Inflammation-driven Tumorigenesis Research Articles

Differential Expression of IL-17, 22 and 23 in the Progression of Colorectal Cancer in Patients with K-ras Mutation: Ras Signal Inhibition and Crosstalk with GM-CSF and IFN-γ

Recent studies have suggested that aberrant K-ras signaling is responsible for triggering immunological responses and inflammation-driven tumorigenesis. Interleukins IL-17, IL-22, and IL-23 have been reported in various types of malignancies, but the exact mechanistic role of these molecules remains to be elucidated. Given the role of K-ras and the involvement of interleukins in colorectal tumorigenesis, research efforts are reported for the first time, showing that differentially expressed interleukin IL-17, IL-22, and IL-23 levels are associated with K-ras in a stage-specific fashion along colorectal cancer progression. Specifically, a) the effect of K-ras signaling was investigated in the overall expression of interleukins in patients with colorectal cancer and healthy controls, and b) an association was established between mutant K-ras and cytokines GM-CSF and IFN-γ. The results indicate that specific interleukins are differentially expressed in K-ras positive patients and the use of K-ras inhibitor Manumycin A decreases both interleukin levels and apoptosis in Caco-2 cells by inhibiting cell viability. Finally, inflammation-driven GM-CSF and IFN-γ levels are modulated through interleukin expression in tumor patients, with interleukin expression in the intestinal lumen and cancerous tissue mediated by aberrant K-ras signaling. Collectively, the findings a) indicate that interleukin expression is influenced by ras signaling and specific interleukins play an oncogenic promoter role in colorectal cancer, highlighting the molecular link between inflammation and tumorigenesis, and b) accentuate the interwoven molecular correlations as leads to new therapeutic approaches in the future.

IKK epsilon kinase is crucial for viral G protein-coupled receptor tumorigenesis

G protein-coupled receptors (GPCRs) are seven-transmembrane proteins that transmit diverse extracellular signals across a membrane. Herpesvirus genomes encode multiple GPCRs implicated in viral pathogenesis. Kaposi sarcoma-associated herpesvirus GPCR (kGPCR) activates proliferative pathways and, when expressed in endothelium in mice, sufficiently induces angiogenic tumor resembling human Kaposi's sarcoma. IKKε, an IκB kinase (IKK)-related kinase, is implicated in inflammation-driven tumorigenesis. We report here that IKKε is critically required for kGPCR tumorigenesis and links kGPCR to NF-κB activation. Using kGPCR-induced tumor models, we found that IKKε expression was drastically up-regulated in Kaposi sarcoma-like lesions and that loss of IKKε abolished tumor formation. Moreover, kGPCR interacted with and activated IKKε. Activated IKKε promoted NF-κB subunit RelA (also known as p65) phosphorylation, which correlated with NF-κB activation and inflammatory cytokine expression. The robust expression of IKKε and phosphorylated RelA was observed in human Kaposi sarcoma. Finally, a kinase-defective mutant of IKKε effectively abrogated NF-κB activation and tumorigenesis induced by kGPCR. Collectively, our findings uncover a critical IKKε in promoting NF-κB activation and tumorigenesis induced by a viral GPCR.

Modeling Colitis-Associated Cancer with Azoxymethane (AOM) and Dextran Sulfate Sodium (DSS)

Individuals with inflammatory bowel disease (IBD), such as Crohn's disease (CD) or ulcerative colitis (UC) are at increased risk of developing colorectal cancer (CRC) over healthy individuals. This risk is proportional to the duration and extent of disease, with a cumulative incidence as high as 30% in individuals with longstanding UC with widespread colonic involvement. Colonic dysplasia in IBD and colitis associated cancer (CAC) are believed to develop as a result of repeated cycles of epithelial cell injury and repair while these cells are bathed in a chronic inflammatory cytokine milieu. While spontaneous and colitis-associated cancers share the quality of being adenocarcinomas, the sequence of underlying molecular events is believed to be different. This distinction argues the need for specific animal models of CAC. Several mouse models currently exist for the study of CAC. Dextran sulfate sodium (DSS), an agent with direct toxic effects on the colonic epithelium, can be administered in drinking water to mice in multiple cycles to create a chronic inflammatory state. With sufficient duration, some of these mice will develop tumors. Tumor development is hastened in this model if administered in a pro-carcinogenic setting. These include mice with genetic mutations in tumorigenesis pathways (APC, p53, Msh2), as well as mice pre-treated with genotoxic agents (azoxymethane [AOM], 1,2-dimethylhydrazine [DMH]). The combination of DSS with AOM as a model for colitis associated cancer has gained popularity for its reproducibility, potency, low price, and ease of use. Though they have a shared mechanism, AOM has been found to be more potent and stable in solution than DMH. While tumor development in other models generally requires several months, mice injected with AOM and subsequently treated with DSS develop adequate tumors in as little as 7-10 weeks. Finally, AOM and DSS can be administered to mice of any genetic background (knock out, transgenic, etc.) without cross-breeding to a specific tumorigenic strain. Here, we demonstrate a protocol for inflammation-driven colonic tumorigenesis in mice utilizing a single injection of AOM followed by three seven-day cycles of DSS over a 10 week period. This model induces tumors with histological and molecular changes closely resembling those occurring in human CAC and provides a highly valuable model for the study of oncogenesis and chemoprevention in this disease.

Inhibition of CXCR2 profoundly suppresses inflammation-driven and spontaneous tumorigenesis.

The chemokine receptor CXCR2 is a key mediator of neutrophil migration that also plays a role in tumor development. However, CXCR2 influences tumors through multiple mechanisms and might promote or inhibit tumor development depending on context. Here, we used several mouse models of spontaneous and inflammation-driven neoplasia to define indispensable roles for CXCR2 in benign and malignant tumors. CXCR2-activating chemokines were part of the secretome of cultured primary benign intestinal adenomas (ApcMin/+) and highly expressed by all tumors in all models. CXCR2 deficiency profoundly suppressed inflammation-driven tumorigenesis in skin and intestine as well as spontaneous adenocarcinoma formation in a model of invasive intestinal adenocarcinoma (AhCreER;Apcfl/+;Ptenfl/fl mice). Pepducin-mediated CXCR2 inhibition reduced tumorigenesis in ApcMin/+ mice. Ly6G+ neutrophils were the dominant source of CXCR2 in blood, and CXCR2 deficiency attenuated neutrophil recruitment. Moreover, systemic Ly6G+ cell depletion purged CXCR2-dependent tumor-associated leukocytes, suppressed established skin tumor growth and colitis-associated tumorigenesis, and reduced ApcMin/+ adenoma formation. CXCR2 is thus a potent protumorigenic chemokine receptor that directs recruitment of tumor-promoting leukocytes into tissues during tumor-inducing and tumor-driven inflammation. Similar leukocyte populations were also found in human intestinal adenomas, which suggests that CXCR2 antagonists may have therapeutic and prophylactic potential in the treatment of cancer.

STAT3 can serve as a hit in the process of malignant transformation of primary cells

The transcription factor signal transducer and activator of transcription 3 (STAT3) acts downstream of many pro-oncogenic signals, including cytokines, growth factors and oncogenes, and is accordingly constitutively active in a wide variety of tumors that often become addicted to it. Moreover, STAT3 is a key player in mediating inflammation-driven tumorigenesis, where its aberrant continuous activation is typically triggered by local or systemic production of the pro-inflammatory cytokine IL-6. We recently showed that mouse embryonic fibroblasts (MEFs) derived from STAT3C k/in mice, which express physiological levels of the constitutively active mutant STAT3C, display features of transformed cells such as increased proliferation, resistance to apoptosis and senescence, and aerobic glycolysis. Here, we show that pre-existing constitutively active STAT3 is sufficient to prime primary MEFs for malignant transformation upon spontaneous immortalization. Transformation is strictly STAT3-dependent and correlates with high resistance to apoptosis and enhanced expression of anti-apoptotic/pro-survival genes. Additionally, hypoxia inducible factor (HIF)-1α level is elevated by twofold and contributes to STAT3 oncogenic activity by supporting high rates of aerobic glycolysis. Thus, constitutively active STAT3, an accepted essential factor for tumor growth/progression, can also act as a first hit in multistep carcinogenesis; this ability to predispose cells to malignant transformation may be particularly relevant in the pro-oncogenic niche represented by chronically inflamed tissues.

Abstract B41: A mouse model for inflammation-driven lung tumorigenesis

Abstract The link between chronic inflammation and cancer development has lately gained extensive epidemiological and experimental support, particularly in organs like liver, stomach, colon, and lung. Although experimental models are available to study inflammation-driven tumorigenesis in the liver, stomach, and colon, no such models are available for lung cancer. Therefore, the objective of the present study is to develop a model for inflammation-driven lung tumorigenesis. A/J mice received four intraperitoneal injections (two doses/week) of the tobacco smoke carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) at a dose level of 50 mg/kg body weight. Beginning one week after the last dose of NNK, the mice were given weekly intranasal instillations of lipopolysaccharide (LPS, 10ug/mouse), a potent inflammation-inducing agent, until the end of the study at week 27. Upon termination of the study, tumors on the surface of the lung were counted, their size determined and histopathologically analyzed. Moreover, we analyzed alterations in the expression of inflammation- and tumorigenesis-related proteins and microRNAs (miRs) by Western immunoblotting and qRT-PCR, respectively. Chronic exposure NNK-treated mice to LPS increased the number and size of lung tumors (47.3 ± 11 tumors/mouse for the NNK plus LPS group versus 28 ± 8 tumors/mouse in the NNK only group). Furthermore, lung tumors in the NNK plus LPS treated mice were significantly larger than the lung tumors of the mice challenged with NNK alone. Multiplicities of lung tumors in LPS-treated mice were similar to those mice given the vehicle. Multiplicities of the histopathological lesions pulmonary hyperplastic foci, adenoma, adenoma with dysplasia and adenocarcinoma in the NNK only group were 3.0 ± 1.2, 7.1 ± 2.9, 1.3 ± 1.1, and 0.3 ± 0.5/mouse, respectively. The corresponding frequencies of the lesions in the NNK plus LPS group were 3.1 ± 1.8, 11.8 ± 5.2, 3.9 ± 1.8, and 0.6 ± 0.7/mouse. Western immunoblotting studies showed that LPS exposure of NNK-treated mice enhanced activation of NF-kappaB, STAT3, and Akt but caused down-regulation of the tumor suppressor protein PTEN. Further, analyses of levels of five carcinogenesis-related microRNAs (miR-21, miR-146a, miR-150, miR-155 and miR-21, and miR-181b-1) showed increases in the expressions of miR-155 and miR-21. Levels of miR-155 and miR-21 were increased by 2.3-fold and 1.9-fold, respectively, in mice treated with NNK plus LPS group as compared to mice treated with NNK. Moreover, levels of miR-155 and miR-21 were increased by 10.5-fold and 4.7-fold, respectively, in LPS treated mice compared to vehicle-treated mice. In summary, our results demonstrate that LPS-induced chronic lung inflammation enhances lung tumorigenesis. This model could be a vey useful tool to understand the role inflammation in lung tumorigenesis and for identification of anti-inflammatory and lung cancer chemopreventive agents. Citation Information: Cancer Prev Res 2011;4(10 Suppl):B41.

Inhibition of Histone Deacetylases in Inflammatory Bowel Diseases

This review, comprised of our own data and that of others, provides a summary overview of histone deacetylase (HDAC) inhibition on intestinal inflammation as well as inflammation-mediated carcinogenesis. Experimental colitis in mice represents an excellent in vivo model to define the specific cell populations and target tissues modulated by inhibitors of HDAC. Oral administration of either suberyolanilide hydroxamic acid (SAHA) or ITF2357 results in an amelioration in these models, as indicated by a significantly reduced colitis disease score and histological score. This effect was paralleled by suppression of proinflammatory cytokines at the site of inflammation as well as specific changes in the composition of cells within the lamina propria. In addition, tumor number and size was significantly reduced in two models of inflammation-driven tumorigenesis, namely interleukin (IL)-10-deficient mice and the azoxymethane-dextran sulfate sodium (DSS) model, respectively. The mechanisms affected by HDAC inhibition, contributing to this antiinflammatory and antiproliferative potency will be discussed in detail. Furthermore, with regard to the relevance in human inflammatory bowel disease, the doses of ITF2357 considered safe in humans and the corresponding serum concentrations are consistent with the efficacious dosing used in our in vivo as well as in vitro experiments. Thus, the data strongly suggest that HDAC inhibitors could serve as a therapeutic option in inflammatory bowel disease.

Abstract 5323: Distinct roles of IL-17A in inflammation-induced tumor development and tumor immunosurveillance

Abstract While chronic inflammation is considered to be a critical component of tumorigenesis, the immune system can also prevent tumor development and/or growth. IL-17A and IL-17A secreting T cells, termed Th17 mediate inflammation via activation of a wide range of downstream inflammatory mediators that contribute to chronic inflammatory diseases. It also has been suggested that Th17 can be a constituent in tumor immunosurveillance since tumor-specific Th17 has been shown to eradicate established tumor. In the present study, we addressed the effects of inflammation/immunity driven by IL-17A on a primary tumor development model using a chemical carcinogen 3′-methylcholanthrene (MCA). We found that IL-17A deficient (IL-17A−/−) mice were protected from the primary tumor development by MCA. Paradoxically, the growth of primary tumors developed in IL-17A−/− mice was faster than that of tumors in WT (C57BL/6) mice. Although tumor cell lines derived from WT and IL-17A−/− mice grew equally in immunocompromised (T, B cell deficient C. B-17 scid) mice, those from IL-17−/− mice were easily rejected in C57BL/6 mice as compared to those from WT mice. Consistent with this, tumor growth of B16 melanoma, a non-immunogenic transplantable tumor cell line, was enhanced in IL-17A−/− mice. The apparently contrasting effects of IL-17A on tumor growth and development may reflect difference in cells producing IL-17A, namely cells mediate innate or acquired immunity. We transferred CD4+ T cells from WT mice into IL-17A−/−. While the transfer with CD4+ T cells from WT mice did not affect the primary tumor development in IL-17A−/− mice, the growth of primary tumors in IL-17A−/− mice transferred with WT CD4+ T cells was significantly suppressed. These results indicate that IL-17A promotes tumorigenesis possibly by enhancing inflammation and IL-17A produced by CD4+ T cells contributes to the immune surveillance to the emerging tumors as well. Overall, these results not only demonstrate that a single cytokine, IL-17A, plays contrasting role in tumor development and growth, but also indicate that immune inflammation-driven tumorigenesis and tumor immunosurveillance coexist in the same host. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5323.