Supplementary Materials1002721_Supplemental_Information. in human colorectal cancer (CRC) cells These findings provide

Supplementary Materials1002721_Supplemental_Information. in human colorectal cancer (CRC) cells These findings provide evidence that IL-15 suppresses colitis-associated colon carcinogenesis through regulation of antitumor cytotoxicity, and modulation of the inflammatory tumor micromilieu. to IL-2R/c on neighboring cells.8,9 IL-15- and IL-15R-deficient mice exhibit a common phenotype that has demonstrated an essential role of IL-15 in both the development and homeostasis of memory CD8+ T cells, natural killer cells (NK), invariant NKT (iNKT) cells and intestinal intraepithelial lymphocytes (IEL).10,11 Conversely, IL-15 has been shown to be pro-tumorogenic, through promotion of tumor growth, invasion and metastasis, while also protecting tumor cells from apoptosis.12-16 Furthermore, in humans, overexpression of IL-15 promotes development of large granular lymphocytic leukemia.12,17 Thus, the clinical value of targeting IL-15 in cancer immunotherapy remains uncertain and may be highly context-dependent. Of interest to this study, it is ill understood whether IL-15 is required for the development or suppression of inflammation-induced cancer. Cytokines produced by tumor-infiltrating immune cells modify tumor growth and survival, promote angiogenesis and inhibit antitumor immune responses to promote the development of pre-malignant cells. The balance between pro- and anti-inflammatory activities is critical for an efficient antitumor immune response,18 with dysregulation of IL-6, Zarnestra manufacturer IL-17, IL-23, and IL-22 cytokine signaling pathways playing an important inflammatory role in the development and progression of intestinal tumors.19 Furthermore, genetic variations within pro- and anti-inflammatory interleukins may confer risk of developing or impact survival rates in colon cancer.20,21 Among these, single nucleotide polymorphisms (SNPs) from IL-3, IL-6R, IL-8 and, interestingly, IL-15 were found to be Zarnestra manufacturer associated with an increased colon cancer risk,22 while IL-1 or IL-1 receptor antagonist polymorphisms negatively impact on CRC survival and recurrence.23,24 The role of the inflammatory milieu is of particular importance in CRC as the risk of developing dysplasia and CRC positively correlates with the duration and degree of inflammation in patients with irritable bowel disease (IBD).25 While there is abundant evidence indicating the causal relationship of chronic mucosal inflammation with CRC,26 the mechanism(s) underlying this correlation, namely the role of IL-15-mediated signaling, remain largely unknown. In light of the complex and dichotomous role of IL-15 in an oncology setting, summarized above, this current study seeks to clarify the contribution of IL-15 in a well-defined experimental model of inflammation-induced CRC. For this, a single injection of the carcinogen azoxymethane (AOM) was combined with the dextran sulfate sodium (DSS) mouse model of chronic colon inflammation.27,28 This generates a relatively non-invasive and reproducible model of colitis-associated carcinoma (CAC). Utilizing this model, we have investigated the role that IL-15 plays on tumor development and growth using IL-15- or IL-15R- deficient mice as well as a newly generated strain of mice, in which IL-15 is selectively expressed in predominantly antigen presenting cells under the control of the CD11c-promoter. In this model, we demonstrate that IL-15 deficiency increases tumor burden as a result of deficient NK and CD8+ T cell immunity and a tumor-supporting inflammatory milieu, indicating that intestinal homeostasis and suppression of inflammation induced-tumorigenesis are dependent on IL-15. Results IL-15 deficiency promotes inflammation-induced colorectal tumorigenesis in mice To determine the role of IL-15 in inflammation-induced colorectal tumorigenesis we utilized the AOM/DSS model. Briefly, mice were injected with AOM followed by three cycles of 1% DSS in drinking water.27,28 Firstly, we compared the survival and colon carcinoma burden between and to WT mice after induction of colitis-associated colon carcinogenesis. IL-15- Mouse monoclonal to OCT4 but not IL-15R-deficient mice, had significantly reduced survival rates compared to WT mice (Fig. 1A), with 25% of mice dying after completion of the second DSS administration cycle. Tumor incidence was 100% in mice, and colon weight and tumor size was significantly higher in compared to and WT mice (Fig. 1BCF). Adenomas greater than 4mm in diameter were exclusively found in mice with disrupted IL-15 signaling (34% and 22%) (Fig. 1D). Open in a separate window Figure 1. Increased Zarnestra manufacturer tumorigenesis in mice in a colitis-associated cancer model. Survival rates (A) of WT, and Zarnestra manufacturer mice subjected to AOM/DSS treatment, were monitored. Colon weight (B), numbers of tumors per mouse (C), size (D) and location (E) of tumors were determined. Data represented as mean SEM of two independent experiments (WT = 14, = 11, = 13). (F) Representative images of longitudinally cut colons from WT (= 2), (= 2) and (= 2). (G) Representative H&E images of formalin-fixed tissues from proximal, mid and distal colonic regions. Dotted lines indicate adenomas with high-grade dysplasia. Insert enlarges a cancerous gland invading muscularis mucosa, with the overlying epithelium which is dysplastic. Scale.