Proteomic differential display analysis identified upregulated astrocytic phosphoprotein PEA‐15 in human malignant pleural mesothelioma cell lines

We performed proteomic differential display analysis of human malignant pleural mesothelioma (MPM) cell lines and a human pleural mesothelial cell line by using 2‐DE and LC‐MS/MS. The human MPM cell lines were NCI‐H28, NCI‐H2052 and NCI‐H2452, and the human pleural mesothelial cell line was MeT‐5A. Between MeT‐5A and NCI‐H2052, we found 38 protein spots whose expression levels were different, from the results of 2‐DE; 28 protein spots appeared higher, and 10 other protein spots lower in NCI‐H2052 than in MeT‐5A. These spots were analyzed by LC‐MS/MS analysis and identified by a peptide sequence tag. However, from the results of 2‐DE of the other cell lines, there was only one consistently upregulated protein, astrocytic phosphoprotein PEA‐15, in all three MPM cell lines. Western blotting using specific antibodies against PEA‐15 confirmed the elevated expression level of PEA‐15 in all three MPM cell lines compared with MeT‐5A cells and normal pleura tissues from patients. PEA‐15 was knocked down in NCI‐H2052 cells, and the proliferation of PEA‐15‐silenced NCI‐H2052 cells was suppressed 7–15% compared with negative control cells. These results suggest that PEA‐15 expression is likely to be associated with the tumorigenesis of MPM.