Engineered modular recombinant transporters: application of new platform for targeted radiotherapeutic agents to alpha-particle emitting 211 At.
OBJECTIVE
To generate and evaluate a modular recombinant transporter (MRT) for targeting 211 At to cancer cells overexpressing the epidermal growth factor receptor (EGFR).


METHODS
The MRT was produced with four functional modules: (1) human epidermal growth factor as the internalizable ligand, (2) the optimized nuclear localization sequence of simian vacuolating virus 40 (SV40) large T-antigen, (3) a translocation domain of diphtheria toxin as an endosomolytic module, and (4) the Escherichia coli hemoglobin-like protein (HMP) as a carrier module. MRT was labeled using N-succinimidyl 3-[211 At]astato-5-guanidinomethylbenzoate (SAGMB), its 125 I analogue SGMIB, or with 131 I using Iodogen. Binding, internalization, and clonogenic assays were performed with EGFR-expressing A431, D247 MG, and U87MG.wtEGFR human cancer cell lines.


RESULTS
The affinity of SGMIB-MRT binding to A431 cells, determined by Scatchard analysis, was 22 nM, comparable to that measured before labeling. The binding of SGMIB-MRT and its internalization by A431 cancer cells was 96% and 99% EGFR specific, respectively. Paired label assays demonstrated that compared with Iodogen-labeled MRT, SGMIB-MRT and SAGMB-MRT exhibited more than threefold greater peak levels and durations of intracellular retention of activity. SAGMB-MRT was 10-20 times more cytotoxic than [211 At]astatide for all three cell lines.


CONCLUSIONS
The results of this study have demonstrated the initial proof of principle for the MRT approach for designing targeted alpha-particle emitting radiotherapeutic agents. The high cytotoxicity of SAGMB-MRT for cancer cells overexpressing EGFR suggests that this 211 At-labeled conjugate has promise for the treatment of malignancies, such as glioma, which overexpress this receptor.
Rosenkranz
Andrey A
AA
Laboratory of Molecular Genetics of Intracellular Transport, Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia.
Vaidyanathan
Ganesan
G
Pozzi
Oscar R
OR
Lunin
Vladimir G
VG
Zalutsky
Michael R
MR
Sobolev
Alexander S
AS
D000512:Alpha Particles / Q000627:therapeutic use; D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism; D001246:Astatine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001565:Benzoates / Q000493:pharmacokinetics / Q000627:therapeutic use; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000532:radiotherapy; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism / Q000528:radiation effects*; D016001:Confidence Intervals; D004093:Dihydropteridine Reductase / Q000493:pharmacokinetics; D004167:Diphtheria Toxin / Q000493:pharmacokinetics; D004337:Drug Carriers / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011992:Endosomes / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000493:pharmacokinetics; D005909:Glioblastoma / Q000378:metabolism / Q000532:radiotherapy; D019791:Guanidine / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000627:therapeutic use; D006146:Guanidines / Q000493:pharmacokinetics / Q000627:therapeutic use; D006420:Hemeproteins / Q000493:pharmacokinetics; D006801:Humans; D009247:NADH, NADPH Oxidoreductases / Q000493:pharmacokinetics; D016499:Radioimmunotherapy / Q000379:methods
D000952:Antigens, Polyomavirus Transforming; D001565:Benzoates; D004167:Diphtheria Toxin; D004337:Drug Carriers; D029968:Escherichia coli Proteins; D006146:Guanidines; D006420:Hemeproteins; C532020:N-succinimidyl 3-astato-5-guanidinomethylbenzoate; C438937:N-succinimidyl 4-guanidinomethyl-3-iodobenzoate; D004815:Epidermal Growth Factor; D004093:Dihydropteridine Reductase; C076538:hmp protein, E coli; D009247:NADH, NADPH Oxidoreductases; D066246:ErbB Receptors; D019791:Guanidine; D001246:Astatine