Overexpression of interleukin-1beta induces gastric inflammation and cancer and mobilizes myeloid-derived suppressor cells in mice

Interleukin-23 is sufficient to induce rapid de novo gut tumorigenesis, independent of carcinogens, through activation of innate lymphoid cells

Chronic inflammation has been associated with increased risk for developing gastrointestinal cancer. Interleukin-23 (IL-23) receptor signaling has been correlated with inflammatory bowel disease pathogenesis, as well as promotion of tumor growth. However, little is known about the relative potential for IL-23-directed causality in gut tumorigenesis. We report that IL-23 transgene expression was sufficient to induce rapid (3-4 weeks) de novo development of intestinal adenomas with 100% incidence. Initiation of tumorigenesis was independent of exogenous carcinogens, Helicobacter colonization, or pre-existing tumor-suppressor gene mutations. Tumorigenesis was mediated by Thy1(+)IL-23R(+) innate lymphoid cells (ILC3), in part, through IL-17 responses as tumor development was inhibited in RAG(-/-) × IL-17(-/-) double knockout mice. Remarkably, IL-23 initiation of tumorigenesis by resident ILCs consistently occurred before recruitment of conspicuous inflammatory infiltrates. Our results reveal an explicit role for IL-23-mediated initiation of gut tumorigenesis and implicate a key role for IL-23R(+) ILC3 in the absence of overt cellular infiltrate recruitment.

Advances in circulating microRNAs as diagnostic and prognostic markers for ovarian cancer

Ovarian cancer is one of the most lethal malignant gynecological tumors. More than 70% of patients with ovarian cancer are diagnosed at advanced stage. The 5-year survival in patients with advanced ovarian cancer is less than 30% because of the lack of effective biomarkers for diagnosis, prognosis, and personalized treatment. MicroRNA (miR) is a class of small noncoding RNAs that negatively regulate gene expression primarily through post-transcriptional repression. Many studies on tissue miR in ovarian cancer have been carried out and show great potential in clinical practice. However, tissue samples are not easily available because sampling causes injury. Researchers have started to focus on plasma/serum miR, assuming that blood samples may replace tissue samples in miR research in the future. Plasma/serum miR research is still in its early stages. Studies on its function in the early diagnosis of ovarian cancer have achieved some progress, but plasma/serum miR profiling for prognosis and personalized treatment of ovarian cancer remains unknown. A thorough understanding of the function of plasma/serum miR in ovarian cancer will facilitate early diagnosis and improve treatment for ovarian cancer.

STAT3 activation: A key factor in tumor immunoescape

Cancer growth is controlled by cancer cells (cell intrinsic phenomenon), but also by the immune cells in the tumor microenvironment (cell extrinsic phenomenon). Thus cancer progression is mediated by the activation of transcription programs responsible for cancer cell proliferation, but also induced proliferation/activation of immunosuppressive cells such as Th17, Treg or myeloid derived suppressor cells (MDSCs). One of the key transcription factors involved in these pathways is the signal transducer and activator of transcription 3 (STAT3). In this review we will focus on STAT3 activation in immune cells, and how it impacts on tumor progression.

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.

NF-κB and Nrf2 signaling pathways contribute to wogonin-mediated inhibition of inflammation-associated colorectal carcinogenesis

The transcriptional factors nuclear factor-κB (NF-κB) and NF-E2-related factor 2 (Nrf2) have been recently reported to have critical roles in protecting various tissues against inflammation and colitis-associated colorectal cancer (aberrant crypt foci). Our previous studies showed that wogonin (5,7-dihydroxy-8-methoxyflavone) possessed anti-neoplastic and anti-inflammatory activities. The present study extended these important earlier findings by exploring the effect of wogonin on the initiation and development of colitis-associated cancer. Wogonin lowered tumor incidence and inhibited the development of colorectal adenomas in azoxymethane- or dextran sulfate sodium-induced mice. We found that wogonin significantly decreased the secretion and expression of IL-6 and IL-1β, reduced cell proliferation and nuclear expression of NF-κB in adenomas and surrounding tissues and promoted Nrf2 nuclear translocation in surrounding tissues, although overexpressed Nrf2 in tumor tissues was independent of wogonin administration. Furthermore, wogonin inhibited the interaction between human monocytic THP-1 cells and human colon cancer HCT116 cells, and significantly downregulated lipopolysaccharide-induced secretion of prototypical pro-inflammatory cytokines IL-6 and IL-1β in THP-1 cells. Further mechanism research revealed that wogonin inhibited the nuclear translocation of NF-κB and phosphorylation of IκB and IKKα/β, and promoted Nrf2 signaling pathway in HCT116 cells and THP-1 cells. Taken together, the present results indicated that wogonin effectively suppressed inflammation-associated colon carcinogenesis and cancer development, suggesting its potential as a chemopreventive agent against colitis-associated colon cancer.

Macrophages promote progression of spasmolytic polypeptide-expressing metaplasia after acute loss of parietal cells

BACKGROUND & AIMS

Loss of parietal cells causes the development of spasmolytic polypeptide-expressing metaplasia (SPEM) through transdifferentiation of chief cells. In the presence of inflammation, SPEM can advance into a more proliferative metaplasia with increased expression of intestine-specific transcripts. We used L635 to induce acute SPEM with inflammation in mice and investigated the roles of inflammatory cells in the development of SPEM.

METHODS

To study the adaptive immune system, Rag1 knockout, interferon-γ-deficient, and wild-type (control) mice received L635 for 3 days. To study the innate immune system, macrophages were depleted by intraperitoneal injection of clodronate liposomes 2 days before and throughout L635 administration. Neutrophils were depleted by intraperitoneal injection of an antibody against Ly6G 2 days before and throughout L635 administration. Pathology and immunohistochemical analyses were used to determine depletion efficiency, metaplasia, and proliferation. To characterize SPEM in each model, gastric tissues were collected and levels of Cftr, Dmbt1, and Gpx2 mRNAs were measured. Markers of macrophage polarization were used to identify subpopulations of macrophages recruited to the gastric mucosa.

RESULTS

Administration of L635 to Rag1 knockout, interferon-γ-deficient, and neutrophil-depleted mice led to development of proliferative SPEM and up-regulation of intestine-specific transcripts in SPEM cells, similar to controls. However, macrophage-depleted mice given L635 showed significant reductions in numbers of SPEM cells, SPEM cell proliferation, and expression of intestine-specific transcripts, compared with control mice given L635. In mice given L635, as well as patients with intestinal metaplasia, M2 macrophages were the primary inflammatory component.

CONCLUSIONS

Results from studies of mouse models and human metaplastic tissues indicate that M2 macrophages promote the advancement of SPEM in the presence of inflammation.

Inhibition of the JAK2/STAT3 pathway reduces gastric cancer growth in vitro and in vivo

Signal Transducer and Activator of Transcription-3 (STAT3) is constitutively activated in many cancers where it promotes growth, inflammation, angiogenesis and inhibits apoptosis. We have shown that STAT3 is constitutively activated in human gastric cancer, and that chronic IL-11-driven STAT3 transcriptional activity induces gastric tumourigenesis in the gp130^757FF mouse model of gastric cancer development. Here we show that treatment of human AGS gastric cancer cells with the Janus Kinase (JAK) inhibitor WP1066 dose-, and time-dependently inhibits STAT3 phosphorylation, in conjunction with reduced JAK2 phosphorylation, reduced proliferation and increased apoptosis. In addition, application of intraperitoneal WP1066 for 2 weeks, reduced gastric tumour volume by 50% in the gp130^757FF mouse coincident with reduced JAK2 and STAT3 activation compared with vehicle-treated, littermate controls. Gastric tumours from WP1066- treated mice had reduced polymorphonuclear inflammation, coincident with inhibition of numerous proinflammatory cytokines including IL-11, IL-6 and IL-1β, as well as the growth factors Reg1 and amphiregulin. These results show that WP1066 can block proliferation, reduce inflammation and induce apoptosis in gastric tumour cells by inhibiting STAT3 phosphorylation, and that many cytokines and growth factors that promote gastric tumour growth are regulated by STAT3-dependent mechanisms. WP1066 may form the basis for future therapeutics against gastric cancer.

Minimal changes in the systemic immune response after nephrectomy of localized renal masses

OBJECTIVES

Renal cell carcinoma (RCC) is an immunogenic tumor, and multiple immunostimulatory therapies are in use or under development for patients with inoperable tumors. However, a major drawback to the use of immunotherapy for RCC is that renal tumors are also immunosuppressive. As a result, current immunotherapies are curative in<10% of patients with RCC. To better understand the systemic immune response to RCC, we performed a comprehensive examination of the leukocyte and cytokine/chemokine composition in the peripheral blood of patients with localized clear cell renal tumors pre- and post-nephrectomy.

METHODS AND MATERIALS

Peripheral blood samples were taken from 53 consented subjects with renal masses before cytoreductive nephrectomy and again at clinic visits approximately 30 days after nephrectomy. Samples were also obtained from 10 healthy age- and gender-matched controls. Blood samples from clear cell RCC subjects were analyzed by multi-parameter flow cytometry to determine leukocyte subset composition and multiplex array to evaluate plasma proteins.

RESULTS

Pre-nephrectomy, clear cell tumors were associated with systemic accumulations of both "exhausted" CD8+ T cells, as indicated by surface BTLA expression, and monocytic CD14(+)HLA-DR(neg)CD33(+) myeloid-derived suppressor cells (MDSC). Subjects with T3 clear cell RCC also had a unique pro-tumorigenic and inflammatory cytokine/chemokine profile characterized by high serum concentrations of IL-1β, IL-2, IL-5, IL-7, IL-8, IL-17, TNF-α, MCP-1 and MIP-1β. At an early post-nephrectomy time point (~30 d), we found the systemic immune response to be largely unaltered. The only significant change was a decrease in the mean percentage of circulating BTLA(+)CD8(+) T cells. All other cellular and soluble immune parameters we examined were unaltered by the removal of the primary tumor.

CONCLUSIONS

In the first month following surgery, nephrectomy may relieve systemic CD8 T cell exhaustion marked by BTLA expression, but continuing inflammation and MDSC presence likely counteract this positive effect. Future determination of how this systemic immune signature becomes altered during metastatic progression could provide novel targets for neoadjuvant immunotherapy in RCC.

Nod-like receptors: key molecular switches in the conundrum of cancer

It is believed the immune system can contribute to oncogenic transformation especially in settings of chronic inflammation, be activated during immunosurveillance to destroy early neoplastic cells before they undergo malignant outgrowth, and finally, can assist growth of established tumors by preventing clearance, remodeling surrounding tissue, and promoting metastatic events. These seemingly opposing roles of the immune system at the different stages of cancer development must all be mediated by innate signaling mechanisms that regulate the overall state of immune activation. Recently, the cytosolic nod-like receptor (NLR) pathway of innate immunity has gained a lot of attention in the tumor immunology field due to its known involvement in promoting inflammation and immunity, and conversely, in regulating tissue repair processes. In this review, we present all the current evidence for NLR involvement in the different stages of neoplasia to understand how a single molecular pathway can contribute to conflicting immunological interactions with cancer.

Serum amyloid A3 exacerbates cancer by enhancing the suppressive capacity of myeloid-derived suppressor cells via TLR2-dependent STAT3 activation

Myeloid-derived suppressor cells (MDSCs), which suppress diverse innate and adaptive immune responses and thereby provide an evasion mechanism for tumors, are emerging as a key population linking inflammation to cancer. Although many inflammatory factors that induce MDSCs in the tumor microenvironment are known, the crucial components and the underlying mechanisms remain elusive. In this study, we proposed a novel mechanism by which serum amyloid A3 (SAA3), a well-known inflammatory factor, connects MDSCs with cancer progression. We found that SAA3 expression in BALB/c mice increased in monocytic MDSCs (Mo MDSCs) with tumor growth. The induction of SAA3 by apo-SAA treatment in Mo MDSCs enhanced their survival and suppressive activity, while it inhibited GM-CSF-induced differentiation. Endogenous SAA3 itself contributed to the increase in the survival and suppressive activity of Mo MDSCs. We demonstrated that SAA3 induced TLR2 signaling, in turn increasing the autocrine secretion of TNF-α, that led to STAT3 activation. In addition, activated STAT3 enhanced the suppressive activity of Mo MDSCs. Furthermore, SAA3 induction in Mo MDSCs contributed to accelerating tumor progression in vivo. Collectively, these data suggest a novel mechanism by which Mo MDSCs mediate inflammation through SAA3-TLR2 signaling and thus exacerbate cancer progression by a STAT3-dependent mechanism.

Signaling pathways involved in MDSC regulation

The immune system has evolved mechanisms to protect the host from the deleterious effects of inflammation. The generation of immune suppressive cells like myeloid derived suppressor cells (MDSCs) that can counteract T cell responses represents one such strategy. There is an accumulation of immature myeloid cells or MDSCs in bone marrow (BM) and lymphoid organs under pathological conditions such as cancer. MDSCs represent a population of heterogeneous myeloid cells comprising of macrophages, granulocytes and dendritic cells that are at early stages of development. Although, the precise signaling pathways and molecular mechanisms that lead to MDSC generation and expansion in cancer remains to be elucidated. It is widely believed that perturbation of signaling pathways involved during normal hematopoietic and myeloid development under pathological conditions such as tumorogenesis contributes to the development of suppressive myeloid cells. In this review we discuss the role played by key signaling pathways such as PI3K, Ras, Jak/Stat and TGFb during myeloid development and how their deregulation under pathological conditions can lead to the generation of suppressive myeloid cells or MDSCs. Targeting these pathways should help in elucidating mechanisms that lead to the expansion of MDSCs in cancer and point to methods for eliminating these cells from the tumor microenvironment.

Myeloid-derived suppressor cells: the dark knight or the joker in viral infections?

Myeloid derived suppressor cells (MDSCs) are immature cells of myeloid origin, frequently found in tumor microenvironments and in the blood of cancer patients. In recent years, MDSCs have also been found in non-cancer settings, including a number of viral infections. The evasion of host immunity employed by viruses to establish viral persistence strikingly parallels mechanisms of tumor escape, prompting investigations into the generation and function of MDSCs in chronic viral infections. Importantly, analogous to the tumor microenvironment, MDSCs effectively suppress antiviral host immunity by limiting the function of several immune cells including T cells, natural killer cells, and antigen-presenting cells. In this article, we review studies on the mechanisms of MDSC generation, accumulation, and survival in an effort to understand their emergent importance in viral infections. We include a growing list of viral infections in which MDSCs have been reported. Finally, we discuss how MDSCs might play a role in establishing chronic viral infections and identify potential therapeutics that target MDSCs.

Multifocal epithelial tumors and field cancerization: stroma as a primary determinant

It is increasingly evident that cancer results from altered organ homeostasis rather than from deregulated control of single cells or groups of cells. This applies especially to epithelial cancer, the most common form of human solid tumors and a major cause of cancer lethality. In the vast majority of cases, in situ epithelial cancer lesions do not progress into malignancy, even if they harbor many of the genetic changes found in invasive and metastatic tumors. While changes in tumor stroma are frequently viewed as secondary to changes in the epithelium, recent evidence indicates that they can play a primary role in both cancer progression and initiation. These processes may explain the phenomenon of field cancerization, i.e., the occurrence of multifocal and recurrent epithelial tumors that are preceded by and associated with widespread changes of surrounding tissue or organ "fields."

The role IL-1 in tumor-mediated angiogenesis

Tumor angiogenesis is one of the hallmarks of tumor progression and is essential for invasiveness and metastasis. Myeloid inflammatory cells, such as immature myeloid precursor cells, also termed myeloid-derived suppressor cells (MDSCs), neutrophils, and monocytes/macrophages, are recruited to the tumor microenvironment by factors released by the malignant cells that are subsequently “educated” in situ to acquire a pro-invasive, pro-angiogenic, and immunosuppressive phenotype. The proximity of myeloid cells to endothelial cells (ECs) lining blood vessels suggests that they play an important role in the angiogenic response, possibly by secreting a network of cytokines/chemokines and inflammatory mediators, as well as via activation of ECs for proliferation and secretion of pro-angiogenic factors. Interleukin-1 (IL-1) is an “alarm,” upstream, pro-inflammatory cytokine that is generated primarily by myeloid cells. IL-1 initiates and propagates inflammation, mainly by inducing a local cytokine network and enhancing inflammatory cell infiltration to affected sites and by augmenting adhesion molecule expression on ECs and leukocytes. Pro-inflammatory mediators were recently shown to play an important role in tumor-mediated angiogenesis and blocking their function may suppress tumor progression. In this review, we summarize the interactions between IL-1 and other pro-angiogenic factors during normal and pathological conditions. In addition, the feasibility of IL-1 neutralization approaches for anti-cancer therapy is discussed.

Pten null prostate epithelium promotes localized myeloid-derived suppressor cell expansion and immune suppression during tumor initiation and progression

Chronic inflammation is known to be associated with prostate cancer development, but how epithelium-associated cancer-initiating events cross talk to inflammatory cells during prostate cancer initiation and progression is largely unknown. Using the Pten null murine prostate cancer model, we show an expansion of Gr-1(+) CD11b(+) myeloid-derived suppressor cells (MDSCs) occurring intraprostatically immediately following epithelium-specific Pten deletion without expansion in hematopoietic tissues. This MDSC expansion is accompanied by sustained immune suppression. Prostatic Gr-1(+) CD11b(+) cells, but not those isolated from the spleen of the same tumor-bearing mice, suppress T cell proliferation and express high levels of Arginase 1 and iNOS. Mechanistically, the loss of PTEN in the epithelium leads to a significant upregulation of genes within the inflammatory response and cytokine-cytokine receptor interaction pathways, including Csf1 and Il1b, two genes known to induce MDSC expansion and immunosuppressive activities. Treatment of Pten null mice with the selective CSF-1 receptor inhibitor GW2580 decreases MDSC infiltration and relieves the associated immunosuppressive phenotype. Our study indicates that epithelium-associated tumor-initiating events trigger the secretion of inflammatory cytokines and promote localized MDSC expansion and immune suppression, thereby promoting tumor progression.

Autoimmunity as a double agent in tumor killing and cancer promotion

Cancer immunotherapy through manipulation of the immune system holds great potential for the treatment of human cancers. However, recent trials targeting the negative immune regulators cytotoxic T-lymphocyte antigen 4, programed death 1 (PD-1), and PD-1 receptor ligand (PD-L1) demonstrated that clinically significant antitumor responses were often associated with the induction of autoimmune toxicity. This finding suggests that the same immune mechanisms that elicit autoimmunity may also contribute to the destruction of tumors. Given the fact that the immunological identity of tumors might be largely an immunoprivileged self, autoimmunity may not represent a wholly undesirable outcome in the context of cancer immunotherapy. Rather, targeted killing of cancer cells and autoimmune damage to healthy tissues may be intricately linked through molecular mechanisms, in particular inflammatory cytokine signaling. On the other hand, since chronic inflammation is a well-recognized condition that promotes tumor development, it appears that autoimmunity can be a "double agent" in mediating either pro-tumor or antitumor effects. This review surveys the tumor-promoting and tumoricidal activities of several prominent cytokines: IFN-γ, TNF-α, TGF-β, IL-17, IL-23, IL-4, and IL-13, produced by three major subsets of T helper cells that interact with innate immune cells. Many of these cytokines exert divergent and seemingly contradictory effects on cancer development in different human and animal models, suggesting a high degree of context dependence in their functions. We hypothesize that these inflammatory cytokines could mediate a feedback loop of autoimmunity, antitumor immunity, and tumorigenesis. Understanding the diverse and paradoxical roles of cytokines from autoimmune responses in the setting of cancer will advance the long-term goal of improving cancer immunotherapy, while minimizing the hazards of immune-mediated tissue damage and the possibility of de novo tumorigenesis, through proper monitoring and preventive measures.

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.

Obesity accelerates Helicobacter felis-induced gastric carcinogenesis by enhancing immature myeloid cell trafficking and TH17 response

OBJECTIVE

To investigate the role of obesity-associated inflammation and immune modulation in gastric carcinogenesis during Helicobacter-induced chronic gastric inflammation.

DESIGN

C57BL/6 male mice were infected with H felis and placed on a high-fat diet (45% calories from fat). Study animals were analysed for gastric and adipose pathology, inflammatory markers in serum, stomach and adipose tissue, and immune responses in blood, spleen, stomach and adipose tissue.

RESULTS

H felis-induced gastric carcinogenesis was accelerated in diet-induced obese mice compared with lean controls. Obesity increased bone marrow-derived immature myeloid cells in blood and gastric tissue of H felis-infected mice. Obesity also led to elevations in CD4 T cells, IL-17A, granulocyte macrophage colony-stimulating factor, phosphorylated STAT3 and prosurvival gene expression in gastric tissue of H felis-infected mice. Conversely, in adipose tissue of obese mice, H felis infection increased macrophage accumulation and expression of IL-6, C-C motif ligand 7 (CCL7) and leptin. Finally, the combination of obesity and gastric inflammation synergistically increased serum proinflammatory cytokines, including IL-6.

CONCLUSIONS

Here, we have established a model to study the molecular mechanism by which obesity predisposes individuals to gastric cancer. In H felis-infected mice, obesity increased proinflammatory immune responses and accelerated gastric carcinogenesis. Interestingly, gastric inflammation augmented obesity-induced adipose inflammation and production of adipose-derived factors in obese, but not lean, mice. Our findings suggest that obesity accelerates Helicobacter-associated gastric cancer through cytokine-mediated cross-talk between inflamed gastric and adipose tissues, augmenting immune responses at both tissue sites, and thereby contributing to a protumorigenic gastric microenvironment.

NF-κB in cellular senescence and cancer treatment

The NF-κB pathway transcriptionally controls a large set of target genes that play important roles in cell survival, inflammation, and immune responses. While many studies showed anti-tumorigenic and pro-survival role of NF-κB in cancer cells, recent findings postulate that NF-κB participates in a senescence-associated cytokine response, thereby suggesting a tumor restraining role of NF-κB. In this review, we discuss implications of the NF-κB signaling pathway in cancer. Particularly, we emphasize the connection of NF-κB with cellular senescence as a response to chemotherapy, and furthermore, present examples how distinct oncogenic network contexts surrounding NF-κB produce fundamentally different treatment outcomes in aggressive B-cell lymphomas as an example.

Cell-death-associated molecular patterns as determinants of cancer immunogenicity

SIGNIFICANCE

Accumulating evidence indicates that the success of some anticancer treatments (select chemotherapies or radiotherapy or trastuzumab) could be related to the stimulation of an anticancer immune response through the induction of an immunogenic tumor cell death (ICD).

RECENT ADVANCES

Preclinical data revealed that dying tumor cells can emit a series of danger signals (so-called "cell-death-associated molecular patterns" (CDAMP)) that will dictate the recruitment and activation of specific inflammatory phagocytes. Hence, tumor cells succumbing to ICD are characterized by specific metabolic and molecular changes that will trigger a hierarchy of polarizing cytokine-producing cells, culminating in the recruitment and reactivation of antitumor interferon-γ-producing effector T cells which contribute to the success of cytotoxic treatments.

CRITICAL ISSUES

In this review, we summarize the molecular and cellular bases of this ICD, underscoring the crucial role of high mobility group box 1 protein (HMGB1) and adenosine tri-phosphate, both of which are released from dying tumor cells during ICD and are implicated in the chemotherapy-elicited anticancer immune response.

FUTURE DIRECTIONS

We discuss here how such CDAMP could serve as predictive biomarkers that could discriminate immunogenic from nonimmunogenic anti-cancer compounds, and, in case of deficiency, could be compensated by surrogate products to ameliorate the success rate of conventional anticancer treatment modalities.

Increased expression of IL17A in human gastric cancer and its potential roles in gastric carcinogenesis

Inflammatory cytokines modulate immune responses in the tumor microenvironment during progression. The role of interleukin (IL) 17A in cancer is currently under debate. We aim to investigate the expression of IL17A in situ tumors as well as in nontumor gastric mucosa tissues and further explore the functional significance of IL17A on gastric cancer cells in vitro. We found that compared with nontumor regions, the expression of IL17A were increased significantly in tumors of gastric cancer patients (P=0.007). The immunoreactivity for IL17A was found only in cytoplasm of inflammatory cells as well as vascular endothelial cells but not in tumor cells. Consistently, IL17A transcription was silenced in a variety of gastric cancer cell lines. In vitro, recombinant human IL17A protein promotes cell proliferation and monolayer wound healing of both AGS and SGC7901cells, in a dose-dependent manner. Besides, IL17A inhibits H2O2-induced cell apoptosis. Expression of IL6 and MMP13 mRNA was increased significantly after IL17A stimulation. These data suggest that accumulation of intratumoral IL17A-producing cells may promote gastric cancer progression directly or by inducing key signal transduction pathways implicated in gastric carcinogenesis.

Inflammasomes in cancer: a double-edged sword

Chronic inflammatory responses have long been observed to be associated with various types of cancer and play decisive roles at different stages of cancer development. Inflammasomes, which are potent inducers of interleukin (IL)-1β and IL-18 during inflammation, are large protein complexes typically consisting of a Nod-like receptor (NLR), the adapter protein ASC, and Caspase-1. During malignant transformation or cancer therapy, the inflammasomes are postulated to become activated in response to danger signals arising from the tumors or from therapy-induced damage to the tumor or healthy tissue. The activation of inflammasomes plays diverse and sometimes contrasting roles in cancer promotion and therapy depending on the specific context. Here we summarize the role of different inflammasome complexes in cancer progression and therapy. Inflammasome components and pathways may provide novel targets to treat certain types of cancer; however, using such agents should be cautiously evaluated due to the complex roles that inflammasomes and pro-inflammatory cytokines play in immunity.

Dietary factors modulate Helicobacter-associated gastric cancer in rodent models

Since its discovery in 1982, the global importance of Helicobacter pylori-induced disease, particularly in developing countries, remains high. The use of rodent models, particularly mice, and the unanticipated usefulness of the gerbil to study H. pylori pathogenesis have been used extensively to study the interactions of the host, the pathogen, and the environmental conditions influencing the outcome of persistent H. pylori infection. Dietary factors in humans are increasingly recognized as being important factors in modulating progression and severity of H. pylori-induced gastric cancer. Studies using rodent models to verify and help explain mechanisms whereby various dietary ingredients impact disease outcome should continue to be extremely productive.

Transmembrane TNF-α promotes suppressive activities of myeloid-derived suppressor cells via TNFR2

It has been reported that TNFR2 is involved in regulatory T cell induction and myeloid-derived suppressor cell (MDSC) accumulation, two kinds of immunosuppressive cells contributing to tumor immune evasion. Because transmembrane TNF-α (tmTNF-α) is the primary ligand for TNFR2, we hypothesized that tmTNF-α is mainly responsible for the activation of MDSCs. Indeed, we found that tmTNF-α, rather than secretory TNF-α (sTNF-α), activated MDSCs with enhanced suppressive activities, including upregulating arginase-1 and inducible NO synthase transcription, promoting secretion of NO, reactive oxygen species, IL-10, and TGF-β, and enhancing inhibition of lymphocyte proliferation. This effect of tmTNF-α was mediated by TNFR2, as TNFR2 deficiency significantly impaired tmTNF-α-induced release of IL-10 and NO and inhibition of T cell proliferation by MDSC supernatant. Furthermore, tmTNF-α caused p38 phosphorylation and NF-κB activation, whereas inhibition of NF-κB or p38 with an inhibitor pyrrolidine dithiocarbamate or SB203580 abrogated tmTNF-α-mediated increased suppression of lymphocyte proliferation by MDSCs. Consistently, our in vivo study showed that ectopic expression of uncleavable tmTNF-α mutant by 4T1 cells significantly promoted tumor progression and angiogenesis, accompanied with more accumulation of MDSCs and regulatory T cells in the tumor site, increased production of NO, IL-10, and TGF-β, as well as poor lymphocyte infiltration. In contrast, enforced expression of sTNF-α mutant by 4T1 cells that only released sTNF-α without expression of surface tmTNF-α markedly reduced MDSC accumulation and induced more lymphocyte infiltration instead, showing obvious tumor regression. Our data suggest that tmTNF-α acts as a potent activator of MDSCs via TNFR2 and reveals another novel immunosuppressive effect of this membrane molecule that promotes tumor immune escape.

Licensing Adaptive Immunity by NOD-Like Receptors

The innate immune system is composed of a diverse set of host defense molecules, physical barriers, and specialized leukocytes and is the primary form of immune defense against environmental insults. Another crucial role of innate immunity is to shape the long-lived adaptive immune response mediated by T and B lymphocytes. The activation of pattern recognition receptors (PRRs) from the Toll-like receptor family is now a classic example of innate immune molecules influencing adaptive immunity, resulting in effective antigen presentation to naïve T cells. More recent work suggests that the activation of another family of PRRs, the NOD-like receptors (NLRs), induces a different set of innate immune responses and accordingly, drives different aspects of adaptive immunity. Yet how this unusually diverse family of molecules (some without canonical PRR function) regulates immunity remains incompletely understood. In this review, we discuss the evidence for and against NLR activity orchestrating adaptive immune responses during infectious as well as non-infectious challenges.

Analysis of cell hyperplasia and parietal cell dysfunction induced by Ostertagia ostertagi infection

Infections in cattle with the gastric nematode Ostertagia ostertagi are associated with decreased acid secretion and profound physio-morphological changes of the gastric mucosa. The purpose of the current study was to investigate the mechanisms triggering these pathophysiological changes. O. ostertagi infection resulted in a marked cellular hyperplasia, which can be explained by increased transcriptional levels of signaling molecules related to the homeostasis of gastric epithelial cells such as HES1, WNT5A, FGF10, HB-EGF, AREG, ADAM10 and ADAM17. Intriguingly, histological analysis indicated that the rapid rise in the gastric pH, observed following the emergence of adult worms, cannot be explained by a loss of parietal cells, as a decrease in the number of parietal cells was only observed following a long term infection of several weeks, but is likely to be caused by an inhibition of parietal cell activity. To investigate whether this inhibition is caused by a direct effect of the parasites, parietal cells were co-cultured with parasite Excretory/Secretory products (ESP) and subsequently analyzed for acid production. The results indicate that adult ESP inhibited acid secretion, whereas ESP from the L4 larval stages did not alter parietal cell function. In addition, our data show that the inhibition of parietal cell activity could be mediated by a marked upregulation of inflammatory factors, which are partly induced by adult ESP in abomasal epithelial cells. In conclusion, this study shows that the emergence of adult O. ostertagi worms is associated with marked cellular changes that can be partly triggered by the worm’s Excretory/secretory antigens.

Comparison of experimental mouse models of inflammatory bowel disease

Inflammatory bowel disease (IBD) is multifactorial and involves immunological, environmental and genetic factors. Although there are no animal models that effectively mimic human IBD, experimental models allow us to analyze the mechanisms of chronic intestinal inflammation. IBD can be induced in mice by dextran sulfate sodium (DSS) or by a 2,4,6-trinitrobenzene sulfonic acid (TNBS)‑ethanol enema, which evoke immune responses and colitis. In this study, in order to compare the mechanisms of inflammatory response in mice, 3 distinct models of IBD were established: 2% TNBS-induced acute colitis, 4% DSS-induced acute colitis and 2% DSS-induced chronic colitis. In addition, to evaluate the effects of TNBS on inflammasome activation, we used caspase-1 knockout (KO) mice. Changes in both body weight and survival became prominent after day 1 in the 2% TNBS‑induced colitis model, and after day 5 in the 4% DSS-induced colitis model. The TNBS- and DSS-treated mice, but not the caspase-1 KO mice, showed a massive bowel edema and disruption of epithelial cells. The level of CD11b(+)Gr-1(+) myeloid-derived suppressor cells (MDSCs) was increased in all tested tissues of the TNBS- and DSS-treated groups, apart from the basal membrane (BM) in the DSS-induced colitis groups and the lamina propria (LP) in the DSS-induced chronic colitis group. We further analyzed different subsets of CD4(+) T cells in LP and found that the levels of interferon (IFN)γ‑secreting (IFNγ(+)), IL-17‑secreting (IL-17(+)), but not those of IL-4-secreting (IL-4(+)) T cells increased upon treatment with TNBS or DSS. In addition, discrepancies between the histopathologies of wild-type and caspase-1 KO mice indicated that the pathogenesis of IBD may be associated with the inflammasome pathway responses mediated by caspase‑1 in TNBS‑induced colitis.

Progress in understanding the association between interleukin-1B gene polymorphisms and susceptibility to gastric cancer

Gastric cancer is one of severe diseases threatening human health and has a close association with Helicobacter pylori infection. Interleukin-1B (IL-1B) gene polymorphisms have been suggested to be associated with susceptibility to gastric cancer; however, there is still controversy over this point of view. In this paper we will summarize recent progress in understanding the association between IL-1B gene polymorphisms and susceptibility to gastric cancer in population in different areas or of different races

Mycoplasma hyorhinis activates the NLRP3 inflammasome and promotes migration and invasion of gastric cancer cells

BACKGROUND

Mycoplasma hyorhinis (M.hyorhinis, M.hy) is associated with development of gastric and prostate cancers. The NLRP3 inflammasome, a protein complex controlling maturation of important pro-inflammatory cytokines interleukin (IL)-1β and IL-18, is also involved in tumorigenesis and metastasis of various cancers.

METHODOLOGY/PRINCIPAL FINDINGS

To clarify whether M.hy promoted tumor development via inflammasome activation, we analyzed monocytes for IL-1β and IL-18 production upon M.hy challenge. When exposed to M.hy, human monocytes exhibited rapid and robust IL-1β and IL-18 secretion. We further identified that lipid-associated membrane protein (LAMP) from M.hy was responsible for IL-1β induction. Applying competitive inhibitors, gene specific shRNA and gene targeted mice, we verified that M.hy induced IL-1β secretion was NLRP3-dependent in vitro and in vivo. Cathepsin B activity, K(+) efflux, Ca(2+) influx and ROS production were all required for the NLRP3 inflammasome activation by M.hy. Importantly, it is IL-1β but not IL-18 produced from macrophages challenged with M.hy promoted gastric cancer cell migration and invasion.

CONCLUSIONS

Our data suggest that activation of the NLRP3 inflammasome by M.hy may be associated with its promotion of gastric cancer metastasis, and anti-M.hy therapy or limiting NLRP3 signaling could be effective approach for control of gastric cancer progress.

The role of the gastrointestinal microbiome in Helicobacter pylori pathogenesis

The discovery of Helicobacter pylori overturned the conventional dogma that the stomach was a sterile organ and that pH values<4 were capable of sterilizing the stomach. H. pylori are an etiological agent associated with gastritis, hypochlorhydria, duodenal ulcers, and gastric cancer. It is now appreciated that the human stomach supports a bacterial community with possibly 100s of bacterial species that influence stomach homeostasis. Other bacteria colonizing the stomach may also influence H. pylori-associated gastric pathogenesis by creating reactive oxygen and nitrogen species and modulating inflammatory responses. In this review, we summarize the available literature concerning the gastric microbiota in humans, mice, and Mongolian gerbils. We also discuss the gastric perturbations, many involving H. pylori, that facilitate the colonization by bacteria from other compartments of the gastrointestinal tract, and identify risk factors known to affect gastric homeostasis that contribute to changes in the microbiota.

IL-1β, RAGE and FABP4: targeting the dynamic trio in metabolic inflammation and related pathologies

Within the past decade, inflammatory and lipid mediators, such as IL-1β, FABP4 and RAGE, have emerged as important contributors to metabolic dysfunction. As growing experimental and clinical evidence continues to tie obesity-induced chronic inflammation with dysregulated lipid, insulin signaling and related pathologies, IL-1β, FABP4 and RAGE each are being independently implicated as culprits in these events. There are also convincing data that molecular pathways driven by these molecules are interconnected in exacerbating metabolic consequences of obesity. This article highlights the roles of IL-1β, FABP4 and RAGE in normal physiology as well as focusing specifically on their contribution to inflammation, insulin resistance, atherosclerosis, Type 2 diabetes and cancer. Studies implicating the interconnection between these pathways, current and emerging therapeutics, and their use as potential biomarkers are also discussed. Evidence of impact of IL-1β, FABP4 and RAGE pathways on severity of metabolic dysfunction underlines the strong links between inflammatory events, lipid metabolism and insulin regulation, and offers new intriguing approaches for future therapies of obesity-driven pathologies.

Bone marrow-derived myofibroblasts promote colon tumorigenesis through the IL-6/JAK2/STAT3 pathway

Bone marrow-derived myofibroblasts (BMFs) have been shown to promote tumor growth. Here, we found that BMFs or BMF conditioned medium (BMF-CM) induced cancer stem cell-like sphere formation of colon cancer cells. The co-cultured BMFs, but not co-cultured cancer cells, expressed higher levels of IL-6 than BMFs or cancer cells cultured alone. Anti-mouse IL-6 neutralizing antibody, JAK2 inhibitors and STAT3 knockdown in mouse cancer cells reduced BMF- and BMF-CM-induced sphere formation of colon cancer cells. When co-injected, BMFs significantly enhanced tumorigenesis of colon cancer cells in mice. Our results demonstrate that BMFs promote tumorigenesis via the activation of the IL-6/JAK2/STAT3 pathway.

Interleukin-6 is required for pancreatic cancer progression by promoting MAPK signaling activation and oxidative stress resistance

Pancreatic cancer, one of the deadliest human malignancies, is almost invariably associated with the presence of an oncogenic form of Kras. Mice expressing oncogenic Kras in the pancreas recapitulate the stepwise progression of the human disease. The inflammatory cytokine interleukin (IL)-6 is often expressed by multiple cell types within the tumor microenvironment. Here, we show that IL-6 is required for the maintenance and progression of pancreatic cancer precursor lesions. In fact, the lack of IL-6 completely ablates cancer progression even in presence of oncogenic Kras. Mechanistically, we show that IL-6 synergizes with oncogenic Kras to activate the reactive oxygen species detoxification program downstream of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling cascade. In addition, IL-6 regulates the inflammatory microenvironment of pancreatic cancer throughout its progression, providing several signals that are essential for carcinogenesis. Thus, IL-6 emerges as a key player at all stages of pancreatic carcinogenesis and a potential therapeutic target.

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.

Loss of SHP-2 activity in CD4+ T cells promotes melanoma progression and metastasis

The Src homology 2 domain-containing tyrosine phosphatase 2 (SHP-2) has been reported to have both tumor-promoting and tumor-suppressing roles in tumorigenesis. However, the role of SHP-2 in tumor immunity remains unclear. Here we observed progressively lower levels of phosphorylated SHP-2 in tumor-associated CD4⁺ T cells during melanoma development in a murine model. Similarly, the levels of phosphorylated SHP-2 in the CD4⁺ T cells of human melanoma specimens revealed a decrease paralleling cancer development. The CD4⁺ T cell-specific deletion of SHP-2 promoted melanoma metastasis in mice. Furthermore, SHP-2 deficiency in CD4⁺ T cells resulted in the increased release of inflammatory cytokines, especially IL-6, and the enhanced accumulation of tumor-promoting myeloid-derived suppressor cells (MDSCs) in tumor-bearing mice. An IL-6-neutralizing antibody reduced MDSC accumulation and inhibited tumor growth in CD4⁺ T-cell-specific SHP-2-knockout mice. Our results suggest that SHP-2 in CD4⁺ T cells plays an important role in preventing melanoma progression and metastasis.

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.

Myeloid-derived suppressor cell development is regulated by a STAT/IRF-8 axis

Myeloid-derived suppressor cells (MDSCs) comprise immature myeloid populations produced in diverse pathologies, including neoplasia. Because MDSCs can impair antitumor immunity, these cells have emerged as a significant barrier to cancer therapy. Although much research has focused on how MDSCs promote tumor progression, it remains unclear how MDSCs develop and why the MDSC response is heavily granulocytic. Given that MDSCs are a manifestation of aberrant myelopoiesis, we hypothesized that MDSCs arise from perturbations in the regulation of interferon regulatory factor-8 (IRF-8), an integral transcriptional component of myeloid differentiation and lineage commitment. Overall, we demonstrated that (a) Irf8-deficient mice generated myeloid populations highly homologous to tumor-induced MDSCs with respect to phenotype, function, and gene expression profiles; (b) IRF-8 overexpression in mice attenuated MDSC accumulation and enhanced immunotherapeutic efficacy; (c) the MDSC-inducing factors G-CSF and GM-CSF facilitated IRF-8 downregulation via STAT3- and STAT5-dependent pathways; and (d) IRF-8 levels in MDSCs of breast cancer patients declined with increasing MDSC frequency, implicating IRF-8 as a negative regulator in human MDSC biology. Together, our results reveal a previously unrecognized role for IRF-8 expression in MDSC subset development, which may provide new avenues to target MDSCs in neoplasia.

Sox2 cooperates with inflammation-mediated Stat3 activation in the malignant transformation of foregut basal progenitor cells

Sox2 regulates the self-renewal of multiple types of stem cells. Recent studies suggest it also plays oncogenic roles in the formation of squamous carcinoma in several organs, including the esophagus where Sox2 is predominantly expressed in the basal progenitor cells of the stratified epithelium. Here, we use mouse genetic models to reveal a mechanism by which Sox2 cooperates with microenvironmental signals to malignantly transform epithelial progenitor cells. Conditional overexpression of Sox2 in basal cells expands the progenitor population in both the esophagus and forestomach. Significantly, carcinoma only develops in the forestomach, where pathological progression correlates with inflammation and nuclear localization of Stat3 in progenitor cells. Importantly, co-overexpression of Sox2 and activated Stat3 (Stat3C) also transforms esophageal basal cells but not the differentiated suprabasal cells. These findings indicate that basal stem/progenitor cells are the cells of origin of squamous carcinoma and that cooperation between Sox2 and microenvironment-activated Stat3 is required for Sox2-driven tumorigenesis.

An inflammatory situation: SOX2 and STAT3 cooperate in squamous cell carcinoma initiation

Although SOX2 has been identified as a squamous cell carcinoma oncogene, mechanisms of SOX2-induce oncogenesis have remained elusive. In this issue of Cell Stem Cell, Li et al. (2013) show that SOX2 synergizes with inflammation-induced STAT3 activation to transform basal progenitors and initiate squamous cell carcinoma.

Signaling mediated by the NF-κB sub-units NF-κB1, NF-κB2 and c-Rel differentially regulate Helicobacter felis-induced gastric carcinogenesis in C57BL/6 mice

The classical nuclear factor-kappaB (NF-κB) signaling pathway has been shown to be important in a number of models of inflammation-associated cancer. In a mouse model of Helicobacter-induced gastric cancer, impairment of classical NF-κB signaling in the gastric epithelium led to the development of increased preneoplastic pathology, however the role of specific NF-κB proteins in Helicobacter-associated gastric cancer development remains poorly understood. To investigate this C57BL/6, Nfkb1^−/−, Nfkb2^−/− and c-Rel^−/− mice were infected with Helicobacter felis for 6 weeks or 12 months. Bacterial colonization, gastric atrophy and preneoplastic changes were assessed histologically and cytokine expression was assessed by qPCR. Nfkb1^−/− mice developed spontaneous gastric atrophy when maintained for 12 months in conventional animal house conditions. They also developed more pronounced gastric atrophy after short-term H. felis colonization with a similar extent of preneoplasia to wild-type (WT) mice after 12 months. c-Rel^−/− mice developed a similar degree of gastric atrophy to WT mice; 3 of 6 of these animals also developed lymphoproliferative lesions after 12 months of infection. Nfkb2^−/− mice developed minimal gastric epithelial pathology even 12 months after H. felis infection. These findings demonstrate that NF-κB1- and NF-κB2-mediated signaling pathways differentially regulate the epithelial consequences of H. felis infection in the stomach, while c-Rel-mediated signaling also appears to modulate the risk of lymphomagenesis in gastric mucosa-associated lymphoid tissue.

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.

Activation of the NF-kB pathway downregulates TFF-1 in gastric carcinogenesis

Trefoil factor 1 (TFF1) is expressed in the normal superficial epithelium of the stomach and is implicated in the maintenance of gastric epithelial structure and function. During gastric carcinogenesis, in which pro-inflammatory cytokines play a crucial role, its expression level decreases suggesting a role as tumor suppressor factor. We have compared expression of TFF1 in gastric mucosa from cancer patients, in which several degrees of inflammatory infiltrate are present, with that in normal mucosa from non-cancer patients without infiltrating inflammatory cells. TFF1 is less expressed in the superficial gastric epithelium from cancer patients than in that from normal individuals in which the nuclear factor (NF)-κB pathway is not activated. We analyzed TFF1 expression in ex vivo samples of gastric mucosa from cancer patients, and in MKN45 gastric cancer cell line after exposure to proinflammatory cytokines interleukin (IL)-1β or tumor necrosis factor (TNF)-α, that activate the NF-κB pathway. We found that IL-1β and TNF-α activate the NF-κB pathway, as reflected in the nuclear expression of p65 and the activation of p-IκBα, and downregulate TFF1 expression after 1 or 2 h of exposure. Moreover, cells in the superficial gastric epithelium in ex vivo samples co-expressed TFF1/p65 at cellular level, whereas tumor cells did not. In summary, downregulation of TFF1 expression during gastric neoplastic transformation is associated with activation of the NF-κB pathway through IL-1β or TNF-α, but other regulatory mechanisms might also be involved.

Inhibition of Hedgehog signaling in the gastrointestinal tract: targeting the cancer microenvironment

This review summarizes emerging information regarding the Hedgehog (Hh) signaling pathway during neoplastic transformation in the gastrointestinal tract. Although there is a role for the well-established canonical pathway in which Hedgehog ligands interact with their receptor Patched, there is sufficient evidence that downstream components of the Hh pathway, e.g., Gli1, are hijacked by non-Hh signaling pathways to promote the conversion of the epithelium to dysplasia and carcinoma. We review the canonical pathway and involvement of primary cilia, and then focus on current evidence for Hh signaling in luminal bowel cancers as well as accessory organs, i.e., liver, pancreas and biliary ducts. We conclude that targeting the Hh pathway with small molecules, nutriceuticals and other mechanisms will likely require a combination of inhibitors that target Gli transcription factors in addition to canonical modulators such as Smoothened.

The Yin and Yang of Toll-like receptors in cancer

Recognition of non-self molecular patterns by pattern recognition receptors is a cornerstone of innate immunity. Toll-like receptors (TLRs) exert a key role in recognizing pathogen-associated molecular patterns (PAMPs) but have also been implicated in the recognition of damage-associated molecular patterns (DAMPs). As such, TLRs regulate a wide range of biological responses including inflammatory and immune responses during carcinogenesis. The high expression of TLRs by antigen-presenting cells, including dendritic cells, and their ability to induce antitumor mediators such as type I interferon has led to efforts to utilize TLR agonists in tumor therapy in order to convert the often tolerant immune response toward antitumor responses. However, TLRs are also increasingly recognized as regulators of tumor-promoting inflammation and promoters of tumor survival signals. Here, we will review in detail the dichotomous role of TLRs in tumor biology, focusing on relevant TLR-dependent pro- and antitumor pathways, and discuss clinical applications of TLR-targeted therapies for tumor prevention and treatment.

Interleukin-1β induced by Helicobacter pylori infection enhances mouse gastric carcinogenesis

Interleukin-1β (Il1b) is considered to be involved in Helicobacter pylori (HP)-induced human gastric carcinogenesis, while the role of its polymorphisms in gastric cancer susceptibility remains controversial. Here, we aimed to clarify the role of HP infection-induced IL1B in gastric inflammation and carcinogenesis using Il1b(-/-) (Il1b-null) mice. In gastric mucosa of the Il1b(+/+) (WT) mice, HP infection induced Il1b expression and severe inflammation. In contrast, in Il1b-null mice, recruitment of neutrophils and macrophages by HP infection was markedly suppressed. In a carcinogenicity test, the multiplicity of gastric tumors was significantly suppressed in theIl1b-null mice (58% of WT; P<0.005). Mechanistically, HP infection induced NF-κB activation both in the inflammatory and epithelial cells in gastric mucosae, and the activation was attenuated in the Il1b-null mice. Accordingly, increased proliferation and decreased apoptosis of gastric epithelial cells induced by HP infection in the WT mice were attenuated in the Il1b-null mice. These results demonstrated that the IL1B physiologically induced by HP infection enhanced gastric carcinogenesis by affecting both inflammatory and epithelial cells.