title: Characterization of ductal and lobular breast carcinomas using novel prolactin receptor isoform specific antibodies.
abstract: BACKGROUND
  Prolactin is a polypeptide hormone responsible for proliferation and differentiation of the mammary gland. More recently, prolactin's role in mammary carcinogenesis has been studied with greater interest. Studies from our laboratory and from others have demonstrated that three specific isoforms of the prolactin receptor (PRLR) are expressed in both normal and cancerous breast cells and tissues. Until now, reliable isoform specific antibodies have been lacking. We have prepared and characterized polyclonal antibodies against each of the human PRLR isoforms that can effectively be used to characterize human breast cancers.
  
  
  METHODS
  Rabbits were immunized with synthetic peptides of isoform unique regions and immune sera affinity purified prior to validation by Western blot and immunohistochemical analyses. Sections of ductal and lobular carcinomas were stained with each affinity purified isoform specific antibody to determine expression patterns in breast cancer subclasses.
  
  
  RESULTS
  We show that the rabbit antibodies have high titer and could specifically recognize each isoform of PRLR. Differences in PRLR isoform expression levels were observed and quantified using histosections from xenografts of established human breast cancer cells lines, and ductal and lobular carcinoma human biopsy specimens. In addition, these results were verified by real-time PCR with isoform specific primers. While nearly all tumors contained LF and SF1b, the majority (76%) of ductal carcinoma biopsies expressed SF1a while the majority of lobular carcinomas lacked SF1a staining (72%) and 27% had only low levels of expression.
  
  
  CONCLUSIONS
  Differences in the receptor isoform expression profiles may be critical to understanding the role of PRL in mammary tumorigenesis. Since these antibodies are specifically directed against each PRLR isoform, they are valuable tools for the evaluation of breast cancer PRLR content and have potential clinical importance in treatment of this disease by providing new reagents to study the protein expression of the human PRLR.
authors.affiliation: Mammary Biology and Tumorigenesis Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. eg20e@nih.gov
authors.forename: Erika
authors.initials: E
authors.lastname: Ginsburg
authors.forename: Stefanie
authors.initials: S
authors.lastname: Alexander
authors.forename: Sarah
authors.initials: S
authors.lastname: Lieber
authors.forename: Sarah
authors.initials: S
authors.lastname: Tarplin
authors.forename: Luwanda
authors.initials: L
authors.lastname: Jenkins
authors.forename: Linda
authors.initials: L
authors.lastname: Pang
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Heger
authors.forename: Paul
authors.initials: P
authors.lastname: Goldsmith
authors.forename: Barbara K
authors.initials: BK
authors.lastname: Vonderhaar
mesh_terms: D000818:Animals; D000906:Antibodies; D000918:Antibody Specificity; D001706:Biopsy; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D016466:CHO Cells; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism*; D018275:Carcinoma, Lobular / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008819:Mice, Nude; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D011981:Receptors, Prolactin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D000906:Antibodies; D020033:Protein Isoforms; D012333:RNA, Messenger; D011981:Receptors, Prolactin