Proteomic analysis showed heat shock 70 kda protein and 78 kda glucose-regulated protein were up-regulated in human malignant pleural mesothelioma cells

Abstract

Malignant pleural mesothelioma (MPM) is a malignant neoplasm arising from mesothelial cells existing in pleura. It is difficult to identify a crucial symptom in patients with MPM, and there is no standard curative therapy for this malignancy. The incidence of MPM is increasing worldwide, and many patients can not survive more than one year after diagnosis. MPM is an asbestos-related disease, and it is believed that the incidence is closely related to the amount and time of exposure to asbestos. Since the latency period after exposure to asbestos is very long, the incidence may increase over the next two decades. Therefore, it is important to understand the biology of MPM, and to find a molecular target for its therapy. Three of human malignant pleural mesothelioma (MPM) cell lines (NCIH28, NCI-H2052, NCI-H2452) and a human pleural mesothelial cell line (MeT-5A) were analyzed by proteomics with the use of twodimensional gel electrophoresis (2-DE) and liquid chromatographytandem mass spectrometry (LC-MS/MS). From the results of 2-DE between MeT-5A and three MPM cell lines, 9 protein spots showed increased expression levels in MPM cells compared to MeT-5A. These spots were analyzed by LC-MS/MS analysis, and identified by a peptide sequence tag. Identified increased spots included 78 kDa glucose regulated protein (GRP78), heat shock 70 kDa protein (HSP70), protein disulfide isomerase A3, annexin A3, peroxiredoxin-2 and 14 kDa phosphohistidine phosphatase. Western blotting using specific antibodies against GRP78 and HSP70 confirmed the elevated expression level of GRP78 and HSP70 in MPM cell lines compared to MeT-5A cells. These results suggest that GRP78 and HSP70 expression is likely to be associated with the tumorigenesis of MPM, and they may be expectable as biomarkers or therapeutic targets for MPM.