Tumor-derived prostaglandin E2 and transforming growth factor-beta stimulate endothelial cell motility through inhibition of protein phosphatase-2A and involvement of PTEN and phosphatidylinositide 3-kinase

Inflammatory stimuli promote growth and invasion of pancreatic cancer cells through NF-κB pathway dependent repression of PP2Ac

Previous studies have indicated that inflammatory stimulation represses protein phosphatase 2A (PP2A), a well-known tumor suppressor. However, whether PP2A repression participates in pancreatic cancer progression has not been verified. We used lipopolysaccharide (LPS) and macrophage-conditioned medium (MCM) to establish in vitro inflammation models, and investigated whether inflammatory stimuli affect pancreatic cancer cell growth and invasion PP2A catalytic subunit (PP2Ac)-dependently. Via nude mouse models of orthotopic tumor xenografts and dibutyltin dichloride (DBTC)-induced chronic pancreatitis, we evaluated the effect of an inflammatory microenvironment on PP2Ac expression in vivo. We cloned the PP2Acα and PP2Acβ isoform promoters to investigate the PP2Ac transcriptional regulation mechanisms. MCM accelerated pancreatic cancer cell growth; MCM and LPS promoted cell invasion. DBTC promoted xenograft growth and metastasis, induced tumor-associated macrophage infiltration, promoted angiogenesis, activated the nuclear factor-κB (NF-κB) pathway, and repressed PP2Ac expression. In vitro, LPS and MCM downregulated PP2Ac mRNA and protein. PP2Acα overexpression attenuated JNK, ERK, PKC, and IKK phosphorylation, and impaired LPS/MCM-stimulated cell invasion and MCM-promoted cell growth. LPS and MCM activated the NF-κB pathway in vitro. LPS and MCM induced IKK and IκB phosphorylation, leading to p65/RelA nuclear translocation and transcriptional activation. Overexpression of the dominant negative forms of IKKα attenuated LPS and MCM downregulation of PP2Ac, suggesting inflammatory stimuli repress PP2Ac expression NF-κB pathway-dependently. Luciferase reporter gene assay verified that LPS and MCM downregulated PP2Ac transcription through an NF-κB-dependent pathway. Our study presents a new mechanism in inflammation-driven cancer progression through NF-κB pathway-dependent PP2Ac repression.

High Concentrations of Uric Acid Inhibit Endothelial Cell Migration via miR-663 Which Regulates Phosphatase and Tensin Homolog by Targeting Transforming Growth Factor-β1

BACKGROUND

Whether microRNAs participate in endothelial dysfunction HUA remains unknown. A previous study indicated that miR-663 was the most significantly differentially expressed endothelial microRNA under HUA conditions. Some studies have demonstrated that the miR-663 target gene and TGF-β1, promoted endothelial cell migration by inhibiting PTEN deleted on chromosome 10. Therefore, we hypothesized that HUA inhibits endothelial migration via miR-663, which regulates PTEN by targeting TGF-β1.

METHODS

PCR analysis was performed to determine miR-663 expression levels. A luciferase assay was performed to validate whether miR-663 targets TGF-β1 directly. Western blot analysis was performed to determine TGF-β1 and PTEN expression levels. An miR-663 inhibitor and TGF-β1- and PTEN-specific siRNAs were transfected into EA.hy926 cells to inhibit miR-663, TGF-β1, and PTEN expression, respectively. A wound healing assay was performed to determine the migratory ability of EA.hy926 cells.

RESULTS

miR-663 had higher expression levels in HUA-stimulated endothelial cells and in the sera of hyperuricemic patients and animals. TGF-β1 was targeted directly by miR-663. Endothelial miR-663 was up-regulated under HUA conditions, and HUA inhibited endothelial cell migration via miR-663, which targeted TGF-β1. Thus, TGF-β1 regulated cell migration in a PTEN-dependent manner.

CONCLUSION

HUA inhibits endothelial cell migration via miR-663, which regulates PTEN by targeting TGF-β1.

Open-label, phase I dose-escalation study of sodium selenate, a novel activator of PP2A, in patients with castration-resistant prostate cancer

Background:

Angiogenesis is fundamental to the progression of many solid tumours including prostate cancer. Sodium selenate is a small, water-soluble, orally bioavailable activator of PP2A phosphatase with anti-angiogenic properties.

Methods:

This was a dose-escalation phase I study in men with asymptomatic, chemotherapy-naïve, castration-resistant prostate cancer. The primary objective was to determine the maximum tolerated dose (MTD). Secondary objectives included establishing the safety, tolerability and pharmacokinetic profile.

Results:

A total of 19 patients were enrolled. The MTD was 60 mg per day. Dose-limiting toxicity (fatigue and diarrhoea) was observed at 90 mg per day. The most frequently reported treatment-related adverse events across all treatment cohorts were nausea, diarrhoea, fatigue, muscle spasms, alopecia and nail disorders. No grade 4 toxicities were observed and there were no deaths on study. Linear pharmacokinetics was observed. One patient had a PSA response >50%. Median time to PSA progression (for non-responders) was 14.2 weeks. Mean PSA doubling time increased during the main treatment phase from 2.18 months before trial to 3.85 months.

Conclusion:

Sodium selenate is well tolerated at a dose of 60 mg per day with modest single-agent efficacy similar to other anti-angiogenic agents. Further trials in combination with conventional cytotoxic regimens are warranted.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

Cyclooxygenase-2 mediates hydrogen peroxide-induced wound repair in human endothelial cells

Cyclooxygenase-2 (Cox-2) metabolites produced by endothelial cells, particularly prostacyclin and prostaglandin E(2), profoundly affect vascular tone, regional blood flow, and angiogenesis. We have previously shown that reactive oxygen species induce Cox-2 expression in human endothelial cells (HUVEC), either on their own or as components of the signaling pathway triggered by TNFalpha, the prototypical inflammatory cytokine. Here we investigated the role of Cox-2 induced by hydrogen peroxide (H(2)O(2)), either exogenous or endogenously generated by TNFalpha, in the repair of a mechanically wounded HUVEC monolayer and probed the sources of H(2)O(2) that are involved in TNFalpha signaling and the pathways through which H(2)O(2) modulates Cox-2 expression. Results indicate that H(2)O(2)-induced Cox-2 activity participates in the repair of wounded monolayers. Both NADPH oxidase and the mitochondrial electron transport chain are involved in H(2)O(2) generation. Signaling triggered by H(2)O(2) for Cox-2 induction acts by increasing the protein tyrosine kinase phosphorylation that follows inhibition of protein phosphatase activity. The activation of p38 MAPK and its interaction in the inhibition of serine/threonine phosphatase activity are both critical steps in this event. We conclude that Cox-2 induced by H(2)O(2) plays an important role in promoting endothelial wound repair after injury, so that the cardioprotective effect of Cox-2 is due at least in part to its power of healing damaged endothelium.

Autocrine motility-stimulatory pathways of oral premalignant lesion cells

Patients with premalignant oral lesions have varying levels of risk of developing oral squamous cell carcinoma (OSCC), whose aggressiveness requires increased motility. Not known is if and how premalignant oral lesion cells acquire the increased motility characteristic of OSCC. This was addressed by immunohistochemical analysis of banked premalignant lesion tissues and by functional analyses using cultures established from premalignant oral lesions and OSCC. These studies showed premalignant oral lesion cells and OSCC to be more motile than normal keratinocytes. Concomitantly, levels of ceramide were reduced. The activity of the protein phosphatase PP-2A, which restricts motility and which can be activated by ceramide, was also diminished. This was due to IL-10 released from premalignant lesion cells. Treatment with a membrane-permeable ceramide restored PP-2A activity and blocked migration. These studies show an autocrine motility-stimulatory pathway that is mediated in premalignant lesion cells by IL-10 through its reduction of ceramide levels and inhibition of PP-2A activity.

Cellular Distribution, Post-translational Modification, and Tumorigenic Potential of Human Group III Secreted Phospholipase A2

Human group III secreted phospholipase A(2) (sPLA(2)-III) consists of a central group III sPLA(2) domain flanked by unique N- and C-terminal domains. We found that the sPLA(2) domain alone was sufficient for its catalytic activity and for its prostaglandin E(2) (PGE(2))-generating functions in various cell types. In several if not all cell types, the N- and C-terminal domains of sPLA(2)-III were proteolytically removed, leading to the production of the form containing only the sPLA(2) domain, which could be further N-glycosylated at two consensus sites. Immunohistochemistry demonstrated that sPLA(2)-III was preferentially expressed in the microvascular endothelium in human tissues with inflammation, ischemic injury, and cancer. In support of this, sPLA(2)-III was induced in cultured microvascular endothelial cells after stimulation with proinflammatory cytokines. Expression of sPLA(2)-III was also associated with various tumor cells, and colorectal cancer cells transfected with sPLA(2)-III exhibited enhanced PGE(2) production and cell proliferation, which required sPLA(2)-III catalytic activity. When implanted into nude mice, the sPLA(2)-III-transfected cells formed larger solid tumors with increased angiogenesis compared with control cells. Moreover, small interfering RNA for sPLA(2)-III significantly reduced PGE(2) production and proliferation of colorectal cancer cells. Taken together, these results reveal unique cell type-specific processing and N-glycosylation of sPLA(2)-III and the potential role of this enzyme in cancer development by stimulating tumor cell growth and angiogenesis.