Octreotide Labelled Fluorescein Isothiocyanate for Identification of Somatostatin Receptor Subtype 2

Abstract

Cancer can be detected by certain signs and symptoms, it is can be investigated by medical imaging and confirmed by biopsy. Many tumor cells express some kind of receptor, e.g., somatostatin receptors. Somatostatin receptor-positive human tumors can be detected using labeled analogues of somatostatin. In vitro labeled octreotide (OCT) has been successfully used in the visualization of somatostatin receptor-positive tumors by flow cytometry. OCT was labeled with fluorescein isothiocyanate (FITC) to easy identify the somatostatin receptor subtype 2 (SSTR 2) in different living cell lines. The labelling of OCT was proceeded depending on the the difference of pKa of amino groups of OCT. The reaction was proceeded at pH 6 as the amino group phenylalanine has pKa 7.1 and the amino group of lysine has pKa 10.1. The labelling of OCT was confirmed by high performance liquid chromatography and mass spectrometry. The expression of somatostatin receptor in tumor cells was confirmed by incubation with FITC-OCT. All cells were positively expressed with SSTR2 in comparison with standard positive SSTR2. The labelled FITC-OCT is a promising model for identification of SSTR2. The tumor cell lines were choosed in this study were completely positive SSTR2.