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Endocrine Abstracts (2016) 47 OC25 | DOI: 10.1530/endoabs.47.OC25

1Department of Imaging Chemistry and Biology, King’s College London, London, UK; 2Department of Nuclear Medicine, Guy’s & St Thomas’ NHS Foundation Trust, London, UK.


Background: Despite its desirable half-life and high-energy Auger electrons, 67Ga has been neglected as a therapeutic Auger electron emitter, due in part to lack of suitable chelators and targeting molecules.

Objective: Here, 67Ga is compared with Auger electron emitter 111In as a therapeutic radionuclide in prostate cancer and breast cancer cell lines.

Method: Plasmid pBR322 studies allowed direct comparison between 67Ga and 111In (1 MBq) in causing DNA damage, including the effect of chelators EDTA and DTPA and the effects of free radical scavenger DMSO. The cytotoxicity of internalized (using oxine) and non-internalized 67Ga and 111In was measured in cancer cells after a one-hour incubation using cell viability and clonogenic studies.

Results: Plasmid DNA damage caused by 67Ga was comparable to 111In and was reduced in the presence of EDTA, DTPA and DMSO. The A50 values (internalized activity of oxine complexes per cell required to kill 50% of cells) as determined by trypan blue staining was 1.0 Bq/cell for both 67Ga and 111In; the A50 values determined by clonogenic assay were 0.7 Bq/cell and 0.3 Bq/cell for 111In and 67Ga respectively. At the concentrations required achieving these uptake levels, non-internalized 67Ga and 111In caused no cellular toxicity.

Conclusion: 67Ga causes as much damage as 111In to plasmid DNA in solution and is more toxic than 111In at equivalent internalized activity per cell in the cell types studied. 67Ga therefore deserves further evaluation for radionuclide therapy.

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