Arsenic trioxide as a novel anticancer agent against human transitional carcinoma--characterizing its apoptotic pathway

Parthenolide and arsenic trioxide co-trigger autophagy-accompanied apoptosis in hepatocellular carcinoma cells

Although arsenic trioxide (ATO) shows a strong anti-tumor effect in the treatment of acute promyelocytic leukemia, it does not benefit patients with hepatocellular carcinoma (HCC). Thus, combination therapy is proposed to enhance the efficacy of ATO. Parthenolide (PTL), a natural compound, selectively eradicates cancer cells and cancer stem cells with no toxicity to normal cells. In this study, we chose PTL and ATO in combination and found that nontoxic dosage of PTL and ATO co-treatment can synergistically inhibit the in vitro and in vivo proliferation activity of HCC cells through suppressing stemness and self-renewal ability and inducing mitochondria-dependent apoptosis. More importantly, USP7-HUWE1-p53 pathway is involved in PTL enhancing ATO-induced apoptosis of HCC cell lines. Meanwhile, accompanied by induction of apoptosis, PTL and ATO evoke autophagic activity via inhibiting PI3K/Akt/mTOR pathway, and consciously controlling autophagy can improve the anti-HCC efficacy of a combination of PTL and ATO. In short, our conclusion represents a novel promising approach to the treatment of HCC.

Cytotoxicity and genotoxicity effects of arsenic trioxide on SQ20B human laryngeal carcinoma cells

This study investigates the cytotoxicity and the genotoxicity induced by arsenic trioxide As₂O₃in human laryngeal SQ20B carcinoma cell line. SQ20B cells were exposed to graded concentrations of arsenic trioxide (2 and 5μM) for 48h. Comet assay and γ-H2AX foci formation were used for measuring DNA damages, flow cytometry was used to identify cell cycle alterations and apoptosis, while cell morphology was visualized using transmission electron microscopy. The results show a dose-dependent induction of DNA damages and double strand breaks, alterations in cell cycle and morphologic alterations of cells. These results prove that As₂O₃ is highly cytotoxic and genotoxic at the micromolar range ina human laryngeal carcinoma cell line.

Disruption of Mitotic Progression by Arsenic

Arsenic is an enigmatic xenobiotic that causes a multitude of chronic diseases including cancer and also is a therapeutic with promise in cancer treatment. Arsenic causes mitotic delay and induces aneuploidy in diploid human cells. In contrast, arsenic causes mitotic arrest followed by an apoptotic death in a multitude of virally transformed cells and cancer cells. We have explored the hypothesis that these differential effects of arsenic exposure are related by arsenic disruption of mitosis and are differentiated by the target cell's ability to regulate or modify cell cycle checkpoints. Functional p53/CDKN1A axis has been shown to mitigate the mitotic block and to be essential to induction of aneuploidy. More recent preliminary data suggest that microRNA modulation of chromatid cohesion also may play a role in escape from mitotic block and in generation of chromosomal instability. Other recent studies suggest that arsenic may be useful in treatment of solid tumors when used in combination with other cytotoxic agents such as cisplatin.

Chalcone derivatives inhibit human platelet aggregation and inhibit growth in human bladder cancer cells

In an effort to develop potent cyclooxygenase-1 (COX-1) inhibitors used as anticancer agent, a series of 2',5'-dimethoxychalcones was screened to evaluate their antiplatelet effect on human washed platelets suspension. Compound 2 exhibited potent inhibition of human washed platelet aggregation induced by collagen, significantly inhibited collagen- and arachidonic acid-induced thromboxane B2 release, and revealed inhibitory effect on COX-1 activity. Molecular docking studies showed that 1, 2, and 4 were bound in the active site of COX-1. These indicated that the antiplatelet effect of these compounds were mainly mediated through the suppression of COX-1 activity and reduced the thromboxane formation. To investigate the mechanistic action of COX-1 inhibitor enhanced the cytotoxic effect against human bladder cancer cells, NTUB1, we assessed the cytotoxic effect of 2 against NTUB1. Treatment of NTUB1 cells with various concentrations of 2 led to a concentration-dependent increase of cell death and decrease of reactive oxygen species levels. The flow-cytometric analysis showed that 2 induced a G1 phase cell cycle arrest but did not accompany an appreciable sub-G1 phase in NTUB1 cells. In addition, compound 2 increased p21 and p27 expressions and did not inhibit the expression of COX-1 in NTUB1 cells. Our results suggested that 2 enhanced cell growth inhibition or antiproliferative activity in NTUB1 cells through G1 arrest by COX-1 independent mechanism.

Lantabetulic acid derivatives induce G1 arrest and apoptosis in human prostate cancer cells

Ten new lantabetulic acid (1) derivatives 2-11 were synthesized and their cytotoxicities against human prostate cancer cells were evaluated. PC3 cells treated with 10 μM 8 exhibited the most potent G1 phase arrest. In addition, 10 μM 8 markedly decreased the levels of cyclin E and cdk2 and caused an increase in the p21 and p27 levels, while 20 μM 8 mainly led to cell death through the apoptotic pathway, which correlated with an increase in reactive oxygen species levels, decreased expression levels of Bcl-2 and caspase-8, the induction of mitochondrial changes, and decreased levels of cytochrome c in mitochondria. The dual action of 8 could provide a new approach for the development of chemotherapeutic drugs.

Inhibitory effect of As2O3 combined with adenovirus carrying IκBαM on proliferation of liver cancer cells in vitro and in vivo

AIM: To analyze the inhibitory effect of arsenic trioxide (As₂O₃) combined with adenovirus carrying IκBαM (Ad-IκBαM) on proliferation of liver cancer cells in vitro and in vivo.

METHODS: The effect of As₂O₃ combined with Ad-IκBαM on liver cancer cell growth was assessed by MTT assay. Wistar rats were treated with diethylnitrosamine (DENA) for about 16 wk to induce liver cancer. The index of apoptosis was assessed by TUNEL assay.

RESULTS: As₂O₃ induced cellular toxicity in a dose- and time-dependent fashion in SMMC-7721 cells. MTT assay showed that the proliferation of SMMC-7721 cells was most significantly suppressed by As₂O₃ at a dose of 16 µmol/L, and the reduced rate of cell proliferation was 17.7% ± 5.3%, 40.7% ± 2.5% and 62.8% ± 5.4% at 48, 72 and 96 h, respectively. The reduced rate of cell proliferation at 72 and 96 h in cells treated with 16 µmol/L As₂O₃ and Ad-IκBαM was 68.3% ± 2.1% and 81.9% ± 3.0%, significantly higher than those in other groups (all P < 0.01). DENA treatment successfully induced tumors in rats at week 16. There was no significant difference in life span of liver cancer-bearing rats among each group. TUNEL assay demonstrated that treatment with As₂O₃ and Ad-IκBαM greatly enhanced apoptotic cell death.

CONCLUSION: Ad-IκBαM has a synergistic effect with As₂O₃ in inhibiting liver cancer cell proliferation in vitro and in vivo.

Role of arsenic trioxide in the treatment of malignant tumors of the digestive system

Arsenic trioxide (As₂O₃), also named arsenic, is a main ingredient of numerous traditional Chinese herbal recipes and has a long history of clinical application. It has positive anticancer effects and is effective in treating acute promyelocytic leukemia without toxic and side effects. As₂O₃ can induce apoptosis of cancer cells. In recent years, it has been found that As₂O₃ has an apoptosis-promoting effect on tumor cells in many human solid tumors, including liver cancer. Many in vitro and in vivo studies using digestive tract tumor cell lines or animal model have found that As₂O₃ can induce apoptosis and inhibit growth of digestive tract cancer cells. Therefore, As₂O₃ may have an important role in the prevention of malignant tumors of the digestive system. In this article, we discuss the possible cellular and molecular mechanisms by which As₂O₃ induces apoptosis of digestive tract cancer cells.

Cytotoxic and antioxidant constituents from Garcinia subelliptica

Two new triterpenoids, garcinielliptones Q (1) and S (3), and a new phloroglucinol, garcinielliptone R (2), were isolated from the seed of Garcinia subelliptica. Their structures were established by analysis of their spectroscopic data. Phloroglucinol, garcinielliptone FC (4) from this plant exhibited a significant increase of antiproliferative effect, while 4 combined with cisplatin significantly caused decrease of cell inhibition induced by cisplatin in NTUB1. Exposure of NTUB1 cells to 4 cotreated with cisplatin for significantly decreased the amount of reactive oxygen species (ROS) than that of the total amount generated by 4 and cisplatin. These results suggested that 4 could protect the cisplatin toxicity through reduction of ROS in NTUB1. Phloroglucinols, garcinielliptones, A (5) and F (7), and garsubelline A (6), from this plant, revealed ABTS radical cation scavenging activity and 5 displayed an inhibitory effect on xanthine oxidase. These finding showed that 5-7 may be used as antioxidants.

Camalexin induces apoptosis in T-leukemia Jurkat cells by increased concentration of reactive oxygen species and activation of caspase-8 and caspase-9

Camalexin, a major indole phytoalexin of Arabidopsis thaliana, accumulates in various cruciferous plants in response to environmental stress and reportedly displays antimicrobial activities against various plant pathogens. However, its cytotoxicity against eukaryotic cells and potential as a prospective drug for human diseases has been examined only in a limited context. Our data demonstrate the time- and concentration-dependent cytotoxicity of camalexin on human T-leukemia Jurkat cells in the micromolar range, and the lower potency of cytotoxic effects on human lymphoblasts and primary fibroblasts. Cytotoxicity of camalexin is enhanced by the glutathione-depleting agent buthionine sulfoximine and completely blocked by pan-caspase inhibitor Z-VAD-FMK. Treatment of Jurkat cells with camalexin resulted in activation of caspase-8, caspase-9, caspases-3/7, and apoptosis that was detected by the presence of a sub-G1 population of cells, externalization of phosphatidyl serine and decreased mitochondrial membrane potential. Staining with 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium bromide displayed increased concentration of reactive oxygen species (ROS) early in camalexin-treated Jurkat cells, prior to the onset of apoptosis, while staining with MitoSOX(™) dye identified mitochondria as a source of increased ROS. Our data suggest that this phytochemical, which has a wide range of predicted pharmacological activities, induces apoptosis in Jurkat leukemia cells through increased ROS followed by dissipation of mitochondrial membrane potential and execution of caspase-9- and caspase-8-initiated apoptosis. This is, to the best of our knowledge, the first report on antileukemic activity and mode of action of this unique indole phytoalexin.

Antioxidant xanthone derivatives induce cell cycle arrest and apoptosis and enhance cell death induced by cisplatin in NTUB1 cells associated with ROS

In an effort to develop novel antioxidant as anticancer agents, a series of xanthones were prepared. In vitro screening, the synthetic xanthones revealed significant inhibitory effects on xanthine oxidase and ABTS radical-cation scavenging activity. The selective compounds 2 and 8 induced an accumulation of NTUB1 cells in the G(1) phase arrest and cellular apoptosis by the increase of ROS level. The combination of cisplatin and 2 significantly enhanced the cell death in NTUB1 cells. Compounds 2 and 8 did not show cytotoxic activity in selected concentrations against SV-HUC1 cells. The present results suggested that antioxidants 2 and 8 may be used as anticancer agent for enhancing the therapeutic efficacy of anticancer agents and to reduce their side effect.

Xanthine oxidase inhibitory triterpenoid and phloroglucinol from guttiferaceous plants inhibit growth and induced apoptosis in human NTUB1 cells through a ROS-dependent mechanism

A known triterpenoid, β-amyrin (1), and a known and a new phloroglucinol, cohulupone (2) and garcinielliptone P (3), were isolated from the pericarp and heartwood and seed of Garcinia subelliptica, respectively. A new xanthonolignoid, hyperielliptone HF (4), was isolated from the heartwood of Hypericum geminiflorum. The new compounds were established by analysis of their spectroscopic data. Compounds 1-3 showed an inhibitory effect on xanthine oxidase (XO). Treatment of NTUB1, a human bladder cancer cell, with 1 or 1 cotreated with cisplatin for 24 h resulted in a decreased viability of cells. Exposure of NTUB1 to 1 or 1 cotreated with cisplatin for 24 h significantly increased the level of production of reactive oxygen species (ROS). Flow cytometric analysis indicated that treatment of NTUB1 with 1 or 1 cotreated with cisplatin led to the cell cycle arrest, accompanied by an increase in the extent of apoptotic cell death in 1 or 1 combined with cisplatin-treated NTUB1 after 24 h. These data suggested that the presentation of cell cycle arrest and apoptosis in 1 or 1 combined with cisplatin-treated NTUB1 for 24 h was mediated through an increased amount of ROS in cells exposed to 1 or 1 cotreated with cisplatin.

Xanthine oxidase inhibitory terpenoids of Amentotaxus formosana protect cisplatin-induced cell death by reducing reactive oxygen species (ROS) in normal human urothelial and bladder cancer cells

The diterpenoids (+)-ferruginol (1), ent-kaur-16-en-15-one (2), ent-8(14),15-sandaracopimaradiene-2α,18-diol (3), 8(14),15-sandaracopimaradiene-2α,18,19-triol (4), and (+)-sugiol (5) and the triterpenoids 3β-methoxycycloartan-24(24(1))-ene (6), 3β,23β-dimethoxycycloartan-24(24(1))-ene (7), 3β,23β-dimethoxy-5α-lanosta-24(24(1))-ene (8), and 23(S)-23-methoxy-24-methylenelanosta-8-en-3-one (9), isolated from Amentotaxus formosana, showed inhibitory effects on xanthine oxidase (XO). Of the compounds tested, compound 5 was a potent inhibitor of XO activity, with an IC(50) value of 6.8±0.4 μM, while displaying weak ABTS radical cation scavenging activity. Treatment of the bladder cancer cell line, NTUB1, with 3-10 μM of compound 5 and 10 μM cisplatin, and immortalized normal human urothelial cell line, SV-HUC1, with 0.3-1 μM and 10-50 μM of compound 5 and 10 μM cisplatin, respectively, resulted in increased viability of cells compared with cytotoxicity induced by cisplatin. Treatment of NTUB1 with 20 μM cisplatin and 10 or 30 μM of compound 5 resulted in decreased ROS production compared with ROS production induced by cisplatin. These results indicate that 10 or 30 μM of compound 5 in NTUB1 cells may mediate through the suppression of XO activity and reduction of reactive oxygen species (ROS) induced by compound 5 cotreated with 20 μM cisplatin and protection of subsequent cell death.

Hypertension, diuretics and antihypertensives in relation to bladder cancer

The aim of this study is to investigate the relationships between hypertension, hypertension medication and bladder cancer risk in a population-based case-control study conducted in Los Angeles. Non-Asians between the ages of 25 and 64 years with histologically confirmed bladder cancers diagnosed between 1987 and 1996 were identified through the Los Angeles County Cancer Surveillance Program. A total of 1585 cases and their age-, gender- and race-matched neighborhood controls were included in the analyses. Conditional logistic regression models were used to examine the relationship between history of hypertension, medication use and bladder cancer risk. A history of hypertension was not related to bladder cancer; however, among hypertensive individuals, there was a significant difference in bladder cancer risk related to the use of diuretics or antihypertensive drugs (P for heterogeneity = 0.004). Compared with individuals without hypertension, hypertensive individuals who regularly used diuretics/antihypertensives had a similar risk [odds ratio (OR) 1.06; 95% confidence interval (CI) 0.86-1.30], whereas untreated hypertensive subjects had a 35% reduction in risk (OR: 0.65; 95% CI: 0.48-0.88). A greater reduction in bladder cancer risk was observed among current-smokers (OR: 0.43; 95% CI: 0.27-0.71) and carriers of GSTM1-null (homozygous absence) genotypes (OR: 0.43; 95% CI: 0.22-0.85). Similarly, among smokers with GSTM1-null genotype, levels of 4-aminobiphenyl-hemoglobin adducts were significantly lower among untreated hypertensive individuals (45.7 pg/g Hb) compared with individuals without hypertension (79.8 pg/g Hb) (P = 0.009). In conclusion, untreated hypertension was associated with a reduced risk of bladder cancer.

Ling-Zhi polysaccharides potentiate cytotoxic effects of anticancer drugs against drug-resistant urothelial carcinoma cells

The combined effects of ling-zhi polysaccharide fraction 3 (LZP-F3) and anticancer drugs (cisplatin and arsenic trioxide) were examined in three human urothelial carcinoma (UC) cells (parental, NTUB1; cisplatin-resistant, N/P(14); and arsenic-resistant, N/As(0.5)). MTT assay and median-effect analysis revealed that LZP-F3 could profoundly reverse the chemosensitivity of N/P(14) and N/As(0.5) to cisplatin and arsenic, respectively, in a dose-dependent manner, which involved activation of p38 and down-regulation of Akt and XPA. A dose of 10 mug/mL of LZP-F3 induced significant G1 arrest in N/P(14) and N/As(0.5) cells by flow cytometry, which may be mediated by the induction of p21(WAF1/CIP1). The combination of LZP-F3 and arsenic trioxide produced a significant synergistic growth inhibition of NTUB1 and N/As(0.5) cells. Similar results were also found in N/P(14) cells. These molecular events of combined effects involved significant and earlier induction of Fas, caspase 3 and 8 activation, Bax and Bad up-regulation, Bcl-2 and Bcl-x(L) down-regulatuion, and cytochrome c release.

Antitumor effect and mechanisms of arsenic trioxide on subcutaneously implanted human gastric cancer in nude mice

We sought to investigate the efficacy of arsenic trioxide (As(2)O(3)) against a human gastric cell line implanted in nude mice in vivo, as well as the mechanism involved. The solid tumor model was created in nude mice with the gastric cancer cell line SGC-7901. The animals were randomly divided into three groups. As(2)O(3) was injected into animals in two arsenic-treated groups (2.5 mg/kg and 5 mg/kg), and the same volume of saline solution was injected into the control group. The inhibitory effect was observed in every group. Apoptotic cells and apoptotic bodies were observed by transmission electron microscope; the fraction of apoptotic cells was detected by TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) under laser confocal technology. The expression of Fas and FasL was detected by immunohistochemical staining. In nude mice, after treatment with 5 mg/kg and 2.5 mg/kg As(2)O(3), approximately 50% and 30% tumor growth inhibition were observed, respectively (P < 0.05 for both treatment groups). Increase in apoptotic cells and apoptotic bodies appeared in As(2)O(3)-treated tumors compared with the control group. The fluorescence intensity levels of apoptotic cells in tumor were significantly higher in the arsenic-treated groups (P < 0.05 for both treatment groups). The fluorescence intensity level of apoptotic cells in the 5-mg/kg group was higher than that in the 2.5-mg/kg group (P < 0.05). The expression of Fas protein increased in dose- and time-dependent manner after the treatment with As(2)O(3), but that of FasL protein showed no significant difference between control and treated groups. As(2)O(3) did not induce hepatic and renal system injury in the nude mice. As(2)O(3) can inhibit the growth of human gastric cell implanted tumor. We ascribe this to upregulation of Fas, which can induce apoptosis of gastric cells.

Transcriptional up-regulation of SOD1 by CEBPD: a potential target for cisplatin resistant human urothelial carcinoma cells

Bladder cancer is the fourth most common type of cancer in men (ninth in women) in the United States. Cisplatin is an effective agent against the most common subtype, urothelial carcinoma. However, the development of chemotherapy resistance is a severe clinical problem for the successful treatment of this and other cancers. A better understanding of the cellular and molecular events in response to cisplatin treatment and the development of resistance are critical to improve the therapeutic options for patients. Here, we report that expression of the CCAAT/enhancer binding protein delta (CEBPD, C/EBPdelta, NF-IL6beta) is induced by cisplatin in the human bladder urothelial carcinoma NTUB1 cell line and is specifically elevated in a cisplatin resistant subline. Expression of CEBPD reduced cisplatin-induced reactive oxygen species (ROS) and apoptosis in NTUB1 cells by inducing the expression of Cu/Zn-superoxide dismutase (SOD1) via direct promoter transactivation. Several reports have implicated CEBPD as a tumor suppressor gene. This study reveals a novel role for CEBPD in conferring drug resistance, suggesting that it can also be pro-oncogenic. Furthermore, our data suggest that SOD inhibitors, which are already used as anti-angiogenic agents, may be suitable for combinatorial chemotherapy to prevent or treat cisplatin resistance in bladder and possibly other cancers.

Terpenoids induce cell cycle arrest and apoptosis from the stems of Celastrus kusanoi associated with reactive oxygen species

Bioguided fractionation of the CHCl(3) extracts obtained from Celastrus kusanoi stems led to isolation of two new terpenoids, 3beta-hydroxy-11,14-oxo-abieta-8,12-diene (1) and 3beta-trans-(3,4-dihydroxycinnamoyloxy)-11alpha-methoxy-12-ursene (2), and four known compounds characterized by spectroscopic methods. Compounds 1 and 2 and known triterpenoid erythrodiol (3) exhibited cytotoxic activity against bladder cancer cells (NTUB1) with IC(50) values of 58.2 +/- 2.3, 160.1 +/- 60.9, and 18.3 +/- 0.5 microM, respectively. Exposure of NTUB1 to 3 (5 and 10 microM) for 24 h significantly increased the level of production of reactive oxygen species (ROS). Flow cytometric analysis showed that treatment of NTUB1 with 3 led to the cell cycle arrest at G0/G1 accompanied by an increase in the extent of apoptotic cell death after 24 h. These data suggest that the presentation of G1 phase arrest and apoptosis in 3-treated NTUB1 for 24 h was mediated through an increased amount of ROS in cells exposed to 3.

Arsenic exposure predicts bladder cancer survival in a US population

PURPOSE

Chronic arsenic exposure at levels found in US drinking water has been associated with bladder cancer. While arsenic is a known carcinogen, recent studies suggest that it is useful as a therapeutic agent for leukemia. This study examined the relationship between arsenic exposure and bladder cancer mortality.

METHODS

We studied 832 cases of bladder cancer diagnosed in New Hampshire from a population-based case-control study. Individual exposure to arsenic was determined in home drinking water using ICP-MS and in toenail samples by instrumental neutron activation analysis.

RESULTS

Among the high arsenic exposure group, found using toenail arsenic level or arsenic consumption, cases experienced a de-escalated survival hazard ratio (HR) [high (> or =75 percent) versus low (<25th percentile) toenail arsenic overall survival HR 0.5 (95% CI 0.4-0.8)], controlled for tumor stage, grade, gender, age and treatment regimen. This association was found largely among invasive tumors, in smokers and was not modified by TP53 status. Bladder cancer cause-specific survival showed a similar trend, but did not reach statistical significance [HR 0.5 (95% CI 0.3-1.1)].

CONCLUSIONS

Arsenic exposure may be related to the survival of patients with bladder cancer.

Ursolic acid derivatives induce cell cycle arrest and apoptosis in NTUB1 cells associated with reactive oxygen species

Twenty-three ursolic acid (1) derivatives 2-24 including nine new 1 derivatives 5, 7-11, 20-22 were synthesized and evaluated for cytotoxicities against NTUB1 cells (human bladder cancer cell line). Compounds 5 and 17 with an isopropyl ester moiety at C-17-COOH and a succinyl moiety at C-3-OH showed potent inhibitory effect on growth of NTUB1 cells. Compounds 23 and 24 with seco-structures prepared from 1 also showed the increase of the cytotoxicity against NTUB1 cells. Exposure of NTUB1 to 5 (40 microM) and 23 (20 and 50 microM) for 24h significantly increased the production of reactive oxygen species (ROS) while exposure of NTUB1 to 5 (20 and 40 microM) and 23 (20 and 50 microM) for 48 h also significantly increased the production of ROS while exposure of cells to 17 did not increase the amount of ROS. Flow cytometric analysis exhibited that treatment of NTUB1 with 5 or 17 or 23 led to the cell cycle arrest accompanied by an increase in apoptotic cell death after 24 or 48 h. These data suggest that the presentation of G1 phase arrest and apoptosis in 5- and 23-treated NTUB1 for 24 h mediated through increased amount of ROS in cells exposed with 5 and 23, respectively, while the presence of G2/M arrest before accumulation of cells in sub-G1 phase in 5-treated cells for 48 h also due to increased amount of ROS in cells exposed with 5. The inhibition of tubulin polymerization and cell cycle arrest at G2/M following by apoptosis presented in the cell cycle of 23 also mediates through the increase amount of ROS induced by treating NTUB1 with 23 for 48 h.

Arsenic trioxide mutational spectrum analysis in the mouse lymphoma assay

It has been well documented that long-term exposure to inorganic arsenic induces cancers and vascular diseases in a dose-response relationship. Nevertheless, arsenic has also demonstrated to have anticancer activity; thus, arsenic trioxide (ATO, As2O3) is an inorganic trivalent arsenic form, currently used in the treatment against acute promyelocytic leukaemia (APL). The open discussion about how arsenic compounds induce genotoxic damage has moved us to evaluate the mutational spectrum induced by ATO in mouse lymphoma cells. Thus, 49 Tk-/- mutant colonies obtained in the mouse lymphoma assay (MLA), after treatments lasting for 4h with 10microM ATO, and 49 spontaneous mutant colonies from independent untreated cultures, were used to analyse and to characterise the mutational spectrum induced by this arsenic compound, to understand its mechanism of action. RT-PCR analysis of Tk cDNA and PCR amplifications of eight selected microsatellite sequences, located on chromosome 11, were used to carry out this screening. Our results show that, in mouse lymphoma cells, ATO is a strong clastogenic compound inducing large deletions, at chromosomal level, covering the Tk gene, as well as other regions of chromosome 11.

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

We have previously reported that As(2)O(3) affected cell cycle progression and cyclins D1 and B1 expression in two glioma cell lines differing in p53 status (U87MG-wt; T98G-mutated). In the present study, we further demonstrated that As(2)O(3) affected proliferation, viability and apoptosis of the two cell lines in a dose- and time-dependent manner, and T98G cells were more sensitive than U87MG cells to As(2)O(3) -induced apoptosis and inhibition of proliferation and viability. We further investigated the expression profiles of genes related with apoptosis and cell cycle in the two cell lines with a human cDNA-microarray (SuperArray) spotted with 267 genes of apoptosis and cell cycle. Thirty five genes were upregulated and 15 genes downregulated at least 2-fold by As(2)O(3) in U87-MG cells; whereas, 38 genes were upregulated and 21 genes downregulated at least 2-fold in T98G cells by As(2)O(3). After As(2)O(3) treatment, p53 expression was upregulated 56.5-fold in T98G cells, but only 6.0-fold in U87MG cells. The results indicate that As(2)O(3) suppresses the growth of U87MG cells mainly by regulating expression of genes of cell cycle arrest, stress and toxicity; whereas As(2)O(3) affects T98G cells mainly by regulating expression of genes belonging to Bcl-2, tumor necrotic factor receptor and ligand families. The data may be helpful for optimizing As(2)O(3) as an anti-cancer drug in the treatment of gliomas.

Opposing effects of arsenic trioxide on hepatocellular carcinomas in mice

Arsenic trioxide (As2O3) is a potent antitumor agent used to treat acute promyelocytic leukemia (APL) and, more recently, solid tumors. However, the dose of As2O3 required to suppress human xenographs in mice is markedly higher than that used to treat APL in humans. Paradoxically, low doses of As2O3 stimulate angiogenesis, which might be expected to promote tumor growth. Clearly, appropriate dosages of As2O3 are required to treat human patients to avoid toxicity and undesirable side effects. In the present study, we investigated As2O3 with respect to its toxicity and effects on tumor growth, angiogenesis and cell apoptosis using H22 hepatocellular carcinoma (HCC) cells in a mouse model of HCC. As2O3 inhibited tumor growth and angiogenesis, and enhanced tumor cell apoptosis at doses greater than 1 mg/kg, but mice lost weight and failed to thrive at doses of 4 mg/kg and greater. In contrast, low doses (<1 mg/kg) of As2O3 promoted tumor growth, upregulated the expression of vascular endothelial growth factor and tumor angiogenesis, and had no effect on tumor cell apoptosis. In vitro studies demonstrated that As2O3 inhibited the proliferation of H22 tumor cells and bovine aortic endothelial cells, and induced their apoptosis in a dose- and time-dependent fashion, suggesting that the mechanism of As2O3-mediated inhibition of tumor growth is due to direct effects of the drug on both tumor cells and endothelia. In summary, different doses of As2O3 have opposing effects on tumor growth and angiogenesis. The results demonstrate that As2O3 has a narrow window of therapeutic opportunity with respect to dosage, and that low doses of the drug as used in metronomic therapy should be used with extreme caution.

Arsenic trioxide synergizes with B7H3-mediated immunotherapy to eradicate hepatocellular carcinomas

Arsenic trioxide (As(2)O(3)), a valuable anticancer drug for the treatment of acute promyelocytic leukemia, may also have therapeutic potential for the treatment of solid tumors. However, its therapeutic efficacy against solid tumors is lacking even at high dosages. Other therapeutic strategies are required to enhance the efficacy of As(2)O(3) against solid tumors such as hepatocellular carcinoma (HCC), which is refractory to chemotherapy. B7H3, a new member of the B7 family, has been shown to induce antitumor immunity. Intratumoral injection of B7H3 plasmids eradicates small EL-4 lymphomas, but monotherapy is ineffective against large tumors. Here we investigated whether As(2)O(3) would synergize with B7H3 immunotherapy to combat HCC. Large subcutaneous H22 HCCs (0.7-0.8 cm in diameter) established in BALB/c mice were rapidly and completely eradicated when intratumoral administration of As(2)O(3) was preceded by in situ gene transfer of B7H3. In contrast, neither As(2)O(3) nor B7H3 monotherapy was effective. The antitumor activity of As(2)O(3) was attributed to increased tumor-cell apoptosis, perhaps as a result of direct cytotoxicity as well as decreased tumor angiogenesis. Combination therapy generated potent systemic antitumor immunity mediated by CD8(+) and NK cells that was effective in combating a systemic challenge of 1 x 10(7) parental H22 cells. It led to the simultaneous and complete regression of multiple distant tumor nodules, concomitant with increased levels of serum IFN-gamma and cytotoxic T lymphocyte (CTL) activity. In conclusion, combining B7H3-mediated immunotherapy with As(2)O(3) warrants investigation as a therapeutic strategy to combat HCC, and other malignancies.

Arsenic trioxide: an anti cancer missile with multiple warheads

The proven efficacy of ATO in the treatment of APL and the emerging importance of ATO in other diseases prompted extensive studies of the mechanisms of action of ATO in APL and in other types of cancers. In this review we will focus on downstream events in ATO-induced intrinsic and extrinsic apoptotic pathways with an emphasis on the role of pro-apoptotic and anti-apoptotic proteins and the role of p53 in ATO-induced apoptosis including its effect on cell cycle, its anti-mitotic effect and the role of apoptosis inducing factors (AIF) in ATO-induced apoptosis, chromatin condensation and nuclear fragmentation in myeloma cells as a model.

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

PURPOSE

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

METHODS AND MATERIALS

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

RESULTS

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

CONCLUSIONS

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

Characterization of molecular events in a series of bladder urothelial carcinoma cell lines with progressive resistance to arsenic trioxide

Our previous studies have shown that arsenic trioxide (As2O3), a novel anti-cancer agent, may be active against urothelial carcinomas. A series of bladder urothelial carcinoma cells with progressive As2O3 resistance were established and studied to reveal molecular events in relation to the mechanisms of resistance to As2O3. A sensitive parental line (NTUB1) and three As2O3-resistant sublines (NTUB1/As) were used with their IC50s being 0.9, 1.2, 2.5 and 4.9 microM, respectively. Cellular resistance to As2O3 was associated with a lowered proliferation profile (increased p53 and p21Waf1/Cip1 and decreased c-Myc levels) and a greater resistance to apoptosis (elevated Bcl-2 levels). Cells with a stronger resistance had higher expressions of superoxide dismutase (Cu/Zn) and hMSH2 (but not hMLH1). GSH contents were up-regulated in resistant cells in a dose-dependent manner. The DNA-binding activities of NF-kappaB and AP-1 were down-regulated in resistant cells in a dose-dependent manner. Profound molecular alterations occur during the acquisition of secondary As2O3 resistance. Our in vitro cellular model may help to reveal resistance mechanisms to As2O3 in bladder urothelial carcinoma cells.

Reverse Effects of Tetraarsenic Oxide on the Angiogenesis Induced by Nerve Growth Factor in the Rat Cornea

To compare the antiangiogenic effects of tetraarsenic oxide (As4O6) with those of diarsenic oxide (As2O3) in the rat cornea, rat cornea micropocket assay was conducted to induce angiogenesis by implantation of the pellet contained 1.0 ng of nerve growth factor (NGF). Ten of thirty eyes of Sprague-Dawley rats were randomly assigned to one of three groups, namely, control group (no medication), As2O3 group (50 mg/kg As2O3, PO, s.i.d.), and As4O6 group (50 mg/kg As4O6, PO, s.i.d.). After implantation, the number of new vessels, vessel length and clock hour of neovascularization were examined under the microscope from day 3 to day 7. The area of neovascularization was calculated using a mathematical formula. Although new vessels in control and As2O3 groups were first noticed at day 3, whereas those of As4O6 group were first observed on day 5. The number, length, clock hour of neovascularization and areas of the vessels in As4O6 group showed more significant inhibition than those of control and As2O3 groups from day 5 (P<0.05). However, there were no differences in all parameters between control group and As2O3 group during the entire study period. These results showed that As4O6 had antiangiogenic effects on the new vessels induced by NGF in the rat cornea.

Antitumor effect of arsenic trioxide in murine xenograft model

Arsenic trioxide, As(2)O(3) (ATO), has been established to be an effective agent for treating acute promyelocytic leukemia, but its effect on solid tumors has not been fully explored. In the present study in a murine xenograft system, we found that ATO significantly inhibited tumor growth of the inoculated human hepatocellular carcinoma cell line HuH7 when administered either intravenously or intratumorally. Pathological examination revealed that ATO induced extensive cell death in the tumor. Some of the dead cells in intratumorally ATO-treated mice showed characteristic features of apoptosis, such as nuclear condensation and fragmentation, and were TUNEL-positive. The measurement of arsenic by using particle induced X-ray emission revealed that arsenic was accumulated more in the tumor than in brain, kidney or liver after the intravenous injection of ATO, which is consistent with the hemorrhagic cell death observed in ATO-treated tumor tissues. Thus, ATO appears to have potential for the treatment of solid tumors, as well as hematopoietic malignancies.

Synergistic effect of cell differential agent-II and arsenic trioxide on induction of cell cycle arrest and apoptosis in hepatoma cells

AIM: To illustrate the possible role of cell differential agent-II (CDA-II) in the apoptosis of hepatoma cells induced by arsenic trioxide (As₂O₃).

METHODS: Hepatoma cell lines BEL-7402 and HepG2 were treated with As₂O₃ together with CDA-II. Cell surviving fraction was determined by MTT assay; morphological changes were observed by immunofluorescence staining of Hoechst 33258; and cell cycle and the apoptosis index were determined by flow cytometry (FCM).

RESULTS: Cytotoxity of CDA-II was low. Nevertheless, CDA-II could strongly potentiate arsenic trioxide-induced apoptosis. At 1.0 g/L CDA-II, IC₅₀ of As₂O₃ in hepatoma cell lines was reduced from 5.0 µmol/L to 1.0 µmol/L (P < 0.01). The potentiation of apoptosis was dependent on the dosage of CDA-II. FCM indicated that in hepatoma, cell growth was inhibited by CDA-II at lower concentrations (< 2.0 g/L) primarily by arresting at S and G₂ phase, and at higher concentrations (> 2.0 g/L) apoptotic cell and cell cycle arresting at G₁ phase increased proportionally. The combination of two drugs led to much higher apoptotic rates, as compared with the either drug used alone.

CONCLUSION: CDA-II can strongly potentiate As₂O₃-induced apoptosis in hepatoma cells, and two drugs can produce a significant synergic effect.

Metvan: a novel oxovanadium(IV) complex with broad spectrum anticancer activity

Among the 25 bis(cyclopentadienyl)vanadium(IV) and 14 oxovanadium(IV) compounds synthesised and evaluated for anticancer activity, bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(IV) (metvan) was identified as the most promising multitargeted anticancer vanadium complex with apoptosis-inducing activity. At nanomolar and low micromolar concentrations, metvan induces apoptosis in human leukaemia cells, multiple myeloma cells and solid tumour cells derived from breast cancer, glioblastoma, ovarian, prostate and testicular cancer patients. It is highly effective against cisplatin-resistant ovarian cancer and testicular cancer cell lines. Metvan is much more effective than the standard chemotherapeutic agents dexamethasone and vincristine in inducing apoptosis in primary leukaemia cells from patients with acute lymphoblastic leukaemia, acute myeloid leukaemia or chronic acute myeloid leukaemia. Metvan-induced apoptosis is associated with a loss of mitochondrial transmembrane potential, the generation of reactive oxygen species and depletion of glutathione. Treatment of leukaemia cells from acute lymphoblastic leukaemia, acute myeloid leukaemia and chronic acute myeloid leukaemia patients with metvan inhibits the constitutive expression as well as the gelatinolytic activities of matrix metalloproteinase-9 and -2. Treatment of human malignant glioblastoma and breast cancer cells with metvan at concentrations > 1 microM is associated with a nearly complete loss of the adhesive, migratory and invasive properties of the treated cancer cell populations. Metvan shows favourable pharmacokinetics in mice and does not cause acute or subacute toxicity at the dose levels tested (12.5 - 50 mg/kg). Therapeutic plasma concentrations > or = 5 microM, which are highly cytotoxic against human cancer cells, can be rapidly achieved and maintained in mice for at least 24 h after intraperitoneal bolus injection of a single 10 mg/kg non-toxic dose of metvan. Metvan exhibits significant antitumour activity, delays tumour progression and prolongs survival time in severe combined immunodeficient mouse xenograft models of human malignant glioblastoma and breast cancer. The broad spectrum anticancer activity of metvan together with favourable pharmacodynamic features and lack of toxicity warrants further development of this oxovanadium compound as a new anticancer agent. Metvan could represent the first vanadium complex as an alternative to platinum-based chemotherapy.

Cytotoxicity of arsenic trioxide to transitional carcinoma cells

OBJECTIVES

To explore the therapeutic efficacy of arsenic trioxide (As2O3) in human transitional cell carcinomas, we investigated the potential use of the compound as a chemotherapeutic agent and the possible cross-resistance with cisplatin in this malignancy.

METHODS

Three bladder transitional carcinoma cell lines, NTUB1, NTUB1/P (cisplatin-resistant), and NTUB1/As (As2O3-resistant), were used. The chemosensitivity of the three cell lines to cisplatin and As2O3 was determined by the microculture tetrazolium assay. The modulatory effect of buthionine sulfoximine (BSO) on As2O3 cytotoxicity was studied by combining the two agents simultaneously or sequentially and evaluated using the median-effect analysis. Cellular glutathione contents were determined using a biochemical method.

RESULTS

There was evident cross-resistance between cisplatin and As2O3 in the cell model used. BSO significantly enhanced As2O3 cytotoxicity in the three cell lines, indicating synergism in combination. In the presence of 3 microM BSO, the sensitivity of NTUB1, NTUB1/P, and NTUB1/As to As2O3 was increased 3, 7.4, and 8.4-fold, respectively. Among the three different combination schedules, greater cytotoxic effects were obtained by concurrent exposure to both agents. A significant dose-response relationship was found between the BSO concentrations and glutathione contents in NTUB1 (P = 0.007) and NTUB1/As (P = 0.05) but not NTUB1/P (P = 0.1) cells.

CONCLUSIONS

As2O3 in the presence of BSO may be an active agent against transitional cell carcinoma. Our results have clinical implications and warrant further investigation.