Rosenkranz AA, Vaidyanathan G, Pozzi OR, Lunin VG, Zalutsky MR, Sobolev AS. Engineered modular recombinant transporters: application of new platform for targeted radiotherapeutic agents to alpha-particle emitting 211 At.
Int J Radiat Oncol Biol Phys 2008;
72:193-200. [PMID:
18722270 DOI:
10.1016/j.ijrobp.2008.05.055]
[Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 04/16/2008] [Accepted: 05/23/2008] [Indexed: 10/21/2022]
Abstract
PURPOSE
To generate and evaluate a modular recombinant transporter (MRT) for targeting 211 At to cancer cells overexpressing the epidermal growth factor receptor (EGFR).
METHODS AND MATERIALS
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.
CONCLUSION
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.
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