Modulation of skin tumorigenesis by SOD

Grass carp superoxide dismutases exert antioxidant function and inhibit autophagy to promote grass carp reovirus (GCRV) replication

Superoxide dismutases (SODs) are potent antioxidants crucial for neutralizing reactive oxygen species (ROS) and protecting organisms from oxidative damage. In this study, we successfully cloned and analyzed two SOD genes, CiSOD1 and CiSOD2, from grass carp (Ctenopharyngodon idellus). CiSOD1 consists of two CuZn signature motifs and two conserved cysteine residues, while CiSOD2 contains a single Mn signature motif. The expression of CiSODs was found to be ubiquitous across all examined tissues, with their expression levels significantly altered after stimulation by grass carp reovirus (GCRV) or pathogen-associated molecular patterns (PAMPs). CiSOD1 was observed to be uniformly distributed in the cytoplasm, whereas CiSOD2 localized in the mitochondria. Escherichia coli transformed with both CiSODs demonstrated enhanced host resistance to H2O2 and heavy metals. Additionally, purified recombinant CiSOD proteins effectively protected DNA against oxidative damage. Furthermore, overexpression of CiSODs in fish cells reduced intracellular ROS, inhibited autophagy, and then resulted in the promotion of GCRV replication. Knockdown of CiSODs showed opposite trends. Notably, these roles of CiSODs in autophagy and GCRV replication were reversed upon treatment with an autophagy inducer. In summary, our findings suggest that grass carp SODs play an important role in decreasing intracellular ROS levels, inhibiting autophagy, and subsequently promoting GCRV replication.

Yüzme Egzersizi Yaptırılan Farelere Alfa-Lipoik Asit Uygulamasının Lipid Peroksidasyon, Kreatin Kinaz ve Laktat Düzeyleri Üzerine Etkisinin İncelenmesi*

Özet Amaç: Bu çalışmada, yüzme egzersizi yaptırılan farelere alfa-lipoik asit (ALA) uygulamasının lipit peroksidasyon, kreatin kinaz ve laktat düzeyleri üzerine etkisi incelendi. Gereç ve Yöntemler: Çalışmada 20-25 gr ağırlığında, 30 adet Swiss albino cinsi fare kullanıldı. Fareler kontrol, ALA- 50 ve ALA-100 şeklinde her grupta 10 adet olacak şekilde 3 gruba ayrıldı. Kontrol grubuna 10 gün boyunca intraperitoneal (i.p.) izotonik serum uygulandı. ALA gruplarına ise 10 gün boyunca i.p. yol ile sırasıyla 50 ve 100 mg/kg konsantrasyonlarda ALA uygulandı. Onuncu günün sonunda fareler yüzme havuzlarına alınarak test edildi. Yüzme testi sonrası farelerin kas ve kan örnekleri alınarak biyokimyasal olarak incelendi. Bulgular: Elde edilen veriler kontrol grubu ile karşılaştırıldığında ALA uygulanan grupların yüzme süresi, GSH, GSH-Px ve SOD seviyelerinde artış, CK, LDH ve MDA değerlerinde ise azalma olduğu görüldü. Sonuç: Sonuç olarak akut tüketici yüzme egzersizi yaptırılan farelerin kas dokusundaki hasarın varlığı biyokimyasal olarak tespit edilmiştir. ALA uygulamalarının tüketici yüzme egzersizinin oluşturduğu oksidatif hasarın engellenmesinde ve kas yorgunluğunun geciktirilmesinde etkili olabileceği kanısına varıldı.

UVB-induced inactivation of manganese-containing superoxide dismutase promotes mitophagy via ROS-mediated mTORC2 pathway activation

Mitochondria are major sites of energy metabolism that influence numerous cellular events, including immunity and cancer development. Previously, we reported that the mitochondrion-specific antioxidant enzyme, manganese-containing superoxide dismutase (MnSOD), has dual roles in early- and late-carcinogenesis stages. However, how defective MnSOD impacts the chain of events that lead to cell transformation in pathologically normal epidermal cells that have been exposed to carcinogens is unknown. Here, we show that UVB radiation causes nitration and inactivation of MnSOD leading to mitochondrial injury and mitophagy. In keratinocytes, exposure to UVB radiation decreased mitochondrial oxidative phosphorylation, increased glycolysis and the expression of autophagy-related genes, and enhanced AKT Ser/Thr kinase (AKT) phosphorylation and cell growth. Interestingly, UVB initiated a prosurvival mitophagy response by mitochondria-mediated reactive oxygen species (ROS) signaling via the mammalian target of the mTOR complex 2 (mTORC2) pathway. Knockdown of rictor but not raptor abrogated UVB-induced mitophagy responses. Furthermore, fractionation and proximity-ligation assays reveal that ROS-mediated mTOC2 activation in mitochondria is necessary for UVB-induced mitophagy. Importantly, pretreatment with the MnSOD mimic MnTnBuOE-2-PyP⁵⁺ (MnP) attenuates mTORC2 activation and suppresses UVB-induced mitophagy. UVB radiation exposure also increased cell growth as assessed by soft-agar colony survival and cell growth assays, and pretreatment with MnP or the known autophagy inhibitor 3-methyladenine abrogated UVB-induced cell growth. These results indicate that MnSOD is a major redox regulator that maintains mitochondrial health and show that UVB-mediated MnSOD inactivation promotes mitophagy and thereby prevents accumulation of damaged mitochondria.

Enzymatic antioxidants and its role in oral diseases

Antioxidants are substances that when present at very low concentration inhibits the oxidation of a molecule. It has the capacity to nullify the ill effects of oxidation caused by free radicals in the living organisms. The unpaired electrons of these free radicals are highly reactive and neutralize the harmful reactions of human metabolism. Protection of the body against free radicals is provided by some enzymes which come under a distinctive group, concerned solely with the detoxification of these radicals. Superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase are the key enzymatic antioxidants of this defense system by which the free radicals that are produced during metabolic reactions are removed. This review highlights the mechanism of action of enzymatic antioxidants SOD, GPX and catalase and its role in oral disease.

SOD2 immunoexpression predicts lymph node metastasis in penile cancer

BACKGROUND

Superoxide dismutase-2 (SOD2) is considered one of the most important antioxidant enzymes that regulate cellular redox state in normal and tumorigenic cells. Overexpression of this enzyme in lung, gastric, colorectal, breast cancer and cervical cancer malignant tumors has been observed. Its relationship with inguinal lymph node metastasis in penile cancer is unknown.

METHODS

SOD2 protein expression levels were determined by immunohistochemistry in 125 usual type squamous cell carcinomas of the penis from a Brazilian cancer center. The casuistic has been characterized by means of descriptive statistics. An exploratory logistic regression has been proposed to evaluate the independent predictive factors of lymph node metastasis.

RESULTS

SOD2 expression in more than 50% of cells was observed in 44.8% of primary penile carcinomas of the usual type. This expression pattern was associated with lymph node metastasis both in the uni and multivariate analysis.

CONCLUSIONS

Our results indicate that SOD2 expression predicts regional lymph node metastasis. The potential clinical implication of this observation warrants further studies.

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.

Anti-inflammatory/antioxidant use in long-term maintenance cancer therapy: a new therapeutic approach to disease progression and recurrence

The chronic, progressive clinical characteristics of many adult solid tumor malignancies suggest that a more effective therapeutic approach to cancer management may require long-term intervention using nontoxic systemic agents that block critical components of abnormal tumor physiology. Two highly promising systemic targets common to the development, progression and recurrence of many common cancers are dysregulated inflammatory and oxidation/reduction (redox) pathways. Compelling clinical data support the use of anti-inflammatory and antioxidant agents as a therapeutic modality for long-term use in patients diagnosed with several common cancers, including colon cancer and breast cancer. The therapeutic paradigm presented in this paper is the product of a synthesis of what is currently understood about the biological effects of inflammation and oxidative stress that contribute to tumorigenesis, disease progression and recurrence as well as results obtained from research on the use of prophylactics with anti-inflammatory or antioxidant properties in cancer prevention and treatment.

Ellagic acid inhibits PKC signaling by improving antioxidant defense system in murine T cell lymphoma

Antioxidants protect the cells from the damaging effects of reactive oxygen species (ROS). Production of ROS during cellular metabolism is balanced by their removal by antioxidants. Any condition leading to increased levels of ROS results in oxidative stress, which participates in multistage carcinogenesis by causing oxidative DNA damage, mutations in the proto-oncogenes and tumor suppressor genes. Antioxidant defense system is required to overcome the process of carcinogenesis generated by ROS. Antioxidant enzymes are major contributors to endogenous antioxidant defense system. Protein kinase C (PKC) is generally involved in cell proliferation and its over expression leads to abnormal tumor growth. Out of three classes of PKC, classical PKC is mainly involved in cell proliferation and tumor growth. Classical PKC initiates signaling pathway and leads to activation of a number of downstream protein via activation of NF-κB. Therefore any agent which can promotes the endogenous antioxidant defense system should be able to down regulate PKC and NF-κB activation and thus may be useful in reducing cancer progression. To investigate this hypothesis we have tested the effect of antioxidant ellagic acid on antioxidant enzymes and PKC signaling in Dalton's lymphoma bearing (DL) mice. DL mice were treated with three different doses of ellagic acid. The treatment significantly increases the activity and expression of antioxidant enzymes and down regulates the expression of classical isozymes of PKC as well as the activation of NF-κB, indicating that ellagic acid improves antioxidant defense system and PKC signaling via NF-κB which may contribute to its cancer preventive role.

The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer

This review addresses the oncopharmacological properties of curcumin at the molecular level. First, the interactions between curcumin and its molecular targets are addressed on the basis of curcumin's distinct chemical properties, which include H-bond donating and accepting capacity of the β-dicarbonyl moiety and the phenylic hydroxyl groups, H-bond accepting capacity of the methoxy ethers, multivalent metal and nonmetal cation binding properties, high partition coefficient, rotamerization around multiple C-C bonds, and the ability to act as a Michael acceptor. Next, the in vitro chemical stability of curcumin is elaborated in the context of its susceptibility to photochemical and chemical modification and degradation (e.g., alkaline hydrolysis). Specific modification and degradatory pathways are provided, which mainly entail radical-based intermediates, and the in vitro catabolites are identified. The implications of curcumin's (photo)chemical instability are addressed in light of pharmaceutical curcumin preparations, the use of curcumin analogues, and implementation of nanoparticulate drug delivery systems. Furthermore, the pharmacokinetics of curcumin and its most important degradation products are detailed in light of curcumin's poor bioavailability. Particular emphasis is placed on xenobiotic phase I and II metabolism as well as excretion of curcumin in the intestines (first pass), the liver (second pass), and other organs in addition to the pharmacokinetics of curcumin metabolites and their systemic clearance. Lastly, a summary is provided of the clinical pharmacodynamics of curcumin followed by a detailed account of curcumin's direct molecular targets, whereby the phenotypical/biological changes induced in cancer cells upon completion of the curcumin-triggered signaling cascade(s) are addressed in the framework of the hallmarks of cancer. The direct molecular targets include the ErbB family of receptors, protein kinase C, enzymes involved in prostaglandin synthesis, vitamin D receptor, and DNA.

Modulation of MnSOD in Cancer:Epidemiological and Experimental Evidence

Since it was first observed in late 1970s that human cancers often had decreased manganese superoxide dismutase (MnSOD) protein expression and activity, extensive studies have been conducted to verify the association between MnSOD and cancer. Significance of MnSOD as a primary mitochondrial antioxidant enzyme is unquestionable; results from in vitro, in vivo and epidemiological studies are in harmony. On the contrary, studies regarding roles of MnSOD in cancer often report conflicting results. Although putative mechanisms have been proposed to explain how MnSOD regulates cellular proliferation, these mechanisms are not capitulated in epidemiological studies. This review discusses most recent epidemiological and experimental studies that examined the association between MnSOD and cancer, and describes emerging hypotheses of MnSOD as a mitochondrial redox regulatory enzyme and of how altered mitochondrial redox may affect physiology of normal as well as cancer cells.

Low-dose radiation-induced enhancement of thymic lymphomagenesis in Lck-Bax mice is dependent on LET and gender

The hypothesis that mitochondrial dysfunction and increased superoxide levels in thymocytes over expressing Bax (Lck-Bax1 and Lck-Bax38&1) contributes to lymphomagenesis after low-dose radiation was tested. Lck-Bax1 single-transgenic and Lck-Bax38&1 double-transgenic mice were exposed to single whole-body doses of 10 or 100 cGy of (137)Cs or iron ions (1,000 MeV/n, 150 keV/μm) or silicon ions (300 MeV/n, 67 keV/μm). A 10 cGy dose of (137)Cs significantly increased the incidence and onset of thymic lymphomas in female Lck-Bax1 mice. In Lck-Bax38&1 mice, a 100 cGy dose of high-LET iron ions caused a significant dose dependent acceleration of lymphomagenesis in both males and females that was not seen with silicon ions. To determine the contribution of mitochondrial oxidative metabolism, Lck-Bax38&1 over expressing mice were crossed with knockouts of the mitochondrial protein deacetylase, Sirtuin 3 (Sirt3), which regulates superoxide metabolism. Sirt3(-/-)/Lck-Bax38&1 mice demonstrated significant increases in thymocyte superoxide levels and acceleration of lymphomagenesis (P < 0.001). These results show that lymphomagenesis in Bax over expressing animals is enhanced by radiation exposure in both an LET and gender dependent fashion. These findings support the hypothesis that mitochondrial dysfunction leads to increased superoxide levels and accelerates lymphomagenesis in Lck-Bax transgenic mice.

Is it time for a new paradigm for systemic cancer treatment? Lessons from a century of cancer chemotherapy

U.S. SEER (Surveillance Epidemiology and End Results) data for age-adjusted mortality rates for all cancers combined for all races show only a modest overall 13% decline over the past 35 years. Moreover, the greatest contributor to cancer mortality is treatment-resistant metastatic disease. The accepted therapeutic paradigm for the past half-century for the treatment of advanced cancers has involved the use of systemic chemotherapy drugs cytotoxic for cycling cells (both normal and malignant) during DNA synthesis and/or mitosis. The failure of this therapeutic modality to achieve high-level, consistent rates of disease-free survival for some of the most common cancers, including tumors of the lung, colon breast, brain, melanoma, and others is the focus of this paper. A retrospective assessment of critical milestones in cancer chemotherapy indicates that most successful therapeutic regimens use cytotoxic cell cycle inhibitors in combined, maximum tolerated, dose-dense acute treatment regimens originally developed to treat acute lymphoblastic leukemia and some lymphomas. Early clinical successes in this area led to their wholesale application to the treatment of solid tumor malignancies that, unfortunately, has not produced consistent, long-term high cure rates for many common cancers. Important differences in therapeutic sensitivity of leukemias/lymphomas versus solid tumors can be explained by key biological differences that define the treatment-resistant solid tumor phenotype. A review of these clinical outcome data in the context of recent developments in our understanding of drug resistance mechanisms characteristic of solid tumors suggests the need for a new paradigm for the treatment of chemotherapy-resistant cancers. In contrast to reductionist approaches, the systemic approach targets both microenvironmental and systemic factors that drive and sustain tumor progression. These systemic factors include dysregulated inflammatory and oxidation pathways shown to be directly implicated in the development and maintenance of the cancer phenotype. The paradigm stresses the importance of a combined preventive/therapeutic approach involving adjuvant chemotherapies that incorporate anti-inflammatory and anti-oxidant therapeutics.

Dual role of the antioxidant enzyme peroxiredoxin 6 in skin carcinogenesis

The antioxidant enzyme peroxiredoxin 6 (Prdx6) is a key regulator of the cellular redox balance, particularly under stress conditions. We identified Prdx6 as an important player in different phases of skin carcinogenesis. Loss of Prdx6 in mice enhanced the susceptibility to skin tumorigenesis, whereas overexpression of Prdx6 in keratinocytes of transgenic mice had the opposite effect. The tumor-preventive effect of Prdx6, which was observed in a human papilloma virus 8-induced and a chemically induced tumor model, was not due to alterations in keratinocyte proliferation, apoptosis, or in the inflammatory response. Rather, endogenous and overexpressed Prdx6 reduced oxidative stress as reflected by the lower levels of oxidized phospholipids in the protumorigenic skin of Prdx6 transgenic mice and the higher levels in Prdx6-knockout mice than in control animals. In contrast to its beneficial effect in tumor prevention, overexpression of Prdx6 led to an acceleration of malignant progression of existing tumors, revealing a dual function of this enzyme in the pathogenesis of skin cancer. Finally, we found strong expression of PRDX6 in keratinocytes of normal human skin and in the tumor cells of squamous cell carcinomas, indicating a role of Prdx6 in human skin carcinogenesis. Taken together, our data point to the potential usefulness of Prdx6 activators or inhibitors for controlling different stages of skin carcinogenesis.

Antihyperlipidemic and antitumor effects of chickpea albumin hydrolysate

This study was undertaken to determine the effects of chickpea albumin hydrolysate (CAH) on antihyperlipidemic and antitumor functions. The antihyperlipidemic results showed that CAH exhibited a dose dependent ability to decrease the levels of serum total cholesterol, triglyceride, LDL cholesterol (LDL-C), while increasing HDL cholesterol (HDL-C). Additionally, the appearance of the hyperlipidemic livers was ameliorated significantly. The antitumor results showed that CAH administration significantly increased the tumor inhibition rate and decreased tumor volume. CAH was also able to increase the spleen index and promote spleen lymphocyte proliferation. In addition, CAH treatment led to a remarkable rise in the superoxide dismutase (SOD) activity, while dramatically decreasing malondialdehyde (MDA) in the liver. Most importantly, we found that the physical conditions, such as appetite, activity, and coat luster of the mice in the CAH test group were better than those in the tumor control (TC) and positive control (PC) groups. These results taken together indicate that CAH warrants being further investigated and developed as an adjunctive element for hepatic lipid control, as well as antitumor and hypolipidemic therapies.

Effects of Calendula Essential Oil-Based Cream on Biochemical Parameters of Skin of Albino Rats against Ultraviolet B Radiation

Reactive oxygen species (ROS) generated from UV-B radiation have the capacity to cause oxidative decomposition which leads to the formation of toxic components as well as lipid peroxidation. Considering this fact, the present study was performed to evaluate the effect of a cream (O/W) containing the essential oil of Calendula officinalis on biochemical parameters of the skin of albino rats against UV-B radiation. The fingerprint analysis of Calendula essential oil was performed by HPLC with special reference to 1,8-cineole and α-pinene. The results indicated that the treatment with creams containing 4% and 5% of Calendula essential oil caused a significant decrease in the malonyldialdehyde level, whereas the levels of catalase, glutathione, superoxide dismutase, ascorbic acid, and the total protein level were significantly increased after 1 month of daily irradiation and treatment when compared to untreated control groups. The results suggest that the cutaneous application of the essential oil of Calendula prevents UV-B-induced alterations in the level of antioxidants in skin tissue.

Manganese superoxide dismutase is a p53-regulated gene that switches cancers between early and advanced stages

Manganese superoxide dismutase (MnSOD) plays a critical role in the survival of aerobic life, and its aberrant expression has been implicated in carcinogenesis and tumor resistance to therapy. However, despite extensive studies in MnSOD regulation and its role in cancer, when and how the alteration of MnSOD expression occurs during the process of tumor development in vivo are unknown. Here, we generated transgenic mice expressing a luciferase reporter gene under the control of human MnSOD promoter-enhancer elements and investigated the changes of MnSOD transcription using the 7,12-dimethylbenz(α)anthracene (DMBA)/12-O-tetradecanoylphorbol-l3-acetate (TPA) multistage skin carcinogenesis model. The results show that MnSOD expression was suppressed at a very early stage but increased at late stages of skin carcinogenesis. The suppression and subsequent restoration of MnSOD expression were mediated by two transcription-factors, Sp1 and p53. Exposure to DMBA and TPA activated p53 and decreased MnSOD expression via p53-mediated suppression of Sp1 binding to the MnSOD promoter in normal-appearing skin and benign papillomas. In squamous cell carcinomas, Sp1 binding increased because of the loss of functional p53. We used chromatin immunoprecipitation, electrophoretic mobility shift assay, and both knockdown and overexpression of Sp1 and p53 to verify their roles in the expression of MnSOD at each stage of cancer development. The results identify MnSOD as a p53-regulated gene that switches between early and advanced stages of cancer. These findings also provide strong support for the development of means to reactivate p53 for the prevention of tumor progression.

Chemoprevention of two-stage skin cancer in vivo by Saraca asoca

Saraca asoca (Family Caesalpiniaceae) has been widely used in traditional Indian medicine especially due to its wound-healing property. The present study investigates the chemopreventive property of flavonoids from Saraca asoca (flowers) on 2-stage skin carcinogenesis in mice models. Skin cancer was induced in Swiss albino mice by single topical application of 7,12-dimethyl benzanthracene (100 µg/50 µL of acetone) followed by thrice a week treatment of croton oil for 20 weeks. The topical pretreatment of the flavonoid fraction from S asoca (FF S asoca) was 30 minutes prior to the application of croton oil thrice weekly for 20 weeks. At the end of the experimental period the animals were sacrificed, and the tumor statistics and various marker parameters were studied (enzyme assays, Western blotting). The pretreatment of the FF of S asoca caused significant reduction in the number of tumors per mouse and the percentage of tumor-bearing mice. Also, the latency period for the appearance of the first tumor was delayed by S asoca pretreatment. In plant-treated animals there was a significant increase in the levels of reduced glutathione, catalase, and protein in skin when compared with the untreated animals. Conversely, there was a significant decrease in the lipid peroxidation levels. A significant reduction in the expression of ornithine decarboxylase, a key enzyme in the promotion stage of 2-stage skin cancer, in the plant-treated group was also observed. These findings suggest the chemopreventive activity of flavonoids from S asoca on 2-stage skin carcinogenesis.

Mitochondrial oxidative stress drives tumor progression and metastasis: should we use antioxidants as a key component of cancer treatment and prevention?

The functional role of oxidative stress in cancer pathogenesis has long been a hotly debated topic. A study published this month in BMC Cancer by Goh et al., directly addresses this issue by using a molecular genetic approach, via an established mouse animal model of human breast cancer. More specifically, alleviation of mitochondrial oxidative stress, via transgenic over-expression of catalase (an anti-oxidant enzyme) targeted to mitochondria, was sufficient to lower tumor grade (from high-to-low) and to dramatically reduce metastatic tumor burden by >12-fold. Here, we discuss these new findings and place them in the context of several other recent studies showing that oxidative stress directly contributes to tumor progression and metastasis. These results have important clinical and translational significance, as most current chemo-therapeutic agents and radiation therapy increase oxidative stress, and, therefore, could help drive tumor recurrence and metastasis. Similarly, chemo- and radiation-therapy both increase the risk for developing a secondary malignancy, such as leukemia and/or lymphoma. To effectively reduce mitochondrial oxidative stress, medical oncologists should now re-consider the use of powerful anti-oxidants as a key component of patient therapy and cancer prevention. Please see related research article: http://www.biomedcentral.com/1471-2407/11/191.

Caveolin-1 and mitochondrial SOD2 (MnSOD) function as tumor suppressors in the stromal microenvironment: a new genetically tractable model for human cancer associated fibroblasts

We have recently proposed a new model for understanding tumor metabolism, termed: "The Autophagic Tumor Stroma Model of Cancer Metabolism". In this new paradigm, catabolism (autophagy) in the tumor stroma fuels the anabolic growth of aggressive cancer cells. Mechanistically, tumor cells induce autophagy in adjacent cancer-associated fibroblasts via the loss of caveolin-1 (Cav-1), which is sufficient to promote oxidative stress in stromal fibroblasts. To further test this hypothesis, here we created human Cav-1 deficient immortalized fibroblasts using a targeted sh-RNA knock-down approach. Relative to control fibroblasts, Cav-1 deficient fibroblasts dramatically promoted tumor growth in xenograft assays employing an aggressive human breast cancer cell line, namely MDA-MB-231 cells. Co-injection of Cav-1 deficient fibroblasts, with MDA-MB-231 cells, increased both tumor mass and tumor volume by ~4-fold. Immuno-staining with CD31 indicated that this paracrine tumor promoting effect was clearly independent of angiogenesis. Mechanistically, proteomic analysis of these human Cav-1 deficient fibroblasts identified > 40 protein biomarkers that were upregulated, most of which were associated with i) myofibroblast differentiation, or ii) oxidative stress/hypoxia. In direct support of these findings, the tumor promoting effects of Cav-1 deficient fibroblasts could be functionally suppressed (nearly 2-fold) by the recombinant over-expression of SOD2 (superoxide dismutase 2), a known mitochondrial enzyme that de-activates superoxide, thereby reducing mitochondrial oxidative stress. In contrast, cytoplasmic soluble SOD1 had no effect, further highlighting a specific role for mitochondrial oxidative stress in this process. In summary, here we provide new evidence directly supporting a key role for a loss of stromal Cav-1 expression and oxidative stress in cancer-associated fibroblasts, in promoting tumor growth, which is consistent with "The Autophagic Tumor Stroma Model of Cancer". The human Cav-1 deficient fibroblasts that we have generated are a new genetically tractable model system for identifying other suppressors of the cancer-associated fibroblast phenotype, via a genetic "complementation" approach. This has important implications for understanding the pathogenesis of triple negative and basal breasts cancers, as well as tamoxifen-resistance in ER+ breast cancers, which are all associated with a Cav-1 deficient "lethal" tumor micro-environment, driving poor clinical outcome.

Effects of pergolide mesylate on transduction efficiency of PEP-1-catalase protein

The low transduction efficiency of various proteins is an obstacle to their therapeutic application. However, protein transduction domains (PTDs) are well-known for a highly effective tool for exogenous protein delivery to cells. We examined the effects of pergolide mesylate (PM) on the transduction of PEP-1-catalase into HaCaT human keratinocytes and mice skin and on the anti-inflammatory activity of PEP-1-catatase against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation using Western blot and histological analysis. PM enhanced the time- and dose-dependent transduction of PEP-1-catalase into HaCaT cells without affecting the cellular toxicity. In a mouse edema model, PEP-1-catalase inhibited the increased expressions of inflammatory mediators and cytokines such as cyclooxygenase-2, inducible nitric oxide synthase, interleukin-6 and -1β, and tumor necrosis factor-α induced by TPA. On the other hand, PM alone failed to exert any significant anti-inflammatory effects. However, the anti-inflammatory effect of co-treatment with PEP-1-catalase and PM was more potent than that of PEP-1-catalase alone. Our results indicate that PM may enhance the delivery of PTDs fusion therapeutic proteins to target cells and tissues and has potential to increase their therapeutic effects of such drugs against various diseases.

Superoxide dismutase mRNA and protein level in human colorectal cancer

Impairments of antioxidant enzyme expression are often concomitant with the onset of cancer. Due to epigenetic factors causing an inflammatory state the gastrointestinal tract can become exposed to reactive oxygen species. The purpose of our work was to evaluate mRNA and protein levels of superoxide dismutase isoenzymes in human colorectal adenocarcinoma due to its clinical advancement, and in colorectal cancer liver metastases. Evaluation of SOD expression in regard to CRC advancement, seems useful for clinical applications due to different tumor cells sensitivity to reactive oxygen species based treatment. Studies were conducted on a group of 27 patients: 15 diagnosed with colorectal adenocarcinoma and 12 diagnosed with colorectal cancer liver metastases. The mRNA level was determined by RT-PCR, and protein level by Western blotting. We observed significant (P≤0.05) changes of mRNA and protein level of SOD isoenzymes in subsequent stages of colorectal adenocarcinoma advancement and in colorectal cancer liver metastases. Differences in mRNA and protein level of SOD isoenzymes in colorectal adenocarcinoma and its liver metastases indicates that SOD participate in adaptation of tumor cells to oxidative stress, and maintain certain level of ROS, necessary for appropriate cell proliferation. Expression of superoxide dismutase isoenzymes seems to be regulated not only at transcriptional level, but also posttranscriptional.

Mutations in the SOD2 promoter reveal a molecular basis for an activating protein 2-dependent dysregulation of manganese superoxide dismutase expression in cancer cells

A primary antioxidant enzyme in mitochondria, manganese superoxide dismutase (MnSOD), plays a critical role in the survival of aerobic life. It is well documented that, compared with normal cell counterparts, MnSOD level is decreased in neoplastic transformed cells but is increased in aggressive cancers. However, the underlying mechanism for the observed dysregulation of MnSOD in cancer is unknown. We have identified previously a unique set of mutations located in the promoter region of the SOD2 gene in several types of cancer cells. We found that a C-to-T transition at -102 and an insertion of A at -93 down-regulate MnSOD transcription by interrupting the formation of a single-stranded loop that is essential for a high level of promoter activity. Here, we show that the additional downstream mutation, C-to-G transversion at -38, creates a binding site for the transcription factors specificity protein 1 (Sp1) and activating protein 2 (AP-2). The promoter function is regulated by the relative levels of Sp1 and AP-2. In cytokine-induced expression of the SOD2 gene, Sp1 cooperates with a transcriptional complex containing nuclear factor-kappaB and nucleophosmin. The presence of AP-2 attenuates this induction. Our results suggest that the high level of MnSOD observed in aggressive cancer cells may be due, in part, to the absence of AP-2 transcriptional repression.

Stressed Jerusalem artichoke tubers (Helianthus tuberosus L.) excrete a protein fraction with specific cytotoxicity on plant and animal tumour cell

Wounds from Jerusalem artichoke (Helianthus tuberosus L.) tubers excrete bioactive metabolites from a variety of structural classes, including proteins. Here we describe a protein specifically active against tumour cells arising either from human, animal or plant tissues. The non-tumour animal cells or the plant callus cells are not sensitive to these excreta. The active product was only obtained after a wound-drought stress of plant tubers. The cytotoxicity varies according to the tumour cell type. For instance, some human tumour cell lines and especially the human mammary tumour cells MDA-MB-231 were shown to be very susceptible to the active product. The active agent is shown to contain an 18-kDa polypeptide with homology to a superoxide dismutase (SOD). A 28-kDa polypeptide, related to an alkaline phosphatase (AP), was shown to be tightly linked to this 18-kDa polypeptide. The excreted 28-kDa polypeptide also displayed a consensus sequence similar to the group of DING proteins, but with a smaller molecular weight. The superoxide dismutase polypeptide was shown to be involved in the antitumour activity, but the presence of smaller factors (MW<10 kDa), such as salicylic acid, can enhance this activity.

The role of a single-stranded nucleotide loop in transcriptional regulation of the human sod2 gene

Manganese superoxide dismutase (MnSOD), a mitochondrial antioxidant enzyme, is necessary for survival of aerobic life. Previously, we demonstrated that a Sp1-based promoter is essential for constitutive transcription and a NF-kappaB-based intronic enhancer is responsible for cytokine-mediated induction. Here we show that nucleophosmin (NPM), a RNA-binding protein, binds to an 11G single-stranded loop in the promoter region and serves to integrate the Sp1 and NF-kappaB responses. Disruption of the loop structure causes a reduction of both constitutive and inductive transcription due to loss of the binding motif for NPM. Interaction of NF-kappaB.NPM.Sp1 facilitated by binding of NPM to the loop structure in the promoter region appears to comprise the basic complex for the transcriptional stimulation. These results suggest a novel molecular mechanism for communication between the enhancer and the GC-rich promoter.

Protein kinase C-ERK1/2 signal pathway switches glucose depletion-induced necrosis to apoptosis by regulating superoxide dismutases and suppressing reactive oxygen species production in A549 lung cancer cells

Cells typically die by either apoptosis or necrosis. However, the consequences of apoptosis and necrosis are quite different for a whole organism. In the case of apoptosis, the cell content remains packed in the apoptotic bodies that are removed by macrophages, and thereby inflammation does not occur; during necrosis, the cell membrane is ruptured, and the cytosolic constituents are released into the extracellular space provoking inflammation. Recently, inflammation and necrosis have been suggested to promote tumor growth. We investigated the molecular mechanism underlying cell death in response to glucose depletion (GD), a common characteristic of the tumor microenvironment. GD induced necrosis through production of reactive oxygen species (ROS) in A549 lung carcinoma cells. Inhibition of ROS production by N-acetyl-L-cysteine and catalase prevented necrosis and switched the cell death mode to apoptosis that depends on mitochondrial death pathway involving caspase-9 and caspase-3 activation, indicating a critical role of ROS in determination of GD-induced cell death mode. We demonstrate that protein kinase C-dependent extracellular regulated kinase 1/2 (ERK1/2) activation also switched GD-induced necrosis to apoptosis through inhibition of ROS production possibly by inducing manganese superoxide dismutase (SOD) expression and by preventing GD-induced degradation of copper zinc SOD. Thus, these results suggest that GD-induced cell death mode is determined by the protein kinase C/ERK1/2 signal pathway that regulates MnSOD and CuZnSOD and that these antioxidants may exert their known tumor suppressive activities by inducing necrosis-to-apoptosis switch.

Manganese superoxide dismutase polymorphism and risk of skin cancer (United States)

OBJECTIVE

We assessed whether the functional V16A polymorphism in the MnSOD gene is associated with skin cancer risk.

METHODS

We conducted a nested case-control study (219 melanoma, 286 squamous cell carcinoma (SCC), and 300 basal cell carcinoma (BCC) cases, and 873 matched controls) within the Nurses' Health Study. Genotyping was performed by the 5' nuclease assay (TaqMan). We used logistic regression to model the association between the genotype and skin cancer risk.

RESULTS AND CONCLUSIONS

Overall, there was no significant association between this polymorphism and the risk of each type of skin cancer. No significant interaction was observed between this polymorphism and sunburn history and constitutional susceptibility on skin cancer risk. For interactions between intakes of alpha-carotene and beta-carotene and the MnSOD polymorphism on SCC, the inverse association of intake of either carotene with SCC risk was limited to the Val carriers, whereas no association was observed among women with the AA genotype. We observed an interaction between total vitamin C intake and the MnSOD polymorphism on melanoma risk. No interaction was observed for the intakes of other carotenoids, vitamin E, and vitamin A. Further research is needed to confirm these possible associations.

Evidence of ROS generation by mitochondria in cells with impaired electron transport chain and mitochondrial DNA damage

Mitochondrial damage is a well known cause of mitochondria-related diseases. A major mechanism underlying the development of mitochondria-related diseases is thought to be an increase in intracellular oxidative stress produced by impairment of the mitochondrial electron transport chain (ETC). However, clear evidence of intracellular free radical generation has not been clearly provided for mitochondrial DNA (mtDNA)-damaged cells. In this study, using the novel fluorescence dye, 2-[6-(4'-hydroxy)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (HPF), which was designed to detect hydroxyl radicals (*OH), intracellular free radical formation was examined in 143B cells (parental cells), 143B-rho(0) cells (mtDNA-lacking cells), 87 wt (cybrid), and cybrids of 4977-bp mtDNA deletion (common deletion) cells containing the deletion with 0%, 5%, 50% and >99% frequency (HeLacot, BH5, BH50 and BH3.12, respectively), using a laser confocal microscope detection method. ETC inhibitors (rotenone, 3-nitropropionic acid, thenoyltrifluoroacetone, antimycin A and sodium cyanide) were also tested to determine whether inhibitor treatment increased intracellular reactive oxygen species (ROS) generation. A significant increase in ROS for 143B-rho(0) cells was observed compared with 143B cells. However, for the 87 wt cybrid, no increase was observed. An increase was also observed in the mtDNA-deleted cells BH50 and BH3.12. The ETC inhibitors increased intracellular ROS in both 143B and 143B-rho(0) cells. Furthermore, in every fluorescence image, the fluorescence dye appeared localized around the nuclei. To clarify the localization, we double-stained cells with the dye and MitoTracker Red. The resulting fluorescence was consistently located in mitochondria. Furthermore, manganese superoxide dismutase (MnSOD) cDNA-transfected cells had decreased ROS. These results suggest that more ROS are generated from mitochondria in ETC-inhibited and mtDNA-damaged cells, which have impaired ETC.

Oxidative stress in the pathogenesis of skin disease

Skin is the largest body organ that serves as an important environmental interface providing a protective envelope that is crucial for homeostasis. On the other hand, the skin is a major target for toxic insult by a broad spectrum of physical (i.e. UV radiation) and chemical (xenobiotic) agents that are capable of altering its structure and function. Many environmental pollutants are either themselves oxidants or catalyze the production of reactive oxygen species (ROS) directly or indirectly. ROS are believed to activate proliferative and cell survival signaling that can alter apoptotic pathways that may be involved in the pathogenesis of a number of skin disorders including photosensitivity diseases and some types of cutaneous malignancy. ROS act largely by driving several important molecular pathways that play important roles in diverse pathologic processes including ischemia-reperfusion injury, atherosclerosis, and inflammatory responses. The skin possesses an array of defense mechanisms that interact with toxicants to obviate their deleterious effect. These include non-enzymatic and enzymatic molecules that function as potent antioxidants or oxidant-degrading systems. Unfortunately, these homeostatic defenses, although highly effective, have limited capacity and can be overwhelmed thereby leading to increased ROS in the skin that can foster the development of dermatological diseases. One approach to preventing or treating these ROS-mediated disorders is based on the administration of various antioxidants in an effort to restore homeostasis. Although many antioxidants have shown substantive efficacy in cell culture systems and in animal models of oxidant injury, unequivocal confirmation of their beneficial effects in human populations has proven elusive.

Hemoglobin induces colon cancer cell proliferation by release of reactive oxygen species

AIM: To study whether hemoglobin could amplify colon cancer cell proliferation via reactive oxygen species (ROS) production.

METHODS: Colon cancer cell line HT-29 was grown in the conventional method using RPMI1640 media. The viability of the cells was measured using the colorimetric MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay after adding hemoglobin. We determined reactive oxygen species levels to be indicators of oxidative stress in HT 29 cell lines with and without hemoglobin and/or 5-fluorouracil (5-FU), 5’-deoxy-5-fluorouridine (5-DFUR) using fluorometric dichlorofluorescin diacetate (DCFH-DA) assay.

RESULTS: Cellular proliferation was increased with hemoglobin in a concentration-dependent manner. A significant increment on ROS levels was found in HT 29 cells following hemoglobin incubation. The cytotoxic effects of 5-FU and 5-DFUR were significantly blunted by administration of hemoglobin. There was a slight increase of peroxiredoxin 1, superoxide dismutase 1 concentration according to different hemoglobin concentrations.

CONCLUSION: Hemoglobin has a cellular proliferative effect on HT-29 colon cancer cell line by production of ROS. Also, hemoglobin abates cytotoxic effects of chemotherapeutic agents such as 5-FU and 5-DFUR.

The overexpression of NADPH-producing enzymes counters the oxidative stress evoked by gallium, an iron mimetic

Gallium (Ga), an iron (Fe) mimetic promoted an oxidative environment and elicited an antioxidative response in Pseudomonas fluorescens. Ga-stressed P. fluorescens was characterized by higher amounts of oxidized lipids and proteins compared to control cells. The oxidative environment provoked by Ga was nullified by increased synthesis of NADPH. The activity and expression glucose 6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase-NADP (ICDH) were stimulated in Ga-cultures. The induction of isoenzymes of these dehydrogenases was also evident in the Ga-stressed cells. Although superoxide dismutase (SOD) activity was significantly enhanced in Ga-stressed cultures, catalase activity experienced a marked diminution. Fe metabolism appeared to be severely impeded by Ga toxicity. This is the first demonstration of the oxidative stress evoked by Ga to be neutralized by a reductive environment generated via the overexpression of NADPH-producing enzymes.

C/EBPβ regulates TNF induced MnSOD expression and protection against apoptosis

The CCAAT enhancer binding protein-beta (C/EBPbeta) is a critical regulator of many cellular processes. Exposure of C/EBPbeta-deficient fibroblasts to tumor necrosis factor-alpha (TNF) resulted in their death due to apoptosis. While, the expression of Bad, Bcl-2, Bcl-x, CAS, and hILP/XIAP, as well as the nuclear translocation of NF-kappaB was normal in C/EBPbeta-deficient cells, induction of manganous superoxide dismutase (MnSOD) gene did not occur. Ectopic expression of C/EBPbeta in C/EBPbeta-deficient fibroblasts prevented TNF-induced apoptosis. C/EBPbeta complemented cells were able to induce MnSOD in response to TNF, ruling out the possibilities that C/EBPbeta could render protection by regulating early apoptotic gene expression and/or NF-kappaB p65 expression. Moreover, C/EBPbeta-deficient cells stably transfected with an MnSOD expression vector bypassed the requirement of C/EBPbeta in protection against TNF-induced cell death, suggesting that C/EBPbeta protects TNF-induced apoptotic cell death through its role in activating MnSOD expression. Mechanistically, C/EBPbeta was required for induced NF-kappaB p65 binding to MnSOD's intronic TNF response element and indispensable for histone acetylation of the element in response to TNF. These results suggest a role for C/EBPbeta in MnSOD regulation through remodeling of local chromatin structure.

Epigallocatechin-3-gallate delivers hydrogen peroxide to induce death of ovarian cancer cells and enhances their cisplatin susceptibility

The green tea polyphenol epigallocatechin-3-gallate (EGCG) has cancer chemopreventive properties against various types of cancers. The compound is known to attack various targets in transformed cells. In this report, we examined the action of EGCG on ovarian cancer cells. Eight ovarian cancer cell lines were tested (SKOV3, CAOV3, OVCAR3, OVCAR10, A2780, CP70, C30, and C200) and showed IC50s for EGCG at the micromolar range, including ones that are resistant to the chemotherapeutic drug cisplatin. The ovarian cancer cells were sensitive to H2O2 at similar concentrations, and EGCG treatment led to enhanced intracellular H2O2. Neutralization with pyruvate, a scavenger of H2O2, suggests that the toxicity of EGCG may be mediated by oxidative stress from the free radical. Addition of Tempol, a superoxide dismutase mimetic, demonstrates that H2O2 might be generated endogenously from superoxide. The toxicity of cisplatin and the development of cisplatin resistance are major obstacles in treatment of ovarian cancer. We found that addition of EGCG amplified the toxicity of cisplatin. EGCG increased cisplatin potency by three to six-fold in SKOV3, CAOV3, and C200 cells, the latter being a cell line induced to have several hundred fold resistant to cisplatin above the parental line. Our findings suggest that EGCG may accentuate oxidative stress to inhibit growth of ovarian cancer cells and sensitize them to cisplatin.

Superoxide dismutases and their impact upon human health

Superoxide dismutases (SOD), a group of metal-containing enzymes, have a vital anti-oxidant role in human health, conferred by their scavenging of one of the reactive oxygen species, superoxide anion. Three types of SODs are known in humans, with the most abundant being cytosolic SOD1, identified by its Cu, Zn-containing prosthetic group. The presence of these metals and the coordination to certain amino acids are essential for function. SODs are among the first line of defense in the detoxification of products resulting from oxidative stress. Here, we describe the importance of SOD function, and the need for coordination with other ROS-scavenging enzymes in this pathway of detoxification. The impact of metal-deficient diets (copper or zinc) or incorrect metal ion incorporation (copper chaperone for SOD) onto nascent SOD, are also examined. Finally, human pathologies associated with either SOD dysfunction or decreased activity are discussed with current progress on the development of novel therapies.