title: BRK/Sik expression in the gastrointestinal tract and in colon tumors.
abstract: Clones encoding the breast tumor kinase BRK were isolated from a normal human small intestinal cDNA library that was screened with the cDNA encoding the mouse epithelial-specific tyrosine kinase Sik. Although BRK and Sik share only 80% amino acid sequence identity, Southern blot hybridizations confirmed that the two proteins are orthologues. Sik was mapped to mouse distal chromosome 2, which shows conservation of synteny with human chromosome 20q13.3, the location of the BRK gene. BRK expression was examined in the normal gastrointestinal tract, colon tumor cell lines, and primary colon tumor samples. Like Sik, BRK is expressed in normal epithelial cells of the gastrointestinal tract that are undergoing terminal differentiation. BRK expression also increased during differentiation of the Caco-2 colon adenocarcinoma cell line. Modest increases in BRK expression were detected in primary colon tumors by RNase protection, in situ hybridization, and immunohistochemical assays. The BRK tyrosine kinase appears to play a role in signal transduction in the normal gastrointestinal tract, and its overexpression may be linked to the development of a variety of epithelial tumors.
authors.affiliation: Department of Molecular Genetics, University of Illinois College of Medicine, Chicago 60607, USA.
authors.forename: X
authors.initials: X
authors.lastname: Llor
authors.forename: M S
authors.initials: MS
authors.lastname: Serfas
authors.forename: W
authors.initials: W
authors.lastname: Bie
authors.forename: V
authors.initials: V
authors.lastname: Vasioukhin
authors.forename: M
authors.initials: M
authors.lastname: Polonskaia
authors.forename: J
authors.initials: J
authors.lastname: Derry
authors.forename: C M
authors.initials: CM
authors.lastname: Abbott
authors.forename: A L
authors.initials: AL
authors.lastname: Tyner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D014408:Biomarkers, Tumor / Q000096:biosynthesis*; D018938:Caco-2 Cells; D002890:Chromosomes, Human, Pair 20; D003110:Colonic Neoplasms / Q000737:chemistry / Q000378:metabolism*; D004064:Digestive System / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human; C000598269:Ptk6 protein, mouse; D019061:src-Family Kinases