The recently discovered iron regulatory peptide hormone hepcidin holds promise as a novel biomarker in iron metabolism disorders. To date, various mass spectrometry and immunochemical methods have been developed for its quantification in plasma and urine. Differences in methodology and analytical performance hinder the comparability of data. As a first step towards method harmonization, several hepcidin assays were compared. Worldwide eight laboratories participated in a urinary and plasma round robin in which hepcidin was analyzed. For both urine and plasma: (i) the absolute hepcidin concentrations differed widely between methods, (ii) the between-sample variation and the analytical variation of the methods are similar. Importantly, the analytical variation as percentage of the total variance is low for all methods, indicating their suitability to distinguish hepcidin levels of different samples. Spearman correlations between methods were generally high. The round robin results inform the scientific and medical community on the status and agreement of the current hepcidin methods. Ongoing initiatives should facilitate standardization by exchanging calibrators and representative samples.

The importance of mesenchymal cells in inflammation and/or neoplastic transformation is well recognized, but their role in the initiation of these processes, particularly in the intestine, remains elusive. Using mouse models of colorectal cancer, we show that IKKβ in intestinal mesenchymal cells (IMCs) is critically involved in colitis-associated, but not spontaneous tumorigenesis. We further demonstrate that IMC-specific IKKβ is involved in the initiation of colitis-associated cancer (CAC), as in its absence mice develop reduced immune cell infiltration, epithelial cell proliferation, and dysplasia at the early stages of the disease. At the molecular level, these effects are associated with decreased early production of proinflammatory and protumorigenic mediators, including IL-6, and reduced STAT3 activation. Ex vivo IKKβ-deficient IMCs show defective responses to innate immune stimuli such as LPS, as shown by decreased NF-κB signaling and reduced expression of important NF-κB target genes. Collectively, our results reveal a hitherto unknown role of mesenchymal IKKβ in driving inflammation and enabling carcinogenesis in the intestine.

Significance: Tumor progression locus-2 (Tpl2) is a proinflammatory gene genetically associated with inflammatory bowel diseases. This study provides a mechanistic interpretation for this association showing a dominant Tpl2-mediated homeostatic mechanism protecting mice from epithelial injury-induced colitis. This function of Tpl2 is mediated specifically by subepithelial intestinal myofibroblasts, a cell type supporting crypt stem cells. Tpl2 in myofibroblasts is essential for the compensatory proliferative response of the epithelium by promoting arachidonic acid metabolism and cyclooxygenase-2 (Cox-2)/prostaglandin E ₂ activation. Notably, in Crohn’s Disease patients, Tpl2 is downregulated in myofibroblasts isolated from the inflamed ileum. These results challenge current concepts on a solely proinflammatory function of Tpl2 and highlight the dominant role of subepithelial myofibroblasts in sensing inflammation and tissue damage and promoting intestinal homeostasis through Tpl2-Cox-2-prostaglandin E ₂ .

The tumor microenvironment plays a significant role in colitis-associated cancer (CAC). Intestinal myofibroblasts (IMFs) are cells in the intestinal lamina propria secreting factors that are known to modulate carcinogenesis; however, the physiological role of IMFs and signaling pathways influencing CAC have remained unknown. Tumor progression locus 2 (Tpl2) is a MAPK that regulates inflammatory and oncogenic pathways. In this study we addressed the role of Tpl2 in CAC using complete and tissue-specific ablation of Tpl2 in mutant mice. Tpl2-deficient mice did not exhibit significant differences in inflammatory burdens following azoxymethane (AOM)/dextran sodium sulfate (DSS) administration compared with wild-type mice; however, the mutant mice developed significantly increased numbers and sizes of tumors, associated with enhanced epithelial proliferation and decreased apoptosis. Cell-specific ablation of Tpl2 in IMFs, but not in intestinal epithelial or myeloid cells, conferred a similar susceptibility to adenocarcinoma formation. Tpl2-deficient IMFs upregulated HGF production and became less sensitive to the negative regulation of HGF by TGF-β3. In vivo inhibition of HGF-mediated c-Met activation blocked early, enhanced colon dysplasia in Tpl2-deficient mice, indicating that Tpl2 normally suppresses the HGF/c-Met pathway. These findings establish a mesenchyme-specific role for Tpl2 in the regulation of HGF production and suppression of epithelial tumorigenesis.