Placental growth factor promotes tumour desmoplasia and treatment resistance in intrahepatic cholangiocarcinoma.

OBJECTIVE: Intrahepatic cholangiocarcinoma (ICC)-a rare liver malignancy with limited therapeutic options-is characterised by aggressive progression, desmoplasia and vascular abnormalities. The aim of this study was to determine the role of placental growth factor (PlGF) in ICC progression. DESIGN: We evaluated the expression of PlGF in specimens from ICC patients and assessed the therapeutic effect of genetic or pharmacologic inhibition of PlGF in orthotopically grafted ICC mouse models. We evaluated the impact of PlGF stimulation or blockade in ICC cells and cancer-associated fibroblasts (CAFs) using in vitro 3-D coculture systems. RESULTS: PlGF levels were elevated in human ICC stromal cells and circulating blood plasma and were associated with disease progression. Single-cell RNA sequencing showed that the major impact of PlGF blockade in mice was enrichment of quiescent CAFs, characterised by high gene transcription levels related to the Akt pathway, glycolysis and hypoxia signalling. PlGF blockade suppressed Akt phosphorylation and myofibroblast activation in ICC-derived CAFs. PlGF blockade also reduced desmoplasia and tissue stiffness, which resulted in reopening of collapsed tumour vessels and improved blood perfusion, while reducing ICC cell invasion. Moreover, PlGF blockade enhanced the efficacy of standard chemotherapy in mice-bearing ICC. Conclusion PlGF blockade leads to a reduction in intratumorous hypoxia and metastatic dissemination, enhanced chemotherapy sensitivity and increased survival in mice-bearing aggressive ICC.

Dual Programmed Death Receptor-1 and Vascular Endothelial Growth Factor Receptor-2 Blockade Promotes Vascular Normalization and Enhances Antitumor Immune Responses in Hepatocellular Carcinoma.

BACKGROUND AND AIMS: Activation of the antitumor immune response using programmed death receptor-1 (PD-1) blockade showed benefit only in a fraction of patients with hepatocellular carcinoma (HCC). Combining PD-1 blockade with antiangiogenesis has shown promise in substantially increasing the fraction of patients with HCC who respond to treatment, but the mechanism of this interaction is unknown. APPROACH AND RESULTS: We recapitulated these clinical outcomes using orthotopic-grafted or induced-murine models of HCC. Specific blockade of vascular endothelial receptor 2 (VEGFR-2) using a murine antibody significantly delayed primary tumor growth but failed to prolong survival, while anti-PD-1 antibody treatment alone conferred a minor survival advantage in one model. However, dual anti-PD-1/VEGFR-2 therapy significantly inhibited primary tumor growth and doubled survival in both models. Combination therapy reprogrammed the immune microenvironment by increasing cluster of differentiation 8-positive (CD8+ ) cytotoxic T cell infiltration and activation, shifting the M1/M2 ratio of tumor-associated macrophages and reducing T regulatory cell (Treg) and chemokine (C-C motif) receptor 2-positive monocyte infiltration in HCC tissue. In these models, VEGFR-2 was selectively expressed in tumor endothelial cells. Using spheroid cultures of HCC tissue, we found that PD-ligand 1 expression in HCC cells was induced in a paracrine manner upon anti-VEGFR-2 blockade in endothelial cells in part through interferon-gamma expression. Moreover, we found that VEGFR-2 blockade increased PD-1 expression in tumor-infiltrating CD4+ cells. We also found that under anti-PD-1 therapy, CD4+ cells promote normalized vessel formation in the face of antiangiogenic therapy with anti-VEGFR-2 antibody. CONCLUSIONS: We show that dual anti-PD-1/VEGFR-2 therapy has a durable vessel fortification effect in HCC and can overcome treatment resistance to either treatment alone and increase overall survival in both anti-PD-1 therapy-resistant and anti-PD-1 therapy-responsive HCC models.

Hatched "egg" of thymoma with sarcoidosis.

BACKGROUND: While calcification of thymoma is common, "eggshell" calcification is rare. We report a case of an eggshell calcified thymoma that "hatched" after 4 years of follow-up. Pathologically, it revealed that sarcoidosis accompanied this case of thymoma, which might cause in calcification. CASE PRESENTATION: The patient was a 68-year-old female. A 20-mm anterior mediastinal nodule completely covered with calcification was noted in an annual health check-up. However, as the nodule did not change during 6 months of follow-up, she discontinued regular examinations. Four years later, an abnormality in her chest X-ray was noted again. The tumor grew outside the calcification to reach 63 mm. She underwent resection of this anterior mediastinal tumor. Pathologically, the tumor was diagnosed as thymoma of type B1 in the WHO classification. The histology of the tumor inside and outside of the calcification was not different, suggesting that the tumor grew from the inside of the calcification. The calcification was located within the fibrotic capsule of thymoma. Sarcoidosis also presented in her lung and mediastinal lymph nodes. CONCLUSIONS: Although the mechanism of calcification of the capsule was not clear, sarcoidosis might be related to this case because macrophage accumulation and altered lipid metabolism in sarcoidosis present with similar dystrophic calcification.

CXCR4 inhibition in tumor microenvironment facilitates anti-programmed death receptor-1 immunotherapy in sorafenib-treated hepatocellular carcinoma in mice.

UNLABELLED: Sorafenib, a broad tyrosine kinase inhibitor, is the only approved systemic therapy for advanced hepatocellular carcinoma (HCC) but provides limited survival benefits. Recently, immunotherapy has emerged as a promising treatment strategy, but its role remains unclear in HCCs, which are associated with decreased cytotoxic CD8(+) T-lymphocyte infiltration in both murine and human tumors. Moreover, in mouse models after sorafenib treatment intratumoral hypoxia is increased and may fuel evasive resistance. Using orthotopic HCC models, we now show that increased hypoxia after sorafenib treatment promotes immunosuppression, characterized by increased intratumoral expression of the immune checkpoint inhibitor programmed death ligand-1 and accumulation of T-regulatory cells and M2-type macrophages. We also show that the recruitment of immunosuppressive cells is mediated in part by hypoxia-induced up-regulation of stromal cell-derived 1 alpha. Inhibition of the stromal cell-derived 1 alpha receptor (C-X-C receptor type 4 or CXCR4) using AMD3100 prevented the polarization toward an immunosuppressive microenvironment after sorafenib treatment, inhibited tumor growth, reduced lung metastasis, and improved survival. However, the combination of AMD3100 and sorafenib did not significantly change cytotoxic CD8(+) T-lymphocyte infiltration into HCC tumors and did not modify their activation status. In separate experiments, antibody blockade of the programmed death ligand-1 receptor programmed death receptor-1 (PD-1) showed antitumor effects in treatment-naive tumors in orthotopic (grafted and genetically engineered) models of HCC. However, anti-PD-1 antibody treatment had additional antitumor activity only when combined with sorafenib and AMD3100 and not when combined with sorafenib alone. CONCLUSION: Anti-PD-1 treatment can boost antitumor immune responses in HCC models; when used in combination with sorafenib, anti-PD-1 immunotherapy shows efficacy only with concomitant targeting of the hypoxic and immunosuppressive microenvironment with agents such as CXCR4 inhibitors.

Neutrophil-Lymphocyte Ratio as a Prognostic Marker for Lung Adenocarcinoma After Complete Resection.

BACKGROUNDS: The neutrophil-lymphocyte ratio (NLR) is a simple and low-cost index that may be a benchmark for systemic inflammatory response and antitumor immunity. The goal of the study was to investigate the prognostic value of preoperative NLR in patients with lung adenocarcinoma after complete resection. METHODS: The subjects were 361 consecutive patients with lung adenocarcinoma who underwent complete resection between 2000 and 2009. Perioperative clinical and laboratory data were evaluated retrospectively. The cohort was divided using the cut-off value for preoperative NLR identified in receiver operating characteristic analysis. Correlations of NLR with clinicopathological characteristics and prognosis were examined. RESULTS: A high NLR was significantly correlated with a smoking history >10 pack-years (p = 0.023), pathological stage II or III (p < 0.001), lymphatic invasion (p = 0.003), and pleural invasion (p = 0.039). In univariate analysis, the high NLR group had significantly lower 5-year overall survival (86.0 vs. 77.1 %, p < 0.001) and 5-year recurrence-free survival (75.1 vs. 59.9 %, p < 0.001). Multivariate analysis showed that NLR was an independent prognostic factor (hazard ratio 1.822, 95 % confidence interval 1.133-2.931, p = 0.013). CONCLUSION: These results show that preoperative NLR is an independent prognostic factor in patients with lung adenocarcinoma after complete resection. NLR may reflect host immunity and systemic inflammation that facilitates tumor growth.

Immune checkpoint blockade in hepatocellular carcinoma: current progress and future directions.

Immune checkpoint blockade has recently emerged as a promising therapeutic approach for various malignancies including hepatocellular carcinoma (HCC). Preclinical and clinical studies have shown the potential benefit of modulating the immunogenicity of HCC. In addition, recent advances in tumor immunology have broadened our understanding of the complex mechanism of immune evasion. In this review we summarize the current knowledge on HCC immunology and discuss the potential of immune checkpoint blockade as a novel HCC therapy from the basic, translational, and clinical perspectives.

Prognostic Significance of Preoperative Neutrophil-Lymphocyte Ratios in Patients with Stage I Non-small Cell Lung Cancer After Complete Resection.

BACKGROUND: The immune system has been shown to play an important role in preventing cancer progression. The neutrophil-lymphocyte ratio (NLR) has been proposed to be an indicator of a systemic inflammatory response. We investigated the prognostic significance of NLR in patients with completely resected stage I non-small lung cancer (NSCLC). METHODS: A series of 343 pathological stage I NSCLC patients, completely resected between 2000 and 2008 at a single institution, were evaluated retrospectively. Perioperative clinical and laboratory data were collected, and the cohort was divided into two groups according to preoperative NLR. We examined the correlation between NLR and clinicopathological parameters and determined the prognostic significance. RESULTS: High NLR was significantly correlated with patients of older age (p = 0.045), preoperative hypoalbuminemia (p = 0.030), and nonadenocarcinoma histology (p = 0.045). Upon univariate analysis, the high NLR group had significantly lower 5-year recurrence-free survival (81.2 vs. 59.9 %, p < 0.001) and 5-year overall survival (89.2 vs. 72.8 %, p < 0.001) than the low NLR group. Multivariate analysis showed that NLR was an independent prognostic factor (hazard ratio 2.141, 95 % confidence interval; 1.306-3.515, p = 0.003). In terms of initial recurrent sites, the proportion of patients who developed distant metastasis was significantly higher in the high NLR group than in the low NLR group (p < 0.001). CONCLUSIONS: Preoperative high NLR is a significant predictor of poor prognosis and is associated with more frequent distant metastasis in patients with completely resected stage I NSCLC. This readily available and simply calculated ratio provides useful information for the clinician to consider in terms of perioperative management.

Carbon monoxide-releasing molecule attenuates allograft airway rejection.

Acute rejection after lung transplantation is the main risk factor for the development of bronchiolitis obliterans (BO). Carbon monoxide (CO) can provide anti-inflammatory effects and may serve to limit tissue injury in airway transplant. Here, we tested the ability of carbon monoxide releasing molecule-2 (CORM-2) to prevent airway rejection. Tracheal grafts from BALB/c or C57BL/6 were transplanted to C57BL/6 recipients. Experimental groups were treated with multiple doses of CORM-2. Histopathological evaluation of luminal obliteration was blindly reviewed. Immunohistochemistry and real-time RT-PCR analyses were performed. Allografts treated with CORM-2 revealed a striking reduction of thickening in epithelial and subepithelial airway layers (P < 0.01) at day 7 in orthotopic trachea transplantation model compared with allografts treated with vehicle. In heterotopic trachea transplantation model, CORM-2 treated allografts showed a reduction of luminal obliteration (P < 0.01) at days 14 and 21. There was also a concordant decrease in CD3(+) lymphocytes and macrophages in CORM-2 treated allografts. IFN-γ, IL-2 and IL17A mRNA expressions were reduced dramatically by systemic administration of CORM-2. These data implicate CORM-2-derived CO has an important protective function in experimental BO, and may represent a target for the therapeutic intervention of chronic lung allograft rejection.

Comprehensive treatment approach is necessary for the closure of open window thoracostomy: an institutional review of 35 cases.

PURPOSE: Although life-threatening situations can be avoided using an open window thoracostomy (OWT), the closure is often difficult. We investigated the predictors of a successful closure of an OWT at the time of OWT creation. METHODS: Thirty-five consecutive patients who underwent an OWT at our institute between January 1991 and December 2010 were reviewed. We directly compared the patients with and without a successful OWT closure. A logistic regression analysis was employed to determine the predictive factors of a successful closure. RESULTS: OWT closure was only achieved in 12 patients. The closure of the OWT and absence of diabetes mellitus significantly influenced the survival of the OWT patients. The OWT in patients with preceding lung resection was difficult to close, especially if the underlying disease was lung cancer. The existence of a bronchopleural fistula (BPF) was not related to successful closure. Among the post-lung resection patients, the nutritional status tended to affect the success of the closure. CONCLUSION: Successful closure is difficult to predict at the time of the creation of an OWT. A comprehensive approach, including nutritional support and the precise timing of intervention is critical to promote a successful closure.

[Resection and reconstruction of sternum].

We have experienced 6 cases with resection and reconstruction of sternum. They were 1 with osteosarcoma, 1 with synovial sarcoma, 1 with sternal metastasis of fallopian tube cancer, 1 with sternal metastasis of thyroid cancer, 1 with desmoid tumor, and 1 with dermatofibrosarcoma protuberance. Resection of both manubrium and sternum was performed in 3 cases and sternum resection in 3. There was no total resection. We used a titanium reconstruction plate and titanium mesh in 3 cases, a titanium reconstruction plate and polypropylene mesh in 2, titanium mesh in 1 for reconstruction of bony defect, and rectus abdominis myocutaneous flap in 3, pectralis major muscle flap in 2, latissimus doris myocutaneous flap in 1 for reconstruction of soft tissue defect. Postoperative courses were uneventful, and flail chest was not observed. Reconstruction of the bony defect of the anterior chest wall with the titanium reconstruction plate and titanium mesh or polypropylene mesh was effective by providing sufficient rigidity as well as protection of the thoracic organs.

Using hemoglobin vesicles to treat operative hemorrhagic shock after pneu- monectomy in dog models: an experimental study.

Hemoglobin vesicles (HbVs), considered as red blood cell substitutes, are liposomes encapsulating purified hemoglobin, with a phospholipid bilayer membrane (diameter: 250 nm; P50, 28 Torr). In this study, we aimed to investigate HbV function during hemorrhagic shock in lung resection and analyze the details of oxygen delivery. Left pneumonectomy was performed in dogs under mechanical ventilation, followed by rapid exsanguination of approximately 30% of the total circulating blood volume, which led to shock, reducing the mean arterial pressure (MAP) by approximately 60% of baseline. Subsequently, either 5% human serum albumin (HSA) or HbVs suspended in 5% HSA were infused for resuscitation. The MAP only recovered to 75% of baseline after HSA administration, but fully recovered (100%) after HbV administration, with significant differences between the groups (P < 0.005). Oxygen delivery was restored in the HbV group and was significantly higher than that in the HSA group (P < 0.0001). The infusion of HbVs dispersed in a 5% HSA solution compensated for the rapid loss of approximately 30% of the total circulating blood volume in a dog pneumonectomy model, even with impaired lung function. Thus, HbVs can be used for resuscitation from hemorrhagic shock during thoracic surgery.

Surgical resection of a thymoma developed in a case with isolated persistent left superior vena cava.

INTRODUCTION: Persistent left superior vena cava (PLSVC) is one of the most common vascular abnormalities in the chest. In approximately 10 % of cases, the right superior vena cava is missing, which is called isolated persistent left superior vena cava (IPLSVC). PRESENTATION OF CASE: The case is an 85 years-old female. An anterior mediastinal tumor was accidentally revealed when the patient was admitted after a traffic accident. As the tumor became larger within four months, a thymectomy was planned. The anterior mediastinal tumor was in front of the ascending aorta, which was close to the confluence of the left and right brachiocephalic veins in normal anatomy. However, in this case, the right superior vena cava was missing, and the right brachiocephalic vein flowed into the left superior vena cava by the chest computed tomography. Preoperative examinations found no accompanying cardiac abnormality. Robot-assisted thymectomy was performed. No tumor infiltration was observed in the right brachiocephalic vein. No abnormality was found in either phrenic nerve. The tumor could be safely resected, and her postoperative course was uneventful. The pathological diagnosis was a thymoma. DISCUSSION: A case of thymectomy with IPLSVC is quite rare. A careful observation of the preoperative computed tomography images helps to diagnose IPLSVC. Technically, thymectomy was not much different from normal, other than the reversed location of the veins. However, it should be noted that IPLSVC cases may have cardiac malformations. CONCLUSION: Thymectomy for thymoma with IPLSVC can be safely performed when the left and right veins are reversed.

A case of cerebral infarction due to aplastic or twig-like middle cerebral artery after lung cancer surgery.

Aplastic/twig-like middle cerebral artery is a rare vascular abnormality. We report a case of postoperative cerebral infarction caused by this disease. The patient is a male in his 40s. A 9-cm tumour was revealed to have invaded the superior vena cava from his right lung. He underwent right upper and middle bilobectomy. Due to the vascular invasion, the intraoperative bleeding exceeded 2 litres. Mechanical ventilation was required for postoperative pneumonia. After extubation, he was unable to write and was found to have cerebral infiltration in the left middle cerebral artery region. The cause of the cerebral infarction was investigated, but no thrombus in the left atrium or arteriosclerosis was found. No atrial fibrillation was observed during or after the surgery. Magnetic resonance angiography of the brain revealed an aplastic/twig-like middle cerebral artery.

Early reperfusion with hemoglobin vesicles into tracheal subepithelial capillaries in a mouse tracheal transplant model.

Hemoglobin vesicles (HbVs), liposomes containing concentrated hemoglobin extracted from outdated human red blood cells (RBC), are artificial oxygen carriers with a small particle size. To evaluate the reperfusion of capillaries with HbVs in a tracheal transplant model and compare it with that of RBC. Isogenic mice were used as donors and recipients in a parallel trachea transplant model. Both ends of the donor trachea were anastomosed end-laterally to the recipient trachea to form in parallel. After transplantation, 0.3 mL of HbV solution (Hb concentration, 10 g/dL) was administered via the tail vein. The recipients were euthanized 1, 4, 6, and 8 h after surgery (n = 5 in each group). The tracheas were harvested, and tracheal subepithelial capillaries (SEC) reperfusion was histologically evaluated. A significant number of particles defined as HbV by electron microscopy were observed in the SEC of the grafted tracheas 4 h after the transplant surgery and HbV administration when no RBC were found in the SECs. The number increased 6 and 8 h later. Our findings suggest that HbVs, which are smaller than RBC, can reperfuse the capillaries of grafts earlier than RBCs after transplantation and contribute to the oxygenation of transplanted tissues.

A desmoplastic fibroblastoma that developed in the anterior mediastinum: a case report.

BACKGROUND: Desmoplastic fibroblastoma (also known as collagenous fibroma) is a benign, slowly growing soft-tissue tumor. Most desmoplastic fibroblastomas develop in the limbs, neck, or trunk. A mediastinal origin is quite rare. CASE PRESENTATION: A 32-year-old Asian female was referred to us for the diagnosis and treatment of an anterior mediastinal tumor. The tumor was 80 mm in the largest diameter and was located on the pericardium. No invasion was evident. She underwent resection of the tumor via video-assisted thoracoscopic resection. The tumor was totally encapsulated, and its pedicle was on the pericardium. The resected specimen was very rigid, making it difficult to remove from the intercostal space. Histologically, the tumor was composed of a paucicellular dense collagenous tissue. Mitosis was rarely observed, and cellular atypia was not evident, suggesting that the tumor was benign. We diagnosed the tumor as a desmoplastic fibroblastoma by morphology and immunohistochemistry. CONCLUSIONS: Desmoplastic fibroblastoma of the mediastinum is an extremely rare disease. Preoperative diagnosis is difficult. Early surgical resection is suitable for diagnosis and treatment planning.

A non-invasive thymoma that occurred 29 years after complete resection of a non-invasive thymoma accompanied by a microthymoma.

A 55-year-old woman with a 7 cm non-invasive thymoma and myasthenia gravis had been treated by extended thymectomy via median sternotomy 29 years ago. A microscopic 0.15 cm thymoma (microthymoma) was incidentally found in the thymus during surgery. Twenty-nine years later, a 5 cm thymoma developed in the anterior mediastinum and was surgically treated. The non-invasive first thymoma, the microthymoma and the non-invasive third thymoma were all classified as type AB thymomas according to the World Health Organization (WHO) classification and showed extremely similar histological findings. We think the mechanism underlying the local recurrence of non-invasive thymomas would be intrathymic metastasis because of their clinical and pathological features.

Regorafenib combined with PD1 blockade increases CD8 T-cell infiltration by inducing CXCL10 expression in hepatocellular carcinoma.

BACKGROUND AND PURPOSE: Combining inhibitors of vascular endothelial growth factor and the programmed cell death protein 1 (PD1) pathway has shown efficacy in multiple cancers, but the disease-specific and agent-specific mechanisms of benefit remain unclear. We examined the efficacy and defined the mechanisms of benefit when combining regorafenib (a multikinase antivascular endothelial growth factor receptor inhibitor) with PD1 blockade in murine hepatocellular carcinoma (HCC) models. BASIC PROCEDURES: We used orthotopic models of HCC in mice with liver damage to test the effects of regorafenib-dosed orally at 5, 10 or 20 mg/kg daily-combined with anti-PD1 antibodies (10 mg/kg intraperitoneally thrice weekly). We evaluated the effects of therapy on tumor vasculature and immune microenvironment using immunofluorescence, flow cytometry, RNA-sequencing, ELISA and pharmacokinetic/pharmacodynamic studies in mice and in tissue and blood samples from patients with cancer. MAIN FINDINGS: Regorafenib/anti-PD1 combination therapy increased survival compared with regofarenib or anti-PD1 alone in a regorafenib dose-dependent manner. Combination therapy increased regorafenib uptake into the tumor tissues by normalizing the HCC vasculature and increasing CD8 T-cell infiltration and activation at an intermediate regorafenib dose. The efficacy of regorafenib/anti-PD1 therapy was compromised in mice lacking functional T cells (Rag1-deficient mice). Regorafenib treatment increased the transcription and protein expression of CXCL10-a ligand for CXCR3 expressed on tumor-infiltrating lymphocytes-in murine HCC and in blood of patients with HCC. Using Cxcr3-deficient mice, we demonstrate that CXCR3 mediated the increased intratumoral CD8 T-cell infiltration and the added survival benefit when regorafenib was combined with anti-PD1 therapy. PRINCIPAL CONCLUSIONS: Judicious regorafenib/anti-PD1 combination therapy can inhibit tumor growth and increase survival by normalizing tumor vasculature and increasing intratumoral CXCR3+CD8 T-cell infiltration through elevated CXCL10 expression in HCC cells.

Angiopoietins contribute to lung development by regulating pulmonary vascular network formation.

Angiopoietin (Ang) signaling through the Tie2 receptor regulates vasculature. The role of Ang signaling in pulmonary hypertension is well investigated, but its role in lung development is not elucidated. Here, we show that the Tie2 agonist ligand, Ang1, was detected in lung tissue at birth and its expression gradually increased in mice, whereas its antagonist Ang2 was abundant at birth and decreased inversely with Ang1. Mice expressing the potent chimeric Ang1 protein COMP-Ang1 in surfactant protein C (SPC)-positive lung epithelial cells, showed 50% lethality at birth due to respiratory failure. Surviving mice displayed impaired adaptive responsive respiratory function. Histological analysis revealed that pulmonary artery and alveolar structure were significantly dilated, and alveolar density was decreased to approximately a third of controls. Thus, the precise regulation of Tie2 signaling through an Ang1/Ang2 expression switch is important to construct a mature lung vascular network system required for normal lung development.

Angiopoietin-related growth factor enhances blood flow via activation of the ERK1/2-eNOS-NO pathway in a mouse hind-limb ischemia model.

OBJECTIVE: Transgenic mice overexpressing angiopoietin-related growth factor (AGF) exhibit enhanced angiogenesis, suggesting that AGF may be a useful drug target in ischemic disease. Our goal was to determine whether AGF enhances blood flow in a mouse hind-limb ischemia model and to define molecular mechanisms underlying AGF signaling in endothelial cells. METHODS AND RESULTS: Intramuscular injection of adenovirus harboring AGF into the ischemic limb increased AGF production, which increased blood flow through induction of angiogenesis and arteriogenesis, thereby reducing the necessity for limb amputation. In vitro analysis showed that exposing human umbilical venous endothelial cells to AGF increased nitric oxide (NO) production through activation of an ERK1/2-endothelial NO synthetase (eNOS) signaling pathway. AGF-stimulated eNOS phosphorylation, NO production, and endothelial cell migration were all abolished by specific MEK1/2 inhibitors. Moreover, AGF did not restore blood flow to ischemic hind-limbs of either mice receiving NOS inhibitor L-NAME or eNOS knockout mice. CONCLUSIONS: Activation of an ERK1/2-eNOS-NO pathway is a crucial signaling mechanism by which AGF increases blood flow through induction of angiogenesis and arteriogenesis. Further investigation of the regulation underlying AGF signaling pathway may contribute to develop a new clinical strategy for ischemic vascular diseases.

The role of angiopoietin-like proteins in angiogenesis and metabolism.

Recently, a family of proteins structurally similar to the angiogenic regulating factors angiopoietins was identified and designated "angiopoietin-like proteins" (Angptls). Encoded by seven genes, Angptls 1 to 7 all possess an N-terminal coiled-coil domain and a C-terminal fibrinogen-like domain, both characteristic of angiopoietins. However, Angptls do not bind to either the angiopoietin receptor Tie2 or the related protein Tie1 and remain orphan ligands. Nonetheless, Angptls 1, 2, 3, 4, and Angptl6/angiopoietin-related growth factor function to regulate angiogenesis. Angptls 3, 4, and Angptl6/angiopoietin-related growth factor also appear to directly regulate lipid, glucose, and energy metabolism independently of angiogenic effects. Recently, several lines of evidence reveal differential roles of Angptl structural domains in both angiogenesis and metabolism. Here, we briefly review what is currently known about Angptls function.