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|Title:||Synthesis and in vitro evaluation of 225Ac-DOTA-SubstanceP for targeted alpha therapy of glioblastoma multiforme|
|Authors:||MAJKOWSKA AGNIESZKA; BRUCHERTSEIFER Frank; WEIS Mirjam; BONELLI Milton; LAURENZA M; APOSTOLIDIS Christos; MORGENSTERN Alfred|
|Citation:||EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING vol. 39 no. Supplement 2 p. 157|
|Type:||Contributions to Conferences|
|Abstract:||Aim The life expectancy of patients diagnosed with glioblastoma multiforme (GBM) is 12 to 15 months despite aggressive surgery, radiation therapy and chemotherapy. According to the cancer stem cell hypothesis, malignant gliomas arise from mutated, developmentally arrested multipotent progenitor cells ("glioma stem cells") that sustain tumor growth and are intrinsically resistant to radio- and chemotherapy. Targeted alpha therapy has been shown to overcome chemo- and radioresistance in vitro and thus presents a promising approach for therapy of GBM. The neuropeptide SubstanceP is the physiological ligand of the neurokinin1 (NK1) receptor consistently overexpressed by glioblastoma cells. The aim of this study is to develop a protocol for the synthesis of DOTA-SubstanceP labeled with the alpha emitter 225Ac and to evaluate the binding affinity and cytotoxicity of 225Ac-DOTA-SubstanceP (225Ac-DOTA-SP) towards GBM cells and GBM stem cells. Materials and methods Synthesis of 225Ac-DOTA-SP was investigated in the temperature range from 60 - 95° C in various buffer systems with and without addition of radioprotectants. Four human GBM cell lines (T 98G, LN 319, U 87 MG, U 138 MG) as well as GBM stem cells derived from adult human GBM bioptic samples were used. Expression of NK1 receptors on the cell lines was confirmed by PCR. The binding affinity of 225Ac-DOTA-SP was determined by saturation binding experiments. To evaluate cytotoxicity 225Ac-DOTA-SP (0.1-100 kBq/ml) was incubated with GBM cells and GBM stem cells for 1-5 days. Cell viability was assayed using the MTS colorimetric assay and the clonogenic assay. Results 225Ac-DOTA-SP could be reliably synthesized with high specific activity (3.7 MBq/nmol), and in high radiochemical purity (> 99%) at 95 °C in 0.1 M TRIS buffer. Binding studies demonstrated high affinity of the radiolabelled peptide in the nanomolar range. Cytotoxicity assays showed a reduction of viability of GBM cells as well as GBM stem cells after incubation with 225Ac-DOTA-SP in a dose dependent manner. Cell viability also decreased with increasing incubation times. Conclusion The protocol developed in this work allows the synthesis of 225Ac-DOTA-SP in high specific activity and purity. 225Ac-DOTA-SP was found to be highly cytotoxic not only towards established GBM cell lines but also to particularly radioresistant GBM stem cells. Targeted alpha therapy with 225Ac-DOTA-SP is a promising approach for treatment of GBM and warrants further investigation in vivo.|
|JRC Institute:||Institute for Transuranium Elements|
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