title: 111In-labeled trastuzumab-modified gold nanoparticles are cytotoxic in vitro to HER2-positive breast cancer cells and arrest tumor growth in vivo in athymic mice after intratumoral injection.
abstract: BACKGROUND
  Gold nanoparticles (AuNP; 30nm) were modified with polyethylene glycol (PEG) chains linked to trastuzumab for binding to HER2-positive breast cancer (BC) cells and diethylenetriaminepentaacetic acid (DTPA) for complexing the Auger electron-emitter,111In (trastuzumab-AuNP-111In). Our objective was to determine the cytotoxicity of trastuzumab-AuNP-111In on HER2-positive BC cells in vitro and evaluate its tumor growth inhibition properties and normal tissue toxicity in vivo following intratumoral (i.t.) injection in mice with s.c. HER2-overexpressing BC xenografts.
  
  
  METHODS
  Binding and internalization of trastuzumab-AuNP-111In or non-targeted AuNP-111In in SK-BR-3 (1-2×106HER2/cell) and MDA-MB-361 (5×105HER2/cell) human BC cells were studied. The surviving fraction (SF) of SK-BR-3 or MDA-MB-361 cells exposed to trastuzumab-AuNP-111In or AuNP-111In was determined. DNA double-strand breaks (DSBs) were assayed by probing for γ-H2AX. Tumor growth was monitored over 70days in CD1 athymic mice with s.c. MDA-MB-361 xenografts after i.t. injection of 10MBq (0.7mg; 2.6×1012AuNP) of trastuzumab-AuNP-111In and normal tissue toxicity was assessed by monitoring body weight, complete blood cell (CBC) counts and serum alanine aminotransferase (ALT) and creatinine (Cr).
  
  
  RESULTS
  Trastuzumab-AuNP-111In was specifically bound by SK-BR-3 and MDA-MB-361 cells. Trastuzumab-AuNP-111In was more efficiently internalized than AuNP-111In and localized to a peri-nuclear region. The SF fraction of SK-BR-3 cells was reduced by 1.8-fold by treatment with 3nM (7MBq/mL) of trastuzumab-AuNP-111In. The SF of MDA-MB-361 cells was reduced by 3.7-fold at 14.4nM (33.6MBq/mL). In comparison, non-targeted AuNP-111In at these concentrations reduced the SF of SK-BR-3 or MDA-MB-361 cells by 1.2-fold (P=0.03) and 1.7-fold (P<0.0001), respectively. DNA DSBs were greater in SK-BR-3 and MDA-MB-361 cells exposed to trastuzumab-AuNP-111In compared to AuNP-111In, but unlabeled trastuzumab-AuNP did not increase DNA DSBs. Local i.t. injection of trastuzumab-AuNP-111In in CD1 athymic mice with s.c. MDA-MB-361 tumors arrested tumor growth for 70days. There was no apparent normal tissue toxicity. The radiation absorbed dose deposited in the tumor by trastuzumab-AuNP-111In was 60.5Gy, while normal organs received <0.9Gy.
  
  
  CONCLUSIONS
  These results are promising for further development of trastuzumab-AuNP-111In as a novel Auger electron-emitting radiation nanomedicine for local treatment of HER2-positive BC.
  
  
  CONCLUSIONS
  A local radiation treatment for HER2-positive BC based on AuNP modified with trastuzumab and labeled with the Auger electron-emitter,111In was developed and shown to arrest tumor growth with no normal tissue toxicity.
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada.
authors: Zhongli
authors: Z
authors: Cai
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada.
authors: Niladri
authors: N
authors: Chattopadhyay
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada.
authors: Kaiyu
authors: K
authors: Yang
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada.
authors: Yongkyu Luke
authors: YL
authors: Kwon
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada.
authors: Simmyung
authors: S
authors: Yook
authors: Department of Radiation Oncology, Erasmus MC Cancer Institute, Rotterdam, The Netherlands.
authors: Jean-Philippe
authors: JP
authors: Pignol
authors: Department of Pharmaceutical Sciences, University of Toronto, Ontario, Canada; Department of Medical Imaging, University of Toronto, Ontario, Canada; Toronto General Research Institute and Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada. Electronic address: raymond.reilly@utoronto.ca.
authors: Raymond M
authors: RM
authors: Reilly
mesh_terms: D000818:Animals; D001692:Biological Transport; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism*; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007205:Indium Radioisotopes / Q000627:therapeutic use*; D015552:Injections, Intralesional; D053768:Metal Nanoparticles / Q000737:chemistry*; D008819:Mice, Nude; D011829:Radiation Dosage; D000068878:Trastuzumab / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism / Q000627:therapeutic use*
chemical_list: D007205:Indium Radioisotopes; D006046:Gold; D066246:ErbB Receptors; D000068878:Trastuzumab
keywords: Auger electrons; Breast cancer; Gold nanoparticles; HER2; Indium-111; Radiotherapy