title: The synthetic peptide P111-136 derived from the C-terminal domain of heparin affin regulatory peptide inhibits tumour growth of prostate cancer PC-3 cells.
abstract: BACKGROUND
  Heparin affin regulatory peptide (HARP), also called pleiotrophin, is a heparin-binding, secreted factor that is overexpressed in several tumours and associated to tumour growth, angiogenesis and metastasis. The C-terminus part of HARP composed of amino acids 111 to 136 is particularly involved in its biological activities and we previously established that a synthetic peptide composed of the same amino acids (P111-136) was capable of inhibiting the biological activities of HARP. Here we evaluate the ability of P111-136 to inhibit in vitro and in vivo the growth of a human tumour cell line PC-3 which possess an HARP autocrine loop.
  
  
  METHODS
  A total lysate of PC-3 cells was incubated with biotinylated P111-136 and pulled down for the presence of the HARP receptors in Western blot. In vitro, the P111-136 effect on HARP autocrine loop in PC-3 cells was determined by colony formation in soft agar. In vivo, PC-3 cells were inoculated in the flank of athymic nude mice. Animals were treated with P111-136 (5 mg/kg/day) for 25 days. Tumour volume was evaluated during the treatment. After the animal sacrifice, the tumour apoptosis and associated angiogenesis were evaluated by immunohistochemistry. In vivo anti-angiogenic effect was confirmed using a mouse Matrigel™ plug assay.
  
  
  RESULTS
  Using pull down experiments, we identified the HARP receptors RPTPβ/ζ, ALK and nucleolin as P111-136 binding proteins. In vitro, P111-136 inhibits dose-dependently PC-3 cell colony formation. Treatment with P111-136 inhibits significantly the PC-3 tumour growth in the xenograft model as well as tumour angiogenesis. The angiostatic effect of P111-136 on HARP was also confirmed using an in vivo Matrigel™ plug assay in mice
  
  
  CONCLUSIONS
  Our results demonstrate that P111-136 strongly inhibits the mitogenic effect of HARP on in vitro and in vivo growth of PC-3 cells. This inhibition could be linked to a direct or indirect binding of this peptide to the HARP receptors (ALK, RPTPβ/ζ, nucleolin). In vivo, the P111-136 treatment significantly inhibits both the PC-3 tumour growth and the associated angiogenesis. Thus, P111-136 may be considered as an interesting pharmacological tool to interfere with tumour growth that has now to be evaluated in other cancer types.
authors.affiliation: Laboratoire de Recherche sur la Croissance Cellulaire, la Réparation et la Régénération Tissulaires, Université Paris Est Créteil, CNRS, avenue du Général de Gaulle, 94010 Créteil Cedex, France.
authors.forename: Yamina
authors.initials: Y
authors.lastname: Hamma-Kourbali
authors.forename: Oya
authors.initials: O
authors.lastname: Bermek
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bernard-Pierrot
authors.forename: Racha
authors.initials: R
authors.lastname: Karaky
authors.forename: Dominique
authors.initials: D
authors.lastname: Martel-Renoir
authors.forename: Sophie
authors.initials: S
authors.lastname: Frechault
authors.forename: José
authors.initials: J
authors.lastname: Courty
authors.forename: Jean
authors.initials: J
authors.lastname: Delbé
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016207:Cytokines / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000473:pathology; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D002352:Carrier Proteins; D016207:Cytokines; D010455:Peptides; C066845:pleiotrophin