title: Upregulation of CPE promotes cell proliferation and tumorigenicity in colorectal cancer.
abstract: BACKGROUND
  Colorectal cancer (CRC) is one of the most common cancers worldwide and a leading cause of cancer related death. Although the mortality rate of CRC is decreasing, finding novel targets for its therapy remains urgent. Carboxypeptidase E (CPE), a member of the pro-protein convertases, which are involved in the maturation of protein precursors, has recently been reported as elevated in many types of cancer. However, its role and mechanisms in tumor progression are poorly understood.
  
  
  METHODS
  In the present study, we investigated expression of CPE in CRC cell lines and tumor tissues using Western blot and real-time qRT-PCR. Plasmids for overexpression and depletion of CPE were constructed and analyzed by Western blot, MTT and colony formation assays and bromodeoxyuridine incorporation assays. The relative expression of p21, p27, and cyclin D1 were analyzed by Real-time qRT-PCR in the indicated cells.
  
  
  RESULTS
  Our study showed that CPE was significantly upregulated in CRC cell lines and tumor tissues. MTT and colony formation assays indicated that overexpression of CPE enhanced cell growth rates. BrdU incorporation and flow-cytometry assays showed that ectopic expression of CPE increased the S-phase fraction cells. Soft agar assay proved enhanced tumorigenicity activity in CPE over-expressing CRC cells. Further studies of the molecular mechanisms of CPE indicated that is promoted cell proliferation and tumorigenicity through downregulation of p21 and p27, and upregulation of cyclin D1.
  
  
  CONCLUSIONS
  Taken together, these data suggest that CPE plays an important role in cell cycle regulation and tumorigenicity, and may serve as a potential target for CRC therapeutics.
authors.affiliation: Department of General Surgery, Zengcheng People's Hospital, (BoJi-Affiliated Hospital of Sun Yat-Sen University), Zengcheng 511300, China. zxcheng1974@163.com.
authors.forename: Xing-Hua
authors.initials: XH
authors.lastname: Liang
authors.forename: Ling-Ling
authors.initials: LL
authors.lastname: Li
authors.forename: Geng-Gang
authors.initials: GG
authors.lastname: Wu
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Xie
authors.forename: Guang-Xian
authors.initials: GX
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Hai-Feng
authors.initials: HF
authors.lastname: Yang
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Liu
authors.forename: Wen-Hong
authors.initials: WH
authors.lastname: Li
authors.forename: Wen-Guang
authors.initials: WG
authors.lastname: He
authors.forename: Yan-Nian
authors.initials: YN
authors.lastname: Huang
authors.forename: Xian-Cheng
authors.initials: XC
authors.lastname: Zeng
mesh_terms: D043423:Carboxypeptidase H / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D016196:S Phase / Q000235:genetics; D015854:Up-Regulation
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D043423:Carboxypeptidase H