title: Caveolin-1 Dependent Endocytosis Enhances the Chemosensitivity of HER-2 Positive Breast Cancer Cells to Trastuzumab Emtansine (T-DM1).
abstract: The humanized monoclonal antibody-drug conjugate trastuzumab emtansine (T-DM1, Kadcyla) has been approved by the U.S. FDA to treat human epidermal growth factor receptor 2 (HER-2)-positive metastatic breast cancer. Despite its effectiveness in most patients, some are initially resistant or develop resistance. No biomarker of drug resistance to T-DM1 has been identified. Antibody-drug efficacy is associated with antibody internalization in the cell; therefore, cellular sensitivity of cells to the drug may be linked to cellular vesicle trafficking systems. Caveolin-1 is a 22 KD protein required for caveolae formation and endocytic membrane transport. In this study, the relationship between caveolin-1 expression and the chemosensitivity of HER-2-positive breast cancer cells to T-DM1 was investigated. Samples from 32 human breast cancer biopsy and normal tissue specimens were evaluated immunohistochemically for caveolin-1 expression. Caveolin-1 was shown to be expressed in 68% (22/32) of the breast cancer specimens. In addition, eight (72.7%, 8/11) HER-2 positive breast cancer specimens had a higher caveolin-1 expression than normal tissues. HER-2-positive BT-474 and SKBR-3 breast cancer cells that express low and moderate levels of caveolin-1, respectively, were treated with trastuzumab or its conjugate T-DM1. Cell viability and molecular localizations of caveolin-1, antibody and its conjugate were examined. Confocal microscopy showed that T-DM1 and caveolin-1 colocalized in SKBR-3 cells, which also were five times more sensitive to the conjugate in terms of cell survival than BT-474 cells, although T-DM1 also showed improved drug efficacy in BT-474 cells than trastuzumab treatment. Caveolin-1 expression in these lines was manipulated by transfection of GFP-tagged caveolin-1 or caveolin-1 siRNA. BT-474 cells overexpressing caveolin-1 were more sensitive to T-DM1 treatment than mock-transfected cells, whereas the siRNA-transfected SKBR-3 cells had decreased sensitivity to T-DM1 than mock-transfected SKBR-3 cells. The expression of caveolin-1 could mediate endocytosis and promote the internalization of T-DM1 into HER-2 positive cancer cells. Thus, caveolin-1 protein may be an effective predictor for determining the outcome of T-DM1 treatment in breast cancer patients.
authors.affiliation: Department of Surgery, Cheng-Ching General Hospital, Chungkang Branch, Taichung, Taiwan.
authors.forename: Yuan-Chiang
authors.initials: YC
authors.lastname: Chung
authors.affiliation: Department of Pathology, Cheng-Ching General Hospital, Chungkang Branch, Taichung, Taiwan.
authors.forename: Jang-Fang
authors.initials: JF
authors.lastname: Kuo
authors.affiliation: Department of Surgery, Cheng-Ching General Hospital, Chungkang Branch, Taichung, Taiwan; Department of Life Science, Tunghai University, Taichung, Taiwan.
authors.forename: Wan-Chen
authors.initials: WC
authors.lastname: Wei
authors.affiliation: Department of Surgery, Cheng-Ching General Hospital, Chungkang Branch, Taichung, Taiwan.
authors.forename: King-Jen
authors.initials: KJ
authors.lastname: Chang
authors.affiliation: Department of Life Science, Tunghai University, Taichung, Taiwan.
authors.forename: Wei-Ting
authors.initials: WT
authors.lastname: Chao
mesh_terms: D000080044:Ado-Trastuzumab Emtansine; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D051242:Caveolin 1 / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D008453:Maytansine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008875:Middle Aged; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D000068878:Trastuzumab
chemical_list: D000080044:Ado-Trastuzumab Emtansine; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D051242:Caveolin 1; D008453:Maytansine; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C495540:CAV1 protein, human; C508053:ERBB2 protein, human