title: Prostatic acid phosphatase is not a prostate specific target.
abstract: Prostatic acid phosphatase (PAP) is currently evaluated as a target for vaccine immunotherapy of prostate cancer. This is based on the previous knowledge about secretory PAP and its high prostatic expression. We describe a novel PAP spliced variant mRNA encoding a type I transmembrane (TM) protein with the extracellular NH(2)-terminal phosphatase activity and the COOH-terminal lysosomal targeting signal (YxxPhi). TM-PAP is widely expressed in nonprostatic tissues like brain, kidney, liver, lung, muscle, placenta, salivary gland, spleen, thyroid, and thymus. TM-PAP is also expressed in fibroblast, Schwann, and LNCaP cells, but not in PC-3 cells. In well-differentiated human prostate cancer tissue specimens, the expression of secretory PAP, but not TM-PAP, is significantly decreased. TM-PAP is localized in the plasma membrane-endosomal-lysosomal pathway and is colocalized with the lipid raft marker flotillin-1. No cytosolic PAP is detected. We conclude that the wide expression of TM-PAP in, for instance, neuronal and muscle tissues must be taken into account in the design of PAP-based immunotherapy approaches.
authors.affiliation: Research Center for Molecular Endocrinology and WHO Collaborating Centre, Biocenter Oulu, University of Oulu, Finland.
authors.forename: Ileana B
authors.initials: IB
authors.lastname: Quintero
authors.forename: César L
authors.initials: CL
authors.lastname: Araujo
authors.forename: Anitta E
authors.initials: AE
authors.lastname: Pulkka
authors.forename: Riikka S
authors.initials: RS
authors.lastname: Wirkkala
authors.forename: Annakaisa M
authors.initials: AM
authors.lastname: Herrala
authors.forename: Eeva-Liisa
authors.initials: EL
authors.lastname: Eskelinen
authors.forename: Eija
authors.initials: E
authors.lastname: Jokitalo
authors.forename: Pekka A
authors.initials: PA
authors.lastname: Hellström
authors.forename: Hannu J
authors.initials: HJ
authors.lastname: Tuominen
authors.forename: Pasi P
authors.initials: PP
authors.lastname: Hirvikoski
authors.forename: Pirkko T
authors.initials: PT
authors.lastname: Vihko
mesh_terms: D000135:Acid Phosphatase; D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011467:Prostate / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
chemical_list: D008565:Membrane Proteins; C106354:flotillins; D000135:Acid Phosphatase; C428439:prostatic acid phosphatase; D017027:Protein Tyrosine Phosphatases