Ets-1 is a transcriptional mediator of oncogenic nitric oxide signaling in estrogen receptor-negative breast cancer

Nitric oxide inhibits ten-eleven translocation DNA demethylases to regulate 5mC and 5hmC across the genome

DNA methylation at cytosine bases of eukaryotic DNA (5-methylcytosine, 5mC) is a heritable epigenetic mark that can regulate gene expression in health and disease. Enzymes that metabolize 5mC have been well-characterized, yet the discovery of endogenously produced signaling molecules that regulate DNA methyl-modifying machinery have not been described. Herein, we report that the free radical signaling molecule nitric oxide (NO) can directly inhibit the Fe(II)/2-OG-dependent DNA demethylases ten-eleven translocation (TET) and human AlkB homolog 2 (ALKBH2). Physiologic NO concentrations reversibly inhibited TET and ALKBH2 demethylase activity by binding to the mononuclear non-heme iron atom which formed a dinitrosyliron complex (DNIC) preventing cosubstrates (2-OG and O2) from binding. In cancer cells treated with exogenous NO, or cells endogenously synthesizing NO, there was a global increase in 5mC and 5-hydroxymethylcytosine (5hmC) in DNA, the substrates for TET, that could not be attributed to increased DNA methyltransferase activity. 5mC was also elevated in NO-producing cell-line-derived mouse xenograft and patient-derived xenograft tumors. Genome-wide DNA methylome analysis of cells chronically treated with NO (10 days) demonstrated enrichment of 5mC and 5hmC at gene-regulatory loci which correlated to changes in the expression of NO-regulated tumor-associated genes. Regulation of DNA methylation is distinctly different from canonical NO signaling and represents a novel epigenetic role for NO.

Non-canonical nitric oxide signalling and DNA methylation: Inflammation induced epigenetic alterations and potential drug targets

DNA methylation controls DNA accessibility to transcription factors and other regulatory proteins, thereby affecting gene expression and hence cellular identity and function. As epigenetic modifications control the transcriptome, epigenetic dysfunction is strongly associated with pathological conditions and ageing. The development of pharmacological agents that modulate the activity of major epigenetic proteins are in pre-clinical development and clinical use. However, recent publications have identified novel redox-based signalling pathways, and therefore novel drug targets, that may exert epigenetic effects. This review will discuss the recent developments in nitric oxide (NO) signalling on DNA methylation as well as potential epigenetic drug targets that have emerged from the intersection of inflammation/redox biology and epigenetic regulation.

Nitric oxide inhibits FTO demethylase activity to regulate N6-methyladenosine mRNA methylation

N6-methyladenosine (m6A) is the most abundant internal modification on eukaryotic mRNAs. Demethylation of m6A on mRNA is catalyzed by the enzyme fat mass and obesity-associated protein (FTO), a member of the nonheme Fe(II) and 2-oxoglutarate (2-OG)-dependent family of dioxygenases. FTO activity and m6A-mRNA are dysregulated in multiple diseases including cancers, yet endogenous signaling molecules that modulate FTO activity have not been identified. Here we show that nitric oxide (NO) is a potent inhibitor of FTO demethylase activity by directly binding to the catalytic iron center, which causes global m6A hypermethylation of mRNA in cells and results in gene-specific enrichment of m6A on mRNA of NO-regulated transcripts. Both cell culture and tumor xenograft models demonstrated that endogenous NO synthesis can regulate m6A-mRNA levels and transcriptional changes of m6A-associated genes. These results build a direct link between NO and m6A-mRNA regulation and reveal a novel signaling mechanism of NO as an endogenous regulator of the epitranscriptome.

S-Nitrosylation at the intersection of metabolism and autophagy: Implications for cancer

Metabolic plasticity, which determines tumour growth and metastasis, is now understood to be a flexible and context-specific process in cancer metabolism. One of the major pathways contributing to metabolic adaptations in eucaryotic cells is autophagy, a cellular degradation and recycling process that is activated during periods of starvation or stress to maintain metabolite and biosynthetic intermediate levels. Consequently, there is a close association between the metabolic adaptive capacity of tumour cells and autophagy-related pathways in cancer. Additionally, nitric oxide regulates protein function and signalling through S-nitrosylation, a post-translational modification that can also impact metabolism and autophagy. The primary objective of this review is to provide an up-to-date overview of the role of S-nitrosylation at the intersection of metabolism and autophagy in cancer. First, we will outline the involvement of S-nitrosylation in the metabolic adaptations that occur in tumours. Then, we will discuss the multifaceted role of autophagy in cancer, the interplay between metabolism and autophagy during tumour progression, and the contribution of S-nitrosylation to autophagic dysregulation in cancer. Finally, we will present insights into relevant therapeutic aspects and discuss prospects for the future.

Insights on the functional dualism of nitric oxide in the hallmarks of cancer

Nitric oxide (NO), a gaseous radical, governs a variety of physiological and pathological processes, including cancer, pro-inflammatory signalling, and vasodilation. The family of nitric oxide synthases (NOS), which comprises the constitutive forms, nNOS and eNOS, and the inducible form, iNOS, produces NO enzymatically. Additionally, NO can be generated non-enzymatically from the nitrate-nitrite-NO pathway. The anti- and pro-oxidant properties of NO and its functional dualism in cancer is due to its highly reactive nature. Numerous malignancies have NOS expression, which interferes with the tumour microenvironment to modulate the tumour's growth in both favourable and unfavourable ways. NO regulates a number of mechanisms in the tumour microenvironment, including metabolism, cell cycle, DNA repair, angiogenesis, and apoptosis/necrosis, depending on its concentration and spatiotemporal profile. This review focuses on the bi-modal impact of nitric oxide on the alteration of a few cancer hallmarks.

S-Nitrosylation in endothelial cells contributes to tumor cell adhesion and extravasation during breast cancer metastasis

BACKGROUND

Nitric oxide is produced by different nitric oxide synthases isoforms. NO activates two signaling pathways, one dependent on soluble guanylate cyclase and protein kinase G, and other where NO post-translationally modifies proteins through S-nitrosylation, which is the modification induced by NO in free-thiol cysteines in proteins to form S-nitrosothiols. High levels of NO have been detected in blood of breast cancer patients and increased NOS activity has been detected in invasive breast tumors compared to benign or normal breast tissue, suggesting a positive correlation between NO biosynthesis, degree of malignancy and metastasis. During metastasis, the endothelium plays a key role allowing the adhesion of tumor cells, which is the first step in the extravasation process leading to metastasis. This step shares similarities with leukocyte adhesion to the endothelium, and it is plausible that it may also share some regulatory elements. The vascular cell adhesion molecule-1 (VCAM-1) expressed on the endothelial cell surface promotes interactions between the endothelium and tumor cells, as well as leukocytes. Data show that breast tumor cells adhere to areas in the vasculature where NO production is increased, however, the mechanisms involved are unknown.

RESULTS

We report that the stimulation of endothelial cells with interleukin-8, and conditioned medium from breast tumor cells activates the S-nitrosylation pathway in the endothelium to induce leukocyte adhesion and tumor cell extravasation by a mechanism that involves an increased VCAM-1 cell surface expression in endothelial cells. We identified VCAM-1 as an S-nitrosylation target during this process. The inhibition of NO signaling and S-nitrosylation blocked the transmigration of tumor cells through endothelial monolayers. Using an in vivo model, the number of lung metastases was inhibited in the presence of the S-nitrosylation inhibitor N-acetylcysteine (NAC), which was correlated with lower levels of S-nitrosylated VCAM-1 in the metastases.

CONCLUSIONS

S-Nitrosylation in the endothelium activates pathways that enhance VCAM-1 surface localization to promote binding of leukocytes and extravasation of tumor cells leading to metastasis. NAC is positioned as an important tool that might be tested as a co-therapy against breast cancer metastasis.

Targeting Nitric Oxide: Say NO to Metastasis

Utilizing targeted therapies capable of reducing cancer metastasis, targeting chemoresistant and self-renewing cancer stem cells, and augmenting the efficacy of systemic chemo/radiotherapies is vital to minimize cancer-associated mortality. Targeting nitric oxide synthase (NOS), a protein within the tumor microenvironment, has gained interest as a promising therapeutic strategy to reduce metastatic capacity and augment the efficacy of chemo/radiotherapies in various solid malignancies. Our review highlights the influence of nitric oxide (NO) in tumor progression and cancer metastasis, as well as promising preclinical studies that evaluated NOS inhibitors as anticancer therapies. Lastly, we highlight the prospects and outstanding challenges of using NOS inhibitors in the clinical setting.

Interferon-gamma is quintessential for NOS2 and COX2 expression in ER- breast tumors that lead to poor outcome

A strong correlation between NOS2 and COX2 tumor expression and poor clinical outcomes in ER breast cancer has been established. However, the mechanisms of tumor induction of these enzymes are unclear. Analysis of The Cancer Genome Atlas (TCGA) revealed correlations between NOS2 and COX2 expression and Th1 cytokines. Herein, single-cell RNAseq analysis of TNBC cells shows potent NOS2 and COX2 induction by IFNγ combined with IL1β or TNFα. Given that IFNγ is secreted by cytolytic lymphocytes, which improve clinical outcomes, this role of IFNγ presents a dichotomy. To explore this conundrum, tumor NOS2, COX2, and CD8⁺ T cells were spatially analyzed in aggressive ER-, TNBC, and HER2 + breast tumors. High expression and clustering of NOS2-expressing tumor cells occurred at the tumor/stroma interface in the presence of stroma-restricted CD8⁺ T cells. High expression and clustering of COX2-expressing tumor cells extended into immune desert regions in the tumor core where CD8⁺ T cell penetration was limited or absent. Moreover, high NOS2-expressing tumor cells were proximal to areas with increased satellitosis, suggestive of cell clusters with a higher metastatic potential. Further in vitro experiments revealed that IFNγ + IL1β/TNFα increased the elongation and migration of treated tumor cells. This spatial analysis of the tumor microenvironment provides important insight into distinct neighborhoods where stroma-restricted CD8⁺ T cells exist proximal to NOS2-expressing tumor niches that could have increased metastatic potential.

Interferon-gamma is Quintessential for NOS2 and COX2 Expression in ER - Breast Tumors that Lead to Poor Outcome

A strong correlation between NOS2 and COX2 tumor expression and poor clinical outcomes in ER-breast cancer has been established. However, mechanisms of tumor induction of these enzymes are unclear. Analysis of The Cancer Genome Atlas (TCGA) revealed correlations between NOS2 and COX2 expression and Th1 cytokines. Herein, single cell RNAseq analysis of TNBC cells shows potent NOS2 and COX2 induction by IFNγ combined with IL1β or TNFα. Given that IFNγ is secreted by cytolytic lymphocytes, which improve clinical outcomes, this role of IFNγpresents a dichotomy. To explore this conundrum, tumor NOS2, COX2, and CD8 ⁺ T cells were spatially analyzed in aggressive ER-, TNBC, and HER2+ breast tumors. High expression and clustering of NOS2-expressing tumor cells occurred at the tumor/stroma interface in the presence of stroma-restricted CD8 ⁺ T cells. High expression and clustering of COX2-expressing tumor cells extended into immune desert regions in the tumor core where CD8 ⁺ T cell penetration was limited or absent. Moreover, high NOS2-expressing tumor cells were proximal to areas with increased satellitosis suggestive of cell clusters with a higher metastatic potential. Further in vitro experiments revealed that IFNγ+IL1β/TNFα increased elongation and migration of treated tumor cells. This spatial analysis of the tumor microenvironment provides important insight of distinct neighborhoods where stroma-restricted CD8 ⁺ T cells exist proximal to NOS2-expressing tumor niches that could have increased metastatic potential.

Targeted Therapy and Mechanisms of Drug Resistance in Breast Cancer

Breast cancer is the most common cause of cancer-related death in women worldwide. Multidrug resistance (MDR) has been a large hurdle in reducing BC death rates. The drug resistance mechanisms include increased drug efflux, enhanced DNA repair, senescence escape, epigenetic alterations, tumor heterogeneity, tumor microenvironment (TME), and the epithelial-to-mesenchymal transition (EMT), which make it challenging to overcome. This review aims to explain the mechanisms of resistance in BC further, identify viable drug targets, and elucidate how those targets relate to the progression of BC and drug resistance.

The Chemical Biology of NO that Regulates Oncogenic Signaling and Metabolism: NOS2 and Its Role in Inflammatory Disease

Nitric oxide (NO) and the enzyme that synthesizes it, nitric oxide synthase 2 (NOS2), have emerged as key players in inflammation and cancer. Expression of NOS2 in tumors has been correlated both with positive outcomes and with poor prognoses. The chemistry of NO is the major determinate to the biological outcome and the concentration of NO, which can range over five orders of magnitude, is critical in determining which pathways are activated. It is the activation of specific oncogenic and immunological mechanisms that shape the outcome. The kinetics of specific reactions determine the mechanisms of action. In this review, the relevant reactions of NO and related species are discussed with respect to these oncogenic and immunological signals.

The Breast Cancer Protooncogenes HER2, BRCA1 and BRCA2 and Their Regulation by the iNOS/NOS2 Axis

The expression of inducible nitric oxide synthase (iNOS; NOS2) and derived NO in various cancers was reported to exert pro- and anti-tumorigenic effects depending on the levels of expression and the tumor types. In humans, the breast cancer level of iNOS was reported to be overexpressed, to exhibit pro-tumorigenic activities, and to be of prognostic significance. Likewise, the expression of the oncogenes HER2, BRCA1, and BRCA2 has been associated with malignancy. The interrelationship between the expression of these protooncogenes and oncogenes and the expression of iNOS is not clear. We have hypothesized that there exist cross-talk signaling pathways between the breast cancer protooncogenes, the iNOS axis, and iNOS-mediated NO mutations of these protooncogenes into oncogenes. We review the molecular regulation of the expression of the protooncogenes in breast cancer and their interrelationships with iNOS expression and activities. In addition, we discuss the roles of iNOS, HER2, BRCA1/2, and NO metabolism in the pathophysiology of cancer stem cells. Bioinformatic analyses have been performed and have found suggested molecular alterations responsible for breast cancer aggressiveness. These include the association of BRCA1/2 mutations and HER2 amplifications with the dysregulation of the NOS pathway. We propose that future studies should be undertaken to investigate the regulatory mechanisms underlying the expression of iNOS and various breast cancer oncogenes, with the aim of identifying new therapeutic targets for the treatment of breast cancers that are refractory to current treatments.

Gasotransmitters in the tumor microenvironment: Impacts on cancer chemotherapy (Review)

Nitric oxide, carbon monoxide and hydrogen sulfide are three endogenous gasotransmitters that serve a role in regulating normal and pathological cellular activities. They can stimulate or inhibit cancer cell proliferation and invasion, as well as interfere with cancer cell responses to drug treatments. Understanding the molecular pathways governing the interactions between these gases and the tumor microenvironment can be utilized for the identification of a novel technique to disrupt cancer cell interactions and may contribute to the conception of effective and safe cancer therapy strategies. The present review discusses the effects of these gases in modulating the action of chemotherapies, as well as prospective pharmacological and therapeutic interfering approaches. A deeper knowledge of the mechanisms that underpin the cellular and pharmacological effects, as well as interactions, of each of the three gases could pave the way for therapeutic treatments and translational research.

A Description of the Hemolytic Component in Sickle Leg Ulcer: The Role of Circulating miR-199a-5p, miR-144, and miR-126

Sickle leg ulcers (SLU) are malleoli lesions with exuberant hemolytic pathophysiology. The microRNAs are potential genetic biomarkers for several pathologies. Thereby, we aimed to assess the expression of circulating miR-199a-5p, miR-144, and miR-126 in association with hemolytic biomarkers in SLU. This cross-sectional study included 69 patients with sickle cell disease, 52 patients without SLU (SLU-) and 17 patients with active SLU or previous history (SLU+). The results demonstrated elevated expression of circulating miR-199a-5p and miR-144 in SLU+ patients while miR-126 expression was reduced. Circulating miR-199a-5p and miR-144 were associated with hemolytic biomarkers such as LDH, indirect bilirubin, AST, GGT, iron, ferritin, RBC, hemoglobin, and NOm, in addition to association with impaired clinical profile of SLU. Furthermore, in silico analyses indicated interactions of miR-199a-5p with HIF1A, Ets-1, and TGFB2 genes, which are associated with vasculopathy and reduced NO. In contrast, miR-126 was associated with an attenuating clinical profile of SLU, in addition to not characterizing hemolysis. In summary, this study demonstrates, for the first time, that hemolytic mechanism in SLU can be characterized by circulating miR-199a-5p and miR-144. The circulating miR-126 may play a protective role in SLU. Thus, these microRNAs can support to establish prognosis and therapeutic strategy in SLU.

Pillars and Gaps of S-Nitrosylation-Dependent Epigenetic Regulation in Physiology and Cancer

Nitric oxide (NO) is a diffusible signaling molecule produced by three isoforms of nitric oxide synthase, which release NO during the metabolism of the amino acid arginine. NO participates in pathophysiological responses of many different tissues, inducing concentration-dependent effect. Indeed, while low NO levels generally have protective effects, higher NO concentrations induce cytotoxic/cytostatic actions. In recent years, evidences have been accumulated unveiling S-nitrosylation as a major NO-dependent post-translational mechanism ruling gene expression. S-nitrosylation is a reversible, highly regulated phenomenon in which NO reacts with one or few specific cysteine residues of target proteins generating S-nitrosothiols. By inducing this chemical modification, NO might exert epigenetic regulation through direct effects on both DNA and histones as well as through indirect actions affecting the functions of transcription factors and transcriptional co-regulators. In this light, S-nitrosylation may also impact on cancer cell gene expression programs. Indeed, it affects different cell pathways and functions ranging from the impairment of DNA damage repair to the modulation of the activity of signal transduction molecules, oncogenes, tumor suppressors, and chromatin remodelers. Nitrosylation is therefore a versatile tool by which NO might control gene expression programs in health and disease.

Clinical Value and Potential Mechanism of miRNA-33a-5p in Lung Squamous Cell Carcinoma

This study is aimed at thoroughly exploring the expression status, clinical significance, and underlying molecular mechanism of miRNA-33a-5p in lung squamous cell carcinoma (LUSC). Here, we detected miRNA-33a-5p in 20 samples from patients with LUSCs and 20 matching non-LUSC specimens by in-house quantitative real-time PCR (RT-qPCR). Relationship between miRNA-33a-5p expression and clinicopathological traits was investigated from materials derived from miRNA sequencing and miRNA microarrays. A pool standard mean difference (SMD) and summary receiver operating characteristic curves (SROC) were calculated to evaluate the integrated expression value of miRNA-33a-5p in LUSC. Twelve online platforms were applied to select potential target genes of miRNA-33a-5p. The differentially expressed genes (DEGs) of LUSC and the candidate target genes of miRNA-33a-5p were overlapped to acquire a set of specific genes for further analyses of the Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and protein–protein interaction (PPI) network. miRNA-33a-5p overexpressed in LUSC was supported by 706 LUSC and 261 non-LUSC samples gathering from RT-qPCR, miRNA-seq, and public miRNA microarrays. The pooled SMD was 0.56 (95% CI: -0.01-1.05), and the area under the curve (AUC) of the SROC was 0.78 (95% CI: 0.74-0.82). A total of 240 genes were identified as potential target genes of miRNA-33a-5p for functional enrichment analyses; the results suggested that these target genes may participate in several vital biological processes that promote the proliferation and progression of LUSC. miRNA-33a-5p may play an essential role in the occurrence and development of LUSC by targeting hub genes (ETS1, EDNRB, CYR61, and LRRK2) derived from the PPI network. In summary, our results indicated that miRNA-33a-5p may contribute as a prospective therapeutic target in LUSC.

Nitric Oxide and Cancer: When to Give and When to Take Away?

The mechanistic roles of nitric oxide (NO) during cancer progression have been important considerations since its discovery as an endogenously generated free radical. Nonetheless, the impacts of this signaling molecule can be seemingly contradictory, being both pro-and antitumorigenic, which complicates the development of cancer treatments based on the modulation of NO fluxes in tumors. At a fundamental level, low levels of NO drive oncogenic pathways, immunosuppression, metastasis, and angiogenesis, while higher levels lead to apoptosis and reduced hypoxia and also sensitize tumors to conventional therapies. However, clinical outcome depends on the type and stage of the tumor as well as the tumor microenvironment. In this Viewpoint, the current understanding of the concentration, spatial, and temporal dependence of responses to NO is correlated with potential treatment and prevention technologies and strategies.

Nitrosative Stress and Human Disease: Therapeutic Potential of Denitrosylation

Proteins dynamically contribute towards maintaining cellular homeostasis. Posttranslational modification regulates the function of target proteins through their immediate activation, sudden inhibition, or permanent degradation. Among numerous protein modifications, protein nitrosation and its functional relevance have emerged. Nitrosation generally initiates nitric oxide (NO) production in association with NO synthase. NO is conjugated to free thiol in the cysteine side chain (S-nitrosylation) and is propagated via the transnitrosylation mechanism. S-nitrosylation is a signaling pathway frequently involved in physiologic regulation. NO forms peroxynitrite in excessive oxidation conditions and induces tyrosine nitration, which is quite stable and is considered irreversible. Two main reducing systems are attributed to denitrosylation: glutathione and thioredoxin (TRX). Glutathione captures NO from S-nitrosylated protein and forms S-nitrosoglutathione (GSNO). The intracellular reducing system catalyzes GSNO into GSH again. TRX can remove NO-like glutathione and break down the disulfide bridge. Although NO is usually beneficial in the basal context, cumulative stress from chronic inflammation or oxidative insult produces a large amount of NO, which induces atypical protein nitrosation. Herein, we (1) provide a brief introduction to the nitrosation and denitrosylation processes, (2) discuss nitrosation-associated human diseases, and (3) discuss a possible denitrosylation strategy and its therapeutic applications.

Melatonin, Its Metabolites and Their Interference with Reactive Nitrogen Compounds

Melatonin and several of its metabolites are interfering with reactive nitrogen. With the notion of prevailing melatonin formation in tissues that exceeds by far the quantities in blood, metabolites come into focus that are poorly found in the circulation. Apart from their antioxidant actions, both melatonin and N¹-acetyl-5-methoxykynuramine (AMK) downregulate inducible and inhibit neuronal NO synthases, and additionally scavenge NO. However, the NO adduct of melatonin redonates NO, whereas AMK forms with NO a stable product. Many other melatonin metabolites formed in oxidative processes also contain nitrosylatable sites. Moreover, AMK readily scavenges products of the CO₂-adduct of peroxynitrite such as carbonate radicals and NO₂. Protein AMKylation seems to be involved in protective actions.

Nitric Oxide Modulates Metabolic Processes in the Tumor Immune Microenvironment

The metabolic requirements and functions of cancer and normal tissues are vastly different. Due to the rapid growth of cancer cells in the tumor microenvironment, distorted vasculature is commonly observed, which creates harsh environments that require rigorous and constantly evolving cellular adaption. A common hallmark of aggressive and therapeutically resistant tumors is hypoxia and hypoxia-induced stress markers. However, recent studies have identified alterations in a wide spectrum of metabolic pathways that dictate tumor behavior and response to therapy. Accordingly, it is becoming clear that metabolic processes are not uniform throughout the tumor microenvironment. Metabolic processes differ and are cell type specific where various factors promote metabolic heterogeneity within the tumor microenvironment. Furthermore, within the tumor, these metabolically distinct cell types can organize to form cellular neighborhoods that serve to establish a pro-tumor milieu in which distant and spatially distinct cellular neighborhoods can communicate via signaling metabolites from stroma, immune and tumor cells. In this review, we will discuss how biochemical interactions of various metabolic pathways influence cancer and immune microenvironments, as well as associated mechanisms that lead to good or poor clinical outcomes.

S-Nitrosylation in Tumor Microenvironment

S-nitrosylation is a selective and reversible post-translational modification of protein thiols by nitric oxide (NO), which is a bioactive signaling molecule, to exert a variety of effects. These effects include the modulation of protein conformation, activity, stability, and protein-protein interactions. S-nitrosylation plays a central role in propagating NO signals within a cell, tissue, and tissue microenvironment, as the nitrosyl moiety can rapidly be transferred from one protein to another upon contact. This modification has also been reported to confer either tumor-suppressing or tumor-promoting effects and is portrayed as a process involved in every stage of cancer progression. In particular, S-nitrosylation has recently been found as an essential regulator of the tumor microenvironment (TME), the environment around a tumor governing the disease pathogenesis. This review aims to outline the effects of S-nitrosylation on different resident cells in the TME and the diverse outcomes in a context-dependent manner. Furthermore, we will discuss the therapeutic potentials of modulating S-nitrosylation levels in tumors.

Vorinostat exhibits anticancer effects in triple-negative breast cancer cells by preventing nitric oxide-driven histone deacetylation

Triple-negative breast cancers (TNBC) that produce nitric oxide (NO) are more aggressive, and the expression of the inducible form of nitric oxide synthase (NOS2) is a negative prognostic indicator. In these studies, we set out to investigate potential therapeutic strategies to counter the tumor-permissive properties of NO. We found that exposure to NO increased proliferation of TNBC cells and that treatment with the histone deacetylase inhibitor Vorinostat (SAHA) prevented this proliferation. When histone acetylation was measured in response to NO and/or SAHA, NO significantly decreased acetylation on histone 3 lysine 9 (H3K9ac) and SAHA increased H3K9ac. If NO and SAHA were sequentially administered to cells (in either order), an increase in acetylation was observed in all cases. Mechanistic studies suggest that the "deacetylase" activity of NO does not involve S-nitrosothiols or soluble guanylyl cyclase activation. The observed decrease in histone acetylation by NO required the interaction of NO with cellular iron pools and may be an overriding effect of NO-mediated increases in histone methylation at the same lysine residues. Our data revealed a novel pathway interaction of Vorinostat and provides new insight in therapeutic strategy for aggressive TNBCs.

Nitric Oxide and S-Nitrosylation in Cancers: Emphasis on Breast Cancer

Nitric oxide (NO) is a ubiquitous, endogenously produced, water-soluble signaling molecule playing critical roles in physiological processes. Nitric oxide plays pleiotropic roles in cancer and, depending on its local concentration, may lead to either tumor progression or tumor suppression. Addition of NO group to a cysteine residue within a protein, termed as S-nitrosylation, plays diverse regulatory roles and affects processes such as metabolism, apoptosis, protein phosphorylation, and regulation of transcription factors. The process of S-nitrosylation has been associated with development of different cancers, including breast cancer. The present review discusses different mechanisms through which NO acts, with special emphasis on breast cancers, and provides detailed insights into reactive nitrogen species, posttranslational modifications of proteins mediated by NO, dual nature of NO in cancers, and the implications of S-nitrosylation in cancers. Our review will generate interest in exploring molecular regulation by NO in different cancers and will have significant therapeutic implications in the management and treatment of breast cancer.

Anti-proliferative and immunomodulatory activities of fractions from methanol root extract of Abrus precatorius L

Background

Abrus precatorius possesses various therapeutic properties including anticancer potentials. This study evaluated the anti-proliferative activities of fractions of methanol root extract of A. precatorius on breast and cervical cancer cells and their immunomodulatory effect. Phytochemical screening was done by FTIR and GCMS. In vitro anti-proliferative effect was evaluated on human breast cancer (AU565) and cervical cancer (HeLa) cells and on murine fibroblast (NIH 3 T3) cells. Antioxidant activity was performed via DPPH radical scavenging assay. The immunomodulatory potential of fractions was evaluated by inhibition of phagocytes oxidative burst (ROS), Nitric oxide (NO) and proinflammatory cytokine TNF-α.

Results

A. precatorius fractions showed different chemical groups and were somewhat selective in antiproliferative activity against studied cancer cells. Ethyl acetate fraction showed the most significant antiproliferative activity with IC50 values of 18.10 μg/mL and 11.89 μg/mL against AU565 and HeLa cells respectively. Hexane fraction significantly (p < 0.05) inhibited HeLa cells (IC50 18.24 ± 0.16 μg/mL), whereas aqueous fraction showed mild inhibition (IC50 46.46 ± 0.14 μg/mL) on AU565 cell proliferation. All fractions showed no cytotoxicity against NIH-3 T3 murine fibroblast normal cells. All fractions showed potent and significant (p < 0.001) DPPH radical scavenging activity as well as suppressed phagocytic oxidative burst. Hexane (< 1 μg/mL), ethyl acetate (< 1 μg/mL), and butanol (5.74 μg/mL) fractions potently inhibited the cytokine TNF- α, hexane (< 1 μg/mL) and ethyl acetate (< 1 μg/mL) fractions also potently inhibited NO.

Conclusions

The antiproliferative activities and suppressive effect on the phagocytic oxidative burst, NO and proinflammatory cytokine might be due to the synergistic actions of bioactive compounds especially flavonoids present in the assayed fractions and therefore, suggest chemotherapeutic use of A. precatorius in cancer treatment.

Molecular Mechanisms of Nitric Oxide in Cancer Progression, Signal Transduction, and Metabolism

SIGNIFICANCE

Cancer is a complex disease, which not only involves the tumor but its microenvironment comprising different immune cells as well. Nitric oxide (NO) plays specific roles within tumor cells and the microenvironment and determines the rate of cancer progression, therapy efficacy, and patient prognosis. Recent Advances: Key understanding of the processes leading to dysregulated NO flux within the tumor microenvironment over the past decade has provided better understanding of the dichotomous role of NO in cancer and its importance in shaping the immune landscape. It is becoming increasingly evident that nitric oxide synthase 2 (NOS2)-mediated NO/reactive nitrogen oxide species (RNS) are heavily involved in cancer progression and metastasis in different types of tumor. More recent studies have found that NO from NOS2+ macrophages is required for cancer immunotherapy to be effective.

CRITICAL ISSUES

NO/RNS, unlike other molecules, are unique in their ability to target a plethora of oncogenic pathways during cancer progression. In this review, we subcategorize the different levels of NO produced by cells and shed light on the context-dependent temporal effects on cancer signaling and metabolic shift in the tumor microenvironment.

FUTURE DIRECTIONS

Understanding the source of NO and its spaciotemporal profile within the tumor microenvironment could help improve efficacy of cancer immunotherapies by improving tumor infiltration of immune cells for better tumor clearance.

S-nitrosylation and its role in breast cancer angiogenesis and metastasis

S-nitrosylation, the modification by nitric oxide of free sulfhydryl groups in cysteines, has become an important regulatory mechanism in carcinogenesis and metastasis. S-nitrosylation of targets in tumor cells contributes to metastasis regulating epithelial to mesenchymal transition, migration and invasion. In the tumor environment, the role of S-nitrosylation in endothelium has not been addressed; however, the evidence points out that S-nitrosylation of endothelial proteins may regulate angiogenesis, adhesion of tumor cells to the endothelium, intra and extravasation of tumor cells and contribute to metastasis.

Posttranslational Modifications of RAS Proteins

The three human RAS genes encode four proteins that play central roles in oncogenesis by acting as binary molecular switches that regulate signaling pathways for growth and differentiation. Each is subject to a set of posttranslational modifications (PTMs) that modify their activity or are required for membrane targeting. The enzymes that catalyze the various PTMs are potential targets for anti-RAS drug discovery. The PTMs of RAS proteins are the focus of this review.

Computational Structural Biology of S-nitrosylation of Cancer Targets

Nitric oxide (NO) plays an essential role in redox signaling in normal and pathological cellular conditions. In particular, it is well known to react in vivo with cysteines by the so-called S-nitrosylation reaction. S-nitrosylation is a selective and reversible post-translational modification that exerts a myriad of different effects, such as the modulation of protein conformation, activity, stability, and biological interaction networks. We have appreciated, over the last years, the role of S-nitrosylation in normal and disease conditions. In this context, structural and computational studies can help to dissect the complex and multifaceted role of this redox post-translational modification. In this review article, we summarized the current state-of-the-art on the mechanism of S-nitrosylation, along with the structural and computational studies that have helped to unveil its effects and biological roles. We also discussed the need to move new steps forward especially in the direction of employing computational structural biology to address the molecular and atomistic details of S-nitrosylation. Indeed, this redox modification has been so far an underappreciated redox post-translational modification by the computational biochemistry community. In our review, we primarily focus on S-nitrosylated proteins that are attractive cancer targets due to the emerging relevance of this redox modification in a cancer setting.

ETS1 is associated with cisplatin resistance through IKKα/NF-κB pathway in cell line MDA-MB-231

Background

Platinum-based drugs are used extensively in neoadjuvant chemotherapy for triple-negative breast cancer (TNBC), but their use can be limited by resistance. In this study, we established cisplatin (DDP) resistant TNBC cells to investigate the potential relationship among ETS1, IKKα/NF-κB and resistance.

Methods

The sensitivity was evaluated by MTT, apoptosis analysis. The intracellular DDP concentration difference was tested by inductively coupled plasma mass spectrometry (ICP-MS) method. Molecular pathological mechanism of DDP resistance was explored by microarray analysis and PPI network analysis. The ETS1, NF-κB signaling change were assessed by western blot and q-PCR in vitro and vivo. The existing binds between ETS1 and the core IKKα promoter were found by luciferase assay and chromatin immunoprecipitation technique (ChIP).

Results

MDA-MB-231/DDP (231/DDP) cell had a higher IC₅₀ value of cisplatin, lower intracellular DDP concentration, and lower apoptosis ratio than MDA-MB-231 (231/wt) cell line treated with DDP. Increased ABC transporters were induced by the activation of NF-κB pathway in 231/DDP cells. ETS1, RPL6, RBBP8, BIRC2, PIK3A and RARS were six important genes for DDP-resistance based on PPI network and expression validation. Protein expression of ETS1 and IKKα were significantly up-regulated in 231/DDP cells. However, inhibition of ETS1 expression enhances chemo-sensitivity to DDP and reversed the activation of NF-κB pathway in 231/DDP cells and subcutaneous transplantation tumor in vivo. Moreover, there is existing binds between ETS1 and the core IKKα promoter though luciferase assay and ChIP.

Conclusion

This study enables us to understand the functions of ETS1 in TNBC chemotherapy and suggests that ETS1 could be used as a novel marker of poor response to DDP and a potential therapeutic target for TNBC chemotherapy.

Elevated mitochondrial SLC25A29 in cancer modulates metabolic status by increasing mitochondria-derived nitric oxide

Warburg effect has been recognized as a hallmark of cancer cells for many years, but its modulation mechanism remains a great focus. Our current study found a member of solute carrier family 25 (SLC25A29), the main arginine transporter on mitochondria, significantly elevated in various cancer cells. Knockout of SLC25A29 by CRISPR/Cas9 inhibited proliferation and migration of cancer cells both in vitro and in vivo. SLC25A29-knockout cells also showed an altered metabolic status with enhanced mitochondrial respiration and reduced glycolysis. All of above impacts could be reversed after rescuing SLC25A29 expression in SLC25A29-knockout cells. Arginine is transported into mitochondria partly for nitric oxide (NO) synthesis. Deletion of SLC25A29 resulted in severe decrease of NO production, indicating that the mitochondria is a significant source of NO. SLC25A29-knockout cells dramatically altered the variation of metabolic processes, whereas addition of arginine failed to reverse the effect, highlighting the necessity of transporting arginine into mitochondria by SLC25A29. In conclusion, aberrant elevated SLC25A29 in cancer functioned to transport more arginine into mitochondria, improved mitochondria-derived NO levels, thus modulated metabolic status to facilitate increased cancer progression.

Immunology Comes Full Circle in Melanoma While Specific Immunity Is Unleashed to Eliminate Metastatic Disease, Inflammatory Products of Innate Immunity Promote Resistance

Melanoma and many other cancers often express cells and molecular features of inflammation. Intrinsic to melanoma is the expression of a continuous cycle of cytokines and oxidative stress markers. The oxidative stress of inflammation is proposed to drive a metastatic process, not only of DNA adducts and crosslinks, but also of posttranslational oxidative modifications to lipids and proteins that we argue support growth and survival. Fortunately, numerous antioxidant agents are available clinically and we further propose that the pharmacological attenuation of these inflammatory processes, particularly the reactive nitrogen species, will restore the cancer cells to an apoptosis-permissive and growth-inhibitory state. Experimental model data using a small-molecule arginine antagonist that prevents enzymatic production of nitric oxide supports this view directly. I propose that the recognition, measurement, and regulation of such carcinogenic inflammation be considered as part of the approach to the treatment of cancer.

Targeting nitric oxide and NMDA receptor-associated pathways in treatment of high grade glial tumors. Hypotheses for nitro-memantine and nitrones

Glioblastoma multiforme (GBM) is a devastating brain cancer with no curative treatment. Targeting Nitric Oxide (NO) and glutamatergic pathways may help as adjunctive treatments in GBM. NO at low doses promotes tumorigenesis, while at higher levels (above 300 nM) triggers apoptosis. Gliomas actively secrete high amounts of glutamate which activates EGR signaling and mediates degradation of peritumoral tissues via excitotoxic injury. Memantine inhibits NMDA-subtype of glutamate receptors (NMDARs) and induces autophagic death of glioma cells in vitro and blocks glioma growth in vivo. Nitro-memantines may exert further benefits by limiting NMDAR signaling and by delivery of NO to the areas of excessive NMDAR activity leading NO-accumulation at tumoricidal levels within gliomas. Due to the duality of NO in tumorigenesis, agents which attenuate NO levels may also act beneficial in treatment of GBM. Nitrone compounds including N-tert-Butyl-α-phenylnitrone (PBN) and its disulfonyl-phenyl derivative, OKN-007 suppress free radical formation in experimental cerebral ischemia. OKN-007 failed to show clinical efficacy in stroke, but trials demonstrated its high biosafety in humans including elderly subjects. PBN inhibits the signaling pathways of NF-κB, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX). In animal models of liver cancer and glioblastoma, OKN-007 seemed more efficient than PBN in suppression of cell proliferation, microvascular density and in induction of apoptosis. OKN-007 also inhibits SULF2 enzyme, which promotes tumor growth via versatile pathways. We assume that nitromemantines may be more beneficial concomitant with chemo-radiotherapy while nitrones alone may act useful in suppressing basal tumor growth and angiogenesis.

Nitric Oxide Synthase-2-Derived Nitric Oxide Drives Multiple Pathways of Breast Cancer Progression

SIGNIFICANCE

Breast cancer is the second leading cause of cancer-related deaths among women in the United States. Development and progression of malignancy are associated with diverse cell signaling pathways that control cell proliferation, survival, motility, invasion, and metastasis. Recent Advances: An increasing number of clinical studies have implicated a strong relationship between elevated tumor nitric oxide synthase-2 (NOS2) expression and poor patient survival.

CRITICAL ISSUES

Herein, we review what we believe to be key mechanisms in the role(s) of NOS2-derived nitric oxide (NO) as a driver of breast cancer disease progression. High NO increases cyclooxygenase-2 activity, hypoxia inducible factor-1 alpha protein stabilization, and activation of important cell signaling pathways, including phosphoinositide 3-kinase/protein kinase B, mitogen-activated protein kinase, epidermal growth factor receptor, and Ras, through post-translational protein modifications. Moreover, dysregulated NO flux within the tumor microenvironment has other important roles, including the promotion of angiogenesis and modulation of matrix metalloproteinase/tissue inhibitor matrix metalloproteinase associated with tumor progression.

FUTURE DIRECTIONS

The elucidation of these and other NO-driven pathways implicates NOS2 as a key driver of breast cancer disease progression and provides a new perspective in the identification of novel targets that may be therapeutically beneficial in the treatment of estrogen receptor-negative disease. Antioxid. Redox Signal. 26, 1044-1058.

Nitric oxide: what's new to NO?

Nitric oxide (NO) is one of the critical components of the vasculature, regulating key signaling pathways in health. In macrovessels, NO functions to suppress cell inflammation as well as adhesion. In this way, it inhibits thrombosis and promotes blood flow. It also functions to limit vessel constriction and vessel wall remodeling. In microvessels and particularly capillaries, NO, along with growth factors, is important in promoting new vessel formation, a process termed angiogenesis. With age and cardiovascular disease, animal and human studies confirm that NO is dysregulated at multiple levels including decreased production, decreased tissue half-life, and decreased potency. NO has also been implicated in diseases that are related to neurotransmission and cancer although it is likely that these processes involve NO at higher concentrations and from nonvascular cell sources. Conversely, NO and drugs that directly or indirectly increase NO signaling have found clinical applications in both age-related diseases and in younger individuals. This focused review considers recently reported advances being made in the field of NO signaling regulation at several levels including enzymatic production, receptor function, interacting partners, localization of signaling, matrix-cellular and cell-to-cell cross talk, as well as the possible impact these newly described mechanisms have on health and disease.

[NO and cancer: itinerary of a double agent]

Protein S-nitrosylation is now recognized as a ubiquitous regulatory mechanism. Like any post-translational modifications, S-nitrosylation is critical for the control of numerous cellular processes. It is now clear that S-nitrosylation is playing a double game, enhancing or inhibiting the tumor growth or the induction of cell death. Thanks to research aimed at demonstrating NO cytotoxic effects, new therapeutic strategies based on NO donor drugs have emerged. Although therapeutic NO donors can target a large number of proteins, the cellular mechanism is still not fully understood. This review reflects the current state of knowledge on S-nitrosylated proteins that take part of the oncogenic and apoptotic signaling, putting forward proteins with potential interest in cancer therapy.

Review of Triple Negative Breast Cancer and the Impact of Inducible Nitric Oxide Synthase on Tumor Biology and Patient Outcomes

Triple negative breast cancers (TNBCs), which are defined as estrogen-receptor, progesterone-receptor, and HER2-receptor negative, account for 10-20% of breast cancers, and they are associated with early metastasis, chemotherapeutic resistance, and poor survival rates. One aspect of TNBC that complicates its prognosis and the development of new molecular therapeutic targets is its clinical and molecular heterogeneity. Herein we compare TNBC and basal cytokeratin-positive breast cancers. We examine the different TNBC molecular subtypes, based on gene expression profiling, which include basal-like, mesenchymal, and luminal androgen receptors, in the context of their biology and impact on TNBC prognosis. We explore the potential role of inducible nitric oxide synthase (iNOS) in TNBC tumor biology and treatment responses. iNOS has been shown to induce p53 mutation accumulation, basal-like gene signature enrichment, and transactivation of the epidermal growth factor receptor (EGFR) via S-nitrosylation, all of which are key components of TNBC biology. Moreover, iNOS predicts poor outcome in TNBC, and iNOS inhibitors show efficacy against TNBC when used in combination with chemotherapy. We discuss molecular targeted approaches, including EGFR, PARP, and VEGF inhibitors and immunotherapeutics, that are under consideration for the treatment of TNBC and what role, if any, iNOS may play in their success.

Biological signaling by small inorganic molecules

Small redox active molecules such as reactive nitrogen and oxygen species and hydrogen sulfide have emerged as important biological mediators that are involved in various physiological and pathophysiological processes. Advancement in understanding of cellular mechanisms that tightly regulate both generation and reactivity of these molecules is central to improved management of various disease states including cancer and cardiovascular dysfunction. Imbalance in the production of redox active molecules can lead to damage of critical cellular components such as cell membranes, proteins and DNA and thus may trigger the onset of disease. These small inorganic molecules react independently as well as in a concerted manner to mediate physiological responses. This review provides a general overview of the redox biology of these key molecules, their diverse chemistry relevant to physiological processes and their interrelated nature in cellular signaling.

PC-TraFF: identification of potentially collaborating transcription factors using pointwise mutual information

Background

Transcription factors (TFs) are important regulatory proteins that govern transcriptional regulation. Today, it is known that in higher organisms different TFs have to cooperate rather than acting individually in order to control complex genetic programs. The identification of these interactions is an important challenge for understanding the molecular mechanisms of regulating biological processes. In this study, we present a new method based on pointwise mutual information, PC-TraFF, which considers the genome as a document, the sequences as sentences, and TF binding sites (TFBSs) as words to identify interacting TFs in a set of sequences.

Results

To demonstrate the effectiveness of PC-TraFF, we performed a genome-wide analysis and a breast cancer-associated sequence set analysis for protein coding and miRNA genes. Our results show that in any of these sequence sets, PC-TraFF is able to identify important interacting TF pairs, for most of which we found support by previously published experimental results. Further, we made a pairwise comparison between PC-TraFF and three conventional methods. The outcome of this comparison study strongly suggests that all these methods focus on different important aspects of interaction between TFs and thus the pairwise overlap between any of them is only marginal.

Conclusions

In this study, adopting the idea from the field of linguistics in the field of bioinformatics, we develop a new information theoretic method, PC-TraFF, for the identification of potentially collaborating transcription factors based on the idiosyncrasy of their binding site distributions on the genome. The results of our study show that PC-TraFF can succesfully identify known interacting TF pairs and thus its currently biologically uncorfirmed predictions could provide new hypotheses for further experimental validation. Additionally, the comparison of the results of PC-TraFF with the results of previous methods demonstrates that different methods with their specific scopes can perfectly supplement each other. Overall, our analyses indicate that PC-TraFF is a time-efficient method where its algorithm has a tractable computational time and memory consumption.

The PC-TraFF server is freely accessible at http://pctraff.bioinf.med.uni-goettingen.de/

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0827-2) contains supplementary material, which is available to authorized users.

Nitric Oxide Regulates Gene Expression in Cancers by Controlling Histone Posttranslational Modifications

Altered nitric oxide (•NO) metabolism underlies cancer pathology, but mechanisms explaining many •NO-associated phenotypes remain unclear. We have found that cellular exposure to •NO changes histone posttranslational modifications (PTM) by directly inhibiting the catalytic activity of JmjC-domain containing histone demethylases. Herein, we describe how •NO exposure links modulation of histone PTMs to gene expression changes that promote oncogenesis. Through high-resolution mass spectrometry, we generated an extensive map of •NO-mediated histone PTM changes at 15 critical lysine residues on the core histones H3 and H4. Concomitant microarray analysis demonstrated that exposure to physiologic •NO resulted in the differential expression of over 6,500 genes in breast cancer cells. Measurements of the association of H3K9me2 and H3K9ac across genomic loci revealed that differential distribution of these particular PTMs correlated with changes in the level of expression of numerous oncogenes, consistent with epigenetic code. Our results establish that •NO functions as an epigenetic regulator of gene expression mediated by changes in histone PTMs.

P-cadherin and the journey to cancer metastasis

P-cadherin is a classical cell-to-cell adhesion molecule with a homeostatic function in several normal tissues. However, its behaviour in the malignant setting is notably dependent on the cellular context. In some tumour models, such as melanoma and oral squamous cell carcinoma, P-cadherin acts as a tumour suppressor, since its absence is associated with a more aggressive cancer cell phenotype; nevertheless, the overexpression of this molecule is linked to significant tumour promoting effects in the breast, ovarian, prostate, endometrial, skin, gastric, pancreas and colon neoplasms. Herein, we review the role of P-cadherin in cancer cell invasion, as well as in loco-regional and distant metastatic dissemination. We focus in P-cadherin signalling pathways that are activated to induce invasion and metastasis, as well as cancer stem cell properties. The signalling network downstream of P-cadherin is notably dependent on the cellular and tissue context and includes the activation of integrin molecules, receptor tyrosine kinases, small molecule GTPases, EMT transcription factors, and crosstalk with other cadherin family members. As new oncogenic molecular pathways mediated by P-cadherin are uncovered, putative therapeutic options can be tested, which will allow for the targeting of invasion or metastatic disease, depending on the tumour model.

Signaling and stress: The redox landscape in NOS2 biology

Nitric oxide (NO) has a highly diverse range of biological functions from physiological signaling and maintenance of homeostasis to serving as an effector molecule in the immune system. However, deleterious as well as beneficial roles of NO have been reported. Many of the dichotomous effects of NO and derivative reactive nitrogen species (RNS) can be explained by invoking precise interactions with different targets as a result of concentration and temporal constraints. Endogenous concentrations of NO span five orders of magnitude, with levels near the high picomolar range typically occurring in short bursts as compared to sustained production of low micromolar levels of NO during immune response. This article provides an overview of the redox landscape as it relates to increasing NO concentrations, which incrementally govern physiological signaling, nitrosative signaling and nitrosative stress-related signaling. Physiological signaling by NO primarily occurs upon interaction with the heme protein soluble guanylyl cyclase. As NO concentrations rise, interactions with nonheme iron complexes as well as indirect modification of thiols can stimulate additional signaling processes. At the highest levels of NO, production of a broader range of RNS, which subsequently interact with more diverse targets, can lead to chemical stress. However, even under such conditions, there is evidence that stress-related signaling mechanisms are triggered to protect cells or even resolve the stress. This review therefore also addresses the fundamental reactions and kinetics that initiate signaling through NO-dependent pathways, including processes that lead to interconversion of RNS and interactions with molecular targets.

INPP4B is an oncogenic regulator in human colon cancer

Inositol polyphosphate 4-phosphatase type II (INPP4B) negatively regulates phosphatidylinositol 3-kinase signaling and is a tumor suppressor in some types of cancers. However, we have found that it is frequently upregulated in human colon cancer cells. Here we show that silencing of INPP4B blocks activation of Akt and serum- and glucocorticoid-regulated kinase 3 (SGK3), inhibits colon cancer cell proliferation and retards colon cancer xenograft growth. Conversely, overexpression of INPP4B increases proliferation and triggers anchorage-independent growth of normal colon epithelial cells. Moreover, we demonstrate that the effect of INPP4B on Akt and SGK3 is associated with inactivation of phosphate and tensin homolog through its protein phosphatase activity and that the increase in INPP4B is due to Ets-1-mediated transcriptional upregulation in colon cancer cells. Collectively, these results suggest that INPP4B may function as an oncogenic driver in colon cancer, with potential implications for targeting INPP4B as a novel approach to treat this disease.

The role of the transcription factor Ets1 in carcinoma

Ets1 belongs to the large family of the ETS domain family of transcription factors and is involved in cancer progression. In most carcinomas, Ets1 expression is linked to poor survival. In breast cancer, Ets1 is primarily expressed in the triple-negative subtype, which is associated with unfavorable prognosis. Ets1 contributes to the acquisition of cancer cell invasiveness, to EMT (epithelial-to-mesenchymal transition), to the development of drug resistance and neo-angiogenesis. The aim of this review is to summarize the current knowledge on the functions of Ets1 in carcinoma progression and on the mechanisms that regulate Ets1 activity in cancer.

The diatom-derived aldehyde decadienal affects life cycle transition in the ascidian Ciona intestinalis through nitric oxide/ERK signalling

Polyunsaturated aldehydes (PUAs) are fatty-acid-derived metabolites produced by some microalgae, including different diatom species. PUAs are mainly produced as a wound-activated defence mechanism against microalgal predators or released from senescent cells at the end of a bloom. PUAs, including 2,4-trans-decadienal (DD), induce deleterious effects on embryonic and larval development of several planktonic and benthic organisms. Here, we report on the effects of DD on larval development and metamorphosis of the ascidian Ciona intestinalis. Ciona larval development is regulated by the cross-talking of different molecular events, including nitric oxide (NO) production, ERK activation and caspase 3-dependent apoptosis. We report that treatment with DD at the competence larval stage results in a delay in metamorphosis. DD affects redox balance by reducing total glutathione and NO levels. By biochemical and quantitative gene expression analysis, we identify the NO-signalling network affected by DD, including the upregulation of ERK phosphatase mkp1 and consequent reduction of ERK phosphorylation, with final changes in the expression of downstream ERK target genes. Overall, these results give new insights into the molecular pathways induced in marine organisms after exposure to PUAs during larval development, demonstrating that this aldehyde affects key checkpoints of larval transition from the vegetative to the reproductive life stage.

NOS Inhibition Modulates Immune Polarization and Improves Radiation-Induced Tumor Growth Delay

Nitric oxide synthases (NOS) are important mediators of progrowth signaling in tumor cells, as they regulate angiogenesis, immune response, and immune-mediated wound healing. Ionizing radiation (IR) is also an immune modulator and inducer of wound response. We hypothesized that radiation therapeutic efficacy could be improved by targeting NOS following tumor irradiation. Herein, we show enhanced radiation-induced (10 Gy) tumor growth delay in a syngeneic model (C3H) but not immunosuppressed (Nu/Nu) squamous cell carcinoma tumor-bearing mice treated post-IR with the constitutive NOS inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME). These results suggest a requirement of T cells for improved radiation tumor response. In support of this observation, tumor irradiation induced a rapid increase in the immunosuppressive Th2 cytokine IL10, which was abated by post-IR administration of L-NAME. In vivo suppression of IL10 using an antisense IL10 morpholino also extended the tumor growth delay induced by radiation in a manner similar to L-NAME. Further examination of this mechanism in cultured Jurkat T cells revealed L-NAME suppression of IR-induced IL10 expression, which reaccumulated in the presence of exogenous NO donor. In addition to L-NAME, the guanylyl cyclase inhibitors ODQ and thrombospondin-1 also abated IR-induced IL10 expression in Jurkat T cells and ANA-1 macrophages, which further suggests that the immunosuppressive effects involve eNOS. Moreover, cytotoxic Th1 cytokines, including IL2, IL12p40, and IFNγ, as well as activated CD8(+) T cells were elevated in tumors receiving post-IR L-NAME. Together, these results suggest that post-IR NOS inhibition improves radiation tumor response via Th1 immune polarization within the tumor microenvironment.

S-Nitrosylation in Organs of Mice Exposed to Low or High Doses of γ-Rays: The Modulating Effect of Iodine Contrast Agent at a Low Radiation Dose

The covalent addition of nitric oxide (NO^•) onto cysteine thiols, or S-nitrosylation, modulates the activity of key signaling proteins. The dysregulation of normal S-nitrosylation contributes to degenerative conditions and to cancer. To gain insight into the biochemical changes induced by low-dose ionizing radiation, we determined global S-nitrosylation by the “biotin switch” assay coupled with mass spectrometry analyses in organs of C57BL/6J mice exposed to acute 0.1 Gy of ¹³⁷Cs γ-rays. The dose of radiation was delivered to the whole body in the presence or absence of iopamidol, an iodinated contrast agent used during radiological examinations. To investigate whether similar or distinct nitrosylation patterns are induced following high-dose irradiation, mice were exposed in parallel to acute 4 Gy of ¹³⁷Cs γ rays. Analysis of modulated S-nitrosothiols (SNO-proteins) in freshly-harvested organs of animals sacrificed 13 days after irradiation revealed radiation dose- and contrast agent-dependent changes. The major results were as follows: (i) iopamidol alone had significant effects on S-nitrosylation in brain, lung and liver; (ii) relative to the control, exposure to 0.1 Gy without iopamidol resulted in statistically-significant SNO changes in proteins that differ in molecular weight in liver, lung, brain and blood plasma; (iii) iopamidol enhanced the decrease in S-nitrosylation induced by 0.1 Gy in brain; (iv) whereas a decrease in S-nitrosylation occurred at 0.1 Gy for proteins of ~50 kDa in brain and for proteins of ~37 kDa in liver, an increase was detected at 4 Gy in both organs; (v) mass spectrometry analyses of nitrosylated proteins in brain revealed differential modulation of SNO proteins (e.g., sodium/potassium-transporting ATPase subunit beta-1; beta tubulins; ADP-ribosylation factor 5) by low- and high-dose irradiation; and (vi) ingenuity pathway analysis identified major signaling networks to be modulated, in particular the neuronal nitric oxide synthase signaling pathway was differentially modulated by low- and high-dose γ-irradiation.

Inhibition of iNOS as a novel effective targeted therapy against triple-negative breast cancer

Introduction

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer with no effective targeted therapy. Inducible nitric oxide synthase (iNOS) is associated with poor survival in patients with breast cancer by increasing tumor aggressiveness. This work aimed to investigate the potential of iNOS inhibitors as a targeted therapy for TNBC. We hypothesized that inhibition of endogenous iNOS would decrease TNBC aggressiveness by reducing tumor initiation and metastasis through modulation of epithelial-mesenchymal transition (EMT)-inducing factors.

Methods

iNOS protein levels were determined in 83 human TNBC tissues and correlated with clinical outcome. Proliferation, mammosphere-forming efficiency, migration, and EMT transcription factors were assessed in vitro after iNOS inhibition. Endogenous iNOS targeting was evaluated as a potential therapy in TNBC mouse models.

Results

High endogenous iNOS expression was associated with worse prognosis in patients with TNBC by gene expression as well as immunohistochemical analysis. Selective iNOS (1400 W) and pan-NOS (L-NMMA and L-NAME) inhibitors diminished cell proliferation, cancer stem cell self-renewal, and cell migration in vitro, together with inhibition of EMT transcription factors (Snail, Slug, Twist1, and Zeb1). Impairment of hypoxia-inducible factor 1α, endoplasmic reticulum stress (IRE1α/XBP1), and the crosstalk between activating transcription factor 3/activating transcription factor 4 and transforming growth factor β was observed. iNOS inhibition significantly reduced tumor growth, the number of lung metastases, tumor initiation, and self-renewal.

Conclusions

Considering the effectiveness of L-NMMA in decreasing tumor growth and enhancing survival rate in TNBC, we propose a targeted therapeutic clinical trial by re-purposing the pan-NOS inhibitor L-NMMA, which has been extensively investigated for cardiogenic shock as an anti-cancer therapeutic.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-015-0527-x) contains supplementary material, which is available to authorized users.