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The tumor microenvironment promotes epigenetic changes in tumor cells associated with tumor aggressiveness. Here we report that in primary tumor cells, increased interleukin-6 (IL-6) expression brought on by DNA demethylation of its promoter by ten-eleven translocation 2 (TET2) promotes lung metastasis in osteosarcoma (OS). Xenograft experiments show increased IL-6expression and decreased methylation of its promoter in OS cells after implantation relative to before implantation. In addition, changes in IL-6methylation and expression seen in OS cells at the primary site were maintained at the metastatic site. TET2 knockdown in OS cells suppressed upregulation of IL-6and demethylation of its promoter in xenograft tumors and decreased tumor metastasis. We also present evidence showing that tumor cell-derived IL-6 facilitates glycolytic metabolism in tumor cells by activating the MEK/ERK1/2/hypoxia-inducible transcription factor-1α (HIF-1α) pathway and increases lung colonization by OS cells by upregulating expression of intercellular adhesion molecule-1 (ICAM-1), enhancing tumor metastasis. Blocking IL-6 signaling with a humanized monoclonal antibody against the IL-6 receptor reduced lung metastasis and prolonged survival of xenografted mice. These findings suggest that TET2-dependent IL-6induction enables acquisition of aggressive phenotypes in OS cells via the tumor microenvironment and that blocking IL-6 signaling could be serve as a potential therapy to antagonize metastasis.

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Renal fibrosis is a common pathological consequence of chronic kidney disease (CKD) with tissue fibrosis closely associated with chronic inflammation in numerous pathologies. However, molecular mechanisms underlying that association, particularly in the kidney, remain unclear. Here, we determine whether there is a molecular link between chronic inflammation and tissue fibrosis in CKD progression. Histological analysis of human kidneys indicated abundant expression of angiopoietin-like protein 2 (ANGPTL2) in renal tubule epithelial cells during progression of renal fibrosis. Numerous ANGPTL2-positive renal tubule epithelial cells colocalized with cells positive for transforming growth factor (TGF)-β1, a critical mediator of tissue fibrosis. Analysis of M1 collecting duct cells in culture showed that TGF-β1 increases ANGPTL2 expression by attenuating its repression through microRNA-221. Conversely, ANGPTL2 increased TGF-β1 expression through α5β1 integrin-mediated activation of extracellular signal-regulated kinase. Furthermore, ANGPTL2 deficiency in a mouse unilateral ureteral obstruction model significantly reduced renal fibrosis by decreasing TGF-β1 signal amplification in kidney. Thus, ANGPTL2 and TGF-β1 positively regulate each other as renal fibrosis progresses. Our study provides insight into molecular mechanisms underlying chronic inflammation and tissue fibrosis and identifies potential therapeutic targets for CKD treatment.

PHD3 influences apoptotic cell survival decisions in macrophages by altered production of Angiopoietin‐like protein 2. On a molecular level, cells sense changes in oxygen availability through the PHDs, which regulate the protein stability of the α‐subunit of the transcription factor HIF. Especially, PHD3 has been additionally associated with apoptotic cell death. We hypothesized that PHD3 plays a role in cell‐fate decisions in macrophages. Therefore, myeloid‐specific PHD3−/−mice were created and analyzed. PHD3−/−BMDM showed no altered HIF‐1α or HIF‐2α stabilization or increased HIF target gene expression in normoxia or hypoxia. Macrophage M1 and M2 polarization was unchanged likewise. Compared with macrophages from WT littermates, PHD3−/−BMDM exhibited a significant reduction in TUNEL‐positive cells after serum withdrawal or treatment with stauro and SNAP. Under the same conditions, PHD3−/−BMDM also showed less Annexin V staining, which is representative for membrane disruption, and indicated a reduced early apoptosis. In an unbiased transcriptome screen, we found that Angptl2 expression was reduced in PHD3−/−BMDM under stress conditions. Addition of rAngptl2 rescued the antiapoptotic phenotype, demonstrating that it is involved in the PHD3‐mediated response toward apoptotic stimuli in macrophages.

Introduction Breast cancer is a leading cause of cancer-related death in women worldwide, and its metastasis is a major cause of disease mortality. Therefore, identification of the mechanisms underlying breast cancer metastasis is crucial for the development of therapeutic and diagnostic strategies. Our recent study of immunodeficient female mice transplanted with MDA-MB231 breast cancer cells demonstrated that tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) accelerates metastasis through both increasing tumor cell migration in an autocrine/paracrine manner, and enhancing tumor angiogenesis. To determine whether ANGPTL2 contributes to its clinical pathogenesis, we asked whether serum ANGPTL2 levels reflect the clinical features of breast cancer progression.Methods We monitored the levels of secreted ANGPTL2 in supernatants of cultured proliferating MDA-MB231 cells. We also determined whether the circulating ANGPTL2 levels were positively correlated with cancer progression in an in vivo breast cancer xenograft model using MDA-MB231 cells. Finally, we investigated whether serum ANGPTL2 levels were associated with clinical features in breast cancer patients.Results Both in vitro and in vivo experiments showed that the levels of ANGPTL2 secreted from breast cancer cells increased with cell proliferation and cancer progression. Serum ANGPTL2 levels in patients with metastatic breast cancer were significantly higher than those in healthy subjects or in patients with ductal carcinoma in situ or non-metastatic invasive ductal carcinoma. Serum ANGPTL2 levels in patients negative for estrogen receptors and progesterone receptors, particularly triple-negative cases, reflected histological grades.Conclusions These findings suggest that serum ANGPTL2 levels in breast cancer patients could represent a potential marker of breast cancer metastasis.

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by symmetrical polyarticular synovitis of the diarthrodial joints. Several proinflammatory cytokines derived from both infiltrating inflammatory cells and activated resident cells within the RA joint play a fundamental role in the processes that cause inflammation. However, anticytokine treatment is beneficial but not curative, the effects are only partial, and nonresponses are common. Therefore, an effort has been made to identify other key regulators of inflammation in articular structures to develop new therapies to suppress synovial inflammation and joint destruction in RA. Adipose tissue-derived angiopoietin-like protein 2 (Angptl2) activates an inflammatory cascade in endothelial cells and induces chemotaxis of monocytes/macrophages in obesity, resulting in initiation and propagation of inflammation within adipose tissues and obesity-related metabolic diseases. Angptl2 mRNA and protein are abundantly expressed in hyperplastic rheumatoid synovium of RA patients, especially in fibroblast-like and macrophage-like synoviocytes, but not in B and T lymphocytes. Angptl2 concentration in joints of RA patients was also significantly increased in comparison with patients with osteoarthritis, which in comparison with RA represents a significantly lower inflammatory grade form of arthritis. Notably, Angptl2 promoted increased chemotactic activities of CD14+CD16−monocytes from synovial fluid of RA patients. Therefore, Angptl2 acts as an important rheumatoid synovium-derived inflammatory mediator in RA pathogenesis.

The endoplasmic reticulum (ER) is the site of synthesis and maturation of proteins, designed for secretion, and the cell membrane. Various types of stress from both inside and outside of cells disturb ER function, and unfolded or misfolded proteins accumulate in the ER. The accumulation of these abnormal proteins in the ER further disturbs ER function and cell survival can be threatened. To improve and maintain ER functions against such stress, the ER stress response pathway is activated. When the stress is too severe to maintain ER function, apoptosis pathways are activated to remove damaged cells to protect organs and the whole body. However, when a large number of cells are lost through apoptosis, disturbance of organ function is induced. Therefore, ER stress-induced apoptosis is involved in various diseases, including diabetes, ischemic diseases, atherosclerosis, and heart failure. The transcription factor CHOP/GADD153 is induced by ER stress, and is involved in ER stress-induced apoptosis. CHOP is a member of the CCAAT/enhancer binding proteins (C/EBPs), and forms heterodimers with other C/EBP family members, and binds to the CHOP-binding site of DNA, which is distinct from the C/EBP-binding site. CHOP is also involved in the process of inflammation, through the activation of pro-IL-1. The pathological roles of CHOP therefore remain to be further investigated.

Although recent reports suggest that the endoplasmic reticulum (ER) stress response is induced in association with the development of inflammatory bowel disease, its role in the pathogenesis of inflammatory bowel disease remains unclear. The CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is a transcription factor that is involved in the ER stress response, especially ER stress-induced apoptosis. In this study, we found that experimental colitis was ameliorated in CHOP-null mice, suggesting that CHOP exacerbates the development of colitis. The mRNA expression of Mac-1(CD11b, a positive regulator of macrophage infiltration), Ero-1α, and Caspase-11(a positive regulator of interleukin-1β production) in the intestine was induced with the development of colitis, and this induction was suppressed in CHOP-null mice. ERO-1α is involved in the production of reactive oxygen species (ROS); an increase in ROS production, which is associated with the development of colitis in the intestine, was suppressed in CHOP-null mice. A greater number of apoptotic cells in the intestinal mucosa of wild-type mice were observed to accompany the development of colitis compared with CHOP-null mice, suggesting that up-regulation of CHOP expression exacerbates the development of colitis. Furthermore, this CHOP activity appears to involve various stimulatory mechanisms, such as macrophage infiltration via the induction of Mac-1, ROS production via the induction of ERO-1α, interleukin-1β production via the induction of Caspase-11, and intestinal mucosal cell apoptosis.

Preventing signaling by ANGPTL2, which is stimulated by the tumor microenvironment, could inhibit metastasis.