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.