Abnormal PTEN expression in portal hypertensive gastric mucosa: a key to impaired PI 3-kinase/Akt activation and delayed injury healing?

RICK regulates the odontogenic differentiation of dental pulp stem cells through activation of TNF-α via the ERK and not through NF-κB signaling pathway

Dental pulp stem cells (DPSCs) are capable of both self-renewal and multilineage differentiation, which play a positive role in dentinogenesis. Studies have shown that tumor necrosis factor-α (TNF-α) is involved in the differentiation of DPSCs under pro-inflammatory stimuli, but the mechanism of action of TNF-α is unknown. Rip-like interacting caspase-like apoptosis-regulatory protein kinase (RICK) is a biomarker of an early inflammatory response that plays a key role in modulating cell differentiation, but the role of RICK in DPSCs is still unclear. In this study, we identified that RICK regulates TNF-α-mediated odontogenic differentiation of DPSCs via the ERK signaling pathway. The expression of the biomarkers of odontogenic differentiation dental matrix protein-1 (DMP-1), dentin sialophosphoprotein (DSPP), biomarkers of odontogenic differentiation, increased in low concentration (1-10 ng/ml) of TNF-α and decreased in high concentration (50-100 ng/ml). Odontogenic differentiation increased over time in the odontogenic differentiation medium. In the presence of 10 ng/L TNF-α, the expression of RICK increased gradually over time, along with odontogenic differentiation. Genetic silencing of RICK expression reduced the expression of odontogenic markers DMP-1 and DSPP. The ERK, but not the NF-κB signaling pathway, was activated during the odontogenic differentiation of DPSCs. ERK signaling modulators decreased when RICK expression was inhibited. PD98059, an ERK inhibitor, blocked the odontogenic differentiation of DPSCs induced by TNF-α. These results provide a further theoretical and experimental basis for the potential use of RICK in targeted therapy for dentin regeneration.

Catalpol suppresses osteoclastogenesis and attenuates osteoclast-derived bone resorption by modulating PTEN activity

Excessive activation of osteoclast activity is responsible for many bone diseases, such as osteoporosis, rheumatoid arthritis, periprosthetic osteolysis, and periodontitis. Natural compounds that inhibit osteoclast formation and/or function have therapeutic potential for treating these diseases. Catalpol, a bioactive iridoid extracted from a traditional herbal medicine Rehmannia glutinosa, exhibits various pharmacological properties, including anti-inflammatory, antioxidant, antidiabetic, and antitumor effects. However, its effects on osteoclast formation and function remain unknown. In the present study, we showed that catalpol inhibited receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast formation and bone resorption, as well as the expression of osteoclast-related marker genes. The investigation of molecular mechanisms showed that catalpol upregulated phosphatase and tensin homolog (PTEN) activity by reducing its ubiquitination and degradation, subsequently suppressing RANKL-induced NF-κB and AKT signaling pathways, leading to an inhibition on NFATc1 induction. Furthermore, catalpol protected mice against inflammation- and ovariectomy-induced bone loss by inhibiting osteoclast activity in vivo. These results suggest that catalpol might be developed as a promising candidate for treating osteoclast-related bone diseases.

PTEN Inhibition in Human Disease Therapy

The tumor suppressor PTEN is a major homeostatic regulator, by virtue of its lipid phosphatase activity against phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3], which downregulates the PI3K/AKT/mTOR prosurvival signaling, as well as by its protein phosphatase activity towards specific protein targets. PTEN catalytic activity is crucial to control cell growth under physiologic and pathologic situations, and it impacts not only in preventing tumor cell survival and proliferation, but also in restraining several cellular regeneration processes, such as those associated with nerve injury recovery, cardiac ischemia, or wound healing. In these conditions, inhibition of PTEN catalysis is being explored as a potentially beneficial therapeutic intervention. Here, an overview of human diseases and conditions in which PTEN inhibition could be beneficial is presented, together with an update on the current status of specific small molecule inhibitors of PTEN enzymatic activity, their use in experimental models, and their limitations as research or therapeutic drugs.

Downregulation of dickkopf-1 enhances the proliferation and osteogenic potential of fibroblasts isolated from ankylosing spondylitis patients via the Wnt/β-catenin signaling pathway in vitro

BACKGROUND

Heterotopic ossification of the entheses is one of the most distinctive features in ankylosing spondylitis (AS). Fibroblasts are potential target cells for heterotopic ossification. The Wnt/β-catenin pathway and its inhibitor dickkopf-1 (DKK-1) regulate bone formation. DKK-1 expression in human AS tissues has not been documented.

OBJECTIVE

The purpose of the current study was to investigate the expression of DKK-1 in AS tissues and to elucidate its role in fibroblasts proliferation and osteogenesis in AS.

METHODS

DKK-1 expression was assessed by western blotting, real time-polymerase chain reaction (RT-PCR), and immunohistochemistry analysis of hip synovial tissues obtained from AS and control patients. Fibroblasts were isolated, cultured, and transfected with lentiviral vectors for overexpressing human DKK-1 or an shRNA for silencing DKK-1. MTS [(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl) 2-(4-sulfophenyl)-2H-tetrazolium] and a 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay were used to detect AS fibroblasts proliferation after transfection. The expression levels of β-catenin, phosphorylated β-catenin, c-Myc, cyclin D1, and the osteogenesis markers alkaline phosphatase (ALP), osteocalcin (OCN), and Runt-related transcription factor 2 (Runx2) were then examined by western blot analysis. Alizarin red staining (ARS) was also used to observe biomineralization activity.

RESULTS

DKK-1 was downregulated in hip synovial tissues from AS patients compared to that observed in controls. AS fibroblasts exhibited excessive proliferation, a higher growth rate, and a decreased apoptotic rate. EdU assay demonstrated that DKK-1 suppressed the growth of AS fibroblasts. Downregulation of DKK-1 decreased the phosphorylation of β-catenin and upregulated the expression of β-catenin, c-Myc, cyclin D1, and osteogenesis markers. Overexpression of DKK-1 had the opposite effect, resulting in the inhibition of the Wnt/β-catenin pathway. ARS showed an increase in biomineralization activity after the inhibition of DKK-1.

CONCLUSIONS

AS fibroblasts are characterized by an imbalance between proliferation and apoptosis. DKK-1 may play a role in switching to new bone formation in AS progression.

Telomerase activity promotes osteoblast differentiation by modulating IGF-signaling pathway

The contribution of deficient telomerase activity to age-related decline in osteoblast functions and bone formation is poorly studied. We have previously demonstrated that telomerase over-expression led to enhanced osteoblast differentiation of human bone marrow skeletal (stromal) stem cells (hMSC) in vitro and in vivo. Here, we investigated the signaling pathways underlying the regulatory functions of telomerase in osteoblastic cells. Comparative microarray analysis and Western blot analysis of telomerase-over expressing hMSC (hMSC-TERT) versus primary hMSC revealed significant up-regulation of several components of insulin-like growth factor (IGF) signaling. Specifically, a significant increase in IGF-induced AKT phosphorylation and alkaline phosphatase (ALP) activity were observed in hMSC-TERT. Enhanced ALP activity was reduced in presence of IGF1 receptor inhibitor: picropodophyllin. In addition, telomerase deficiency caused significant reduction in IGF signaling proteins in osteoblastic cells cultured from telomerase deficient mice (Terc(-/-)). The low bone mass exhibited by Terc(-/-) mice was associated with significant reduction in serum levels of IGF1 and IGFBP3 as well as reduced skeletal mRNA expression of Igf1, Igf2, Igf2r, Igfbp5 and Igfbp6. IGF1-induced osteoblast differentiation was also impaired in Terc(-/-) MSC. In conclusion, our data demonstrate that impaired IGF/AKT signaling contributes to the observed decreased bone mass and bone formation exhibited by telomerase deficient osteoblastic cells.

Angiogenesis in gastric mucosa: an important component of gastric erosion and ulcer healing and its impairment in aging

Angiogenesis (also referred to as neovascularization-formation of new blood vessels from existing vessels) is a fundamental process essential for healing of tissue injury and ulcers because regeneration of blood microvessels is a critical requirement for oxygen and nutrient delivery to the healing site. This review article updates the current views on angiogenesis in gastric mucosa following injury and during ulcer healing, its sequential events, the underlying mechanisms, and the impairment of angiogenesis in aging gastric mucosa. We focus on the time sequence and ultrastructural features of angiogenesis, hypoxia as a trigger, role of vascular endothelial growth factor signaling (VEGF), serum response factor, Cox2 and prostaglandins, nitric oxide, and importin. Recent reports indicate that gastric mucosa of aging humans and experimental animals exhibits increased susceptibility to injury and delayed healing. Gastric mucosa of aging rats has increased susceptibility to injury by a variety of damaging agents such as ethanol, aspirin, and other non-steroidal anti-inflammatory drugs because of structural and functional abnormalities including: reduced gastric mucosal blood flow, hypoxia, reduced expression of vascular endothelial growth factor and survivin, and increased expression of early growth response protein 1 (egr-1) and phosphatase and tensin homolog (PTEN). Until recently, postnatal neovascularization was assumed to occur solely through angiogenesis sprouting of endothelial cells and formation of new blood vessels from pre-existing blood vessels. New studies in the last decade have challenged this paradigm and indicate that in some tissues, including gastric mucosa, the homing of bone marrow-derived endothelial progenitor cells to the site of injury can also contribute to neovascularization by a process termed vasculogenesis.

Increased mortality with peptic ulcer bleeding in patients with both compensated and decompensated cirrhosis

BACKGROUND

Cirrhosis is associated with worse outcomes in peptic ulcer bleeding (PUB). There are no population-based studies from the United States on the impact of cirrhosis on PUB outcomes.

OBJECTIVE

To investigate the impact of cirrhosis on outcomes of patients with PUB.

DESIGN

Cross-sectional study.

SETTING

Nationwide Inpatient Sample 2009.

PATIENTS

International Classification of Diseases, the 9th revision, codes were used to identify patients with PUB and cirrhosis. The control group was patients with PUB without cirrhosis.

MAIN OUTCOME MEASUREMENTS

In-hospital mortality, length of stay, and hospitalization costs.

RESULTS

A total of 96,887 discharges with PUB as a diagnosis were identified-3574 with PUB and cirrhosis and 93,313 with PUB alone without cirrhosis. Mortality of PUB with concomitant cirrhosis was higher than in the control group without cirrhosis (5.5% vs 2%; P = .01); decompensated cirrhosis had higher mortality than did compensated cirrhosis (6.6% vs 3.9%; P = .01). In multivariate analysis, the presence of cirrhosis independently increased mortality (adjusted odds ratio (aOR) 3.3; 95% confidence interval [CI], 2.2-4.9). Stratified analysis showed that decompensated cirrhosis (aOR 4.4; 95% CI, 2.6-7.3) had higher mortality than compensated cirrhosis (aOR 1.9; 95% CI, 1.04-3.6). There was no difference in the proportion of patients who underwent endoscopy within 24 hours (51.9% vs 51.1%; P = .68) between those with cirrhosis and controls. Patients with cirrhosis received less surgical intervention (aOR 0.8; 95% CI, 0.6-0.9) compared with controls. Hospitalization costs also were increased in patients with decompensated cirrhosis.

LIMITATIONS

Administrative data set.

CONCLUSION

Both decompensated and compensated cirrhosis are associated with increased mortality in patients with PUB.

Long-term risk of recurrent peptic ulcer bleeding in patients with liver cirrhosis: a 10-year nationwide cohort study

Peptic ulcer bleeding leads to substantial morbidity and mortality in patients with liver cirrhosis, but their long-term risk of recurrent bleeding remains elusive. This nationwide cohort study aimed to elucidate the association between cirrhosis and recurrent peptic ulcer bleeding by analyzing the Taiwan National Health Insurance Research Database. We enrolled a total of 9,711 patients who had cirrhosis with clinical complications of portal hypertension from all patients (n = 271,030) hospitalized for peptic ulcer bleeding between January 1997 and December 2006, along with 38,844 controls who were matched at a 1:4 proportion for age, sex, and antisecretory agents. We accounted for death as the competing cause of risk when calculating the cumulative incidences and hazard ratios of recurrent bleeding during the 10-year study period. Overall, patients with cirrhosis had a significantly higher death-adjusted rebleeding rate compared with controls (1 year, 14.4% versus 11.3%; 5 years, 26.1% versus 22.5%; 10 years, 28.4% versus 27.1%; P < 0.001). The modified Cox proportional hazard model verified that cirrhosis was significantly associated with peptic ulcer rebleeding (adjusted hazard ratio, 3.19; 95% confidence interval, 2.62-3.88), but also uncovered a seemingly paradoxical interaction between cirrhosis and age. Multivariate stratified analysis further revealed that the rebleeding risk after adjustment for death diminished with age in patients with cirrhosis, whose risk of death far exceeded that of rebleeding when they grew old.

CONCLUSION

Liver cirrhosis is associated with long-term risk of recurrent peptic ulcer bleeding, although the risk declines with age because of death being the competing cause. Effective therapy should be sought to reduce this excessive risk in these critically ill patients, particularly for those at younger age with longer life expectancy.

PTEN inhibition improves wound healing in lung epithelia through changes in cellular mechanics that enhance migration

The phosphoinositide-3 kinase/Akt pathway is a vital survival axis in lung epithelia. We previously reported that inhibition of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a major suppressor of this pathway, results in enhanced wound repair following injury. However, the precise cellular and biomechanical mechanisms responsible for increased wound repair during PTEN inhibition are not yet well established. Using primary human lung epithelia and a related lung epithelial cell line, we first determined whether changes in migration or proliferation account for wound closure. Strikingly, we observed that cell migration accounts for the majority of wound recovery following PTEN inhibition in conjunction with activation of the Akt and ERK signaling pathways. We then used fluorescence and atomic force microscopy to investigate how PTEN inhibition alters the cytoskeletal and mechanical properties of the epithelial cell. PTEN inhibition did not significantly alter cytoskeletal structure but did result in large spatial variations in cell stiffness and in particular a decrease in cell stiffness near the wound edge. Biomechanical changes, as well as migration rates, were mediated by both the Akt and ERK pathways. Our results indicate that PTEN inhibition rapidly alters biochemical signaling events that in turn provoke alterations in biomechanical properties that enhance cell migration. Specifically, the reduced stiffness of PTEN-inhibited cells promotes larger deformations, resulting in a more migratory phenotype. We therefore conclude that increased wound closure consequent to PTEN inhibition occurs through enhancement of cell migration that is due to specific changes in the biomechanical properties of the cell.

Abnormal elevated PTEN expression in the mouse antrum of a model of GIST Kit(K641E/K641E)

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Approximately 85% of GISTs harbor activating mutations of the KIT or PDGFRA receptor tyrosine kinases. PTEN and SHIP2 are major phosphatases that dephosphorylate PI(3,4,5)P(3), one of the intracellular signal pathways downstream of KIT. PTEN is an important tumor suppressor, whereas the involvement of SHIP2 in cancer has been proposed based essentially on cell line studies. We have used a mouse model of GIST, i.e. Kit(K641E) knock-in mice, resulting in the substitution of a Lys by Glu at position 641 of Kit. In homozygous Kit(K641E) mice, PTEN-immunoreactivity (ir) in antrum was found in the hyperplastic Kit-ir layer. The same localization was found for SHIP2. Western blot analysis in antrum showed a large increase in PTEN expression in Kit(K641E) homozygous mice as compared to wild type. In contrast, SHIP2 expression was not affected between the two genotypes. Erk1, but not PKB, phosphorylation appears to be upregulated in Kit(K641E) homozygous mice. In the human GIST882 imatinib sensitive cell line, both PTEN and SHIP2 were expressed and showed, in part, a nuclear localization. The upregulation of PTEN in antrum in Kit(K641E) mice might serve as a feedback mechanism to limit PI 3-kinase activation downstream of Kit in a context of oncogenic mutation.

Inhibition of the phosphatase PTEN protects mice against oleic acid-induced acute lung injury

BACKGROUND AND PURPOSE

Injury to the lung parenchyma is a constitutional feature shared by many lung diseases. The protein, phosphatase and tensin homologue deleted on chromosome Ten (PTEN) is a major suppressor of phosphoinositide-3 kinase/Akt signalling, a vital survival pathway in lung parenchymal cells. Based on this, we hypothesized that PTEN inhibition in vivo would enhance cell tolerance to stress thereby preventing acute lung injury.

EXPERIMENTAL APPROACH

We evaluated the ability of a PTEN inhibitor, potassium bisperoxo (1,10-phenanthroline) oxovanadate [bpV(phen)], to prevent acute lung injury induced by oleic acid (OA) in adult C57BL/6 mice. Lung assessments included bronchoalveolar lavage, tissue morphology, immunostaining for markers of cell death, cell identity, phospho-Akt and phospho-ERK levels and oximetry.

KEY RESULTS

OA induced acute lung injury in a dose- and time-dependent manner. No injury was observed in the vehicle control or bpV(phen) treatment groups. PTEN inhibition by bpV(phen) increased lung tissue levels of phospho-Akt and ERK and but not focal adhesion kinase. This occurred in conjunction with a statistically significant reduction in protein content, lactate dehydrogenase, as well as tumour necrosis factor-alpha and chemokines in bronchoalveolar lavage fluid when compared with OA treatment alone. The incidence of alveolar lesions, consistent with acute lung injury, and terminal uridine deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)-positive cells was also significantly reduced. Importantly, PTEN suppression maintained pulmonary function.

CONCLUSIONS AND IMPLICATIONS

Treatment with bpV(phen) significantly reduced the severity of acute lung injury in mice indicating that additional investigation is warranted to understand the important role that this phosphatase may play in the lung.

Aging gastropathy-novel mechanisms: hypoxia, up-regulation of multifunctional phosphatase PTEN, and proapoptotic factors

BACKGROUND & AIMS

Aging gastric mucosa has impaired mucosal defense and increased susceptibility to injury. Our aims were to determine the mechanisms responsible for above abnormalities.

METHODS

We used Fisher F-344 rats, 3 and 24 months of age. We measured gastric mucosal blood flow; visualized mucosal hypoxia; examined expression of early growth response-1 transcription factor and phosphatase and tensin homologue deleted on chromosome 10 (PTEN); assessed apoptosis; and determined expression of caspase-3, caspase-9, and survivin. We also examined susceptibility of gastric mucosa of young and aging rats to ethanol injury and whether down-regulation of PTEN affects susceptibility of aging gastric mucosa to injury. To determine human relevance, we examined expression of PTEN and survivin in human gastric specimens of young and aging individuals.

RESULTS

Gastric mucosa of aging (vs young) rats has a 60% reduction in mucosal blood flow; prominent hypoxia; and increased early growth response-1 transcription factor and PTEN messenger RNAs, and proteins. It also has increased expression of proapoptotic proteins caspase-3 and capase-9, reduced survivin, and a 6-fold increased apoptosis vs mucosa of young rats. Ethanol-induced gastric mucosal injury in aging (vs young) rats was significantly increased. The down-regulation of PTEN in gastric mucosa of aging rats completely reversed its increased susceptibility to ethanol injury. In aging human gastric mucosa, PTEN expression was significantly increased, whereas survivin was significantly reduced.

CONCLUSIONS

(1) Gastric mucosa of aging rats has significantly reduced blood flow, tissue hypoxia, activation of Egr-1, PTEN; increased caspases; and reduced survivin. (2) These changes increase susceptibility of aging gastric mucosa to injury.

PTEN: a promising pharmacological target to enhance epithelial wound healing

PI3Ks (phosphoinositide-3 kinases) produce PIP3 (phosphatidylinositol(3,4,5)-trisphosphate) which mediates signals for cell survival and proliferation. The tumour suppressor PTEN (phosphatase and tensin homologue) dephosphorylates PIP3 and is a key negative regulator of PI3K signalling. Recent research highlighted important roles for PI3K/PTEN in cell polarization and directional cell migration, pointing to a significant role for PTEN in wound healing where spatially organized tissue growth is essential. Lai et al. (in this issue of British Journal of Pharmacology) have moved a step closer in utilizing PTEN for wound healing through pharmacological inhibition. Two vanadium derivative inhibitors targeting PTEN significantly elevated the level of phosphorylated Akt (protein kinase B) and nearly doubled the wound healing rate in monolayer cultures of lung and airway epithelial cells. Damage to airway and lung epithelia underlies a wide spectrum of significant clinical conditions. With further experiments, this promising approach may find potential clinical use in situations where enhanced wound healing of pulmonary and other epithelia is important.

Identification of functional domains in AKT responsible for distinct roles of AKT isoforms in pressure-stimulated cancer cell adhesion

Cell adhesion is a critical step in cancer metastasis, activated by extracellular forces such as pressure and shear. Reducing AKT1, but not AKT2, ablates the increase in cancer cell adhesion associated with 15 mm Hg increased extracellular pressure. To identify the determinants of this AKT isoform specificity, we exchanged the pleckstrin homology (PH) domains and/or hinge regions of AKT1 and AKT2. Wild type isoforms or these chimeras were overexpressed in Caco-2 cells in the absence or presence of isoform-specific siRNA to suppress endogenous AKT1. Pressure-induced AKT translocation and phosphorylation to the membrane were compared, along with the stimulation of cell adhesion by pressure. Pressure stimulated translocation of AKT1, but not AKT2 to the plasma membrane. Among our chimeras, only the chimeric AKT2 (chimera2), in which both the AKT2 PH domain and hinge region had been replaced by those of AKT1, translocated to the membrane in response to pressure. Similarly, only chimera2 rescued the function of AKT1 in mediating pressure-stimulated adhesion after endogenous AKT1 had been reduced. Pressure also promoted phosphorylation of AKT1 but not AKT2, and expression of a nonphosphorylatable double point mutant prevented pressure-stimulated adhesion. Among the chimeras, pressure promoted only chimera2 phosphorylation. These results identify the AKT1 PH domain and hinge region as functional domains which jointly permit AKT1 translocation and phosphorylation in response to extracellular pressure and distinguish determine the specificity of AKT1 in mediating the effects of extracellular pressure on cancer cell adhesion. These may be useful targets for interventions to inhibit metastasis.

Epidermal growth factor receptor-dependent PI3K-activation promotes restitution of wounded human gastric epithelial monolayers

Restitution is a crucial event during the healing of superficial injury of the gastric mucosa involving epithelial cell sheet movement into the damaged area. We demonstrated that growth factors promote the restitution of human gastric epithelial cells. However, the intracellular signaling pathways that transmit extracellular cues as well as regulate basal and growth factor-stimulated gastric epithelial cell migration are still unclear. Herein, confluent human gastric epithelial cell monolayers (HGE-17) or primary cultures of gastric epithelial cells were wounded with a razor blade and the migration response was analyzed in presence or absence of TGFalpha or of pharmacological inhibitors of signaling proteins. Kinase activation profile analysis and phase-contrast microscopy were also performed in parallel. We report that ERK1/2 and Akt activities are rapidly stimulated following wounding of HGE-17 cells. Treatment of confluent HGE-17 cells or primary cultures of gastric epithelial cells with the phosphatidylinositol 3-kinase inhibitor LY294002, but not the MEK1 inhibitor, PD98059, significantly inhibits basal and TGFalpha-induced migration following wounding. Conversely, treatment of wounded HGE-17 cells with phosphatidylinositol(3,4,5)-triphosphate is sufficient to stimulate basal cell migration by 235%. In addition, pp60c-src kinase activity and tyrosine phosphorylation of epidermal growth factor receptors (EGFR) are also rapidly enhanced after wounding and pharmacological inhibition of both these activities strongly attenuates basal and TGFalpha-induced migration as well as Akt phosphorylation levels. In conclusion, the present results indicate that EGFR-dependent PI3K activation promotes restitution of wounded human gastric epithelial monolayers.

The transcription factor Egr1 is a direct regulator of multiple tumor suppressors including TGFbeta1, PTEN, p53, and fibronectin

Recent studies are reviewed indicating that the transcription factor early growth response-1 (Egr1) is a direct regulator of multiple tumor suppressors including TGFbeta1, PTEN, p53, and fibronectin. The downstream pathways of these factors display multiple nodes of interaction with each other, suggesting the existence of a functional network of suppressor factors that serve to maintain normal growth regulation and resist the emergence of transformed variants. Paradoxically, Egr1 is oncogenic in prostate cancer. In the majority of these cancers, PTEN or p53 is inactive. It is suggested that these defects in the suppressor network allow for the unopposed induction of TGFbeta1 and fibronectin, which favor transformation and survival of prostate tumor epithelial cells, and explain the role of Egr1 in prostate cancer. Egr1 is a novel and logical target for intervention by gene therapy methods, and targeting methods are discussed.

Selective cyclooxygenase (COX) inhibition causes damage to portal hypertensive gastric mucosa: roles of nitric oxide and NF-kappaB

Portal hypertension (PHT) is associated with increased susceptibility of the gastric mucosa to injury by a variety of factors, including nonsteroidal anti-inflammatory drugs (NSAIDs) that nonselectively inhibit both isoforms of cyclooxygenase (COX-1 and -2). PHT gastric mucosa also has excessive nitric oxide (NO) production that contributes to the general increased susceptibility to injury. Using a rat model of PHT, we studied whether selective COX inhibition, which does not damage normal (normotensive) gastric mucosa, is sufficient to cause PHT gastric damage and, if so, whether and how excessive NO is involved. Indomethacin, a nonselective NSAID, caused 2.4-fold more gastric injury to PHT vs. normotensive sham-operated (SO) control rats. Neither NS-398 nor celecoxib, selective COX-2 inhibitors, caused gastric damage in either SO or PHT rats. SC-560, a selective COX-1 inhibitor, did not cause gastric damage in SO rats but dose-dependently caused gastric damage in PHT rats. There was a compensatory increase in COX-2 expression and activity in SC-560-treated SO rats but not SC-560-treated PHT rats. Partial inhibition of NO production restored gastric COX-2 expression and activity levels in SC-560-treated PHT rats to those of SC-560-treated SO rats, by a mechanism consistent with induction of NF-kappaB, and significantly reduced gastric damage. These studies indicate that, in contrast to normotensive gastric mucosa, inhibition of COX-1 alone is sufficient to cause PHT gastric damage as a result of excessive NO that prevents the induction of NF-kappaB and the compensatory increase in COX-2.

Relationship between expression of PTEN and cyclinE and Helicobacter pylori infection in gastric cancer

AIM: To investigate the relationship between H pylori infection and PTEN, cyclinE expression in gastric cancer and adjacent mucosal tissues, and to study the possible mechanism of H pylori in gastric carcinogenesis.

METHODS: Both rapid urease and pathological test were used to examine H pylori in 59 cases of specimen. The expression of PTEN and cyclinE in gastric cancer and adjacent mucosal tissues was detected by immunohistochemical technique (SP method).

RESULTS: PTEN expression in gastric cancer tissues was significantly lower than that in the cancer adjacent tissues (50.85% vs 96.61%, P < 0.05); however, CyclinE expression in gastric cancer tissues was significantly higher than that in cancer adjacent tissues. The level of PTEN expression in well-differentiated adenocarcinoma was significantly higher than that in poorly-differentiated adenocarcinoma and mucinous carcinoma (68.4% vs 33.3%, P < 0.05 68.4% vs 37.5%, P < 0.05 respectively); however, the level of CyclinE expression in well-differentiated adenocarcinoma was significantly lower than that in poorly-differentiated adenocarcinoma and mucinous carcinoma (31.5% vs 68.8%, P < 0.05; 31.5% vs 66.7%, P < 0.05); PTEN expression in in H pylori positive group was lower than that in H pylori negative group (51.9% vs 59.4%, P > 0.05); CyclinE expression had no significant difference between H pylori positive and negative gastric cancer tissues.

CONCLUSION: Pathogenesis of gastric cancer relates to loss of suppression gene PTEN and over-expression of oncogene cyclinE, and suppression gene PTEN probably plays a role in development of gastric cancer induced by H pylori infection.