title: Characterization of low molecular weight protein tyrosine phosphatase isoforms in human breast cancer epithelial cell lines.
abstract: BACKGROUND
  Low molecular weight protein tyrosine phosphatase (LMW-PTP) is a polymorphic protein with two major isoforms whose role in tumorigenesis is currently controversial.
  
  
  METHODS
  We characterized LMW-PTP genotype, isoform expression and activity in six different human breast cancer epithelial cell lines (ZR75, MDA-MB-231, MDA-MB-231BO, MCF7, MDA-MB-231BO2, MDA-MB-435) and compared them with MCF10A, a normal breast epithelial cell line.
  
  
  RESULTS
  mRNA expression of the slow isoform was increased in almost all breast cancer cell lines and that of the fast isoform was reduced (p<0.05) in all breast cancer cell lines. Regarding enzymatic activity, only MCF7 had significantly lower (p<0.05) LMW-PTP activity compared to MCF10A.
  
  
  CONCLUSIONS
  Since these are novel and previously unreported findings, we propose that the differential expression of LMW-PTP fast and slow isoforms suggests their opposite roles in the tumorigenic process, with the fast isoform being anti-oncogenic and the slow isoform being oncogenic.
authors: Genetics Laboratory, Lisbon Medical School, Edificio Egas Moniz, P1C, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal.
authors: Irina
authors: I
authors: Alho
authors: Luís
authors: L
authors: Costa
authors: Manuel
authors: M
authors: Bicho
authors: Constança
authors: C
authors: Coelho
mesh_terms: D015153:Blotting, Western; D001940:Breast / Q000166:cytology / Q000201:enzymology*; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D006801:Humans; D008970:Molecular Weight; D010766:Phosphorylation; D020033:Protein Isoforms; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; C490429:ACP1 protein, human; D017027:Protein Tyrosine Phosphatases
keywords: LMW-PTP isoforms; Protein tyrosine phosphorylation; enzymatic activity; genotype; mRNA expression