Thorsten Wiethege

Hepatocyte growth factor/scatter factor and its receptor c-met are overexpressed and associated with an increased microvessel density in malignant pleural mesothelioma

Abstract Hepatocyte growth factor/scatter factor (HGF/SF) stimulates cell proliferation, motility and invasiveness via its receptor c-Met during embryogenesis and repair processes. It induces angiogenesis, promoting endothelial cell migration and capillary-tube formation in vivo. Co-expression of HGF/SF and c-Met receptor results in enhanced tumour growth, invasiveness and a mesenchymal-epithelial transition in some experimental tumours. Since mesothelioma cells have been reported to express c-Met receptor and to migrate in response to HGF/SF, we investigated human malignant pleural mesotheliomas for the demonstration of possible co-expression of the growth factor and its receptor. The microvessel density of the tumours was also analysed in order to assess the influence of HGF/SF expression on tumour angiogenesis. Thirty-nine paraffin-embedded specimens of malignant pleural mesotheliomas were immunostained by anti-HGF/SF and anti-c-Met antibodies and semiquantitatively evaluated. c-Met mRNA expression was visualised in ten tumour samples by a fluorescent in situ hybridisation method. Microvessel density was calculated by counting microvessels with a high-power field (200×) on von-Willebrand-factor-stained slides. We found an increased production of HGF/SF in 33/39 tumours and a corresponding overexpression of c-Met receptor in 29/39 specimens. The FISH method detected increased transcription of c-Met mRNA in malignant cells and in neighbouring vascular endothelial cells. HGF/SF-positive mesotheliomas had significantly higher microvessel densities compared to their HGF/SF-negative counterparts. The observed co-expression of HGF/SF and c-Met in malignant pleural mesotheliomas suggests a possible self-stimulation (autocrine loop) of tumour cells. On the basis of the significantly higher microvessel density values of malignant mesotheliomas overexpressing HGF/SF, we postulate, that HGF/SF may be an additional relevant factor in tumour angiogenesis in malignant pleural mesotheliomas.

Presence of simian virus 40 sequences in malignant mesotheliomas and mesothelial cell proliferations

Malignant mesotheliomas (MMs) are pleural‐, pericardial‐, or peritoneal‐based neoplasms usually associated with asbestos exposure. Mesothelial cells are biphasic and may give rise to epithelial and sarcomatous MMs. In addition, benign or atypical proliferations of mesothelial cells may occur in response to many stimuli. There have been recent reports of simian virus 40 (SV40) DNA large T antigen (Tag) sequences in pleural MMs. To further understand the relationship between SV40, MMs, and mesothelial proliferations, we studied 118 MMs from multiple sites in Germany and North America, including 93 epithelial pleural, 14 sarcomatous or mixed pleural MMs, and 11 peritoneal MMs. In 12 pleural MMs, adjacent noninvasive tumor foci were identified and studied separately. Information about asbestos exposure (detailed history and/or microscopic examination for asbestos bodies) was available from 43 German patients. In addition, 13 examples of reactive mesothelium and 20 lung cancers from the United States were tested. DNA was extracted from frozen tumor and adjacent nontumorous tissues or after microdissection of archival formalin‐fixed, paraffin‐embedded microslides. Two rounds of PCR were performed with primers SVFor 3 and SVRev, which amplify a 105 bp region specific for SV40 Tag. The specificity of the PCR product was confirmed in some cases by sequencing. Our major findings were: 1) Specific SV40 viral sequences were present in 57% of epithelial invasive MMs, of both pleural and peritoneal origin. No significant geographic differences were found, and frozen and paraffin‐embedded tissues were equally suitable for analysis. 2) There was no apparent relationship between the presence of SV40 sequences and asbestos exposure. 3) SV40 sequences were present in the surface (noninvasive) components of epithelial MMs. 4) SV40 sequences were not detected in MMs of sarcomatous or mixed histologies. 5) Viral sequences were present in two of 13 samples (15%) of reactive mesothelium. 6) Lung cancers lacked SV40 sequences, as did non‐malignant tissues adjacent to MMs. Our findings demonstrate the presence of SV40 sequences in epithelial MMs of pleural and peritoneal origin and their absence in tumors with a sarcomatous component. Viral sequences may be present in reactive and malignant mesothelial cells, but they are absent in adjacent tissues and lung cancers. J. Cell. Biochem. 76:181–188, 1999.

Expression of vascular endothelial growth factor in diffuse malignant pleural mesothelioma

Abstract Angiogenesis is an important part of normal and pathological processes, including tumour growth, metastasis, inflammation and wound healing. VEGF is the best known angiogenic factor, implicated in tumour-associated microvascular hyperpermeability and carcinogenesis. We investigated 103 malignant pleural mesotheliomas, analysing the expression of vascular endothelial growth factor using immunohistochemistry and insitu hybridization. The grade of microvessel density was assessed with the aid of anti-factor-VIII antibodies. An increased expression of VEGF was found in biphasic and epithelioid mesotheliomas, correlating in a statistically significant manner (P<0.042). Insitu hybridization confirmed the specificity of VEGF mRNA expression. There was a robust correlation between VEGF expression and increased microvessel density (P<0.001), and positive mesotheliomas had significantly higher microvessel densities than negative specimens. There was also a significant correlation between microvessel density and histological pattern. As growth pattern tended towards biphasic and sarcomatoid mesotheliomas the density of micovessels decreased (P<0.05).

Histopathologic findings of lung carcinoma in German uranium miners

This study evaluates the histopathology of lung carcinoma in relation to underground radon exposure.

Expression and localization of vascular endothelial growth factor and its receptor flt in pulmonary sarcoidosis

Abstract Vascular endothelial growth factor (VEGF) is a multifunctional cytokine, which has recently been reported to enhance the activation and migration of monocytes through the flt receptor in vitro, which are key events in granuloma formation of granulomatous disorders and in sarcoidosis. Since activated macrophages and monocytes are known to be involved in sarcoid granuloma formation in sarcoidosis, we investigated the expression of VEGF and its receptor flt in 33 paraffin-embedded lung tissue biopsies of patients with pulmonary sarcoidosis. VEGF-mRNA was localized by nonradioactive in situ hybridization, VEGF and flt expression were visualized immunohistochemically. We found an increased transcription and protein production of VEGF and an overexpression of flt in activated alveolar macrophages, in epitheloid cells, and in multinuclear giant cells of pulmonary sarcoid granulomas.

Co-Expression of Vascular Endothelial Growth Factor and Its Receptor flt-1 in Malignant Pleural Mesothelioma

Background: Vascular endothelial growth factor (VEGF) is a potent angiogenic protein with a selective mitogenic effect on endothelial cells known to be involved in many normal and pathological processes. Coexpression of VEGF and its receptor flt-1 has been reported in different types of malignant tumors. Objective: In the present study we investigated the expression of VEGF and flt-1 in 90 cases of diffuse malignant pleural mesotheliomas. Methods: VEGF and flt-1 expression was analyzed by immunohistochemistry and non-radioactive in situ hybridization. Results: VEGF expression was visualized immunohistochemically in tumor cells. flt-1 expression correlated with histological differentiation (p < 0.013). Furthermore, expression of flt-1 was detected in tumor cells, macrophages and microvessels adjacent to tumor cells. VEGF and flt-1 expression were confirmed by in situ hybridization. Conclusion: There was a statistically significant correlation between VEGF and flt-1 expression (p < 0.001). The observed coexpression of VEGF and flt-1 possibly suggests a potential autocrine loop for malignant pleural mesothelioma cells.

Role of exposure to radon and silicosis on the cell type of lung carcinoma in German uranium miners

In East Germany, uranium mining was undertaken on a large scale from 1946 to 1990. Poor working conditions led to a high level of exposure to ionizing radiation and quartz dust. This analysis evaluates the histopathology of lung carcinoma in uranium miners in relation to radon exposure and silicosis.

Cancer mortality in a surveillance cohort of German males formerly exposed to asbestos.

The objective of this analysis was the estimation of the cancer risks of asbestos and asbestosis in a surveillance cohort of high-exposed German workers. A group of 576 asbestos workers was selected for high-resolution computer tomography of the chest in 1993-1997. A mortality follow-up was conducted through 2007. Standardised mortality ratios (SMRs) were calculated and Poisson regression was performed to assess mesothelioma risks. A high risk was observed for pleural mesothelioma (SMR 28.10, 95% CI 15.73-46.36) that decreased after cessation of exposure (RR 0.1; 95% CI 0.0-0.6 for > or =30 vs. <30 years after last exposure). Asbestosis was a significant risk factor for mesothelioma (RR 6.0, 95% CI 2.4-14.7). Mesothelioma mortality was still in excess in former asbestos workers although decreasing after cessation of exposure. Fibrosis was associated with subsequent malignancy.

Detection of transforming growth factor beta1 mRNA in cerebrospinal fluid cells of patients with meningitis by non-radioactive in situ hybridization

Meningitis is a serious disease mostly caused by viral or bacterial infections. In complicated cases it may lead to brain damage and death. The infection and cell damage result in a cellular and immunological response. Following this, a high secretion of cytokines can be expected. Cytokines, especially tumour necrosis factor alpha (TNF-alpha) and interleukin-1 (IL-1), promote the inflammatory reactions in the subarachnoid space. Transforming growth factor beta1 (TGF-beta1) has antagonistic effects on TNF-alpha and IL-1-mediated processes. Therefore, it suppresses inflammatory reactions. To observe the expression of TGF-betal in transcellular signalling in the inflammatory processes of meningitis, we investigated TGF-betal mRNA in cells in the cerebrospinal fluid of three patients with meningitis by non-radioactive in situ hybridization. All patients fulfilled the usual clinical criteria of meningitis. In one caseNeisseria menigitidis could be identified as the pathogenic agent. In the remainder, no agent could be isolated. In all cytological preparations of the cerebrospinal fluid of these patients a high level of TGF-betal mRNA was detectable in the cell populations. It was possible to distinguish between the different cell types of the cerebrospinal fluid and to attach the mRNA expression to them. On the one hand, this makes it possible to investigate pathogenesis and defence mechanisms in bacterial and aseptic meningitis on a cellular level; on the other hand, it may open new perspectives in the control of disease development, prognosis, diagnosis and supporting therapy.

A Study on Lung Cancer Mortality Related to Radon, Quartz, and Arsenic Exposures in German Uranium Miners

Between 1946 and 1990 uranium mining was undertaken on a large scale in East Germany. This study evaluates the proportional lung cancer risk of German uranium miners from radon, quartz, and arsenic exposure during mining operations at the WISMUT Corporation. The database of the WISMUT tissue repository and a comprehensive job-exposure matrix were used to compare exposure levels of lung cancer cases with deaths from diseases of the circulatory system for risk analysis. In addition, the ratio of lung cancer cases was compared to cases from diseases of the circulatory system to the corresponding ratio in the general population. The proportional lung cancer mortality of German uranium miners was 2.9-fold higher than in the general population of East Germany. Cumulative radon, quartz, and arsenic exposure were determined as risk factors for lung cancer among German uranium miners, where silicosis modified the risk of cumulative radon and quartz exposure. Silicotics were exposed to higher levels of quartz, radon, and arsenic than nonsilicotics. Because selection of the study population was based on a tissue repository, the results need to be interpreted with caution.