Imaging of HER2/neu expression in BT-474 human breast cancer xenografts in athymic mice using [(99m)Tc]-HYNIC-trastuzumab (Herceptin) Fab fragments

Nucl Med Commun. 2005 May;26(5):427-32. doi: 10.1097/00006231-200505000-00006.


Objective: To evaluate the ability of trastuzumab (Herceptin) Fab, labelled with (99m)Tc through introduced hydrazinenicotinamide (HYNIC) functionalities, to image HER2/neu-overexpressing human breast cancer xenografts in athymic mice.

Methods: Fab fragments were produced by immobilized papain digestion of trastuzumab immunoglobulin G (IgG), followed by purification by ultrafiltration. The immunoreactivity of trastuzumab Fab was evaluated by receptor-binding assays against HER2/neu-positive SK-BR-3 human breast cancer cells. Trastuzumab Fab fragments were labelled with (99m)Tc following modification with HYNIC N-hydroxysuccinimide ester. Biodistribution and tumour imaging studies were performed in athymic mice bearing subcutaneous HER2/neu-overexpressing BT-474 human breast cancer xenografts following intravenous injection of 1.1 or 25 MBq of [(99m)Tc]-trastuzumab Fab (30 microg), respectively. The specificity of tumour uptake was assessed by comparison with that of [(99m)Tc]-labelled irrelevant anti-CD33 HuM195 Fab.

Results: Trastuzumab Fab was pure and exhibited preserved immunoreactivity towards SK-BR-3 cells (K(d) = 1.6 x 10(-8) M). Modification with HYNIC diminished its receptor-binding affinity fourfold. [(99m)Tc]-trastuzumab Fab localized avidly and specifically in BT-474 xenografts, achieving a tumour uptake of 10.7% of the injected dose (ID) per gram and a tumour to blood (T/B) ratio of 3 : 1 at 24 h. The tumour uptake and T/B ratio for [(99m)Tc]-trastuzumab Fab were significantly higher than those for control [(99m)Tc]-HuM195 Fab (2.6% ID x g(-1) and 0.9 : 1, respectively; P<0.05). Tumours were imaged as early as 2 h post-injection of [(99m)Tc]-trastuzumab Fab, but were more clearly visualized at 6 and 24 h post-injection.

Conclusions: [(99m)Tc]-HYNIC-trastuzumab Fab localized specifically in HER2/neu-overexpressing human breast cancer xenografts in athymic mice, allowing imaging of the tumours within the useful lifetime of the radionuclide.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents / pharmacology
  • Binding, Competitive
  • Breast Neoplasms / diagnostic imaging
  • Breast Neoplasms / pathology*
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Immunoglobulin Fab Fragments / chemistry
  • Immunoglobulin Fragments / chemistry*
  • Immunoglobulin G / chemistry
  • Kinetics
  • Mice
  • Mice, Nude
  • Neoplasm Transplantation
  • Organotechnetium Compounds / pharmacology
  • Radiography
  • Radiopharmaceuticals
  • Receptor, ErbB-2 / biosynthesis*
  • Technetium / pharmacology
  • Time Factors
  • Tissue Distribution
  • Trastuzumab


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • Immunoglobulin Fab Fragments
  • Immunoglobulin Fragments
  • Immunoglobulin G
  • Organotechnetium Compounds
  • Radiopharmaceuticals
  • Technetium
  • Receptor, ErbB-2
  • Trastuzumab