Gene expression profile of malignant mesothelioma

Malignant mesothelioma (MM) is an asbestos-related malignancy and largely unresponsive to conventional chemotherapy or radiotherapy. Novel, more effective therapeutic strategies are needed for this fatal disease. We performed microarray analysis of MM using Affymetrix Human U133 Plus 2.0 array. Aberrant expression of the genes participating in semaphorin signaling were detected in malignant mesothelioma cells. All MM cells downregulated the expression of more than one gene for SEMA3B, 3F, and 3G when compared with Met5a, a normal pleura-derived cell line. In 12 of 14 epithelioid MM cells, the expression level of SEMA3A was lower than that in Met5a. An augmented expression of VEGFA was detected in half of the MM cells. The expression ratio of VEGFA/SEMA3A was significantly higher in the epithelioid MMs than in Met5a and the non-epithelioid MMs. Next, gene expression profiling for the polycomb and trithorax group genes revealed that expression of BAP1, the catalytic subunit of the polycomb repressive deubiquitinase complex, and many trithorax group genes was downregulated in MMs compared with the expression of the same genes in Met5a cells. Perturbation of the polycomb–trithorax balance plays a significant role in the pathogenesis of malignant mesothelioma. Array analysis was performed with 19 malignant mesothelioma (MM) cell samples, including 14 primary cell cultures from Japanese patients at the Hospital of Hyogo College of Medicine, and with two primary cell cultures of reactive mesothelial hyperplasia (RM) and human normal pleura transformant Met5a as reference cells.