[Show abstract][Hide abstract] ABSTRACT: Objectives
Investigators hypothesized that cancer stem cells (CSCs) could play a role in determining cancer progression by metastasizing to cervical lymph node (N+) and then influencing prognosis of head and neck squamous cell carcinomas (HNSCCs) patients. DesignTo identify CSCs in HNSCCs and their clonogenic capacity. SettingIn vitro study. ParticipantsPutative CSCs from 29 primary HNSCCs and 19 corresponding node metastases were analyzed. Main outcome measuresImmunohistochemical (IHC) was performed, and CSCs' clonogenic in vitro capacity was tested; ones epithelial nature of cancer cells forming colonies was confirmed by a second IHC, fluorescence-activated cell sorting (FACS) analysis helped in counting CD44/CD133-CSCs markers percentage expression in HNSCC tumour-derived cultures. ResultsImmunohistochemical showed CD44 (93.1%) and CD133 (10.34%) expression; FACS-analysis showed the enrichment of CD44/CD133 cancer cells, with the highest clonogenic capacity of CD44+-subpopulation; a higher CD44 rates were documented from N+ subcultures than from original tumours (P<0.05). ConclusionsA putative cancer stem-like cell population is detectable in HNSCCs, and our findings show their in vitro clonogenic capacity by demonstrating that CD44+-cultured cells are the main population proliferating obtained by N+ HNSCC metastases, emphasizing their possible role in tumour progression.
Full-text · Article · Jan 2015 · Clinical otolaryngology: official journal of ENT-UK; official journal of Netherlands Society for Oto-Rhino-Laryngology & Cervico-Facial Surgery
[Show abstract][Hide abstract] ABSTRACT: The inability of endothelial cells of patients affected by the diffuse form of Systemic sclerosis (SSc) to perform angiogenesis is a marker of the disease. We previously demonstrated that desmoglein-2 reduction is a major difference between (SSc)-microvascular endothelial cells (MVECs) and normal (N)-MVECs. Here we investigated the role of desmoglein-2 in human N-MVECs and SSc-MVECs angiogenesis.
Angiogenesis was studied by Matrigel invasion, capillary morphogenesis in vitro and Matrigel plug assay in vivo. Gene profiling was studied by Affymetrix technology and signal transduction by Western blotting. Colocalization was validated by immunoprecipitation and confocal microscopy. SiRNAs were used to validate the roles of specific molecules. We observed that desmoglein-2 co-localizes with integrin-beta8 in N-MVECs. This complex is required to signal through Rac, FAK, SMAD1/5 and MAP-kinases, promoting an angiogenic program. Inhibition of desmoglein-2 by DSG2-siRNA impaired actin stress fibres formation, capillary morphogenesis in vitro and angiogenesis in vivo. Transcriptome profiling after DSG2 inhibition revealed alterations of several genes involved in actin organization. siRNA inhibition of integrin-beta8 and RAC2 also resulted into capillary morphogenesis impairment in N-MVECs, due to reduced expression of the same actin-assembly genes that were down-regulated by DSG2 silencing. SSc-MVECs showed down-regulation of the same genes in DSG2-siRNA treated N-MVECs, suggesting that impairment of desmoglein-2/integrin-beta8 complex contributes to angiogenesis derangement in SSc. Transfection of DSG2 in SSc-MVEC partially restored their angiogenic properties in vitro.
We have shown that impairment of actin assembly as a result of desmoglein-2/integrin-beta8 complex formation is a major factor contributing to angiogenesis deregulation in Systemic sclerosis.
[Show abstract][Hide abstract] ABSTRACT: Objective
Clinical evidence suggests that the vascular abnormalities of systemic sclerosis (SSc) precede the onset of fibrosis, but molecular cues accounting for a possible vascular connection of SSc fibrosis have been elusive, although they have been searched for intensively. Since we had previously shown that connective tissue growth factor (CCN2), endowed with fibroblast-oriented activities, was overexpressed by endothelial cells (ECs) from SSc patients, we undertook this study to investigate its role and mechanisms in fibroblast activation. Methods
Normal fibroblasts were challenged with conditioned medium of normal microvascular ECs (MVECs) and MVECs obtained from SSc patients with the diffuse form of the disease. Fibroblast invasion was studied using the Boyden chamber Matrigel assay. Fibroblast activation was evaluated by Western blotting and immunofluorescence of α-smooth muscle actin (α-SMA), vimentin, and type I collagen. Matrix metalloproteinase (MMP) production was evaluated by zymography and reverse transcription–polymerase chain reaction. Signal transduction and activation of the small GTPases RhoA and Rac1 were studied by Western blotting. Inhibition of SSc MVEC conditioned medium–dependent fibroblast activation was obtained by anti-CCN2 antibodies and the transforming growth factor β (TGFβ) antagonist peptide p17. ResultsSSc MVEC CCN2 stimulated fibroblast activation and invasion. Such activities depended on CCN2-induced overexpression of TGFβ and its type I, II, and III receptors combined with overproduction of MMP-2 and MMP-9 gelatinases. All of these effects were reversed by the TGFβ antagonist peptide p17. Motility increase required Rac1 activation and RhoA inhibition and was inhibited by an MMP inhibitor. These features connoted a mesenchymal style of cell invasion. Since fibroblast activation also fostered overexpression of α-SMA, vimentin, and type I collagen, the CCN2-dependent increase in fibroblast activities recapitulated the characteristics of a mesenchymal-to-mesenchymal transition. ConclusionSSc MVECs recruit and activate dermal fibroblasts by induction of a CCN2/TGFβ-dependent mesenchymal-to-mesenchymal transition.
Full-text · Article · Jan 2013 · Arthritis & Rheumatology
[Show abstract][Hide abstract] ABSTRACT: TGFß overproduction in cancer cells is one of the main characteristics of late tumor progression being implicated in metastasis, tumor growth, angiogenesis and immune response. We investigated the therapeutic efficacy of anti-TGFß peptides in the control of angiogenesis elicited by conditional over-expression of TGFß.
We have inserted in human MCF7 mammary-cancer cells a mutated TGFß gene in a tetracycline-repressible vector to obtain conditional expression of mature TGFß upon transient transfection, evaluated the signaling pathways involved in TGFß-dependent endothelial cells activation and the efficacy of anti-TGFß peptides in the control of MCF7-TGFß-dependent angiogenesis.
TGFß over-expression induced in MCF7 several markers of the epithelial-to-mesenchymal transition. Conditioned-medium of TGFß-transfected MCF7 stimulated angiogenesis in vivo and in vitro by subsequent activation of SMAD2/3 and SMAD1/5 signaling in endothelial cells, as well as SMAD4 nuclear translocation, resulting in over-expression of the pro-angiogenic growth and differentiation factor-5 (GDF5). Inhibition or silencing of GDF5 in TGFß-stimulated EC resulted in impairment of GDF5 expression and of TGFß-dependent urokinase-plasminogen activator receptor (uPAR) overproduction, leading to angiogenesis impairment. Two different TGFß antagonist peptides inhibited all the angiogenesis-related properties elicited in EC by exogenous and conditionally-expressed TGFß in vivo and in vitro, including SMAD1/5 phosphorylation, SMAD4 nuclear translocation, GDF5 and uPAR overexpression. Antagonist peptides and anti-GDF5 antibodies efficiently inhibited in vitro and in vivo angiogenesis.
TGFß produced by breast cancer cells induces in endothelial cells expression of GDF5, which in turn stimulates angiogenesis both in vitro and in vivo. Angiogenesis activation is rapid and the involved mechanism is totally opposed to the old and controversial dogma about the AKL5/ALK1 balance. The GDF-dependent pro-angiogenic effects of TGFß are controlled by anti-TGFß peptides and anti-GDF5 antibodies, providing a basis to develop targeted clinical studies.
[Show abstract][Hide abstract] ABSTRACT: Endothelial urokinase-type plasminogen activator receptor (uPAR) is thought to provide a regulatory mechanism in angiogenesis. Here we studied the proangiogenic role of uPAR in endothelial colony-forming cells (ECFCs), a cell population identified in human umbilical blood that embodies all of the properties of an endothelial progenitor cell matched with a high proliferative rate. By using caveolae-disrupting agents and by caveolin-1 silencing, we have shown that the angiogenic properties of ECFCs depend on caveolae integrity and on the presence of full-length uPAR in such specialized membrane invaginations. Inhibition of uPAR expression by antisense oligonucleotides promoted caveolae disruption, suggesting that uPAR is an inducer of caveolae organization. Vascular endothelial growth factor (VEGF) promoted accumulation of uPAR in ECFC caveolae in its undegraded form. We also demonstrated that VEGF-dependent ERK phosphorylation required integrity of caveolae as well as caveolar uPAR expression. VEGF activity depends on inhibition of ECFC MMP12 production, which results in impairment of MMP12-dependent uPAR truncation. Further, MMP12 overexpression in ECFC inhibited vascularization in vitro and in vivo. Our data suggest that intratumor homing of ECFCs suitably engineered to overexpress MMP12 could have the chance to control uPAR-dependent activities required for tumor angiogenesis and malignant cells spreading.
[Show abstract][Hide abstract] ABSTRACT: Poly(ADP-Ribose) polymerase (PARP) activity has been demonstrated fundamental in many cellular processes, including DNA repair, cell proliferation and differentiation. In particular, PARP activity has been recently found to affect proliferation, migration, and tube formation of human umbilical vein endothelial cells. In recent times, PARP inhibitors have entered in clinical trials to potentiate cancer treatments by preventing DNA repair, but little is known about the effects performed by different drug concentrations on neoangiogenesis, an essential step in tumor growth.
Human umbilical vein endothelial cells were treated with 3 aminobenzamide (3ABA), a PARP inhibitor, and tested for several different cellular parameters.
Here we present in vitro evidence that a low concentration of 3ABA (50 μM), stimulates angiogenesis by decreasing fibrinolytic activity, carried out by urokinase-type plasminogen activator (uPA), and by enhancing matrix metalloprotease-2 (MMP-2) gelatinolytic activity, in fibroblast growth factor-2-stimulated endothelial cells. These unbalanced pathways modify in vitro angiogenic steps, inhibiting chemoinvasion and stimulating tubulogenic activity.
Our results suggest that the proangiogenic effect of low concentrations of 3ABA alerts on the efficacy of PARP inhibitors to potentiate anticancer therapy. Moreover, they indicate that endothelial chemoinvasion and tubulogenesis depend on distinct proteolytic pathways.
[Show abstract][Hide abstract] ABSTRACT: The effect on angiogenesis of (-)-alpha-bisabolol [(-)-6-methyl-2-(4-methyl-3-cyclohexen-1-yl)-5-hepten-2-ol] (1), a widely distributed plant sesquiterpene alcohol, was investigated for the first time. Human endothelial cells treated with 1 were analyzed for their ability to differentiate and organize in microvessels and for their sensitivity to this compound in terms of cytotoxicity and cell growth inhibition. Within 24 h of the treatment with 5 microM 1, cells underwent massive death. Apoptosis induction was responsible for cytotoxicity triggered by 1 as revealed by the release of cytochrome c from the mitochondria, reduction of the Bcl-2/Bax ratio, and caspase 3 activation. At a lower, non-apoptotic concentration (0.25 microM), 1 showed a differentiating effect resulting in growth inhibition, invasiveness reduction, and tubule stabilization.
No preview · Article · Apr 2010 · Journal of Natural Products
[Show abstract][Hide abstract] ABSTRACT: Cannabinoids have been recently proposed as a new family of potential antitumor agents. The present study was undertaken to investigate the expression of the two cannabinoid receptors, CB1 and CB2, in colorectal cancer and to provide new insight into the molecular pathways underlying the apoptotic activity induced by their activation.
Cannabinoid receptor expression was investigated in both human cancer specimens and in the DLD-1 and HT29 colon cancer cell lines. The effects of the CB1 agonist arachinodyl-2'-chloroethylamide and the CB2 agonist N-cyclopentyl-7-methyl-1-(2-morpholin-4-ylethyl)-1,8-naphthyridin-4(1H)-on-3-carboxamide (CB13) on tumor cell apoptosis and ceramide and tumor necrosis factor (TNF)-alpha production were evaluated. The knockdown of TNF-alpha mRNA was obtained with the use of selective small interfering RNA.
We show that the CB1 receptor was mainly expressed in human normal colonic epithelium whereas tumor tissue was strongly positive for the CB2 receptor. The activation of the CB1 and, more efficiently, of the CB2 receptors induced apoptosis and increased ceramide levels in the DLD-1 and HT29 cells. Apoptosis was prevented by the pharmacologic inhibition of ceramide de novo synthesis. The CB2 agonist CB13 also reduced the growth of DLD-1 cells in a mouse model of colon cancer. The knockdown of TNF-alpha mRNA abrogated the ceramide increase and, therefore, the apoptotic effect induced by cannabinoid receptor activation.
The present study shows that either CB1 or CB2 receptor activation induces apoptosis through ceramide de novo synthesis in colon cancer cells. Our data unveiled, for the first time, that TNF-alpha acts as a link between cannabinoid receptor activation and ceramide production.
Full-text · Article · Jan 2009 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: Cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LOX) are key enzymes involved in arachidonic acid metabolism. Their products, prostaglandins and leukotrienes, are involved in colorectal tumor development. We aimed at evaluating whether combined blocking of the COX-2 and 5-LOX pathways might have additive antitumor effects in colorectal cancer. The expression/activity of COX-2 and 5-LOX were assessed in 24 human colorectal cancer specimens. The effects of the COX-2 inhibitor celecoxib and the 5-LOX inhibitor MK886 on prostaglandin E(2) and cysteinyl leukotriene production, tumor cell proliferation, cell apoptosis, and Bcl-2/Bax expression were evaluated in the Caco-2 and HT29 colon cancer cells. We also investigated the effect of the enzymatic inhibition on mitochondrial membrane depolarization, one of the most important mechanisms involved in ceramide-induced apoptosis. Up-regulation of the COX-2 and 5-LOX pathways was found in the tumor tissue in comparison with normal colon mucosa. Inhibition of either COX-2 or 5-LOX alone resulted in activation of the other pathway in colon cancer cells. Combined treatment with 10 micromol/L celecoxib and MK886 could prevent this activation and had additive effects on inhibiting tumor cell proliferation, inducing cell apoptosis, decreasing Bcl-2 expression, increasing Bax expression, and determining mitochondrial depolarization in comparison with treatment with either inhibitor alone. The administration of the ceramide synthase inhibitor fumonisin B1 could prevent some of these antineoplastic effects. In conclusion, our study showed that inhibition of 5-LOX by MK886 could augment the antitumor activity of celecoxib in human colorectal cancer.
Full-text · Article · Dec 2006 · Molecular Cancer Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Nitric oxide (NO) is a diatomic free radical molecule that has been implicated in tumour angiogenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the mechanism underlying the effect of NO on tumour spread remains largely unknown. Tumour lymphangiogenesis has recently received considerable attention and there is increasing evidence that it is relevant for metastasis to lymph nodes in HNSCC. Here, we study the correlation between inducible NOS synthase (iNOS) activity and lymphangiogenesis in a series of 60 HNSCCs and the possible involvement of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C. HNSCC presenting with lymph node metastasis had a significantly higher lymphatic vessel density in both the tumour mass and the peritumour area (p = 0.006 and p = 0.001, respectively). Similarly, tumours with lymph node metastasis showed greater lymphatic vessel area than tumours with no lymph node involvement (p = 0.001 for intratumour lymphatics and p < 0.001 for peritumour lymphatics). iNOS activity measured in specimens from the tumour periphery correlated strongly with both lymphatic vessel density and lymphatic vessel area (p = 0.01, rs = 0.45 and p < 0.001, rs = 0.725, respectively). Conversely, these correlations were not observed in specimens from the tumour core. In addition, VEGF-C mRNA expression was significantly elevated in tumours with high iNOS activity (p = 0.008, rs = 0.563), and VEGF-C expression correlated positively with the presence of lymph node metastases (p = 0.03). In vitro, in the A431 human squamous carcinoma cell line, exogenous and endogenous stimulation of the iNOS pathway led to up-regulation of VEGF-C, which was blocked by the NOS inhibitor L-NNA. Taken together, our results indicate that iNOS activity may promote lymphangiogenesis and spread to lymph nodes in HNSCC, with the possible involvement of VEGF-C.
No preview · Article · Feb 2006 · The Journal of Pathology
[Show abstract][Hide abstract] ABSTRACT: Activity of histidine decarboxylase, the key enzyme in the synthesis of histamine, has been shown to be increased in several types of human tumors. We attempted to establish whether the possible involvement of histidine decarboxylase and histamine in colorectal carcinogenesis might be mediated by the activation of the cyclooxygenase-2 (COX-2) pathway.
Expression/activity of histidine decarboxylase, histamine content, and prostaglandin E2 (PGE2) production were analyzed in 33 colorectal cancer samples and in the HT29, Caco-2, and HCT116 colon cancer cell lines. The effects of histamine, celecoxib, and H1, H2, and H4 receptor antagonists on COX-2 expression/activity, cell proliferation, and vascular endothelial growth factor (VEGF) production were assessed in the three colon cancer lines that showed different constitutive COX-2 expression.
We showed the up-regulation of histidine decarboxylase protein expression and activity in the tumor specimens when compared with normal colonic mucosa. Histidine decarboxylase activity and histamine content were also significantly higher in metastatic tumors than in nonmetastatic ones. These variables significantly correlated with tumor PGE(2) production. The administration of histamine increased COX-2 expression/activity, cell proliferation, and VEGF production in the COX-2-positive HT29 and Caco-2 cells. Treatment with either H2/H4 receptor antagonists or celecoxib prevented these effects. Histamine had no effect on both the COX-2 pathway and VEGF production in the COX-2-negative HCT116 cells.
Our data showed that histamine exerts both a proproliferative and a proangiogenic effect via H2/H4 receptor activation. These effects are likely to be mediated by increasing COX-2-related PGE2 production in COX-2-expressing colon cancer cells.
Full-text · Article · Nov 2005 · Clinical Cancer Research
[Show abstract][Hide abstract] ABSTRACT: Satellite cells are quiescent cells that can be induced to proliferate by a variety of stimuli such as injury and exercise, providing in this way a source of new myoblasts that repopulate the damaged muscle. It is well known that, as senescence progresses, the muscle regenerative potential progressively diminishes, but the molecular mechanisms underlying this process are not yet completely defined. Many growth factors, including Platelet Derived Growth Factor (PDGF-BB)*, have been associated to satellite cells activation, acting as potent mitogenic agents for these cells. The aim of this study is to explore if the diminished response of senescent myoblasts to growth stimuli could be due to the inability to receive and transduce hormonal signals. Herein, we demonstrate that that although PDGF-r expression is down-regulated during senescence, the receptor is fully able to be phosphorylated and to transmit the signal. Although senescent myoblasts display increased level of phosphotyrosine phosphatases (PTPs), neither the PDGF receptor (PDGF-r) phosphorylation level nor the citosolic signal transduction machinery is affected. Indeed, we demonstrated that senescent human myoblasts are able to initiate a proper mitogenic signalling cascade, since the activation of mitogen-activated protein kinases (MAPK) and phosphatydil inositole 3 kinase (PI-3K) pathways is similar in young and senescent cells. Our data underline that, despite a conserved capability to activate PDGF-r after agonist stimulation and a functional signal transduction machinery, the mitogenic signal initiated by growth factors in senescent cells does not lead to cell division, being unable to overcome the cell cycle block, likely caused by the accumulation of the inhibitor p21WAF1.
No preview · Article · Jan 2005 · The Italian journal of biochemistry
[Show abstract][Hide abstract] ABSTRACT: Cell differentiation is often associated with a block in the cell cycle. Growth factor signaling has been reported to be impaired in differentiated cells, due to the withdrawal of growth factors or to transcriptional down-regulation of their receptors. Our proposal is that the down regulation of growth factor signaling may be achieved through an alternative pathway: the decrease of growth factor receptor activation and the ensuing inhibition of intracellular pathways leading the cell to division. Here we report that platelet-derived growth factor receptor (PDGFr) signaling is down-regulated during muscle differentiation, although its expression level remains unchanged. PDGFr signaling inhibition is achieved through a decrease in the receptor tyrosine phosphorylation level, in particular of Tyr716, Tyr751, Tyr857 and Tyr1021, leading to down-regulation of intracellular signaling pathways. Furthermore, during myogenesis, the expression level of several phosphotyrosine phosphatases (PTPs) increases and most of them shift toward the reduced/activated state. We propose a causal link between the down-regulation of PDGFr tyrosine phosphorylation and the increases in PTP specific activity during myogenesis.
Full-text · Article · Jan 2004 · Cellular and Molecular Life Sciences CMLS
[Show abstract][Hide abstract] ABSTRACT: Protein tyrosine phosphorylation is one of the earliest signaling events detected in response to lymphocyte function-associated antigen-1 (LFA-1) engagement during lymphocyte adhesion. In particular, the focal adhesion kinase p125FAK, involved in the modulation and rearrangement of the actin cytoskeleton, seems to be a crucial mediator of LFA-1 signaling. Herein, we investigate the role of a FAK tyrosine phosphatase, namely low molecular weight phosphotyrosine phosphatase (LMW-PTP), in the modulation of LFA-1-mediated T cell adhesion. Overexpression of LMW-PTP in Jurkat cells revealed an impairment of LFA-1-dependent cell-cell adhesion upon T cell receptor (TCR) stimulation. Moreover, in these conditions LMW-PTP causes FAK dephosphorylation, thus preventing the activation of FAK downstream pathways. Our results also demonstrated that, upon antigen stimulation, LMW-PTP-dependent FAK inhibition is associated to a strong reduction of LFA-1 and TCR co-clustering toward a single region of T cell surface, thus causing an impairment of receptor activity by preventing changes in their avidity state. Because co-localization of both LFA-1 and TCR is an essential event during encounters of T cells with antigen-presenting cells and immunological synapse (IS) formation, we suggest an intriguing role of LMW-PTP in IS establishment and stabilization through the negative control of FAK activity and, in turn, of cell surface receptor redistribution.
Full-text · Article · Oct 2003 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: The goal of this study was to analyze the correlation between inducible nitric oxide synthase (iNOS) and COX-2 activities and p53 gene status in head and neck squamous cell carcinomas (HNSCCs) in vivo and in vitro. In a series of 43 HNSCCs we observed an up-regulation of both iNOS and COX-2 pathways in tumor tissues and both activities were correlated each other (rs = 0.612 and P = 0.0002). We also found that p53-mutated HNSCCs (25 cases, 58.1%) showed higher levels of iNOS activity and cGMP in comparison with wild-type p53 tumors (18 cases, 41.9%) (P = 0.0005 and P = 0.01), as well as higher iNOS immunohistochemical expression (P = 0.03). Analogously, higher PgE2 levels were documented in p53-mutated HNSCCs when compared with wild-type p53 tumors (P = 0.015) and COX-2 protein expression was higher in p53-mutated HNSCCs (P = 0.007). A431 cancer cells expressing a p53 temperature-sensitive mutant showed an approximately 1.9- and 2.6-fold decrease in spontaneous NO(2-)/NO(3-) and PgE2 synthesis at permissive temperature, respectively, when compared with the same cells at nonpermissive temperature (P <or= 0.001). Basal levels of iNOS and COX-2 proteins and mRNAs were markedly suppressed by restoration of p53 activity. Our results indicate that p53 gene mutation(s) may be responsible for iNOS and COX-2 up-regulation frequently observed in HNSCCs and suggest that restoration of wild-type p53 expression may interfere with tumor growth by inhibiting iNOS and COX-2 pathways.
Full-text · Article · Aug 2003 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: We investigated the interactions between inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) pathways in head and neck squamous cell carcinomas (HNSCCs) and in two carcinoma cell lines. HNSCCs showed an up-regulation of both pathways which were strongly correlated with each other (p=0.02) and with tumor vascularization (p=0.0001 and p=0.008, respectively). In carcinoma cells, Escherichia coli lipopolysaccharide (LPS) and EGF treatment up-regulated both pathways. NOS inhibitor N(G)-monomethyl-L-arginine methyl ester (L-NAME) inhibited this up-regulation. LPS or EGF induced iNOS expression that was not altered by NOS or COX-2 inhibitors. Conversely, LPS or EGF promoted COX-2 expression that was decreased by L-NAME. The NO donor S-nitroso-acetyl-penicillamine (SNAP) up-regulated COX-2 pathway and this effect was reduced by the guanylate cyclase inhibitor methylene blue. Thus, in squamous carcinoma cells, NO increases the activity of COX-2 pathway and this effect is probably mediated by endocellular cGMP level, with potential implications on tumor growth, angiogenesis, and therapy.
Full-text · Article · Jan 2003 · Biochemical and Biophysical Research Communications