Mingyong Liu

Vascular Endothelial Growth Factor Receptor 2 (VEGFR-2) Plays a Key Role in Vasculogenic Mimicry Formation, Neovascularization and Tumor Initiation by Glioma Stem-like Cells

Human glioblastomas (GBM) are thought to be initiated by glioma stem-like cells (GSLCs). GSLCs also participate in tumor neovascularization by transdifferentiating into vascular endothelial cells. Here, we report a critical role of GSLCs in the formation of vasculogenic mimicry (VM), which defines channels lined by tumor cells to supply nutrients to early growing tumors and tumor initiation. GSLCs preferentially expressed vascular endothelial growth factor receptor-2 (VEGFR-2) that upon activation by VEGF, mediated chemotaxis, tubule formation and increased expression of critical VM markers by GSLCs. Knockdown of VEGFR-2 in GSLCs by shRNA markedly reduced their capacity of self-renewal, forming tubules, initiating xenograft tumors, promoting vascularization and the establishment of VM. Our study demonstrates VEGFR-2 as an essential molecule to sustain the “stemness” of GSLCs, their capacity to initiate tumor vasculature, and direct initiation of tumor.

Monocyte Chemoattractant Protein-1/CCL2 Produced by Stromal Cells Promotes Lung Metastasis of 4T1 Murine Breast Cancer Cells

MCP-1/CCL2 plays an important role in the initiation and progression of cancer. Since tumor cells produce MCP-1, they are considered to be the main source of this chemokine. Here, we examined whether MCP-1 produced by non-tumor cells affects the growth and lung metastasis of 4T1 breast cancer cells by transplanting them into the mammary pad of WT or MCP-1−/− mice. Primary tumors at the injected site grew similarly in both mice; however, lung metastases were markedly reduced in MCP-1−/− mice, with significantly longer mouse survival. High levels of MCP-1 mRNA were detected in tumors growing in WT, but not MCP-1−/− mice. Serum MCP-1 levels were increased in tumor-bearing WT, but not MCP-1−/− mice. Transplantation of MCP-1−/− bone marrow cells into WT mice did not alter the incidence of lung metastasis, whereas transplantation of WT bone marrow cells into MCP-1−/− mice increased lung metastasis. The primary tumors of MCP-1−/− mice consistently developed necrosis earlier than those of WT mice and showed decreased infiltration by macrophages and reduced angiogenesis. Interestingly, 4T1 cells that metastasized to the lung constitutively expressed elevated levels of MCP-1, and intravenous injection of 4T1 cells producing a high level of MCP-1 resulted in increased tumor foci in the lung of WT and MCP-1−/− mice. Thus, stromal cell-derived MCP-1 in the primary tumors promotes lung metastasis of 4T1 cells, but tumor cell-derived MCP-1 can also contribute once tumor cells enter the circulation. A greater understanding of the source and role of this chemokine may lead to novel strategies for cancer treatment.

Formylpeptide receptors are critical for rapid neutrophil mobilization in host defense against Listeria monocytogenes

Listeria monocytogenes (Listeria) causes opportunistic infection in immunocompromised hosts with high mortality. Resistance to Listeria depends on immune responses and recruitment of neutrophils of the immune system into infected sites is an early and critical step. Mouse neutrophils express two G protein-coupled formylpeptide receptor subtypes Fpr1 and Fpr2 that recognize bacterial and host-derived chemotactic molecules including Listeria peptides for cell migration and activation. Here we report deficiency in Fprs exacerbated the severity of the infection and increased the mortality of infected mice. The mechanism involved impaired early neutrophil recruitment to the liver with Fpr1 and Fpr2 being sole receptors for neutrophils to sense Listeria chemoattractant signals and for production of bactericidal superoxide. Thus, Fprs are essential sentinels to guide the first wave of neutrophil infiltration in the liver of Listeria-infected mice for effective elimination of the invading pathogen.

Cell Surface Receptor FPR2 Promotes Antitumor Host Defense by Limiting M2 Polarization of Macrophages

FPR2 (Fpr2 in mouse) is a G-protein-coupled receptor interacting with bacterial and host-derived chemotactic agonists. Fpr2 supports innate and adaptive immune responses as illustrated by the reduction in severity of allergic airway inflammation in Fpr2-KO mice, due to impaired trafficking of antigen-presenting dendritic cells (DC). The aim of this study is to examine the role of Fpr2 in host antitumor responses. We found that Fpr2-KO mice bearing subcutaneously implanted Lewis lung carcinoma (LLC) cells exhibited significantly shortened survival than normal mice due to more rapidly growing tumors. In contrast, in Fpr2-transgenic mice overexpressing Fpr2, subcutaneously implanted LLC tumors grew more slowly than those in wild-type (WT) littermates. Investigation of tumor tissues revealed an increased number of macrophages associated with tumors grown in Fpr2-KO mice. Macrophages derived from Fpr2-KO mice showed a more potent chemotactic response to LLC-derived supernatant (LLC Sup), which could be neutralized by an anti-CCL2 antibody. The increased chemotaxis of Fpr2-KO mouse macrophages in response to LLC Sup was due to their higher level expression of CCR4, a chemokine receptor that also recognizes the ligand CCL2. Furthermore, macrophages from Fpr2-KO mice acquired an M2 phenotype after stimulation with LLC Sup. These results suggest that Fpr2 plays an important role in host defense against implanted LLC by sustaining macrophages in an M1 phenotype with more potent antitumor activities.

Spinal trauma in mainland China from 2001 to 2007: an epidemiological study based on a nationwide database.

Study Design. Descriptive epidemiological study. Objective. To determine the epidemiological characteristics of spinal trauma in Mainland China. Summary of Background Data. To date, a large-scale epidemiological analysis of spinal trauma in Mainland China has not been undertaken. Methods. Data were acquired from Chinese Database of Traumas. Patients with International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) coding of 805.x and 806.x (spinal column fracture with and without spinal cord injury) from 2001 to 2007 were identified. Variables assessed included patient demographics, etiology, segmental distribution, and outcomes. Results. A total of 82,720 patients with spinal trauma were identified, accounting for 4.58% of all trauma patients in the study period. Spinal cord injuries (SCIs) and fracture-dislocations accounted for 16.87% and 7.17% of spinal trauma and 0.74% and 0.32% of all traumas in the same period, respectively. The male-to-female ratio was 2.33:1. About 79.32% of spinal trauma occurred in patients between 20 and 60 years of age. There was an annual increase in incidence during the study period. A total of 64,630 patients (78.13%) had a definitive cause, with motor vehicle accidents identified as the leading etiological factor (33.61%), followed by high falls (31.25%) and trivial falls (23.23%). Lumbar spine was most frequently involved (56.09%), followed by thoracic spine (23.77%), cervical spine (17.75%), and sacrococcygeal vertebrae (2.39%). Fracture-dislocation occurred most frequently in the cervical and lumbar spines, whereas spinal cord injury occurred most frequently in the cervical and thoracic spines. Children younger than 10 years of age were prone to cervical spine injury, whereas adults older than 60 years were more prone to osteoporotic thoracic and lumbar fractures. Overall rate of conservative treatment (55.88%) was higher than that of operative treatment (44.12%). Overall combined cure and improvement rates exceeded 90%. The male mortality rate was twice that of the female population. Lumbar spine injury was the most curable, whereas cervical spine injury was associated with the worst prognosis and the highest medical costs. Conclusion. This is the first large-scale epidemiological study of spinal injury in Mainland China. The results obtained have important implications for future public health care planning, public safety, and resource allocation.

G protein-coupled receptor FPR1 as a pharmacologic target in inflammation and human glioblastoma.

Formylpeptide receptor1 (FPR1) is a G protein-coupled receptor (GPCR) originally identified in phagocytic leucocytes and mediates cell chemotaxis and activation in response to bacterial formylated chemotactic peptides. However, FPR1 also participates in a signal relay which regulates the infiltration of phagocytes, in particular neutrophils, to inflammatory sites in response to tissue-derived chemoattractant ligands. In addition to participating in innate immune responses, recently, FPR1 has been shown to be expressed by highly malignant glioblastoma (GBM) cells. Upon activation by an endogenous agonist Annexin 1 (Anx A1) released by necrotic glioma cells, FPR1 transactivates the receptor for epithelial growth factor (EGFR) and consequently to promote glioma cell chemotaxis, invasion, growth and production of angiogenic factors. The observations demonstrate that FPR1, as a multifunctional GPCR with pattern recognition properties, is not only involved in innate immune responses but also in the progression of GBM. Thus, FPR1 is an immunopharmacologic target for development of novel therapies.

Signal Relay by CC Chemokine Receptor 2 (CCR2) and Formylpeptide Receptor 2 (Fpr2) in the Recruitment of Monocyte-derived Dendritic Cells in Allergic Airway Inflammation

Background: Chemoattractant receptor Fpr2 interacts with host-derived agonists and mediates leukocyte trafficking. Results: In the lung of allergic inflammation, chemokine receptor CCR2 elicits accumulation of monocyte-derived DC in perivascular region, but Fpr2 is critical for cell trafficking to peribronchiolar area. Conclusion: CCR2 and Fpr2 sequentially guide DC trafficking in inflamed lung. Significance: DC trafficking is controlled by multiple chemoattractant receptors, which are potential therapeutic targets. Chemoattractant receptors regulate leukocyte accumulation at sites of inflammation. In allergic airway inflammation, although a chemokine receptor CCR2 was implicated in mediating monocyte-derived dendritic cell (DC) recruitment into the lung, we previously also discovered reduced accumulation of DCs in the inflamed lung in mice deficient in formylpeptide receptor Fpr2 (Fpr2−/−). We therefore investigated the role of Fpr2 in the trafficking of monocyte-derived DCs in allergic airway inflammation in cooperation with CCR2. We report that in allergic airway inflammation, CCR2 mediated the recruitment of monocyte-derived DCs to the perivascular region, and Fpr2 was required for further migration of the cells into the bronchiolar area. We additionally found that the bronchoalveolar lavage liquid from mice with airway inflammation contained both the CCR2 ligand CCL2 and an Fpr2 agonist CRAMP. Furthermore, similar to Fpr2−/− mice, in the inflamed airway of CRAMP−/− mice, DC trafficking into the peribronchiolar areas was diminished. Our study demonstrates that the interaction of CCR2 and Fpr2 with their endogenous ligands sequentially mediates the trafficking of DCs within the inflamed lung.

Formylpeptide Receptors Mediate Rapid Neutrophil Mobilization to Accelerate Wound Healing

Wound healing is a multi-phased pathophysiological process requiring chemoattractant receptor-dependent accumulation of myeloid cells in the lesion. Two G protein-coupled formylpeptide receptors Fpr1 and Fpr2 mediate rapid neutrophil infiltration in the liver of Listeria-infected mice by sensing pathogen-derived chemotactic ligands. These receptors also recognize host-derived chemotactic peptides in inflammation and injury. Here we report the capacity of Fprs to promote the healing of sterile skin wound in mice by initiating neutrophil infiltration. We found that in normal miceneutrophils rapidly infiltrated the dermis in the wound before the production of neutrophil-specific chemokines by the injured tissue. In contrast, rapid neutrophil infiltration was markedly reduced with delayed wound closure in mice deficient in both Fprs. In addition, we detected Fpr ligand activity that chemoattracted neutrophils into the wound tissue. Our study thus demonstrates that Fprs are critical for normal healing of the sterile skin wound by mediating the first wave of neutrophil infiltration.

A Novel Operative Approach for the Treatment of Old Distractive Flexion Injuries of Subaxial Cervical Spine

Study Design. Retrospective study of 9 patients who underwent operations as treatments of old distractive flexion injuries (DFI, Stage 2 and 3) of subaxial cervical spine. Objective. Description of a novel operative sequence for reduction and stabilization of old DFI of subaxial cervical spine, and assessment of the clinical outcome. Summary of Background Data. Subaxial cervical spine injuries are often missed on the primary trauma survey. However, there is a relative paucity of published clinical data regarding the treatment of old DFI (≥3 weeks) of subaxial cervical spine. Our technique minimizes the total number of necessary procedures and differs in sequence from previously reported methods. Methods. Between January 2001 and January 2004, 9 patients with old DFI (Stage 2 and 3) of subaxial cervical spine underwent operative treatments and were followed-up for at least 2 years. A posterior procedure was conducted first, comprised of soft tissue release, facetectomy and interspinous wiring. Subsequent anterior procedure included soft tissue release, discectomy, reduction, intervertebral grafting, and anterior plating. One functional spinal unit was fused in this group. Neck pain, neurologic status, and radiographs were recorded throughout the patient’s course. Results. Intraoperative anatomic reduction was achieved by this technique in all patients. Neck pain significantly remitted after the operation and neurologic function improved. All involved segments maintained the anatomic reduction until bony fusion was achieved, with the exception of one case of DFI (Stage 3) at C6–C7 level, who lost partial reduction but achieved fusion ultimately. Conclusion. Using the posterior-anterior procedures, anatomic reduction was successfully achieved for old DFI of subaxial cervical spine, with decreased need to turn patients during operative interventions compared with previously reported techniques. Segmental stability was maintained till fusion, with the exception of one case of DFI at the C6–C7 level. Preliminary clinical outcomes were satisfying.

Formylpeptide Receptors Promote the Migration and Differentiation of Rat Neural Stem Cells

Neural stem cells (NSCs) bear characteristics for proliferation, migration and differentiation into three main neural cell type(s): neurons, astrocytes and/or oligodendrocytes. Formylpeptide receptors (Fprs), belonging to the family of G protein-coupled chemoattractant receptors, have been detected on neurons in the central nervous system (CNS). Here, we report that Fpr1 and Fpr2 are expressed on NSCs as detected with immunohistochemistry, RT-PCR and WB assays. In addition, Fpr1 and Fpr2 promoted NSC migration through F-actin polymerization and skewed NSC differentiation to neurons. Our study demonstrates a unique role of Fpr1 and Fpr2 in NSCs and opens a novel window for cell replacement therapies for brain and spinal cord injury.