Establishment and characterization of CRISPR /Cas9‐mediated NF 2 −/− human mesothelial cell line: Molecular insight into fibroblast growth factor receptor 2 in malignant pleural mesothelioma

Malignant pleural mesothelioma ( MPM ), a highly refractory tumor, is currently incurable due to the lack of an early diagnosis method and medication, both of which are urgently needed to improve the survival and/or quality of life of patients. NF 2 is a tumor suppressor gene and is frequently mutated in MPM . Using a CRISPR /Cas9 system, we generated an NF 2‐ knockout human mesothelial cell line, MeT‐5A ( NF 2‐ KO ). In NF 2‐ KO cell clones, cell growth, clonogenic activity, migration activity, and invasion activity significantly increased compared with those in NF 2‐ WT cell clones. Complementary DNA microarray analysis clearly revealed the differences in global gene expression profile between NF 2‐ WT and NF 2‐ KO cell clones. Quantitative PCR analysis and western blot analysis showed that the upregulation of fibroblast growth factor receptor 2 ( FGFR 2) was concomitant with the increases in phosphorylation levels of JNK , c‐Jun, and retinoblastoma (Rb) in NF 2‐ KO cell clones. These increases were all abrogated by the exogenous expression of NF 2 in the NF 2‐ KO clone. In addition, the disruption of FGFR 2 in the NF 2‐ KO cell clone suppressed cell proliferation as well as the phosphorylation levels of JNK , c‐Jun, and Rb. Notably, FGFR 2 was found to be highly expressed in NF 2‐negative human mesothelioma tissues (11/12 cases, 91.7%) but less expressed in NF 2‐positive tissues. Collectively, these findings suggest that NF 2 deficiency might play a role in the tumorigenesis of human mesothelium through mediating FGFR 2 expression; FGFR 2 would be a candidate molecule to develop therapeutic and diagnostic strategies for targeting MPM with NF 2 loss.