Abstract
Auger electron-emitters increasingly attract attention as potential radionuclides for molecular radionuclide therapy in oncology. The radionuclide technetium-99m is widely used for imaging; however, its potential as a therapeutic radionuclide has not yet been fully assessed. We used MDA-MB-231 breast cancer cells engineered to express the human sodium iodide symporter-green fluorescent protein fusion reporter (hNIS-GFP; MDA-MB-231.hNIS-GFP) as a model for controlled cellular radionuclide uptake. Uptake, efflux, and subcellular location of the NIS radiotracer [99mTc]TcO4− were characterised to calculate the nuclear-absorbed dose using Medical Internal Radiation Dose formalism. Radiotoxicity was determined using clonogenic and γ-H2AX assays. The daughter radionuclide technetium-99 or external beam irradiation therapy (EBRT) served as controls. [99mTc]TcO4− in vivo biodistribution in MDA-MB-231.hNIS-GFP tumour-bearing mice was determined by imaging and complemented by ex vivo tissue radioactivity analysis. [99mTc]TcO4− resulted in substantial DNA damage and reduction in the survival fraction (SF) following 24 h incubation in hNIS-expressing cells only. We found that 24,430 decays/cell (30 mBq/cell) were required to achieve SF0.37 (95%-confidence interval = [SF0.31; SF0.43]). Different approaches for determining the subcellular localisation of [99mTc]TcO4− led to SF0.37 nuclear-absorbed doses ranging from 0.33 to 11.7 Gy. In comparison, EBRT of MDA-MB-231.hNIS-GFP cells resulted in an SF0.37 of 2.59 Gy. In vivo retention of [99mTc]TcO4− after 24 h remained high at 28.0% ± 4.5% of the administered activity/gram tissue in MDA-MB-231.hNIS-GFP tumours. [99mTc]TcO4− caused DNA damage and reduced clonogenicity in this model, but only when the radioisotope was taken up into the cells. This data guides the safe use of technetium-99m during imaging and potential future therapeutic applications.
Funder
Engineering and Physical Sciences Research Council
Cancer Research UK
Medical Research Council
Academy of Medical Sciences
Wellcome Trust
Subject
Inorganic Chemistry,Organic Chemistry,Physical and Theoretical Chemistry,Computer Science Applications,Spectroscopy,Molecular Biology,General Medicine,Catalysis
Cited by
4 articles.
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