Expression of both TNF-alpha receptor subtypes is essential for optimal skin tumour development

Tumor-Elicited Inflammation and Colorectal Cancer

The link between chronic inflammation and cancer has long been suspected, due to the pioneering work of Rudolf Virchow over 150 years ago. Yet the causal relationship between inflammation and cancer was only deciphered in the past decade or so, using animal models of various cancers. Up to 20% of all human cancers result from chronic inflammation and persistent infections. Proinflammatory cytokines and tumor-infiltrating myeloid and immune cells play critical roles in almost every developmental stages of inflammation-induced cancers, from initiation, promotion, and progression to malignant metastasis. However, even in cancers with no preceding inflammation, inflammatory cells infiltrate tumor stroma and contribute to cancer development. Such "tumor-elicited inflammation" further emphasizes the importance of inflammation in different types of cancers, including that of the colon. In this review, we summarize our current knowledge of the function and induction mechanisms of inflammatory cytokines during colorectal cancer development, and hope to provide insight into the development of novel anticancer therapies by modulating tumor-elicited inflammation.

Synergistic Inhibition of Tumor Necrosis Factor-Alpha-Stimulated Pro-Inflammatory Cytokine Expression in HaCaT Cells by a Combination of Rapamycin and Mycophenolic Acid

Background

Keratinocytes release various pro-inflammatory cytokines, chemokines, and adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1) in response to cytokines such as tumor necrosis factor (TNF)-α and interferon (IFN)-γ. Rapamycin and mycophenolic acid (MPA) have potent immunosuppressive activity because they inhibit lymphocyte proliferation.

Objective

We investigated the effects of rapamycin and MPA on the expression of inflammation-related factors such as ICAM-1 and inducible nitric oxide synthase (iNOS), pro-inflammatory cytokines and chemokines, and related signaling pathways in TNF-α-stimulated HaCaT cells.

Methods

The viability of HaCaT cells treated with rapamycin and MPA was confirmed using MTT assay. The expression of various cytokines such as interleukin (IL)-1β, IL-6, and IL-8; inflammation-related factors such as ICAM-1 and iNOS; and the activation of mitogen activated protein kinase (MAPK) signaling pathways mediated by extracellular signal-related kinases (ERK), p38, and c-Jun N-terminal kinases (JNK) in TNF-α-stimulated HaCaT cells were confirmed using reverse transcription-polymerase chain reaction and western blotting.

Results

Combined treatment of TNF-α-induced HaCaT cells with rapamycin and MPA decreased ICAM-1 and iNOS expression and ERK and p38 activation more than treatment with either drug alone. The most significant decrease was observed with a combination of rapamycin (80 nM) and MPA (20 nM). These results show that co-treatment with these agents has a synergistic anti-inflammatory effect by blocking the activation of the ERK/p38 MAPK signaling pathway and thus suppressing the TNF-α-induced expression of ICAM-1 and iNOS.

Conclusion

The combination of rapamycin and MPA could potentially be used as a therapeutic approach in inflammatory skin diseases.

Innate sensing of microbial products promotes wound-induced skin cancer

The association between tissue damage, chronic inflammation and cancer is well known. However, the underlying mechanisms are unclear. Here we characterize a mouse model in which constitutive epidermal extracellular-signal-regulated kinase-MAP-kinase signalling results in epidermal inflammation, and skin wounding induces tumours. We show that tumour incidence correlates with wound size and inflammatory infiltrate. Ablation of tumour necrosis factor receptor (TNFR)-1/-2, Myeloid Differentiation primary response gene 88 or Toll-like receptor (TLR)-5, the bacterial flagellin receptor, but not other innate immune sensors, in radiosensitive leukocytes protects against tumour formation. Antibiotic treatment inhibits, whereas injection of flagellin induces, tumours in a TLR-5-dependent manner. TLR-5 is also involved in chemical-induced skin carcinogenesis in wild-type mice. Leukocytic TLR-5 signalling mediates upregulation of the alarmin HMGB1 (High Mobility Group Box 1) in wound-induced papillomas. HMGB1 is elevated in tumours of patients with Recessive Dystrophic Epidermolysis Bullosa, a disease characterized by chronic skin damage. We conclude that in our experimental model the combination of bacteria, chronic inflammation and wounding cooperate to trigger skin cancer.

Inflammation and wounding can promote cancer development, but the underlying mechanisms are unclear. Here Hoste et al. show that leukocytes sensing flagellin, a component of bacteria, play a key role in inducing skin cancer in the context of wounding and chronic inflammation.

Expression of tumor necrosis factor-alpha-mediated genes predicts recurrence-free survival in lung cancer

In this study, we conducted a meta-analysis on high-throughput gene expression data to identify TNF-α-mediated genes implicated in lung cancer. We first investigated the gene expression profiles of two independent TNF-α/TNFR KO murine models. The EGF receptor signaling pathway was the top pathway associated with genes mediated by TNF-α. After matching the TNF-α-mediated mouse genes to their human orthologs, we compared the expression patterns of the TNF-α-mediated genes in normal and tumor lung tissues obtained from humans. Based on the TNF-α-mediated genes that were dysregulated in lung tumors, we developed a prognostic gene signature that effectively predicted recurrence-free survival in lung cancer in two validation cohorts. Resampling tests suggested that the prognostic power of the gene signature was not by chance, and multivariate analysis suggested that this gene signature was independent of the traditional clinical factors and enhanced the identification of lung cancer patients at greater risk for recurrence.

Obesity and cancer: at the crossroads of cellular metabolism and proliferation

Obesity is associated with an increased risk of cancer. The mechanisms underlying this association include but are not limited to increased systemic inflammation, an anabolic hormonal milieu, and adipocyte-cancer crosstalk, aberrant stimuli that conspire to promote neoplastic transformation. Cellular proliferation is uncoupled from nutrient availability in malignant cells, promoting tumor progression. Elucidation of the mechanisms underlying the obesity-cancer connection will lead to the development of novel metabolism-based agents for cancer prevention and treatment.

Upregulation of Toll-like receptor 2 expression in colorectal cancer infected by human cytomegalovirus

The aim of the present study was to investigate the association between Toll-like receptor 2 (TLR2) expression and human cytomegalovirus (HCMV) in colorectal carcinoma by detecting the expression of IE1-72, TLR2, TLR4 and tumor necrosis factor (TNF)-α in colorectal carcinoma and colon adenoma samples, as well as by analyzing the mRNA levels of the proteins in colon cancer cell lines, following HCMV infection. For this study, 56 colorectal cancer and 36 colon adenoma samples were collected, and normal mucosal tissue adjacent to the tumor was used as the control. The expression of the IE1-72, TLR2, TLR4, nuclear factor (NF)-κB and TNF-α protein was detected by immunohistochemistry. Cells from the SW480 human colon carcinoma cell line were infected with HCMV. The expression of IE1-72, TLR2, TLR4, NF-κB and TNF-α mRNA was quantified at different time points prior to and following infection. The positive expression rate of IE1-72 was 44.6% (25/56) in colorectal cancer and 41.7% (15/36) in colon adenoma. These rates were significantly higher when compared with the 12.5% (7/56) observed in the normal tissues adjacent to the cancer tissues (P<0.05). The expression levels of TLR2, TLR4, NF-κB and TNF-α in colorectal cancer and adenoma were also higher than those in the control tissues. Furthermore, the expression of IE1-72 in colorectal cancer tissues was found to correlate with TLR2 and TLR4, and the correlation coefficients were 0.515 and 0.462, respectively. Following the infection of SW480 cells, the mRNA levels of TLR2 and TNF-α increased gradually from 6 h, peaked at 48 h, and then decreased gradually. No significant differences in TLR4 and NF-κB expression were identified. The results of the present study indicated that there is a specific association between HCMV and the occurrence and development of colorectal cancer, which may be facilitated by the TLR2 signaling pathway.

Myeloid suppressor cells require membrane TNFR2 expression for suppressive activity

TNF and TNF receptor type 2 (TNFR2) have been shown to be important for generation of myeloid-derived suppressor cells (MDSC). In order to analyze whether and how TNFR2 passes the effect of TNF on, myeloid cells from TNFR2-deficient mice were compared to respective cells from wild-type mice. Primary TNFR2-deficient myeloid cells showed reduced production of NO and IL-6 which was attributable to CD11b⁺ CD11c⁻ Ly6C⁺ Ly6G⁻ immature monocytic MDSC. TNFR2-deficient MDSC isolated from bone marrow were less suppressive for T cell proliferation compared to WT-derived MDSC. These differences on myeloid cells between the two mouse lines were still observed after co-culture of bone marrow cells from the two mouse lines together during myeloid cell differentiation, which demonstrated that the impaired functional capacity of TNFR2-deficient cells was independent of soluble factors but required membrane expression of TNFR2. Similarly, adoptive transfer of TNFR2-deficient bone marrow cells into wild-type hosts did not rescue the TNFR2-specific phenotype of bone marrow-derived myeloid cells. Therefore, membrane TNFR2 expression determines generation and function of monocytic MDSC.

Therapeutic non-toxic doses of TNF induce significant regression in TNFR2-p75 knockdown Lewis lung carcinoma tumor implants

Tumor necrosis factor-alpha (TNF) binds to two receptors: TNFR1/p55-cytotoxic and TNFR2/p75-pro-survival. We have shown that tumor growth in p75 knockout (KO) mice was decreased more than 2-fold in Lewis lung carcinoma (LLCs). We hypothesized that selective blocking of TNFR2/p75 LLCs may sensitize them to TNF-induced apoptosis and affect the tumor growth. We implanted intact and p75 knockdown (KD)-LLCs (>90%, using shRNA) into wild type (WT) mice flanks. On day 8 post-inoculation, recombinant murine (rm) TNF-α (12.5 ng/gr of body weight) or saline was injected twice daily for 6 days. Tumor volumes (tV) were measured daily and tumor weights (tW) on day 15, when study was terminated due to large tumors in LLC+TNF group. Tubular bones, spleens and peripheral blood (PB) were examined to determine possible TNF toxicity. There was no significant difference in tV or tW between LLC minus (-) TNF and p75KD/LLC-TNF tumors. Compared to 3 control groups, p75KD/LLC+TNF showed >2-5-fold decreases in tV (p<0.001) and tW (p<0.0001). There was no difference in tV or tW end of study vs. before injections in p75KD/LLC+TNF group. In 3 other groups tV and tW were increased 2.7-4.5-fold (p<0.01, p<0.0002 and p<0.0001). Pathological examination revealed that 1/3 of p75KD/LLC+rmTNF tumors were 100% necrotic, the remaining revealed 40-60% necrosis. No toxicity was detected in bone marrow, spleen and peripheral blood. We concluded that blocking TNFR2/p75 in LLCs combined with intra-tumoral rmTNF injections inhibit LLC tumor growth. This could represent a novel and effective therapy against lung neoplasms and a new paradigm in cancer therapeutics.

Molecular mechanisms of mouse skin tumor promotion

Multiple molecular mechanisms are involved in the promotion of skin carcinogenesis. Induction of sustained proliferation and epidermal hyperplasia by direct activation of mitotic signaling pathways or indirectly in response to chronic wounding and/or inflammation, or due to a block in terminal differentiation or resistance to apoptosis is necessary to allow clonal expansion of initiated cells with DNA mutations to form skin tumors. The mitotic pathways include activation of epidermal growth factor receptor and Ras/Raf/mitogen-activated protein kinase signaling. Chronic inflammation results in inflammatory cell secretion of growth factors and cytokines such as tumor necrosis factor-α and interleukins, as well as production of reactive oxygen species, all of which can stimulate proliferation. Persistent activation of these pathways leads to tumor promotion.

Biopsychological stress factors in BRCA mutation carriers

OBJECTIVE

Cancer risk-related stressors are prominent among BRCA mutation carriers. Loss of one's mother to a BRCA-associated cancer is an additional stressor, which may be related to an enhanced inflammatory response. This study examined the effect of mother's vital status on psychological factors and stress-associated biomarkers among BRCA mutation carriers. The role of bereavement on biopsychological variables was also examined.

METHODS

BRCA-carriers with known maternal transmission enrolled in the Gilda Radner Hereditary Cancer Program were invited to participate. Focus group composition was predetermined based on participants' personal cancer history and mother's vital status. Prior to the focus group, participants completed a Quality of Life (QOL) survey and collected a first morning saliva sample. Inflammatory biomarkers were analyzed from proximal archived serum. One day post focus group, a process survey, and morning saliva were collected.

RESULTS

QOL was significantly lower for those whose mothers are deceased (n = 17) compared to those whose mothers are alive (n = 15) (P = 0.003) after adjusting for age, personal cancer history and prophylactic surgery. Similarly, those whose mothers are deceased reported significantly more perceived stress (P = 0.015), more intrusive thoughts related to cancer risk (P = 0.049), and more anxiety (P = 0.003). Higher bereavement scores were significantly associated with QOL and psychological measures. Biomarker correlates were consistent with and significantly correlated to the patient-reported psychological outcomes for those whose mothers were deceased.

CONCLUSIONS

BRCA mutation carriers with a known maternal transmission whose mother is deceased report higher perceived stress and anxiety, lower QOL, and a stress-associated biomarker profile that is potentially globally immune suppressive.

Membrane TNF-alpha-activated programmed necrosis is mediated by Ceramide-induced reactive oxygen species

Background

Programmed necrosis is a form of caspase-independent cell death whose molecular regulation is poorly understood. While tumor necrosis factor-alpha (TNF-α) has been identified as an activator of programmed necrosis, the specific context under which this can happen is unclear. Recently we reported that TNF-α can be expressed by human tumor cells as both a membrane tethered (mTNF-α) and a soluble (sTNF-α) form. Whereas low level, tumor-derived sTNF-α acts as a tumor promoter, tumor cell expression of mTNF-α significantly delays tumor growth in mice, in large part by induction of programmed necrosis of tumor associated myeloid cells. In this study we sought to determine the molecular mechanism involved in mTNF-α oxidative stress-induced cell death by evaluating the known pathways involved in TNF receptor-induced programmed necrosis.

Methods

The source of Reactive Oxygen Species (ROS) in mTNF-α treated cells was determined by coculturing RAW 264.7 monocytic and L929 fibroblasts cells with fixed B16F10 control or mTNF-α expressing-melanoma cells in the presence of inhibitors of NADPH and mitochondria ROS. To identify the down-stream effector of TNF-a receptors (TNFR), level of phospho-RIP-1 and ceramide activity were evaluated.

To determine whether mTNF-mediated cell death was dependent on a specific TNFR, cell death was measured in primary CD11b myeloid cells isolated from wild-type or TNFR-1, TNFR-2, TNFR-1 and TNFR-2 double knockout mice, cocultured with various TNF-α isoform.

Results

Tumor derived-mTNF-α increased ROS-mediated cytotoxicity, independent of caspase-3 activity. Although TNFR on target cells were required for this effect, we observed that mTNF-induced cell death could be mediated through both TNFR-1 and the death domain-lacking TNFR-2. ROS generation and cytotoxicity were inhibited by a mitochondrial respiratory chain inhibitor but not by an inhibitor of NADPH oxidase. mTNF-α mediated cytotoxicity was independent of RIP-1, a serine/threonine kinase that serves as a main adaptor protein of sTNF-α induced programmed necrosis. Instead, mTNF-α-induced ROS and cell death was prohibited by the ceramide-activated protein kinase (CAPK) inhibitor.

Conclusion

These findings demonstrate that the mTNF-α isoform is an effective inducer of programmed necrosis through a caspase independent, ceramide-related pathway. Interestingly, unlike sTNFα, mTNF-induced programmed necrosis is not dependent on the presence of TNFR1.

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.

TNF-α signaling in Fanconi anemia

Tumor necrosis factor-alpha (TNF-α) is a major pro-inflammatory cytokine involved in systemic inflammation and the acute phase reaction. Dysregulation of TNF production has been implicated in a variety of human diseases including Fanconi anemia (FA). FA is a genomic instability syndrome characterized by progressive bone marrow failure and cancer susceptibility. The patients with FA are often found overproducing TNF-α, which may directly affect hematopoietic stem cell (HSC) function by impairing HSC survival, homing and proliferation, or indirectly change the bone marrow microenvironment critical for HSC homeostasis and function, therefore contributing to disease progression in FA. In this brief review, we discuss the link between TNF-α signaling and FA pathway with emphasis on the implication of inflammation in the pathophysiology and abnormal hematopoiesis in FA.

Membrane trafficking of death receptors: implications on signalling

Death receptors were initially recognised as potent inducers of apoptotic cell death and soon ambitious attempts were made to exploit selective ignition of controlled cellular suicide as therapeutic strategy in malignant diseases. However, the complexity of death receptor signalling has increased substantially during recent years. Beyond activation of the apoptotic cascade, involvement in a variety of cellular processes including inflammation, proliferation and immune response was recognised. Mechanistically, these findings raised the question how multipurpose receptors can ensure selective activation of a particular pathway. A growing body of evidence points to an elegant spatiotemporal regulation of composition and assembly of the receptor-associated signalling complex. Upon ligand binding, receptor recruitment in specialized membrane compartments, formation of receptor-ligand clusters and internalisation processes constitute key regulatory elements. In this review, we will summarise the current concepts of death receptor trafficking and its implications on receptor-associated signalling events.

Membrane versus soluble isoforms of TNF-α exert opposing effects on tumor growth and survival of tumor-associated myeloid cells

TNF-α, produced by most malignant cells, orchestrates the interplay between malignant cells and myeloid cells, which have been linked to tumor growth and metastasis. Although TNF-α can exist as one of two isoforms, a 26-kDa membrane tethered form (mTNF-α) or a soluble 17-kDa cytokine (sTNF-α), the vast majority of published studies have only investigated the biologic effects of the soluble form. We show for the first time that membrane and soluble isoforms have diametrically opposing effects on both tumor growth and myeloid content. Mouse lung and melanoma tumor lines expressing mTNF-α generated small tumors devoid of monocytes versus respective control lines or lines expressing sTNF-α. The lack of myeloid cells was due to a direct effect of mTNF-α on myeloid survival via induction of cell necrosis by increasing reactive oxygen species. Human non-small cell lung carcinoma expressed varying levels of both soluble and membrane TNF-α, and gene expression patterns favoring mTNF-α were predictive of improved lung cancer survival. These data suggest that there are significant differences in the role of different TNF-α isoforms in tumor progression and the bioavailability of each isoform may distinctly regulate tumor progression. This insight is critical for effective intervention in cancer therapy with the available TNF-α inhibitors, which can block both TNF-α isoforms.

Cancer-related inflammation

Solid tumors consist of neoplastic cells, non-malignant stromal cells, and migratory hematopoietic cells. Complex interactions between the cell types in this microenvironment regulate tumor growth, progression, metastasis, and angiogenesis. The cells and mediators of inflammation form a major part of the epithelial tumor microenvironment. In some cancers, inflammatory conditions precede development of malignancy; in others, oncogenic change drives a tumor-promoting inflammatory milieu. Whatever its origin, this "smoldering" inflammation aids proliferation and survival of malignant cells, stimulates angiogenesis and metastasis, subverts adaptive immunity, and alters response to hormones and chemotherapy. Cytokines are major mediators of communication between cells in the inflammatory tumor microenvironment. It is known that neoplastic cells often over-express proinflammatory mediators including proteases, eicosanoids, cytokines, and chemokines. Several cytokines such as macrophage migratory inhibitory factor (MIF), TNF-α, IL-6, IL-17, IL-12, IL-23, IL-10, and TGF-β have been linked with both experimental and human cancers and can either promote or inhibit tumor development. MIF is a major cytokine in many cancers and there is evidence that the cytokine is produced by both malignant cells and infiltrating leukocytes. In this article we will discuss the role of cancer-associated inflammation and the particular role of MIF in malignant disease.

Cancer-related inflammation

Solid tumors consist of neoplastic cells, non-malignant stromal cells, and migratory hematopoietic cells. Complex interactions between the cell types in this microenvironment regulate tumor growth, progression, metastasis, and angiogenesis. The cells and mediators of inflammation form a major part of the epithelial tumor microenvironment. In some cancers, inflammatory conditions precede development of malignancy; in others, oncogenic change drives a tumor-promoting inflammatory milieu. Whatever its origin, this "smoldering" inflammation aids proliferation and survival of malignant cells, stimulates angiogenesis and metastasis, subverts adaptive immunity, and alters response to hormones and chemotherapy. Cytokines are major mediators of communication between cells in the inflammatory tumor microenvironment. It is known that neoplastic cells often over-express proinflammatory mediators including proteases, eicosanoids, cytokines, and chemokines. Several cytokines such as macrophage migratory inhibitory factor (MIF), TNF-α, IL-6, IL-17, IL-12, IL-23, IL-10, and TGF-β have been linked with both experimental and human cancers and can either promote or inhibit tumor development. MIF is a major cytokine in many cancers and there is evidence that the cytokine is produced by both malignant cells and infiltrating leukocytes. In this article we will discuss the role of cancer-associated inflammation and the particular role of MIF in malignant disease.

TNF signaling drives myeloid-derived suppressor cell accumulation

TNF, an inflammatory cytokine that is enriched in the tumor microenvironment, promotes tumor growth and subverts innate immune responses to cancer cells. We previously reported that tumors implanted in TNF receptor-deficient (Tnfr-/-) mice are spontaneously rejected; however, the molecular mechanisms underlying this rejection are unclear. Here we report that TNF signaling drives the peripheral accumulation of myeloid-derived suppressor cells (MDSCs). MDSCs expand extensively during inflammation and tumor progression in mice and humans and can enhance tumor growth by repressing T cell-mediated antitumor responses. Peripheral accumulation of MDSCs was drastically impaired in Tnfr-/- mice. Signaling of TNFR-2, but not TNFR-1, promoted MDSC survival through upregulation of cellular FLICE-inhibitory protein (c-FLIP) and inhibition of caspase-8 activity. Loss of TNFRs impaired the induction of MDSCs from bone marrow cells, but this could be reversed by treatment with caspase inhibitors. These results demonstrate that TNFR-2 signaling promotes MDSC survival and accumulation and helps tumor cells evade the immune system.

Increased tumor necrosis factor receptor 1 expression in human colorectal adenomas

AIM: To determine the expression statuses of tumor necrosis factor (TNF)-α, its receptors (TNF-R) and downstream effector molecules in human colorectal adenomas.

METHODS: We measured the serum concentrations of TNF-α and its receptors in 62 colorectal adenoma patients and 34 healthy controls. The protein expression of TNF-α, TNF-R1, TNF-R2 and downstream signals of the TNF receptors, such as c-Jun N-terminal kinase (JNK), nuclear factor-κ B and caspase-3, were also investigated in human colorectal adenomas and in normal colorectal mucosal tissues by immunohistochemistry. Immunofluorescence confocal microscopy was used to investigate the consistency of expression of TNF-R1 and phospho-JNK (p-JNK).

RESULTS: The serum levels of soluble TNF-R1 (sTNF-R1) in adenoma patients were significantly higher than in the control group (3.67 ± 0.86 ng/mL vs 1.57 ± 0.72 ng/mL, P < 0.001). Receiver operating characteristic analysis revealed the high diagnostic sensitivity of TNF-R1 measurements (AUC was 0.928) for the diagnosis of adenoma, and the best cut-off level of TNF-R1 was 2.08 ng/mL, with a sensitivity of 93.4% and a specificity of 82.4%. There were no significant differences in the serum levels of TNF-α or sTNF-R2 between the two groups. Immunohistochemistry showed high levels of TNF-R1 and p-JNK expression in the epithelial cells of adenomas. Furthermore, a high incidence of co-localization of TNF-R1 and p-JNK was identified in adenoma tissue.

CONCLUSION: TNF-R1 may be a promising biomarker of colorectal adenoma, and it may also play an important role in the very early stages of colorectal carcinogenesis.

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.

Effect of high-dose intravenous vitamin C on inflammation in cancer patients

BACKGROUND

An inflammatory component is present in the microenvironment of most neoplastic tissues. Inflammation and elevated C-reactive protein (CRP) are associated with poor prognosis and decreased survival in many types of cancer.Vitamin C has been suggested as having both a preventative and therapeutic role in a number of pathologies when administered at much higher-than-recommended dietary allowance levels.Since in vitro studies demonstrated inhibition of pro-inflammatory pathways by millimolar concentrations of vitamin C, we decided to analyze the effects of high dose IVC therapy in suppression of inflammation in cancer patients.

METHODS

45 patients with prostate cancer, breast cancer, bladder cancer, pancreatic cancer, lung cancer, thyroid cancer, skin cancer and B-cell lymphoma were treated at the Riordan Clinic by high doses of vitamin C (7.5 g -50 g) after standard treatments by conventional methods.CRP and tumor markers were measured in serum or heparin-plasma as a routine analysis. In addition, serum samples were collected before and after the IVCs for the cytokine kit tests.

RESULTS

According to our data positive response to treatment, which was demonstrated by measurements of C- reactive protein, was found in 75% of patients and progression of the inflammation in 25% of patients. IVC treatments on all aggressive stage cancer patients showed the poor response of treatment.There was correlation between tumor markers (PSA, CEA, CA27.29 and CA15-3) and changes in the levels of C-reactive protein.Our test of the effect of IVC on pro-inflammatory cytokines demonstrated that inflammation cytokines IL-1α, IL-2, IL-8, TNF-α, chemokine eotaxin and CRP were reduced significantly after treatments.

CONCLUSIONS

The high dose intravenous ascorbic acid therapy affects C-reactive protein levels and pro-inflammation cytokines in cancer patients. In our study, we found that modulation of inflammation by IVC correlated with decreases in tumor marker levels.In summary, our data support the hypothesis that high dose intravenous ascorbate treatments may reduce inflammation in cancer patients. Our results suggest that further investigations into the use of IVC to reduce inflammation in diseases where inflammation is relevant are warranted.

TNF-α induces epithelial-mesenchymal transition of renal cell carcinoma cells via a GSK3β-dependent mechanism

TNF-α is a cytokine with antitumorigenic property. In contrast, low dose, chronic TNF-α production by tumor cells or stromal cells may promote tumor growth and metastasis. Serum levels of TNF-α are significantly elevated in renal cell carcinoma (RCC) patients. Here, we showed that TNF-α induced epithelial-mesenchymal transition (EMT) and promoted tumorigenicity of RCC by repressing E-cadherin, upregulating vimentin, activating MMP9, and invasion activities. In addition, TNF-α treatment inhibited glycogen synthase kinase 3β (GSK-3β) activity through serine-9 phosphorylation mediated by the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway in RCC cells. Inhibition of PI3K/AKT by LY294002 reactivated GSK-3β and suppressed the TNF-α-induced EMT of RCC cells. Inactivation of GSK-3β by LiCl significantly increased MMP9 activity and EMT of RCC cells. Activation of GSK-3β by transduction of constitutively active GSK-3β into RCC cells suppressed TNF-α-mediated anchorage-independent growth in soft agar and tumorigenicity in nude mice. Overexpression of a kinase-deficient GSK-3β, in contrast, potentiated EMT, anchorage-independent growth and drastically enhanced tumorigenicity in vivo. Most importantly, a 15-fold inactivation of GSK-3β activity, 3-fold decrease of E-cadherin, and 2-fold increase of vimentin were observed in human RCC tumor tissues. These results indicated that inactivation of GSK-3β plays a pivotal role in the TNF-α-mediated tumorigenesis of RCC.

Claudin 1 mediates TNFα-induced gene expression and cell migration in human lung carcinoma cells

Epithelial-mesenchymal transition (EMT) is an important mechanism in carcinogenesis. To determine the mechanisms that are involved in the regulation of EMT, it is crucial to develop new biomarkers and therapeutic targets towards cancers. In this study, when TGFβ1 and TNFα were used to induce EMT in human lung carcinoma A549 cells, we found an increase in an epithelial cell tight junction marker, Claudin 1. We further identified that it was the TNFα and not the TGFβ1 that induced the fibroblast-like morphology changes. TNFα also caused the increase in Claudin-1 gene expression and protein levels in Triton X-100 soluble cytoplasm fraction. Down-regulation of Claudin-1, using small interfering RNA (siRNA), inhibited 75% of TNFα-induced gene expression changes. Claudin-1 siRNA effectively blocked TNFα-induced molecular functional networks related to inflammation and cell movement. Claudin-1 siRNA was able to significantly reduce TNF-enhanced cell migration and fibroblast-like morphology. Furthermore, over expression of Claudin 1 with a Claudin 1-pcDNA3.1/V5-His vector enhanced cell migration. In conclusion, these observations indicate that Claudin 1 acts as a critical signal mediator in TNFα-induced gene expression and cell migration in human lung cancer cells. Further analyses of these cellular processes may be helpful in developing novel therapeutic strategies.

Emerging avenues linking inflammation and cancer

The role of inflammation in carcinogenesis has been extensively investigated and well documented. Many biochemical processes that are altered during chronic inflammation have been implicated in tumorigenesis. These include shifting cellular redox balance toward oxidative stress; induction of genomic instability; increased DNA damage; stimulation of cell proliferation, metastasis, and angiogenesis; deregulation of cellular epigenetic control of gene expression; and inappropriate epithelial-to-mesenchymal transition. A wide array of proinflammatory cytokines, prostaglandins, nitric oxide, and matricellular proteins are closely involved in premalignant and malignant conversion of cells in a background of chronic inflammation. Inappropriate transcription of genes encoding inflammatory mediators, survival factors, and angiogenic and metastatic proteins is the key molecular event in linking inflammation and cancer. Aberrant cell signaling pathways comprising various kinases and their downstream transcription factors have been identified as the major contributors in abnormal gene expression associated with inflammation-driven carcinogenesis. The posttranscriptional regulation of gene expression by microRNAs also provides the molecular basis for linking inflammation to cancer. This review highlights the multifaceted role of inflammation in carcinogenesis in the context of altered cellular redox signaling.

Macrophage-tumor crosstalk: role of TAMR tyrosine kinase receptors and of their ligands

Ample clinical and preclinical evidence indicates that macrophages interact with tumor cells as well as with virtually all populations of host cells present in the tumor microenvironment. This crosstalk can strongly promote malignancy, but also has in principle the potential to inhibit tumor growth. Thus, it is of the utmost importance to improve our understanding of the mechanisms driving the pro- and antimalignant behavior of tumor-associated macrophages (TAMs) in order to develop better anticancer therapies. In this review, we discuss the biological consequences of reciprocal interactions between TAMs, cancer cells, endothelial cells, fibroblasts and other leukocyte subfractions within tumors. It was recently elucidated that tumors specifically educate macrophages to secrete growth arrest-specific gene 6 (Gas6), the common ligand of the Tyro3, Axl, Mer receptor (TAMR) family. In turn, Gas6 fosters tumor growth by promoting cancer cell proliferation. Therefore, the Gas6-TAMR axis might represent a novel target for disrupting tumor-macrophage crosstalk. We summarize here what is known about TAMR and their ligands in (human) cancer biology. In order to shed more light on the role of macrophages in human cancer, we additionally provide an overview of what is currently known about the prognostic impact of TAMs in human cancer.

Chronic inflammation in cancer development

Chronic inflammatory mediators exert pleiotropic effects in the development of cancer. On the one hand, inflammation favors carcinogenesis, malignant transformation, tumor growth, invasion, and metastatic spread; on the other hand inflammation can stimulate immune effector mechanisms that might limit tumor growth. The link between cancer and inflammation depends on intrinsic and extrinsic pathways. Both pathways result in the activation of transcription factors such as NF-κB, STAT-3, and HIF-1 and in accumulation of tumorigenic factors in tumor and microenvironment. STAT-3 and NF-κB interact at multiple levels and thereby boost tumor-associated inflammation which can suppress anti-tumor immune responses. These factors also promote tumor growth, progression, and metastatic spread. IL-1, IL-6, TNF, and PGHS-2 are key mediators of an inflammatory milieu by modulating the expression of tumor-promoting factors. In this review we concentrate on the crucial role of pro-inflammatory mediators in inflammation-driven carcinogenesis and outline molecular mechanisms of IL-1 signaling in tumors. In addition, we elucidate the dual roles of stress proteins as danger signals in the development of anti-cancer immunity and anti-apoptotic functions.

Tumor cells and tumor-associated macrophages: secreted proteins as potential targets for therapy

Inflammatory pathways, meant to defend the organism against infection and injury, as a byproduct, can promote an environment which favors tumor growth and metastasis. Tumor-associated macrophages (TAMs), which constitute a significant part of the tumor-infiltrating immune cells, have been linked to the growth, angiogenesis, and metastasis of a variety of cancers, most likely through polarization of TAMs to the M2 (alternative) phenotype. The interaction between tumor cells and macrophages provides opportunities for therapy. This paper will discuss secreted proteins as targets for intervention.

FAT10 mediates the effect of TNF-α in inducing chromosomal instability

Tumor necrosis factor-alpha (TNF-α) plays important roles in chronic inflammation-associated tumorigenesis but the mechanisms involved remain poorly understood. Previously, we reported that high levels of FAT10 led to chromosomal instability that is mediated by an abbreviated mitotic phase. Here, we show that TNF-α induces FAT10 gene expression through TNF receptor 1 (TNFR1) and activates the NF-κB pathway in HCT116 and SW620 cells. TNF-α treatment also leads to an abbreviated mitotic phase that can be reversed by inhibiting FAT10 expression. This abbreviated mitotic phase is correlated with a TNF-α-induced reduction in the kinetochore localization of MAD2 during prometaphase which, again, can be reversed by inhibiting FAT10 gene expression. There is greater variability of chromosome numbers in HCT116 and SW620 cells treated with TNF-α than in untreated cells, which can be reversed by the introduction of short hairpin RNA (shRNA) against FAT10. The more stable chromosome numbers in HCT116 cells expressing FAT10 shRNA can revert to greater variability with the addition of a mutant FAT10 that is not recognized by the FAT10 shRNA. Upon TNF-α stimulation, higher cell death is observed when FAT10 expression is inhibited by shRNA. These data strongly suggest that FAT10 plays an important role in mediating the function of TNF-α during tumorigenesis by inducing cell cycle deregulation and chromosomal instability, and by inhibiting apoptosis.

CD44 and HCELL: preventing hematogenous metastasis at step 1

Despite great strides in our knowledge of the genetic and epigenetic changes underlying malignancy, we have limited information on the molecular basis of metastasis. Over 90% of cancer deaths are caused by spread of tumor cells from a primary site to distant organs and tissues, highlighting the pressing need to define the molecular effectors of cancer metastasis. Mounting evidence suggests that circulating tumor cells (CTCs) home to specific tissues by hijacking the normal leukocyte trafficking mechanisms. Cancer cells characteristically express CD44, and there is increasing evidence that hematopoietic cell E-/L-selectin ligand (HCELL), a sialofucosylated glycoform of CD44, serves as the major selectin ligand on cancer cells, allowing interaction of tumor cells with endothelium, leukocytes, and platelets. Here, we review the structural biology of CD44 and of HCELL, and present current data on the function of these molecules in mediating organ-specific homing/metastasis of CTCs.

Tumor Necrosis Factor (TNF) and Chemokines in Colitis-Associated Cancer

The connection between inflammation and tumorigenesis has been well established, based on a great deal of supporting evidence obtained from epidemiological, pharmacological, and genetic studies. One representative example is inflammatory bowel disease, because it is an important risk factor for the development of colon cancer. Moreover, intratumoral infiltration of inflammatory cells suggests the involvement of inflammatory responses also in other forms of sporadic as well as heritable colon cancer. Inflammatory responses and tumorigenesis activate similar sets of transcription factors such as NF-κB, Stat3, and hypoxia inducible factor and eventually enhances the expression of inflammatory cytokines including tumor necrosis factor (TNF) and chemokines. The expression of TNF and chemokines is aberrantly expressed in a mouse model of colitis-associated carcinogenesis as well as in inflammatory bowel disease and colon cancer in humans. Here, after summarizing the presumed actions of TNF and chemokines in tumor biology, we will discuss the potential roles of TNF and chemokines in chronic inflammation-associated colon cancer in mice.

Luteolin, a novel natural inhibitor of tumor progression locus 2 serine/threonine kinase, inhibits tumor necrosis factor-alpha-induced cyclooxygenase-2 expression in JB6 mouse epidermis cells

Targeting tumor necrosis factor (TNF)-α-mediated signal pathways may be a promising strategy for developing chemopreventive agents, because TNF-α-mediated cyclooxygenase (COX)-2 expression plays a key role in inflammation and carcinogenesis. Luteolin [2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-chromenone] exerts anticarcinogenic effects, although little is known about the underlying molecular mechanisms and specific targets of this compound. In the present study, we found that luteolin inhibited TNF-α-induced COX-2 expression by down-regulating the transactivation of nuclear factor-κB and activator protein-1. Furthermore, luteolin inhibited TNF-α-induced phosphorylation of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase 1/ERK/p90(RSK), mitogen-activated protein kinase kinase 4/c-Jun N-terminal kinase/c-Jun, and Akt/p70(S6K). However, it had no effect on the phosphorylation of p38. These effects of luteolin on TNF-α-mediated signaling pathways and COX-2 expression are similar to those achieved by blocking tumor progression locus 2 serine/threonine kinase (TPL2) using pharmacologic inhibitors and small interfering RNAs. Luteolin inhibited TPL2 activity in vitro and in TPL2 immunoprecipitation kinase assays by binding directly in an ATP-competitive manner. Overall, these results indicate that luteolin exerts potent chemopreventive activities, which primarily target TPL2.

B regulatory cells and the tumor-promoting actions of TNF-α during squamous carcinogenesis

The inflammatory cytokine TNF-α has been recognized as a critical tumor promoter, but the effector cells that mediate its action have not been fully characterized. Because B cells regulate squamous and prostate carcinogenesis, and Tnf(-/-) mice harbor B-cell defects, we investigated the hypothesis that B cells are important effector cells for TNF-α-mediated promotion of cancer development. Using an adoptive transfer strategy and the 7,12-dimethylbenz[α]anthracene/terephthalic acid (DMBA/TPA) two-stage model of skin carcinogenesis, we found that both B cells and TNF-α are critical for the development of DMBA/TPA-induced papilloma. Transfer of B cells from DMBA/TPA-treated wild-type mice to Tnf(-/-) mice rescued papilloma development to a wild-type level, a result not observed when B cells from Tnf(-/-) mice were transferred to Rag2(-/-) mice or when TNF-α was eliminated selectively in B cells. Resistance to papilloma development in Tnf(-/-) mice was associated with increased IFN-γ and CD8(+) T cells in skin and a significant reduction in IL-10-producing B regulatory cells alongside an increase in IFN-γ-producing CD8(+) T cells in the spleen. These data indicate that during DMBA/TPA-induced squamous carcinogenesis TNF-α mediates tumor-promoting activity via regulatory B cells that repress antitumor immunity.

Role of TLR2-dependent inflammation in metastatic progression

Inflammation is a part of the host defense system, which provides protection against invading pathogens. However, it has become increasingly clear that inflammation can be evoked by endogenous mediators through Toll-like receptors (TLRs) to enhance tumor progression and metastasis. Here, we discuss the roles of TLR-mediated inflammation in tumor progression and the mechanisms through which it accomplishes this pathogenic function.

Anti-tumor immunity and mechanism of immunosuppression mediated by tumor cells: role of tumor-derived soluble factors and cytokines

The immune system plays a crucial role in the protection against tumor growth and progression. However, the activation of the immune system against the neoplastic cells does not always occur and, therefore, tumor cells are able to grow and progress continually in the host. It has now been realized that tumor cells themselves produce many of the important factors that are responsible for dismounting of effective immune response. These tumor-derived soluble factors invariably subdue the functions of almost every immune cell population. Therefore, we attempted to underline the mechanism of anti-tumor immune response and immunosuppression induced by tumor cells.

Oncogene-driven intrinsic inflammation induces leukocyte production of tumor necrosis factor that critically contributes to mammary carcinogenesis

Oncogene activation promotes an intrinsic inflammatory pathway that is crucial for cancer development. Here, we have investigated the actual effect of the inflammatory cytokine tumor necrosis factor (TNF) on the natural history of spontaneous mammary cancer in the HER2/neuT (NeuT) transgenic mouse model. Bone marrow transplantation from TNF knockout mice into NeuT recipients significantly impaired tumor growth, indicating that the source of TNF fostering tumor development was of bone marrow origin. We show that the absence of leukocyte-derived TNF disarranged the tumor vasculature, which lacked pericyte coverage and structural integrity, leading to diffuse vascular hemorrhage and stromal necrosis. In addition, tumor-associated Tie2-expressing monocytes were reduced and cytokine expression skewed from Th2 to Th1 type. Treatment of NeuT mice with anti-TNF antibody partially phenocopied the antitumor effect of TNF-deficient bone marrow cell transplantation, providing a strong preclinical background and rationale for the introduction of TNF antagonists in the treatment of human breast cancer, including basal-like samples for which consolidated targeted therapies do not exist.

Inflammation, tumor necrosis factor and Wnt promotion in gastric cancer development

Infection-associated chronic inflammation plays an important role in tumorigenesis, and macrophages are a key player in both inflammation and tumorigenesis. Tumor-associated macrophages accelerate tumorigenesis through the enhancement of angiogenesis, remodeling and the suppression of antitumor immunity. Helicobacter pylori infection induces inflammatory responses, which are closely associated with gastric cancer development. Recent studies using mouse models indicate that activated macrophages in the infected and inflamed gastric mucosa express TNF-alpha, which stimulates the surrounding epithelial cells to promote Wnt signaling activity. Such a promotion of Wnt signaling activity beyond the threshold for tumorigenesis may, therefore contribute to gastric cancer development. Accordingly, it is possible that the TNF-alpha-induced promotion of Wnt signaling is a novel protumorigenic mechanism of inflammation in gastric carcinogenesis.

Cocoa polyphenols suppress TNF-α-induced vascular endothelial growth factor expression by inhibiting phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase kinase-1 (MEK1) activities in mouse epidermal cells

Cocoa polyphenols have antioxidant and anti-inflammatory effects. TNF-α is a pro-inflammatory cytokine that has a vital role in the pathogenesis of inflammatory diseases such as cancer and psoriasis. Vascular endothelial growth factor (VEGF) expression is associated with tumorigenesis, CVD, rheumatoid arthritis and psoriasis. We tested whether cocoa polyphenol extract (CPE) inhibited TNF-α-induced VEGF expression in promotion-sensitive JB6 mouse epidermal cells. CPE significantly inhibited TNF-α-induced up-regulation of VEGF via reducing TNF-α-induced activation of the nuclear transcription factors activator protein-1 (AP-1) and NF-κB, which are key regulators of VEGF expression. CPE also inhibited TNF-α-induced phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinase. CPE blocked activation of their downstream kinases, p70 kDa ribosomal protein S6 kinase and p90 kDa ribosomal protein S6 kinase. CPE suppressed phosphoinositide 3-kinase (PI3K) activity via binding PI3K directly. CPE did not affect TNF-α-induced phosphorylation of mitogen-activated protein kinase kinase-1 (MEK1) but suppressed TNF-α-induced MEK1 activity. Collectively, these results indicate that CPE reduced TNF-α-induced up-regulation of VEGF by directly inhibiting PI3K and MEK1 activities, which may contribute to its chemopreventive potential.

Inflammatory bowel disease and intestinal cancer: a paradigm of the Yin-Yang interplay between inflammation and cancer

Colon cancer represents a paradigm for the connection between inflammation and cancer in terms of epidemiology and mechanistic studies in preclinical models. Key components of cancer promoting inflammation include master transcription factors (for example, nuclear factor kappaB, STAT3), proinflammatory cytokines (for example, tumor necrosis factor, interleukin-6 (IL-6)), cyclooxygenase-2 and selected chemokines (for example, CCL2). Of no less importance are mediators that keep inflammation in check, including IL-10, transforming growth factorbeta, toll-like receptor and the IL-1 receptor inhibitor TIR8/SIGIRR, and the chemokine decoy and scavenger receptor D6. Dissection of molecular pathways involved in colitis-associated cancer may offer opportunities for innovative therapeutic strategies.

MK2 regulates the early stages of skin tumor promotion

The association between inflammation and tumorigenesis is well recognized. Mitogen-activated protein kinase-activated protein kinase-2 (MK2) is known to play a pivotal role in inflammatory processes. Here, we studied the effect of MK2-deficiency and tumor necrosis factor (TNF)-alpha-deficiency on skin tumor development in mice using the two-stage chemical carcinogenesis model. We found that MK2(-/-) mice developed significantly fewer skin tumors compared with both TNF-alpha(-/-) and wild-type mice when induced by initiation with 7,12-dimethylbenz[a]anthracene (DMBA) and by promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). The TPA-induced inflammatory response was reduced in both, TNF-alpha(-/-) mice and MK2(-/-) mice, but most pronounced in TNF-alpha(-/-) mice, indicating that a reduced inflammatory response was not the only explanation for the inhibited tumorigenesis seen in MK2(-/-) mice. Interestingly, increased numbers of apoptotic cells were detected in the epidermis of MK2(-/-) mice compared with TNF-alpha(-/-) and wild-type mice, suggesting an additional role of MK2 in the regulation of apoptosis. This was further supported by: (i) increased levels of the tumor suppressor protein p53 in MK2(-/-) mice after DMBA/TPA treatment compared with controls, (ii) reduced phosphorylation (activation) of the negative p53 regulator, murine double minute 2 in MK2(-)(/-) mouse keratinocytes in vitro and (iii) a significant decrease in the DMBA/TPA induced apoptosis in cultured MK2(-/-) keratinocytes transfected with p53 small interfering RNA. Taken together, these findings demonstrate a dual role of MK2 in the early stages of tumor promotion through regulation of both the inflammatory response and apoptosis of DNA-damaged cells. These results also identify MK2 as a putative target for future skin carcinoma therapy.