Alpha2beta1 integrin signalling enhances cyclooxygenase-2 expression in intestinal epithelial cells

Involvement of redox signalling in tumour cell dormancy and metastasis

Decades of research on oncogene-driven carcinogenesis and gene-expression regulatory networks only started to unveil the complexity of tumour cellular and molecular biology. This knowledge has been successfully implemented in the clinical practice to treat primary tumours. In contrast, much less progress has been made in the development of new therapies against metastasis, which are the main cause of cancer-related deaths. More recently, the role of epigenetic and microenviromental factors has been shown to play a key role in tumour progression. Free radicals are known to communicate the intracellular and extracellular compartments, acting as second messengers and exerting a decisive modulatory effect on tumour cell signalling. Depending on the cellular and molecular context, as well as the intracellular concentration of free radicals and the activation status of the antioxidant system of the cell, the signalling equilibrium can be tilted either towards tumour cell survival and progression or cell death. In this regard, recent advances in tumour cell biology and metastasis indicate that redox signalling is at the base of many cell-intrinsic and microenvironmental mechanisms that control disseminated tumour cell fate and metastasis. In this manuscript, we will review the current knowledge about redox signalling along the different phases of the metastatic cascade, including tumour cell dormancy, making emphasis on metabolism and the establishment of supportive microenvironmental connections, from a redox perspective.

Studies of postpartum mammary gland involution reveal novel pro-metastatic mechanisms

Postpartum involution is the process by which the lactating mammary gland returns to the pre-pregnant state after weaning. Expression of tumor-promotional collagen, upregulation of matrix metalloproteinases, infiltration of M2 macrophages, and remodeling of blood and lymphatic vasculature are all characteristics shared by the involuting mammary gland and breast tumor microenvironment. The tumor promotional nature of the involuting mammary gland is perhaps best evidenced by cases of postpartum breast cancer (PPBC), or those cases diagnosed within 10 years of most recent childbirth. Women with PPBC experience more aggressive disease and higher risk of metastasis than nulliparous patients and those diagnosed outside the postpartum window. Semaphorin 7a (SEMA7A), cyclooxygenase-2 (COX-2), and collagen are all expressed in the involuting mammary gland and, together, predict for decreased metastasis free survival in breast cancer. Studies investigating the role of these proteins in involution have been important for understanding their contributions to PPBC. Postpartum involution thus represents a valuable model for the identification of novel molecular drivers of PPBC and classical cancer hallmarks. In this review, we will highlight the similarities between involution and cancer in the mammary gland, and further define the contribution of SEMA7A/COX-2/collagen interplay to postpartum involution and breast tumor progression and metastasis.

Extracellular Matrix Induction of Intracellular Reactive Oxygen Species

SIGNIFICANCE

The extracellular matrix (ECM) is the noncellular component secreted by cells and is present within all tissues and organs. The ECM provides the structural support required for tissue integrity and also contributes to diseases, including cancer. Many diseases rich in ECM are characterized by changes in reactive oxygen species (ROS) levels that have been shown to have important context-dependent functions. Recent Advances: Many studies have found that the ECM affects ROS production through integrins. The activation of integrins by ECM ligands results in stimulation of multiple pathways that can generate ROS. Furthermore, control of ECM-integrin interaction by matricellular proteins is an underappreciated pathway that functions as an ROS rheostat in remodeling tissues.

CRITICAL ISSUES

A better understanding of how the ECM affects the generation of intracellular ROS is required for advances in the development of therapeutic strategies that affect or exploit oxidative stress.

FUTURE DIRECTIONS

Targeting ROS generation can be therapeutic or can promote disease progression in a context-dependent manner. Many ECM proteins can impact ROS generation. However, given the breadth of different proteins that constitute the ECM and the cell surface receptors that interact with ECM proteins, there are likely many tissue and microenvironmental-specific ROS-generating pathways that have yet to be investigated in depth. Identifying canonical pathways of ECM-induced ROS generation should be a priority for the field. Antioxid. Redox Signal. 27, 774-784.

Flavonoids in Inflammatory Bowel Disease: A Review

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestine that compromises the patients’ life quality and requires sustained pharmacological and surgical treatments. Since their etiology is not completely understood, non-fully-efficient drugs have been developed and those that have shown effectiveness are not devoid of quite important adverse effects that impair their long-term use. In this regard, a growing body of evidence confirms the health benefits of flavonoids. Flavonoids are compounds with low molecular weight that are widely distributed throughout the vegetable kingdom, including in edible plants. They may be of great utility in conditions of acute or chronic intestinal inflammation through different mechanisms including protection against oxidative stress, and preservation of epithelial barrier function and immunomodulatory properties in the gut. In this review we have revised the main flavonoid classes that have been assessed in different experimental models of colitis as well as the proposed mechanisms that support their beneficial effects.

Down-regulation of collagen I biosynthesis in intestinal epithelial cells exposed to indomethacin: a comparative proteome analysis

In contrast to accumulated knowledge about gastroduodenal injury associated with nonsteroidal antiinflammatory drugs (NSAIDs) such as indomethacin, small intestinal mucosal injuries have been noticed only recently, and the precise mechanism remains to be elucidated. To clarify the mechanism, we performed 2-DE on IEC-6 rat normal intestinal cells that were treated with indomethacin (200μΜ, 24h) or a vehicle control and identified 18 up-regulated and 8 down-regulated proteins through MALDI-TOF/TOF mass spectrometry. Among these proteins, collagen I and proteins involved in collagen I biosynthesis and maturation, including prolyl 4-hydroxylase subunit α1, protein disulfide isomerase A3 (PDIA3), calreticulin, and endoplasmin, were all down-regulated by indomethacin. Immunohistochemical staining of the intestinal mucosa of indomethacin-administered rats showed a decrease of collagen I on the apical surface of intestinal cells. Cell death induced by indomethacin was prominently suppressed when IEC-6 cells were grown on collagen I-coated plates. cis-4-Hydroxy-l-proline, a proline analog that inhibits collagen synthesis, depressed IEC-6 cell viability in a concentration-dependent manner. Cell death was also induced by short interfering RNA knockdown of endogenous collagen I in IEC-6 cells. In conclusion, by comparative proteome analysis, we identified down-regulation of collagen I as an important mechanism in NSAID-induced intestinal injury.

BIOLOGICAL SIGNIFICANCE

Small intestinal lesions induced by NSAIDs are of great concern in clinical settings. Various hypotheses have been proposed for the origin of these inflammatory responses, such as reduction in the blood flow, intestinal hypermotility, abnormal intestinal mucosal permeability, mitochondrial dysfunction, and reactive oxygen species, many of which are related to the inhibition of prostaglandin synthesis. However, the precise mechanism is yet to be known. The cellular process of the lesions must involve up- and down-regulations of a large number of proteins and complex interactions between them. To elucidate it, global and systematic identification of the proteins in intestinal cells affected by NSAIDs is essential. We found that the proteins exhibiting reduced expression by indomethacin treatment are collagen I and the proteins involved in collagen I synthesis and maturation. Consistent with this, immunohistochemical analysis showed that the indomethacin-treated rat intestinal mucosal cells exhibits decreased collagen I expression on its apical surface. Furthermore, the cell-protective effect of collagen on intestinal mucosal cells was demonstrated by the use of a collagen-synthesis inhibitor, short interfering RNA (siRNA) knockdown of endogenous collagen I, and cell cultivation on collagen I-coated plates versus uncoated plates. These results give important information on the role of the collagen synthesis in intestinal mucosa in the mechanism of NSAID-induced small intestinal lesions.

Reactive oxygen species and tumor metastasis

The migration and invasion of cancer cells are the first steps in metastasis. Through a series of cellular responses, including cytoskeletal reorganization and degradation of the extracellular matrix, cancer cells are able to separate from the primary tumor and metastasize to distant locations in the body. In cancer cells, reactive oxygen species (ROS) play important roles in the migration and invasion of cells. Stimulation of cell surface receptors with growth factors and integrin assembly generates ROS, which relay signals from the cell surface to important signaling proteins. ROS then act within cells to promote migration and invasion. In this review, we collect recent evidence pointing towards the involvement of ROS in tumor metastasis and discuss the roles of ROS at different stages during the process of cancer cell migration, invasion and epithelial-mesenchymal transition.

Molecular Crosstalk between Integrins and Cadherins: Do Reactive Oxygen Species Set the Talk?

The coordinate modulation of the cellular functions of cadherins and integrins plays an essential role in fundamental physiological and pathological processes, including morphogenesis, tissue differentiation and renewal, wound healing, immune surveillance, inflammatory response, tumor progression, and metastasis. However, the molecular mechanisms underlying the fine-tuned functional communication between cadherins and integrins are still elusive. This paper focuses on recent findings towards the involvement of reactive oxygen species (ROS) in the regulation of cell adhesion and signal transduction functions of integrins and cadherins, pointing to ROS as emerging strong candidates for modulating the molecular crosstalk between cell-matrix and cell-cell adhesion receptors.

Postpartum mammary gland involution drives progression of ductal carcinoma in situ through collagen and COX-2

The prognosis of breast cancer in young women is influenced by reproductive history. Women diagnosed within 5 years postpartum have worse prognosis than nulliparous women or women diagnosed during pregnancy. Here we describe a mouse model of postpartum breast cancer that identifies mammary gland involution as a driving force of tumor progression. In this model, human breast cancer cells exposed to the involuting mammary microenvironment form large tumors that are characterized by abundant fibrillar collagen, high cyclooxygenase-2 (COX-2) expression and an invasive phenotype. In culture, tumor cells are invasive in a fibrillar collagen and COX-2-dependent manner. In the involuting mammary gland, inhibition of COX-2 reduces the collagen fibrillogenesis associated with involution, as well as tumor growth and tumor cell infiltration to the lung. These data support further research to determine whether women at high risk for postpartum breast cancer would benefit from treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) during postpartum involution.

Changes in extracellular matrix composition regulate cyclooxygenase-2 expression in human mesangial cells

Glomerular diseases are characterized by a sustained synthesis and accumulation of abnormal extracellular matrix proteins, such as collagen type I. The extracellular matrix transmits information to cells through interactions with membrane components, which directly activate many intracellular signaling events. Moreover, accumulating evidence suggests that eicosanoids derived from cyclooxygenase (COX)-2 participate in a number of pathological processes in immune-mediated renal diseases, and it is known that protein kinase B (AKT) may act through different transcription factors in the regulation of the COX-2 promoter. The present results show that progressive accumulation of collagen I in the extracellular medium induces a significant increase of COX-2 expression in human mesangial cells, resulting in an enhancement in PGE2 production. COX-2 overexpression is due to increased COX-2 mRNA levels. The study of the mechanism implicated in COX-2 upregulation by collagen I showed focal adhesion kinase (FAK) activation. Furthermore, we observed that the activation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway by collagen I and collagen I-induced COX-2 overexpression was abolished by PI3K and AKT inhibitors. Additionally, we showed that the cAMP response element (CRE) transcription factor is implicated. Finally, we studied COX-2 expression in an animal model, NG-nitro-l-arginine methyl ester hypertensive rats. In renal tissue and vascular walls, COX-2 and collagen type I content were upregulated. In summary, our results provide evidence that collagen type I increases COX-2 expression via the FAK/PI3K/AKT/cAMP response element binding protein signaling pathway.

Reactive oxygen species in cancer

Elevated rates of reactive oxygen species (ROS) have been detected in almost all cancers, where they promote many aspects of tumour development and progression. However, tumour cells also express increased levels of antioxidant proteins to detoxify from ROS, suggesting that a delicate balance of intracellular ROS levels is required for cancer cell function. Further, the radical generated, the location of its generation, as well as the local concentration is important for the cellular functions of ROS in cancer. A challenge for novel therapeutic strategies will be the fine tuning of intracellular ROS signalling to effectively deprive cells from ROS-induced tumour promoting events, towards tipping the balance to ROS-induced apoptotic signalling. Alternatively, therapeutic antioxidants may prevent early events in tumour development, where ROS are important. However, to effectively target cancer cells specific ROS-sensing signalling pathways that mediate the diverse stress-regulated cellular functions need to be identified. This review discusses the generation of ROS within tumour cells, their detoxification, their cellular effects, as well as the major signalling cascades they utilize, but also provides an outlook on their modulation in therapeutics.

TGF-beta1 causes epithelial-mesenchymal transition in HaCaT derivatives, but induces expression of COX-2 and migration only in benign, not in malignant keratinocytes

BACKGROUND

Transforming growth factor beta (TGF-beta) acts as a tumor promoter by inducing epithelial-mesenchymal transition (EMT), which leads to a motile phenotype, enabling invasion and metastasis of cancer cells. Cancer-related inflammation, mediated by prostaglandins, has been proposed as a critical mechanism in conversion of benign cells to malignant.

OBJECTIVE

Induction of cyclooxygenase 2 (COX-2), producer of prostaglandins, is thought to be a prerequisite for TGF-beta-induced EMT in benign cells. We used HaCaT derivatives, representative of skin cancer progression, to investigate TGF-beta1 mediated EMT response, and the role of COX-2 in it.

METHODS

Effect of TGF-beta1 was investigated by analyzing cell proliferation, morphology and protein expression. Chemotaxis and scratch-wound assays were used to study migration.

RESULTS

TGF-beta1 caused proliferation arrest of benign and malignant HaCaT cells, and changed the epithelial morphology of benign and low-grade malignant cells, but not metastatic cells, to mesenchymal spindle-shape. Epithelial junction proteins ZO-1 and E-cadherin were downregulated in all cell lines in response to TGF-beta1, but mesenchymal markers were not induced, suggesting a partial EMT response. COX-2 and migration were induced only in benign HaCaT derivatives. Malignant derivatives did not induce COX-2 in response to TGF-beta 1 treatment, thus emphasizing the role of inflammation in EMT response of benign cells.

CONCLUSIONS

TGF-beta1 operates via distinct mechanisms in inducing EMT and metastasis, and supporting this we show that TGF-beta1 induces COX-2 and promotes the migration of benign cells, but does not further augment the migration of malignant cells, indicating their resistance to TGF-beta1 in the context of motility.

The tumor microenvironment in colorectal carcinogenesis

Colorectal cancer is the second leading cause of cancer-related mortality in the United States. Therapeutic developments in the past decade have extended life expectancy in patients with metastatic disease. However, metastatic colorectal cancers remain incurable. Numerous agents that were demonstrated to have significant antitumor activity in experimental models translated into disappointing results in extending patient survival. This has resulted in more attention being focused on the contribution of tumor microenvironment to the progression of a number of solid tumors including colorectal cancer. A more complete understanding of interactions between tumor epithelial cells and their stromal elements will enhance therapeutic options and improve clinical outcome. Here we will review the role of various stromal components in colorectal carcinogenesis and discuss the potential of targeting these components for the development of future therapeutic agents.

Enhanced 5-fluorouracil cytotoxicity in high cyclooxygenase-2 expressing colorectal cancer cells and xenografts induced by non-steroidal anti-inflammatory drugs via downregulation of dihydropyrimidine dehydrogenase

PURPOSE

To prove that 5-FU cytotoxicity could be increased by combination with low-dose non-steroidal anti-inflammatory drugs (NSAIDs) (indomethacin or NS-398) in high cyclooxygenase-2- (COX-2) expressing cells and xenografts through the modulation of dihydropyrimidine dehydrogenase (DPD) mRNA expression and/or enzyme activity.

METHODS

HT-29 cells were grown on collagen IV coated plates (HT-29-C). The antiproliferative effect of 5-fluorouracil (5-FU) +/- NSAIDs was examined on non-COX-2 expressing HT-29 and COX-2-expressing HT-29-C cells by sulphorhodamine B assay. The COX-2 and DPD expressions were visualized by immunofluorescent staining, and prostaglandin E(2) levels were measured by ELISA kit. The HT-29 xenograft was established in SCID mice and treated with 5-FU +/- NSAIDs for 5 days. The tumor volume, enzyme activity, and DPD mRNA expression were investigated by caliper, radioenzymatic method, and real-time RT-PCR, respectively. The drug interaction was calculated for both combinations (5-FU + indomethacin and 5-FU + NS-398).

RESULTS

Collagen IV up-regulated significantly the COX-2 and DPD mRNA, and protein expressions, and also their enzyme activities in HT-29 cells. NSAIDs enhanced in a synergistic manner the cytotoxic effect of 5-FU treatment both in vitro and in vivo. Downregulation of DPD was observed after 5-FU monotherapy, but the combined effect of NSAIDs and 5-FU on DPD mRNA expression, and enzyme activity was superior to the effect of 5-FU alone.

CONCLUSIONS

Since 5-FU + NSAID treatment can alter the DPD enzyme activity resulting in an enhanced cytotoxic effect, further studies in clinical practice are warranted.

Allogeneic hematopoietic stem cell transplantation for X-linked ectodermal dysplasia and immunodeficiency: case report and review of outcomes

Hypomorphic mutations in nuclear factor kappa B essential modulator (NEMO) cause X-linked ectodermal dysplasia with immunodeficiency (X-ED-ID). Clinical manifestations in boys with X-ED-ID apart from ectodermal dysplasia and immunodeficiency include osteopetrosis, lymphedema, and colitis. Further description of atypical findings in this disorder is needed. Treatment with allogeneic hematopoietic stem cell transplantation (HSCT) is in its infancy, and how or whether non-immune manifestations of defective NEMO function are impacted by HSCT is poorly described. We report an interesting case of a boy with NEMO mutation who had symptoms reminiscent of Omenn's syndrome and small intestinal villous atrophy with features reminiscent of tufting enteropathy. We describe his treatment course as well as reconstitution of immune function and correction of osteopetrosis post-HSCT, and review the cases of allogeneic HSCT reported to date in the literature.

CD47 regulates collagen I-induced cyclooxygenase-2 expression and intestinal epithelial cell migration

Increased epithelial cell expression of the cyclooxgenase-2 (COX-2) enzyme is a characteristic event of both inflammatory bowel disease and colon cancer. We here report the novel findings that collagen I-induced de novo synthesis of COX-2 in intestinal epithelial cells is inhibited by pertussis toxin (PTX) and by an inhibitory peptide selective for the heterotrimeric Gα_i3-protein. These findings could be explained by a regulatory involvement of the G-protein-dependent integrin-associated protein CD47. In support of this notion, we observed a collagen I-induced association between CD47 and α2 integrins. This association was reduced by a blocking anti-CD47 antibody but not by PTX or a control anti-β2 antibody. Furthermore, a blocking antibody against CD47, dominant negative CD47 or specific siRNA knock down of CD47, significantly reduced collagen I-induced COX-2 expression. COX-2 has previously been shown to regulate intestinal epithelial cell adhesion and migration. Morphological analysis of intestinal cells adhering to collagen I revealed a co-localisation of CD47 and α2 integrins to non-apoptotic membrane blebs enriched in Rho A and F-actin. The blocking CD47 antibody, PTX and a selective COX-2 inhibitor, dramatically inhibited the formation of these blebs. In accordance, migration of these cells on a collagen I-coated surface or through a collagen I gel were significantly reduced by the CD47 blocking antibody, siRNA knock down of CD47 and the COX-2 inhibitor NS-398. In conclusion, we present novel data that identifies the G-protein-dependent CD47 protein as a key regulator of collagen I-induced COX-2 expression and a promoter of intestinal epithelial cell migration.

Chemopreventive effects of the standardized extract (DA-9601) of Artemisia asiatica on azoxymethane-initiated and dextran sulfate sodium-promoted mouse colon carcinogenesis

Dextran sulfate sodium (DSS) administration has been reported to cause inflammation in mouse colonic mucosa, which promotes colon carcinogenesis. When male ICR mice were treated with a single intraperitoneal dose (10 mg/kg body weight) of azoxymethane (AOM) followed by 2.5% DSS in drinking water for 7 consecutive days, all developed tumors at the 16th wk, mostly in the distal colon. Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were markedly upregulated in the AOM-initiated and DSS-promoted colon tumors. The DNA binding activity of nuclear factor-kappaB (NF-kappa B) was also elevated in the colon tumors. In this study, we examined the chemopreventive effects of the standardized extract (DA-9601) of Artemisia asiatica that has been used in the traditional herbal medicine for the treatment of inflammatory disorders. Mice fed the chow diet containing 10% DA-9601 for 15 wk following DSS treatment displayed the significantly lower multiplicity of colon tumors. DA-9601 treatment suppressed the expression of COX-2 and iNOS as well as NF-kappa B DNA binding in the colonic tissues. It also downregulated the phosphorylation of extracellular, signal-regulated protein kinase and p38 mitogen-activated protein kinase that are upstream of NF-kappa B. Furthermore, DA-9601 reduced expression of beta-catenin in colonic mucosa of mice challenged with AOM plus DSS.

Redox signalling in anchorage-dependent cell growth

Current data have provided new perspectives concerning the regulation of non-transformed cell proliferation in response to both soluble growth factors and to adhesive cues. Non-transformed cells are anchorage dependent for the execution of the mitotic program and cannot avoid the concomitant signals starting from mitogenic molecules, as growth factors, and adhesive agents belonging to extracellular matrix. Reactive oxygen species play a key role during both growth factor and integrin receptor signalling and these second messengers are recognised to have a synergistic function for anchorage-dependent growth signalling. Redox regulated proteins include protein tyrosine phosphatases and protein tyrosine kinases, although with opposite regulation of their enzymatic activity, and cytoskeletal proteins as beta-actin. In this review we support a role of ROS as key second messengers granting a proper executed mitosis for anchorage-dependent cells, through redox regulation of several downstream targets. Deregulation of these redox pathways may help to guide transformed cells to elude the native apoptotic response to abolishment of signals started by cell/ECM contact, sustaining ectopic anchorage-independent cancer cell growth.