Increased oxidative stress created by adenoviral MnSOD or CuZnSOD plus BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) inhibits breast cancer cell growth

Antioxidant Enzymes and Their Potential Use in Breast Cancer Treatment

According to the World Health Organization (WHO), breast cancer (BC) is the deadliest and the most common type of cancer worldwide in women. Several factors associated with BC exert their effects by modulating the state of stress. They can induce genetic mutations or alterations in cell growth, encouraging neoplastic development and the production of reactive oxygen species (ROS). ROS are able to activate many signal transduction pathways, producing an inflammatory environment that leads to the suppression of programmed cell death and the promotion of tumor proliferation, angiogenesis, and metastasis; these effects promote the development and progression of malignant neoplasms. However, cells have both non-enzymatic and enzymatic antioxidant systems that protect them by neutralizing the harmful effects of ROS. In this sense, antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), thioredoxin reductase (TrxR), and peroxiredoxin (Prx) protect the body from diseases caused by oxidative damage. In this review, we will discuss mechanisms through which some enzymatic antioxidants inhibit or promote carcinogenesis, as well as the new therapeutic proposals developed to complement traditional treatments.

SOD2, a Potential Transcriptional Target Underpinning CD44-Promoted Breast Cancer Progression

CD44, a cell-adhesion molecule has a dual role in tumor growth and progression; it acts as a tumor suppressor as well as a tumor promoter. In our previous work, we developed a tetracycline-off regulated expression of CD44's gene in the breast cancer (BC) cell line MCF-7 (B5 clone). Using cDNA oligo gene expression microarray, we identified SOD2 (superoxide dismutase 2) as a potential CD44-downstream transcriptional target involved in BC metastasis. SOD2 gene belongs to the family of iron/manganese superoxide dismutase family and encodes a mitochondrial protein. SOD2 plays a role in cell proliferation and cell invasion via activation of different signaling pathways regulating angiogenic abilities of breast tumor cells. This review will focus on the findings supporting the underlying mechanisms associated with the oncogenic potential of SOD2 in the onset and progression of cancer, especially in BC and the potential clinical relevance of its various inhibitors.

Astaxanthin from shrimp efficiently modulates oxidative stress and allied cell death progression in MCF-7 cells treated synergistically with β-carotene and lutein from greens

This study investigated the synergistic efficacy of keto-carotenoid astaxanthin (AST, from shrimp) plus hydrocarbon (β-carotene, BC) and hydroxyl (lutein, L) carotenoids (from greens) on molecular events in MCF-7 cells. MCF-7 cells were treated with either of carotenoid (20 μM, AST or BC or L) separately or the mixture of them (an equimolar concentration of carotenoids mixture, CM) or saponified carotenoid extract from shrimp (SSCE) for 48 h and analyzed cellular uptake, cytotoxicity, and apoptosis. The IC₅₀ and combination-index values of AST co-treatment with a lower concentration of BC and L (5 μM) exhibited enhanced cytotoxicity and oxidative stress as compared with individual carotenoids or SSCE. Further, higher cellular uptake/accumulation of AST along with BC and L found to synergistically induce apoptosis through modulation of cyclin D1, p53, Bax and Bcl-2 expressions by arresting cell cycle at G0/G1 phase. Further, CM or SSCE treatments are unlikely to affect proliferation of normal breast epithelial cells (MCF-10A). The results of selective killing of MCF-7 cells demonstrated a greater insight on the synergistic effect of shrimp AST plus BC and L. It is concluded that consumption of shrimp along with green leafy vegetables helps in combating cancer chemoprevention.

The role of thioredoxin reductase and glutathione reductase in plumbagin-induced, reactive oxygen species-mediated apoptosis in cancer cell lines

Plumbagin is a secondary metabolite that was first identified in the Plumbago genus of plants. It is a naphthoquinone compound with anti-atherosclerosis, anticancer, anti-inflammatory, antimicrobial, contraceptive, cardiotonic, immunosuppressive, and neuroprotective activities. However, the mechanisms of plumbagin's activities are largely unknown. In this study, we examined the effect of plumbagin on HepG2 hepatocellular carcinoma cells as well as LLC lung cancer cells, SiHa cervical carcinoma cells. Plumbagin significantly decreased HepG2 cell viability in a dose-dependent manner. Additionally, treatment with plumbagin significantly increased the Bax/Bcl-2 ratio and caspase-3/7 activity. Using the similarity ensemble approach (SEA)-a state-of-the-art cheminformatic technique-we identified two previously unknown cellular targets of plumbagin: thioredoxin reductase (TrxR) and glutathione reductase (GR). This was then confirmed using protein- and cell-based assays. We found that plumbagin was directly reduced by TrxR, and that this reduction was inhibited by the TrxR inhibitor, sodium aurothiomalate (ATM). Plumbagin also decreased the activity of GR. Plumbagin, and the GR inhibitor sodium arsenite all increased intracellular reactive oxygen species (ROS) levels and this increase was significantly attenuated by pretreatment with the ROS scavenger N-acetyl-cysteine (NAC) in HepG2 cells. Plumbagin increased TrxR-1 and heme oxygenase (HO)-1 expression and pretreatment with NAC significantly attenuated the plumbagin-induced increase of TrxR-1 and HO-1 expression in HepG2 cells, LLC cells and SiHa cells. Pretreatment with NAC significantly prevented the plumbagin-induced decrease in cell viability in these cell types. In conclusion, plumbagin exerted its anticancer effect by directly interacting with TrxR and GR, and thus increasing intracellular ROS levels.

Downregulation of hPMC2 imparts chemotherapeutic sensitivity to alkylating agents in breast cancer cells

Triple negative breast cancer cell lines have been reported to be resistant to the cyotoxic effects of temozolomide (TMZ). We have shown previously that a novel protein, human homolog of Xenopus gene which Prevents Mitotic Catastrophe (hPMC2) has a role in the repair of estrogen-induced abasic sites. Our present study provides evidence that downregulation of hPMC2 in MDA-MB-231 and MDA-MB-468 breast cancer cells treated with temozolomide (TMZ) decreases cell survival. This increased sensitivity to TMZ is associated with an increase in number of apurinic/apyrimidinic (AP) sites in the DNA. We also show that treatment with another alkylating agent, BCNU, results in an increase in AP sites and decrease in cell survival. Quantification of western blot analyses and immunofluorescence experiments reveal that treatment of hPMC2 downregulated cells with TMZ results in an increase in γ-H2AX levels, suggesting an increase in double strand DNA breaks. The enhancement of DNA double strand breaks in TMZ treated cells upon downregulation of hPCM2 is also revealed by the comet assay. Overall, we provide evidence that downregulation of hPMC2 in breast cancer cells increases cytotoxicity of alkylating agents, representing a novel mechanism of treatment for breast cancer. Our data thus has important clinical implications in the management of breast cancer and brings forth potentially new therapeutic strategies.

Differential effects of superoxide dismutase and superoxide dismutase/catalase mimetics on human breast cancer cells

Reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (H2O2) have been implicated in development and progression of breast cancer. In the present study, we have evaluated the effects of the superoxide dismutase (SOD) mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 on superoxide and H2O2 formation as well as proliferation, adhesion, and migration of MCF-7 and MDA-MB-231 cells. Superoxide and H2O2 production was examined using dihydroethidium and Amplex red assays, respectively. Cell viability and adhesion were measured using a tetrazolium-based MTT assay. Cell proliferation was determined using trypan blue assay. Cell cycle progression was analyzed using flow cytometry. Clonal expansion of a single cell was performed using a colony formation assay. Cell migration was measured using transwell migration assay. Dual luciferase assay was used to determine NF-κB reporter activity. EUK 134 effectively reduced both superoxide and H2O2, whereas MnTmPyP removed superoxide but enhanced H2O2 formation. EUK 134 effectively attenuated viability, proliferation, clonal expansion, adhesion, and migration of MCF-7 and MDA-MB-231 cells. In contrast, MnTmPyP only reduced clonal expansion of MCF-7 and MDA-MB-231 cells but had no effect on adhesion and cell cycle progression. Tumor necrosis factor-alpha-induced NF-κB activity was reduced by EUK 134, whereas MnTmPyP enhanced this activity. These data indicate that the SOD mimetic MnTmPyP and the SOD/catalase mimetic EUK 134 exert differential effects on breast cancer cell growth. Inhibition of H2O2 signaling using EUK 134-like compound might be a promising approach to breast cancer therapy.

[Correlation between drinking behavior and polymorphisms of extracellular superoxide dismutase, aldehyde dehydrogenase 2 genes, and oral squamous cell carcinoma]

OBJECTIVE

To investigate the correlation between drinking behavior and polymorphism combination of extracellular superoxide dismutase (EC-SOD) and aldehyde dehydrogenase 2 (ALDH2) genes and oral squamous cell carcinoma.

METHODS

The genetic polymorphisms of EC-SOD and ALDH2 were analyzed by polymorphism-polymerase chain reaction technique in peripheral blood leukocytes of 750 oral squamous cell carcinoma cases and 750 non-cancer controls.

RESULTS

The frequencies of EC-SOD (C/G) and ALDH2 variant genotypes were 38.27% and 69.47% in oral squamous cell carcinoma cases and 21.07% and 44.40% in healthy controls, respectively. Statistical tests showed significant difference in the frequencies between the two groups (P < 0.01). The risk of oral squamous cell carcinoma with EC-SOD (C/G) was significantly higher than that of controls (OR = 2.32). Individuals carrying ALDH2 variant genotypes had high risk of oral squamous cell carcinoma (OR = 2.85). Combined analysis of the polymorphisms showed that percentages of EC-SOD (C/G)/ALDH2 variant genotypes in oral squamous cell carcinoma and control groups were 30.67% and 6.80%, respectively (P < 0.01). Individuals carrying EC-SOD (C/G)/ALDH2 variant genotypes had high risk of oral squamous cell carcinoma (OR = 8.13). The drinking rate of the case group was significantly higher than that in the control group (OR = 2.70). Statistical analysis suggested an interaction between drinking and EC-SOD (C/G) and ALDH2 variant genotypes, which increase risk of oral squamous cell carcinoma (OR = 25.00).

CONCLUSION

EC-SOD (C/G) and ALDH2 variant genotypes and drinking are the risk factors in oral squamous cell carcinoma, which could carry out a coordinated attack of oral squamous cell carcinoma.

Manganese superoxide dismutase in cancer prevention

SIGNIFICANCE

Cancer is the second leading cause of death in the United States. Considering the quality of life and treatment cost, the best way to fight against cancer is to prevent or suppress cancer development. Cancer is preventable as indicated by human papilloma virus (HPV) vaccination and tamoxifen/raloxifen treatment in breast cancer prevention. The activities of superoxide dismutases (SODs) are often lowered during early cancer development, making it a rational candidate for cancer prevention.

RECENT ADVANCES

SOD liposome and mimetics have been shown to be effective in cancer prevention animal models. They've also passed safety tests during early phase clinical trials. Dietary supplement-based SOD cancer prevention provides another opportunity for antioxidant-based cancer prevention. New mechanistic studies have revealed that SOD inhibits not only oncogenic activity, but also subsequent metabolic shifts during early tumorigenesis.

CRITICAL ISSUES

Lack of sufficient animal model studies targeting specific cancers; and lack of clinical trials and support from pharmaceutical industries also hamper efforts in further advancing SOD-based cancer prevention.

FUTURE DIRECTIONS

To educate and obtain support from our society that cancer is preventable. To combine SOD-based therapeutics with other cancer preventive agents to obtain synergistic effects. To formulate a dietary supplementation-based antioxidant approach for cancer prevention. Lastly, targeting specific populations who are prone to carcinogens, which can trigger oxidative stress as the mechanism of carcinogenesis.

The tumor microenvironment: characterization, redox considerations, and novel approaches for reactive oxygen species-targeted gene therapy

The tumor microenvironment is a complex system that involves the interaction between malignant and neighbor stromal cells embedded in a mesh of extracellular matrix (ECM) components. Stromal cells (fibroblasts, endothelial, and inflammatory cells) are co-opted at different stages to help malignant cells invade the surrounding ECM and disseminate. Malignant cells have developed adaptive mechanisms to survive under the extreme conditions of the tumor microenvironment such as restricted oxygen supply (hypoxia), nutrient deprivation, and a prooxidant state among others. These conditions could be eventually used to target drugs that will be activated specifically in this microenvironment. Preclinical studies have shown that modulating cellular/tissue redox state by different gene therapy (GT) approaches was able to control tumor growth. In this review, we describe the most relevant features of the tumor microenvironment, addressing reactive oxygen species-generating sources that promote a prooxidative microenvironment inside the tumor mass. We describe different GT approaches that promote either a decreased or exacerbated prooxidative microenvironment, and those that make use of the differential levels of ROS between cancer and normal cells to achieve tumor growth inhibition.

Expression of ovotransferrin enhances tolerance of yeast cells toward oxidative stress

Recently, we found that ovotransferrin (OTf) undergoes distinct self-cleavage in a redox-dependent process and exhibited in vitro superoxide dismutase (SOD)-like activity. In this study, we explore that the expression of OTf confers high tolerance to oxidative stress in yeast cells. The OTf gene was cloned into the vector pPICZB and was successfully expressed in methylotrophic yeast, Pichia pastoris KM71H. There was no growth difference between the non-transformed strain and recombinant strains harboring a mock vector (pPICZB) or the OTf gene carrying a vector (OTf-pPICZB). Intracellularly expressed OTf was found to undergo self-cleavage, producing a major fragment of 15 kDa, which corresponded to the disulfide kringle domain of the N-terminal lobe. The yeast OTf transformants exhibited strong tolerance to oxidative stress induced by either hydrogen peroxide (H₂O₂) or diethyl maleate (DEM). Further, OTf transformants showed higher intracellular reducing capacity and enhanced cytosolic reductase activity. This study is the first to describe the ability of OTf to confer in vivo antioxidative stress function within a complicated milieu of eukaryotic cells and provide novel insights for the potential of the OTf gene for molecular breeding of industrial yeast strains with high tolerance to oxidative stress.

Anticancer activity of Acacia nilotica (L.) Wild. Ex. Delile subsp. indica against Dalton's ascitic lymphoma induced solid and ascitic tumor model

The aim of the present investigation was to evaluate the effect of A. nilotica extract against Dalton's ascitic lymphoma (DAL) induced solid and ascitic tumors in BALB/c mice. Experimental animals received A. nilotica extract (10 mg/kg.bw) intraperitoneally for 10 and 14 consecutive days before induction of solid and ascitic tumors, respectively. Treatment with A. nilotica extract significantly decreased the development of tumor and percentage increase in body weight when compared to DAL induced solid tumor control group, also increasing the life span, restoring the total white blood cell count and hemoglobin content and significantly decreasing the levels of serum aspartate transaminase (SGPT), alanine transaminase (SGOT), alkaline phosphatase (ALP), gamma glutamyl transferase (GGT) and nitric oxide (NO) when compared to DAL induced ascitic tumor controls. The treatment also reduced significantly the cellular glutathione (GSH) and nitric oxide levels in treated animals. Histopathological studies also confirmed protective influence. The outcome of the present work indicates that A. nilotica extract could be used as natural anticancer agent for human health.

Inhibitors of hydroperoxide metabolism enhance ascorbate-induced cytotoxicity

Pharmacological ascorbate, via its oxidation, has been proposed as a pro-drug for the delivery of H(2)O(2) to tumors. Pharmacological ascorbate decreases clonogenic survival of pancreatic cancer cells, which can be reversed by treatment with scavengers of H(2)O(2). The goal of this study was to determine if inhibitors of intracellular hydroperoxide detoxification could enhance the cytotoxic effects of ascorbate. Human pancreatic cancer cells were treated with ascorbate alone or in combination with inhibitors of hydroperoxide removal including the glutathione disulfide reductase inhibitor 1,3 bis (2-chloroethyl)-1-nitrosurea (BCNU), siRNA targeted to glutathione disulfide reductase (siGR), and 2-deoxy-D-glucose (2DG), which inhibits glucose metabolism. Changes in the intracellular concentration of H(2)O(2) were determined by analysis of the rate of aminotriazole-mediated inactivation of endogenous catalase activity. Pharmacological ascorbate increased intracellular H(2)O(2) and depleted intracellular glutathione. When inhibitors of H(2)O(2) metabolism were combined with pharmacological ascorbate the increase in intracellular H(2)O(2) was amplified and cytotoxicity was enhanced. We conclude that inclusion of agents that inhibit cellular peroxide removal produced by pharmacological ascorbate leads to changes in the intracellular redox state resulting in enhanced cytotoxicity.

Manganese superoxide dismutase regulates a metabolic switch during the mammalian cell cycle

Proliferating cells consume more glucose to cope with the bioenergetics and biosynthetic demands of rapidly dividing cells as well as to counter a shift in cellular redox environment. This study investigates the hypothesis that manganese superoxide dismutase (MnSOD) regulates cellular redox flux and glucose consumption during the cell cycle. A direct correlation was observed between glucose consumption and percentage of S-phase cells in MnSOD wild-type fibroblasts, which was absent in MnSOD homozygous knockout fibroblasts. Results from electron paramagnetic resonance spectroscopy and flow cytometric assays showed a significant increase in cellular superoxide levels in S-phase cells, which was associated with an increase in glucose and oxygen consumption, and a decrease in MnSOD activity. Mass spectrometry results showed a complex pattern of MnSOD-methylation at both lysine (68, 89, 122, and 202) and arginine (197 and 216) residues. MnSOD protein carrying a K89A mutation had significantly lower activity compared with wild-type MnSOD. Computational-based simulations indicate that lysine and arginine methylation of MnSOD during quiescence would allow greater accessibility to the enzyme active site as well as increase the positive electrostatic potential around and within the active site. Methylation-dependent changes in the MnSOD conformation and subsequent changes in the electrostatic potential around the active site during quiescence versus proliferation could increase the accessibility of superoxide, a negatively charged substrate. These results support the hypothesis that MnSOD regulates a "metabolic switch" during progression from quiescent through the proliferative cycle. We propose MnSOD as a new molecular player contributing to the Warburg effect.

Clair DK. Manganese superoxide dismutase: beyond life and death

Manganese superoxide dismutase (MnSOD) is a nuclear-encoded antioxidant enzyme that localizes to the mitochondria. Expression of MnSOD is essential for the survival of aerobic life. Transgenic mice expressing a luciferase reporter gene under the control of the human MnSOD promoter demonstrate that the level of MnSOD is reduced prior to the formation of cancer. Overexpression of MnSOD in transgenic mice reduces the incidences and multiplicity of papillomas in a DMBA/TPA skin carcinogenesis model. However, MnSOD deficiency does not lead to enhanced tumorigenicity of skin tissue similarly treated because MnSOD can modulate both the p53-mediated apoptosis and AP-1-mediated cell proliferation pathways. Apoptosis is associated with an increase in mitochondrial levels of p53 suggesting a link between MnSOD deficiency and mitochondrial-mediated apoptosis. Activation of p53 is preventable by application of a SOD mimetic (MnTE-2-PyP(5+)). Thus, p53 translocation to mitochondria and subsequent inactivation of MnSOD explain the observed mitochondrial dysfunction that leads to transcription-dependent mechanisms of p53-induced apoptosis. Administration of MnTE-2-PyP(5+) following apoptosis but prior to proliferation leads to suppression of protein carbonyls and reduces the activity of AP-1 and the level of the proliferating cellular nuclear antigen, without reducing the activity of p53 or DNA fragmentation following TPA treatment. Remarkably, the incidence and multiplicity of skin tumors are drastically reduced in mice that receive MnTE-2-PyP(5+) prior to cell proliferation. The results demonstrate the role of MnSOD beyond its essential role for survival and suggest a novel strategy for an antioxidant approach to cancer intervention.

D-4F, an apoA-I mimetic peptide, inhibits proliferation and tumorigenicity of epithelial ovarian cancer cells by upregulating the antioxidant enzyme MnSOD

We recently reported that apoA-I and apoA-I mimetic peptides prevent the development of flank tumors in immunocompetent C57BL/6J mice. To delineate the mechanism(s) of action of apoA-I mimetic peptides in tumor development, we examined the effect of D-4F (an apoA-I mimetic peptide) on the antioxidant status and on the gene expression and function of antioxidant enzymes in ID8 cells (a mouse epithelial ovarian cancer cell line) and in a mouse model. We demonstrate that D-4F treatment significantly reduces the viability and proliferation of ID8 cells, with a concomitant improvement of the antioxidant status of ID8 cells as measured by lipid peroxidation, protein carbonyl, superoxide anion, and hydrogen peroxide levels. D-4F treatment induces MnSOD (but not CuZnSOD) mRNA, protein, and activity. Inhibition of MnSOD in ID8 cells using shRNA vectors abrogates the inhibitory effects of D-4F on ID8 cell viability and proliferation. Moreover, tumor development from ID8 cells carrying shRNA for MnSOD were unaffected by D-4F treatment. Our results suggest that the inhibitory effects of D-4F on ID8 cell proliferation and tumor development are mediated, at least in part, by the induced expression and activity of MnSOD.

Enhanced expression of mitochondrial superoxide dismutase leads to prolonged in vivo cell cycle progression and up-regulation of mitochondrial thioredoxin

Mn superoxide dismutase (MnSOD) is an important mitochondrial antioxidant enzyme, and elevated MnSOD levels have been shown to reduce tumor growth in part by suppressing cell proliferation. Studies with fibroblasts have shown that increased MnSOD expression prolongs cell cycle transition time in G1/S and favors entrance into the quiescent state. To determine if the same effect occurs during tissue regeneration in vivo, we used a transgenic mouse system with liver-specific MnSOD expression and a partial hepatectomy paradigm to induce synchronized in vivo cell proliferation during liver regeneration. We show in this experimental system that a 2.6-fold increase in MnSOD activity leads to delayed entry into S phase, as measured by reduction in bromodeoxyuridine (BrdU) incorporation and decreased expression of proliferative cell nuclear antigen (PCNA). Thus, compared to control mice with baseline MnSOD levels, transgenic mice with increased MnSOD expression in the liver have 23% fewer BrdU-positive cells and a marked attenuation of PCNA expression. The increase in MnSOD activity also leads to an increase in the mitochondrial form of thioredoxin (thioredoxin 2), but not in several other peroxidases examined, suggesting the importance of thioredoxin 2 in maintaining redox balance in mitochondria with elevated levels of MnSOD.

Neutrophil oxidative metabolism in Down syndrome patients with congenital heart defects

Down syndrome (DS) occurs when an individual has three, rather than two, copies of the 21st chromosome. Cytosolic superoxide dismutase (SOD-1) is encoded by a gene on chromosome 21 and thus, SOD-1 activity is elevated in patients with DS. Forty percent of all cases with DS are associated with congenital heart defects (CHD). Although the contribution of SOD1 to disease phenotype is unknown, it is considered to be a "molecular marker" of the disease. It was hypothesized herein that the presence of CHD may alter the expression of SOD1 and oxidative metabolism in patients with DS. This hypothesis was tested via four experimental groups as follows: patients with DS without CHD, DS patients with CHD, CHD patients without DS and controls. Expression and activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), myeloperoxidase (MPO), and catalase (CAT) were determined in neutrophils from all experimental groups. Intracellular hydrogen peroxide concentration and superoxide release were also evaluated in neutrophils. A significant increase was observed in SOD and GPx amount and activity in patients with DS with and without CHD. No significant difference was found in the amount and activity of MPO and CAT among the different experimental groups. Intracellular hydrogen peroxide concentration was similar in all groups, whereas a prominent decrease was seen in superoxide release in cases with DS. Patients with DS with and without CHD showed no significant differences in any of the measured parameters. The data suggest that CHD observed in patients with DS does not result from altered redox metabolism associated with the disease.

Proline analogue of nitrosourea as a new cytotoxic prodrug

Carmustine is frequently used as anticancer drug. High toxicity and low selectivity reduces the application of this drug. Though, there is a necessity to find new compounds characterized by similar therapeutic effects but a higher selectivity and safety. As a result, the proline analogue of nitrosourea, N-[N'-(2-bromophenyl)-N'-nitrosocarbamoyl]proline (AC), has been synthesized. The aim of this study was to compare the influence of carmustine and the proline analogue of nitrosourea on the antioxidant abilities of fibroblasts and leukemia cells, MOLT4. It was shown that carmustine as well as AC cause an increase in hydrogen peroxide concentration in normal and neoplastic cells. Incubation with both compounds led to a diminution of the activity of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and reductase. Changes in activity / level of antioxidant parameters were accompanied by augmentation of lipid and oxidative protein modifications. In conclusion, carmustine and AC cause changes in the antioxidative system of normal and MOLT4 cells and are a reason of oxidative stress formation.

Overexpression of extracellular superoxide dismutase attenuates heparanase expression and inhibits breast carcinoma cell growth and invasion

Increased expression of heparanase stimulates the progression of various human cancers, including breast cancer. Therefore, a deeper understanding of the mechanisms involved in regulating heparanase is critical in developing effective treatments for heparanase-overexpressing cancers. In this study, we investigated the potential use of extracellular superoxide dismutase (EcSOD) to enhance the inhibitory effects of heparin/low molecular weight heparin (LMWH) in breast cancer cells. EcSOD binds to cell surfaces and the extracellular matrix through heparin-binding domain (HBD). Deleting this HBD rendered the protein a more potent inhibitor of breast cancer growth, survival, and invasion. Among the treatment combinations examined, EcSODDeltaHBD plus LMWH provided the best tumor suppressive effects in inhibiting breast cancer growth and invasion in vitro. We have further shown that overexpression of EcSOD decreased accumulation of vascular endothelial growth factor in the culture medium and increased the level of intact cell surface-associated heparan sulfate, thus implicating inhibition of heparanase expression as a potential mechanism. Overexpression of EcSOD inhibited steady-state heparanase mRNA levels by >50% as determined by quantitative reverse transcription-PCR. Moreover, heparanase promoter activation was suppressed by EcSOD as indicated by a luciferase reporter assay. These findings reveal a previously unrecognized molecular pathway showing that regulation of heparanase transcription can be mediated by oxidative stress. Our study implies that overexpression of EcSOD is a promising strategy to enhance the efficacy of heparin/LMWH by inhibiting heparanase as a novel treatment for breast cancer.

Activity of lactate dehydrogenase and superoxide dismutase in the circulation of patients with breast carcinoma

Background: A rapid increase in the turnover of malignant cells modulates the enzymes level in circulation and may be a prognostic sign of disease progression. We evaluated the activity of serum lactate dehydrogenase and superoxide dismutase in erythrocytes of breast cancer patients immediately after surgery and before adjuvant therapy. Methods: Fourteen newly operated breast cancer patients were included in the study. Lactate dehydrogenase and superoxide dismutase activity were estimated using standard tests for evaluation of enzyme activity. Results: Activity of lactate dehydrogenase was in normal range in all but one sample obtained from patient at clinical status IIIB. Superoxide dismutase activity was elevated in 11 out of 14 patients, and was 2 to 8 fold higher compare to control values. The highest activity of superoxide dismutase was found in samples of two patients at clinical status I. Conclusion: Determination of lactate dehydrogenase and superoxide dismutase activity might be useful in clinical follow up of breast cancer patients.