Increased in situ expression of nitric oxide synthase in human colorectal cancer

CS-NO suppresses inhibits glycolysis and gastric cancer progression through regulating YAP/TAZ signaling pathway

CONTEXT

Gastric cancer (GC) is a significant contributor to global mortality and is recognized for its elevated prevalence and fatality rates. Nitric Oxide (NO) plays a role in multiple aspects of cancer metastasis and progression. CS-NO is a polysaccharide-based biomaterial with NO-releasing properties that shows promising therapeutic potential. Nonetheless, the action mechanism of CS-NO in GC is still largely unclear.

METHODS

The present study employed various experimental techniques, including CCK-8 assay, colony formation assay, EdU staining, and transwell assays, to evaluate the proliferation, migration, and invasion of GC cells. Additionally, ELISA was utilized to measure glucose uptake, lactate production, and cellular ATP levels in GC cells. In vivo investigations on nude mice were conducted to validate the in vitro results.

OBJECTIVE

The present study aimed to examine the potential anti-tumor properties of CS-NO on GC through in vitro and in vivo investigations, while also exploring the underlying mechanisms involved.

RESULTS

Our data suggested that CS-NO might prevent GC cell invasion and migration. Decreased expressions of GLUT1, HK2, and LDHA further demonstrated that CS-NO significantly suppressed aerobic glycolysis in GC cells. The administration of CS-NO resulted in a significant reduction of YAP and TAZ levels in GC cells. Our data further show that CS-NO treatment could inhibit GC cancer growth in mice, consistent with the significant decrease in Ki67, GLUT1 and YAP expression levels.

DISCUSSION AND CONCLUSION

These findings could reveal the good effects of CS-NO therapy on inhibiting GC.

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.

GPR87 Promotes Metastasis through the AKT-eNOS-NO Axis in Lung Adenocarcinoma

Lung adenocarcinoma is one of the leading causes of cancer-related deaths. Despite the availability of advanced anticancer drugs for lung cancer treatment, the prognosis of patients still remains poor. There is a need to explore novel oncogenic mechanisms to overcome these therapeutic limitations. The functional experiments in vitro and in vivo were performed to evaluate the role of GPR87 expression on lung adenocarcinoma metastasis. The public lung adenocarcinoma dataset was used to determine the clinical relevance of GPR87 expression in patients with lung adenocarcinoma. GPR87 is upregulated in various cancer; however, the biological function of GPR87 has not yet been established in lung adenocarcinoma. In this study, we found that GPR87 expression is upregulated in lung adenocarcinoma and is associated with poor patient prognosis. Additionally, we showed that GPR87 overexpression promotes invasiveness and metastasis of lung adenocarcinoma cells. Furthermore, we demonstrated that AKT-eNOS-NO signaling is a novel downstream pathway of GPR87 in lung adenocarcinoma. Conversely, we confirmed that silencing of GPR87 expression suppressed these phenotypes. Our results reveal the oncogenic function of GPR87 in cancer progression and metastasis through the activation of eNOS as a key mediator. Therefore, we propose that targeting eNOS could be a novel therapeutic strategy to improve the clinical treatment of lung adenocarcinoma.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

K. H, Basavaraju P, Pasumarthi D, S. D. A, Soujanya P, Arnold Emeson I, Bodiga V, Pawar SC. Inhibition of Inducible Nitric Oxide Synthase (iNOS) by Andrographolide and In Vitro Evaluation of Its Antiproliferative and Proapoptotic Effects on Cervical Cancer

This work is aimed at investigating the expression levels of inducible nitric oxide synthase (iNOS) in cervical cancer and identifying a potential iNOS inhibitor. The data mining studies performed advocated iNOS to be a promising biomarker for cancer prognosis, as it is highly overexpressed in several malignant cancers. The elevated iNOS was found to be associated with poor survival and increased tumor aggressiveness in cervical cancer. Immunohistochemical and RT-PCR investigations of iNOS showed significant upregulation of endogenous iNOS expression in the cervical tumor samples, thus making iNOS a potent target for decreasing tumor inflammation and aggressiveness. Andrographolide, a plant-derived diterpenoid lactone, is widely reported to be effective against infections and inflammation, causing no adverse side effects on humans. In the current study, we investigated the effect of andrographolide on the prognostic value of iNOS expression in cervical cancer, which has not been reported previously. The binding efficacy of andrographolide was analyzed by performing molecular docking and molecular dynamic simulations. Multiple parameters were used to analyze the simulation trajectory, like root mean square deviation (RMSD), torsional degree of freedom, protein-root mean square fluctuations (P-RMSF), ligand RMSF, total number of intramolecular hydrogen bonds, secondary structure elements (SSE) of the protein, and protein complex with the time-dependent functions of MDS. Ligand-protein interactions revealed binding efficacy of andrographolide with tryptophan amino acid of iNOS protein. Cancer cell proliferation, cell migration, cell cycle analysis, and apoptosis-mediated cell death were assessed in vitro, post iNOS inhibition induced by andrographolide treatment (demonstrated by Western blot). Results. Andrographolide exhibited cytotoxicity by inhibiting the in vitro proliferation of cervical cancer cells and also abrogated the cancer cell migration. A significant increase in apoptosis was observed with increasing andrographolide concentration, and it also induced cell cycle arrest at G1-S phase transition. Our results substantiate that andrographolide significantly inhibits iNOS expression and exhibits antiproliferative and proapoptotic effects on cervical cancer cells.

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.

Protective effect of cerium oxide nanoparticles on cisplatin and oxaliplatin primary toxicities in male albino rats

Cisplatin and oxaliplatin are widely used anticancer drugs. Their use is restricted by their dose-limiting side effects: nephrotoxicity and neurotoxicity, respectively. Cerium oxide nanoparticles (CONPs) are promising antioxidant and anti-inflammatory agent. To test the possible ameliorative impact of CONPs on the toxic effect of cisplatin and oxaliplatin in male albino rats. Forty eight rats were divided into 6 groups: control group, CONPs group, cisplatin group, cisplatin and CONPs group, oxaliplatin group, and oxaliplatin and CONPs group. After 4 weeks, serum urea and creatinine, renal tissue level of interleukin 10 (IL10), and total antioxidant (TAO) were measured in control, CONPs, and cisplatin groups. The other kidney was used for histopathological and immunohistochemical studies. The right sciatic nerves and the lumbar spinal cord of rats from control, CONPs, and oxaliplatin groups were used for immunohistochemical evaluations of nitrotyrosine, myelin basic protein (MBP), and glial fibrillary acidic protein (GFAP). Cisplatin significantly increased serum urea and creatinine levels, significantly decreased the kidney level of IL10 and TAO with marked tubular necrosis, hemorrhage and renal damage. Also, it decreased IL10 immunohistochemical expression. CONPs significantly decreased the serum urea and creatinine level and increased IL10 and TAO with lower renal damage and strong IL10 expression compared with cisplatin group. Oxaliplatin significantly decreased MBP immunoreactivity and increased nitrotyrosine immunoreactivity. In the lumbar spinal cord, GFAP immunoreactivity was significantly increased. CONPs significantly increased MBP and decreased nitrotyrosine immunoreactivity. GFAP immunoreactivity was significantly decreased. CONPs ameliorated cisplatin and oxaliplatin primary toxicities through anti-inflammatory and antioxidant characteristics.

Protective effect of magnolol on oxaliplatin-induced intestinal injury in mice

Oxaliplatin (OXL) is the first line treatment therapy for gastrointestinal (GI) cancers and often combines with other chemotherapy. However, few reports have studied on its GI toxicity. Magnolol (MG), one of the mainly active constituents in Magnolia, has been reported to treat digestive diseases. Therefore, the purpose of this study is to evaluate the intestinal protective effect of MG in OXL treatment group. OXL administration mice showed body weight loss, diarrhea, and intestinal damage characterized by the shortening of villi and destruction of intestinal crypts, as well as the colon length change. MG significantly reduced body weight loss, alleviated diarrhea, reversed histopathological changes, and prevented colon length reduction. Oxidative stress and inflammation were activated after OXL, and these responses were repressed by MG through increasing the activities of superoxide dismutase, glutathione peroxidase, and glutathione, decreasing level of nuclear factor of kappa b and downregulating the following pro-inflammatory cytokines. Although the expression of tight junction protein occludin and numbers of proliferative crypt cells were reduced on ileum and colon after OXL, MG administration promoted these expressions. The fecal gut microbiota composition disturbed by OXL was significantly reversed by MG. Thus, MG could prevent the development and progression of mucositis induced by oxaliplatin through multipathway.

Effects of eNOS gene polymorphisms on individual susceptibility to cancer: A meta-analysis

BACKGROUND

Whether endothelial nitric oxide synthase (eNOS) polymorphisms are implicated in cancer development remains controversial. Therefore, we performed this study to obtain a more conclusive result on associations between eNOS polymorphisms and cancer.

METHODS

Literature retrieve was conducted in PubMed, Medline and Embase. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Forty-one studies were enrolled for analyses. Pooled overall analyses showed that rs1799983 (dominant model: p = 0.01; recessive model: p = 0.007; allele model: p = 0.005), rs2070744 (recessive model: p = 0.004) and rs869109213 (recessive model: p < 0.0001; allele model: p = 0.02) polymorphisms were all significantly associated with individual susceptibility to cancer. Further subgroup analyses revealed that rs2070744 and rs869109213 polymorphisms were only significantly associated with individual susceptibility to cancer in Caucasians, whereas the rs1799983 polymorphism was significantly associated with individual susceptibility to cancer in both Caucasians and Asians.

CONCLUSIONS

Our findings indicated that rs1799983, rs2070744 and rs869109213 polymorphisms may serve as genetic biomarkers of cancer in certain ethnicities.

Anticancer Activity of Chitosan, Chitosan Derivatives, and Their Mechanism of Action

Tailoring of chitosan through the involvement of its amino, acetamido, and hydroxy groups can give derivatives of enhanced solubility and remarkable anticancer activity. The general mechanism of such activity is associated with the disturbances in normal functioning of cell cycle, interference to the central dogma of biological system from DNA to RNA to protein or enzymatic synthesis, and the disruption of hormonal path to biosynthesis to inhibit the growth of cancer cells. Both chitosan and its various derivatives have been reported to selectively permeate through the cancer cell membranes and show anticancer activity through the cellular enzymatic, antiangiogenic, immunoenhancing, antioxidant defense mechanism, and apoptotic pathways. They get sequestered from noncancer cells and provide their enhanced bioavailability in cancer cells in a sustained release manner. This review presents the putative mechanisms of anticancer activity of chitosan and mechanistic approaches of structure activity relation upon the modification of chitosan through functionalization, complex formation, and graft copolymerization to give different derivatives.

Expression profile of NF-κB regulated genes in sporadic colorectal cancer patients

Colorectal cancer (CRC) is the fourth leading worldwide cause of cancer-associated mortalities. Nuclear factor-κB (NF-κB) is a transcriptional regulator of multiple genes associated with CRC. Tumor tissue were compared with normal adjacent mucosa from 30 sporadic patients with CRC were investigated. A total of 8 non-CRC patients were analyzed as a control group. In the present study, the protein expression of NF-κB/p65 was detected by immunohistochemistry, and the gene expression profiles of cyclin D1 (CCND1), prostaglandin-endoperoxide synthase 2, vascular endothelial growth factor A, matrix metallopeptidase 9, BCL2 apoptosis regulator (BCL2), BCL2 like 1, nitric oxide synthase 2, tumor necrosis factor and arachidonate lipoxygenase were detected by reverse transcription-quantitative polymerase chain reaction. NF-κB/p65 and genes expression profiles were classified according to tumor-node-metastasis (TNM) clinicopathological parameters, followed by statistical analysis. Higher protein expression of NF-κB/p65 in the cytoplasm of tumor tissues compared with adjacent normal mucosa was reported; this increment was positively associated with all clinicopathological parameters, except for tumor localization site. The selected genes demonstrated a diverse associative pattern when analyzed with clinicopathological parameters. CCND1 was positively associated with all TNM parameters and BCL2 was negatively associated with all TNM parameters, thus indicating their importance as strong molecular biomarkers for CRC. According to these results, not all selected genes regulated by NF-κB/p65 show increased expression during CRC development, whereas the transcription factor did. The present study suggests that NF-κB/p65 overexpression is necessary for CRC establishment and progression, but its transcriptional activity is not sufficient to regulate all target genes in CRC. NF-κB/p65 and the gene expression profiles reported in the present study may be therapeutically useful. Considering the heterogeneity of the disease, the particular evaluation of these molecules may allow for the selection of proper diagnosis, treatment and follow-up for patients with sporadic CRC.

Role of endogenous and exogenous nitric oxide, carbon monoxide and hydrogen sulfide in HCT116 colon cancer cell proliferation

The role of the three gasotransmitter systems - nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) - in cancer cells has not yet been studied simultaneously in the same experimental system. We measured the expression of NO and CO and H2S generating enzymes in primary colon cancer tissues and HCT116 colon cancer cells, and evaluated the effect of their pharmacological inhibition or pharmacological donation on cell proliferation. Increased expression of iNOS, nNOS, HO-1, CBS and 3-MST was detected in colon cancer. Inhibitors of NOS, HO-1/2, CBS/CSE and 3-MST, at lower concentrations, slightly stimulated HCT116 cell proliferation, but inhibited proliferation at higher concentrations. Donors of NO, CO or H2S inhibited HCT116 proliferation in a concentration-dependent manner. Inhibition of the cGMP/VASP pathway, Akt and p44/42 MAPK (Erk1/2) inhibited HCT116 cell proliferation. Endogenous NO and H2S biosynthesis were found to play a role in the maintenance of the activity of the cGMP/VASP pathway in HCT116 cells. We conclude that each of the three gasotransmitters play similar, bell-shaped roles in the control of HCT116 cell proliferation: endogenously produced NO, CO and H2S, at an optimal concentration, support HCT116 proliferation; inhibition of their production (which decreases gasotransmitter levels below optimal concentrations) as well as exogenous delivery of these gasotransmitters (which increases gasotransmitter levels above optimal concentrations) suppresses colon cancer cell proliferation. The current data give a mechanistic explanation for the paradoxical finding that both inhibitors and donors of NO, CO and H2S exert anticancer actions in cancer cells.

A transcriptome-based protein network that identifies new therapeutic targets in colorectal cancer

Background

Colon cancer occurrence is increasing worldwide, making it the third most frequent cancer. Although many therapeutic options are available and quite efficient at the early stages, survival is strongly decreased when the disease has spread to other organs. The identification of molecular markers of colon cancer is likely to help understanding its course and, eventually, to uncover novel genes to be targeted by drugs. In this study, we compared gene expression in a set of 95 human colon cancer samples to that in 19 normal colon mucosae, focusing on 401 genes from 5 selected pathways (Apoptosis, Cancer, Cholesterol metabolism and lipoprotein signaling, Drug metabolism, Wnt/beta-catenin). Deregulation of mRNA levels largely matched that of proteins, leading us to build in silico protein networks, starting from mRNA levels, to identify key proteins central to network activity.

Results

Among the analyzed genes, 10.5% (42) had no reported link with colon cancer, including the SFRP1, IGF1 and ADH1B (down), and MYC and IL8 (up), whose encoded proteins were most interacting with other proteins from the same or even distinct networks. Analyzing all pathways globally led us to uncover novel functional links between a priori unrelated or rather remotely connected pathways, such as the Drug metabolism and the Cancer pathways or, even more strikingly, between the Cholesterol metabolism and lipoprotein signaling and the Cancer pathways. In addition, we analyzed the responsiveness of some of the deregulated genes essential to network activities, to chemotherapeutic agents used alone or in presence of Lovastatin, a lipid-lowering drug. Some of these treatments could oppose the deregulations occurring in cancer samples, including those of the CHECK2, CYP51A1, HMGCS1, ITGA2, NME1 or VEGFA genes.

Conclusions

Our network-based approach allowed discovering genes not previously known to play regulatory roles in colon cancer. Our results also showed that selected drug treatments might revert the cancer-specific deregulation of genes playing prominent roles within the networks operating to maintain colon homeostasis. Among those genes, some could constitute novel testable targets to eliminate colon cancer cells, either directly or, potentially, through the use of lipid-lowering drugs such as statins, in association with selected anticancer drugs.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4139-y) contains supplementary material, which is available to authorized users.

Neuroendocrine factors: The missing link in non‑melanoma skin cancer (Review)

Non‑melanoma skin cancer (NMSC) is the most common form of cancer worldwide, comprising 95% of all cutaneous malignancies and approximately 40% of all cancers. In spite of intensive efforts aimed towards awareness campaigns and sun‑protective measures, epidemiological data indicate an increase in the incidence of NMSC. This category of skin cancers has many common environmental triggers. Arising primarily on sun‑exposed skin, it has been shown that ultraviolet radiation is, in the majority of cases, the main trigger involved in the pathogenesis of NMSC. Aside from the well‑known etiopathogenic factors, studies have indicated that several neuroactive factors are involved in the carcinogenesis of two of the most common types of NMSC, namely basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), with the exception of penile SCC, for which a paucity of specific data on their pathogenic role exists. The complex interaction between the peripheral nervous system and target cells in the skin appears to be mediated by locally released neuroendocrine factors, such as catecholamines, substance P, calcitonin gene‑related peptide and somatostatin, as well as neurohormones, such as proopiomelanocortin and its derived peptides, α‑melanocyte‑stimulating hormone and adrenocorticotropin. All these factors have been, at least at some point, a subject of debate regarding their precise role in the pathogenesis of NMSC. There is also a significant body of evidence indicating that psychological stress is a crucial impact factor influencing the course of skin cancers, including SCC and BCC. Numerous studies have suggested that neuroendocrine factor dysregulation, as observed in stress reactions, may be involved in tumorigenesis, accelerating the development and progression, and suppressing the regression of NMSC. Further studies are required in order to elucidate the exact mechanisms through which neuroactive molecules promote or inhibit cutaneous carcinogenesis, as this could lead to the development of more sophisticated and tailored treatment protocols, as well as open new perspectives in skin cancer research.

Resveratrol alleviates oxidative damage in enteric neurons and associated gastrointestinal dysfunction caused by chemotherapeutic agent oxaliplatin

Oxaliplatin is a first-line chemotherapeutic agent used for the treatment of colorectal cancer. Its use is associated with severe gastrointestinal (GI) side-effects, associated with oxidative damage and neurotoxicity to the enteric neurons. Resveratrol is a potent anti-oxidant that has been shown to protect against oxidative damage and neurotoxicity in other neurons and could therefore prevent oxaliplatin-induced damage to enteric neurons. We determined whether co-administration of resveratrol with oxaliplatin alleviates enteric neuron toxicity and GI dysfunction in mice. Colons were collected for immunohistochemical analysis of myenteric neurons and assessment of motor activity in organ-bath experiments. Morphological damage to the colonic mucosa and muscles was analysed. Oxaliplatin treatment induced translocation of nitrated proteins into the nuclei of myenteric neurons and significant damage to the mucosal lining, vacuolisation and a decrease in muscle thickness. This damage is linked to motor dysfunction due to inhibition of the amplitude of colonic contractions, leading to chronic constipation. Co-treatment with resveratrol prevented oxaliplatin-induced neurotoxicity, alleviated damage to GI mucosa, crypts and muscle layer, resulting in improved contractility and a decrease in constipation. Resveratrol could be integrated as part of a therapeutic regimen to help alleviate oxaliplatin-induced GI dysfunction.

Potential biomarkers associated with oxidative stress for risk assessment of colorectal cancer

Cells are continuously threatened by the damage caused by reactive oxygen/nitrogen species (ROS/RNS), which are produced during physiological oxygen metabolism. In our review, we will summarize the latest reports on the role of oxidative stress and oxidative stress-induced signaling pathways in the etiology of colorectal cancer. The differences in ROS generation may influence the levels of oxidized proteins, lipids, and DNA damage, thus contributing to the higher susceptibility of colon. Reactive species (RS) of various types are formed and are powerful oxidizing agents, capable of damaging DNA and other biomolecules. Increased formation of RS can promote the development of malignancy, and the "normal" rates of RS generation may account for the increased risk of cancer development in the aged. In this review, we focus on the role of oxidative stress in the etiology of colorec-tal cancer and discuss free radicals and free radical-stimulated pathways in colorectal carcinogenesis.

Role of oxidative stress in oxaliplatin-induced enteric neuropathy and colonic dysmotility in mice

BACKGROUND AND PURPOSE

Oxaliplatin is a platinum-based chemotherapeutic drug used as a first-line therapy for colorectal cancer. However, its use is associated with severe gastrointestinal side-effects resulting in dose limitations and/or cessation of treatment. In this study, we tested whether oxidative stress, caused by chronic oxaliplatin treatment, induces enteric neuronal damage and colonic dysmotility.

EXPERIMENTAL APPROACH

Oxaliplatin (3 mg·kg^-1 per day) was administered in vivo to Balb/c mice intraperitoneally three times a week. The distal colon was collected at day 14 of treatment. Immunohistochemistry was performed in wholemount preparations of submucosal and myenteric ganglia. Neuromuscular transmission was studied by intracellular electrophysiology. Circular muscle tone was studied by force transducers. Colon propulsive activity studied in organ bath experiments and faeces were collected to measure water content.

KEY RESULTS

Chronic in vivo oxaliplatin treatment resulted in increased formation of reactive oxygen species (O₂ -), nitration of proteins, mitochondrial membrane depolarisation resulting in the release of cytochrome c, loss of neurons, increased inducible NOS expression and apoptosis in both the submucosal and myenteric plexuses of the colon. Oxaliplatin treatment enhanced NO-mediated inhibitory junction potentials and altered the response of circular muscles to the NO donor, sodium nitroprusside. It also reduced the frequency of colonic migrating motor complexes and decreased circular muscle tone, effects reversed by the NO synthase inhibitor, Nω-Nitro-L-arginine.

CONCLUSION AND IMPLICATIONS

Our study is the first to provide evidence that oxidative stress is a key player in enteric neuropathy and colonic dysmotility leading to symptoms of chronic constipation observed in oxaliplatin-treated mice.

Evaluation of iNOS Expression in Esophageal Cancer Patients

BACKGROUND

Esophageal cancer is a public health concern around the world; this cancer is the sixth leading cause of death of cancer in the world with about 386,000 deaths per year. Its risk factors include environmental factors such as tobacco smoke, gastroesophageal reflux and genetic changes. iNOS is stated by the effect of various inflammatory factors and is thus called inducible NOS. Investigating iNOS expression is a powerful tool for understanding effective molecular parameters at tissue and cellular responses to external factors. In this research work, iNOS expression in patients with esophageal cancer was studied in Iran.

MATERIALS AND METHODS

15 formalin-fixed and paraffin-embedded (FFPE) esophageal cancer tissue samples and 15 normal FFPE samples were collected from various medical centers (Zabol, Zahedan, Kashan) to measure iNOS expression by real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR). All PCR reactions were conducted by three replicates for iNOS and internal control (β-actin) by 2^-ΔΔCT (Livak) method. Differences were measured in target gene expression in patients and control group using the t test. All statistical analyses were done using the SPSS software.

RESULTS

The results showed that there was no significant difference between iNOS expression in the case and control groups (p > 0.05); however, there was an increase in iNOS expression in the case group. On the other hand, there was a significant difference between iNOS expression in males and females in the two groups of healthy subjects and patients, and it was higher in women than in men.

CONCLUSION

Further studies need to be conducted with larger sample sizes and in other populations to validate these findings.

Radioprotection of 1,2-dimethylhydrazine-initiated colon cancer in rats using low-dose γ rays by modulating multidrug resistance-1, cytokeratin 20, and β-catenin expression

Ionizing radiation is a widely used therapy for solid tumors. However, high-dose ionizing radiation causes apoptosis, transforms normal cells into tumor cells, and impairs immune functions, leading to the defects in the removal of damaged or tumor cells. In contrast, low-dose radiation has been reported to exert various beneficial effects in cells. This experimental study investigated the effect of γ rays at low dose on the development of colorectal tumor in a 1,2-dimethylhydrazine (DMH)-induced colon cancer. Colorectal tumor model was induced in Wistar rats by subcutaneous injection of DMH (20 mg/kg) once a week for 15 weeks. Starting from zero day of DMH injection, a single low dose of whole-body γ irradiation of 0.5 Gy/week was applied to the rats. A significant reduction in lipid peroxidation, nitric oxide, and elevation in the glutathione content and antioxidant enzyme activity (superoxide dismutase and catalase) were observed after γ irradiation comparing with DMH group. Moreover, γ ray reduced the expressions of multidrug resistance 1 (MDR1), β-catenin, and cytokeratin 20 (CK20) those increased in DMH-treated rats. However, survivin did not change with γ ray treatment. A histopathological examination of the DMH-injected rats revealed ulcerative colitis, dysplasia, anaplasia, and hyperchromasia. An improvement in the histopathological picture was seen in the colon of rats exposed to γ rays. In conclusion, the present results showed that low-dose γ ray significantly inhibited DMH-induced colon carcinogenesis in rats by modulating CK20, MDR1, and β-catenin expression but not survivin expression.

Quantitative measurement of iNOS expression in melanoma, nasopharyngeal, colorectal, and breast tumors of Tunisian patients: comparative study and clinical significance

Chronic inflammation increases the risk of development of human malignancies. iNOS is an enzyme dominantly expressed during inflammatory reactions and seems to play a critical role in tumorigenesis. Our aim was to assess the iNOS expression in four types of human tumors: breast, colorectal, nasopharyngeal, and melanoma, of Tunisian patients. The level of iNOS was measured by RT-QPCR in tumor specimens. We showed that the expression of iNOS was higher in breast compared to colorectal and nasopharyngeal tumors, whereas in melanoma, the level of iNOS expression was low. Significant associations were found when comparing the iNOS expression in cancers pairs such as melanoma versus colorectal (p < 0.0001), colorectal versus nasopharyngeal (p = 0.0072), and melanoma versus breast (p < 0.0001). Furthermore, iNOS expression correlated with the Breslow thickness, Clark level, and histological subtype in melanoma, while in nasopharyngeal carcinoma, significant association was seen with age at diagnosis, TNM, metastasis, response to treatment, and expression of COX-2. Furthermore, the expression of iNOS correlated with tumor size, TNM, tumor location, and histological type in colorectal cancer, and with tumor size, tumor stage, SBR grade, and triple negative cases in breast cancer. On the other hand, immunohistochemistry analysis shows that the expression of iNOS is observed in the stroma and tumor cells as well. Overall, our results highlight that iNOS is a reliable marker for advanced stage and aggressive behavior for the four types of cancer and might be a potential promising therapeutic target.

Luteolin, a bioflavonoid inhibits colorectal cancer through modulation of multiple signaling pathways: a review

Luteolin, 3', 4', 5,7-tetrahydroxyflavone, belongs to a group of naturally occurring compounds called flavonoids that are found widely in the plant kingdom. It possesses many beneficial properties including antioxidant, anti- inflammatory, anti-bacterial, anti-diabetic and anti-proliferative actions. Colorectal cancer (CRC) is a leading cause of cancer related deaths worldwide. Many signaling pathways are deregulated during the progression of colon cancer. In this review we aimed to analyze the protection offered by luteolin on colon cancer. During colon cancer genesis, luteolin known to reduce oxidative stress thereby protects the cell to undergo damage in vivo. Wnt/β-catenin signaling, deregulated during neoplastic development, is modified by luteolin. Hence, luteolin can be considered as a potential drug to treat CRC.

Caenorhabditis elegans as a model for cancer research

The term cancer describes a group of multifaceted diseases characterized by an intricate pathophysiology. Despite significant advances in the fight against cancer, it remains a key public health concern and burden on societies worldwide. Elucidation of key molecular and cellular mechanisms of oncogenic diseases will facilitate the development of better intervention strategies to counter or prevent tumor development. In vivo and in vitro models have long been used to delineate distinct biological processes involved in cancer such as apoptosis, proliferation, angiogenesis, invasion, metastasis, genome instability, and metabolism. In this review, we introduce Caenorhabditis elegans as an emerging animal model for systematic dissection of the molecular basis of tumorigenesis, focusing on the well-established processes of apoptosis and autophagy. Additionally, we propose that C. elegans can be used to advance our understanding of cancer progression, such as deregulation of energy metabolism, stem cell reprogramming, and host-microflora interactions.

Dietary administration of Nexrutine inhibits rat liver tumorigenesis and induces apoptotic cell death in human hepatocellular carcinoma cells

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Nexrutine has anti-tumor potential in Solt-Farber rat liver tumorigenesis model.

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Nexrutine caused decreased cell proliferation in the DEN/2-AAF treated rats.

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It decreases cell viability of liver cancer cells and modulates pro- and anti-apoptotic markers.

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Nexrutine modulates the cell cycle regulatory proteins and MAPKs.

Epidemiological studies suggested that plant-based dietary supplements can reduce the risk of liver cancer. Nexrutine (NX), an herbal extract from Phellodendronamurense, has been shown to have anti-inflammatory, anti-microbial and anti-tumor activities. In the present study, we have shown the anti-tumor potential of NX against Solt-Farber model with elimination of PH, rat liver tumor induced by diethylnitrosoamine (DEN) as carcinogen and 2-acetylaminofluorene (2-AAF) as co-carcinogen. The elucidation of mechanistic pathways was explored in human liver cancer cells. Dietary intake of NX significantly decreased the cell proliferation and inflammation, as well as increased apoptosis in the liver sections of DEN/2-AAF-treated rats. Moreover, NX (2.5–10 μg/ml) exposure significantly decreased the viability of liver cancer cells and modulated the levels of Bax and Bcl-2 proteins levels. NX treatment resulted in increased cytochrome-c release and cleavage of caspases 3 and 9. In addition, NX decreased the expression of CDK2, CDK4 and associated cyclins E1 and D1, while up-regulated the expression of p21, p27 and p53 expression. NX also enhanced phosphorylation of the mitogen-activated protein kinases (MAPKs) ERK1/2, p38 and JNK1/2. Collectively, these findings suggested that NX-mediated protection against DEN/2-AAF-induced liver tumorigenesis involves decrease in cell proliferation and enhancement in apoptotic cell death of liver cancer cells.

The role of inflammation in colon cancer

Colorectal cancer (CRC) is the one of the leading causes of cancer-related deaths in the world. CRC is responsible for more than 600,000 deaths annually and incidence rates are increasing in most of the developing countries. Epidemiological and laboratory investigations suggest that environmental factors such as western style dietary habits, tobacco-smoking, and lack of physical activities are considered as risks for CRC. Molecular pathobiology of CRC implicates pro-inflammatory conditions to promote the tumor malignant progression, invasion, and metastasis. It is well known that patients with inflammatory bowel disease are at higher risk of CRC. Many evidences exist reiterating the link between Inflammation and CRC. Inflammation involves interaction between various immune cells, inflammatory cells, chemokines, cytokines, and pro-inflammatory mediators, such as cyclooxygenase (COX) and lipoxygenase (LOX) pathways, which may lead to signaling towards, tumor cell proliferation, growth, and invasion. Thus, this review will focus on mechanisms by which pro-inflammatory mediators and reactive oxygen/nitrogen species play a role in promoting CRC. Based on these mechanisms, various preventive strategies, involving anti-inflammatory agents, such as COX inhibitors, COX-LOX inhibitors, iNOS inhibitors, natural supplements/agents, and synthetic agents, that blocks the inflammatory pathways and suppress CRC are discussed in this review.

Nitric oxide and cancer: a review

Nitric oxide (NO), is a ubiquitous, water soluble, free radical gas, which plays key role in various physiological as well as pathological processes. Over past decades, NO has emerged as a molecule of interest in carcinogenesis and tumor growth progression. However, there is considerable controversy and confusion in understanding its role in cancer biology. It is said to have both tumoricidal as well as tumor promoting effects which depend on its timing, location, and concentration. NO has been suggested to modulate different cancer-related events including angiogenesis, apoptosis, cell cycle, invasion, and metastasis. On the other hand, it is also emerging as a potential anti-oncogenic agent. Strategies for manipulating in vivo production and exogenous delivery of this molecule for therapeutic gain are being investigated. However, further validation and experimental/clinical trials are required for development of novel strategies based on NO for cancer treatment and prevention. This review discusses the range of actions of NO in cancer by performing an online MEDLINE search using relevant search terms and a review of the literature. Various mechanisms by which NO acts in different cancers such as breast, cervical, gastric,colorectal, and head and neck cancers are addressed. It also offers an insight into the dichotomous nature of NO and discusses its novel therapeutic applications for cancer prevention and treatment.

Link between cancer and Alzheimer disease via oxidative stress induced by nitric oxide-dependent mitochondrial DNA overproliferation and deletion

Nitric oxide- (NO-) dependent oxidative stress results in mitochondrial ultrastructural alterations and DNA damage in cases of Alzheimer disease (AD). However, little is known about these pathways in human cancers, especially during the development as well as the progression of primary brain tumors and metastatic colorectal cancer. One of the key features of tumors is the deficiency in tissue energy that accompanies mitochondrial lesions and formation of the hypoxic smaller sized mitochondria with ultrastructural abnormalities. We speculate that mitochondrial involvement may play a significant role in the etiopathogenesis of cancer. Recent studies also demonstrate a potential link between AD and cancer, and anticancer drugs are being explored for the inhibition of AD-like pathology in transgenic mice. Severity of the cancer growth, metastasis, and brain pathology in AD (in animal models that mimic human AD) correlate with the degree of mitochondrial ultrastructural abnormalities. Recent advances in the cell-cycle reentry of the terminally differentiated neuronal cells indicate that NO-dependent mitochondrial abnormal activities and mitotic cell division are not the only important pathogenic factors in pathogenesis of cancer and AD, but open a new window for the development of novel treatment strategies for these devastating diseases.

Effects of oxaliplatin on mouse myenteric neurons and colonic motility

Oxaliplatin, an anti-cancer chemotherapeutic agent used for the treatment of colorectal cancer, commonly causes gastrointestinal side-effects such as constipation, diarrhoea, nausea, and vomiting. Damage to enteric neurons may underlie some of these gastrointestinal side-effects, as the enteric nervous system (ENS) controls functions of the bowel. In this study, neuronal loss and changes to the structure and immunoreactivity of myenteric neuronal nitric oxide synthase (nNOS) neurons were examined in colonic segments from mice following exposure to oxaliplatin ex vivo and following repeated intraperitoneal injections of oxaliplatin over 3 weeks in vivo, using immunohistochemistry and confocal microscopy. Significant morphological alterations and increases in the proportion of NOS-immunoreactive (IR) neurons were associated with both short-term oxaliplatin exposure and long-term oxaliplatin administration, confirming that oxaliplatin causes changes to the myenteric neurons. Long-term oxaliplatin administration induced substantial neuronal loss that was correlated with a reduction in both the frequency and propagation speed of colonic migrating motor complexes (CMMCs) in vitro. Similar changes probably produce some symptoms experienced by patients undergoing oxaliplatin treatment.

Molecular docking studies of quercetin and its analogues against human inducible nitric oxide synthase

Nitric oxide synthases (NOS) catalyze to produce nitric oxide (NO) from L-arginine. The isoform of NOS i.e. inducible nitric oxide synthases (iNOS) expression is observed in various human malignant tumors such as breast, lung, prostate and bladder, colorectal cancer, and malignant melanoma. Also an increased level of iNOS expression and activity has been found in the tumor cells of gynecological malignancies, stroma of breast cancer and tumor cells of head and neck cancer. Because of its importance in causing tumors and cancer, iNOS enzyme has become a new target in finding novel inhibitors as anti cancer agents. The present work focuses on the molecular docking analysis of quercetin and its analogues against iNOS enzyme. Earlier there are reports of quercetin inhibiting iNOS enzyme in certain experiments as anti cancer agent. But the clinical use of quercetin is limited by its low oral bioavailability and therefore needed its molecular modification to improve its pharmacological properties. In the present study ten analogues of quercetin were found to be docked at the active site cavity with favorable ligand-protein molecular interaction and interestingly from the ADME-Toxicity analysis these analogues have enhanced pharmacological properties than quercetin.

iNOS-selective inhibitors for cancer prevention: promise and progress

Nitric oxide (NO) is involved in various physiological functions and its role in tumorigenesis has been well studied. A large majority of human and experimental tumors appear to progress owing to NO resulting from iNOS, further stimulated by proinflammatory cytokines. Conversely, in some cases, NO is associated with induction of apoptosis and tumor regression. This dichotomy of NO is largely explained by the complexity of signaling pathways in tumor cells, which respond to NO very differently depending on its concentration. In addition, NO alters many signaling pathways through chemical modifications, such as the addition of S-nitrosothiols and nitrosotyrosine to target proteins altering various biological pathways. Hence, iNOS inhibitors are designed and developed to inhibit various organ site cancers including the colon. Here, we review iNOS expression, generation of NO, involvement of NO in altering signaling pathways, and iNOS select inhibitors and their possible use for the prevention and treatment of various cancers.

Differential inhibitory effects of the polyphenol ellagic acid on inflammatory mediators NF-kappaB, iNOS, COX-2, TNF-alpha, and IL-6 in 1,2-dimethylhydrazine-induced rat colon carcinogenesis

Dietary polyphenols have been found to possess preventive and therapeutic potential against several types of cancers. We investigated the effect of ellagic acid on colon cancer induced by 1,2-dimethylhydrazine in rats. Male Wistar albino rats were divided into four groups. Group 1 served as control, group 2 rats received ellagic acid 60 mg/kg bodyweight/every day p.o. throughout the experiment. Rats from groups 3 and 4 were given subcutaneous (s.c.) injections of 1,2-dimethylhydrazine (20 mg/kg body weight) once a week for the first 15 weeks; rats in group 4 received ellagic acid as in group 2 after the last injection of 1,2-dimethylhydrazine and continued till the end of the experimental period of 30 weeks. 1,2-dimethylhydrazine-induced rats exhibited alterations in cancer tumour markers [5'-nucleotidase (5'-ND), gamma glutamyl transpeptidase (gamma-GT), carcinoembryonic antigen (CEA), alphafetoprotein (AFP) and cathepsin-D (CD)]; pathophysiological markers [alkaline phosphatase (ALP) and lactate dehydrogenase (LDH)] and oral administration of ellagic acid restored the levels of these marker enzymes. Nuclear factor-kappa B (NF-kappaB) actively involved in the regulation of both pro-inflammatory proteins [inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2)] and pro-inflammatory cytokines [tumour necrosis factor (TNF)-alpha and interleukin (IL)-6] and in our study 1,2-dimethylhydrazine-induced group exhibited elevated expressions of all these inflammatory proteins. Ellagic acid administration reduced the expressions of NF-kappaB, COX-2, iNOS, TNF-alpha and IL-6 as confirmed by immunohistochemical, immunoblot and immunofluorescence analysis during 1,2-dimethylhydrazine-induced colon carcinogenesis. In conclusion, ellagic acid demonstrates anti-inflammatory property by iNOS, COX-2, TNF-alpha and IL-6 down-regulation due to inhibition of NF-kappaB and exerts its chemopreventive effect on colon carcinogenesis.

Cyclooxygenase-2 in tumorigenesis of gastrointestinal cancers: an update on the molecular mechanisms

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with lower risks for esophageal, gastric and colon cancers as well as other solid tumors. The antitumor effect of NSAIDs is mediated through cyclooxygenase-2 (COX-2)-dependent and -independent regulation of oncogenic and tumor-suppressive pathways. Recent discoveries have shed new light on the regulation of COX-2 at the molecular level in these cancers. Moreover, prostaglandin E(2) (PGE(2)), a COX-2-derived eicosanoid, has been found to affect numerous tumorigenic processes. In this connection, PGE(2) activates multiple intracellular signaling pathways, including (1) transactivation of epidermal growth factor receptor (EGFR); (2) protein kinase C-dependent, EGFR-independent activation of extracellular signal-regulated kinase (ERK) and the transcription factors activator protein-1 and c-Myc; (3) G-protein-mediated activation of beta-catenin/TCF-dependent transcription. Activation of these signaling pathways by PGE(2) is mediated by EP receptors whose inhibitors suppress gastrointestinal carcinogenesis. Taken together, COX-2 expression is dysregulated in many types of cancer and COX-2-derived PGE(2) elicits multiple oncogenic signals to promote carcinogenesis. Targeting PGE(2) signaling by EP receptor antagonists holds promise for the development of targeted therapy for the treatment of cancer.

Anti-cancer activity of nitrones in the Apc(Min/+) model of colorectal cancer

Abstract The nitrones of alpha-phenyl-tert-butyl nitrone (PBN) and 4-hydroxyl-PBN (4-OH-PBN) that have anti-cancer activity in models of liver cancer and glioblastomas were tested in the ApcMin/+ mouse model. Mice were administered PBN and 4-OH-PBN in drinking water and intestinal tumour size and number assessed after 3-4 months. Throughout the experiment, contrast-enhanced magnetic resonance imaging (MRI) was used to monitor colon tumours. MRI data showed a time-dependent significant increase in total colonic signal intensity in sham-treated mice, but a significant decrease for PBN-treated mice and slight decrease for 4-OHPBN treated mice, probably due to the limited water solubility of 4-OH-PBN. Final pathological and percentage survival data agreed with the MRI data. PBN had little effect on oxaliplatin-mediated killing of HCT116 colon cancer cells and caused only a slight decrease in the amount of active fraction caspase 3 in oxaliplatin-treated cells. PBN has significant anti-cancer activity in this model of intestinal neoplasia.

Inducible nitric oxide synthase expression and its prognostic significance in colorectal cancer

Nitric oxide synthases (NOS) are expressed in colorectal cancer. The aim of this study was to examine the inducible NOS (iNOS) expression in colorectal cancer and to investigate its prognostic relevance. Tissue sections of primary tumors from 132 patients undergoing curative resection for colorectal cancer were immunohistochemically examined for iNOS expression. The expression pattern of iNOS was correlated with various clinicopathological characteristics and survival. iNOS immunoreactivity was observed in the cytoplasm of tumor epithelial cells in 60 patients (45.5%) and positively correlated with lymph node involvement (p = 0.019). No significant correlation was found between iNOS expression and various clinicopathological characteristics, including age, gender, tumor location, tumor size, tumor grade, T stage, and Union International Contra la Cancrum (UICC) stage. Survival analysis showed a significant correlation between iNOS-positive tumors and poor disease-specific survival (p < 0.0001), with independent prognostic significance in multivariate analysis (HR = 4.42; p < 0.0001). Patients with stage II disease and iNOS-positive tumors had significantly worse disease-specific survival than those with iNOS-negative tumors (p < 0.0001). In addition, patients with stage III disease and iNOS-positive tumors had significantly worse disease-specific survival than those with iNOS-negative tumors (p = 0.001). The ability of iNOS to predict outcome in colorectal cancer patients may be independent of other known prognostic factors, providing a new molecular marker with significant potential for clinical utility.

An intron 4 VNTR polymorphism of the endothelial nitric oxide synthase gene is associated with early-onset colorectal cancer

Endothelial-derived nitric oxide, which is produced by endothelial nitric oxide synthase (eNOS), may play an important role in colorectal carcinogenesis. However, the putative contribution of common eNOS genetic polymorphisms to colorectal cancer risk remains unknown. We genotyped 3 polymorphisms of eNOS (T-786C, G894T, and intron4b/a) in 727 colorectal adenocarcinoma cases and 736 age- and sex-matched healthy controls in Taiwan. Genotypes of the T-786C and G894T polymorphisms were determined by fluorescence polarization assays and the 27-bp variable number of tandem repeat (VNTR) polymorphism in intron 4 (intron4b/a) was analyzed by PCR. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Among younger participants (< or =60 yrs), the intron4a variant genotype was associated with a significantly increased risk of colorectal cancer, compared with the intron4bb genotype (OR = 1.60, 95% CI = 1.04-2.46). In addition, those young individuals bearing a greater number of high-risk genotypes (OR > 1, i.e., CT+TT for T-786C, ba+aa for intron4b/a, and GG for G894T) of eNOS had a higher colorectal cancer risk (p(trend) = 0.039). Compared with younger individuals without any putative high-risk genotypes, those with 3 high-risk genotypes had a significantly greater cancer risk (OR = 1.89, 95% CI = 1.04-3.43). Our results suggest that the eNOS intron4b/a polymorphism may contribute to early-onset colorectal cancer risk in the Taiwanese population.

Elevated insulin-like growth factor 1 receptor, hepatocyte growth factor receptor and telomerase protein expression in mild ulcerative colitis

OBJECTIVE

The risk of development of colorectal carcinoma is elevated in chronic, long-standing ulcerative colitis (UC). The changes in regenerative and immortalizing pathways caused by the inflammatory process, and that have been proved to be carcinogenic in other human tissues, have not been fully and uniformly described. We assayed the expression alterations of regenerative signal receptors and cell-aging inhibitory systems within colonic crypts by considering the histological activity of the disease.

METHODS

I-type insulin-like growth factor receptor (IGF1R), hepatocyte growth factor receptor (HGFR), telomerase reverse transcriptase (TERT) and telomerase associated protein (TP-1) expression were evaluated immunohistochemically on biopsy specimens from 11 mild, 11 moderate and 12 severe active inflammation of UC cases and from 10 normal colonic tissue cases. Independent colonic biopsies from 5 healthy and 7 severe UC cases were used for TaqMan real-time RT-PCR validation.

RESULTS

In mild inflammation, all observed parameters showed significantly elevated epithelial protein expression (IGF1R: 22.3 +/- 9.46%; HGFR: 35.3 +/- 22.8%; TERT/TP-1: 2.1 +/- 1.87%/2 +/- 1.32%) compared to normal (p < 0.005). In moderately active inflammation, only IGF1R expression was significantly higher (50.2 +/- 8.6%) compared to normal and mild inflammation (p < 0.005). In severe inflammation, all parameters showed decreased epithelial expression; IGF1R showed decreased mRNA expression, while HGFR was overexpressed and TERT showed a decreased tendency.

CONCLUSIONS

The epithelial expression of IGF1R, HGFR and TERT/TP-1 is elevated in mildly active UC. This phenomenon may allow the epithelial cells that collected genetic defects during severe inflammatory episodes pathologically to survive and proliferate.

Cellular mechanisms involved in the melatonin inhibition of HT-29 human colon cancer cell proliferation in culture

The antiproliferative and proapoptotic properties of melatonin in human colon cancer cells in culture were recently reported. To address the mechanisms involved in these actions, HT-29 human colon cancer cells were cultured in RPMI 1640 medium supplemented with fetal bovine serum at 37 degrees C. Cell proliferation was assessed by the incorporation of [(3)H]-thymidine into DNA. Cyclic nucleotide levels, nitrite concentration, glutathione peroxidase and reductase activities, and glutathione levels were assessed after the incubation of these cells with the following drugs: melatonin membrane receptor agonists 2-iodo-melatonin, 2-iodo-N-butanoyl-5-methoxytryptamine, 5-methoxycarbonylamino-N-acetyltryptamine (GR-135,531), and the antagonists luzindole, 4-phenyl-2-propionamidotetralin, and prazosin; the melatonin nuclear receptor agonist CGP 52608, and four synthetic kynurenines analogs to melatonin 2-acetamide-4-(3-methoxyphenyl)-4-oxobutyric acid, 2-acetamide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid, 2-butyramide-4-(3-methoxyphenyl)-4-oxobutyric acid and 2-butyramide-4-(2-amino-5-methoxyphenyl)-4-oxobutyric acid. The results show that the membrane receptors are not necessary for the antiproliferative effect of melatonin and the participation of the nuclear receptor in this effect is suggested. Moreover, the antioxidative and anti-inflammatory actions of melatonin, counteracting the oxidative status and reducing the production of nitric oxide by cultured HT-29 cells seem to be directly involved in the oncostatic properties of melatonin. Some of the synthetic kynurenines exert higher antiproliferative effects than melatonin. The results reinforce the clinical interest of melatonin due to the different mechanisms involved in its oncostatic role, and suggest a new synthetic pathway to obtain melatonin agonists with clinical applications to oncology.

Involvement of nitric oxide in the inhibition of bone cancer-induced hyperalgesia through the activation of peripheral opioid receptors in mice

Experiments were designed to elucidate the involvement of nitric oxide (NO) in the antihyperalgesic effect induced by the activation of peripheral mu-opioid receptors on osteosarcoma-induced thermal hyperalgesia in mice. Since this pathway has previously been shown to be involved in the antihyperalgesic effect induced by some drugs--including opiates--on inflammatory pain, experiments were also performed in inflamed mice. The intraplantar administration of loperamide (15 microg) abolishes the thermal hyperalgesia that appears 4 weeks after the intratibial inoculation of NCTC 2472 cells in C3H/HeJ mice. The blockade of this effect by coadministering a peripheral opioid receptor antagonist (naloxone methiodide), a nitric oxide synthase (NOS) inhibitor (L-NMMA), a soluble guanylyl cyclase inhibitor (ODQ), a PKG inhibitor (KT-5823) or a K(+)(ATP)-channel blocker (glibenclamide) shows the involvement of a NO/cGMP/K(+)(ATP)-channel pathway. Accordingly the administration of loperamide produced, in osteosarcoma-bearing mice, an increase in the concentrations of NO metabolites, nitrites and nitrates, extracted from paws. The selective inhibitor of eNOS L-NIO, but not the inhibitors of nNOS (N-omega-propyl-L-arginine) or iNOS (1400w), blocked the effect of loperamide on osteosarcoma-induced hyperalgesia and also the endogenous opioid peripheral hypoalgesia that appears during the initial stages of the development of this osteosarcoma. Although this pathway also participates in the inhibitory effect of loperamide on the thermal hyperalgesia induced by administration of complete Freund's adjuvant, only selective inhibitors of nNOS or iNOS antagonized this effect. Our results demonstrate that the activation of a NO/cGMP/K(+)(ATP)-channel triggered by eNOS participates in the peripheral antihyperalgesic of loperamide on osteosarcoma-induced thermal hyperalgesia.

Inhibitory effects of asiatic acid on 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol 13-acetate-induced tumor promotion in mice

Asiatic acid, a pentacyclic triterpene, has been reported to induce apoptosis of various human cancer cells. In the present study, we assessed the anti-tumor promoting effect of asiatic acid against 12-O-tetradecanoylphorbol 13-acetate (TPA)-mediated skin tumorigenesis in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated ICR mice. Topical application of asiatic acid prior to each application of TPA resulted in a significant reduction in skin tumor formation. We also found that pre-application of asiatic acid alleviated TPA-induced [3H]thymidine incorporation, which is a conventional marker for skin tumor promotion. In addition, asiatic acid inhibited the TPA-induced generation of nitric oxide (NO) and expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), which are known to play important roles in tumor growth, especially in the promotion stage. In addition, topical application of aminoguanidine (AG), a selective iNOS inhibitor, and N(G)-nitro-L-arginine-methyl ester (NAME), another iNOS inhibitor, 30 min prior to TPA treatment significantly inhibited the TPA-induced COX-2 expression. These results suggest that asiatic acid may exert anti-tumorigenesis through inhibitory actions in NO and COX-2 signals.

Deoxycholate-induced colitis is markedly attenuated in Nos2 knockout mice in association with modulation of gene expression profiles

Nos2 knockout mice were compared to wild-type mice for susceptibility to colitis in response to a diet supplemented with deoxycholate, a bile acid increased in the colon of individuals on a high-fat diet. Wild-type mice fed a fat-related diet, supplemented with 0.2% DOC, develop colonic inflammation associated with increases in nitrosative stress, proliferation, oxidative DNA/RNA damage, and angiogenesis, as well as altered expression of numerous genes. However, Nos2 knockout mice fed a diet supplemented with deoxycholate were resistant to these alterations. In particular, 35 genes were identified whose expression was significantly altered at the mRNA level in deoxycholate-fed Nos2(+/+) mice but not in deoxycholate-fed Nos2(-/-) mice. Some of these alterations in NOS2-dependent gene expression correspond to those reported in human inflammatory bowel disease. Overall, our results indicate that NOS2 expression is necessary for the development of deoxycholate-induced colitis in mice, a unique dietary-related model of colitis.

Increased protein expression of both inducible nitric oxide synthase and cyclooxygenase-2 in human colon cancers

The present study was conducted to investigate protein levels of inducible NO synthase (iNOS) and cayclooxygenase-2 (COX-2) in human colon cancer tissues. Significant increase of iNOS and COX-2 levels in tumors as compared to paired normal tissue was observed in 15 and 28, respectively, of 29 cases investigated. No correlation was observed between the two enzymes, and immunohistochemically demonstrated iNOS expression was mainly observed in tumor epithelial cells and was higher in well-differentiated than moderately-differentiated adenocarcinomas, while COX-2 expression was mainly detected in stromal cells and higher in Dukes' C and D than Dukes' A and B cases. These results suggest that iNOS and COX-2 have separate roles in colon carcinogenesis, and might both be usefully targeted by chemoprevention.

Nitric oxide promotes resistance to tumor suppression by CTLs

Many human tumors express inducible NO synthetase (NOS2), but the roles of NO in tumor development are not fully elucidated. An important step during tumor development is the acquisition of apoptosis resistance. We investigated the dose-dependent effects of endogenously produced NO on apoptosis using ecdysone-inducible NOS2 cell lines. Our results show that short-term NOS2 expression enhances CD95-mediated apoptosis and T cell cytotoxicity dose dependently. Furthermore, we could show that during chronic exposure to NO, besides the primary cytotoxic NO effect, there is selection of cell clones resistant to NO that show cross-resistance to CD95-induced apoptosis and the killing by CTLs. We propose that NO production could initially act as an autocrine suicide or paracrine killing mechanism in cells undergoing malignant transformation. However, once failed, the outcome is fatal. NO promotes tumor formation by enhancing the selection of cells that can evade immune attack by acquiring apoptosis resistance.

Nitric oxide and metastatic cell behaviour

Nitric oxide (NO) is a pleiotropic signalling molecule that subserves a wide variety of basic cellular functions and also manifests itself pathophysiologically. As regards cancer and its progression, however, the reported role of NO appears surprisingly inconsistent. In this review, we focus on metastasis, the process of cancer cell spread and secondary tumour formation. In a 'reductionist' approach, we consider the metastatic cascade to be made up of a series of basic cellular behaviours (such as proliferation, apoptosis, adhesion, secretion migration, invasion and angiogenesis). We evaluate how NO controls such behaviours, in comparison with normal cells. The available information suggests strongly that NO signalling would be expected to regulate these behaviours both positively and negatively and this probably leads to the observed apparent variability in the NO status of cancer cells and tissues. Thus, the role of NO in cancer is more complex than previously thought. A number of suggestions are made, including consideration of novel mechanisms, such as ion channels, in order to achieve a more consistent and integrated understanding of NO signalling in cancer and to realise its clinical potential.