Yi Ren

Macrophage migration inhibitory factor: Roles in regulating tumor cell migration and expression of angiogenic factors in hepatocellular carcinoma

Macrophage migration inhibitory factor (MIF) may contribute to multiple aspects of tumor progression, including control of cell proliferation, differentiation, cell survival and angiogenesis. However, the potential roles of MIF in regulating hepatocellular carcinoma (HCC) tumor cell migration and the expression of angiogenic factors by HCC tumor cells have not been studied yet. In our study, we reported that intracellular MIF mRNA and protein were overexpressed in HCC tissues compared to nontumor tissues by using in situ hybridization and immunohistochemic staining. HCC tumor cell lines also secreted large amounts of MIF into the supernatants of tumor cell culture. To assess the role of MIF in HCC, we employed the transwell invasion chamber to study the effect of MIF on tumor cell migration. Our results showed that recombinant MIF and the supernatants of tumor cell line culture could enhance the invasion and migration of HCC cells. This effect can be inhibited by the addition of a neutralizing anti‐MIF antibody. We observed that increased MIF serum levels correlated with higher levels of interleukin‐8 (IL‐8) in the sera of patients with HCC than in normal volunteers. We therefore hypothesized that MIF may regulate the production of angiogenic factors by HCC cells. To test this hypothesis, we examined the effect of MIF treatment on vascular endothelial growth factor (VEGF) and IL‐8 expression by HCC cell lines. MIF induced a significant dose‐dependent increase in IL‐8 and VEGF production. Taken together, our results indicated that MIF may act as an autocrine‐acting factor that stimulates angiogenesis and metastasis in HCC by promoting expression of angiogenic factors and migration of tumor cells. A more detailed understanding of the MIF regulatory mechanisms involved may provide insight into new direction in the treatment of HCC.

Hepatocyte growth factor promotes cancer cell migration and angiogenic factors expression: a prognostic marker of human esophageal squamous cell carcinomas.

Purpose: Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, c-Met, play important roles in tumor development and progression. In this study, we measured the serum HGF levels in patients with esophageal squamous cell carcinoma (ESCC) to evaluate its relationships with clinicopathologic features and the role of HGF in ESCC. Experimental Design: One hundred and forty-nine patients with ESCC were studied. Pretherapy serum was collected and ELISA was used to detect the concentrations of HGF, vascular endothelial growth factor (VEGF), and interleukin 8 (IL-8). The function of HGF was shown by invasion chamber assay. Results: Pretherapy serum HGF was found to be significantly higher in patients with ESCC than in control subjects. The levels of HGF correlated significantly with advanced tumor metastasis stage and survival. Multivariate analyses showed that serum HGF level in cell migration was an independent prognostic factor. Increased HGF serum levels correlated positively with serum levels of VEGF and IL-8. Our results also showed that HGF was overexpressed in ESCC tissues and cell lines. In vitro study showed that HGF could stimulate ESCC cell to express VEGF and IL-8 and markedly enhance invasion and migration of ESCC cells. Furthermore, HGF-induced IL-8 and VEGF expression was dependent on extracellular signal-regulated kinase signaling pathways. The inhibition of extracellular signal-regulated kinase activation reduced HGF-mediated IL-8 and VEGF expression. Conclusions: Our results suggest that serum HGF may be a useful biomarker of tumor progression and a valuable independent prognostic factor in patients with ESCC. HGF may be involved in the progression of ESCC as an autocrine/paracrine factor via enhancing angiogenesis and tumor cell invasion and migration.

Apoptotic Cells Protect Mice against Lipopolysaccharide-Induced Shock

LPS is a main causative agent of septic shock. There is a lack of effective therapies. In vitro studies have shown that uptake of apoptotic cells actively inhibits the secretion by activated macrophages (Mφ) of proinflammatory mediators such as TNF-α and that such uptake increases the antiinflammatory and immunosuppressive cytokine TGF-β. We therefore investigated the protective effect of apoptotic cells against LPS-induced endotoxic shock in mice. The current report is the first study to demonstrate that administration of apoptotic cells can protect mice from LPS-induced death, even when apoptotic cells were administered 24 h after LPS challenge. The beneficial effects of administration of apoptotic cells included 1) reduced circulating proinflammatory cytokines, 2) suppression of polymorphonuclear neutrophil infiltration in target organs, and 3) decreased serum LPS levels. LPS can quickly bind to apoptotic cells and these LPS-coated apoptotic cells can be recognized and cleared by Mφ in a CD14/thrombospondin/vitronectin receptor-dependent manner, accompanied with suppression of TNF-α and enhancement of IL-10 expression by LPS-activated Mφ. Apoptotic cells may therefore have therapeutic potential for the treatment of septic shock.

Nonphlogistic Clearance of Late Apoptotic Neutrophils by Macrophages: Efficient Phagocytosis Independent of β2 Integrins

Neutrophils undergo constitutive death by apoptosis, leading to safe nonphlogistic phagocytosis and clearance by macrophages. Recent work has shown that before secondary necrosis, neutrophils exhibiting classical features of apoptosis can progress to a morphologically defined late apoptotic state. However, whether such neutrophils could be safely cleared was unknown. We now report that human late apoptotic neutrophils could be purified from cultured neutrophil populations undergoing constitutive death and were subsequently ingested by human monocyte-derived macrophages by serum-independent mechanisms that did not trigger the release of IL-8 or TNF-α. Such ingestion was specifically inhibited by Abs to thrombospondin-1 and the αvβ3 vitronectin receptor. Murine bone marrow-derived macrophage phagocytosis of late and early apoptotic neutrophils occurred by similar mechanisms, proceeding with the same efficiency as that observed for wild-type controls when macrophages from αm−/− or β2−/− mice were used. We conclude that specific nonphlogistic, β2 integrin-independent mechanisms involving thrombospondin-1 and αvβ3 allow macrophages to ingest late apoptotic neutrophils without eliciting inflammatory cytokine secretion.

Upregulation of macrophage migration inhibitory factor contributes to induced N-Myc expression by the activation of ERK signaling pathway and increased expression of interleukin-8 and VEGF in neuroblastoma.

Macrophage migration inhibitory factor (MIF) has been linked to fundamental processes such as control of cell proliferation, cell survival, angiogenesis, and tumor progression. The expression of MIF has been reported in several tumors. However, the precise role of MIF in tumor cells remains unclear. In the present study, we investigated the expression pattern and the function of MIF in neuroblastoma. Our results showed that intracellular MIF was upregulated in neuroblastoma tumor tissues and cell lines. MIF protein expression significantly correlated with the grade of tumor differentiation. In addition, we found that MIF induced a significant dose-dependent increase of vascular endothelial growth factor and interleukin-8 secretion. We also observed that an increased MIF expression level correlated with N-Myc protein (the N-myc oncogene product) expression in neuroblastoma tissues. MIF increased the expression of N-myc mRNA and N-Myc protein and induced N-Myc translocation from the cytoplasm to nucleus in neuroblastoma cell lines. MIF-induced N-Myc expression was found to be dependent on ERK signaling pathways. The inhibition of ERK activation reduced MIF-mediated N-Myc expression. These results suggest that MIF may contribute to the progression of neuroblastoma by (a) inducing N-Myc expression and (b) upregulating the expression of angiogenic factors.

Macrophage migration inhibitory factor stimulates angiogenic factor expression and correlates with differentiation and lymph node status in patients with esophageal squamous cell carcinoma.

Objective:The objectives of this study were: 1) to examine the expression of macrophage migration inhibitory factor (MIF) in esophageal squamous cell carcinoma (ESCC); 2) to see if a relationship exists between MIF expression, clinicopathologic features, and long-term prognosis; and 3) to ascertain the possible biologic function of MIF in angiogenesis. Summary Background Data:MIF has been linked to fundamental processes such as those controlling cell proliferation, cell survival, angiogenesis, and tumor progression. Its role in ESCC, and the correlation of MIF expression and tumor pathologic features in patients, has not been elucidated. Methods:The expression of MIF in tumor and nontumor tissues was examined by immunohistochemical staining. Concentrations of MIF, vascular endothelial growth factor (VEGF), and interleukin-8 (IL-8) in patients’ sera and in the supernatant of tumor cells culture were examined by ELISA. Correlations with clinicopathologic factors were made. Results:In 72 patients with ESCC, intracellular MIF was overexpressed in esophagectomy specimens. The expression of MIF correlated with both tumor differentiation and lymph node status. The median survival in the low-MIF expression group (<50% positively stained cancer cells on immunohistochemistry) and high expression group (≥50% positively stained cancer cells) was 28.3 months and 15.8 months, respectively (P = 0.03). The 3-year survival rates for the 2 groups were 37.7% and 12.1%, respectively. MIF expression was related to microvessel density; increased MIF serum levels also correlated with higher serum levels of VEGF. In addition, in vitro MIF stimulation of esophageal cancer cell lines induced a dose-dependent increase in VEGF and IL-8 secretion. Conclusions:These results demonstrate, for the first time, that human esophageal carcinomas express and secrete large amounts of MIF. Through its effects on VEGF and IL-8, MIF may serve as an autocrine factor in angiogenesis and thus play an important role in the pathogenesis of ESCC.

Inhibition of tumor growth and metastasis in vitro and in vivo by targeting macrophage migration inhibitory factor in human neuroblastoma

Macrophage migration inhibitory factor (MIF) has been defined as a novel oncogene. Our previous results have shown that MIF may contribute to the progression of neuroblastoma by (a) inducing N-Myc expression and (b) upregulating the expression of angiogenic factors. The aim of this study was to test whether tumor growth could be inhibited by reduction of endogenous MIF expression in neuroblastoma and clarify the molecular mechanisms underlying MIF reduction on the control of neuroblastoma growth. We established human neuroblastoma cell lines stably expressing antisense MIF (AS-MIF) cDNA. These stable transfectants were characterized by cell proliferation, gene expression profile, tumorigenicity and metastasis in vitro and in vivo. Decreased MIF expression was observed after transfection with AS-MIF in neuroblastoma cells and downregulation of MIF expression significantly correlated with decreased expression of N-Myc, Ras, c-Met and TrkB at protein level. Affymetrix microarray analysis revealed that expression of IL-8 and c-met was inhibited and neuroblastoma-favorable genes such as EPHB6 and BLU were upregulated in MIF reduced cells. Neuroblastoma cell growth exhibited a nearly 80% reduction in AS-MIF transfectants in vitro. Furthermore, mice in which tumors formed after subcutaneous injection of AS-MIF transfectants showed a 90% reduction in tumor growth compared to control. Metastasis in mice was also suppressed dramatically. Our data demonstrate that targeting MIF expression is a promising therapeutic strategy in human neuroblastoma therapy, and also identifies the MIF target genes for further study.

Myelin Activates FAK/Akt/NF-κB Pathways and Provokes CR3-Dependent Inflammatory Response in Murine System

Inflammatory response following central nervous system (CNS) injury contributes to progressive neuropathology and reduction in functional recovery. Axons are sensitive to mechanical injury and toxic inflammatory mediators, which may lead to demyelination. Although it is well documented that degenerated myelin triggers undesirable inflammatory responses in autoimmune diseases such as multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), there has been very little study of the direct inflammatory consequences of damaged myelin in spinal cord injury (SCI), i.e., there is no direct evidence to show that myelin debris from injured spinal cord can trigger undesirable inflammation in vitro and in vivo. Our data showed that myelin can initiate inflammatory responses in vivo, which is complement receptor 3 (CR3)-dependent via stimulating macrophages to express pro-inflammatory molecules and down-regulates expression of anti-inflammatory cytokines. Mechanism study revealed that myelin-increased cytokine expression is through activation of FAK/PI3K/Akt/NF-κB signaling pathways and CR3 contributes to myelin-induced PI3K/Akt/NF-κB activation and cytokine production. The myelin induced inflammatory response is myelin specific as sphingomyelin (the major lipid of myelin) and myelin basic protein (MBP, one of the major proteins of myelin) are not able to activate NF-κB signaling pathway. In conclusion, our results demonstrate a crucial role of myelin as an endogenous inflammatory stimulus that induces pro-inflammatory responses and suggest that blocking myelin-CR3 interaction and enhancing myelin debris clearance may be effective interventions for treating SCI.

Function of microglia and macrophages in secondary damage after spinal cord injury

Spinal cord injury (SCI) is a devastating type of neurological trauma with limited therapeutic opportunities. The pathophysiology of SCI involves primary and secondary mechanisms of injury. Among all the secondary injury mechanisms, the inflammatory response is the major contributor and results in expansion of the lesion and further loss of neurologic function. Meanwhile, the inflammation directly and indirectly dominates the outcomes of SCI, including not only pain and motor dysfunction, but also preventingneuronal regeneration. Microglia and macrophages play very important roles in secondary injury. Microglia reside in spinal parenchyma and survey the microenvironment through the signals of injury or infection. Macrophages are derived from monocytes recruited to injured sites from the peripheral circulation. Activated resident microglia and monocyte-derived macrophages induce and magnify immune and inflammatory responses not only by means of their secretory moleculesand phagocytosis, but also through their influence on astrocytes, oligodendrocytes and demyelination. In this review, we focus on the roles of microglia and macrophages in secondary injury and how they contribute to the sequelae of SCI.

The use of proteomics in the discovery of serum biomarkers from patients with severe acute respiratory syndrome

Severe acute respiratory syndrome (SARS) is a new infectious disease with a global impact. Understanding its pathogenesis and developing specific diagnostic methods for its early diagnosis are crucial for the effective management and control of this disease. By using proteomic technology, truncated forms of α1‐antitrypsin (TF‐α1‐AT) were found to increase significantly and consistently in sera of SARS patients compared to control subjects. The result showed a sensitivity of 100% for SARS patients and a specificity of 92.8% for controls. Furthermore, the levels of these proteins significantly correlated with certain clinico‐pathological parameters. The dramatic increase in TF‐α1‐AT may be the result of degradation of α1‐AT. As α1‐AT plays an important role in the protection of lung function, its degradation may be an important factor in the pathogenesis of SARS. These findings indicate that increased TF‐α1‐AT may be therapeutically relevant, and may also be a useful biological marker for the diagnosis of SARS.