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Baseline platelet production is dependent on thrombopoietin (TPO). TPO is constitutively produced and primarily regulated by receptor-mediated uptake by platelets. Inflammatory thrombocytosis is thought to be related to increased interleukin-6 (IL-6) levels. To address whether IL-6 might act through TPO to increase platelet counts, TPO was neutralized in vivo in C57BL/10 mice treated with IL-6, and hepatic TPO mRNA expression and TPO plasma levels were studied. Transcriptional regulation of TPO mRNA was studied in the hepatoblastoma cell line HepG2. Furthermore, TPO plasma levels were determined in IL-6-treated cancer patients. It is shown that IL-6-induced thrombocytosis in C57BL/10 mice is accompanied by enhanced hepatic TPO mRNA expression and elevated TPO plasma levels. Administration of IL-6 to cancer patients results in a corresponding increase in TPO plasma levels. IL-6 enhances TPO mRNA transcription in HepG2 cells. IL-6-induced thrombocytosis can be abrogated by neutralization of TPO, suggesting that IL-6 induces thrombocytosis through TPO. A novel pathway of TPO regulation by the inflammatory mediator IL-6 is proposed, indicating that the number of platelets by themselves might not be the sole determinant of circulating TPO levels and thus of thrombopoiesis. This regulatory pathway might be of relevance for the understanding of reactive thrombocytosis. IntroductionThrombocytosis can be classified into primary and secondary forms. Whereas primary thrombocytosis is observed in myeloproliferative syndromes, secondary or reactive thrombocytosis is noted in numerous clinical situations, 1 especially in association with inflammatory states of either infectious or noninfectious origin such as trauma and malignancy. 2,3 The extent to which mediators of the immune or hematopoietic system are involved in the regulation of the circulating platelet count in these conditions is insufficiently understood.Interleukin-6 (IL-6) plays a prominent role in inflammatory and neoplastic diseases. 4-6 Accordingly, mice deficient in IL-6 show a severely impaired acute-phase response. 7 Administration of IL-6 to humans has been associated with an increase in circulating platelet counts. [8][9][10][11][12][13][14] Furthermore, serum levels of IL-6 were significantly higher in patients with reactive thrombocytosis than in control patients. 15,16 Whether the thrombopoietic effect of IL-6 in vivo is caused by direct stimulation of hematopoietic progenitor cells or is indirectly mediated is unknown.Thrombopoietin (TPO), the ligand of the c-mpl proto-oncogene, is the primary regulator of proliferation and differentiation of megakaryocyte progenitors. [17][18][19][20][21][22][23] Mice rendered deficient in TPO or TPO receptor by gene targeting show severe thrombocytopenia, with platelet counts reduced by approximately 90%. 22,24 Treatment of mice, nonhuman primates, and humans with recombinant TPO or recombinant megakaryocyte growth and development factor, which constitutes a truncated, biologically active form of TPO, results in sig...

In individuals with mammary carcinoma, the most relevant prognostic predictor of distant organ metastasis and clinical outcome is the status of axillary lymph node metastasis. Metastases form initially in axillary sentinel lymph nodes and progress via connecting lymphatic vessels into postsentinel lymph nodes. However, the mechanisms of consecutive lymph node colonization are unknown. Through the analysis of human mammary carcinomas and their matching axillary lymph nodes, we show here that intrametastatic lymphatic vessels and bulk tumor cell invasion into these vessels highly correlate with formation of postsentinel metastasis. In an in vitro model of tumor bulk invasion, human mammary carcinoma cells caused circular defects in lymphatic endothelial monolayers. These circular defects were highly reminiscent of defects of the lymphovascular walls at sites of tumor invasion in vivo and were primarily generated by the tumor-derived arachidonic acid metabolite 12S-HETE following 15-lipoxygenase-1 (ALOX15) catalysis. Accordingly, pharmacological inhibition and shRNA knockdown of ALOX15 each repressed formation of circular defects in vitro. Importantly, ALOX15 knockdown antagonized formation of lymph node metastasis in xenografted tumors. Furthermore, expression of lipoxygenase in human sentinel lymph node metastases correlated inversely with metastasis-free survival. These results provide evidence that lipoxygenase serves as a mediator of tumor cell invasion into lymphatic vessels and formation of lymph node metastasis in ductal mammary carcinomas.

Primary sclerosing cholangitis (PSC) is a chronic bile duct disease affecting 2.4–7.5% of individuals with inflammatory bowel disease. We performed a genome-wide association analysis of 2,466,182 SNPs in 715 individuals with PSC and 2,962 controls, followed by replication in 1,025 PSC cases and 2,174 controls. We detected non-HLA associations at rs3197999 in MST1 and rs6720394 near BCL2L11 (combined P = 1.1 × 10−16 and P = 4.1 × 10−8, respectively).

Immunization with cardiac myosin induces T cell-mediated myocarditis in genetically predisposed mice and serves as a model for autoimmune heart disease. This study was undertaken to identify pathogenic epitopes on the myosin molecule. Our approach was based on the comparison of the pathogenicity between cardiac ( ␣ -) myosin and soleus muscle ( ␤ -) myosin. We show that ␣ -myosin is the immunodominant isoform and induces myocarditis at high severity and prevalence whereas ␤ -myosin induces little disease. Therefore the immunodominant epitopes of ␣ -myosin must reside in regions of different amino acid sequence between ␣ -and ␤ -myosin isoforms. Cardiac myosin peptides corresponding to these regions of difference were synthesized and tested for their ability to induce inflammatory heart disease. Three pathogenic peptides were identified. One peptide that is located in the head portion of the molecule induced severe myocarditis, whereas two others that reside in the rod portion possessed only minor pathogenicity. The identification of pathogenic epitopes on the cardiac myosin molecule will allow detailed studies on the recognition of this antigen by the immune system and might be used to downmodulate ongoing heart disease. (

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Inflammatory bowel disease (IBD) constituting Crohn's disease (CD) and ulcerative colitis (UC) is related to a dysregulated T cell response. CCL20 attracts memory T lymphocytes and dendritic cells. We asked whether CCL20 expression is altered in IBD. Colonic biopsies were obtained from 114 subjects with IBD, non-IBD colitis, irritable bowel syndrome, and healthy controls. CCL20 and CCR6 mRNA expression was measured by Taqman-PCR, and protein secretion from colonic explant cultures (CEC) and its regulation by TNF-alpha by ELISA. CCL20, CCR6, and Langerin were identified by immunohistochemistry and immunofluorescence. CCL20 mRNA and protein were severalfold increased in involved CD and UC but not in non-IBD colitis. TNF-alpha increased and anti-TNF-alpha decreased CCL20 release in healthy control CEC but not in involved IBD colonic specimens. CCL20 localized to follicle-associated epithelium, and CCR6 to the adjacent mantle zone of lymphoid follicles. Furthermore, abundant numbers of Langerin(+) immature dendritic cells were identified in the subepithelial space of IBD specimens. CCL20 might regulate the attraction of T lymphocytes and dendritic cells in IBD.

Tumor budding in colorectal cancer (CRC) is recognized as a valuable prognostic factor but its translation into daily histopathology practice has been delayed by lack of agreement on the optimal method of assessment. Within the context of the Swiss Association of Gastrointestinal Pathology (SAGIP), we performed a multicenter interobserver study on tumor budding, comparing hematoxylin and eosin (H&E) with pan-cytokeratin staining using a 10 high power field (10HPF) and hotspot (1HPF) method. Two serial sections of 50 TNM stage II-IV surgically treated CRC were stained for H&E and pan-cytokeratin. Tumor buds were scored by independent observers at six participating centers in Switzerland and Austria using the 10HPF and 1HPF method on a digital pathology platform. Pearson correlation (r) and intra-class correlation coefficients (ICC) comparing scores between centers were calculated. Three to four times more tumor buds were detected in pan-cytokeratin compared to H&E slides. Correlation coefficients for tumor budding counts between centers ranged from r = 0.46 to r = 0.91 for H&E and from r = 0.73 to r = 0.95 for pan-cytokeratin slides. Interobserver agreement across all centers was excellent for pan-cytokeratin [10HPF: ICC = 0.83 and 1HPF: ICC = 0.8]. In contrast, assessment of tumor budding on H&E slides reached only moderate agreement [10HPF: ICC = 0.58 and 1HPF: ICC = 0.49]. Based on previous literature and our findings, we recommend (1) pan-cytokeratin staining whenever possible, (2) 10HPF method for resection specimens, and (3) 1HPF method for limited material (preoperative biopsy or pT1). Since tumor budding counts can be used to determine probabilities of relevant outcomes and as such more optimally complement clinical decision making, we advocate the avoidance of cutoff scores.