Functional analysis of Discoidin domain receptor 2 mutation and expression in squamous cell lung cancer.

OBJECTIVES: Discoidin domain receptor (DDR) 2 mutations have recently been reported to be candidate targets of molecular therapy in lung squamous cell carcinoma (SQCC). However, the status of DDR2 expression and mutations, as well as their precise roles in lung SQCC, have not been clarified. We here report DDR2 mutation and expression status in clinical samples and its role of lung SQCC.

MATERIALS AND METHODS: We investigated DDR2 expression and mutation status in 44 human clinical samples and 7 cell lines. Biological functions of DDR2 were assessed by in vitro cell invasion assay and animal model experiments.

RESULTS: Endogenous DDR2 protein expression levels were high in one cell line, PC-1, and immunohistochemistry of lung cancer tissue array showed high levels of DDR2 protein in 29% of lung SQCC patients. A mutation (T681I) identified in lung SQCC and the cell line EBC-1 was detected among 44 primary lung SQCC samples and 7 lung SQCC cell lines. Although Forced expression of DDR2 and its mutant (T681I) led to induce SQCC cell invasion in vitro, only wild type DDR2 enhanced lung metastasis in an animal model. We also found that ectopic expression of DDR2 induced MMP-1 mRNA expression accompanied by phosphorylation of c-Jun after treatment with its ligand, collagen type I, but DDR2 with the T681I mutation did not, suggesting that T681I mutation is an inactivating mutation.

CONCLUSION: Overexpression of DDR2 might contribute to tumor progression in lung SQCC. The overexpression of DDR2 could be potential molecular target of lung SQCC.