Radiolabeling and in vitro evaluation of (67)Ga-NOTA-modular nanotransporter--a potential Auger electron emitting EGFR-targeted radiotherapeutic.
BACKGROUND
Modular nanotransporters (MNTs) are vehicles designed to transport drugs from the cell surface via receptor-mediated endocytosis and endosomal escape to nucleus. Hence their conjugation to Auger electron emitters, can cause severe cell killing, by nuclear localization. Herein we evaluate the use of MNT as a platform for targeted radiotherapy with (67)Ga.


METHODS
EGF was the targeting ligand on the MNT, and NOTA was selected for its radiolabeling with (67)Ga. In the radiolabeling study we dealt with the precipitation of MNT (pI 5.7) at the labeling pH (4.5-5.5) of (67)Ga. Cellular and nuclei uptake of (67)Ga-NOTA-MNT by the A431 cell line was determined. Its specific cytotoxicity was compared to that of (67)Ga-EDTA, (67)Ga-NOTA-BSA and (67)Ga-NOTA-hEGF, in A431 and U87MGWTT, cell lines, by clonogenic assay. Dosimetry studies were also performed.


RESULTS
(67)Ga-NOTA-MNT was produced with 90% yield and specific activity of 25.6mCi/mg. The in vitro kinetics revealed an increased uptake over 24h. 55% of the internalized radioactivity was detected in the nuclei at 1h. The cytotoxicity of (67)Ga-NOTA-MNT on A431 cell line was 17 and 385-fold higher when compared to non-specific (67)Ga-NOTA-BSA and (67)Ga-EDTA. While its cytotoxic potency was 13 and 72-fold higher when compared to (67)Ga-NOTA-hEGF in the A431 and the U87MGWTT cell lines, respectively, validating its nuclear localization. The absorbed dose, for 63% cell killing, was 8Gy, confirming the high specific index of (67)Ga.


CONCLUSIONS
These results demonstrate the feasibility of using MNT as a platform for single cell kill targeted radiotherapy by Auger electron emitters.
Department of Radiology, Duke University Medical Center, Durham, NC, USA.
Eftychia
E
Koumarianou
Laboratory of Molecular Genetics of Intracellular Transport, Institute of Gene Biology, Moscow, Russia; Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
Tatiana A
TA
Slastnikova
Department of Radiology, Duke University Medical Center, Durham, NC, USA.
Marek
M
Pruszynski
Laboratory of Molecular Genetics of Intracellular Transport, Institute of Gene Biology, Moscow, Russia; Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
Andrey A
AA
Rosenkranz
Department of Radiology, Duke University Medical Center, Durham, NC, USA.
Ganesan
G
Vaidyanathan
Laboratory of Molecular Genetics of Intracellular Transport, Institute of Gene Biology, Moscow, Russia; Department of Biophysics, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.
Alexander S
AS
Sobolev
Department of Radiology, Duke University Medical Center, Durham, NC, USA; Departments of Biomedical Engineering and Radiation Oncology, Duke University, Durham, NC, USA. Electronic address: zalut001@mc.duke.edu.
Michael R
MR
Zalutsky
D001692:Biological Transport; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D004583:Electrons; D066246:ErbB Receptors / Q000378:metabolism*; D005710:Gallium Radioisotopes / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000627:therapeutic use*; D006801:Humans; D017879:Isothiocyanates / Q000737:chemistry / Q000627:therapeutic use*; D007553:Isotope Labeling; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism*; D021381:Protein Transport; D011874:Radiometry; D011878:Radiotherapy / Q000379:methods*
D005710:Gallium Radioisotopes; D006571:Heterocyclic Compounds; D017879:Isothiocyanates; D010455:Peptides; C082060:2-(4-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid; D066246:ErbB Receptors
(67)Ga; Auger electron emitter; EGFR; Modular nanotransporter; Radionuclide therapy