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

Triple negative breast cancer cells exposed to aryl hydrocarbon receptor ligands hexachlorobenzene and chlorpyrifos activate endothelial cells

Breast cancer is currently one of the most prevalent cancers worldwide. The mechanisms by which pesticides can increase breast cancer risk are multiple and complex. We have previously observed that two aryl hydrocarbon receptor (AhR) agonists ‒pesticides hexachlorobenzene (HCB) and chlorpyrifos (CPF)‒ act on tumor progression, stimulating cell migration and invasion in vitro and tumor growth in animal models. Elevated levels of hypoxia inducible factor-1α (HIF-1α) are found in malignant breast tumors, and HIF-1α is known to induce proangiogenic factors such as vascular endothelial growth factor (VEGF), nitric oxide synthase-2 (NOS-2) and cyclooxygenase-2 (COX-2), which are fundamental in breast cancer progression. In this work, we studied HCB (0.005, 0.05, 0.5 and 5 μM) and CPF (0.05, 0.5, 5 and 50 μM) action on the expression of these proangiogenic factors in triple negative breast cancer cells MDA-MB-231, as well as the effect of their conditioned medium (CM) on endothelial cells. Exposure to pesticides increased HIF-1α and VEGF protein expression in an AhR-dependent manner. In addition, HCB and CPF boosted NOS-2 and COX-2 content and VEGF secretion in MDA-MB-231 cells. The treatment of endothelial cells with CM from tumor cells exposed to pesticides increased cell proliferation, migration, and tubule formation, enhancing both tubule length and branching points. Of note, these effects were VEGF-dependent, as they were blocked in the presence of a VEGF receptor-2 (VEGFR-2) inhibitor. In sum, our results highlight the harmful impact of HCB and CPF in modulating the interaction between breast cancer and endothelial cells and promoting angiogenesis.

Plateletcrit is predictive of clinical outcome and prognosis for early-stage breast cancer: A retrospective cohort study based on propensity score matching

PURPOSE

Breast cancer (BC) is diagnosed as the most common cancer in women in 2022 according to the American Cancer Society. It is essential to detect early and treat early. Several studies have shown that some blood parameters have important predictive value for BC. In this study, we aim to explore whether some immune-associated blood parameters are relevant to disease-free survival (DFS) in early-stage BC.

METHODS

A single-center, regression cohort study of 1490 patients with early-stage BC in Shanghai Cancer Center was conducted from January 2008 to December 2016. The patients were matched according to the ratio of 1:1 based on Propensity Score Matching (PSM). All patients who experienced disease progression were matched successfully. Thus, 58 pairs of subjects were obtained. Matched blood parameters were evaluated by paired samples t-test or Wilcoxon signed-rank test. Factors with statistical difference were further evaluated by stratified COX regression model.

RESULTS

Univariate analysis showed differences in platelet-related parameters (PLT, PCT, and PLR) and NLR between the two matched groups. However, stratified COX regression analysis, which ruled out the confounding effects of multiple factors, found that only PCT had prognostic value in early BC patients at baseline and study endpoint. Meanwhile, platelet-related parameters (PLT, MPV) and NLR were different in the progressive group by self before and after comparison. However, the multiple-factor analysis showed that only the NLR had prognostic value. ROC curve analysis indicated that the best sensitivity (65.45%) and specificity (78.18%) were obtained when the baseline PCT was 0.225. The optimal sensitivity (70.91%) and specificity (65.45%) were obtained when the PCT of disease progression was 0.215. The Kaplan-Meier curve was used to calculate the DFS rate based on the critical values of the two groups.

CONCLUSIONS

Some blood parameters have value to predict DFS in early-stage BC patients, especially platelet-associated parameters.

Nitric Oxide-Scavenging, Anti-Migration Effects, and Glycosylation Changes after Hemin Treatment of Human Triple-Negative Breast Cancer Cells: A Mechanistic Study

The enhanced expression of nitric oxide (•NO) synthase predicts triple-negative breast cancer outcome and its resistance to different therapeutics. Our earlier work demonstrated the efficiency of hemin to scavenge the intra- and extracellular •NO, proposing its potency as a therapeutic agent for inhibiting cancer cell migration. In continuation, the present work evaluates the effects of •NO on the migration of MDA-MB-231 cells and how hemin modulates the accompanied cellular behavior, focusing on the corresponding expression of cellular glycoproteins, migration-associated markers, and mitochondrial functions. We demonstrated for the first time that while •NO induced cell migration, hemin contradicted that by •NO-scavenging. This was in combination with modulation of the •NO-enhanced glycosylation patterns of cellular proteins with inhibition of the expression of specific proteins involved in the epithelial-mesenchymal transition. These effects were in conjunction with changes in the mitochondrial functions related to both •NO, hemin, and its nitrosylated product. Together, these results suggest that hemin can be employed as a potential anti-migrating agent targeting •NO-scavenging and regulating the expression of migration-associated proteins.

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.

GSNOR deficiency promotes tumor growth via FAK1 S-nitrosylation

Nitric oxide (NO) production in the tumor microenvironment is a common element in cancer. S-nitrosylation, the post-translational modification of cysteines by NO, is emerging as a key transduction mechanism sustaining tumorigenesis. However, most oncoproteins that are regulated by S-nitrosylation are still unknown. Here we show that S-nitrosoglutathione reductase (GSNOR), the enzyme that deactivates S-nitrosylation, is hypo-expressed in several human malignancies. Using multiple tumor models, we demonstrate that GSNOR deficiency induces S-nitrosylation of focal adhesion kinase 1 (FAK1) at C658. This event enhances FAK1 autophosphorylation and sustains tumorigenicity by providing cancer cells with the ability to survive in suspension (evade anoikis). In line with these results, GSNOR-deficient tumor models are highly susceptible to treatment with FAK1 inhibitors. Altogether, our findings advance our understanding of the oncogenic role of S-nitrosylation, define GSNOR as a tumor suppressor, and point to GSNOR hypo-expression as a therapeutically exploitable vulnerability in cancer.

Long-term exposure to nitrogen dioxide air pollution and breast cancer risk: A nested case-control within the French E3N cohort study

Nitrogen dioxide (NO₂) is an important air pollutant due to its adverse effects on human health. Yet, current evidence on the association between NO₂ and the risk of breast cancer lacks consistency. In this study, we investigated the association between long-term exposure to NO₂ and breast cancer risk in the French E3N cohort study. Association of breast cancer risk with NO₂ exposure was assessed in a nested case-control study within the French E3N cohort including 5222 breast cancer cases identified over the 1990-2011 follow-up period and 5222 matched controls. Annual mean concentrations of NO₂ at participants' residential addresses for each year from recruitment 1990 through 2011, were estimated using a land use regression (LUR) model. Multivariable conditional logistic regression models were used to compute odds ratios (ORs) and their 95% confidence intervals (CIs). Additional analyses were performed using NO₂ concentrations estimated by CHIMERE, a chemistry transport model. Overall, the mean NO₂ exposure was associated with an increased risk of breast cancer. In all women, for each interquartile range (IQR) increase in NO₂ levels (LUR: 17.8 μg/m³), the OR of the model adjusted for confounders was 1.09 (95% CI: 1.01-1.18). The corresponding OR in the fully adjusted model (additionally adjusted for established breast cancer risk factors) was 1.07 (95% CI: 0.98-1.15). By menopausal status, results for postmenopausal women were comparable to those for all women, while no association was observed among premenopausal women. By hormone receptor status, the OR of estrogen receptor positive breast cancer = 1.07 (95% CI: 0.97-1.19) in the fully adjusted model. Additional analyses using the CHIMERE model showed slight differences in ORs estimates. The results of this study indicate an increased risk of breast cancer associated with long-term exposure to NO₂ air pollution. Observing comparable effects of NO₂ exposure estimated by two different models, reinforces these findings.

Nitric Oxide and Tumors: From Small-Molecule Donor to Combination Therapy

As an important endogenous signaling molecule, nitric oxide (NO) is involved in various physiological and pathological activities in living organisms. It is proved that NO plays a critical role in tumor therapy, while the extremely short half-life and nonspecific distribution of NO greatly limit its further clinical applications. Thus, the past few decades have witnessed the progress made in conquering these shortcomings, including developing innovative NO donors, especially smart and multimodal nanoplatforms. These platforms can precisely control the spatiotemporal distribution of therapeutic agents in the organism, which make big differences in tumor treatment. Here current NO therapeutic mechanisms for cancer, NO donors from small molecules to smart-responsive nanodrug delivery platforms, and NO-based combination therapy are comprehensively reviewed, emphasizing outstanding breakthroughs in these fields and hoping to bring new insights into NO-based tumor treatments.

Glutamine-dependent effects of nitric oxide on cancer cells subjected to hypoxia-reoxygenation

Limited O₂ availability can decrease essential processes in energy metabolism. However, cancers have developed distinct metabolic adaptations to these conditions. For example, glutaminolysis can maintain energy metabolism and hypoxia signaling. Additionally, it has been observed that nitric oxide (NO) possesses concentration-dependent, biphasic effects in cancer. NO has potent anti-tumor effects through modulating events such as angiogenesis and metastasis at low physiological concentrations and inducing cell death at higher concentrations. In this study, Ewing Sarcoma cells (A-673), MIA PaCa, and SKBR3 cells were treated with DetaNONOate (DetaNO) in a model of hypoxia (1% O₂) and reoxygenation (21% O₂). All 3 cell types showed NO-dependent inhibition of cellular O₂ consumption which was enhanced as O₂-tension decreased. L-Gln depletion suppressed the mitochondrial response to decreasing O₂ tension in all 3 cell types and resulted in inhibition of Complex I activity. In A-673 cells the O₂ tension dependent change in mitochondrial O₂ consumption and increase in glycolysis was dependent on the presence of L-Gln. The response to hypoxia and Complex I activity were restored by α-ketoglutarate. NO exposure resulted in the A-673 cells showing greater sensitivity to decreasing O₂ tension. Under conditions of L-Gln depletion, NO restored HIF-1α levels and the mitochondrial response to O₂ tension possibly through the increase of 2-hydroxyglutarate. NO also resulted in suppression of cellular bioenergetics and further inhibition of Complex I which was not rescued by α-ketoglutarate. Taken together these data suggest that NO modulates the mitochondrial response to O₂ differentially in the absence and presence of L-Gln. These data suggest a combination of metabolic strategies targeting glutaminolysis and Complex I in cancer cells.

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 Role of Heme Peroxo Oxidants in the Rational Mechanistic Modeling of Nitric Oxide Synthase: Characterization of Key Intermediates and Elucidation of the Mechanism

Mammalian nitric oxide synthase (NOS) mediates the two-step O2 -dependent oxidative degradation of arginine, and has been linked to a medley of disease situations in humans. Nonetheless, its exact mechanism of action still remains unclear. This work presents the first NOS model system where biologically proposed heme superoxo and peroxo intermediates are assessed as active oxidants against oxime substrates. Markedly, heme peroxo intermediates engaged in a bioinspired oxime oxidation reaction pathway, converting oximes to ketones and nitroxyl anions (NO- ). Detailed thermodynamic, kinetic, and mechanistic interrogations all evince a rate-limiting step primarily driven by the nucleophilicity of the heme peroxo moiety. Coherent with other findings, 18 O and 15 N isotope substitution experiments herein suffice compelling evidence toward a detailed mechanism, which draw close parallels to one of the enzymatic proposals. Intriguingly, recent enzymatic studies also lend credence to these findings, and several relevant reaction intermediates have been observed during NOS turnover.

Oxidized Proteins Differentially Affect Maturation and Activation of Human Monocyte-Derived Cells

In cancer, antigen-presenting cells (APC), including dendritic cells (DCs), take up and process proteins to mount adaptive antitumor immune responses. This often happens in the context of inflamed cancer, where reactive oxygen species (ROS) are ubiquitous to modify proteins. However, the inflammatory consequences of oxidized protein uptake in DCs are understudied. To this end, we investigated human monocyte-derived cell surface marker expression and cytokine release profiles when exposed to oxidized and native proteins. Seventeen proteins were analyzed, including viral proteins (e.g., CMV and HBV), inflammation-related proteins (e.g., HO1 and HMGB1), matrix proteins (e.g., Vim and Coll), and vastly in the laboratory used proteins (e.g., BSA and Ova). The multifaceted nature of inflammation-associated ROS was mimicked using gas plasma technology, generating reactive species cocktails for protein oxidation. Fourteen oxidized proteins led to elevated surface marker expression levels of CD25, CD40, CD80, CD86, and MHC-II as well as strongly modified release of IL6, IL8, IL10, IL12, IL23, MCP-1, and TNFα compared to their native counterparts. Especially IL8, heme oxygenase 2, and vimentin oxidation gave pronounced effects. Furthermore, protein kinase phospho-array studies in monocyte-derived cells pulsed with native vs. oxidized IL8 and insulin showed enhanced AKT and RSK2 phosphorylation. In summary, our data provide for the first time an overview of the functional consequences of oxidized protein uptake by human monocyte-derived cells and could therefore be a starting point for exploiting such principle in anticancer therapy in the future.

Role of nitric oxide in hyper-aggressiveness of tumor cells that survive various anti-cancer therapies

Low level nitric oxide (NO) produced by inducible NO synthase (iNOS) in many malignant tumors is known to play a key role in the survival and proliferation of tumor cells. NO can also induce or augment resistance to anti-tumor treatments such as platinum-based chemotherapy (CT), ionizing radiotherapy (RT), and non-ionizing photodynamic therapy (PDT). In each of these treatments, tumor cells that survive the challenge may exhibit a striking increase in NO-dependent proliferative, migratory, and invasive aggressiveness compared with non-challenged controls. Moreover, NO from cells directly targeted by PDT can often stimulate aggressiveness in non- or poorly targeted bystander cells. Although NO-mediated resistance to many of these therapies is fairly-well recognized by now, the hyper-aggressiveness of surviving cells and bystander counterparts is not. We will focus on these negative aspects in this review, citing examples from the PDT, CT, and RT publications. Increased aggressiveness of cells that escape therapeutic elimination is a concern because it could enhance tumor progression and metastatic dissemination. Pharmacologic approaches for suppressing these negative responses will also be discussed, e.g., administering inhibitors of iNOS activity or iNOS expression as therapeutic adjuvants.

Inflammation-targeted nanomedicine against brain cancer: From design strategies to future developments

Brain cancer is an aggressive type of cancer with poor prognosis. While the immune system protects against cancer in the early stages, the tumor exploits the healing arm of inflammatory reactions to accelerate its growth and spread. Various immune cells penetrate the developing tumor region, establishing a pro-inflammatory tumor milieu. Additionally, tumor cells may release chemokines and cytokines to attract immune cells and promote cancer growth. Inflammation and its associated mechanisms in the progression of cancer have been extensively studied in the majority of solid tumors, especially brain tumors. However, treatment of the malignant brain cancer is hindered by several obstacles, such as the blood-brain barrier, transportation inside the brain interstitium, inflammatory mediators that promote tumor growth and invasiveness, complications in administering therapies to tumor cells specifically, the highly invasive nature of gliomas, and the resistance to drugs. To resolve these obstacles, nanomedicine could be a potential strategy that has facilitated advancements in diagnosing and treating brain cancer. Due to the numerous benefits provided by their small size and other features, nanoparticles have been a prominent focus of research in the drug-delivery field. The purpose of this article is to discuss the role of inflammatory mediators and signaling pathways in brain cancer as well as the recent advances in understanding the nano-carrier approaches for enhancing drug delivery to the brain in the treatment of brain cancer.

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.

Looking at denitrosylation to understand the myogenesis gone awry theory of rhabdomyosarcoma

S-nitrosylation of proteins is a nitric oxide (NO)-based post-translational modification of cysteine residues. By removing the NO moiety from S-nitrosothiol adducts, denitrosylases restore sulfhydryl protein pool and act as downstream tuners of S-nitrosylation signaling. Alterations in the S-nitrosylation/denitrosylation dynamics are implicated in many pathological states, including cancer ontogenesis and progression, skeletal muscle myogenesis and function. Here, we aim to provide and link different lines of evidence, and elaborate on the possible role of S-nitrosylation/denitrosylation signaling in rhabdomyosarcoma, one of the most common pediatric mesenchymal malignancy.

Pharmacokinetic Characterization of the DDAH1 Inhibitors ZST316 and ZST152 in Mice Using a HPLC-MS/MS Method

The pharmacokinetic profile of ZST316 and ZST152, arginine analogues with inhibitory activity towards human dimethylarginine dimethylaminohydrolase-1 (DDAH1), was investigated in mice using a newly developed HPLC-MS/MS method. The method proved to be reproducible, precise, and accurate for the measurement of the compounds in plasma and urine. Four-week-old female FVB mice received a single dose of ZST316 and ZST152 by intravenous bolus (30 mg/Kg) and oral gavage (60 mg/Kg). ZST316 Cmax was 67.4 µg/mL (intravenous) and 1.02 µg/mL (oral), with a half-life of 6 h and bioavailability of 4.7%. ZST152 Cmax was 24.9 µg/mL (intravenous) and 1.65 µg/mL (oral), with a half-life of 1.2 h and bioavailability of 33.3%. Urinary excretion of ZST152 and ZST316 was 12.5%–22.2% and 2.3%–7.5%, respectively. At least eight urinary metabolites were identified. After chronic intraperitoneal treatment with the more potent DDAH1 inhibitor, ZST316 (30 mg/Kg/day for three weeks), the bioavailability was 59% and no accumulation was observed. Treatment was well tolerated with no changes in body weight vs. untreated animals and no clinical signs of toxicity or distress. The results of this study show that ZST316 has a favorable pharmacokinetic profile, following intraperitoneal administration, to investigate the effects of DDAH1 inhibition in mice.

The biological activity of Ocimum minimum L. flowers on redox status parameters in HCT-116 colorectal carcinoma cells

Medicinal plants have widely been used as a natural source of remedies for treating several diseases, including colorectal cancer. Ocimum minimum L. is a very important dietary plant used in traditional and modern medicine, due to its health beneficial effect realized by cytotoxic, proapoptotic, antioxidant/prooxidant, antiviral and antimicrobial activity. The biological activity of O. minimum flowers has been evaluated in HCT116 colorectal carcinoma cells through antiproliferative activity by MTT assay, pro-apoptotic activity by AO/EB and concentrations of redox status parameters (O2∙ and lipid peroxidation) by colorimetric methods. The protein expression of iNOS was analyzed by immunocytochemistry, while the antimigratory effect was measured by xCELLigence system. The treatment with O. minimum shows the antiproliferative, proapoptotic, impact on redox status parameters and antimigratory effect on HCT-116 cells. Based on obtained results, the pharmacological effect of O. minimum is evident against HCT-116 colorectal carcinoma cells, suggesting that this plant may be good start material for future anticancer therapy investigation.

Tissue levels of oxidative stress markers and antioxidants in colorectal cancer patients

The role of reactive oxygen species in the development of cancer has become well recognized in recent years; however, evidence for a link between oxidative stress and cancer risk has not been fully explored. One of the major cancers whose number of cases has increased significantly in recent years is colon and rectal cancer, which has the second highest mortality rate in Libya. Forty subjects were divided into three groups (20 tumors from colorectal cancer patients, adjacent surrounding tumor tissues, and 20 adjacent normal tissues). Evaluation of oxidative stress indices in the samples was performed by analyzing enzymatic and non-enzymatic parameters including the activity of glutathione peroxidase and catalase as antioxidant enzymes, reduced glutathione as an antioxidant, malondialdehyde MDA levels as an oxidative damage product, nitritc oxide content NO as an inflammatory marker, and total thiols as a measure of redox status. MDA and NO levels were significantly higher in tumor tissues than in adjacent healthy tissue. Also, the surrounding tumor tissue exhibited higher MDA and NO levels compared with control tissues. The oxidant and antioxidant levels in the tumor was significantly lower than those in the surrounding tumor tissue and control healthy tissue. The results suggest that oxidant and antioxidant parameters can be used as indicators of an imbalance in humans, and as this imbalance increases, the human body may be vulnerable to developing cancer.

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.

New azolyl-derivatives as multitargeting agents against breast cancer and fungal infections: synthesis, biological evaluation and docking study

Nonsteroidal aromatase inhibitors (NSAIs) are well-established drugs for the therapy of breast cancer. However, they display some serious side effects, and their efficacy can be compromised by the development of chemoresistance. Previously, we have reported different indazole-based carbamates and piperidine-sulphonamides as potent aromatase inhibitors. Starting from the most promising compounds, here we have synthesised new indazole and triazole derivatives and evaluated their biological activity as potential dual agents, targeting both the aromatase and the inducible nitric oxide synthase, being this last dysregulated in breast cancer. Furthermore, selected compounds were evaluated as antiproliferative and cytotoxic agents in the MCF-7 cell line. Moreover, considering the therapeutic diversity of azole-based compounds, all the synthesized compounds were also evaluated as antifungals on different Candida strains. A docking study, as well as molecular dynamics simulation, were carried out to shed light on the binding mode of the most interesting compound into the different target enzymes catalytic sites.

Protein Phosphorylation in Cancer: Role of Nitric Oxide Signaling Pathway

Nitric oxide (NO), a free radical, plays a critical role in a wide range of physiological and pathological processes. Due to its pleiotropic function, it has been widely investigated in various types of cancers and is strongly associated with cancer development. Mounting pieces of evidence show that NO regulates various cancer-related events, which mainly depends on phosphorylating the key proteins in several signaling pathways. However, phosphorylation of proteins modulated by NO signaling pathway may lead to different effects in different types of cancer, which is complex and remains unclear. Therefore, in this review, we focus on the effect of protein phosphorylation modulated by NO signaling pathway in different types of cancers including breast cancer, lung cancer, prostate cancer, colon cancer, gastric cancer, pancreatic cancer, ovarian cancer, and neuroblastoma. Phosphorylation of key proteins, including p38 MAPK, ERK, PI3K, STAT3, and p53, modified by NO in various signaling pathways affects different cancer-related processes including cell apoptosis, proliferation, angiogenesis, metastasis, and several cancer therapies. Our review links the NO signaling pathway to protein phosphorylation in cancer development and provides new insight into potential targets and cancer therapy.

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.

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.

Exploiting S-nitrosylation for cancer therapy: facts and perspectives

S-nitrosylation, the post-translational modification of cysteines by nitric oxide, has been implicated in several cellular processes and tissue homeostasis. As a result, alterations in the mechanisms controlling the levels of S-nitrosylated proteins have been found in pathological states. In the last few years, a role in cancer has been proposed, supported by the evidence that various oncoproteins undergo gain- or loss-of-function modifications upon S-nitrosylation. Here, we aim at providing insight into the current knowledge about the role of S-nitrosylation in different aspects of cancer biology and report the main anticancer strategies based on: (i) reducing S-nitrosylation-mediated oncogenic effects, (ii) boosting S-nitrosylation to stimulate cell death, (iii) exploiting S-nitrosylation through synthetic lethality.

Network Pharmacology-Based Approach to Investigate the Molecular Targets of Sinomenine for Treating Breast Cancer

Purpose

Sinomenine has been known to inhibit the proliferation of breast cancer cells. However, its targets have not been found yet. This study aimed to search for molecular targets of sinomenine for treating breast cancer via network pharmacology.

Methods

Potential targets of sinomenine or breast cancer were separately screened from indicated databases. The common targets of both sinomenine and breast cancer were considered as the targets of sinomenine for treating breast cancer. A sinomenine-target-pathway network was constructed based on the obtained results from Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The putative targets of sinomenine were further determined by using protein–protein interaction (PPI) analysis and molecular docking. Finally, the putative targets were verified in vitro and in vivo.

Results

Twenty predicted targets were identified through network pharmacological analysis. Gene Ontology (GO) and KEGG pathway enrichment indicated that these predicted targets enriched in the process of MAP kinase activity, VEGF signaling pathway, Relaxin signaling pathway, Growth hormone synthesis, secretion and action. MAPK1, NOS3, NR3C1, NOS1 and NOS2 were further identified as the putative targets by using PPI and molecular docking analysis. Expression of MAPK1, NR3C1, NOS1, NOS2 and NOS3 genes were significantly regulated by sinomenine in both MCF-7 cells and MDA-MB-231 cells. Furthermore, the expression of NR3C1 in human breast cancer specimens was lower than that in para-tumor normal tissues. Meanwhile, the expression of NR3C1 in xenograft tumors was up-regulated after sinomenine treatment.

Conclusion

MAPK1, NR3C1, NOS1, NOS2 and NOS3 were identified as the putative targets of sinomenine for treating breast cancer. NR3C1 was preliminarily confirmed as a target of sinomenine in two breast cancer cell lines, xenograft tumor models and human breast cancer specimens. These data indicated that the network pharmacology-based prediction of sinomenine targets for treating breast cancer could be reliable.

Current Advances of Nitric Oxide in Cancer and Anticancer Therapeutics

Nitric oxide (NO) is a short-lived, ubiquitous signaling molecule that affects numerous critical functions in the body. There are markedly conflicting findings in the literature regarding the bimodal effects of NO in carcinogenesis and tumor progression, which has important consequences for treatment. Several preclinical and clinical studies have suggested that both pro- and antitumorigenic effects of NO depend on multiple aspects, including, but not limited to, tissue of generation, the level of production, the oxidative/reductive (redox) environment in which this radical is generated, the presence or absence of NO transduction elements, and the tumor microenvironment. Generally, there are four major categories of NO-based anticancer therapies: NO donors, phosphodiesterase inhibitors (PDE-i), soluble guanylyl cyclase (sGC) activators, and immunomodulators. Of these, NO donors are well studied, well characterized, and also the most promising. In this study, we review the current knowledge in this area, with an emphasis placed on the role of NO as an anticancer therapy and dysregulated molecular interactions during the evolution of cancer, highlighting the strategies that may aid in the targeting of cancer.

The regulation of nitric oxide in tumor progression and therapy

Nitric oxide (NO) is a ubiquitous gas with free radical groups that is soluble in water, and which is involved in numerous physiological functions including inflammatory and immune responses. However, the role of NO in tumor biology is controversial and misunderstood. NO has been shown to have both anti-cancer and carcinogenic effects, which are dependent on the time, location, and concentration of NO. This duality presents a double challenge to determine the net impact of NO on cancer and to define the therapeutic role of NO-centered anti-cancer strategies. Nevertheless, it is believed that a comprehensive and dynamic understanding of the cascade of molecular and cellular events underlying tumor biology that are affected by NO will allow researchers to exploit the potential anti-tumor properties of drugs that interfere with NO metabolism.

The Role of Nitric Oxide in Cancer: Master Regulator or NOt?

Nitric oxide (NO) is a key player in both the development and suppression of tumourigenesis depending on the source and concentration of NO. In this review, we discuss the mechanisms by which NO induces DNA damage, influences the DNA damage repair response, and subsequently modulates cell cycle arrest. In some circumstances, NO induces cell cycle arrest and apoptosis protecting against tumourigenesis. NO in other scenarios can cause a delay in cell cycle progression, allowing for aberrant DNA repair that promotes the accumulation of mutations and tumour heterogeneity. Within the tumour microenvironment, low to moderate levels of NO derived from tumour and endothelial cells can activate angiogenesis and epithelial-to-mesenchymal transition, promoting an aggressive phenotype. In contrast, high levels of NO derived from inducible nitric oxide synthase (iNOS) expressing M1 and Th1 polarised macrophages and lymphocytes may exert an anti-tumour effect protecting against cancer. It is important to note that the existing evidence on immunomodulation is mainly based on murine iNOS studies which produce higher fluxes of NO than human iNOS. Finally, we discuss different strategies to target NO related pathways therapeutically. Collectively, we present a picture of NO as a master regulator of cancer development and progression.

Role of platelets and breast cancer stem cells in metastasis

The high mortality rate of breast cancer is mainly caused by the metastatic ability of cancer cells, resistance to chemotherapy and radiotherapy, and tumor regression capacity. In recent years, it has been shown that the presence of breast cancer stem cells is closely associated with the migration and metastatic ability of cancer cells, as well as with their resistance to chemotherapy and radiotherapy. The tumor microenvironment is one of the main molecular factors involved in cancer and metastatic processes development, in this sense it is interesting to study the role of platelets, one of the main communicator cells in the human body which are activated by the signals they receive from the microenvironment and can generate more than one response. Platelets can ingest and release RNA, proteins, cytokines and growth factors. After the platelets interact with the tumor microenvironment, they are called "tumor-educated platelets." Tumor-educated platelets transport material from the tumor microenvironment to sites adjacent to the tumor, thus helping to create microenvironments conducive for the development of primary and metastatic tumors. It has been observed that the clone capable of carrying out the metastatic process is a cancer cell with stem cell characteristics. Cancer stem cells go through a series of processes, including epithelial-mesenchymal transition, intravasation into blood vessels, movement through blood vessels, extravasation at the site of the establishment of a metastatic focus, and site colonization. Tumor-educated platelets support all these processes. 

The Relationship Between Protein S-Nitrosylation and Human Diseases: A Review

S-nitrosylation (SNO) is a covalent post-translational oxidative modification. The reaction is the nitroso group (-NO) to a reactive cysteine thiol within a protein to form the SNO. In recent years, a variety of proteins in human body have been found to undergo thiol nitrosylation under specific conditions. Protein SNO, which is closely related to cardiovascular disease, Parkinson's syndrome, Alzheimer's disease and tumors, plays an important role in regulatory mechanism of protein function in both physiological and pathological pathways, such as in cellular homeostasis and metabolism. This review discusses possible molecular mechanisms protein SNO modification, such as the role of NO in vivo and the formation mechanism of SNO, with particular emphasis on mechanisms utilized by SNO to cause certain diseases of human. Importantly, the effect of SNO on diseases is multifaceted and multi-channel, and its critical value in vivo is not well defined. Intracellular redox environment is also a key factor affecting its level. Therefore, we should pay more attention to the equilibrium relationship between SNO and denitrosylation pathway in the future researches. These findings provide theoretical support for the improvement or treatment of diseases from the point of view of SNO.

The progression of metastatic melanoma augments a pro-oxidative milieu locally but not systemically

Malignant melanoma is the most dangerous form of skin cancer. Despite new therapies for melanoma treatment, effective therapy is mainly limited by excessive metastasis. Currently, the factors determining metastasis development are not elucidated, but oxidative stress was suggested to be involved. To this end, we analyzed oxidative stress parameters during the metastatic development using the syngeneic B16F10 melanoma model. An increase in blood plasma lipid peroxidation occurred at the earliest stage of the disease, with a progressive decrease in oxidative damage and an increase in antioxidant defense. Vice versa, increased lipid peroxidation and 3-nitrotyrosine, and decreased antioxidant parameters were observed in the metastatic nodules throughout the disease. This was concomitant with a progressive increase in vascular endothelial growth factor and proliferating cell nuclear antigen. We conclude that the oxidative stress in the bloodstream decreases during the metastatic process and that nitrosative stress increases during the proliferation and growth of metastatic nodules in the tumor microenvironment. These results will help to better understand the role of oxidative stress during melanoma metastasis.

Enhanced in vivo targeting of estrogen receptor alpha signaling in murine mammary adenocarcinoma by nilotinib/rosuvastatin novel combination

The development of resistance to endocrine therapy of estrogen receptor alpha (ERα)-positive breast cancer is inevitable, necessitating the introduction of alternative treatment strategies. Therefore, the current study was carried out to investigate the in vivo efficacy and tolerability of nilotinib/rosuvastatin novel combination against ERα-positive breast carcinoma. Results showed that treatment of tumor-bearing mice with nilotinib/rosuvastatin exerted a significant antitumor activity. Mechanistically, the combination treatment efficiently inhibited the in vivo ERα protein expression, whereas ERα mRNA levels were unaffected suggesting a posttranslational regulation. In addition, the combination treatment markedly downregulated the expression of two ERα downstream target genes: C3 and pS2 confirming the inhibition of ERα signaling in vivo. Further, nilotinib/rosuvastatin combination strongly induced apoptosis evidenced by a marked caspase-3 cleavage and downregulation of tumor nitric oxide levels. Moreover, histopathology showed significant declines in mitotic figures and tumor giant cells implying the in vivo capability of the combination treatment to interfere with cancer cell proliferation and persistence. Of note, the combination treatment abrogated nilotinib-induced hypercholesterolemia and did not adversely affect the liver function or body weight. Overall, the present study provided evidences that warrant further assessment of nilotinib/rosuvastatin combination as an alternative therapeutic modality for ERα-positive breast cancer.

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.

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.

Molecular Mechanisms of the Efficacy of Cold Atmospheric Pressure Plasma (CAP) in Cancer Treatment

Recently, the potential use of cold atmospheric pressure plasma (CAP) in cancer treatment has gained increasing interest. Especially the enhanced selective killing of tumor cells compared to normal cells has prompted researchers to elucidate the molecular mechanisms for the efficacy of CAP in cancer treatment. This review summarizes the current understanding of how CAP triggers intracellular pathways that induce growth inhibition or cell death. We discuss what factors may contribute to the potential selectivity of CAP towards cancer cells compared to their non-malignant counterparts. Furthermore, the potential of CAP to trigger an immune response is briefly discussed. Finally, this overview demonstrates how these concepts bear first fruits in clinical applications applying CAP treatment in head and neck squamous cell cancer as well as actinic keratosis. Although significant progress towards understanding the underlying mechanisms regarding the efficacy of CAP in cancer treatment has been made, much still needs to be done with respect to different treatment conditions and comparison of malignant and non-malignant cells of the same cell type and same donor. Furthermore, clinical pilot studies and the assessment of systemic effects will be of tremendous importance towards bringing this innovative technology into clinical practice.

Small molecule inhibitors and stimulators of inducible nitric oxide synthase in cancer cells from natural origin (phytochemicals, marine compounds, antibiotics)

Nitric oxide synthases (NOS) are a family of isoforms, which generate nitric oxide (NO). NO is one of the smallest molecules in nature and acts mainly as a potent vasodilator. It participates in various biological processes ranging from physiological to pathological conditions. Inducible NOS (iNOS, NOS2) is a calcium-independent and inducible isoform. Despite high iNOS expression in many tumors, the role of iNOS is still unclear and complex with both enhancing and prohibiting actions in tumorigenesis. Nature presents a broad variety of natural stimulators and inhibitors, which may either promote or inhibit iNOS response. In the present review, we give an overview of iNOS-modulating agents with a special focus on both natural and synthetic molecules and their effects in related biological processes. The role of iNOS in physiological and pathological conditions is also discussed.

Genetic and molecular determinants of prostate cancer among Iranian patients: An update

Prostate cancer (PCa) is one of the most common age-related cancers among men. Various environmental and genetic factors are involved in the development and progression of PCa. In most cases, the primary symptoms of disease are not severe. Therefore, it is common for patients to be referred with severe clinical manifestations at advanced stages of disease. Since this malignancy is age related and Iran will face a significant increase in the number of seniors, it is expected that the prevalence of PCa among Iranian men will rise. PCa progression has been observed to be associated with genetic and ethnic factors. It may therefore be clinically useful to determine a panel of genetic markers, in addition to routine diagnostic methods, to detect tumors in the early stages. In the present review, we have summarized the reported genetic markers in PCa Iranian patients to pave the way for the determination of an ethnic specific genetic marker panel for the early detection of PCa. To understand the genetic and molecular biology of PCa among Iranians, we have categorized these genetic markers based on their cellular functions.

The importance of inducible nitric oxide synthase and nitrotyrosine as prognostic markers for oral squamous cell carcinoma

BACKGROUND

The prognosis of human cancer depends on the deregulations of many molecular patterns. In recent years, a great interest in the intracellular signaling mechanisms related to nitric oxide (NO)-induced carcinogenesis has appeared, as one of the most preeminent prognostic markers for many types of neoplasms. In this study, we identify the levels of iNOS and nitrotyrosine in the sample of normal oral mucosa (NOM), oral leukoplakia (OL), and oral squamous cell carcinoma (OSCC).

METHODS

Quantitative polymerase chain reactions (qPCRs) were utilized to detect the NOS2 levels in fresh-frozen tissue samples of NOM (n = 6), OL (n = 20), and OSCC (n = 15). Moreover, the immunohistochemical method was used to examine the levels of iNOS and nitrotyrosine in 85 cases of OSCC (39 cases without metastases and 46 with metastases), 42 cases of OL, and 16 cases of NOM.

RESULTS

There are rising tendencies in the iNOS mRNA and protein levels during human oral carcinogenesis. Similar findings were obtained in the nitrotyrosine staining. Furthermore, iNOS and nitrotyrosine immunostaining are associated with several clinical-pathological features of OSCC (site, presence of metastasis, staging, recidivism, and survival).

CONCLUSIONS

The NO-signaling pathway plays a vital role in the development and progression of human oral dysplastic and neoplastic diseases. Nitrotyrosine was a significant marker for the discrimination of OSCC prognosis and survival.

Inhibition of breast tumor growth by N(G)-nitro-l-arginine methyl ester (l-NAME) is accompanied by activation of fibroblasts

Nitric Oxide (NO) is involved in many physiological and pathological processes. It is generated by a family of NO synthases (NOS), being the inducible isoform, iNOS, responsible for higher amounts of NO. Here, we report that pharmacological inhibition of NO production by l-NAME reduces both viability and MAPK activated signalling pathways in iNOS positive human and murine cancer cell lines. In vivo, using syngeneic models, in parallel with tumor reduction induced by l-NAME, collagen deposition and α-SMA positive stromal cells are observed. This observation takes place only when tumor cells express iNOS. In vitro, l-NAME induces viability and differentiation on fibroblast. Our results reveal that NO inhibition contributes to stimulate proliferation and activation of fibroblasts in parallel with tumor reduction of iNOS positive breast cancer.

Effects of Some Lamiaceae Species on NO Production and Cell Injury in Hydrogen Peroxide-induced Stress

Nitric oxide (NO) is a key mediator that plays an important role in pathogenesis of various chronic diseases like Alzheimer’s disease and Parkinson’s disease. Additionally, there is a great attitude for finding natural compounds, which could control and inhibit NO production in pathological conditions. Therefore, we were encouraged to investigate the effects of some Lamiaceae species on NO production and cell injury during oxidative stress in PC12 cells. In this study, cell death determined by MTT assay and NO levels were evaluated using Griess assay. PC12 cells were exposed to total metanolic extracts of three Scutellaria and one Nepeta species. The results revealed that Nepeta laxiflora (N. laxiflora) could protect PC12 cells from hydrogen proxide-induced oxidative stress and all of the plants inhibited NO production in that condition except Scutellaria tournefortii (Sc. tournefortii). In addition, Scutellaria multicaulis (Sc. multicaulis) was meanwhile subjected to fractionation using different organic solvents. The dichloromethan and ethyl acetate fractions of Sc. multicaulis could protect PC12 cells from oxidative stress injury. However, NO production was restrained by the hexane and dichloromethane fractions. Considering the results, N. laxiflora, Scutellaria nepetifolia (Sc. nepetifolia), and Sc. multicaulis are good candidates for further investigations in neuroprotection and anti-inflammation studies.

Nitric oxide and its derivatives in the cancer battlefield

Elevated levels of reactive nitrogen species, alteration in redox balance and deregulated redox signaling are common hallmarks of cancer progression and chemoresistance. However, depending on the cellular context, distinct reactive nitrogen species are also hypothesized to mediate cytotoxic activity and are thus used in anticancer therapies. We present here the dual face of nitric oxide and its derivatives in cancer biology. Main derivatives of nitric oxide, such as nitrogen dioxide and peroxynitrite cause cell death by inducing protein and lipid peroxidation and/or DNA damage. Moreover, they control the activity of important protein players within the pro- and anti-apoptotic signaling pathways. Thus, the control of intracellular reactive nitrogen species may become a sophisticated tool in anticancer strategies.

Nitric Oxide-Mediated Enhancement and Reversal of Resistance of Anticancer Therapies

In the last decade, immune therapies against human cancers have emerged as a very effective therapeutic strategy in the treatment of various cancers, some of which are resistant to current therapies. Although the clinical responses achieved with many therapeutic strategies were significant in a subset of patients, another subset remained unresponsive initially, or became resistant to further therapies. Hence, there is a need to develop novel approaches to treat those unresponsive patients. Several investigations have been reported to explain the underlying mechanisms of immune resistance, including the anti-proliferative and anti-apoptotic pathways and, in addition, the increased expression of the transcription factor Yin-Yang 1 (YY1) and the programmed death ligand 1 (PD-L1). We have reported that YY1 leads to immune resistance through increasing HIF-1α accumulation and PD-L1 expression. These mechanisms inhibit the ability of the cytotoxic T-lymphocytes to mediate their cytotoxic functions via the inhibitory signal delivered by the PD-L1 on tumor cells to the PD-1 receptor on cytotoxic T-cells. Thus, means to override these resistance mechanisms are needed to sensitize the tumor cells to both cell killing and inhibition of tumor progression. Treatment with nitric oxide (NO) donors has been shown to sensitize many types of tumors to chemotherapy, immunotherapy, and radiotherapy. Treatment of cancer cell lines with NO donors has resulted in the inhibition of cancer cell activities via, in part, the inhibition of YY1 and PD-L1. The NO-mediated inhibition of YY1 was the result of both the inhibition of the upstream NF-κB pathway as well as the S-nitrosylation of YY1, leading to both the downregulation of YY1 expression as well as the inhibition of YY1-DNA binding activity, respectively. Also, treatment with NO donors induced the inhibition of YY1 and resulted in the inhibition of PD-L1 expression. Based on the above findings, we propose that treatment of tumor cells with the combination of NO donors, at optimal noncytotoxic doses, and anti-tumor cytotoxic effector cells or other conventional therapies will result in a synergistic anticancer activity and tumor regression.

Mechanisms for Radioprotection by Melatonin; Can it be Used as a Radiation Countermeasure?

BACKGROUND

Melatonin is a natural body product that has shown potent antioxidant property against various toxic agents. For more than two decades, the abilities of melatonin as a potent radioprotector against toxic effects of ionizing radiation (IR) have been proved. However, in the recent years, several studies have been conducted to illustrate how melatonin protects normal cells against IR. Studies proposed that melatonin is able to directly neutralize free radicals produced by IR, leading to the production of some low toxic products.

DISCUSSION

Moreover, melatonin affects several signaling pathways, such as inflammatory responses, antioxidant defense, DNA repair response enzymes, pro-oxidant enzymes etc. Animal studies have confirmed that melatonin is able to alleviate radiation-induced cell death via inhibiting pro-apoptosis and upregulation of anti-apoptosis genes. These properties are very interesting for clinical radiotherapy applications, as well as mitigation of radiation injury in a possible radiation disaster. An interesting property of melatonin is mitochondrial ROS targeting that has been proposed as a strategy for mitigating effects in radiosensitive organs, such as bone marrow, gastrointestinal system and lungs. However, there is a need to prove the mitigatory effects of melatonin in experimental studies.

CONCLUSION

In this review, we aim to clarify the molecular mechanisms of radioprotective effects of melatonin, as well as possible applications as a radiation countermeasure in accidental exposure or nuclear/radiological disasters.

Reactive nitrogen species in host-bacterial interactions

Reactive nitrogen species play diverse and essential roles in host-pathogen interactions. Here, we review selected recent discoveries regarding nitric oxide (NO) in host defense and the pathogenesis of infection, mechanisms of bacterial NO resistance, production of NO by human macrophages, NO-based antimicrobial therapeutics and NO interactions with the gut microbiota.

The Phosphodiesterase-5 Inhibitors and Prostate Cancer – What We Rely Know About It?

Phosphodiesterase-5 inhibitors (PDE5Is) represent a group of drugs that are registered for the treatment of erectile dysfunctions predominantly, but recently also for treatment of pulmonary hypertension and benign prostatic hypertrophy. However, more and more research deals with possible antitumor potential of PDE5Is in different types of cancers, including prostate cancer. Prostate cancer represents the one of the most common carcinoma in the male population, whose incidence is continuously increasing. Early detection combined with radical prostatectomy increases the survival rate, but also it is necessary to keep in mind the quality of life of patients undergoing prostatectomy in light of bladder control and erectile function. Authors of various clinical studies presented the results that often lead to totally opposing conclusions. For example, Chavez and colleagues have shown that use of PDE5Is in men with erectile dysfunction decreases the risk of developing prostate cancer, while, on the other hand, Michl and colleagues pointed out the adversely effect of PDE5Is on biochemical recurrence after bilateral nerve sparing radical prostatectomy. In that sense, the aim of this review was to present as many as possible of existing results dealing with of action of PDE5Is in the field of prostatic carcinoma. Taking into account all presented data, it can be concluded that eff ect of PDE5Is on formation, development and outcome of treatment in patients with prostate carcinoma is very intriguing question, whose response requires additional both experimental and clinical research.

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.