title: Expression of LINE-1 retrotransposons in human breast cancer.
abstract: BACKGROUND
  Several diseases have been linked to the insertion of human LINE-1 retrotransposons (L1Hs) into structural genes. Recently, the element has been shown to be expressed in a variety of adult and pediatric germ cell cancers, leading to speculation that L1Hs-induced insertion mutations may play a role in the etiology of some neoplasias.
  
  
  METHODS
  An L1Hs-encoded protein (p40) was assayed in breast cancer cell lines by Western blotting and in solid tumors by immunohistochemical staining and Western blotting.
  
  
  RESULTS
  L1Hs retrotransposons are expressed in a significant number of human breast cancers: expression was detected in 7 of 8 malignant cell lines and in 9 of 12 primary infiltrating ductal carcinomas. No expression was detected in two nonmalignant breast epithelial cell lines, five malignant B- or T-cell lines, tissue from a normal breast, a primary breast sarcoma, or a primary medullary carcinoma of the breast.
  
  
  CONCLUSIONS
  These results raise the possibility that L1Hs expression may contribute to the origin or progression of some breast cancers.
authors.affiliation: Department of Cellular Pathology, Armed Forces Institute of Pathology, Washington, DC 20306-6000.
authors.forename: G L
authors.initials: GL
authors.lastname: Bratthauer
authors.forename: R D
authors.initials: RD
authors.lastname: Cardiff
authors.forename: T G
authors.initials: TG
authors.lastname: Fanning
mesh_terms: D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000235:genetics*; D002277:Carcinoma / Q000235:genetics; D018270:Carcinoma, Ductal, Breast / Q000235:genetics; D018276:Carcinoma, Medullary / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins; D015972:Gene Expression Regulation, Neoplastic; D052138:Genes, Neoplasm / Q000235:genetics*; D006801:Humans; D016366:Open Reading Frames / Q000235:genetics*; D014176:Protein Biosynthesis; D011506:Proteins / Q000032:analysis / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D012509:Sarcoma / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D011506:Proteins; C077214:L1Hs-encoded protein p40, human