Dysregulated secretoglobin expression in human lung cancers

Lipophilins A, B, C, mammaglobin, and uteroglobin are members of the secretoglobin family of small, secreted, proteins. The functions of these proteins are not well understood but uteroglobin has been implicated in the development of cancers. Uteroglobin is known to be highly expressed in normal lung and down-regulated in lung cancers but expression of the other secretoglobins in normal lung and lung neoplasms have not been investigated. Therefore, we developed quantitative real-time reverse transcription (RT-) PCR assays for the different secretoglobins and evaluated their expression in normal and neoplastic lung tissues. The secretoglobin transcript levels were quantitated by real-time RT-PCR in samples from three normal lungs, 24 lung tumors including six small cell lung carcinomas, seven adenocarcinomas, and five squamous cell carcinomas, and in cell lines from three small cell lung carcinomas and one mesothelioma. Uteroglobin was confirmed to be abundantly expressed in normal lung and the different lung tumors showed down-regulated uteroglobin expression. Of the other secretoglobins, only lipophilin C was detected in normal lung, albeit at low levels. The lung tumors, however, frequently showed neo- or up-regulation of lipophilins A, B, C, and mammaglobin. The results constitute the first quantitative evaluation of secretoglobin expression in normal and neoplastic human lung tissues and demonstrate dysregulation in various human lung cancers. These findings could have important biological and diagnostic implications.