Identification of a neutrophil gelatinase-associated lipocalin mRNA in human pancreatic cancers using a modified signal sequence trap method

To identify the intercellular signal-transducing proteins and receptors produced by cancer cells, we attempted to clone cDNAs encoding secreted and type I membrane proteins using a signal sequence trap (SST) method with some modifications. By screening an SST library derived from pancreatic cancer cells, we identified two secretory proteins (neutrophil gelatinase-associated lipocalin (NGAL) and lung surfactant protein D) and three membrane proteins (carcinoembryonic antigen, BiP/GRP78 and Hsa4 mitochondrion cytochrome oxidase subunit II). NGAL mRNA was expressed in eight of the pancreatic cancer cell lines and eight pancreatic cancer tissues. The expression of NGAL mRNA was also observed in colorectal and hepatic tumors.