CDNA CLONING OF A NOVEL TRYPSIN-INHIBITOR WITH SIMILARITY TO PATHOGENESIS-RELATED PROTEINS, AND ITS FREQUENT EXPRESSION IN HUMAN BRAIN CANCER-CELLS

A navel trypsin inhibitor (P25TI) with an apparent molecular size of 2 5 kDa has previously been purified from the culture medium of human gl ioblastoma cells, In this study, the cDNA encoding P25TI was isolated by the polymerase chain reaction (PCR) screening system, and its compl ete amino acid sequence was determined, The cDNA consisted of 1440 nuc leotides and encoded a sequence of 258 amino acids, The deduced struct ure of P25TI seemed to consist of a putative signal peptide sequence ( residues 1-25), a propeptide sequence (26-60) and a mature protein (re sidues 61-258), The P25TI sequence has no homology to other proteinase inhibitors, but has similarity to insect venom allergens, mammalian t estis-specific proteins and plant pathogenesis-related proteins. P25TI mRNA was frequently expressed in human neuroblastoma and glioblastoma cell lines, Although Northern blotting analysis failed to detect P25T I mRNA ill various human tissues, PCR analysis showed its expression I n the brain, placenta and lymphocytes. (C) 1998 Elsevier Science B.V.