title: RBBP9: a tumor-associated serine hydrolase activity required for pancreatic neoplasia.
abstract: Pancreatic cancer is one of the most lethal malignancies. To discover functionally relevant modulators of pancreatic neoplasia, we performed activity-based proteomic profiling on primary human ductal adenocarcinomas. Here, we identify retinoblastoma-binding protein 9 (RBBP9) as a tumor-associated serine hydrolase that displays elevated activity in pancreatic carcinomas. Whereas RBBP9 is expressed in normal and malignant tissues at similar levels, its elevated activity in tumor cells promotes anchorage-independent growth in vitro as well as pancreatic carcinogenesis in vivo. At the molecular level, RBBP9 activity overcomes TGF-beta-mediated antiproliferative signaling by reducing Smad2/3 phosphorylation, a previously unknown role for a serine hydrolase in cancer biology. Conversely, loss of endogenous RBBP9 or expression of mutationally inactive RBBP9 leads to elevated Smad2/3 phosphorylation, implicating this serine hydrolase as an essential suppressor of TGF-beta signaling. Finally, RBBP9-mediated suppression of TGF-beta signaling is required for E-cadherin expression as loss of the serine hydrolase activity leads to a reduction in E-cadherin levels and a concomitant decrease in the integrity of tumor cell-cell junctions. These data not only define a previously uncharacterized serine hydrolase activity associated with epithelial neoplasia, but also demonstrate the potential benefit of functional proteomics in the identification of new therapeutic targets.
authors.affiliation: Department of Pathology, Moores Cancer Center, University of California, San Diego, CA 92093-0803, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Shields
authors.forename: Sherry
authors.initials: S
authors.lastname: Niessen
authors.forename: Eric A
authors.initials: EA
authors.lastname: Murphy
authors.forename: Ainhoa
authors.initials: A
authors.lastname: Mielgo
authors.forename: Jay S
authors.initials: JS
authors.lastname: Desgrosellier
authors.forename: Steven K M
authors.initials: SK
authors.lastname: Lau
authors.forename: Leo A
authors.initials: LA
authors.lastname: Barnes
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Lesperance
authors.forename: Michael
authors.initials: M
authors.lastname: Bouvet
authors.forename: David
authors.initials: D
authors.lastname: Tarin
authors.forename: Benjamin F
authors.initials: BF
authors.lastname: Cravatt
authors.forename: David A
authors.initials: DA
authors.lastname: Cheresh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D021441:Carcinoma, Pancreatic Ductal / Q000201:enzymology* / Q000209:etiology / Q000473:pathology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000201:enzymology* / Q000209:etiology / Q000473:pathology; D010766:Phosphorylation; D040901:Proteomics; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D015820:Cadherins; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; C485185:RBBP9 protein, human; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D012697:Serine Endopeptidases