Manganese superoxide dismutase in breast cancer: from molecular mechanisms of gene regulation to biological and clinical significance

Protective effects of SOD2 overexpression in human umbilical cord mesenchymal stem cells on lung injury induced by acute paraquat poisoning in rats

AIMS

To study the protective effects and mechanisms of human umbilical cord mesenchymal stem cells (hUCMSCs) and overexpression of antioxidant gene SOD2 on lung injury by establishing a rat model of paraquat (PQ)-induced lung injury.

MAIN METHODS

The hUCMSCs cell line overexpressed SOD2 was established. After intraperitoneal injection of PQ solution (24 mg/kg) 3 h later, the different groups of hUCMSCs cell lines were injected through the tail veins of rats. Bronchoalveolar lavage fluid (BALF) was obtained to determine the protein level of inflammatory cytokines. Lung tissues were collected to test the wet/dry weight ratios (W/D), oxidative stress index and lung injury scores. Western blotting was used to detect SOD1, SOD2, HO-1, Nrf2, NF-κBp65 subunit, and cleaved caspase-3.

KEY FINDINGS

After treatment with cells built on the basis of hUCMSCs, the protein levels of TNF-α, IL-8, and ICAM-1 in BALF decreased, and meanwhile in lung tissues, MDA content was reduced, GSH-Px activity was elevated, and lung W/D ratio decreased. Additionally, protein expression of NF-κB p65 subunit and activated caspase-3 in lung tissues was down-regulated, whereas expression of SOD1, SOD2, HO-1, and Nrf-2 were up-regulated. The results of HE staining showed that lung injury was significantly alleviated in the hUCMSC treated group. It is noticeable that hUCMSCs and SOD2-overexpressed hUCMSCs effectively reduced PQ-induced lung injury in rats, and moreover, hUCMSCs overexpressed SOD2 were more effective compared with hUCMSCs only.

SIGNIFICANCE

Evaluation of the efficacy and analysis of mechanism in the treatment of PQ induced ALI by appliance of SOD2-overexpressed hUCMSCs will provide the proof from bench to bedside.

Radiation Induces Apoptosis and Osteogenic Impairment through miR-22-Mediated Intracellular Oxidative Stress in Bone Marrow Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (BMSCs) were characterized by their multilineage potential and were involved in both bony and soft tissue repair. Exposure of cells to ionizing radiation (IR) triggers numerous biological reactions, including reactive oxygen species (ROS), cellular apoptosis, and impaired differentiation capacity, while the mechanisms of IR-induced BMSC apoptosis and osteogenic impairment are still unclear. Through a recent study, we found that 6 Gy IR significantly increased the apoptotic ratio and ROS generation, characterized by ROS staining and mean fluorescent intensity. Intervention with antioxidant (NAC) indicated that IR-induced cellular apoptosis was partly due to the accumulation of intracellular ROS. Furthermore, we found that the upregulation of miR-22 in rBMSCs following 6 Gy IR played an important role on the ROS generation and subsequent apoptosis. In addition, we firstly demonstrated that miR-22-mediated ROS accumulation and cell injury had an important regulated role on the osteogenic capacity of BMSCs both in vitro and in vivo. In conclusion, IR-induced overexpression of miR-22 regulated the cell viability and differentiation potential through targeting the intracellular ROS.

Evaluation and prognostic significance of manganese superoxide dismutase in clear cell renal cell carcinoma

The antioxidant enzyme manganese superoxide dismutase (MnSOD) is up-regulated in renal cell carcinoma (RCC) and has been implicated in multiple stages of RCC tumorigenesis and progression. However, the prognostic significance of MnSOD in RCC has not been fully elucidated. This study aimed to investigate the expression profile of MnSOD in clear cell RCC (ccRCC) tissues and evaluate the clinical significance of this enzyme in ccRCC patients. MnSOD mRNA was assessed in 42 ccRCC and 33 normal kidney tissues using the Oncomine database, and its protein was detected in 145 ccRCCs and 3 normal tissues by immunohistochemistry staining. The Oncomine database confirmed higher MnSOD mRNA expression in ccRCC than in normal tissues, and immunohistochemistry analysis revealed that MnSOD protein expression was inversely associated with pathologic grade, clinical stage, tumor size, M status, and cancer-specific survival. In addition, univariate survival analysis demonstrated that high-grade, late-stage, large tumors, stage M₁, and low MnSOD expression were associated with a poorer prognosis for cancer-specific survival, and further multivariate analysis revealed that tumor grade, stage, M₁ stage, and MnSOD were identified as independent prognostic factors for cancer-specific survival in patients with ccRCC. Collectively, these findings imply that MnSOD is a promising prognostic marker in ccRCC and implies that oxidative stress might be involved in the tumorigenesis and progression of ccRCC.

NLRP3 inflammasome inhibition ameliorates tubulointerstitial injury in the remnant kidney model

Recent studies suggest that NLRP3 inflammasome activation is involved in the pathogenesis of chronic kidney disease (CKD). Allopurinol (ALLO) inhibits xanthine oxidase (XOD) activity, and, consequently, reduces the production of uric acid (UA) and reactive oxygen species (ROS), both of which can activate the NLRP3 pathway. Thus, ALLO can contribute to slow the progression of CKD. We investigated whether inhibition of XOD by ALLO reduces NLRP3 activation and renal injury in the 5/6 renal ablation (Nx) model. Adult male Munich-Wistar rats underwent Nx and were subdivided into the following two groups: Nx, receiving vehicle only, and Nx + ALLO, Nx rats given ALLO, 36 mg/Kg/day in drinking water. Rats undergoing sham operation were studied as controls (C). Sixty days after surgery, Nx rats exhibited marked albuminuria, creatinine retention, and hypertension, as well as glomerulosclerosis, tubular injury, and cortical interstitial expansion/inflammation/fibrosis. Such changes were accompanied by increased XOD activity and UA renal levels, associated with augmented heme oxigenase-1 and reduced superoxide dismutase-2 renal contents. Both the NF-κB and NLRP3 signaling pathways were activated in Nx. ALLO normalized both XOD activity and the parameters of oxidative stress. ALLO also attenuated hypertension and promoted selective tubulointerstitial protection, reducing urinary NGAL and cortical interstitial injury/inflammation. ALLO reduced renal NLRP3 activation, without interfering with the NF-κB pathway. These observations indicate that the tubulointerstitial antiinflammatory and antifibrotic effects of ALLO in the Nx model involve inhibition of the NLRP3 pathway, and reinforce the view that ALLO can contribute to arrest or slow the progression of CKD.

Age-related NMDA signaling alterations in SOD2 deficient mice

Oxidative stress affects the survival and function of neurons. Hence, they have a complex and highly regulated machinery to handle oxidative changes. The dysregulation of this antioxidant machinery is associated with a wide range of neurodegenerative conditions. Therefore, we evaluated signaling alterations, synaptic properties and behavioral performance in 2 and 6-month-old heterozygous manganese superoxide dismutase knockout mice (SOD2^+/- mice). We found that their low antioxidant capacity generated direct oxidative damage in proteins, lipids, and DNA. However, only 6-month-old heterozygous knockout mice presented behavioral impairments. On the other hand, synaptic plasticity, synaptic strength and NMDA receptor (NMDAR) dependent postsynaptic potentials were decreased in an age-dependent manner. We also analyzed the phosphorylation state of the NMDAR subunit GluN2B. We found that while the levels of GluN2B phosphorylated on tyrosine 1472 (synaptic form) remain unchanged, we detected increased levels of GluN2B phosphorylated on tyrosine 1336 (extrasynaptic form), establishing alterations in the synaptic/extrasynaptic ratio of GluN2B. Additionally, we found increased levels of two phosphatases associated with dephosphorylation of p-1472: striatal-enriched protein tyrosine phosphatase (STEP) and phosphatase and tensin homolog deleted on chromosome Ten (PTEN). Moreover, we found decreased levels of p-CREB, a master transcription factor activated by synaptic stimulation. In summary, we describe mechanisms by which glutamatergic synapses are altered under oxidative stress conditions. Our results uncovered new putative therapeutic targets for conditions where NMDAR downstream signaling is altered. This work also contributes to our understanding of processes such as synapse formation, learning, and memory in neuropathological conditions.

Manganese superoxide dismutase mediates anoikis resistance and tumor metastasis in nasopharyngeal carcinoma

Metastatic cancer cells are able to survive the loss of attachment to the extracellular matrix (ECM) by developing resistance to anoikis, a specialized form of apoptosis. Here we investigated resistance to anoikis in nasopharyngeal carcinoma cells (NPC). When detached in culture, the highly metastatic S18 NPC cell line exhibited strong resistance to anoikis, as compared to the poorly metastatic S26 NPC cell line. With loss of attachment, S18 cells had lower levels of reactive oxygen species (ROS) and higher levels of manganese superoxide dismutase (MnSOD), an essential mitochondrial antioxidant enzyme. MnSOD knockdown increased the levels of ROS and diminished resistance to anoikis in S18 cells. Conversely, removal of reactive oxygen species (ROS) using NAC or overexpression of MnSOD in S26 cells induced resistance to anoikis. Blocking β-catenin through RNA interference down-regulated MnSOD expression and enhanced anoikis in S18 cells, while β-catenin overexpression enhanced MnSOD expression and suppressed anoikis in S26 cells. In addition, knockdown of MnSOD in S18 cells reduced colony formation in vitro and ameliorated lung metastasis in vivo. In patients with NPC, MnSOD expression was positively correlated with pathologic tumor stages and negatively correlated with overall survival. These results establish MnSOD as a key mediator of anoikis resistance and tumor metastasis and suggest that β-catenin/MnSOD could be a therapeutic target in NPC.

Insights into the Dichotomous Regulation of SOD2 in Cancer

While loss of antioxidant expression and the resultant oxidant-dependent damage to cellular macromolecules is key to tumorigenesis, it has become evident that effective oxidant scavenging is conversely necessary for successful metastatic spread. This dichotomous role of antioxidant enzymes in cancer highlights their context-dependent regulation during different stages of tumor development. A prominent example of an antioxidant enzyme with such a dichotomous role and regulation is the mitochondria-localized manganese superoxide dismutase SOD2 (MnSOD). SOD2 has both tumor suppressive and promoting functions, which are primarily related to its role as a mitochondrial superoxide scavenger and H₂O₂ regulator. However, unlike true tumor suppressor- or onco-genes, the SOD2 gene is not frequently lost, or rarely mutated or amplified in cancer. This allows SOD2 to be either repressed or activated contingent on context-dependent stimuli, leading to its dichotomous function in cancer. Here, we describe some of the mechanisms that underlie SOD2 regulation in tumor cells. While much is known about the transcriptional regulation of the SOD2 gene, including downregulation by epigenetics and activation by stress response transcription factors, further research is required to understand the post-translational modifications that regulate SOD2 activity in cancer cells. Moreover, future work examining the spatio-temporal nature of SOD2 regulation in the context of changing tumor microenvironments is necessary to allows us to better design oxidant- or antioxidant-based therapeutic strategies that target the adaptable antioxidant repertoire of tumor cells.

There is no relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival

Breast cancer is the most common diagnosed cancer among females worldwide. Superoxide dismutase 2 (SOD2), an antioxidant enzyme, may break the balance between the oxidant and antioxidant system to induce various diseases. The present study aimed to clarify the association between the SOD2 Val-16Ala polymorphism and breast cancer risk or survival. Thus, a meta-analysis of the relevant articles retrieved from PubMed and EMBASE databases was conducted to illuminate the association with odd ratios (ORs) or hazards ratios (HRs). A total of 26 eligible publications (n=38,008) were available in risk analysis and eight publications (n=5,746) in survival analysis. The results demonstrated a marginal association between breast cancer risk and SOD2 polymorphism in Caucasian patients [TT vs. CT + CC: (OR, 0.94; 95% confidence interval (CI), 0.88-1.00)]. However, no other positive results were observed in risk and survival of breast cancer in the whole study [T vs. C: (OR, 0.99; 95% CI, 0.96-1.02); CT vs. CC: (OR, 1.00; 95% CI, 0.95-1.05); TT vs. CC: (OR, 0.98; 95% CI, 0.92-1.05); TT vs. CT + CC: (OR, 1.00; 95% CI, 0.95-1.05); CT + TT vs. CC: (OR, 0.99; 95% CI, 0.95-1.05)]. The present meta-analysis indicated that there was no significant relationship between SOD2 Val-16Ala polymorphism and breast cancer risk or survival, although in Caucasian patients, the SOD2 TT genotype may marginally decrease the risk of breast cancer in comparison to the CT + CC genotype.

Polyphenols from Lonicera caerulea L. Berry Inhibit LPS-Induced Inflammation through Dual Modulation of Inflammatory and Antioxidant Mediators

Lonicera caerulea L. berry polyphenols (LCBP) are considered as major components for bioactivity. This study aimed to clarify the molecular mechanisms by monitoring inflammatory and antioxidant mediator actions in lipopolysaccharide (LPS)-induced mouse paw edema and macrophage cell model. LCBP significantly attenuated LPS-induced paw edema (3.0 ± 0.1 to 2.8 ± 0.1 mm, P < 0.05) and reduced (P < 0.05) serum levels of monocyte chemotactic protein-1 (MCP-1, 100.9 ± 2.3 to 58.3 ± 14.5 ng/mL), interleukin (IL)-10 (1596.1 ± 424.3 to 709.7 ± 65.7 pg/mL), macrophage inflammatory protein (MIP)-1α (1761.9 ± 208.3 to 1369.1 ± 56.4 pg/mL), IL-6 (1262.8 ± 71.7 to 499.0 ± 67.1 pg/mL), IL-4 (93.3 ± 25.7 to 50.7 ± 12.5 pg/mL), IL-12(p-70) (580.4 ± 132.0 to 315.2 ± 35.1 pg/mL), and tumor necrosis factor-α (TNF-α, 2045.5 ± 264.9 to 1270.7 ± 158.6 pg/mL). Cell signaling analysis revealed that LCBP inhibited transforming growth factor β activated kinase-1 (TAK1)-mediated mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways, and enhanced the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and manganese-dependent superoxide dismutase (MnSOD) in earlier response. Moreover, cyanidin 3-glucoside (C3G) and (-)-epicatechin (EC), two major components of LCBP, directly bound to TAK1. These data demonstrated that LCBP might inhibit LPS-induced inflammation by modulating both inflammatory and antioxidant mediators.

Allele-specific interaction between glutathione peroxidase 1 and manganese superoxide dismutase affects the levels of Bcl-2, Sirt3 and E-cadherin

Manganese superoxide dismutase (MnSOD) is a mitochondrial-resident enzyme that reduces superoxide to hydrogen peroxide (H₂O₂), which can be further reduced to water by glutathione peroxidase (GPX1). Data from human studies have indicated that common polymorphisms in both of these proteins are associated with the risk of several cancers, including breast cancer. Moreover, polymorphisms in MnSOD and GPX1 were shown to interact to increase the risk of breast cancer. To gain an understanding of the molecular mechanisms behind these observations, we engineered human MCF-7 breast cancer cells to exclusively express GPX1 and/or MnSOD alleles and investigated the consequences on the expression of several proteins associated with cancer aetiology. Little or no effect was observed on the ectopic expression of these genes on the phosphorylation of Akt, although allele-specific effects and interactions were observed for the impact on the levels of Bcl-2, E-cadherin and Sirt3. The patterns observed were not consistent with the steady-state levels of H₂O₂ determined in the transfected cells. These results indicate plausible contributing factors to the effects of allelic variations on cancer risk observed in human epidemiological studies.

STAT3 mediates multidrug resistance of Burkitt lymphoma cells by promoting antioxidant feedback

Burkitt lymphoma (BL) is a highly aggressive B-cell neoplasm. Although BL is relatively sensitive to chemotherapy, some patients do not respond to initial therapy or relapse after standard therapy, which leads to poor prognosis. The mechanisms underlying BL chemoresistance remain poorly defined. Here, we report a mechanism for the relationship between the phosphorylation of STAT3 on Tyr705 and BL chemoresistance. In chemoresistant BL cells, STAT3 was activated and phosphorylated on Tyr705 in response to the generation of the reactive oxygen species (ROS), which induced Src Tyr416 phosphorylation after multi-chemotherapeutics treatment. As a transcription factor, the elevated phosphorylation level of STAT3^Y705 increased the expression of GPx1 and SOD2, both of which protected cells against oxidative damage. Our findings revealed that the ROS-Src-STAT3-antioxidation pathway mediated negative feedback inhibition of apoptosis induced by chemotherapy. Thus, the phosphorylation of STAT3 on Tyr705 might be a target for the chemo-sensitization of BL.

Selenium levels in human breast carcinoma tissue are associated with a common polymorphism in the gene for SELENOP (Selenoprotein P)

Selenium supplementation of the diets of rodents has consistently been shown to suppress mammary carcinogenesis and some, albeit not all, human epidemiological studies have indicated an inverse association between selenium and breast cancer risk. In order to better understand the role selenium plays in breast cancer, 30 samples of tumor tissue were obtained from women with breast cancer and analyzed for selenium concentration, the levels of several selenium-containing proteins and the levels of the MnSOD anti-oxidant protein. Polymorphisms within the genes for these same proteins were determined from DNA isolated from the tissue samples. There was a wide range of selenium in these tissues, ranging from 24 to 854ng/gm. The selenium levels in the tissues were correlated to the genotype of the SELENOP selenium carrier protein, but not to other proteins whose levels have been reported to be responsive to selenium availability, including GPX1, SELENOF and SBP1. There was an association between a polymorphism in the gene for MnSOD and the levels of the encoded protein. These studies were the first to examine the relationship between selenium levels, genotypes and protein levels in human tissues. Furthermore, the obtained data provide evidence for the need to obtain data about the effects of selenium in breast cancer by examining samples from that particular tissue type.

Understanding the pathophysiology of schizophrenia: Contributions from the Melbourne Psychiatric Brain Bank

The Melbourne Psychiatric Brain Bank came into existence 25years ago. This review focusses on lines of research that have used tissue from the Brain Bank over periods of time. Hence there is a discussion on the significance of changes in levels of serotonin 2A receptors in the cortex of patients with schizophrenia and the relevance of such changes with regards to the pathophysiology of the disorder. The extensive contribution made by studies using tissue from the Melbourne Psychiatric Brain Bank to understanding the role of muscarinic receptors in the pathophysiology and treatment of schizophrenia is summarised. Finally, findings using brain bank tissue and "omics" technologies are reviewed. In each case, findings using tissue from the Melbourne Psychiatric Brain Bank is placed in context with research carried out on human postmortem CNS in schizophrenia and with findings in other lines of research that can help explain the causes or consequences of changes in CNS molecular cytoarchitecture. This timely review of data from the Melbourne Psychiatric Brain Bank reinforces the challenges faced in trying to increase our understanding of the molecular pathophysiology of schizophrenia. Continuing to increase our understanding of the disorder is important as a precursor to identifying new drug targets that can be exploited to improve the treatment of a disorder where treatment resistance remains a significant problem (Millan et al., 2016).

Proteomic Approaches to Biomarker Discovery in Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma (CTCL) is the most frequently encountered type of skin lymphoma in humans. CTCL encompasses multiple variants, but the most common types are mycosis fungoides (MF) and Sezary syndrome (SS). While most cases of MF run a mild course over a period of many years, other subtypes of CTCL are very aggressive. The rapidly expanding fields of proteomics and genomics have not only helped increase knowledge concerning the carcinogenesis and tumor biology of CTCL but also led to the discovery of novel markers for targeted therapy. Although multiple biomarkers linked to CTCL have been known for a relatively long time (e.g., CD25, CD45, CD45RA, and CD45R0), compared to other cancers (lymphoma, melanoma, colon carcinoma, head and neck cancer, renal cancer, and cutaneous B-cell lymphoma), information about the antigenicity of CTCL remains relatively limited and no dependable protein marker for CTCL has been discovered. Considering the aggressive nature of some types of CTCL, it is necessary to identify circulating molecules that can help in the early diagnosis, differentiation from inflammatory skin diseases (psoriasis, nummular eczema), and aid in predicting the prognosis and evolution of this pathology. This review aims to bring together some of the information concerning protein markers linked to CTCL, in an effort to further the understanding of the convolute processes involved in this complex pathology.

Breast Cancer: A Molecular and Redox Snapshot

SIGNIFICANCE

Breast cancer is a unique disease characterized by heterogeneous cell populations causing roadblocks in therapeutic medicine, owing to its complex etiology and primeval understanding of the biology behind its genesis, progression, and sustenance. Globocan statistics indicate over 1.7 million new breast cancer diagnoses in 2012, accounting for 25% of all cancer morbidities.

RECENT ADVANCES

Despite these dismal statistics, the introduction of molecular gene signature platforms, progressive therapeutic approaches in diagnosis, and management of breast cancer has led to more effective treatment strategies and control measures concurrent with an equally reassuring decline in the mortality rate.

CRITICAL ISSUES

However, an enormous body of research in this area is requisite as high mortality associated with metastatic and/or drug refractory tumors continues to present a therapeutic challenge. Despite advances in systemic chemotherapy, the median survival of patients harboring metastatic breast cancers continues to be below 2 years.

FUTURE DIRECTIONS

Hence, a massive effort to scrutinize and evaluate chemotherapeutics on the basis of the molecular classification of these cancers is undertaken with the objective to devise more attractive and feasible approaches to treat breast cancers and improve patients' quality of life. This review aims to summarize the current understanding of the biology of breast cancer as well as challenges faced in combating breast cancer, with special emphasis on the current battery of treatment strategies. We will also try and gain perspective from recent encounters on novel findings responsible for the progression and metastatic transformation of breast cancer cells in an endeavor to develop more targeted treatment options. Antioxid. Redox Signal. 25, 337-370.

Manganese Superoxide Dismutase Acetylation and Dysregulation, Due to Loss of SIRT3 Activity, Promote a Luminal B-Like Breast Carcinogenic-Permissive Phenotype

SIGNIFICANCE

Breast cancer is the most common nondermatologic malignancy among women in the United States, among which endocrine receptor-positive breast cancer accounts for up to 80%. Endocrine receptor-positive breast cancers can be categorized molecularly into luminal A and B subtypes, of which the latter is an aggressive form that is less responsive to endocrine therapy with inferior prognosis.

RECENT ADVANCES

Sirtuin, an aging-related gene involved in mitochondrial metabolism, is associated with life span, and more importantly, murine models lacking Sirt3 spontaneously develop tumors that resemble human luminal B breast cancer. Furthermore, these tumors exhibit aberrant manganese superoxide dismutase (MnSOD) acetylation at lysine 68 and lysine 122 and have abnormally high reactive oxygen species (ROS) levels, which have been observed in many types of breast cancer.

CRITICAL ISSUES

The mechanism of how luminal B breast cancer develops resistance to endocrine therapy remains unclear. MnSOD, a primary mitochondrial detoxification enzyme, functions by scavenging excessive ROS from the mitochondria and maintaining mitochondrial and cellular homeostasis. Sirt3, a mitochondrial fidelity protein, can regulate the activity of MnSOD through deacetylation. In this study, we discuss a possible mechanism of how loss of SIRT3-guided MnSOD acetylation results in endocrine therapy resistance of human luminal B breast cancer.

FUTURE DIRECTIONS

Acetylation of MnSOD and other mitochondrial proteins, due to loss of SIRT3, may explain the connection between ROS and development of luminal B breast cancer and how luminal B breast cancer becomes resistant to endocrine therapy. Antioxid. Redox Signal. 25, 326-336.

Increased sensitivity of African American triple negative breast cancer cells to nitric oxide-induced mitochondria-mediated apoptosis

Background

Breast cancer is a complex heterogeneous disease where many distinct subtypes are found. Younger African American (AA) women often present themselves with aggressive form of breast cancer with unique biology which is very difficult to treat. Better understanding the biology of AA breast tumors could lead to development of effective treatment strategies. Our previous studies indicate that AA but not Caucasian (CA) triple negative (TN) breast cancer cells were sensitive to nitrosative stress-induced cell death. In this study, we elucidate possible mechanisms that contribute to nitric oxide (NO)-induced apoptosis in AA TN breast cancer cells.

Methods

Breast cancer cells were treated with various concentrations of long-acting NO donor, DETA-NONOate and cell viability was determined by trypan blue exclusion assay. Apoptosis was determined by TUNEL and caspase 3 activity as well as changes in mitochondrial membrane potential. Caspase 3 and Bax cleavage, levels of Cu/Zn superoxide dismutase (SOD) and Mn SOD was assessed by immunoblot analysis. Inhibition of Bax cleavage by Calpain inhibitor, and levels of reactive oxygen species (ROS) as well as SOD activity was measured in NO-induced apoptosis. In vitro and in vivo effect of NO treatment on mammary cancer stem cells (MCSCs) was assessed.

Results and discussion

NO induced mitocondria-mediated apoptosis in all AA but not in CA TN breast cancer cells. We found significant TUNEL-positive cells, cleavage of Bax and caspase-3 activation as well as depolarization mitochondrial membrane potential only in AA TN breast cancer cells exposed to NO. Inhibition of Bax cleavage and quenching of ROS partially inhibited NO-induced apoptosis in AA TN cells. Increase in ROS coincided with reduction in SOD activity in AA TN breast cancer cells. Furthermore, NO treatment of AA TN breast cancer cells dramatically reduced aldehyde dehydrogenase1 (ALDH1) expressing MCSCs and xenograft formation but not in breast cancer cells from CA origin.

Conclusions

Ethnic differences in breast tumors dictate a need for tailoring treatment options more suited to the unique biology of the disease.

Mitochondrial common deletion is elevated in blood of breast cancer patients mediated by oxidative stress

The 4977 bp common deletion is one of the most frequently observed mitochondrial DNA (mtDNA) mutations in human tissues and has been implicated in various human cancer types. It is generally believed that continuous generation of intracellular reactive oxygen species (ROS) during oxidative phosphorylation (OXPHOS) is a major underlying mechanism for generation of such mtDNA deletions while antioxidant systems, including Manganese superoxide dismutase (MnSOD), mitigating the deleterious effects of ROS. However, the clinical significance of this common deletion remains to be explored. A comprehensive investigation on occurrence and accumulation of the common deletion and mtDNA copy number was carried out in breast carcinoma (BC) patients, benign breast disease (BBD) patients and age-matched healthy donors in our study. Meanwhile, the representative oxidative (ROS production, mtDNA and lipid oxidative damage) and anti-oxidative features (MnSOD expression level and variation) in blood samples from these groups were also analyzed. We found that the mtDNA common deletion is much more likely to be detected in BC patients at relatively high levels while the mtDNA content is lower. This alteration has been associated with a higher MnSOD level and higher oxidative damages in both BC and BBD patients. Our results indicate that the mtDNA common deletion in blood may serve a biomarker for the breast cancer.

Anticancer therapeutic potential of Mn porphyrin/ascorbate system

Ascorbate (Asc) as a single agent suppressed growth of several tumor cell lines in a mouse model. It has been tested in a Phase I Clinical Trial on pancreatic cancer patients where it exhibited no toxicity to normal tissue yet was of only marginal efficacy. The mechanism of its anticancer effect was attributed to the production of tumoricidal hydrogen peroxide (H2O2) during ascorbate oxidation catalyzed by endogenous metalloproteins. The amount of H2O2 could be maximized with exogenous catalyst that has optimized properties for such function and is localized within tumor. Herein we studied 14 Mn porphyrins (MnPs) which differ vastly with regards to their redox properties, charge, size/bulkiness and lipophilicity. Such properties affect the in vitro and in vivo ability of MnPs (i) to catalyze ascorbate oxidation resulting in the production of H2O2; (ii) to subsequently employ H2O2 in the catalysis of signaling proteins oxidations affecting cellular survival pathways; and (iii) to accumulate at site(s) of interest. The metal-centered reduction potential of MnPs studied, E1/2 of Mn(III)P/Mn(II)P redox couple, ranged from -200 to +350 mV vs NHE. Anionic and cationic, hydrophilic and lipophilic as well as short- and long-chained and bulky compounds were explored. Their ability to catalyze ascorbate oxidation, and in turn cytotoxic H2O2 production, was explored via spectrophotometric and electrochemical means. Bell-shape structure-activity relationship (SAR) was found between the initial rate for the catalysis of ascorbate oxidation, vo(Asc)ox and E1/2, identifying cationic Mn(III) N-substituted pyridylporphyrins with E1/2>0 mV vs NHE as efficient catalysts for ascorbate oxidation. The anticancer potential of MnPs/Asc system was subsequently tested in cellular (human MCF-7, MDA-MB-231 and mouse 4T1) and animal models of breast cancer. At the concentrations where ascorbate (1mM) and MnPs (1 or 5 µM) alone did not trigger any alteration in cell viability, combined treatment suppressed cell viability up to 95%. No toxicity was observed with normal human breast epithelial HBL-100 cells. Bell-shape relationship, essentially identical to vo(Asc)oxvs E1/2, was also demonstrated between MnP/Asc-controlled cytotoxicity and E1/2-controlled vo(Asc)ox. Magnetic resonance imaging studies were conducted to explore the impact of ascorbate on T1-relaxivity. The impact of MnP/Asc on intracellular thiols and on GSH/GSSG and Cys/CySS ratios in 4T1 cells was assessed and cellular reduction potentials were calculated. The data indicate a significant increase in cellular oxidative stress induced by MnP/Asc. Based on vo(Asc)oxvs E1/2 relationships and cellular toxicity, MnTE-2-PyP(5+) was identified as the best catalyst among MnPs studied. Asc and MnTE-2-PyP(5+) were thus tested in a 4T1 mammary mouse flank tumor model. The combination of ascorbate (4 g/kg) and MnTE-2-PyP(5+) (0.2mg/kg) showed significant suppression of tumor growth relative to either MnTE-2-PyP(5+) or ascorbate alone. About 7-fold higher accumulation of MnTE-2-PyP(5+) in tumor vs normal tissue was found to contribute largely to the anticancer effect.

Proteomic Profiling of Hematopoietic Stem/Progenitor Cells after a Whole Body Exposure of CBA/CaJ Mice to Titanium (48Ti) Ions

Myeloid leukemia (ML) is one of the major health concerns from exposure to radiation. However, the risk assessment for developing ML after exposure to space radiation remains uncertain. To reduce the uncertainty in risk prediction for ML, a much increased understanding of space radiation-induced changes in the target cells, i.e., hematopoietic stem/progenitor cells (HSPCs), is critically important. We used the label-free quantitative mass spectrometry (LFQMS) proteomic approach to determine the expression of protein in HSPC-derived myeloid colonies obtained at an early time-point (one week) and a late time-point (six months) after an acute whole body exposure of CBA/CaJ mice to a total dose of 0, 0.1, 0.25, or 0.5 Gy of heavy-ion titanium (⁴⁸Ti ions), which are the important component of radiation found in the space environment. Mice exposed to 0 Gy of ⁴⁸Ti ions served as non-irradiated sham controls. There were five mice per treatment groups at each harvest time. The Trans-Proteomic Pipeline (TPP) was used to assign a probability of a particular protein being in the sample. A proof-of-concept based Ingenuity Pathway Analysis (IPA) was used to characterize the functions, pathways, and networks of the identified proteins. Alterations of expression levels of proteins detected in samples collected at one week (wk) post-irradiation reflects acute effects of exposure to ⁴⁸Ti ions, while those detected in samples collected at six months (mos) post-irradiation represent protein expression profiles involved in the induction of late-occurring damage (normally referred to as genomic instability). Our results obtained by using the IPA analyses indicate a wide array of signaling pathways involved in response to 1 GeV/n ⁴⁸Ti ions at both harvest times. Our data also demonstrate that the patterns of protein expression profiles are dose and time dependent. The majority of proteins with altered expression levels are involved in cell cycle control, cellular growth and proliferation, cell death and survival, cell-to-cell signaling and interaction. The IPA analyses indicate several important processes involved in responses to exposure to ⁴⁸Ti ions. These include the proteosme/ubiquination, protein synthesis, post-translation modification, and lipid metabolism. The IPA analyses also indicate that exposure to 1 GeV/n ⁴⁸Ti ions affects the development and function of hematological system, immune cell trafficking, including the cytoskeleton. Further, the IPA analyses strongly demonstrate that the NF-κB and MAPKs (ERKs, JNKs, and p38MAPK) pathways play an essential role in signal transduction after exposure to 1 GeV/n ⁴⁸Ti ions. At an early time-point (1 week), the top networks identified by the IPA analyses are related to metabolic disease, lipid metabolism, small molecule biochemistry, and development disorder. In contrast, the top networks identified in samples collected at a late time-point (6 mos post-irradiation) by the IPA analyses are related to cancer, hematological disorders, and immunological diseases. In summary, the proteomic findings from our study provide a foundation to uncover compounds potentially be highly effective in radiation countermeasures.