BackgroundMalignant pleural mesothelioma (MPM) is an aggressive malignant tumor of mesothelial origin that shows a limited response to conventional chemotherapy and radiotherapy. Therefore, diagnosing MPM early is very important. Some researchers have previously reported that high-mobility group box 1 (HMGB1) was correlated with pulmonary fibrosis. MPM involves the malignant transformation of mesothelial cells, which originate from mesenchymal cells similar to lung fibroblasts. Here, we investigated serum levels of HMGB1 in patients with MPM and compared them with those of a population that had been exposed to asbestos without developing MPM.MethodsHMGB1 production from MPM cell lines was measured using ELISA. Serum HMGB1 levels were also examined in 61 MPM patients and 45 individuals with benign asbestos-related diseases.ResultsHMGB1 concentrations of 2 out of 4 MPM cell lines were higher than that of normal mesothelial cell line, Met-5A. We demonstrated that patients with MPM had significantly higher serum levels of HMGB1 than the population who had been exposed to asbestos but had not developed MPM. The difference in overall survival between groups with serum HMGB1 levels that were lower and higher than assumed cut-off values was significant.ConclusionsOur data suggest that serum HMGB1 concentration is a useful prognostic factor for MPM.

Background/Aims: The present study investigated adenosine-induced apoptosis in human malignant pleural mesothelioma cells. Methods: MTT assay, TUNEL staining, flow cytometry using propidium iodide and annexin V-FITC, real-time RT-PCR, Western blotting, and assay of caspase-3, -8, and -9 activities were carried out using malignant pleural mesothelioma cell lines such as NCI-H28, NCI-H2052, NCI-H2452, and MSTO-211H cells, and p53 or A₃ adenosine receptor was knocked-down by transfecting each siRNA into cells. Results: Adenosine induced apoptosis in all the malignant pleural mesothelioma cells used here, independently of caspase activation. The adenosine effect was prevented by the adenosine transporter inhibitor dipyridamole, the adenosine kinase inhibitor ABT-702, or the A₃ adenosine receptor inhibitor MRS1191. Adenosine upregulated expression of the p53 mRNA and protein, that is abolished by ABT-702, but not by knocking-down A₃ adenosine receptor. Adenosine-induced apoptosis in NCI-H28 cells was significantly inhibited by knocking-down p53 and in part by knocking-down A₃ adenosine receptor. Conclusion: The results of the present study show that AMP converted from intracellularly transported adenosine upregulates p53 expression to induce caspase-independent apoptosis in malignant pleural mesothelioma cells and that A₃ adenosine receptor also participates partially in the apoptosis by the different mechanism.

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We have previously reported that angiopoietin-1 was correlated with pulmonary fibrosis. Here, we investigated the serum levels of angiopoietin-1 in patients with malignant peritoneal mesothelioma, which originate from mesenchymal cells similar to lung fibroblasts. We showed that patients with peritoneal mesothelioma had significantly higher serum levels of angiopoietin-1 in comparison with a population with a history of asbestos exposure without peritoneal mesothelioma, and the Kaplan-Meier method revealed a significant correlation between serum angiopoietin-1 levels and survival. This is the first report about the relationship between angiopoietin-1 and peritoneal mesothelioma.

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