and in vivo.

METHODS

The effects of As(2)O(3) on human ovarian cancer cell lines (3AO, SW626 and HO-8910PM) migration, invasion and adhesion with tumor cells and human peritoneal mesothelial cells (HPMC) were observed by means of cell migration test, cell invasion test and cell adhesion test. The effects of As(2)O(3) on MMP-2, MMP-9, TIMP-1 and TIMP-2 gene expressions and protein expressions of tumor cells were determined by RT-PCR and ELISA, respectively. In animal experiments, ovarian tumor cells were implanted into abdominal cavity of nude mice and then the nude mice were treated by intraperitoneal injection of different doses As(2)O(3). The foci on the surface of peritoneum were counted.

RESULTS

As(2)O(3) inhibited tumor cells migration, invasion and adhesion with HPMC in a dose-dependent manner, while the same treatment enhanced tumor cell-tumor cell interactions. As(2)O(3) inhibited mRNA and protein expressions of MMP-2, MMP-9 and TIMP-2 of tumor cells. In contrast, As(2)O(3) increased mRNA and protein expressions of TIMP-1. As(2)O(3) could reduce tumor cells peritoneal metastasis in nude mice.

CONCLUSION

As(2)O(3) inhibits in vitro and in vivo peritoneal invasive activity of ovarian carcinoma cells in a dose-dependent manner. Its anti-invasive activity may be the results of reduced cell motility, inhibited attachment of tumor cells to HPMC and enhanced tumor cell-tumor cell interaction, as well as down-regulation of MMP-2 and MMP-9 levels and up-regulation of TIMP-1 level.