Secreted form of EphA7 in lung cancer.

EPHA7 is a member of the EPHA family of receptor kinases, among which several members are known to be involved in human lung carcinogenesis. We report here a novel spliced variant, the so-called secreted form of EPHA7, recently reported in malignant lymphoma, in human lung cancer cell lines and primary lung cancer. In contrast to the EPHA7 down-regulation in colorectal cancer by promoter hypermethylation, EPHA7 is expressed at a substantial level in most human lung cancers and the secreted form of EPHA7 mRNA was found in a fraction of primary lung cancer tissues, lung cancer cell lines, and immortalized bronchogenic epithelial cell lines. Interestingly, the secreted form of EPHA7 message was predominantly detected in non-adeno type lung carcinoma. The mechanistic role of the secreted form of EPHA7 in human lung carcinogenesis is not clear, but the presence of this form could distinctly exclude adenocarcinoma of the lung from the other categories, i.e., squamous cell carcinoma, small cell carcinoma and large cell carcinoma, which have strong association with smoking. This is the first study to detect the secreted form of EPHA7 in human epithelial tissues. EPHA7 warrants further investigation to determine its possible involvement in smoking related lung carcinogenesis.