Activated macrophages promote Wnt signalling through tumour necrosis factor-alpha in gastric tumour cells

The neurotrophic receptor Ntrk2 directs lymphoid tissue neovascularization during Leishmania donovani infection

The neurotrophic tyrosine kinase receptor type 2 (Ntrk2, also known as TrkB) and its ligands brain derived neurotrophic factor (Bdnf), neurotrophin-4 (NT-4/5), and neurotrophin-3 (NT-3) are known primarily for their multiple effects on neuronal differentiation and survival. Here, we provide evidence that Ntrk2 plays a role in the pathologic remodeling of the spleen that accompanies chronic infection. We show that in Leishmania donovani-infected mice, Ntrk2 is aberrantly expressed on splenic endothelial cells and that new maturing blood vessels within the white pulp are intimately associated with F4/80(hi)CD11b(lo)CD11c(+) macrophages that express Bdnf and NT-4/5 and have pro-angiogenic potential in vitro. Furthermore, administration of the small molecule Ntrk2 antagonist ANA-12 to infected mice significantly inhibited white pulp neovascularization but had no effect on red pulp vascular remodeling. We believe this to be the first evidence of the Ntrk2/neurotrophin pathway driving pathogen-induced vascular remodeling in lymphoid tissue. These studies highlight the therapeutic potential of modulating this pathway to inhibit pathological angiogenesis.

Chronic subordinate colony housing paradigm: a mouse model to characterize the consequences of insufficient glucocorticoid signaling

Chronic, in particular chronic psychosocial, stress is a burden of modern societies and known to be a risk factor for numerous somatic and affective disorders (in detail referenced below). However, based on the limited existence of appropriate, and clinically relevant, animal models for studying the effects of chronic stress, the detailed behavioral, physiological, neuronal, and immunological mechanisms linking stress and such disorders are insufficiently understood. To date, most chronic stress studies in animals employ intermittent exposure to the same (homotypic) or to different (heterotypic) stressors of varying duration and intensity. Such models are only of limited value, since they do not adequately reflect the chronic and continuous situation that humans typically experience. Furthermore, application of different physical or psychological stimuli renders comparisons to the mainly psychosocial stressors faced by humans, as well as between the different stress studies almost impossible. In contrast, rodent models of chronic psychosocial stress represent situations more akin to those faced by humans and consequently seem to hold more clinical relevance. Our laboratory has developed a model in which mice are exposed to social stress for 19 continuous days, namely the chronic subordinate colony housing (CSC) paradigm, to help bridge this gap. The main aim of the current review article is to provide a detailed summary of the behavioral, physiological, neuronal, and immunological consequences of the CSC paradigm, and wherever possible relate the findings to other stress models and to the human situation.

MicroRNA-29c mediates initiation of gastric carcinogenesis by directly targeting ITGB1

OBJECTIVE

Gastric cancer (GC) remains difficult to cure due to heterogeneity in a clinical challenge and the molecular mechanisms underlying this disease are complex and not completely understood. Accumulating evidence suggests that microRNAs (miRNAs) play an important role in GC, but the role of specific miRNAs involved in this disease remains elusive. We performed next generation sequencing (NGS)-based whole-transcriptome profiling to discover GC-specific miRNAs, followed by functional validation of results.

DESIGN

NGS-based miRNA profiles were generated in matched pairs of GCs and adjacent normal mucosa (NM). Quantitative RT-PCR validation of miR-29c expression was performed in 274 gastric tissues, which included two cohorts of matched GC and NM specimens. Functional validation of miR-29c and its gene targets was undertaken in cell lines, as well as K19-C2mE and K19-Wnt1/C2mE transgenic mice.

RESULTS

NGS analysis revealed four GC-specific miRNAs. Among these, miR-29c expression was significantly decreased in GC versus NM tissues (p<0.001). Ectopic expression of miR-29c mimics in GC cell lines resulted in reduced proliferation, adhesion, invasion and migration. High miR-29c expression suppressed xenograft tumour growth in nude mice. Direct interaction between miR-29c and its newly discovered target, ITGB1, was identified in cell lines and transgenic mice. MiR-29c expression demonstrated a stepwise decrease in wild type hyperplasia-dysplasia cascade in transgenic mice models of GC.

CONCLUSIONS

MiR-29c acts as a tumour suppressor in GC by directly targeting ITGB1. Loss of miR-29c expression is an early event in the initiation of gastric carcinogenesis and may serve as a diagnostic and therapeutic biomarker for patients with GC.

Vitamin D and colon cancer

Calcitriol, 1α, 25-dihydroxyvitamin D₃ (1,25 (OH)₂D₃), the most active form of vitamin D, is a pleotropic hormone with a wide range of biological activities. Due to its ability to regulate calcium and phosphate metabolism, 1,25D₃ plays a major role in bone health. In addition, 1,25D₃ binds to the vitamin D receptor and thereby regulates the expression of a number of genes which control growth, differentiation and survival of cancer cells. In agreement, the levels of vitamin D₃ appear to be an essential determinant for the development and progression of colon cancer and supplementation with vitamin D₃ is effective in suppressing intestinal tumorigenesis in animal models. Vitamin D₃ has been estimated to lower the incidence of colorectal cancer by 50%, which is consistent with the inverse correlation between dietary vitamin D₃ intake or sunlight exposure and human colorectal cancer. Several studies confirmed that increasing vitamin D₃ lowers colon cancer incidence, reduces polyp recurrence, and that sufficient levels of vitamin D₃ are associated with better overall survival of colon cancer patients. Vitamin D regulates the homeostasis of intestinal epithelium by modulating the oncogenic Wnt signaling pathway and by inhibiting tumor-promoting inflammation. Both activities contribute to the ability of 1,25D₃ to prevent the development and progression of colon cancer.

The immune microenvironment confers resistance to MAPK pathway inhibitors through macrophage-derived TNFα

Recently, the rationale for combining targeted therapy with immunotherapy has come to light, but our understanding of the immune response during MAPK pathway inhibitor treatment is limited. We discovered that the immune microenvironment can act as a source of resistance to MAPK pathway-targeted therapy, and moreover during treatment this source becomes reinforced. In particular, we identified macrophage-derived TNFα as a crucial melanoma growth factor that provides resistance to MAPK pathway inhibitors through the lineage transcription factor MITF (microphthalmia transcription factor). Most strikingly, in BRAF-mutant melanomas of patients and BRAF(V600E) melanoma allografts, MAPK pathway inhibitors increased the number of tumor-associated macrophages, and TNFα and MITF expression. Inhibiting TNFα signaling with IκB kinase inhibitors profoundly enhanced the efficacy of MAPK pathway inhibitors by targeting not only the melanoma cells but also the microenvironment. In summary, we identify the immune microenvironment as a novel source of resistance and reveal a new strategy to improve the efficacy of targeted therapy in melanoma.

SIGNIFICANCE

This study identifies the immune microenvironment as a source of resistance to MAPK pathway inhibitors through macrophage-derived TNFα, and reveals that in patients on treatment this source becomes reinforced. Inhibiting IκB kinase enhances the efficacy of MAPK pathway inhibitors, which identifies this approach as a potential novel strategy to improve targeted therapy in melanoma.

Cancer stem cells, pluripotency, and cellular heterogeneity: a WNTer perspective

Cancer stem cells (CSCs) are thought to represent the "beating heart" of malignant growth as they continuously fuel tumors through their ability to self-renew and differentiate. Moreover, they are also believed to underlie malignant behavior, local invasion, and metastasis in distal organ sites upon reversible epithelial-to-mesenchymal transitions (EMTs). Nevertheless, the CSC concept has been the object of controversy, mainly due to the absence of robust operational definitions and to the lack of consistency in the use of the often incorrect nomenclature employed to refer to these cells. Notwithstanding the controversies, it is now generally accepted that primary cancers are organized in hierarchical fashion with neoplastic stem-like cells able to give rise to new CSCs and to more committed malignant cells. Notably, these hierarchical structures are not unidirectional, but are rather characterized by a more dynamic equilibrium where stem-like and more committed cancer cells transit from one meta-state to the other partly because of cues from the microenvironment (niche), but also because of intrinsic and yet incompletely understood characteristics in the activation/silencing of specific signal transduction pathways. Here, we will focus on the Wnt/β-catenin signaling pathway as one of the major regulator of stemness in homeostasis and cancer, and on germ cell tumors as the type of malignancy that most closely mimics normal embryonic development and as such serve as a unique model to study the role of stem cells in neoplasia.

Tissue-specific actions of FXR in metabolism and cancer

The nuclear Farnesoid X Receptor (FXR) is a transcription factor critically involved in metabolic homeostasis in the gut-liver axis. FXR activity is mediated by hormonal and dietary signals and driven by bile acids (BAs), which are the natural FXR ligands. Given the great physiological importance in BA homeostasis, as well as in the regulation of glucose and lipid metabolism, FXR plays a pivotal role in the pathogenesis of a wide range of disease of the liver, biliary tract and intestine, including hepatic and colorectal cancer. In the last years several studies have shown the relative FXR tissue-specific importance, highlighting synergism and additive effects in the liver and intestine. Gain- and loss-of-FXR-function mouse models have been generated in order to identify the biological processes and the molecular FXR targets. Taking advantage of the knowledge on the structure-activity relationship of BAs for FXR, semi-synthetic and synthetic molecules have been generated to obtain more selective and powerful FXR activators than BAs. This article is part of a Special Issue entitled: Linking transcription to physiology in lipodomics.

Cigarette smoking and gastrointestinal diseases: the causal relationship and underlying molecular mechanisms (review)

Cigarette smoking is an important risk factor for gastrointestinal (GI) disorders, including peptic ulcers, inflammatory bowel diseases, such as Crohn's disease and cancer. In this review, the relationship between smoking and GI disorders and the underlying mechanisms are discussed. It has been demonstrated that cigarette smoking is positively associated with the pathogenesis of peptic ulcers and the delay of ulcer healing. Mechanistic studies have shown that cigarette smoke and its active ingredients can cause mucosal cell death, inhibit cell renewal, decrease blood flow in the GI mucosa and interfere with the mucosal immune system. Cigarette smoking is also an independent risk factor for various types of cancer of the GI tract. In this review, we also summarize the mechanisms through which cigarette smoking induces tumorigenesis and promotes the development of cancer in various sections of the GI tract. These mechanisms include the activation of nicotinic acetylcholine receptors, the formation of DNA adducts, the stimulation of tumor angiogenesis and the modulation of immune responses in the GI mucosa. A full understanding of these pathogenic mechanisms may help us to develop more effective therapies for GI disorders in the future.

Interaction between gastric cancer stem cells and the tumor microenvironment

Gastric cancer (GC) remains a leading cause of cancer-related deaths worldwide. Cancer stem cells (CSCs) are selectively capable of tumor initiation and are implicated in tumor relapse and metastasis, thus, governing the prognosis of GC patients. Stromal cells and extracellular matrix adjacent to cancer cells are known to form a supportive environment for cancer progression. CSC properties are also regulated by their microenvironment through cell signaling and related factors. This review presents the current findings regarding the influence of the tumor microenvironment on GC stem cells, which will support the development of novel therapeutic strategies for patients with GC.

Inflammatory cues acting on the adult intestinal stem cells and the early onset of cancer (review)

The observation that cancer often arises at sites of chronic inflammation has prompted the idea that carcinogenesis and inflammation are deeply interwoven. In fact, the current literature highlights a role for chronic inflammation in virtually all the steps of carcinogenesis, including tumor initiation, promotion and progression. The aim of the present article is to review the current literature on the involvement of chronic inflammation in the initiation step and in the very early phases of tumorigenesis, in a type of cancer where adult stem cells are assumed to be the cells of origin of neoplasia. Since the gastrointestinal tract is regarded as the best-established model system to address the liaison between chronic inflammation and neoplasia, the focus of this article will be on intestinal cancer. In fact, the anatomy of the intestinal epithelial lining is uniquely suited to study adult stem cells in their niche, and the bowel crypt is an ideal developmental biology system, as proliferation, differentiation and cell migration are all distributed linearly along the long axis of the crypt. Moreover, crypt stem cells are regarded today as the most likely targets of neoplastic transformation in bowel cancer. More specifically, the present review addresses the molecular mechanisms whereby a state of chronic inflammation could trigger the neoplastic process in the intestine, focusing on the generation of inflammatory cues evoking enhanced proliferation in cells not initiated but at risk of neoplastic transformation because of their stemness. Novel experimental approaches, based on triggering an inflammatory stimulus in the neighbourhood of adult intestinal stem cells, are warranted to address some as yet unanswered questions. A possible approach, the targeted transgenesis of Paneth cells, may be aimed at 'hijacking' the crypt stem cell niche from a status characterized by the maintenance of homeostasis to local chronic inflammation, with the prospect of initiating neoplastic transformation in that site.

Coexpression of CD44-positive/CD133-positive cancer stem cells and CD204-positive tumor-associated macrophages is a predictor of survival in pancreatic ductal adenocarcinoma

BACKGROUND

The interactions between cancer stem cells (CSCs) and tumor-associated macrophages (TAMs) can promote tumor progression, maintain the CSCs population, and reduce therapeutic effects. The objective of this study was to investigate the coexpression of CSCs and TAMs and its clinical significance in pancreatic ductal adenocarcinoma (PDAC).

METHODS

Ninety-six patients with PDAC were included in this study. Tissue microarrays were constructed for immunostaining of the CSCs markers CD44 and CD133 and the TAMs marker CD204. Correlations between the expression of CSCs and TAMs markers and clinicopathologic characteristics or disease progression were analyzed.

RESULTS

Expression levels of CD44/CD133 and CD204 were significantly higher in tumor tissues than in normal tissues (P < .0001). The variables associated with survival were high coexpression of CD44/CD133 (P = .000), high expression of CD204 (P = .011), and tumor grade (P = .014). There was a positive correlation between CD44/CD133 and CD204 expression (r = 0.294; P = .004). Survival analysis indicated that high coexpression of CD44/CD133 and CD204 was associated significantly with shorter overall survival (P = .000) and disease-free survival (P = .003). Multivariate analysis revealed that high CD44/CD133 expression was an independent prognostic factor for disease-free survival, whereas high CD204 expression was an independent predictor for both overall and disease-free survival.

CONCLUSIONS

Coexpression of CD44/CD133 and CD204 is a useful survival prediction marker for patients with PDAC. Cancer 2014;120:2766–2777. © The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.

The clinical significance of pancreatic cancer stem cells and tumor-associated macrophages is explored in patients with pancreatic ductal adenocarcinoma. The results clearly demonstrate that coexpression of 2 cancer stem cell markers (CD44 and CD133) and a tumor-associated macrophage marker (CD204) is a useful prognostic factor for predicting the survival of patients with pancreatic ductal adenocarcinoma after surgery.

Molecular mechanisms of oncogene-induced inflammation and inflammation-sustained oncogene activation in gastrointestinal tumors: an under-appreciated symbiotic relationship

Inflammation plays an integral part in tumor initiation. Specifically, patients with colitis, pancreatitis, or hepatitis have an increased susceptibility to cancer. The activation, mutation, and overexpression of oncogenes have been well documented in cell proliferation and transformation. Recently, oncogenes were found to also regulate the inflammatory milieu in tumors. Similarly, the inflammatory milieu can promote oncogene activation. In this review, we summarize advances of the symbiotic relationship oncogene activation and inflammation in gastrointestinal tumors such as colorectal, hepatic, and pancreatic tumors. NF-κB and STAT3 are the two most common pathways that are deregulated via these oncogenes. Understanding these interactions may yield effective therapeutic strategies for tumor prevention and treatment.

Helicobacter pylori and the molecular pathogenesis of intestinal-type gastric carcinoma

Gastric carcinoma is an inflammation-related cancer caused by long-term infection with the human bacterial pathogen, Helicobacter pylori. The pattern of acute-on-chronic inflammation causes progressive mucosal damage which may result in atrophy with metaplastic epithelia and eventually gastric cancer. Recently, it has been recognized that H. pylori can also cause genetic instability such as double-stranded DNA breaks and can produce gene activation and silencing via epigenetic pathways. As genetic instability is the hallmark of cancer, we highlight recent progress in understanding the gastric carcinogenesis in relation to H. pylori-related inflammation, H. pylori-induced double-stranded DNA breakage and aberrant gene expression as well as the mechanisms and role of H. pylori-associated epigenetic change in gene expression.

Immune response and the tumor microenvironment: how they communicate to regulate gastric cancer

Gastric cancer is the second most common cause of cancer-related death in the world. A growing body of evidence indicates that inflammation is closely associated with the initiation, progression, and metastasis of many tumors, including those of gastric cancer. In addition, approximately 60% of the world's population is colonized by Helicobacter pylori, which accounts for more than 50% of gastric cancers. While the role of inflammation in intestinal and colonic cancers is relatively well defined, its role in stomach neoplasia is still unclear because of the limited access of pathogens to the acidic environment and the technical difficulties isolating and characterizing immune cells in the stomach, especially in animal models. In this review, we will provide recent updates addressing how inflammation is involved in gastric malignancies, and what immune characteristics regulate the pathogenesis of stomach cancer. Also, we will discuss potential therapeutics that target the immune system for the efficient treatment of gastric cancer.

A Wnt/β-catenin negative feedback loop represses TLR-triggered inflammatory responses in alveolar epithelial cells

Increasing evidence has demonstrated that the epithelial cells in the lung play crucial roles in regulating certain inflammatory responses by modulating Wnt signaling during microbial infection. However, the anti-microbial functions of Wnt signaling in alveolar epithelial cells remain elusive. In this report, we show that Wnt/β-catenin signaling is repressed in A549 alveolar epithelial cells during a Toll-like receptor ligand stimulation with Mycobacterium bovis Bacillus Calmette-Guerin (BCG) or lipopolysaccharide (LPS). In addition to activating TLR signaling, a stimulation of BCG or LPS led to the up-regulation of a Wnt receptor Frizzled-1, cytosolic GSK3β and Axin, and the down-regulation of nuclear β-catenin, lymphoid enhancer factor 1 and transcription factor 4. While an enhancement of β-catenin activity suppressed the TLR signal response, and substantially led to alleviate the TLR ligand-induced pro-inflammatory responses. Importantly, gain and loss of function studies by overexpressing or silencing of TLR signaling adaptor, myeloid differentiation primary response gene 88 (MyD88) further demonstrated an inverse relationship between TLR signaling and canonical Wnt signaling in A549 cells. These data imply that Wnt/β-catenin signaling acts as a negative feedback loop to suppress inflammation in alveolar epithelial cells, and averts cell injury from excessive inflammatory reactions. This study thus reveals a novel immunoregulatory mechanism in alveolar epithelial cells in response to bacterial infection.

Activated macrophages promote Wnt/β-catenin signaling in cholangiocarcinoma cells

The Wnt/β-catenin signaling pathway is pathologically activated in cholangiocarcinoma (CCA). Here, we determined the expression profile as well as biological role of activated Wnt/β-catenin signaling in CCA. The quantitative reverse transcription polymerase chain reaction demonstrated that Wnt3a, Wnt5a, and Wnt7b mRNA were significantly higher in CCA tissues than adjacent non-tumor tissues and normal liver tissues. Immunohistochemical staining revealed that Wnt3a, Wnt5a, and Wnt7b were positive in 92.1, 76.3, and 100 % of 38 CCA tissues studied. It was noted that Wnt3 had a low expression in tumor cells, whereas a high expression was mainly found in inflammatory cells. Interestingly, a high expression level of Wnt5a was significantly correlated to poor survival of CCA patients (P=0.009). Membrane localization of β-catenin was reduced in the tumors compared to normal bile duct epithelia, and we also found that 73.7 % of CCA cases showed the cytoplasmic localization. Inflammation is known to be a risk factor for CCA development, and we tested whether this might induce Wnt/β-catenin signaling. We found that lipopolysaccharides (LPS) elevated the expression of Wnt3 both mRNA and protein levels in the macrophage cell line. Additionally, the conditioned media taken from LPS-induced activated macrophage culture promoted β-catenin accumulation in CCA cells. Furthermore, transient suppression of β-catenin by siRNA significantly induced growth inhibition of CCA cells, concurrently with decreasing cyclin D1 protein level. In conclusion, the present study reports the abundant expression of Wnt protein family and β-catenin in CCA as well as the effect of inflammatory condition on Wnt/β-catenin activation in CCA cells. Importantly, abrogation of β-catenin expression caused significant CCA cell growth inhibition. Thus, the Wnt/β-catenin signaling pathway may contribute to CCA cell proliferation and hence may serve as a prognostic marker for CCA progression and provide a potential target for CCA therapy.

Context-dependent activation of Wnt signaling by tumor suppressor RUNX3 in gastric cancer cells

RUNX3 is a tumor suppressor for a variety of cancers. RUNX3 suppresses the canonical Wnt signaling pathway by binding to the TCF4/β-catenin complex, resulting in the inhibition of binding of the complex to the Wnt target gene promoter. Here, we confirmed that RUNX3 suppressed Wnt signaling activity in several gastric cancer cell lines; however, we found that RUNX3 increased the Wnt signaling activity in KatoIII and SNU668 gastric cancer cells. Notably, RUNX3 expression increased the ratio of the Wnt signaling-high population in the KatoIII cells. although the maximum Wnt activation level of individual cells was similar to that in the control. As found previously, RUNX3 also binds to TCF4 and β-catenin in KatoIII cells, suggesting that these molecules form a ternary complex. Moreover, the ChIP analyses revealed that TCF4, β-catenin and RUNX3 bind the promoter region of the Wnt target genes, Axin2 and c-Myc, and the occupancy of TCF4 and β-catenin in these promoter regions is increased by the RUNX3 expression. These results suggest that RUNX3 stabilizes the TCF4/β-catenin complex on the Wnt target gene promoter in KatoIII cells, leading to activation of Wnt signaling. Although RUNX3 increased the Wnt signaling activity, its expression resulted in suppression of tumorigenesis of KatoIII cells, indicating that RUNX3 plays a tumor-suppressing role in KatoIII cells through a Wnt-independent mechanism. These results indicate that RUNX3 can either suppress or activate the Wnt signaling pathway through its binding to the TCF4/β-catenin complex by cell context-dependent mechanisms.

Involvement of CDX2 in the cross talk between TNF-α and Wnt signaling pathway in the colon cancer cell line Caco-2

Tumor necrosis factor-α (TNF-α) is highly upregulated in inflammation and reduces the expression of the intestinal transcription factor, Caudal-related homeobox transcription factor 2 (CDX2). Wnt/β-catenin signaling is critical for intestinal cell proliferation, but a decreased CDX2 expression has influence on the Wnt signaling-related genes and progression of colorectal cancer. Although several inflammatory signaling pathways, including TNF-α, have been reported to promote Wnt/β-catenin activity and development of cancer, the underlying molecular mechanisms remain unclear. The aim was to investigate the signaling pathways involved in the TNF-α-mediated downregulation of CDX2, and its influence on Wnt/β-catenin signaling components in colon cancer cells. The expression of TNF-α and CDX2 at the invasive front were evaluated by immunohistochemical staining and showed reduced CDX2-positive cells in tumor buddings in areas with TNF-α expression in the surrounding inflammatory cells. In vitro studies revealed that TNF-α treatment showed a dose-dependent decrease of CDX2 messenger RNA (mRNA) and protein expression in Caco-2 cells. Inhibition of nuclear factor-kappaB or p38 pathways showed that these are involved in the TNF-α-dependent downregulation of CDX2. Furthermore, TNF-α-mediated downregulation of CDX2 was found to significantly decrease the mRNA levels of adenomatous polyposis coli (APC), axis inhibition protein 2 (AXIN2) and glycogen synthase kinase-3 beta (GSK3β), whereas the mRNA levels of Wnt targets were significantly elevated in TNF-α-treated Caco-2 cells. These findings were associated with reduced binding of CDX2 to promoter or enhancer regions of APC, AXIN2 and GSK3β. In conclusion, it was found that TNF-α induces the expression of Wnt signaling components through a downregulation of the CDX2 expression that might have a tumor-promoting effect on colon cancer cells.

The role of inflammation in gastric cancer

Gastric cancer, despite its declining incidence rate, is still the second cause of cancer-related death worldwide, killing 750,000 people each year and remaining the second common type of cancer. The best examples of inflammation-associated cancer in human beings may be gastric cancer. Understanding the molecular mechanism of the inflammation in gastric carcinogenesis is important for developing new strategies against gastric cancer.

Mechanisms linking excess adiposity and carcinogenesis promotion

Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well established for several tumor types, such as breast cancer in post-menopausal women, colorectal, and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: (i) inflammatory changes leading to macrophage polarization and altered adipokine profile; (ii) insulin resistance development; and (iii) adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases.

TNF-α modulates TLR2-dependent responses during mycobacterial infection

Multifunctional roles of tumor necrosis factor-alpha (TNF-α) during the mycobacterial pathogenesis make it an important molecule to understand and to examine the course of infection. Identification and analysis of TNF-α response can largely contribute to determine the potential host mediators for therapeutic intervention against tuberculosis. The current chapter describes several methods to assess the ability of TNF-α signaling to modulate toll-like receptor (TLR)2 signaling, another key player in mycobacterial infection and its responses. Experiments involving neutralizing antibodies, antagonists, pharmacological inhibitors, and siRNA-mediated gene silencing are discussed in this chapter to establish the role of TNF-α signaling. The widely used protein and mRNA analysis readouts like enzyme-linked immunosorbent assay (ELISA), immunoblotting, fluorescence-activated cell sorting (FACS), and quantitative real-time RT-PCR are useful to estimate and confirm the mediators involved in TNF-α and TLR2 signaling.

Immune chaperone gp96 drives the contributions of macrophages to inflammatory colon tumorigenesis

Macrophages are important drivers in the development of inflammation-associated colon cancers, but the mechanistic underpinnings for their contributions are not fully understood. Furthermore, Toll-like receptors have been implicated in colon cancer, but their relevant cellular sites of action are obscure. In this study, we show that the endoplasmic reticulum chaperone gp96 is essential in tumor-associated macrophages (TAM) to license their contributions to inflammatory colon tumorigenesis. Mice where gp96 was genetically deleted in a macrophage-specific manner exhibited reduced colitis and inflammation-associated colon tumorigenesis. Attenuation of colon cancer in these mice correlated strikingly with reduced mutation rates of β-catenin, increased efficiency of the DNA repair machinery, and reduced expression of proinflammatory cytokines, including interleukin (IL)-17 and IL-23 in the tumor microenvironment. The genotoxic nature of TAM-associated inflammation was evident by increased expression of genes in the DNA repair pathway. Our work deepens understanding of how TAM promote oncogenesis by altering the molecular oncogenic program within epithelial cells, and it identifies gp96 as a lynchpin chaperone needed in TAM to license their function and impact on expression of critical inflammatory cytokines in colon tumorigenesis.

Macrophage-derived reactive oxygen species suppress miR-328 targeting CD44 in cancer cells and promote redox adaptation

CD44 is frequently overexpressed in a wide variety of epithelial malignancies including gastrointestinal cancer and causes resistance to currently available treatments. MicroRNAs (miRNAs) are non-coding RNAs that regulate molecular pathways in cancer by targeting various genes. The aim of this study was to investigate the regulation of CD44 expression by miRNAs and to develop new molecular targets in gastrointestinal cancer. We performed miRNA screening in six human gastrointestinal cancer cell lines and identified three candidate miRNAs that could regulate CD44 expression in gastrointestinal cancer. Among these, we focused on miR-328 and examined its functional relevance using growth assays and cytotoxicity assays. CD44 expression was reduced in gastrointestinal cancer cell lines forced to express miR-328, leading to inhibition of cancer cell growth in vitro and in vivo, and impaired resistance to chemotherapeutic drugs and reactive oxygen species (ROS). In contrast, induction of CD44 expression by miR-328 inhibitor led to promotion of cancer cell growth. Furthermore, we revealed that ROS produced by macrophages triggered CD44 expression through suppression of miR-328 in gastric cancer cells. Finally, tumor-infiltrating macrophages (CD68 and CD163) were closely related to both miR-328 downregulation and CD44 upregulation in 63 patients with surgically resected gastric cancer. These findings suggest that macrophages in the tumor microenvironment may cause increased CD44 expression through miR-328 suppression, resulting in tumor progression by enhancing ROS defense. miR-328-CD44 signaling mediated by macrophages may thus represent a potential target for the treatment of gastrointestinal cancer.

Helicobacter pylori protein JHP0290 binds to multiple cell types and induces macrophage apoptosis via tumor necrosis factor (TNF)-dependent and independent pathways

Activated macrophages at the sub-mucosal space play a major role in generating innate immune responses during H. pylori infection. Final disease outcome largely depends on how H. pylori and bacterium-derived products modulate macrophage responses. Here, we report that JHP0290, a functionally unknown protein from H. pylori, regulates macrophage functions. Recombinant purified JHP0290 (rJHP0290) had the ability to bind to several cell types including macrophages, human gastric epithelial cell lines, human monocyte-derived dendritic cells (MoDC) and human neutrophils. Exposure to rJHP0290 induced apoptosis in macrophages concurrent with release of proinflammatory cytokine tumor necrosis factor (TNF). A mutant strain of H. pylori disrupted in the jhp0290 gene was significantly impaired in its ability to induce apoptosis and TNF in macrophages confirming the role of endogenous protein in regulating macrophage responses. Intracellular signaling involving Src family of tyrosine kinases (SFKs) and ERK MAPK were required for rJHP0290-induced TNF release and apoptosis in macrophages. Furthermore, rJHP0290-induced TNF release was partly dependent on activation of nuclear transcription factor-κB (NF-κB). Neutralizing antibodies against TNF partially blocked rJHP0290-induced macrophage apoptosis indicating TNF-independent pathways were also involved. These results provide mechanistic insight into the potential role of the protein JHP0290 during H. pylori-associated disease development. By virtue of its ability to induce TNF, an acid suppressive proinflammatory cytokine and induction of macrophage apoptosis, JHP0290 possibly helps in persistent survival of the bacterium inside the stomach.

M2 macrophages activate WNT signaling pathway in epithelial cells: relevance in ulcerative colitis

Macrophages, which exhibit great plasticity, are important components of the inflamed tissue and constitute an essential element of regenerative responses. Epithelial Wnt signalling is involved in mechanisms of proliferation and differentiation and expression of Wnt ligands by macrophages has been reported. We aim to determine whether the macrophage phenotype determines the expression of Wnt ligands, the influence of the macrophage phenotype in epithelial activation of Wnt signalling and the relevance of this pathway in ulcerative colitis. Human monocyte-derived macrophages and U937-derived macrophages were polarized towards M1 or M2 phenotypes and the expression of Wnt1 and Wnt3a was analyzed by qPCR. The effects of macrophages and the role of Wnt1 were analyzed on the expression of β-catenin, Tcf-4, c-Myc and markers of cell differentiation in a co-culture system with Caco-2 cells. Immunohistochemical staining of CD68, CD206, CD86, Wnt1, β-catenin and c-Myc were evaluated in the damaged and non-damaged mucosa of patients with UC. We also determined the mRNA expression of Lgr5 and c-Myc by qPCR and protein levels of β-catenin by western blot. Results show that M2, and no M1, activated the Wnt signaling pathway in co-culture epithelial cells through Wnt1 which impaired enterocyte differentiation. A significant increase in the number of CD206+ macrophages was observed in the damaged mucosa of chronic vs newly diagnosed patients. CD206 immunostaining co-localized with Wnt1 in the mucosa and these cells were associated with activation of canonical Wnt signalling pathway in epithelial cells and diminution of alkaline phosphatase activity. Our results show that M2 macrophages, and not M1, activate Wnt signalling pathways and decrease enterocyte differentiation in co-cultured epithelial cells. In the mucosa of UC patients, M2 macrophages increase with chronicity and are associated with activation of epithelial Wnt signalling and diminution in enterocyte differentiation.

Activation of NF-κB: bridging the gap between inflammation and cancer in colitis-mediated colon carcinogenesis

Several studies have shown the anti-neoplastic effects of non-steroidal anti-inflammatory drugs (NSAIDs) on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis, but how these drugs act in case of inflammation-augmented tumorigenesis is still not clear. The present study therefore designs an animal model of colitis-associated colon cancer where 3% Dextran sufate sodium (DSS) is used to develop ulcerative colitis and DMH treatment leads to colon carcinogenesis as early as in six weeks. Clinical symptoms for ulcerative colitis were studied using Disease Activity Index (DAI) while myeloperoxidase assay marked the neutrophil infiltration in DSS and DMH treated groups. The present results indicated the upregulation of the activity of inflammatory marker enzyme, cyclooxygenase-2 (cox-2) and pro-inflammatory cytokines such as TNF-α, IL-1β, IL-4 and IFN-γ with the treatment of DSS as well as DMH. The presence of cytokines in the inflammatory milieu might lead to the transformation of cytoplasmic inactive NF-κB (Nuclear Factor κB) to its active nuclear form, thereby leading to tumorigenesis. The administration of celecoxib along with DSS and DMH, revealed its chemopreventive efficacy in colitis as well as colon cancer. The effect of different doses of DMH on mouse colon was also investigated to obtain a minimum dose of DMH which can induce visible lesions in mice colons at a high incidence.

Functional role of CD44v-xCT system in the development of spasmolytic polypeptide-expressing metaplasia

Cancer development is often preceded by the appearance of preneoplastic lesions. In gastric carcinogenesis, chronic inflammation and histopathologic progression of the stomach epithelium lead to the development of metaplasia and eventually adenocarcinoma. The cell surface protein CD44, especially its variant isoforms (CD44v), has been implicated in metaplasia-carcinoma sequence progression in the stomach. We recently found that CD44v interacts with and stabilizes xCT, a subunit of the cystine transporter system xc(-), in cancer cells and thereby increases cystine uptake and confers resistance to various types of cellular stress in vivo. The functional relevance of CD44v and xCT in the development of preneoplastic lesions, however, has remained unknown. We have now examined the role of the CD44v-xCT system in the development of spasmolytic polypeptide-expressing metaplasia (SPEM) in mouse models of gastric carcinogenesis. CD44v was found to be expressed de novo in SPEM, and CD44v(+) metaplastic cells manifested upregulation of xCT expression compared with CD44v(-) cells. Genetic ablation of CD44 or treatment with sulfasalazine, an inhibitor of xCT-dependent cystine transport, suppressed the development of SPEM and subsequent gastric tumor growth. Therapy targeted to CD44v-xCT could thus prove effective for prevention or attenuation of the CD44v-dependent development of preneoplastic lesions and cancer.

Colon Macrophages Polarized by Commensal Bacteria Cause Colitis and Cancer through the Bystander Effect

Intestinal commensal bacteria have recently been shown to trigger macrophages to produce diffusible clastogens (or chromosome-breaking factors) through a bystander effect (BSE) that mediates DNA damage and induces chromosomal instability in neighboring cells. Colon macrophages appear central to colon carcinogenesis and BSE through the expression of tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). The former induces netrin-1, a regulator of intestinal epithelial cell apoptosis, and the latter generates trans-4-hydroxy-2-nonenal (4-HNE), an endogenous mutagen. To test whether colon macrophages are key effectors for BSE, we depleted these cells in interleukin-10 knockout mice colonized with Enterococcus faecalis using encapsulated liposomal clodronate (ELC), a bisphosphonate that causes macrophage apoptosis. We observed that E. faecalis polarizes colon macrophages to an M1 phenotype. In addition, depleting these cells suppressed COX-2 and TNF-α, blocked the formation of 4-HNE protein adducts, and inhibited up-regulation of netrin-1-all markers for BSE. Finally, treatment with ELC prevented colitis, β-catenin activation, and cancer formation. These results show that selected human commensals can polarize colon macrophages to the M1 phenotype and, when activated, serve as the key effector for bacterial-induced BSE. Our findings suggest that depleting M1-polarized macro-phages is a mechanism for the chemopreventive activity of bisphosphonates and that it represents a new strategy for preventing colon cancer induced by intestinal commensals.

IAPs on the move: role of inhibitors of apoptosis proteins in cell migration

Inhibitors of Apoptosis Proteins (IAPs) are a class of highly conserved proteins predominantly known for the regulation of caspases and immune signaling. However, recent evidence suggests a crucial role for these molecules in the regulation of tumor cell shape and migration by controlling MAPK, NF-κB and Rho GTPases. IAPs directly control Rho GTPases, thus regulating cell shape and migration. For instance, XIAP and cIAP1 function as the direct E3 ubiquitin ligases of Rac1 and target it for proteasomal degradation. IAPs are differentially expressed in tumor cells and have been targeted by several cancer therapeutic drugs that are currently in clinical trials. Here, we summarize the current knowledge on the role of IAPs in the regulation of cell migration and discuss the possible implications of these observations in regulating tumor cell metastases.

TNF-α/TNFR1 signaling promotes gastric tumorigenesis through induction of Noxo1 and Gna14 in tumor cells

Helicobacter pylori infection induces chronic inflammation that contributes to gastric tumorigenesis. Tumor necrosis factor (TNF-α) is a proinflammatory cytokine, and polymorphism in the TNF-α gene increases the risk of gastric cancer. We herein investigated the role of TNF-α in gastric tumorigenesis using Gan mouse model, which recapitulates human gastric cancer development. We crossed Gan mice with TNF-α (Tnf) or TNF-α receptor TNFR1 (Tnfrsf1a) knockout mice to generate Tnf-/- Gan and Tnfrsf1a-/- Gan mice, respectively, and examined their tumor phenotypes. Notably, both Tnf-/- Gan mice and Tnfrsf1a-/- Gan mice showed similar, significant suppression of gastric tumor growth compared with control Tnf+/+ or Tnfrsf1a+/+ Gan mice. These results indicate that TNF-α signaling through TNFR1 is important for gastric tumor development. Bone marrow (BM) transplantation experiments showed that TNF-α expressed by BM-derived cells (BMDCs) stimulates the TNFR1 on BMDCs by an autocrine or paracrine manner, which is important for gastric tumor promotion. Moreover, the microarray analysis and colony formation assay indicated that NADPH oxidase organizer 1 (Noxo1) and Gna14 are induced in tumor epithelial cells in a TNF-α-dependent manner, and have an important role in tumorigenicity and tumor-initiating cell property of gastric cancer cells. Accordingly, it is possible that the activation of TNF-α/TNFR1 signaling in the tumor microenvironment promotes gastric tumor development through induction of Noxo1 and Gna14, which contribute to maintaining the tumor cells in an undifferentiated state. The present results indicate that targeting the TNF-α/TNFR1 pathway may be an effective preventive or therapeutic strategy for gastric cancer.

Interleukin-11 is the dominant IL-6 family cytokine during gastrointestinal tumorigenesis and can be targeted therapeutically

Among the cytokines linked to inflammation-associated cancer, interleukin (IL)-6 drives many of the cancer "hallmarks" through downstream activation of the gp130/STAT3 signaling pathway. However, we show that the related cytokine IL-11 has a stronger correlation with elevated STAT3 activation in human gastrointestinal cancers. Using genetic mouse models, we reveal that IL-11 has a more prominent role compared to IL-6 during the progression of sporadic and inflammation-associated colon and gastric cancers. Accordingly, in these models and in human tumor cell line xenograft models, pharmacologic inhibition of IL-11 signaling alleviated STAT3 activation, suppressed tumor cell proliferation, and reduced the invasive capacity and growth of tumors. Our results identify IL-11 signaling as a potential therapeutic target for the treatment of gastrointestinal cancers.

The gastrointestinal tumor microenvironment

Over the past decade, the microenvironment of gastrointestinal tumors has gained increasing attention because it is required for tumor initiation, progression, and metastasis. The tumor microenvironment has many components and has been recognized as one of the major hallmarks of epithelial cancers. Although therapeutic strategies for gastrointestinal cancer have previously focused on the epithelial cell compartment, there is increasing interest in reagents that alter the microenvironment, based on reported interactions among gastrointestinal epithelial, stromal, and immune cells during gastrointestinal carcinogenesis. We review the different cellular components of the gastrointestinal tumor microenvironment and their functions in carcinogenesis and discuss how improving our understanding of the complex stromal network could lead to new therapeutic strategies.

Salivary gland cancer stem cells

Emerging evidence suggests the existence of a tumorigenic population of cancer cells that demonstrate stem cell-like properties such as self-renewal and multipotency. These cells, termed cancer stem cells (CSC), are able to both initiate and maintain tumor formation and progression. Studies have shown that CSC are resistant to traditional chemotherapy treatments preventing complete eradication of the tumor cell population. Following treatment, CSC are able to re-initiate tumor growth leading to patient relapse. Salivary gland cancers are relatively rare but constitute a highly significant public health issue due to the lack of effective treatments. In particular, patients with mucoepidermoid carcinoma or adenoid cystic carcinoma, the two most common salivary malignancies, have low long-term survival rates due to the lack of response to current therapies. Considering the role of CSC in resistance to therapy in other tumor types, it is possible that this unique sub-population of cells is involved in resistance of salivary gland tumors to treatment. Characterization of CSC can lead to better understanding of the pathobiology of salivary gland malignancies as well as to the development of more effective therapies. Here, we make a brief overview of the state-of-the-science in salivary gland cancer, and discuss possible implications of the cancer stem cell hypothesis to the treatment of salivary gland malignancies.

Helicobacter pylori in gastric carcinogenesis: mechanisms

Helicobacter pylori infection induces chronic inflammation and is the strongest known risk factor for gastric cancer. The genomes of H pylori are highly diverse and therefore bacterial virulence factors play an important role in determining the outcome of H pylori infection, in combination with host responses that are augmented by environmental and dietary risk factors. It is important to gain further understanding of the pathogenesis of H pylori infection to develop more effective treatments for this common but deadly malignancy. This review focuses on the specific mechanisms used by H pylori to drive gastric carcinogenesis.

A New Herbal Formula, KSG-002, Suppresses Breast Cancer Growth and Metastasis by Targeting NF- κ B-Dependent TNF α Production in Macrophages

Tumor-associated macrophages (TAMs) in tumor microenvironment regulate cancer progression and metastases. In breast cancer, macrophage infiltration is correlated with a poor prognosis. While metastatic breast cancer is poor prognostic with a severe mortality, therapeutic options are still limited. In this study, we demonstrate that KSG-002, a new herbal composition of radices Astragalus membranaceus and Angelica gigas, suppresses breast cancer via inhibiting TAM recruitment. KSG-002, an extract of radices Astragalus membranaceus and Angelica gigas at 3 : 1 ratio, respectively, inhibited MDA-MB-231 xenograft tumor growth and pulmonary metastasis in nude mice, while KSG-001, another composition (1 : 1 ratio, w/w), enhanced tumor growth, angiogenesis, and pulmonary metastasis, in vivo. KSG-002 further decreased the infiltrated macrophage numbers in xenograft tumor cohorts. In Raw264.7 cells, KSG-002 but not KSG-001 inhibited cell proliferation and migration and reduced TNF-alpha (TNF α ) production by inhibiting NF- κ B pathway. Furthermore, a combinatorial treatment of KSG-002 with TNF α inhibited a proliferation and migration of both MDA-MB-231 and Raw264.7 cells. Taken together, we conclude that KSG-002 suppresses breast cancer growth and metastasis through targeting NF- κ B-mediated TNF α production in macrophages.

Macrophages stimulate gastric and colorectal cancer invasion through EGFR Y(1086), c-Src, Erk1/2 and Akt phosphorylation and smallGTPase activity

The interactions between cancer cells and their microenvironment are crucial for malignant progression, as they modulate invasion-related activities. Tumor-associated macrophages are generally considered allies in the process of tumor progression in several types of cancer, although their role on gastric and colorectal carcinomas is still poorly understood. In this report, we studied the influence of primary human macrophages on gastric and colorectal cancer cells, considering invasion, motility/migration, proteolysis and activated intracellular signaling pathways. We demonstrated that macrophages stimulate cancer cell invasion, motility and migration, and that these effects depend on matrix metalloproteinase (MMP) activity and on the activation of epidermal growth factor receptor (EGFR) (at the residue Y(1086)), PLC-γ (phospholipase C-gamma) and Gab1 (GRB2-associated binding protein-1), as evidenced by siRNA (small interference RNA) experiments. Epidermal growth factor (EGF)-immunodepletion impaired macrophage-mediated cancer cell invasion and motility, suggesting that EGF is the pro-invasive and pro-motile factor produced by macrophages. Macrophages also induced gastric and colorectal cancer cell phosphorylation of Akt, c-Src and ERK1/2, and led to an increase of RhoA and Cdc42 activity. Interestingly, whereas macrophage-mediated cancer cell c-Src and ERK1/2 phosphorylation occurred downstream EGFR activation, Akt phosphorylation seems to be a parallel event, taking place in an EGFR-independent manner. The involvement of EGF, EGFR-downstream signaling partners and MMPs in macrophage-mediated invasion provides novel insights into the molecular crosstalk established between cancer cells and macrophages, opening new perspectives for the design of new and more efficient therapeutic strategies to counteract cancer cell invasion.

Myeloid cell RelA/p65 promotes lung cancer proliferation through Wnt/β-catenin signaling in murine and human tumor cells

Smoking is the most important risk factor for both lung cancer (LC) and chronic obstructive pulmonary disease. The aim of this study was to investigate the role of myeloid cell nuclear factor-κB in the regulation of tumor cell growth signaling. We subjected mice lacking myeloid RelA/p65 (rela(Δ-/-)) to a metastatic LC model. Cigarette smoke (CS) exposure significantly increased the proliferation of Lewis lung carcinoma cell tumors in wild-type mice. In CS-exposed rela(Δ-/-) mice, the tumor growth was largely inhibited. Transcriptome and pathway analysis of cancer tissue revealed a fundamental impact of myeloid cells on various growth signaling pathways, including the Wnt/β-catenin pathway. In conclusion, myeloid RelA/p65 is necessary to link smoke-induced inflammation with LC growth and has a role in the activation of Wnt/β-catenin signaling in tumor cells.

Molecular profiling of multiple human cancers defines an inflammatory cancer-associated molecular pattern and uncovers KPNA2 as a uniform poor prognostic cancer marker

BACKGROUND

Immune evasion is one of the recognized hallmarks of cancer. Inflammatory responses to cancer can also contribute directly to oncogenesis. Since the immune system is hardwired to protect the host, there is a possibility that cancers, regardless of their histological origins, endow themselves with a common and shared inflammatory cancer-associated molecular pattern (iCAMP) to promote oncoinflammation. However, the definition of iCAMP has not been conceptually and experimentally investigated.

METHODS AND FINDINGS

Genome-wide cDNA expression data was analyzed for 221 normal and 324 cancer specimens from 7 cancer types: breast, prostate, lung, colon, gastric, oral and pancreatic. A total of 96 inflammatory genes with consistent dysregulation were identified, including 44 up-regulated and 52 down-regulated genes. Protein expression was confirmed by immunohistochemistry for some of these genes. The iCAMP contains proteins whose roles in cancer have been implicated and others which are yet to be appreciated. The clinical significance of many iCAMP genes was confirmed in multiple independent cohorts of colon and ovarian cancer patients. In both cases, better prognosis correlated strongly with high CXCL13 and low level of GREM1, LOX, TNFAIP6, CD36, and EDNRA. An "Inflammatory Gene Integrated Score" was further developed from the combination of 18 iCAMP genes in ovarian cancer, which predicted overall survival. Noticeably, as a selective nuclear import protein whose immuno-regulatory function just begins to emerge, karyopherin alpha 2 (KPNA2) is uniformly up-regulated across cancer types. For the first time, the cancer-specific up-regulation of KPNA2 and its clinical significance were verified by tissue microarray analysis in colon and head-neck cancers.

CONCLUSION

This work defines an inflammatory signature shared by seven epithelial cancer types and KPNA2 as a consistently up-regulated protein in cancer. Identification of iCAMP may not only serve as a novel biomarker for prognostication and individualized treatment of cancer, but also have significant biological implications.

Unraveling the signaling pathways promoting fibrosis in Dupuytren's disease reveals TNF as a therapeutic target

Dupuytren's disease is a very common progressive fibrosis of the palm leading to flexion deformities of the digits that impair hand function. The cell responsible for development of the disease is the myofibroblast. There is currently no treatment for early disease or for preventing recurrence following surgical excision of affected tissue in advanced disease. Therefore, we sought to unravel the signaling pathways leading to the development of myofibroblasts in Dupuytren's disease. We characterized the cells present in Dupuytren's tissue and found significant numbers of immune cells, including classically activated macrophages. High levels of proinflammatory cytokines were also detected in tissue from Dupuytren's patients. We compared the effects of these cytokines on contraction and profibrotic signaling pathways in fibroblasts from the palmar and nonpalmar dermis of Dupuytren's patients and palmar fibroblasts from non-Dupuytren's patients. Exogenous addition of TNF, but not other cytokines, including IL-6 and IL-1β, promoted differentiation into specifically of palmar dermal fibroblasts from Dupuytren's patients in to myofibroblasts. We also demonstrated that TNF acts via the Wnt signaling pathway to drive contraction and profibrotic signaling in these cells. Finally, we examined the effects of targeted cytokine inhibition. Neutralizing antibodies to TNF inhibited the contractile activity of myofibroblasts derived from Dupuytren's patients, reduced their expression of α-smooth muscle actin, and mediated disassembly of the contractile apparatus. Therefore, we showed that localized inflammation in Dupuytren's disease contributes to the development and progression of this fibroproliferative disorder and identified TNF as a therapeutic target to down-regulate myofibroblast differentiation and activity.

Genetic and pharmacological targeting of CSF-1/CSF-1R inhibits tumor-associated macrophages and impairs BRAF-induced thyroid cancer progression

Advanced human thyroid cancers are densely infiltrated with tumor-associated macrophages (TAMs) and this correlates with a poor prognosis. We used BRAF-induced papillary thyroid cancer (PTC) mouse models to examine the role of TAMs in PTC progression. Following conditional activation of BRAF^V600E in murine thyroids there is an increased expression of the TAM chemoattractants Csf-1 and Ccl-2. This is followed by the development of PTCs that are densely infiltrated with TAMs that express Csf-1r and Ccr2. Targeting CCR2-expressing cells during BRAF-induction reduced TAM density and impaired PTC development. This strategy also induced smaller tumors, decreased proliferation and restored a thyroid follicular architecture in established PTCs. In PTCs from mice that lacked CSF-1 or that received a c-FMS/CSF-1R kinase inhibitor, TAM recruitment and PTC progression was impaired, recapitulating the effects of targeting CCR2-expressing cells. Our data demonstrate that TAMs are pro-tumorigenic in advanced PTCs and that they can be targeted pharmacologically, which may be potentially useful for patients with advanced thyroid cancers.

Role of macrophage polarization in tumor angiogenesis and vessel normalization: implications for new anticancer therapies

Angiogenesis, the formation of new capillary blood vessels from preexisting vasculature, is one of the hallmarks of cancer that is pivotal for tumor growth and metastasis. Tumor vessels are known to be abnormal, with typically aberrant, leaky and disordered vessels. Thus, the combination of angiogenesis inhibition and vessel normalization is a potential strategy for anticancer therapy. The solid tumor is composed of not only cancer cells, but also the nonmalignant resident stromal cells, such as bone-marrow-derived cells (BMDCs) and cancer-associated fibroblasts (CAFs). Tumor-associated macrophages (TAMs) are the most abundant cell components of BMDCs, which play a significant role in promoting tumor progression. Accumulating evidences from both patient biopsies and experimental animal models have shown that TAMs function in tumor angiogenesis and vessel abnormalization in a density- and phenotype-dependent manner. This chapter will discuss the evidence for the factors and signaling pathways that are involved in macrophage recruitment and polarization in the tumor microenvironment, and it summarizes the role and underlying molecular mechanisms of macrophage polarization in tumor angiogenesis and vessel normalization. In addition, an overview of the potential of targeting TAM polarization for anticancer therapy will be provided.

Recruitment of monocytes/macrophages in different tumor microenvironments

After emigration from the bone marrow into the peripheral blood, monocytes enter tissues and differentiate into macrophages. Monocytes/macrophages have many roles in immune regulation, angiogenesis, and tumor metastasis and invasion. In addition, studies have revealed that these cells are essential to tumor progression. Recently, an accumulation of evidence has indicated that macrophages in distinct regions of tumor masses have distinct origins. For instance, classical monocytes appear to be a major source of macrophages in tumor epithelial, perivascular, and hypoxic regions. In contrast, non-classical monocytes are an important source of macrophages in the tumor perivascular region. During the past century, it has been demonstrated that several chemoattractants can regulate the recruitment of monocytes/macrophages to tumor sites. Despite the importance of monocytes/macrophages in tumor progression, there had been, until recently, no efforts to summarize receptor-ligand pairs between tumor-derived chemokines and corresponding receptors in monocytes in different microenvironments. In this review, we present a cohesive view of the distinct expression patterns of chemokine receptors in two different monocyte subsets (classical and non-classical monocytes) and describe their roles in monocyte/macrophage recruitment into distinct tumor microenvironments. This review provides insight into the behavior of monocytes/macrophages in different tumor microenvironments.

Helicobacter pylori infection induced gastric cancer; advance in gastric stem cell research and the remaining challenges

Helicobacter pylori infection is the major cause of gastric cancer, which remains an important health care challenge. Recent investigation in gastric stem cell or progenitor cell biology has uncovered valuable information in understanding the gastric gland renewal and maintenance of homeostasis, they also provide clues for further defining the mechanisms by which gastric cancer may originate and progress. Lgr5, Villin-promoter, TFF2-mRNA and Mist have recently been identified as gastric stem/progenitor cell markers; their identification enriched our understanding on the gastric stem cell pathobiology during chronic inflammation and metaplasia. In addition, advance in gastric cancer stem cell markers such as CD44, CD90, CD133, Musashi-1 reveal novel information on tumor cell behavior and disease progression implicated for therapeutics. However, two critical questions remain to be of considerable challenges for future exploration; one is how H. pylori or chronic inflammation affects gastric stem cell or their progenitors, which give rise to mucus-, acid-, pepsinogen-, and hormone-secreting cell lineages. Another one is how bacterial infection or inflammation induces oncogenic transformation and propagates into tumors. Focus on the interactions of H. pylori with gastric stem/progenitor cells and their microenvironment will be instrumental to decipher the initiation and origin of gastric cancer. Future studies in these areas will be critical to uncover molecular mechanisms of chronic inflammation-mediated oncogenic transformation and provide options for cancer prevention and intervention. We review recent progress and discuss future research directions in these important research fields.

Inflammation and colorectal cancer: colitis-associated neoplasia

Connection between inflammation and cancer is a rapidly developing field. Epidemiological data suggests that inflammation along with distinct arms of host immune system plays a very important role in the development and progression of many different cancers. Inflammatory bowel disease (IBD) is an important risk factor for the development of colon cancer, namely, colitis-associated cancer (CAC). The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and may differ between CAC and other forms of colorectal cancer. Recent work has shed light on the role of distinct immune cells, cytokines, and other immune mediators in virtually all of the steps of colonic tumorigenesis, including tumor initiation and promotion as well as progression and metastasis. The close proximity of colonic tumors to the myriad of intestinal microbes, as well as instrumental role of microbiota in IBD, introduces microbes as new players capable of triggering inflammation and possibly promoting tumorigenesis. Various mechanisms of CAC tumorigenesis as well as new possible hints for the future approaches for prevention and therapy are discussed in this review.

The role of PGE2-associated inflammatory responses in gastric cancer development

Accumulating evidence indicates that inflammation plays a critical role in cancer development. Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme for prostanoid biosynthesis, including prostaglandin E(2) (PGE(2)), and plays a key role in both inflammation and cancer. It has been demonstrated that inhibition of COX-2 and PGE(2) receptor signaling results in the suppression of tumor development in a variety of animal models. However, the molecular mechanisms underlying COX-2/PGE(2)-associated inflammation in carcinogenesis have not yet been fully elucidated. In order to study the role of PGE(2)-associated inflammatory responses in tumorigenesis, it is important to use in vivo mouse models that recapitulate human cancer development from molecular mechanisms with construction of tumor microenvironment. We have developed a gastritis model (K19-C2mE mice) in which an inflammatory microenvironment is constructed in the stomach via induction of the COX-2/PGE(2) pathway. We also developed a gastric cancer mouse model (Gan mice) in which the mice develop inflammation-associated gastric tumors via activation of both the COX-2/PGE(2) pathway and Wnt signaling. Expression analyses using these in vivo models have revealed novel mechanisms of the inflammatory responses underlying gastric cancer development. PGE(2)-associated inflammatory responses activate epidermal growth factor receptor (EGFR) signaling through the induction of EGFR ligands and ADAMs that release EGFR ligands from the cell membrane. In Gan mice, a combination treatment with EGFR and COX-2 inhibitors significantly suppresses gastric tumorigenesis. Moreover, PGE(2)-associated inflammation downregulates tumor suppressor microRNA, miR-7, in gastric cancer cells, which suppresses epithelial differentiation. These results indicate that PGE(2)-associated inflammatory responses promote in vivo gastric tumorigenesis via several different molecular mechanisms.

The role of PGE2-associated inflammatory responses in gastric cancer development

Accumulating evidence indicates that inflammation plays a critical role in cancer development. Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme for prostanoid biosynthesis, including prostaglandin E(2) (PGE(2)), and plays a key role in both inflammation and cancer. It has been demonstrated that inhibition of COX-2 and PGE(2) receptor signaling results in the suppression of tumor development in a variety of animal models. However, the molecular mechanisms underlying COX-2/PGE(2)-associated inflammation in carcinogenesis have not yet been fully elucidated. In order to study the role of PGE(2)-associated inflammatory responses in tumorigenesis, it is important to use in vivo mouse models that recapitulate human cancer development from molecular mechanisms with construction of tumor microenvironment. We have developed a gastritis model (K19-C2mE mice) in which an inflammatory microenvironment is constructed in the stomach via induction of the COX-2/PGE(2) pathway. We also developed a gastric cancer mouse model (Gan mice) in which the mice develop inflammation-associated gastric tumors via activation of both the COX-2/PGE(2) pathway and Wnt signaling. Expression analyses using these in vivo models have revealed novel mechanisms of the inflammatory responses underlying gastric cancer development. PGE(2)-associated inflammatory responses activate epidermal growth factor receptor (EGFR) signaling through the induction of EGFR ligands and ADAMs that release EGFR ligands from the cell membrane. In Gan mice, a combination treatment with EGFR and COX-2 inhibitors significantly suppresses gastric tumorigenesis. Moreover, PGE(2)-associated inflammation downregulates tumor suppressor microRNA, miR-7, in gastric cancer cells, which suppresses epithelial differentiation. These results indicate that PGE(2)-associated inflammatory responses promote in vivo gastric tumorigenesis via several different molecular mechanisms.

The role of PGE2-associated inflammatory responses in gastric cancer development

Accumulating evidence indicates that inflammation plays a critical role in cancer development. Cyclooxygenase-2 (COX-2) is a rate-limiting enzyme for prostanoid biosynthesis, including prostaglandin E(2) (PGE(2)), and plays a key role in both inflammation and cancer. It has been demonstrated that inhibition of COX-2 and PGE(2) receptor signaling results in the suppression of tumor development in a variety of animal models. However, the molecular mechanisms underlying COX-2/PGE(2)-associated inflammation in carcinogenesis have not yet been fully elucidated. In order to study the role of PGE(2)-associated inflammatory responses in tumorigenesis, it is important to use in vivo mouse models that recapitulate human cancer development from molecular mechanisms with construction of tumor microenvironment. We have developed a gastritis model (K19-C2mE mice) in which an inflammatory microenvironment is constructed in the stomach via induction of the COX-2/PGE(2) pathway. We also developed a gastric cancer mouse model (Gan mice) in which the mice develop inflammation-associated gastric tumors via activation of both the COX-2/PGE(2) pathway and Wnt signaling. Expression analyses using these in vivo models have revealed novel mechanisms of the inflammatory responses underlying gastric cancer development. PGE(2)-associated inflammatory responses activate epidermal growth factor receptor (EGFR) signaling through the induction of EGFR ligands and ADAMs that release EGFR ligands from the cell membrane. In Gan mice, a combination treatment with EGFR and COX-2 inhibitors significantly suppresses gastric tumorigenesis. Moreover, PGE(2)-associated inflammation downregulates tumor suppressor microRNA, miR-7, in gastric cancer cells, which suppresses epithelial differentiation. These results indicate that PGE(2)-associated inflammatory responses promote in vivo gastric tumorigenesis via several different molecular mechanisms.