title: Lactate dehydrogenase isoenzymes 1 and 5: differential expression by neoplastic and stromal cells in non-small cell lung cancer and other epithelial malignant tumors.
abstract: OBJECTIVE
  Lactate dehydrogenase-5 (LDH-5), an isoenzyme composed of 4 M-polypeptide chains, catalyzes the conversion of pyruvate to lactate with an unparalleled efficiency (anaerobic oxidation), but this function of LDH gradually fades away as the number of H over M chains increases. Thus, LDH-1, another component isoenzyme made up of 4 H-polypeptide chains, favors aerobic oxidation of pyruvate by pyruvate dehydrogenase.
  
  
  METHODS
  Using immunohistochemistry in this study, we explored the expression of LDH-1 and LDH-5 in a variety of normal and malignant tissues, including lung, breast, endometrium, urinary bladder and large intestine.
  
  
  RESULTS
  LDH-1 was consistently expressed in all living cells, normal and malignant, epithelial and stromal, including endothelium and lymphocytes. In contrast, LDH-5 was expressed preferentially in tumor cells, while normal tissues were devoid of LDH-5 or expressed it only faintly, and the cellular population of the tumor-supporting stroma showed LDH-5 activity in a small percentage of cases. Interestingly, LDH-5-positive stromal cells were associated with hypoxia-inducible factor-1alpha overexpression.
  
  
  CONCLUSIONS
  It is concluded that normal tissues utilize aerobic oxidation as a means of energy production, while tumor cells are turned to anaerobic glycolysis, a phenomenon which is rarely followed by the mesenchymal cells of the tumor-supporting stroma.
authors.affiliation: Department of Radiotherapy/Oncology, Democritus University of Thrace, Alexandroupolis, Greece.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Koukourakis
authors.forename: Alexandra
authors.initials: A
authors.lastname: Giatromanolaki
authors.forename: Efthimios
authors.initials: E
authors.lastname: Sivridis
mesh_terms: D001943:Breast Neoplasms / Q000201:enzymology; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis*; D007770:L-Lactate Dehydrogenase / Q000032:analysis*; D000080864:Lactate Dehydrogenase 5; D008175:Lung Neoplasms / Q000201:enzymology*; D009375:Neoplasms, Glandular and Epithelial / Q000201:enzymology*; D017154:Stromal Cells / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase; D000080864:Lactate Dehydrogenase 5; C409667:lactate dehydrogenase 1