Shear-stress sensing by PIEZO1 regulates tendon stiffness in rodents and influences jumping performance in humans.

Athletic performance relies on tendons, which enable movement by transferring forces from muscles to the skeleton. Yet, how load-bearing structures in tendons sense and adapt to physical demands is not understood. Here, by performing calcium (Ca2+) imaging in mechanically loaded tendon explants from rats and in primary tendon cells from rats and humans, we show that tenocytes detect mechanical forces through the mechanosensitive ion channel PIEZO1, which senses shear stresses induced by collagen-fibre sliding. Through tenocyte-targeted loss-of-function and gain-of-function experiments in rodents, we show that reduced PIEZO1 activity decreased tendon stiffness and that elevated PIEZO1 mechanosignalling increased tendon stiffness and strength, seemingly through upregulated collagen cross-linking. We also show that humans carrying the PIEZO1 E756del gain-of-function mutation display a 13.2% average increase in normalized jumping height, presumably due to a higher rate of force generation or to the release of a larger amount of stored elastic energy. Further understanding of the PIEZO1-mediated mechanoregulation of tendon stiffness should aid research on musculoskeletal medicine and on sports performance.

Exploring the Role of Osteosarcoma-Derived Extracellular Vesicles in Pre-Metastatic Niche Formation and Metastasis in the 143-B Xenograft Mouse Osteosarcoma Model.

The pre-metastatic niche (PMN) is a tumor-driven microenvironment in distant organs that can foster and support the survival and growth of disseminated tumor cells. This facilitates the establishment of secondary lesions that eventually form overt metastasis, the main cause of cancer-related death. In recent years, tumor-derived extracellular-vesicles (EVs) have emerged as potentially key drivers of the PMN. The role of the PMN in osteosarcoma metastasis is poorly understood and the potential contribution of osteosarcoma cell-derived EVs to PMN formation has not been investigated so far. Here, we characterize pulmonary PMN development using the spontaneously metastasizing 143-B xenograft osteosarcoma mouse model. We demonstrate the accumulation of CD11b+ myeloid cells in the pre-metastatic lungs of tumor-bearing mice. We also establish that highly metastatic 143-B and poorly metastatic SAOS-2 osteosarcoma cell-derived EV education in naïve mice can recapitulate the recruitment of myeloid cells to the lungs. Surprisingly, despite EV-induced myeloid cell infiltration in the pre-metastatic lungs, 143-B and SAOS-2 EVs do not contribute towards the 143-B metastatic burden in the context of both spontaneous as well as experimental metastasis in severe-combined immunodeficient (SCID) mice. Taken together, OS-derived EVs alone may not be able to form a functional PMN, and may perhaps require a combination of tumor-secreted factors along with EVs to do so. Additionally, our study gives a valuable insight into the PMN complexity by providing the transcriptomic signature of the premetastatic lungs in an osteosarcoma xenograft model for the first time. In conclusion, identification of regulators of cellular and molecular changes in the pre-metastatic lungs might lead to the development of a combination therapies in the future that interrupt PMN formation and combat osteosarcoma metastasis.

Osteosarcoma-Derived Extracellular Vesicles Induce Lung Fibroblast Reprogramming.

Tumor-secreted extracellular vesicles (EVs) have been identified as mediators of cancer-host intercellular communication and shown to support pre-metastatic niche formation by modulating stromal cells at future metastatic sites. While osteosarcoma, the most common primary malignant bone tumor in children and adolescents, has a high propensity for pulmonary metastases, the interaction of osteosarcoma cells with resident lung cells remains poorly understood. Here, we deliver foundational in vitro evidence that osteosarcoma cell-derived EVs drive myofibroblast/cancer-associated fibroblast differentiation. Human lung fibroblasts displayed increased invasive competence, in addition to increased α-smooth muscle actin expression and fibronectin production upon EV treatment. Furthermore, we demonstrate, through the use of transforming growth factor beta receptor 1 (TGFBR1) inhibitors and CRISPR-Cas9-mediated knockouts, that TGFß1 present in osteosarcoma cell-derived EVs is responsible for lung fibroblast differentiation. Overall, our study highlights osteosarcoma-derived EVs as novel regulators of lung fibroblast activation and provides mechanistic insight into how osteosarcoma cells can modulate distant cells to potentially support metastatic progression.

TRPV4 Inhibition and CRISPR-Cas9 Knockout Reduce Inflammation Induced by Hyperphysiological Stretching in Human Annulus Fibrosus Cells.

Mechanical loading and inflammation interact to cause degenerative disc disease and low back pain (LBP). However, the underlying mechanosensing and mechanotransductive pathways are poorly understood. This results in untargeted pharmacological treatments that do not take the mechanical aspect of LBP into account. We investigated the role of the mechanosensitive ion channel TRPV4 in stretch-induced inflammation in human annulus fibrosus (AF) cells. The cells were cyclically stretched to 20% hyperphysiological strain. TRPV4 was either inhibited with the selective TRPV4 antagonist GSK2193874 or knocked out (KO) via CRISPR-Cas9 gene editing. The gene expression, inflammatory mediator release and MAPK pathway activation were analyzed. Hyperphysiological cyclic stretching significantly increased the IL6, IL8, and COX2 mRNA, PGE2 release, and activated p38 MAPK. The TRPV4 pharmacological inhibition significantly attenuated these effects. TRPV4 KO further prevented the stretch-induced upregulation of IL8 mRNA and reduced IL6 and IL8 release, thus supporting the inhibition data. We provide novel evidence that TRPV4 transduces hyperphysiological mechanical signals into inflammatory responses in human AF cells, possibly via p38. Additionally, we show for the first time the successful gene editing of human AF cells via CRISPR-Cas9. The pharmacological inhibition or CRISPR-based targeting of TRPV4 may constitute a potential therapeutic strategy to tackle discogenic LBP in patients with AF injury.

The miR-143/145 Cluster, a Novel Diagnostic Biomarker in Chondrosarcoma, Acts as a Tumor Suppressor and Directly Inhibits Fascin-1.

Chondrosarcoma is the second most frequent bone sarcoma. Due to the inherent chemotherapy and radiotherapy resistance and absence of known therapeutic targets, clinical management is limited to surgical resection. Consequently, patients with advanced disease face a poor prognosis. Hence, elucidating regulatory networks governing chondrosarcoma pathogenesis is vital for development of effective therapeutic strategies. Here, miRNA and mRNA next generation sequencing of different subtypes of human chondrogenic tumors in combination with in silico bioinformatics tools were performed with the aim to identify key molecular factors. We identified miR-143/145 cluster levels to inversely correlate with tumor grade. This deregulation was echoed in the miRNA plasma levels of patients and we provided the first evidence that circulating miR-145 is a potential noninvasive diagnostic biomarker and can be valuable as an indicator to improve the currently challenging diagnosis of cartilaginous bone tumors. Additionally, artificial upregulation of both miRNAs impelled a potent tumor suppressor effect in vitro and in vivo in an orthotopic xenograft mouse model. A combined in silico/sequencing approach revealed FSCN1 as a direct target of miR-143/145, and its depletion phenotypically resembled miR-143/145 upregulation in vitro. Last, FSCN1 is a malignancy-promoting factor associated with aggressive chondrosarcoma progression. Our findings underscore miR-143/145/FSCN1 as important players in chondrosarcoma and may potentially open new avenues for specific therapeutic intervention options. © 2020 American Society for Bone and Mineral Research.

Fascin-1 enhances experimental osteosarcoma tumor formation and metastasis and is related to poor patient outcome.

BACKGROUND: Fascin-1, a prominent actin-bundling protein, is found to be upregulated in several human carcinomas. While it is accepted that Fascin-1 expression correlates with poor clinical outcome and decreased survival in various carcinomas, its role in sarcoma such as osteosarcoma (OS) remains unknown. In the present study, we evaluated the prognostic value and biological relevance of Fascin-1 in OS. METHODS: The correlation between Fascin-1 expression and the outcome of OS patients was determined by immunohistochemistry analysis of Fascin-1 expression in a tissue microarray of OS tissue specimens collected during primary tumor resection. To examine the effect of Fascin-1, shRNA and overexpression technology to alter Fascin-1 levels in OS cells were used in cellular assays as well as in intratibial xenograft OS models in SCID mice. RESULTS: Kaplan-Meier survival analysis of Fascin-1 expression in OS tumor specimens revealed a direct relationship between Fascin-1 expression and poor patient survival. Furthermore, overexpression of Fascin-1 in OS cells significantly increased their migratory capacity as well as the activity of the matrix metalloprotease MMP-9, known to be critical for the execution of metastasis. Finally, using relevant xenograft mouse models, orthotopic intratibial transplantation of two different OS cell lines overexpressing Fascin-1 promoted tumor growth and lung metastasis. CONCLUSIONS: Collectively, our findings demonstrate for the first time that Fascin-1 has considerable potential as a novel prognostic biomarker in OS, and suggest that targeting of Fascin-1 might be a new anti-metastatic strategy in OS patient treatment.

Exercise right heart catheterisation before and after pulmonary endarterectomy in patients with chronic thromboembolic disease.

Symptomatic patients with chronic thromboembolic disease (CTED) without pulmonary hypertension often show an excessive increase in mean pulmonary arterial pressure (MPAP) during exercise.We report on the impact of pulmonary endarterectomy (PEA) on pulmonary haemodynamics in a prospective series of 32 consecutive CTED patients who underwent PEA. All patients had a comprehensive diagnostic work-up including right heart catheterisation at baseline and 12 months after PEA. Furthermore, in 12 patients exercise right heart catheterisation was performed before and after PEA.After PEA, MPAP was lower at rest (20±3 versus 17±3 mmHg; p=0.008) and during maximal exercise (39±8 versus 31±6 mmHg; p=0.016). The mean total pulmonary resistance (TPR) decreased from 3.6±0.8 Wood Units (WU) pre-operatively to 2.7±0.7 WU 1 year after PEA (p=0.004) and the mean slope of the MPAP/cardiac output (CO) relationship decreased from 3.6±1.0 to 2.3±0.8 WU (p=0.002). Peak oxygen uptake increased from 1.2±0.4 to 1.5±0.3 L·min-1 (p=0.014) and ventilatory equivalents of carbon dioxide decreased from 39±2 to 30±2 (p=0.002). There was a significant improvement in quality of life assessed by the Cambridge Pulmonary Hypertension Outcome Review questionnaire.In CTED patients, PEA resulted in haemodynamic and clinical improvements. The means of TPR and MPAP/CO slopes decreased to <3.0 WU.

Short-term venoarterial extracorporeal membrane oxygenation for massive endobronchial hemorrhage after pulmonary endarterectomy.

OBJECTIVES: Pulmonary endarterectomy (PEA) is the only curative treatment option for patients with chronic thromboembolic pulmonary hypertension. Massive endobronchial bleeding that precludes weaning from cardiopulmonary bypass is an often-fatal complication of PEA. The aim of this study was to determine whether short-term extracorporeal membrane oxygenation (ECMO) is a safe and feasible procedure in patients with severe endobronchial bleeding. METHODS: From January 2014 to December 2016, 396 patients (mean age 60 ± 18 years, 54.5% male) underwent PEA in our department. Patients with severe endobronchial hemorrhage at the time of weaning from cardiopulmonary bypass (CPB) were switched to a heparin-coated venoarterial ECMO circuit. After full-dose protamine administration to restore normal coagulation, weaning from ECMO was attempted in the operating room. RESULTS: In-hospital mortality was 2.3% (9/396 patients). Eight patients (2.0%) developed severe endobronchial bleeding classified as diffuse (n = 6) or localized (n = 2) by bronchoscopy. After reinstitution of CPB and subsequent switch to ECMO, the mean duration of ECMO support was 49 ± 13 minutes, and all 8 patients were weaned successfully from ECMO in the operating theater without further signs of endobronchial bleeding. One patient needed venovenous ECMO support for poor oxygenation 6 hours after surgery. Seven patients were discharged after a prolonged postoperative stay of 17.6 ± 4.1 days. One patient died. This new concept significantly reduced mortality compared with previous (2009-2013) ECMO support (P = .0406). CONCLUSIONS: For patients with massive endobronchial bleeding after PEA, the intraoperative switch from CPB to venoarterial ECMO support with full-dose protamine administration is a new and potentially life-saving treatment concept.

Follow-Up (Measurement) of Corrected QT Interval in Adult Patients before and after Lung Transplantation.

BACKGROUND: Prolongation of the corrected QT (QTc) interval is well known for many drugs, some of which are an integral part of the therapeutic regimen after lung transplantation (LTX). Therefore, we investigated the QTc interval after LTX in the present study. PATIENTS AND METHODS: The medical records of patients after LTX were studied for demographic data, indication of LTX, medication, and baseline and follow-up ECGs. The QT interval was corrected for the patient's heart rate using the different formulae of Bazett, Fridericia, Hodges, and Framingham. RESULTS: Fifty-nine patients were included. The mean age ± SD was 55.6 ± 7.8 years (median 58 years). After LTX, QTc intervals showed no (relevant) changes during follow-up, even though all patients were treated with drugs (in combination) known to bear a risk of prolonged QTc interval and cortisone. The longest QTc intervals were obtained using Bazett's formula. CONCLUSION: The QTc interval did not increase under immunosuppressive medication after LTX in our cohort of patients. We speculate that the concurrent use of cortisone may shorten the QT(c) intervals or cancel out drug-induced prolongation of the QTc interval.

The effective systematic heparin pre-treatment on thrombus formation on pulmonary artery catheter tips during pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension: a randomized, double-blind study.

Pulmonary artery (PA) catheters are routinely used for hemodynamic management in patients with chronic thromboembolic pulmonary hypertension (CTEPH) undergoing pulmonary endarterectomy (PEA). Tip-associated thrombi are frequently detected and might increase the peri-operative risk in these patients. The aim of the study was to investigate the effects of low-dose heparinization before the insertion of the PA catheter on thrombus formation and thrombus weight during PEA surgery. From September 2013 to February 2015, 60 CTEPH patients undergoing PEA were included in the study and randomized into two groups of 30 patients each, including a heparin group (heparin bolus (70 IU per kg body weight) administration before PA catheter insertion) and a control group (pretreatment with placebo). During the PEA procedure the distal part of the PA catheter was drawn out of the PA and thrombus presence and weight were recorded. There were no significant differences in baseline characteristics between the two groups. Twelve patients (20%) had thrombophilic disorders. In the control group, thrombi were detected in 17 patients (57%) with a median thrombus weight of 27 mg (IQR 41). In the heparin group, tip-associated thrombi were found in five patients (17%) with a median weight of 12 mg (IQR 7). There were no bleeding complications in either group. This study demonstrates a high risk of PA catheter-related thrombi in patients with CTEPH. Prophylactic administration of low-dose heparin reduces thrombus formation and thrombus weight without an increased rate of bleeding complications.

Evaluation of the prognostic value of electrocardiography parameters and heart rhythm in patients with pulmonary hypertension.

BACKGROUND: Several studies have analyzed arrhythmias in patients with pulmonary hypertension (PH) and increased P-wave duration was identified as a risk factor for development of atrial fibrillation (AF). METHODS: We retrospectively analyzed the incidence of arrhythmias in patients with an initial diagnosis of PH during long-term follow-up and assessed the prognostic value of electrocardiography (ECG) data. Data from 167 patients were analyzed (Dana Point Classification: Group 1: 59 patients, Group 2: 28 patients, Group 3: 39 patients, Group 4: 41 patients). Clinical, 6-min-ute walk distance test, echocardiography and right heart catheterization data were collected, and baseline/follow-up ECGs were analyzed. RESULTS: Baseline ECGs revealed sinus rhythm in 137 patients. Thirteen patients had newly onset AF during follow-up. In 30 patients, baseline ECG showed AF. Patients with baseline AF showed higher atrial diameters and higher right atrial pressure. Patients with P-wave du-ration > 0.11 s had shorter survival. Other ECG parameters (PQ-interval, QRS-width, QT-/ /QTc-interval) were not associated with survival. Mean survival times were 79.4 ± 5.4 months (sinus rhythm), 64.4 ± 12.9 months (baseline AF) and 58.8 ± 8.9 months (newly onset AF during follow-up) (p = 0.565). CONCLUSIONS: Atrial fibrillation predict adverse prognosis in patients with PH and a longer P-wave (> 0.11 s) is associated with shorter survival time.

Altered CXCL12 expression reveals a dual role of CXCR4 in osteosarcoma primary tumor growth and metastasis.

PURPOSE: Better understanding of the molecular mechanisms of metastasis-the major cause of death in osteosarcoma (OS)-is a key for the development of more effective metastasis-suppressive therapy. Here, we investigated the biological relevance of the CXCL12/CXCR4 axis in OS. METHODS: We interfered with CXCL12/CXCR4 signaling in CXCR4-expressing human 143-B OS cells through stable expression of CXCL12, of its competitive antagonist P2G, or of CXCL12-KDEL, designed to retain CXCR4 within the cell. Intratibial OS xenograft mouse model metastasizing to the lung was used to assess tumorigenic and metastatic potential of the manipulated cell lines. RESULTS: Constitutive expression of native CXCL12 promoted lung metastasis without affecting tumor growth. Stable expression of P2G or CXCL12-KDEL significantly accelerated tumor growth but diminished lung metastasis. Tumors grown from P2G- or CXCL12-KDEL-expressing cells contained higher levels of CXCR4-encoding mRNA going along with a higher percentage of CXCR4-expressing tumor cells. Lung metastases of all groups were predominantly enriched with CXCR4-expressing tumor cells. CONCLUSION: Higher abundance of CXCR4 possibly contributed to increased local retention of tumor cells by bone marrow-derived CXCL12, reflected in the increased primary tumor growth and decreased number of lung metastases in P2G and CXCL12-KDEL groups. Higher percentage of CXCR4-expressing lung metastatic cells compared to the corresponding primary tumors point to important functions of the CXCL12/CXCR4 axis in late steps of metastasis. In conclusion, based on the here reported results, local treatment of lung metastases with novel CXCR4-targeting therapeutics might be considered and favored over anti-CXCR4 systemic therapy.

Extracorporeal life support in cardiovascular patients with observed refractory in-hospital cardiac arrest is associated with favourable short and long-term outcomes: A propensity-matched analysis.

AIMS: Extracorporeal life support (ECLS) has shown encouraging survival rates in patients with in-hospital cardiac arrest; however, its routine use is still controversial. We compared the survival of patients with in-hospital cardiac arrest receiving conventional cardiopulmonary resuscitation (CCPR) to that of patients with ECLS as an adjunct to cardiopulmonary resuscitation (ECPR). METHODS: A total of 353 patients with in-hospital cardiac arrest (272 CCPR and 52 ECPR) were included in this retrospective, propensity score-adjusted (1:1 matched), single-centre study. Primary endpoints were survival at 30 days, long-term survival and neurological outcome defined by the cerebral performance categories score. RESULTS: In the unmatched groups patients undergoing ECPR initially had significantly higher APACHE II scores ( P=0.03), increased norepinephrine dosages ( P=0.03) and elevated levels of creatine kinase ( P<0.0001), creatinine ( P=0.04) and lactate ( P=0.02) before cardiopulmonary resuscitation compared with those undergoing CCPR. After equalising these parameters significant differences were observed in short and long-term survival, favouring ECPR over CCPR (27% vs. 17%; P=0.01 (short-term) and 23.1% vs. 11.5%; P=0.008 (long-term); median follow-up duration after discharge 1136 days (interquartile range 823-1416)). There was no significant difference in the incidence of a cerebral performance categories score of 1 or 2 between the matched groups (CCPR 66.7% vs. ECPR 83.3%; P=0.77). ECLS implantation was the only significant and independent predictor of mortality in multivariate Cox regression analysis (hazard ratio 0.57, 95% confidence interval 0.35-0.90; P=0.02). CONCLUSION: In our cohort of cardiovascular patients ECPR was associated with better short- and long-term survival over CCPR, with a good neurological outcome in the majority of the patients with refractory in-hospital cardiac arrest.

Combined pulmonary endarterectomy and balloon pulmonary angioplasty in patients with chronic thromboembolic pulmonary hypertension.

BACKGROUND: Pulmonary endarterectomy (PEA) is a curative treatment option for more than 60% of patients with chronic thromboembolic pulmonary hypertension (CTEPH). For selected inoperable patients, interventional balloon pulmonary angioplasty (BPA) has recently been established in addition to medical treatment. This approach disrupts scar tissue occluding the pulmonary arteries, leading to an improvement in parenchymal perfusion. CTEPH is occasionally heterogeneous, with operable disease on one side but peripheral, inoperable changes on the contralateral side. Performing unilateral PEA (on the operable side only) in these patients may lead to a worse hemodynamic outcome and increased mortality compared with patients who that can be surgically corrected bilaterally. We sought to determine the feasibility, safety, and benefits of BPA applied to the contralateral lung in several patients with predominantly unilateral disease that was amenable to treatment by PEA. METHODS: Standard unilateral PEA in deep hypothermic circulatory arrest was performed in 3 CTEPH patients with poor pulmonary hemodynamics, and inoperability of the contralateral pulmonary artery obstructions was confirmed. The inoperable side was treated by BPA. The intervention was performed during the rewarming phase of cardiopulmonary bypass. RESULTS: A dramatic improvement in pulmonary hemodynamics, with a mean reduction in pulmonary vascular resistance of 842 dyne · sec/cm(5), was achieved in all patients. World Health Organization Functional Class was also significantly improved at the midterm follow-up. CONCLUSIONS: The combination of surgical PEA and interventional BPA is a new treatment option for highly selected high-risk CTEPH patients. A multidisciplinary CTEPH expert team is a basic pre-requisite for this complex concept.

Sunitinib malate (SU-11248) reduces tumour burden and lung metastasis in an intratibial human xenograft osteosarcoma mouse model.

Osteosarcoma is a rare type of cancer that commonly occurs as a primary bone tumour in children and adolescents and is associated with a poor clinical outcome. Despite complex treatment protocols, including chemotherapy combined with surgical resection, the prognosis for patients with osteosarcoma and metastases remains poor and more effective therapies are required. In this study, we evaluated the therapeutic efficacy of sunitinib malate, a wide-spectrum tyrosine kinase inhibitor, in a preclinical mouse model of osteosarcoma. Sunitinib significantly inhibited proliferation, provoked apoptosis and induced G2/M cell cycle arrest in the human osteosarcoma cell lines SaOS-2 and 143B in vitro. Importantly, sunitinib treatment significantly reduced tumour burden, microvessel density and suppressed pulmonary metastasis in a 143B cell-derived intratibial osteosarcoma model in SCID mice. Sunitinib significantly decreased primary tumor tissue proliferation and reduced tumor vasculature. Our study indicates that sunitinib has potential for effective treatment of metastasizing osteosarcoma and provides the framework for future clinical trials with sunitinib alone or in combination with conventional and other novel therapeutics aiming at increased treatment efficacy and improved patient outcome.

Clinical course and long-term outcome following venoarterial extracorporeal life support-facilitated interhospital transfer of patients with circulatory failure.

BACKGROUND: Interhospital transfer of patients experiencing circulatory failure and shock has a significant risk of cardiovascular deterioration and death. Extracorporeal life support (ECLS) is a rescue tool for hemodynamic stabilization that makes patient transportation much safer. METHODS: Demographic data, clinical course, and outcome data were reviewed for patients who underwent placement of a venoarterial ECLS in a remote hospital and were transported to our tertiary care facility. RESULTS: 68 patients were transported to our center with ECLS. The majority of these patients (79%) underwent cardiopulmonary resuscitation during or immediately prior to ECLS initiation. The mean patient age was 52 years, and 53 patients were male. The most common underlying diagnosis was acute coronary syndrome (60%). Overall, 23 patients underwent consecutive cardiosurgical procedures, including coronary artery bypass grafting in 12, and left ventricular assist device and biventricular assist device implantation in 11. The median duration of ECLS was 5 days. None of the patients died during transportation. Twelve of the surgically treated patients survived, as well as 21 patients with non-surgical treatment, which resulted in an overall survival of 33 patients (48.5%). CONCLUSION: ECLS-facilitated patient transfer enables safe interhospital transfer of critically ill patients. In this study, a relevant percentage of patients were in need of a cardiosurgical intervention. The long-term survival rate of these patients supports the further use of this time-, cost- and personnel-demanding strategy.

Prognostic value and in vitro biological relevance of Neuropilin 1 and Neuropilin 2 in osteosarcoma.

Neoadjuvant chemotherapy in osteosarcoma increased the long-term survival of patients with localized disease considerably but metastasizing osteosarcoma remained largely treatment resistant. Neuropilins, transmembrane glycoproteins, are important receptors for VEGF dependent hyper-vascularization in tumor angiogenesis and their aberrant expression promotes tumorigenesis and metastasis in many solid tumors. Our analysis of Neuropilin-1 (NRP1) and Neuropilin-2 (NRP2) immunostaining in a tissue microarray of 66 osteosarcoma patients identified NRP2 as an indicator of poor overall, metastasis-free and progression free survival while NRP1 had no predictive value. Patients with tumors that expressed NRP2 in the absence of NRP1 had a significantly worse prognosis than NRP1(-)/NRP2(-), NRP1(+) or NRP1(+)/NRP2(+) tumors. Moreover, patients with overt metastases and with NRP2-positive primary tumors had a significantly shorter survival rate than patients with metastases but NRP2-negative tumors. Furthermore, the expression of both NRP1 and NRP2 in osteosarcoma cell lines correlated to a variable degree with the metastatic potential of the respective cell line. To address the functional relevance of Neuropilins for VEGF signaling we used shRNA mediated down-regulation and blocking antibodies of NRP1 and NRP2 in the metastatic 143B and HuO9-M132 cell lines. In 143B cells, VEGFA signaling monitored by AKT phosphorylation was more inhibited by blocking of NRP1, whereas in HuO9-M132 cells NRP2 blocking was more effective indicating that NRP1 and NRP2 can substitute each other in the functional interaction with VEGFR1. Altogether, these data point to NRP2 as a powerful prognostic marker in osteosarcoma and together with NRP1 as a novel target for tumor-suppressive therapy.

CXCR4 antibody treatment suppresses metastatic spread to the lung of intratibial human osteosarcoma xenografts in mice.

Current combined surgical and neo-adjuvant chemotherapy of primary metastatic osteosarcoma (OS) is ineffective, reflected by a 5-year survival rate of affected patients of less than 20 %. Studies in experimental OS metastasis models pointed to the CXCR4/CXCL12 homing axis as a novel target for OS metastasis-suppressive treatment. The present study investigated for the first time the CXCR4-blocking principle in a spontaneously metastasizing human 143B OS cell line-derived orthotopic xenograft mouse model. The highly metastatic 143B cells, unlike the parental non-metastatic HOS cells, express functional CXCR4 receptors at the cell surface, as revealed in this study by RT/PCR of gene transcripts, by FACS analysis with the monoclonal anti CXCR4 antibody 12G5 (mAb 12G5) and by CXCL12 time- and dose-dependent stimulation of AKT and ERK phosphorylation. A significantly (p < 0.05) higher CXCL12 dose-dependent chemotactic response of 143B compared to HOS cells in a Boyden chamber trans-well migration assay suggested a crucial role of the CXCL12/CXCR4 homing axis in 143B cell lung metastasis. Repetitive treatment of mice with 143B cell-derived intratibial tumors given intravenous bolus injections of mAb12G5 indeed inhibited significantly (p < 0.01) the number of X-gal-stainable lung micrometastases of lacZ-transduced 143B cells. Antibody treatment had also a mild inhibitory effect on primary tumor growth associated with remarkably less osteolysis, but it did not affect the number of developing lung macrometastases. In conclusion, these results demonstrate considerable potential of high-affinity CXCR4-blocking agents for OS tumor cell homing suppressive treatment in metastasizing OS complementary to current (neo)-adjuvant chemotherapy.

Reduced Latency in the Metastatic Niche Contributes to the More Aggressive Phenotype of LM8 Compared to Dunn Osteosarcoma Cells.

Metastasis is the major cause of death of osteosarcoma patients and its diagnosis remains difficult. In preclinical studies, however, forced expression of reporter genes in osteosarcoma cells has remarkably improved the detection of micrometastases and, consequently, the quality of the studies. We recently showed that Dunn cells equipped with a lacZ reporter gene disseminated from subcutaneous primary tumors as frequently as their highly metastatic subline LM8, but only LM8 cells grew to macrometastases. In the present time-course study, tail-vein-injected Dunn and LM8 cells settled within 24 h at the same frequency in the lung, liver, and kidney of mice. Furthermore, Dunn cells also grew to macrometastases, but, compared to LM8, with a delay of two weeks in lung and one week in liver and kidney tissue, consistent with prolonged survival of the mice. Dunn- and LM8-cell-derived ovary and spine metastases occurred less frequently. In vitro, Dunn cells showed less invasiveness and stronger contact inhibition and intercellular adhesion than LM8 cells and several cancer- and dormancy-related genes were differentially expressed. In conclusion, Dunn cells, compared to LM8, have a similar capability but a longer latency to form macrometastases and provide an interesting new experimental system to study tumor cell dormancy.

Expression of the chemokine receptor CXCR7 in CXCR4-expressing human 143B osteosarcoma cells enhances lung metastasis of intratibial xenografts in SCID mice.

More effective treatment of metastasizing osteosarcoma with a current mean 5-year survival rate of less than 20% requires more detailed knowledge on mechanisms and key regulatory molecules of the complex metastatic process. CXCR4, the receptor of the chemokine CXCL12, has been reported to promote tumor progression and metastasis in osteosarcoma. CXCR7 is a recently deorphanized CXCL12-scavenging receptor with so far not well-defined functions in tumor biology. The present study focused on a potential malignancy enhancing function of CXCR7 in interaction with CXCR4 in osteosarcoma, which was investigated in an intratibial osteosarcoma model in SCID mice, making use of the human 143B osteosarcoma cell line that spontaneously metastasizes to the lung and expresses endogenous CXCR4. 143B osteosarcoma cells stably expressing LacZ (143B-LacZ cells) were retrovirally transduced with a gene encoding HA-tagged CXCR7 (143B-LacZ-X7-HA cells). 143B-LacZ-X7-HA cells co-expressing CXCR7 and CXCR4 exhibited CXCL12 scavenging and enhanced adhesion to IL-1ß-activated HUVEC cells compared to 143B-LacZ cells expressing CXCR4 alone. SCID mice intratibially injected with 143B-LacZ-X7-HA cells had significantly (p<0.05) smaller primary tumors, but significantly (p<0.05) higher numbers of lung metastases than mice injected with 143B-LacZ cells. Unexpectedly, 143B-LacZ-X7-HA cells, unlike 143B-LacZ cells, also metastasized with high incidence to the auriculum cordis. In conclusion, expression of the CXCL12 scavenging receptor CXCR7 in the CXCR4-expressing human 143B osteosarcoma cell line enhances its metastatic activity in intratibial primary tumors in SCID mice that predominantly metastasize to the lung and thereby closely mimic the human disease. These findings point to CXCR7 as a target, complementary to previously proposed CXCR4, for more effective metastasis-suppressive treatment in osteosarcoma.