title: Proteomic study reveals that proteins involved in metabolic and detoxification pathways are highly expressed in HER-2/neu-positive breast cancer.
abstract: The receptor tyrosine kinase ErbB2 (HER-2/neu) is overexpressed in up to 30% of breast cancers and is associated with poor prognosis and an increased likelihood of metastasis especially in node-positive tumors. In this proteomic study, to identify the proteins that are associated with the aggressive phenotype of HER-2/neu-positive breast cancer, tumor cells from both HER-2/neu-positive and -negative tumors were procured by laser capture microdissection. Differentially expressed proteins in the two subsets of tumors were identified by two-dimensional electrophoresis and MALDI-TOF/TOF MS/MS. We found differential expression of several key cell cycle modulators, which were linked with increased proliferation of the HER-2/neu-overexpressing cells. Nine proteins involved in glycolysis (triose-phosphate isomerase (TPI), phosphoglycerate kinase 1 (PGK1), and enolase 1 (ENO1)), lipid synthesis (fatty acid synthase (FASN)), stress-mediated chaperonage (heat shock protein 27 (Hsp27)), and antioxidant and detoxification pathways (haptoglobin, aldo-keto reductase (AKR), glyoxalase I (GLO), and prolyl-4-hydrolase beta-isoform (P4HB)) were found to be up-regulated in HER-2/neu-positive breast tumors. HER-2/neu-dependent differential expression of PGK1, FASN, Hsp27, and GLO was further validated in four breast cancer cell lines and 12 breast tumors by immunoblotting and confirmed by partially switching off the HER-2/neu signaling in the high HER-2/neu-expressing SKBr3 cell line with Herceptin treatment. Statistical correlations of these protein expressions with HER-2/neu status were further verified by immunohistochemistry on a tissue microarray comprising 97 breast tumors. Our findings suggest that HER-2/neu signaling may result, directly or indirectly, in enhanced activation of various metabolic, stress-responsive, antioxidative, and detoxification processes within the breast tumor microenvironment. We hypothesize that these identified changes in the cellular proteome are likely to drive cell proliferation and tissue invasion and that the key cell cycle modulators involved, when uncovered by future research, would serve as naturally useful targets for the development of therapeutic strategies to negate the metastatic potential of HER-2/neu-positive breast tumors.
authors.affiliation: Department of Laboratory Medicine, National University Hospital, 5 Lower Kent Ridge Road, Singapore 119074.
authors.forename: DaoHai
authors.initials: D
authors.lastname: Zhang
authors.forename: Lee Kian
authors.initials: LK
authors.lastname: Tai
authors.forename: Lee Lee
authors.initials: LL
authors.lastname: Wong
authors.forename: Lily-Lily
authors.initials: LL
authors.lastname: Chiu
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Sethi
authors.forename: Evelyn S C
authors.initials: ES
authors.lastname: Koay
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D064429:Fatty Acid Synthases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018734:Genes, erbB-2 / Q000235:genetics / Q000502:physiology*; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008658:Inactivation, Metabolic; D007791:Lactoylglutathione Lyase / Q000378:metabolism; D046228:Microarray Analysis; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D010735:Phosphoglycerate Kinase / Q000378:metabolism; D020543:Proteome / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D040901:Proteomics; D015398:Signal Transduction; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D020543:Proteome; D064429:Fatty Acid Synthases; D010735:Phosphoglycerate Kinase; D007791:Lactoylglutathione Lyase; D000068878:Trastuzumab