Regulation and novel action of thymidine phosphorylase in non-small cell lung cancer: crosstalk with Nrf2 and HO-1

Antioxidant genes in cancer and metabolic diseases: Focusing on Nrf2, Sestrin, and heme oxygenase 1

Reactive oxygen species are involved in the pathogenesis of cancers and metabolic diseases, including diabetes, obesity, and fatty liver disease. Thus, inhibiting the generation of free radicals is a promising strategy to control the onset of metabolic diseases and cancer progression. Various synthetic drugs and natural product-derived compounds that exhibit antioxidant activity have been reported to have a protective effect against a range of metabolic diseases and cancer. This review highlights the development and aggravation of cancer and metabolic diseases due to the imbalance between pro-oxidants and endogenous antioxidant molecules. In addition, we discuss the function of proteins that regulate the production of reactive oxygen species as a strategy to treat metabolic diseases. In particular, we summarize the role of proteins such as nuclear factor-like 2, Sestrin, and heme oxygenase-1, which regulate the expression of various antioxidant genes in metabolic diseases and cancer. We have included recent literature to discuss the latest research on identifying novel signals of antioxidant genes that can control metabolic diseases and cancer.

The senescence-associated secretome of Hedgehog-deficient hepatocytes drives MASLD progression

The burden of senescent hepatocytes correlates with the severity of metabolic dysfunction-associated steatotic liver disease (MASLD), but the mechanisms driving senescence and how it exacerbates MASLD are poorly understood. Hepatocytes experience lipotoxicity and become senescent when Smoothened (Smo) is deleted to disrupt Hedgehog signaling. We aimed to determine whether the secretomes of Smo-deficient hepatocytes perpetuate senescence to drive MASLD progression. RNA-Seq analysis of liver samples from human and murine cohorts with MASLD confirmed that hepatocyte populations in MASLD livers were depleted of Smo+ cells and enriched with senescent cells. When fed a choline-deficient, amino acid-restricted high-fat diet (CDA-HFD) to induce MASLD, Smo- mice had lower antioxidant markers and developed worse DNA damage, senescence, steatohepatitis, and fibrosis than did Smo+ mice. Sera and hepatocyte-conditioned medium from Smo- mice were depleted of thymidine phosphorylase (TP), a protein that maintains mitochondrial fitness. Treating Smo- hepatocytes with TP reduced senescence and lipotoxicity, whereas inhibiting TP in Smo+ hepatocytes had the opposite effect and exacerbated hepatocyte senescence, steatohepatitis, and fibrosis in CDA-HFD-fed mice. We conclude that inhibition of Hedgehog signaling in hepatocytes promoted MASLD by suppressing hepatocyte production of proteins that prevent lipotoxicity and senescence.

Heme Oxygenase-1 and Its Role in Colorectal Cancer

Heme oxygenase-1 (HO-1) is an enzyme located at the endoplasmic reticulum, which is responsible for the degradation of cellular heme into ferrous iron, carbon monoxide and biliverdin-IXa. In addition to this main function, the enzyme is involved in many other homeostatic, toxic and cancer-related mechanisms. In this review, we first summarize the importance of HO-1 in physiology and pathophysiology with a focus on the digestive system. We then detail its structure and function, followed by a section on the regulatory mechanisms that control HO-1 expression and activity. Moreover, HO-2 as important further HO isoform is discussed, highlighting the similarities and differences with regard to HO-1. Subsequently, we describe the direct and indirect cytoprotective functions of HO-1 and its breakdown products carbon monoxide and biliverdin-IXa, but also highlight possible pro-inflammatory effects. Finally, we address the role of HO-1 in cancer with a particular focus on colorectal cancer. Here, relevant pathways and mechanisms are presented, through which HO-1 impacts tumor induction and tumor progression. These include oxidative stress and DNA damage, ferroptosis, cell cycle progression and apoptosis as well as migration, proliferation, and epithelial-mesenchymal transition.

Modulation of Nrf2/HO-1 by Natural Compounds in Lung Cancer

Oxidative stresses (OSs) are considered a pivotal factor in creating various pathophysiological conditions. Cells have been able to move forward by modulating numerous signaling pathways to moderate the defects of these stresses during their evolution. The company of Kelch-like ECH-associated protein 1 (Keap1) as a molecular sensing element of the oxidative and electrophilic stress and nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) as a master transcriptional regulator of the antioxidant response makes a master cytoprotective antioxidant pathway known as the Keap1/Nrf2 pathway. This pathway is considered a dual-edged sword with beneficial features for both normal and cancer cells by regulating the gene expression of the array of endogenous antioxidant enzymes. Heme oxygenase-1 (HO-1), a critical enzyme in toxic heme removal, is one of the clear state indicators for the duality of this pathway. Therefore, Nrf2/HO-1 axis targeting is known as a novel strategy for cancer treatment. In this review, the molecular mechanism of action of natural antioxidants on lung cancer cells has been investigated by relying on the Nrf2/HO-1 axis.

High Hemin Concentration Induces Escape from Senescence of Normoxic and Hypoxic Colon Cancer Cells

Simple Summary

High red-meat consumption as well as bleeding or bruising can promote oxidative stress and, in consequence, cancer development. However, the mechanism of that phenomenon is not understood. The induction of therapy-induced senescence (TIS) might also be induced by oxidative stress. Recently, TIS cells, despite their inhibited proliferation potential, have been identified as one of the sources of tumor re-growth. Here, with the use of molecular analyses, we found that oxidative stress, promoted by high doses of hemin or H₂O₂, can trigger TIS escape and cell re-population. It is closely related to the activity of antioxidative enzymes, especially heme oxygenase-1. Hypoxia might accelerate these effects. Therefore, we propose that the prevention of excessive oxidative stress could be a potential target in senolytic therapies.

Abstract

Hemoglobin from either red meat or bowel bleeding may promote oxidative stress and increase the risk of colorectal cancer (CRC). Additionally, solid cancers or their metastases may be present with localized bruising. Escape from therapy-induced senescence (TIS) might be one of the mechanisms of tumor re-growth. Therefore, we sought to study whether hemin can cause escape from TIS in CRC. To induce senescence, human colon cancer cells were exposed to a chemotherapeutic agent irinotecan (IRINO). Cells treated with IRINO exhibited common hallmarks of TIS. To mimic bleeding, colon cancer cells were additionally treated with hemin. High hemin concentration activated heme oxygenase-1 (HO-1), induced escape from TIS and epithelial-to-mesenchymal transition, and augmented progeny production. The effect was even stronger in hypoxic conditions. Similar results were obtained when TIS cells were treated with another prooxidant agent, H₂O₂. Silencing of antioxidative enzymes such as catalase (CAT) or glutathione peroxidase-1 (GPx-1) maintained colon cancer cells in a senescent state. Our study demonstrates that a high hemin concentration combined with an increased activity of antioxidative enzymes, especially HO-1, leads to escape from the senescence of colon cancer cells. Therefore, our observations could be used in targeted anti-cancer therapy.

CRISPR/Cas9-mediated knockout of HO-1 decreased the proliferation and migration of T47D cells and increased cisplatin-induced apoptosis: an in vitro study

Breast cancer is the most common type of neoplasm and the second cause of cancer-related death in women. Despite the development of novel therapeutic strategies and improved the clinical outcomes, the mortality rate for breast cancer is still high. Therefore, development of a new modality, particularly based on knocking out key genes, is under focus of investigation. Heme oxygenase-1 (HO-1) deregulation has been associated with various neoplasms-related behaviors of many types of tumor cells including breast cancer. In the current study, in order to evaluate the role of the HO-1 gene in breast cancer, we utilized the CRISPR/Cas9 technology to knock out HO-1 gene in T47D breast cancer cell line and studied its potential therapeutic effects in vitro. The cell proliferation and their sensitivity to Cisplatin were determined by CCK-8 kit. In addition, the apoptosis and the migratory potential of the cells were evaluated using Hoechst staining, and Transwell/Scratch methods, respectively. Our findings revealed that HO-1 suppression significantly reduced the proliferation ability of T47D cells (P < 0.001). Moreover, sensitivity to Cisplatin-induced toxicity increased significantly in KO-T47D cells compared to the control T47D cells. Furthermore, our findings indicated that Cisplatin-induced apoptosis increased in the KO-T47D cells. Moreover, the migratory capability of KO-T47D cells was abolished significantly (P < 0.001) as determined by Transwell migration assay. In a nutshell, our findings strongly suggest that HO-1 involved in breast cancer progression and metastasis and chemotherapy resistance. However, further comprehensive studies are required to clarify the precise role of the HO-1 gene on breast cancer cells.

MDACT: A New Principle of Adjunctive Cancer Treatment Using Combinations of Multiple Repurposed Drugs, with an Example Regimen

In part one of this two-part paper, we present eight principles that we believe must be considered for more effective treatment of the currently incurable cancers. These are addressed by multidrug adjunctive cancer treatment (MDACT), which uses multiple repurposed non-oncology drugs, not primarily to kill malignant cells, but rather to reduce the malignant cells' growth drives. Previous multidrug regimens have used MDACT principles, e.g., the CUSP9v3 glioblastoma treatment. MDACT is an amalgam of (1) the principle that to be effective in stopping a chain of events leading to an undesired outcome, one must break more than one link; (2) the principle of Palmer et al. of achieving fractional cancer cell killing via multiple drugs with independent mechanisms of action; (3) the principle of shaping versus decisive operations, both being required for successful cancer treatment; (4) an idea adapted from Chow et al., of using multiple cytotoxic medicines at low doses; (5) the idea behind CUSP9v3, using many non-oncology CNS-penetrant drugs from general medical practice, repurposed to block tumor survival paths; (6) the concept from chess that every move creates weaknesses and strengths; (7) the principle of mass-by adding force to a given effort, the chances of achieving the goal increase; and (8) the principle of blocking parallel signaling pathways. Part two gives an example MDACT regimen, gMDACT, which uses six repurposed drugs-celecoxib, dapsone, disulfiram, itraconazole, pyrimethamine, and telmisartan-to interfere with growth-driving elements common to cholangiocarcinoma, colon adenocarcinoma, glioblastoma, and non-small-cell lung cancer. gMDACT is another example of-not a replacement for-previous multidrug regimens already in clinical use, such as CUSP9v3. MDACT regimens are designed as adjuvants to be used with cytotoxic drugs.

NRF2 and Key Transcriptional Targets in Melanoma Redox Manipulation

Melanocytes are dendritic, pigment-producing cells located in the skin and are responsible for its protection against the deleterious effects of solar ultraviolet radiation (UVR), which include DNA damage and elevated reactive oxygen species (ROS). They do so by synthesizing photoprotective melanin pigments and distributing them to adjacent skin cells (e.g., keratinocytes). However, melanocytes encounter a large burden of oxidative stress during this process, due to both exogenous and endogenous sources. Therefore, melanocytes employ numerous antioxidant defenses to protect themselves; these are largely regulated by the master stress response transcription factor, nuclear factor erythroid 2-related factor 2 (NRF2). Key effector transcriptional targets of NRF2 include the components of the glutathione and thioredoxin antioxidant systems. Despite these defenses, melanocyte DNA often is subject to mutations that result in the dysregulation of the proliferative mitogen-activated protein kinase (MAPK) pathway and the cell cycle. Following tumor initiation, endogenous antioxidant systems are co-opted, a consequence of elevated oxidative stress caused by metabolic reprogramming, to establish an altered redox homeostasis. This altered redox homeostasis contributes to tumor progression and metastasis, while also complicating the application of exogenous antioxidant treatments. Further understanding of melanocyte redox homeostasis, in the presence or absence of disease, would contribute to the development of novel therapies to aid in the prevention and treatment of melanomas and other skin diseases.

Tin Mesoporphyrin Selectively Reduces Non-Small-Cell Lung Cancer Cell Line A549 Proliferation by Interfering with Heme Oxygenase and Glutathione Systems

In order to maintain redox homeostasis, non-small-cell lung cancer (NSCLC) increases the activation of many antioxidant systems, including the heme-oxygenase (HO) system. The overexpression of HO-1 has been often associated with chemoresistance and tumor aggressiveness. Our results clearly showed an overexpression of the HO-1 protein in A549 NSCLC cell lines compared to that in non-cancerous cells. Thus, we hypothesized that "off-label" use of tin mesoporphyrin, a well-known HO activity inhibitor clinically used for neonatal hyperbilirubinemia, has potential use as an anti-cancer agent. The pharmacological inhibition of HO activity caused a reduction in cell proliferation and migration of A549. SnMP treatment caused an increase in oxidative stress, as demonstrated by the upregulation of reactive oxygen species (ROS) and the depletion of glutathione (GSH) content. To support these data, Western blot analysis was performed to analyze glucose-6-phosphate dehydrogenase (G6PD), TP53-induced glycolysis and the apoptosis regulator (TIGAR), and the glutamate cysteine ligase catalytic (GCLC) subunit, as they represent the main regulators of the pentose phosphate pathway (PPP) and glutathione synthesis, respectively. NCI-H292, a subtype of the NSCLC cell line, did not respond to SnMP treatment, possibly due to low basal levels of HO-1, suggesting a cellular-dependent antitumorigenic effect. Altogether, our results suggest HO activity inhibition may represent a potential target for selective chemotherapy in lung cancer subtypes.

The Diverse Roles of Heme Oxygenase-1 in Tumor Progression

Heme oxygenase-1 (HO-1) is an inducible intracellular enzyme that is expressed in response to a variety of stimuli to degrade heme, which generates the biologically active catabolites carbon monoxide (CO), biliverdin and ferrous iron (Fe²⁺). HO-1 is expressed across a range of cancers and has been demonstrated to promote tumor progression through a variety of mechanisms. HO-1 can be expressed in a variety of cells within the tumor microenvironment (TME), including both the malignant tumor cells as well as stromal cell populations such as macrophages, dendritic cells and regulatory T-cells. Intrinsically to the cell, HO-1 activity provides antioxidant, anti-apoptotic and cytoprotective effects via its catabolites as well as clearing toxic intracellular heme. However, the catabolites of heme degradation can also diffuse outside of the cell to extrinsically modulate the wider TME, influencing cellular functionality and biological processes which promote tumor progression, such as facilitating angiogenesis and metastasis, as well as promoting anti-inflammation and immune suppression. Pharmacological inhibition of HO-1 has been demonstrated to be a promising therapeutic approach to promote anti-tumor immune responses and inhibit metastasis. However, these biological functions might be context, TME and cell type-dependent as there is also conflicting reports for HO-1 activity facilitating anti-tumoral processes. This review will consider our current understanding of the role of HO-1 in cancer progression and as a therapeutic target in cancer.

Nrf2 Mediates Metabolic Reprogramming in Non-Small Cell Lung Cancer

Nuclear factor erythroid-2–related factor-2 (NFE2L2/Nrf2) is a transcription factor that regulates the expression of antioxidant genes. Both Kelch-like ECH-associated protein 1 (Keap1) mutations and Nrf2 mutations contribute to the activation of Nrf2 in non-small cell lung cancer (NSCLC). Nrf2 activity is associated with poor prognosis in NSCLC. Metabolic reprogramming represents a cancer hallmark. Increasing studies reveal that Nrf2 activation promotes metabolic reprogramming in cancer. In this review, we discuss the underlying mechanisms of Nrf2-mediated metabolic reprogramming and elucidate its role in NSCLC. Inhibition of Nrf2 can alter metabolic processes, thus suppress tumor growth, prevent metastasis, and increase sensitivity to chemotherapy in NSCLC. In conclusion, Nrf2 may serve as a therapeutic target for the treatment of NSCLC.

Control of tumor angiogenesis and metastasis through modulation of cell redox state

Redox reactions pervade all biology. The control of cellular redox state is essential for bioenergetics and for the proper functioning of many biological functions. This review traces a timeline of findings regarding the connections between redox and cancer. There is ample evidence of the involvement of cellular redox state on the different hallmarks of cancer. Evidence of the control of tumor angiogenesis and metastasis through modulation of cell redox state is reviewed and highlighted.

The Roles of NRF2 in Modulating Cellular Iron Homeostasis

SIGNIFICANCE

Iron and oxygen are intimately linked: iron is an essential nutrient utilized as a cofactor in enzymes for oxygen transport, oxidative phosphorylation, and metabolite oxidation. However, excess labile iron facilitates the formation of oxygen-derived free radicals capable of damaging biomolecules. Therefore, biological utilization of iron is a tightly regulated process. The nuclear factor (erythroid-derived 2)-like 2 (NRF2) transcription factor, which can respond to oxidative and electrophilic stress, regulates several genes involved in iron metabolism. Recent Advances: The bulk of NRF2 transcription factor research has focused on its roles in detoxification and cancer prevention. Recent works have identified that several genes involved in heme synthesis, hemoglobin catabolism, iron storage, and iron export are under the control of NRF2. Constitutive NRF2 activation and subsequent deregulation of iron metabolism have been implicated in cancer development: NRF2-mediated upregulation of the iron storage protein ferritin or heme oxygenase 1 can lead to enhanced proliferation and therapy resistance. Of note, NRF2 activation and alterations to iron signaling in cancers may hinder efforts to induce the iron-dependent cell death process known as ferroptosis.

CRITICAL ISSUES

Despite growing recognition of NRF2 as a modulator of iron signaling, exactly how iron metabolism is altered due to NRF2 activation in normal physiology and in pathologic conditions remains imprecise; moreover, the roles of NRF2-mediated iron signaling changes in disease progression are only beginning to be uncovered.

FUTURE DIRECTIONS

Further studies are necessary to connect NRF2 activation with physiological and pathological changes to iron signaling and oxidative stress. Antioxid. Redox Signal. 00, 000-000.

HO-1 Induction in Cancer Progression: A Matter of Cell Adaptation

The upregulation of heme oxygenase-1 (HO-1) is one of the most important mechanisms of cell adaptation to stress. Indeed, the redox sensitive transcription factor Nrf2 is the pivotal regulator of HO-1 induction. Through the antioxidant, antiapoptotic, and antinflammatory properties of its metabolic products, HO-1 plays a key role in healthy cells in maintaining redox homeostasis and in preventing carcinogenesis. Nevertheless, several lines of evidence have highlighted the role of HO-1 in cancer progression and its expression correlates with tumor growth, aggressiveness, metastatic and angiogenetic potential, resistance to therapy, tumor escape, and poor prognosis, even though a tumor- and tissue-specific activity has been observed. In this review, we summarize the current literature regarding the pro-tumorigenic role of HO-1 dependent tumor progression as a promising target in anticancer strategy.

Emerging roles of Nrf2 signal in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) causes considerable mortality in the world. Owing to molecular biological progress, treatments in adenocarcinoma have evolved revolutionarily while those in squamous lung cancer remain unsatisfied. Recent studies revealed high-frequency alteration of Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-like factor 2 (Keap1/Nrf2) pathway within squamous lung cancer, attracting researchers to focus on this particular pathway. In NSCLC patients, deregulated Nrf2 signal is recognized as a common feature at both DNA and protein level. Emerging associations between Nrf2 and other pathways have been elucidated. MicroRNA was also implicated in the regulation of Nrf2. Agents activating or antagonizing Nrf2 showed an effect in preclinical researches, reflecting different effects of Nrf2 during tumor initiation and progression. Prognostic evaluation demonstrated a negative impact of Nrf2 signal on NSCLC patients’ survival. Considering the importance of Nrf2 signal in NSCLC, further studies are required in the future.

Induction of heme oxygenase-1 by hemin protects lung against orthotopic autologous liver transplantation-induced acute lung injury in rats

BACKGROUND

Post-liver transplantation acute lung injury (ALI) severely affects patients' survival, whereas the mechanism is unclear and effective therapy is lacking. The authors postulated that reperfusion-induced increased oxidative stress plays a critical role in mediating post-liver transplantation ALI and that induction of heme oxgenase-1 (HO-1), an enzyme with anti-oxidative stress properties, can confer effective protection of lung against ALI.

METHODS

Male Sprague-Dawley rats underwent autologous orthotopic liver transplantation (OALT) in the absence or presence of treatments with the selective HO-1 inducer (Hemin) or HO-1 inhibitor (ZnPP). Lung tissues were collected at 8 h after OALT, pathological scores and lung water content were evaluated; survival rate of rats was analyzed; protein expression of HO-1 was determined by western blotting, and nuclear translocation of Nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor(NF)-κB p65 were detected by Immunofluorescence staining. The inflammatory cytokines and oxidative indexes of lung tissue were determined.

RESULTS

In lungs harvested at the early stage i.e. 8 h after OALT, Hemin treatment significantly increased superoxide dismutase activities, and reduced malondialdehyde, hydrogen peroxide, interleukin-6, myeloperoxidase, and tumor necrosis factor-α production,which were associated with increased HO-1 protein expression and lower pathological scores and increased survival rate of rats. The underline mechanisms might associate with activation of Nrf2 and inhibition of NF-κB p65 nuclear translocation. However, these changes were aggravated by ZnPP.

CONCLUSIONS

Hemin pretreatment, by enhancing HO-1 induction, increased lung antioxidant capacity and reduced inflammatory stress,protected the lung from OALT-induced ALI at early stage of reperfusion.

Nrf2-heme oxygenase-1 axis in mucoepidermoid carcinoma of the lung: Antitumoral effects associated with down-regulation of matrix metalloproteinases

Lung mucoepidermoid carcinoma (MEC) is a very poorly characterized rare subtype of non-small-cell lung cancer (NSCLC) associated with more favorable prognoses than other forms of intrathoracic malignancies. We have previously identified that heme oxygenase-1 (HO-1, encoded by HMOX1) inhibits MEC tumor growth and modulates the transcriptome of microRNAs. Here we investigate the role of a major upstream regulator of HO-1 and a master regulator of cellular antioxidant responses, transcription factor Nrf2, in MEC biology. Nrf2 overexpression in the NCI-H292 MEC cell line mimicked the phenotype of HO-1 overexpressing cells, leading to inhibition of cell proliferation and migration and down-regulation of oncogenic miR-378. HMOX1 silencing identified HO-1 as a major mediator of Nrf2 action. Nrf2- and HO-1 overexpressing cells exhibited strongly diminished expression of multiple matrix metalloproteinases and inflammatory cytokine interleukin-1β, which was confirmed in an NCI-HO-1 xenograft model. Overexpression of HO-1 altered not only human MMP levels in tumor cells but also murine MMP levels within tumor microenvironment and metastatic niche. This could possibly contribute to decreased metastasis to the lungs and inhibitory effects of HO-1 on MEC tumor growth. Our profound transcriptome analysis and molecular characterization of the mucoepidermoid lung carcinoma helps to understand the specific clinical presentations of these tumors, emphasizing a unique antitumoral role of the Nrf2-HO-1 axis.

Utility of checklist to describe experimental methods for investigating molecular biomarkers

Introduction: In research articles, detailed description of experimental methods and reagents is fundamental for correct reproducibility of the published data. This becomes even more important when such data contribute to identify molecular targets and toxicity biomarkers whose role is crucial in the physiology and pathology of human health. Methods & Objectives: To achieve good reproducibility of data we took advantage of others’ experiences and analyzed molecular biology and immunodetection techniques in 32 journal articles investigating the human NRF2 and Keap1 genes involved in the cell response to oxidative stress. Results & Conclusions: In conclusion of the analysis, we assessed deficiency of information in the published methods, making it difficult to select appropriate protocols. Underlining the importance of assay reproducibility, this paper proposes the utility of a minimum information checklist of methods for biomarker detection.

HO-1/CO system in tumor growth, angiogenesis and metabolism - Targeting HO-1 as an anti-tumor therapy

Heme oxygenase-1 (HO-1, hmox-1) catalyzes the rate-limiting step in the heme degradation processes. Out of three by-products of HO-1 activity, biliverdin, iron ions and carbon monoxide (CO), the latter was mostly shown to mediate many beneficial HO-1 effects, including protection against oxidative injury, regulation of apoptosis, modulation of inflammation as well as contribution to angiogenesis. Mounting evidence suggests that HO-1/CO systemmay be of special benefit in protection inmany pathological conditions, like atherosclerosis or myocardial infarction. By contrast, the augmented expression of HO-1 in tumor tissues may have detrimental effect as HO-1 accelerates the formation of tumor neovasculature and provides the selective advantage for tumor cells to overcome the increased oxidative stress during tumorigenesis and during treatment. The inhibition of HO-1 has been proposed as an anti-cancer therapy, however, because of non-specific effects of known HO-1 inhibitors, the discovery of ideal drug lowering HO-1 expression/activity is still an open question. Importantly, in several types of cancer HO-1/CO system exerts opposite activities, making the possible treatment more complicated. All together indicates the complex role for HO-1/CO in various in vitro and in vivo conditions.

The antioxidant paradox: what are antioxidants and how should they be used in a therapeutic context for cancer

So-called antioxidants have yet to make a clinical impact on the treatment of human cancer. The reasons for this failure are several. First, many agents that are called antioxidants are truly antioxidants at a given dose, but this dose may not have been given in clinical trials. Second, many agents are not antioxidants at all. Third, not all tumors use reactive oxygen as a signaling mechanism. Finally, reactive oxygen inhibition is often insufficient to kill or regress a tumor cell by itself, but requires sequential introduction of a therapeutic agent for maximal effect. We hope to provide a framework for the logical use of these agents in cancer.

Cellular and molecular mechanisms of inflammation-induced angiogenesis

Blood vessel formation is a fundamental process for the development of organism and tissue regeneration. Of importance, angiogenesis occurring during postnatal development is usually connected with inflammation. Here, we review how molecular and cellular mechanisms underlying inflammatory reactions regulate angiogenesis. Inflamed tissues are characterized by hypoxic conditions and immune cell infiltration. In this review, we describe an interplay of hypoxia-inducible factors (HIFs), HIF1 and HIF2, as well as NF-κB and nitric oxide in the regulation of angiogenesis. The mobilization of macrophages and the differential role of M1 and M2 macrophage subsets in angiogenesis are also discussed. Next, we present the current knowledge about microRNA regulation of inflammation in the context of new blood vessel formation. Finally, we describe how the mechanisms involved in inflammation influence tumor angiogenesis. We underlay and discuss the role of NF-E2-related factor 2/heme oxygenase-1 pathway as crucial in the regulation of inflammation-induced angiogenesis.

The Role of miR-378a in Metabolism, Angiogenesis, and Muscle Biology

MicroRNA-378a (miR-378a, previously known as miR-378) is one of the small noncoding RNA molecules able to regulate gene expression at posttranscriptional level. Its two mature strands, miR-378a-3p and miR-378a-5p, originate from the first intron of the peroxisome proliferator-activated receptor gamma, coactivator 1 beta (ppargc1b) gene encoding PGC-1β. Embedding in the sequence of this transcriptional regulator of oxidative energy metabolism implies involvement of miR-378a in metabolic pathways, mitochondrial energy homeostasis, and related biological processes such as muscle development, differentiation, and regeneration. On the other hand, modulating the expression of proangiogenic factors such as vascular endothelial growth factor, angiopoietin-1, or interleukin-8, influencing inflammatory reaction, and affecting tumor suppressors, such as SuFu and Fus-1, miR-378a is considered as a part of an angiogenic network in tumors. In the latter, miR-378a can evoke broader actions by enhancing cell survival, reducing apoptosis, and promoting cell migration and invasion. This review describes the current knowledge on miR-378a linking oxidative/lipid metabolism, muscle biology, and blood vessel formation.