Elvira Stacher

Modern age pathology of pulmonary arterial hypertension.

RATIONALE The impact of modern treatments of pulmonary arterial hypertension (PAH) on pulmonary vascular pathology remains unknown. OBJECTIVES To assess the spectrum of pulmonary vascular remodeling in the modern era of PAH medication. METHODS Assessment of pulmonary vascular remodeling and inflammation in 62 PAH and 28 control explanted lungs systematically sampled. MEASUREMENTS AND MAIN RESULTS Intima and intima plus media fractional thicknesses of pulmonary arteries were increased in the PAH group versus the control lungs and correlated with pulmonary hemodynamic measurements. Despite a high variability of morphological measurements within a given PAH lung and among all PAH lungs, distinct pathological subphenotypes were detected in cohorts of PAH lungs. These included a subset of lungs lacking intima or, most prominently, media remodeling, which had similar numbers of profiles of plexiform lesions as those in lungs with more pronounced remodeling. Marked perivascular inflammation was present in a high number of PAH lungs and correlated with intima plus media remodeling. The number of profiles of plexiform lesions was significantly lower in lungs of male patients and those never treated with prostacyclin or its analogs. CONCLUSIONS Our results indicate that multiple features of pulmonary vascular remodeling are present in patients treated with modern PAH therapies. Perivascular inflammation may have an important role in the processes of vascular remodeling, all of which may ultimately lead to increased pulmonary artery pressure. Moreover, our study provides a framework to interpret and design translational studies in PAH.

Endothelin-1 Inhibits Background Two-Pore Domain Channel TASK-1 in Primary Human Pulmonary Artery Smooth Muscle Cells

Endothelin (ET)-1 causes long-lasting vasoconstriction and vascular remodeling by interacting with specific G-protein-coupled receptors in pulmonary artery smooth muscle cells (PASMCs), and thus plays an important role in the pathophysiology of pulmonary arterial hypertension. The two-pore domain K(+) channel, TASK-1, controls the resting membrane potential in human PASMCs (hPASMCs), and renders these cells sensitive to a variety of vasoactive factors, as previously shown. ET-1 may exert its vasoconstrictive effects in part by targeting TASK-1. To clarify this, we analyzed the ET-1 signaling pathway related to TASK-1 in primary hPASMCs. We employed the whole-cell patch-clamp technique combined with TASK-1 small interfering RNA (siRNA) in hPASMC and the isolated, perfused, and ventilated mouse lung model. We found that ET-1 depolarized primary hPASMCs by phosphorylating TASK-1 at clinically relevant concentrations. The ET sensitivity of TASK-1 required ET(A) receptors, phospholipase C, phosphatidylinositol 4,5-biphosphate, diacylglycerol, and protein kinase C in primary hPASMCs. The ET-1 effect on membrane potential and TASK-1 was abrogated using TASK-1 siRNA. This is the first time that the background K(+) channel, TASK-1, has been identified in the ET-1-mediated depolarization in native hPASMC, and might represent a novel pathologic mechanism related to pulmonary arterial hypertension.

Src tyrosine kinase is crucial for potassium channel function in human pulmonary arteries

The potassium channel TWIK-related acid sensitive potassium (TASK)-1 channel, together with other potassium channels, controls the low resting tone of pulmonary arteries. The Src family tyrosine kinase (SrcTK) may control potassium channel function in human pulmonary artery smooth muscle cells (hPASMCs) in response to changes in oxygen tension and the clinical use of a SrcTK inhibitor has resulted in partly reversible pulmonary hypertension. This study aimed to determine the role of SrcTK in hypoxia-induced inhibition of potassium channels in hPASMCs. We show that SrcTK is co-localised with the TASK-1 channel. Inhibition of SrcTK decreases potassium current density and results in considerable depolarisation, while activation of SrcTK increases potassium current in patch-clamp recordings. Moderate hypoxia and the SrcTK inhibitor decrease the tyrosine phosphorylation state of the TASK-1 channel. Hypoxia also decreases the level of phospho-SrcTK (tyr419) and reduces the co-localisation of the TASK-1 channel and phospho-SrcTK. Corresponding to this, hypoxia reduces TASK-1 currents before but not after SrcTK inhibition and, in the isolated perfused mouse lung, SrcTK inhibitors increase pulmonary arterial pressure. We propose that the SrcTK is a crucial factor controlling potassium channels, acting as a cofactor for setting a negative resting membrane potential in hPASMCs and a low resting pulmonary vascular tone.

PCK2 activation mediates an adaptive response to glucose depletion in lung cancer

Cancer cells are reprogrammed to utilize glycolysis at high rates, which provides metabolic precursors for cell growth. Consequently, glucose levels may decrease substantially in underperfused tumor areas. Gluconeogenesis results in the generation of glucose from smaller carbon substrates such as lactate and amino acids. The key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), has been shown to provide metabolites for cell growth. Still, the role of gluconeogenesis in cancer is unknown. Here we show that the mitochondrial isoform of PEPCK (PCK2) is expressed and active in three lung cancer cell lines and in non-small cell lung cancer samples. PCK2 expression and activity were enhanced under low-glucose conditions. PEPCK activity was elevated threefold in lung cancer samples over normal lungs. To track the conversion of metabolites along the gluconeogenesis pathway, lung cancer cell lines were incubated with 13C3-lactate and label enrichment in the phosphoenolpyruvate (PEP) pool was measured. Under low glucose, all three carbons from 13C3-lactate appeared in the PEP pool, further supporting a conversion of lactate to pyruvate, via pyruvate carboxylase to oxaloacetate, and via PCK2 to phosphoenolpyruvate. PCK2 small interfering RNA and the pharmacological PEPCK inhibitor 3-mercaptopicolinate significantly enhanced glucose depletion-induced apoptosis in A549 and H23 cells, but not in H1299 cells. The growth of H23 multicellular spheroids was significantly reduced by 3-mercaptopicolinate. The results of this study suggest that lung cancer cells may utilize at least some steps of gluconeogenesis to overcome the detrimental metabolic situation during glucose deprivation and that in human lung cancers this pathway is activated in vivo.

Comparison of formalin-free tissue fixatives: a proteomic study testing their application for routine pathology and research.

CONTEXT Formalin-fixed, paraffin-embedded tissue is the routine processing method for diagnostics practiced in pathology departments worldwide. OBJECTIVE To determine the potential value of non-cross-linking, formalin-free tissue fixation for diagnostics in pathology and proteomic investigations. DESIGN We tested 3 commercially available, formalin-free tissue fixatives-FineFIX, RCL2, and HOPE-in lung cancer specimens from 10 patients. The fixatives were evaluated for their effects on tissue morphology, protein recovery, and immunoreactivity for a selected panel of proteins differently expressed in lung cancer, using immunohistochemistry and Western blotting. RESULTS Tumor-cell analysis with hematoxylin-eosin worked equally well for all tested fixatives when compared with the standard formalin-fixed, paraffin-embedded procedure. Movat pentachrome stains showed comparable results for the different matrices and cellular proteins analyzed. The RCL2 (P = .01) and HOPE fixatives (P = .03) improved protein recovery when compared with formalin-fixed, paraffin-embedded or frozen tissues. Our data clearly show that the fixatives evaluated influenced immunoreactivity to matched, formalin-fixed, paraffin-embedded lung cancer tissue. In particular, membrane-bound proteins, such as epidermal growth factor receptor EGFR, can be detected more efficiently by immunohistochemistry and Western blotting. CONCLUSION We have demonstrated that formalin-free fixatives have the potential in routine pathology and research to replace formalin in histomorphology and protein preservation.

The VEGF-system in primary pulmonary angiosarcomas and haemangioendotheliomas: New potential therapeutic targets?

Malignant epitheloid vascular tumors (epitheloid haemangioendotheliomas and angiosarcomas) of the lung are very rare lesions often posing difficulties in diagnosis. Due to their rare incidence no standardized therapy regimen is established. Surgical resection of the tumor is the mainstay of treatment, but in many cases, especially due to the multifocality of the tumor, negative resection margins cannot be achieved. A blockade of members of the vascular endothelial growth factor (VEGF) system either by antibodies for their ligands or by kinase inhibitors has been increasingly used for the therapy of solid tumors. The aim of our study was to highlight the main distinguishing morphological factors between the two entities for diagnostic purposes. Next, we investigated several factors of the VEGF-signalling pathway as well as Tie 2 in eight primary pulmonary epitheloid haemangioendotheliomas and ten primary pulmonary epitheloid angiosarcomas by means of immunohistochemistry using commercially available antibodies against VEGF-A, VEGF-B, VEGF-C, VEGF-D, VEGFR-2, VEGFR-3 and endothelium specific kinase Tie2. The observed positivity for the factors of the VEGF-signalling pathway points towards a possible new therapeutic option in the therapy of pulmonary vascular tumors by a blockade of the ligands or their receptors.

Angiostatic Factors in the Pulmonary Endarterectomy Material from Chronic Thromboembolic Pulmonary Hypertension Patients Cause Endothelial Dysfunction

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare disease with persistent thrombotic occlusion or stenosis of the large pulmonary arteries resulting in pulmonary hypertension. Surgical removal of the neointimal layer of these vessels together with the non-resolved thrombus consisting of organized collagen-rich fibrotic areas with partly recanalized regions is the treatment of choice (pulmonary endarterectomy, PEA). The present study investigates endothelial cells isolated from such material as well as factors present in the surgical PEA material, which may contribute to impairment of recanalization and thrombus non-resolution. We observed muscularized vessels and non-muscularized vessels in the PEA material. The isolated endothelial cells from the PEA material showed significantly different calcium homeostasis as compared to pulmonary artery endothelial cells (hPAECs) from normal controls. In the supernatant (ELISA) as well as on the tissue level (histochemical staining) of the PEA material, platelet factor 4 (PF4), collagen type I and interferon-gamma-inducible 10 kD protein (IP-10) were detected. CXCR3, the receptor for PF4 and IP-10, was particularly elevated in the distal parts of the PEA material as compared to human control lung (RT-PCR). PF4, collagen type I and IP-10 caused significant changes in calcium homeostasis and affected the cell proliferation, migration and vessel formation in hPAECs. The presence of angiostatic factors like PF4, collagen type I and IP-10, as recovered from the surgical PEA material from CTEPH patients, may lead to changes in calcium homeostasis and endothelial dysfunction.

Nuclear and cytoplasmic death receptor 5 as prognostic factors in patients with non-small cell lung cancer treated with chemotherapy.

BACKGROUND Death receptor 4 (DR4) and death receptor 5 (DR5) are tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL) receptors that activate apoptosis via the extrinsic apoptosis pathway. DcR1 and DcR2 are decoy receptors for TRAIL that act antagonistically. Intracellular trafficking of TRAIL receptors has been described, but the role of the subcellular localization of TRAIL receptors in non-small cell lung cancer (NSCLC) progression is unclear. METHODS Expression and intracellular localization of pro-apoptotic and decoy TRAIL receptors were analyzed by immunohistochemistry in 50 samples of advanced or recurrent NSCLC. Using confocal microscopy, localization of TRAIL receptors was studied in NSCLC cell lines. RESULTS Cytoplasmic staining for all four TRAIL receptors was observed in the majority of samples. Nuclear staining was infrequent in the case of DR4 (12%) and DcR2 (8%), while DR5 and DcR1 were localized in the nucleus in 27% and 60% of samples. When overall survival was analyzed, cytoplasmic staining for DR5 in tumor cells (P=0.025) and nuclear staining for DR5 in tumor cells (P=0.007) were significant prognostic factors in univariate, as well as in multivariate analysis including clinicopathologic factors (P=0.026 and 0.021, respectively). In A549, NCI-H358, and A427 NSCLC cells all four TRAIL receptors were found to be mainly located perinuclearly, but also in the nucleus. CONCLUSION The study for the first time shows that TRAIL receptors are found in different intracellular compartments including the nucleus in NSCLC cells and that both nuclear and cytoplasmic DR5 might predict improved survival in patients with advanced NSCLC.

Androgen receptor expression in breast cancer patients tested for BRCA1 and BRCA2 mutations.

Pristauz G, Petru E, Stacher E, Geigl J B, Schwarzbraun T, Tsybrovskyy O, Winter R & Moinfar F
(2010) Histopathology57, 877–884

Compartment-specific expression of collagens and their processing enzymes in intrapulmonary arteries of IPAH patients

Alterations in extracellular matrix (ECM) have been implicated in the pathophysiology of pulmonary hypertension. Here, we have undertaken a compartment-specific study to elucidate the expression profile of collagens and their processing enzymes in donor and idiopathic pulmonary arterial hypertension (IPAH) pulmonary arteries. Predominant intimal, but also medial and perivascular, remodeling and reduced lumen diameter were detected in IPAH pulmonary arteries. Two-photon microscopy demonstrated accumulation of collagen fibers. Quantification of collagen in pulmonary arteries revealed collagen accumulation mainly in the intima of IPAH pulmonary arteries compared with donors. Laser capture-microdissected pulmonary artery profiles (intima+media and perivascular tissue) were analyzed by real-time PCR for ECM gene expression. In the intima+media of IPAH vessels, collagens (COL4A5, COL14A1, and COL18A1), matrix metalloproteinase (MMP) 19, and a disintegrin and metalloprotease (ADAM) 33 were higher expressed, whereas MMP10, ADAM17, TIMP1, and TIMP3 were less abundant. Localization of COLXVIII, its cleavage product endostatin, and MMP10, ADAM33, and TIMP1 was confirmed in pulmonary arteries by immunohistochemistry. ELISA for collagen XVIII/endostatin demonstrated significantly elevated plasma levels in IPAH patients compared with donors, whereas circulating MMP10, ADAM33, and TIMP1 levels were similar between the two groups. Endostatin levels were correlated with pulmonary arterial wedge pressure, and established prognostic markers of IPAH, right atrial pressure, cardiac index, 6-min walking distance, NH2-terminal pro-brain natriuretic peptide, and uric acid. Expression of unstudied collagens, MMPs, ADAMs, and TIMPs were found to be significantly altered in IPAH intima+media. Elevated levels of circulating collagen XVIII/endostatin are associated with markers of a poor prognosis.