Up-regulation of DDX39 in human malignant pleural mesothelioma cell lines compared to normal pleural mesothelial cells

Malignant pleural mesothelioma (MPM) is a malignant tumor originating from mesothelial cells existing in pleura. Since its incidence, it is closely related to the amount and time of exposure to asbestos, and the latency period after exposure to asbestos is very long, the incidence may increase over the next two decades. Since early detection is very difficult and there is no standard curative therapy, it is important to understand the biology of MPM, and to find biomarkers and molecular targets for its therapy. DDX39 is one of the Asp-Glu-Ala-Asp (DEAD)-box RNA helicases, which are required for the export of mRNA out of the nucleus, and transcription, splicing and transport of mRNA. Some reports have shown differential expression of DDX39 in tumor cells or tissues such as lung squamous cell cancer, gastrointestinal stromal tumor and urinary bladder cancer. In the present study, the protein levels of DDX39 in the human MPM cell lines NCI-H28, NCI-H2052 and NCI-H2452, and the human pleural mesothelial cell line MeT-5A were investigated by western blotting. The protein levels of DDX39 were found to be higher in NCI-H28, NCI-H2052 and NCI-H2452 compared to MeT-5A. The intensity of the bands of DDX39 in NCI-H28, NCI-H2052 and NCI-H2452 cells were increased by 1.351-, 1.887- and 2.024-fold, respectively, compared to MPM cells. These results suggest that DDX39 is a possible candidate biomarker for molecular-targeting of MPM.