Keratinocyte Sonic Hedgehog Upregulation Drives the Development of Giant Congenital Nevi via Paracrine Endothelin-1 Secretion.

Giant congenital nevi are associated with clinical complications such as neurocutaneous melanosis and melanoma. Virtually nothing is known about why some individuals develop these lesions. We previously identified the sonic hedgehog (Shh) pathway regulator Cdon as a candidate nevus modifier gene. Here we validate this by studying Cdon knockout mice, and go on to establishing the mechanism by which Shh exacerbates nevogenesis. Cdon knockout mice develop blue nevi without the need for somatic melanocyte oncogenic mutation. In a mouse model carrying melanocyte NRASQ61K, we found that strain backgrounds that carry genetic variants that cause increased keratinocyte Shh pathway activity, as measured by Gli1 and Gli2 expression, develop giant congenital nevi. Shh components are also active adjacent to human congenital nevi. Mechanistically, this exacerbation of nevogenesis is driven via the release of the melanocyte mitogen endothelin-1 from keratinocytes. We then suppressed nevus development in mice using Shh and endothelin antagonists. Our work suggests an aspect of nevus development whereby keratinocyte cytokines such as endothelin-1 can exacerbate nevogenesis, and provides potential therapeutic approaches for giant congenital nevi. Furthermore, it highlights the notion that germline genetic variation, in addition to somatic melanocyte mutation, can strongly influence the histopathological features of melanocytic nevi.

Pulmonary hypertensive vasculopathy in parenchymal lung diseases and/or hypoxia: Number 1 in the Series "Pathology for the clinician" Edited by Peter Dorfmüller and Alberto Cavazza.

Pulmonary hypertension (PH) with complicating chronic lung diseases and/or hypoxia falls into group 3 of the updated classification of PH. Patients with chronic obstructive lung disease (COPD), diffuse lung disease (such as idiopathic pulmonary fibrosis (IPF)) and with sleep disordered breathing are particularly exposed to the risk of developing PH. Although PH in such a context is usually mild, a minority of patients exhibit severe haemodynamic impairment, defined by a mean pulmonary arterial pressure (mPAP) of ≥35 mmHg or mPAP values ranging between 25 mmHg and 35 mmHg with a low cardiac index (<2 L·min-1·m-2). The overlap between lung parenchymal disease and PH heavily affects life expectancy in such a patient population and complicates their therapeutic management. In this review we illustrate the pathological features and the underlying pathophysiological mechanisms of pulmonary circulation in chronic lung diseases, with an emphasis on COPD, IPF and obstructive sleep apnoea syndrome.

Increasing time trends of thin melanomas in The Netherlands: What are the explanations of recent accelerations?

BACKGROUND: A disproportional increase in in situ or thin melanomas may point at underlying causes such as increased melanoma awareness, as well as 'overdiagnosis' of melanoma in diagnostically equivocal small lesions. OBJECTIVES: The purposes of this study were to estimate trends in melanoma incidence by sex, Breslow thickness (thin melanomas subdivided into four subgroups: <0.25 mm, 0.25-0.49 mm, 0.50-0.74 mm, and 0.75-1.0 mm), age and location, and to compare these with trends in subgroups of thicker melanomas. METHODS: Data on all histologically confirmed in situ and invasive melanomas diagnosed between 1994 and 2010 were retrieved from the Netherlands Cancer Registry. Trends in European standardised rates (ESRs) were assessed using joinpoint analysis, and expressed as estimated annual percentage change (EAPC). RESULTS: Between 1994 and 2010, 34,156 persons were diagnosed with an in situ or thin melanoma. The ESR of in situ melanomas doubled for males and females with a recent steeper rise in incidence (EAPC 12% (95% confidence interval [CI]: 8.1-16) and 13% (95% CI: 5.9-20), respectively). ESR for thin melanomas amongst males approximately doubled with a steep, but non-significant acceleration compared to other thickness categories since 2006 for <0.25 mm melanomas (EAPC 26% (95% CI: 2.1-35)). For female patients with thin melanomas the ESRs increased almost two-fold, except for <0.25 mm melanomas. CONCLUSIONS: The incidence rates of in situ, thin and thick melanomas increased similarly between 1994 and 2010. Recently steep increases were found for in situ melanomas and thin melanomas in men. Explanations are 'overdiagnosis' in conjunction with increased ultraviolet exposure (natural and artificial) and therefore a 'true' increase, increased awareness, early detection, diagnostic drift and changed market forces in the Dutch health care system.

"Lentiginous melanoma": full-fledged melanoma or melanoma precursor?

On the basis of a critical review of published literature, it is concluded that there is as yet insufficient evidence to conclude that the melanocytic lesion, which is currently known as "lentiginous melanoma," is a full-fledged melanoma, with the capacity to metastasize to distant sites and to cause the demise of the patient. It is proposed that this lesion is better designated as "lentiginous SAMPUS," that is, a superficial atypical melanocytic proliferation of uncertain significance, with a lentiginous, or predominantly lentiginous, arrangement of the junctional component. As there is uncertainty regarding its actual metastatic potential or the likelihood of progression to melanoma NOS, the lesion should be removed completely, with free surgical margins.

Nitric oxide donors augment interleukin-1ß-induced vascular endothelial growth factor in airway smooth muscle cells.

Angiogenesis and microvascular leakage are features of chronic inflammatory diseases of which molecular mechanisms are poorly understood. We investigated the effects of interleukin-1ß (IL-1ß) on the expression and secretion of vascular endothelial growth factor (VEGF) and placenta growth factor (PlGF) in porcine airway smooth muscle cells (PASMC) in relation to a nitric oxide (NO) pathway. Serum-deprived (48 h) PASMC were stimulated with IL-1ß alone or with NO donor, L-arginine and/or NO synthase inhibitor L-NAME for 4 and 24 h. IL-1ß did not affect PlGF release, but augmented VEGF release (2.4-fold) after 24 h. VEGF release was inhibited by L-NAME (531.8 ± 52 pg/ml), but restored and further elevated by L-arginine (1,529 ± 287 pg/ml). IL-1ß up-regulated VEGF mRNA (1.8-fold) and this response was attenuated by L-NAME (1.1-fold) and augmented by L-arginine (3.8-fold) at 4 h. Restoration of a NO pathway by L-arginine in L-NAME-treated cells resulted in elevated VEGF mRNA levels (2.2-fold). [(3)H]Thymidine incorporation assay revealed enhanced porcine pulmonary artery endothelial cell proliferation in response to IL-1ß, VEGF and PlGF, and this mitogenic effect was not influenced via the NO pathway. Our results suggest that a NO pathway modulates VEGF synthesis during inflammation contributing to bronchial angiogenesis and vascular leakage.

Angiogenesis and vascular remodeling in chronic airway diseases.

Asthma and chronic obstructive pulmonary disease remain a global health problem, with increasing morbidity and mortality. Despite differences in the causal agents, both diseases exhibit various degrees of inflammatory changes, structural alterations of the airways leading to airflow limitation. The existence of transient disease phenotypes which overlap both diseases and which progressively decline the lung function has complicated the search for an effective therapy. Important characteristics of chronic airway diseases include airway and vascular remodeling, of which the molecular mechanisms are complex and poorly understood. Recently, we and others have shown that airway smooth muscle (ASM) cells are not only structural and contractile components of airways, rather they bear capabilities of producing large number of pro-inflammatory and mitogenic factors. Increase in size and number of blood vessels both inside and outside the smooth muscle layer as well as hyperemia of bronchial vasculature are contributing factors in airway wall remodeling in patients with chronic airway diseases, proposing for the ongoing mechanisms like angiogenesis and vascular dilatation. We believe that vascular changes directly add to the airway narrowing and hyper-responsiveness by exudation and transudation of proinflammatory mediators, cytokines and growth factors; facilitating trafficking of inflammatory cells; causing oedema of the airway wall and promoting ASM accumulation. One of the key regulators of angiogenesis, vascular endothelial growth factor in concerted action with other endothelial mitogens play pivotal role in regulating bronchial angiogenesis. In this review article we address recent advances in pulmonary angiogenesis and remodelling that contribute in the pathogenesis of chronic airway diseases.

DNA microarray and quantitative analysis reveal enhanced myocardial VEGF expression with stunted angiogenesis in human tetralogy of Fallot.

Tetralogy of Fallot (ToF) is a cyanotic congenital heart disease with prominent right ventricular hypertrophy (RVH) associated with impaired myocardial oxygen and nutrient supply. Consequently, the right ventricle may manifest in altered molecular phenotype with a number of adaptive and inherited gene profiles which are largely unknown. The aim of the present study was to investigate the myocardial differential gene expression profile and to assess myocardial vascularisation in patients with ToF. DNA microarray analysis on right ventricular biopsies from ToF-patients operated for primary corrective surgery (referred as ToF-1; n = 12, mean age 0.5 year) and age matched controls (n = 6) was validated by Northern hybridisation and RT-PCR. Employing immunohistochemistry and video image analysis expression of vascular endothelial growth factor (VEGF), vascular density (by α-SMA and CD31 staining) and myocyte cross sectional area (Gomori's reticuline staining) were assessed in ToF-1 and adult patients (referred as ToF-2, n = 12, mean age 30 years) who underwent surgery for pulmonary regurgitation and compared the data with respective age matched controls (n = 6/12). DNA microarray analysis revealed altered expression pattern for 236 genes including enhanced (1.5-2.2-fold) expression of angiogenic factors and their receptors including; VEGF, flt-1, flk-1 angiopoietin-2, FGF-2, FGF-R1, PDGF-A, whereas, flt-4, Tie, TGF-ß, TGF-ß3R showed decreased (1.6-3.4-fold) expression in ToF-patients. Northern blot analysis verified the expression patterns of VEGF and flk-1 in both ToF-1 and ToF-2 patients. VEGF staining in cardiomyocytes was increased in ToF-1 (1.5-fold, p < 0.05) as compared to ToF-2. Video image analysis revealed enhanced vascular density (p < 0.01) with enlarged myocyte cross sectional area (p < 0.01), but vascular wall thickness remained unchanged in ToF-1 patients as compared to age matched controls. Our data suggest that RVH is associated with profound changes in gene profile for a number of genes, where VEGF/VEGF-R system contributes to enhance, but stunted myocardial angiogenesis in patients with ToF.

Surveillance of second-degree relatives from melanoma families with a CDKN2A germline mutation.

BACKGROUND: Lifetime melanoma risk of mutation carriers from families with a germline mutation in the CDKN2A gene is estimated to be 67%. The necessity to include family members in a melanoma surveillance program is widely endorsed, but there is no consensus on which family members should be invited. METHODS: In a retrospective follow-up study, we investigated the yield of surveillance of first- and second-degree relatives of melanoma and pancreatic cancer patients from 21 families with the "p16-Leiden" CDKN2A mutation. Melanoma incidence rates were compared with the general population. RESULTS: Three-hundred and fifty-four first-degree relatives and 391 second-degree relatives were included. Forty-five first-degree relatives and 11 second-degree relatives were diagnosed with melanoma. Most (72%) of second-degree relatives diagnosed with melanoma had become a first-degree relative before diagnosis, due to the occurrence of a melanoma in a parent or sibling. Overall, melanoma incidence rate was 2.1 per 1,000 person years [95% confidence interval (CI), 1.2-3.8] in family members still being second-degree relatives at diagnosis, compared with 9.9 per 1,000 person years (95% CI, 7.4-13.3) in first-degree relatives. The standardized morbidity ratio for melanoma of second-degree relatives compared with the general population was 12.9 (95% CI, 7.2-23.4). CONCLUSION: Second-degree relatives from families with the p16-Leiden mutation in CDKN2A have a considerably increased melanoma risk compared with the general population. IMPACT: This study provides justification for the surveillance of second-degree relatives from families with a CDKN2A germline mutation.

[Revision of the national guideline 'Melanoma']. / Revisie van de landelijke richtlijn 'Melanoom'.

Melanoma is in the top ten of the most common types of cancer in the Netherlands. Incidence is increasing steadily by about 4% every year. The relative 5-year survival rate for patients with a melanoma with Breslow thickness < 1mm is about 98%. The national guideline 'Melanoma version 2.0' is the result of an evidence based revision focussed on the most important bottlenecks encountered in clinical practice. The most important changes concern indications for sentinel node procedures (in patients with tumours stage 1b and higher) and multidisciplinary consultation (patients with stage 3 and 4 tumours). The guideline is intended for all professionals involved in diagnosis, treatment and support of patients with melanoma of the skin.- Guideline summary cards and the 'Melanoma Pathway' ('Zorgpad Melanoom') are available at www.iknl.nl.- An English translation of the quideline will be available in April 2013 at www.oncoline.nl.

Azithromycin attenuates fibroblast growth factors induced vascular endothelial growth factor via p38(MAPK) signaling in human airway smooth muscle cells.

The airways in asthma and COPD are characterized by an increase in airway smooth muscle (ASM) mass and bronchial vascular changes associated with increased expression of pro-angiogenic growth factors, such as fibroblast growth factors (FGF-1 and FGF-2) and vascular endothelial growth factor (VEGF). We investigated the contribution of FGF-1/-2 in VEGF production in ASM cells and assessed the influence of azithromycin and dexamethasone and their underlying signaling mechanisms. Growth-synchronized human ASM cells were pre-treated with MAPK inhibitors, U0126 for ERK1/2(MAPK) and SB239063 for p38(MAPK) as well as with dexamethasone or azithromycin, 30 min before incubation with FGF-1 or FGF-2. Expression of VEGF (VEGF-A, VEGF121, and VEGF165) was assessed by quantitative PCR, VEGF release by ELISA and MAPK phosphorylation by Western blotting. Both FGF-1 and FGF-2 significantly induced mRNA levels of VEGF-A, VEGF121, and VEGF165. The VEGF protein release was increased 1.8-fold (FGF-1) and 5.5-fold (FGF-2) as compared to controls. Rapid transient increase in ERK1/2(MAPK) and p38(MAPK) phosphorylation and subsequent release of VEGF from FGF-1 or FGF-2-treated ASM cells were inhibited by respective blockers. Furthermore, azithromycin and dexamethasone significantly reduced both the VEGF release and the activation of p38(MAPK) pathway in response to FGF-1 or FGF-2 treatment. Our Results demonstrate that FGF-1 and FGF-2 up-regulate VEGF production via ERK1/2(MAPK) and p38(MAPK) pathways. Both azithromycin and dexamethasone elicited their anti-angiogenic effects via p38(MAPK) pathway in vitro, thereby suggesting a possible therapeutic approach to tackle VEGF-mediated vascular remodeling.

Targeting BRAFV600E in an inducible murine model of melanoma.

The MAP kinase and PI3 kinase pathways have been identified as the most common pathways that mediate oncogenic transformation in melanoma, and the majority of compounds developed for melanoma treatment target one or the other of these pathways. In addition to such targeted therapies, immunotherapeutic approaches have shown promising results. A combination of these two treatment modalities could potentially result in further improvement of treatment outcome. To preclinically identify efficient treatment combinations and to optimize therapy protocols in terms of sequence and timing, mouse models will be required. We have crossed and characterized the Tyr::CreER(T2);PTEN(F-/-);BRAF(F-V600E/+) inducible melanoma model on a C57BL/6J background. Tumors from this model harbor the BRAF(V600E) mutation and are PTEN-deficient, making them highly suitable for the testing of targeted therapies. Furthermore, we crossed the model onto this specific background for use in immunotherapy studies, because most experiments in this field have been performed in C57BL/6J mice. Selective inhibition of BRAF(V600E) by PLX4720 treatment of melanoma-bearing mice resulted in a strong decrease of tumor outgrowth. Furthermore, the inducible melanomas had immune cell infiltrates similar to those found in human melanoma, and tumor-infiltrating lymphocytes could be cultured from these tumors. Our data indicate that the C57BL/6J Tyr::CreER(T2);PTEN(F-/-);BRAF(F-V600E/+) melanoma model could be used as a standard model in which targeted and immunotherapy combinations can be tested in a high-throughput manner.

Abrogation of BRAFV600E-induced senescence by PI3K pathway activation contributes to melanomagenesis.

Human melanocytic nevi (moles) are benign lesions harboring activated oncogenes, including BRAF. Although this oncogene initially acts mitogenically, eventually, oncogene-induced senescence (OIS) ensues. Nevi can infrequently progress to melanomas, but the mechanistic relationship with OIS is unclear. We show here that PTEN depletion abrogates BRAF(V600E)-induced senescence in human fibroblasts and melanocytes. Correspondingly, in established murine BRAF(V600E)-driven nevi, acute shRNA-mediated depletion of PTEN prompted tumor progression. Furthermore, genetic analysis of laser-guided microdissected human contiguous nevus-melanoma specimens recurrently revealed identical mutations in BRAF or NRAS in adjacent benign and malignant melanocytes. The PI3K pathway was often activated through either decreased PTEN or increased AKT3 expression in melanomas relative to their adjacent nevi. Pharmacologic PI3K inhibition in melanoma cells suppressed proliferation and induced the senescence-associated tumor suppressor p15(INK4B). This treatment also eliminated subpopulations resistant to targeted BRAF(V600E) inhibition. Our findings suggest that a significant proportion of melanomas arise from nevi. Furthermore, these results demonstrate that PI3K pathway activation serves as a rate-limiting event in this setting, acting at least in part by abrogating OIS. The reactivation of senescence features and elimination of cells refractory to BRAF(V600E) inhibition by PI3K inhibition warrants further investigation into the therapeutic potential of simultaneously targeting these pathways in melanoma.

CHEK2*1100delC homozygosity is associated with a high breast cancer risk in women.

BACKGROUND: Mutations in the CHEK2 gene confer a moderately increased breast cancer risk. The risk for female carriers of the CHEK2*1100delC mutation is twofold increased. Breast cancer risk for carrier women is higher in a familial breast cancer setting which is due to coinheritance of additional genetic risk factors. This study investigated the occurrence of homozygosity for the CHEK2*1100delC allele among familial breast cancer cases and the associated breast cancer risk. METHODS AND RESULTS: Homozygosity for the CHEK2*1100delC allele was identified in 8/2554 Dutch independent familial non-BRCA1/2 breast cancer cases. The genotype relative risk for breast cancer of homozygous and heterozygous familial breast cancer cases was 101.34 (95% CI 4.47 to 121 000) and 4.04 (95% CI 0.88 to 21.0), respectively. Female homozygotes appeared to have a greater than twofold increased breast cancer risk compared to familial CHEK2*1100delC heterozygotes (p=0.044). These results and the occurrence of multiple primary tumours in 7/10 homozygotes indicate a high cancer risk in homozygous women from non-BRCA1/2 families. CONCLUSIONS: Intensive breast surveillance is therefore justified in these homozygous women. It is concluded that diagnostic testing for biallelic mutations in CHEK2 is indicated in non-BRCA1/2 breast cancer families, especially in populations with a relatively high prevalence of deleterious mutations in CHEK2.

Transforming growth factor-beta 1 induces angiogenesis in vitro via VEGF production in human airway smooth muscle cells.

Increase in size and number of bronchial blood vessels as well as hyperaemia are factors that contribute to airway wall remodelling in patients with chronic airway diseases, such as asthma and chronic obstructive pulmonary diseases (COPD). Expression of transforming growth factor beta 1 (TGF-beta 1), a multifunctional cytokine as well as vascular endothelial growth factor (VEGF), a key angiogenic molecule, has been shown in the inflammed airways in patients with chronic airway diseases. TGF-beta 1 has been implicated in the regulation of extracellular matrix, leading to airway remodelling in patients with chronic airway diseases. However, the role of TGF-beta 1 in regulating VEGF expression in patients with chronic airway diseases, as well as the underlying mechanisms are not yet well established. We investigated whether TGF-beta 1 stimulates VEGF expression in vitro and hence could influence vascular remodelling. Cultured human airway smooth muscle cells (HASMC) were serum deprived for 60 h before incubation with 5ng/ml of TGF-beta 1 for different time points. Control cells received serum-free culture medium. TGF-beta 1 treatment resulted in time dependent HASMC cell proliferation with maximal values for DNA biosynthesis at 24 h and cell number at 48 h. Northern blot analysis of VEGF mRNA expression showed increased levels in cells treated with TGF-beta 1 for 4 to 8 h. TGF-beta 1 also induced a time-dependent release of VEGF proteins in the conditioned medium after 48 h of treatment. Furthermore, the ability of HASMC-released VEGF proteins to induce human umbilical vein endothelial cells proliferation was inhibited by VEGF receptor antagonist, confirming that TGF-beta 1 induced VEGF was biologically active. We conclude that TGF-beta 1 in addition to an extracellular matrix regulator also could play a key role in bronchial angiogenesis and vascular remodelling via VEGF pathway in asthma.

Effectiveness and causes for failure of surveillance of CDKN2A-mutated melanoma families.

BACKGROUND: For more than 25 years families with an increased susceptibility to melanoma have been under surveillance at our institution. OBJECTIVE: We sought to investigate the effectiveness of surveillance for CDKN2A-mutated families and causes for failure of the program in patients with more advanced tumors. METHODS: In a retrospective case-control study, Breslow thickness of melanomas diagnosed in relatives enrolled in the surveillance program were compared with melanomas of unscreened index patients. We investigated the influence of mode of detection and length of surveillance interval on outcome. RESULTS: Surveillance melanomas (n = 226, median thickness: 0.50 mm) had a significantly lower Breslow thickness (multiplication factor: 0.61 [95% confidence interval 0.47-0.80], P < .001) than index melanomas (n = 40, median thickness: 0.98 mm). Index melanomas were more likely diagnosed with a Breslow thickness greater than 1.0 mm (odds ratio: 3.1 [95% confidence interval 1.2-8.1], P = .022). In all, 53% of surveillance melanomas were diagnosed during regular screens, 7% during patients' first screen, 20% between regular screens, and 20% in patients who were noncompliant with the surveillance schedule. The majority of surveillance melanomas (58%) were detected within 6 months after the last screen. There was no correlation between tumor thickness and the length of the screening interval for tumors diagnosed within 24 months since the last screen. LIMITATIONS: The study is retrospective. CONCLUSIONS: Surveillance was associated with earlier detection of melanomas. Noncompliance was an important cause for failing surveillance. Shortening surveillance intervals may advance detection of tumors, but may paradoxically have little impact on prognosis.

[Modern education in histopathology and radiology]. / Modern onderwijs in histopathologie en radiologie.

Radiological and pathological imaging constitute an essential part of modern medicine. Furthermore, by showing microscopic and radiological images many pathological processes can be made clearer and easier to understand. This has consequences for education. Many medical faculties are switching partly or entirely to the use of 'virtual microscopy', which amounts to studying digitalised histological preparations with the help of software that shows striking similarities to Google Earth. The requesting physician of the future will be able to make the most effective use of radiological tests when he or she has been trained in 'radiological thinking'. Students must realise that radiology depends not just on looking, as one might at holiday snaps, but more especially on interpreting what is seen. By using modern aids, it is possible to test the listeners' knowledge during lectures as a basis for the rest of the presentation. Collections of educational images are now widely available, including on the Internet.

Nevus versus melanoma: to FISH, or not to FISH.

Fluorescence in-situ hybridization (FISH) has arisen as a novel ancillary test for the pathological diagnosis of melanoma. It is an outgrowth of studies using comparative genomic hybridization, a technique capable of surveying the entire genome for DNA copy number changes. An original report published in 2009 showed high sensitivity (87%) and specificity (95%) for diagnosing melanoma, using a combination of 4 FISH probes that target 6p25 (RREB1), 6q23 (MYB), 11q13 (CCND1), and chromosome 6 centromere. Since then, a number of studies have been published, supporting the high accuracy of FISH for diagnosing melanoma. In addition, various clinicopathological settings where FISH may be particularly useful are explored. FISH tests for melanoma are now commercially available. Meanwhile, questions have been raised by some about the true diagnostic value of FISH, particularly in melanocytic lesions with ambiguous histopathology. This review will briefly introduce the historical development of FISH for melanoma diagnosis and discuss its diagnostic value as well as its potential limitations at present.

Platelet-derived growth factor receptor-ß and epidermal growth factor receptor in pulmonary vasculature of systemic sclerosis-associated pulmonary arterial hypertension versus idiopathic pulmonary arterial hypertension and pulmonary veno-occlusive disease: a case-control study.

INTRODUCTION: Systemic sclerosis (SSc) complicated by pulmonary arterial hypertension (PAH) carries a poor prognosis, despite pulmonary vascular dilating therapy. Platelet-derived growth factor receptor-ß (PDGFR-ß) and epidermal growth factor receptor (EGFR) are potential therapeutic targets for PAH because of their proliferative effects on vessel remodelling. To explore their role in SScPAH, we compared PDGFR- and EGFR-mmunoreactivity in lung tissue specimens from SScPAH. We compared staining patterns with idiopathic PAH (IPAH) and pulmonary veno-occlusive disease (PVOD), as SScPAH vasculopathy differs from IPAH and sometimes displays features of PVOD. Immunoreactivity patterns of phosphorylated PDGFR-ß (pPDGFR-ß) and the ligand PDGF-B were evaluated to provide more insight into the patterns of PDGFR-b activation. METHODS: Lung tissue specimens from five SScPAH, nine IPAH, six PVOD patients and five controls were examined. Immunoreactivity was scored for presence, distribution and intensity. RESULTS: All SScPAH and three of nine IPAH cases (P = 0.03) showed PDGFR-ß-immunoreactivity in small vessels (arterioles/venules); of five SScPAH vs. two of nine IPAH cases (P = 0.02) showed venous immunoreactivity. In small vessels, intensity was stronger in SScPAH vs. IPAH. No differences were found between SScPAH and PVOD. One of five normal controls demonstrated focally mild immunoreactivity. There were no differences in PDGF-ligand and pPDGFR-b-immunoreactivity between patient groups; however, pPDGFR-b-immunoreactivity tended to be more prevalent in SScPAH small vasculature compared to IPAH. Vascular EGFR-immunoreactivity was limited to arterial and arteriolar walls, without differences between groups. No immunoreactivity was observed in vasculature of normals. CONCLUSIONS: PDGFR-ß-immunoreactivity in SScPAH is more common and intense in small- and post-capillary vessels than in IPAH and does not differ from PVOD, fitting in with histomorphological distribution of vasculopathy. PDGFR-ß immunoreactivity pattern is not paralleled by pPDGFR-ß or PDGF-B patterns. PDGFR-ß- and EGFR-immunoreactivity of pulmonary vessels distinguishes PAH patients from controls.

The essence of senescence.

Almost half a century after the first reports describing the limited replicative potential of primary cells in culture, there is now overwhelming evidence for the existence of "cellular senescence" in vivo. It is being recognized as a critical feature of mammalian cells to suppress tumorigenesis, acting alongside cell death programs. Here, we review the various features of cellular senescence and discuss their contribution to tumor suppression. Additionally, we highlight the power and limitations of the biomarkers currently used to identify senescent cells in vitro and in vivo.