ISOLATION AND CHARACTERIZATION OF AN EPITHELIAL-SPECIFIC RECEPTOR TYROSINE KINASE FROM AN OVARIAN-CANCER CELL-LINE

A protein receptor tyrosine kinase (RTK 6) has been isolated from a co mplementary DNA library of SKOV-3, an epithelial ovarian cancer cell l ine, using a polymerase chain reaction (PCR)-mediated approach. The pr imary structure of the predicted amino acid sequence of the protein sh ows a novel NH2-terminal region which has homology to a factor VIII-li ke domain. The juxtamembrane region is proline and glycine rich and is the longest for any known receptor kinase. The COOH-terminal catalyti c domain has all of the canonical sequence motifs of a receptor tyrosi ne kinase with homology to the TRK-2H protein (49%). A single transcri pt of 4.5 kilobases is expressed at low levels in heart, placenta, lun g, liver, muscle, kidney, and pancreas, with high levels of expression in the brain. Ribonuclease protection assay showed a varying level of expression of message in a panel of eight ovarian cancer cell lines c ompared to placenta. In situ hybridization analysis demonstrated local ization of mRNA in the epithelial cells of the ovary, kidney, small bo wel, lung, thymus, and brain. There was a lower level of message in no rmal, benign, and borderline tumors of the ovary compared to malignant tumors of the ovary. Polyclonal antisera raised against a COOH-termin al synthetic peptide recognize a M(r) 140,000 protein in ovarian cance r cells, which autophosphorylates in an in vitro kinase assay.