title: Preclinical Efficacy of Ado-trastuzumab Emtansine in the Brain Microenvironment.
abstract: BACKGROUND
  Central nervous system (CNS) metastases represent a major problem in the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer because of the disappointing efficacy of HER2-targeted therapies against brain lesions. The antibody-drug conjugate ado-trastuzumab emtansine (T-DM1) has shown efficacy in trastuzumab-resistant systemic breast cancer. Here, we tested the hypothesis that T-DM1 could overcome trastuzumab resistance in murine models of brain metastases.
  
  
  METHODS
  We treated female nude mice bearing BT474 or MDA-MB-361 brain metastases (n = 9-11 per group) or cancer cells grown in organotypic brain slice cultures with trastuzumab or T-DM1 at equivalent or equipotent doses. Using intravital imaging, molecular techniques and histological analysis we determined tumor growth, mouse survival, cancer cell apoptosis and proliferation, tumor drug distribution, and HER2 signaling. Data were analyzed with one-way analysis of variance (ANOVA), Kaplan-Meier analysis, and Coefficient of Determination. All statistical tests were two-sided.
  
  
  RESULTS
  T-DM1 delayed the growth of HER2-positive breast cancer brain metastases compared with trastuzumab. These findings were consistent between HER2-driven and PI3K-driven tumors. The activity of T-DM1 resulted in a survival benefit (median survival for BT474 tumors: 28 days for trastuzumab vs 112 days for T-DM1, hazard ratio = 6.2, 95% confidence interval = 6.1 to 85.84, P < .001). No difference in drug distribution or HER2-signaling was revealed between the two groups. However, T-DM1 led to a statistically significant increase in tumor cell apoptosis (one-way ANOVA for ApopTag, P < .001), which was associated with mitotic catastrophe.
  
  
  CONCLUSIONS
  T-DM1 can overcome resistance to trastuzumab therapy in HER2-driven or PI3K-driven breast cancer brain lesions due to the cytotoxicity of the DM1 component. Clinical investigation of T-DM1 for patients with CNS metastases from HER2-positive breast cancer is warranted.
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Vasileios
authors.initials: V
authors.lastname: Askoxylakis
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Gino B
authors.initials: GB
authors.lastname: Ferraro
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: David P
authors.initials: DP
authors.lastname: Kodack
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Mark
authors.initials: M
authors.lastname: Badeaux
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Ram C
authors.initials: RC
authors.lastname: Shankaraiah
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Seano
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Jonas
authors.initials: J
authors.lastname: Kloepper
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Trupti
authors.initials: T
authors.lastname: Vardam
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: John D
authors.initials: JD
authors.lastname: Martin
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Kamila
authors.initials: K
authors.lastname: Naxerova
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Divya
authors.initials: D
authors.lastname: Bezwada
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Qi
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Martin K
authors.initials: MK
authors.lastname: Selig
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Elena
authors.initials: E
authors.lastname: Brachtel
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Dan G
authors.initials: DG
authors.lastname: Duda
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Peigen
authors.initials: P
authors.lastname: Huang
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Dai
authors.initials: D
authors.lastname: Fukumura
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Engelman
authors.affiliation: : Edwin L. Steele Laboratories, Department of Radiation Oncology (VA, GBF, DPK, MB, RCS, GS, JK, TV, JDM, KN, DB, XQ, DGD, PH, DF, RKJ), Department of Pathology (MKS, EB), and Department of Medicine, Cancer Center (JAE), Massachusetts General Hospital and Harvard Medical School, Boston MA. jain@steele.mgh.harvard.edu.
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Jain
mesh_terms: D000080044:Ado-Trastuzumab Emtansine; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000032:analysis*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000737:chemistry / Q000188:drug therapy* / Q000556:secondary*; D001943:Breast Neoplasms / Q000737:chemistry / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D004334:Drug Administration Schedule; D019008:Drug Resistance, Neoplasm; D005260:Female; D020869:Gene Expression Profiling; D053208:Kaplan-Meier Estimate; D008453:Maytansine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D046228:Microarray Analysis; D008854:Microscopy, Electron; D016017:Odds Ratio; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis*; D000068878:Trastuzumab; D023041:Xenograft Model Antitumor Assays
chemical_list: D000080044:Ado-Trastuzumab Emtansine; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D008453:Maytansine; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C508053:ERBB2 protein, human