A SOLUBLE FORM OF K-SAM FGFR2 PROTEIN IN THE CULTURE-MEDIUM OF HUMAN GASTRIC-CANCER CELLS

K-SAM/FGFR2 gene encodes a receptor tyrosine kinase which belongs to t he fibroblast growth factor receptor family and is amplified and overe xpressed in KATO-III gastric cancer cells. To characterize K-sam prote ins in cancer cells, anti-K-sam rabbit polyclonal antibody PK1-2 was r aised and used for the immunoprecipitation analysis. 135, 125, and 110 -kDa transmembrane proteins were detected in KATO-III cell lysate, whi le a soluble truncated 85-kDa K-sam protein was found in the condition ed medium. The molecular size of the soluble K-sam protein does not ma tch with those predicted from the secreted forms of the K-sam cDNA whi ch have been cloned so far. The soluble K-sam protein was highly N-gly cosylated like the transmembrane versions, and N-glycosylation appeare d to be necessary for its release. (C) 1994 Academic Press, Inc.