title: Both osteopontin-c and osteopontin-b splicing isoforms exert pro-tumorigenic roles in prostate cancer cells.
abstract: BACKGROUND
  Alternative splicing of the osteopontin (opn, spp1) gene generates three protein splicing isoforms (OPN-SI), designated as OPNa, OPNb, and OPNc, which have demonstrated specific roles in different tumor models. This work aims to investigate the roles of each OPN-SI in prostate cancer (PCa) progression by using in vivo and in vitro functional assays.
  
  
  METHODS
  The expression levels of OPN-SI in prostate cell lines were analyzed by qRT-PCR. PC-3 was stably transfected with expression vectors containing OPNa, OPNb, and OPNc, as well as empty vector controls. PC-3 cells overexpressing each construct were analyzed for in vivo tumor growth and in relation to different aspects mimicking tumor progression, such as cell proliferation, migration, invasion, and soft agar colony formation.
  
  
  RESULTS
  OPN-SI are overexpressed in PCa as compared to non-tumoral prostate cell lines. OPNc and OPNb overexpressing cells significantly activated enhanced xenograft tumor growth and PC-3 proliferation, migration, invasion, and soft agar colony formation, as well as the expression of MMP-2, MMP-9, and VEGF. These isoforms also support sustained proliferative survival. We found that both OPNc and OPNb pro-tumorigenic roles are mainly mediated through PI3K signaling. Inhibition of this pathway by using LY294002 specifically inhibited tumor progression features evoked by OPNc and OPNb overexpression.
  
  
  CONCLUSIONS
  Our data provide evidence that both OPNc and OPNb splicing isoforms promote distinct aspects of PCa progression by inducing PI3K signaling. These data give support to strategies aiming to downregulate OPNc and OPNb expression as an approach to inhibit PCa progression.
authors.affiliation: Coordenação de Pesquisa, Programa de Medicina Experimental, Instituto Nacional de Câncer, Rio de Janeiro, RJ, Brazil.
authors.forename: Tatiana M
authors.initials: TM
authors.lastname: Tilli
authors.forename: Kivvi D
authors.initials: KD
authors.lastname: Mello
authors.forename: Luciana B
authors.initials: LB
authors.lastname: Ferreira
authors.forename: Aline R
authors.initials: AR
authors.lastname: Matos
authors.forename: Maria Thereza S
authors.initials: MT
authors.lastname: Accioly
authors.forename: Paulo A S
authors.initials: PA
authors.lastname: Faria
authors.forename: Akeila
authors.initials: A
authors.lastname: Bellahcène
authors.forename: Vincent
authors.initials: V
authors.lastname: Castronovo
authors.forename: Etel R
authors.initials: ER
authors.lastname: Gimba
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D018450:Disease Progression; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009025:Morpholines / Q000494:pharmacology; D053495:Osteopontin / Q000235:genetics* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D019394:Ki-67 Antigen; D009025:Morpholines; D053495:Osteopontin; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D020033:Protein Isoforms; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one