Preparation and biodistribution of [Ga]-insulin for SPECT purposes

Metabolism of glucose has been an interesting target for tumor imaging for 3 decades. Development of radiolabeled glucose by many research groups in the 1970s and 1980s led to development of the most common PET radiopharmaceutical, F-FDG. Since then, FDG has been used for the detection and staging of several malignancies. Few limitations have been proposed in the last few years in using FDG as a tracer, including natural accumulation of the tracer in the bladder, liver and brain which can limit the detection of malignancies of these regions. It has already been shown insulin stimulates phosphorylation of its own receptor [17, 18] and also phosphorylation of the insulin receptor may be an early step in insulin action which happens in 80% of human cells with some exceptions such as neurons. The idea of detecting FDG consumption in cells indirectly by insulin radiolabeling has come to our interest. Insulin is a peptide pharmaceutical which consists of 51 amino acids which are oriented in two chains (αand β-chain). Insulin has been radiolabeled with many SPECT and PET radionuclides such as Tc [1], I [11, 22] and F [4, 21] for various purposes such as a study of insulin biodistribution in diabetic subjects [4] and overexpression of the insulin receptor on IM-9 lymphoblastoid tumor cell surface [10]. In order to obtain an insulin conjugate for use in diagnostic studies using metallic PET or SPECT radioisotopes, Ga-labeled insulin was prepared for preliminary biodistribution studies, based on our recent Preparation and biodistribution of [Ga]-insulin for SPECT purposes Amir R. Jalilian, Javad Garousi, Ebrahim Gholami, Mehdi Akhlaghi, Fatemeh Bolourinovin, Saeed Rajabifar