title: Imaging biomarkers predict response to anti-HER2 (ErbB2) therapy in preclinical models of breast cancer.
abstract: OBJECTIVE
  To evaluate noninvasive imaging methods as predictive biomarkers of response to trastuzumab in mouse models of HER2-overexpressing breast cancer. The correlation between tumor regression and molecular imaging of apoptosis, glucose metabolism, and cellular proliferation was evaluated longitudinally in responding and nonresponding tumor-bearing cohorts.
  
  
  METHODS
  Mammary tumors from MMTV/HER2 transgenic female mice were transplanted into syngeneic female mice. BT474 human breast carcinoma cell line xenografts were grown in athymic nude mice. Tumor cell apoptosis (NIR700-Annexin V accumulation), glucose metabolism [2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography ([18F]FDG-PET)], and proliferation [3'-[18F]fluoro-3'-deoxythymidine-PET ([18F]FLT-PET)] were evaluated throughout a biweekly trastuzumab regimen. Imaging metrics were validated by direct measurement of tumor size and immunohistochemical analysis of cleaved caspase-3, phosphorylated AKT, and Ki67.
  
  
  RESULTS
  NIR700-Annexin V accumulated significantly in trastuzumab-treated MMTV/HER2 and BT474 tumors that ultimately regressed but not in nonresponding or vehicle-treated tumors. Uptake of [18F]FDG was not affected by trastuzumab treatment in MMTV/HER2 or BT474 tumors. [18F]FLT-PET imaging predicted trastuzumab response in BT474 tumors but not in MMTV/HER2 tumors, which exhibited modest uptake of [18F]FLT. Close agreement was observed between imaging metrics and immunohistochemical analysis.
  
  
  CONCLUSIONS
  Molecular imaging of apoptosis accurately predicts trastuzumab-induced regression of HER2+ tumors and may warrant clinical exploration to predict early response to neoadjuvant trastuzumab. Trastuzumab does not seem to alter glucose metabolism substantially enough to afford [18F]FDG-PET significant predictive value in this setting. Although promising in one preclinical model, further studies are required to determine the overall value of [18F]FLT-PET as a biomarker of response to trastuzumab in HER2+ breast cancer.
authors: Vanderbilt University Institute of Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
authors: Chirayu
authors: C
authors: Shah
authors: Todd W
authors: TW
authors: Miller
authors: Shelby K
authors: SK
authors: Wyatt
authors: Eliot T
authors: ET
authors: McKinley
authors: Maria Graciela
authors: MG
authors: Olivares
authors: Violeta
authors: V
authors: Sanchez
authors: Donald D
authors: DD
authors: Nolting
authors: Jason R
authors: JR
authors: Buck
authors: Ping
authors: P
authors: Zhao
authors: M Sib
authors: MS
authors: Ansari
authors: Ronald M
authors: RM
authors: Baldwin
authors: John C
authors: JC
authors: Gore
authors: Rachel
authors: R
authors: Schiff
authors: Carlos L
authors: CL
authors: Arteaga
authors: H Charles
authors: HC
authors: Manning
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003952:Diagnostic Imaging / Q000379:methods*; D015224:Dideoxynucleosides; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D008822:Mice, Transgenic; D049268:Positron-Emission Tomography; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology; D015203:Reproducibility of Results; D000068878:Trastuzumab; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D015224:Dideoxynucleosides; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D005947:Glucose; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab