title: The prolyl oligopeptidase inhibitor SUAM-14746 attenuates the proliferation of human breast cancer cell lines in vitro.
abstract: BACKGROUND
  Prolyl oligopeptidase (POP, EC 3.4.1.26) is a serine peptidase that hydrolyzes post-proline peptide bonds in peptides that are <30 amino acids in length. We previously reported that POP inhibition suppressed the growth of NB-1 human neuroblastomas cells and KATO III human gastric cancer cells. POP activity is commonly elevated in many cancers, which includes breast cancer. However, the effect of POP inhibition as a candidate breast cancer therapy is unknown.
  
  
  METHODS
  The effects of POP inhibition and knockdown on the proliferation of cultured human estrogen receptor-positive (ER+) MCF7 and T47D, and ER-negative (ER-) MDA-MB-231 breast cancer cell lines and the MCF12A non-tumorigenic epithelial cell line were tested by analyzing their influence on cell proliferation (WST-1 assay), cell viability (trypan blue exclusion assay), and cell cycle arrest (cell cycle analysis, cell cycle regulator proteins expression).
  
  
  RESULTS
  POP-specific inhibitors 3-({4-[2-(E)-styrylphenoxy]butanoyl}-L-4-hydroxyprolyl)-thiazolidine (SUAM-14746) and benzyloxycarbonyl-thiopropyl-thioprolinal and RNAi-mediated POP knockdown inhibited the proliferation of MCF7 cells without inducing cell death. SUAM-14746-induced growth inhibition was also observed in T47D and MDA-MB-231 cells, but not in MCF12A cells. This growth inhibition was associated with G1phase arrest; reduced cyclin D1 and D3, cyclin-dependent kinase 4 (CDK4), E2F1, and retinoblastoma protein (pRb) expression; and increased cyclin-dependent kinase inhibitor 1B (p27kip1) expression. Moreover, the SUAM-14746-mediated cell cycle arrest of MCF7 cells was associated with increased pRb2/p130 protein expression and an increase in the number of cells in the quiescent G0state, as defined by low RNA levels.
  
  
  CONCLUSIONS
  SUAM-14746 inhibited breast cancer cell growth in a cytostatic manner without inducing lethality, and POP-specific inhibitors may be an effective treatment against ER+ and ER- breast cancer.
authors.affiliation: Laboratory of Cell Biology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569-1094, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Laboratory of Cell Biology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569-1094, Japan.
authors.forename: Kanayo
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Laboratory of Cell Biology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka, 569-1094, Japan. sakaguti@gly.oups.ac.jp.
authors.forename: Minoru
authors.initials: M
authors.lastname: Sakaguchi
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D056743:Cyclin D3 / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000494:pharmacology; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005260:Female; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects*; D055785:Gene Knockdown Techniques; D006801:Humans; D011392:Proline / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000085822:Prolyl Oligopeptidases; D011480:Protease Inhibitors / Q000627:therapeutic use; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D056286:Retinoblastoma Binding Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D053778:Thiazolidines / Q000494:pharmacology* / Q000627:therapeutic use; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C560755:3-((4-(2-styrylphenoxy)butanoyl)-4-hydroxyprolyl)thiazolidine; C530104:CCND1 protein, human; C534696:CCND3 protein, human; D056743:Cyclin D3; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D011480:Protease Inhibitors; C000606393:RB1 protein, human; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D056286:Retinoblastoma Binding Proteins; D053778:Thiazolidines; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D011392:Proline; D044767:Ubiquitin-Protein Ligases; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D012697:Serine Endopeptidases; C000705287:PREPL protein, human; D000085822:Prolyl Oligopeptidases
keywords: Cell cycle arrest; Human breast cancer cell lines; Prolyl oligopeptidase; Quiescent G0 state; SUAM-14746