INTRODUCTION: The protein-protein crosslinking activity of the enzyme tissue transglutaminase (TG2; EC 2.3.2.13) is associated with the pathogenesis of various diseases, including celiac disease, lung-, liver- and kidney fibrosis, cancer and neurodegenerative diseases. This study aims at developing a TG2 PET tracer based on the peptidic irreversible TG2 inhibitor Z006. METHODS: Initially, the carbon-11 labeling of Z006 at the diazoketone position was explored. Subsequently, a set of analogues that allow for fluorine-18 labeling was synthesized. Two potent analogues, 6f and 6g, were radiolabeled with fluorine-18 and biodistribution and metabolite analysis in Wistar rats was performed. The identity of the main metabolite of [18F]6g was elucidated using LC-MS/MS. In vitro binding to isolated TG2 and in vitro autoradiography on MDA-MB-231 breast cancer tissue using [18F]6g was performed. RESULTS: [18F]6f and [18F]6g were obtained in 20 and 9% yields, respectively. Following administration to healthy Wistar rats, rapid metabolism of both tracers was observed. Remarkably, full conversion to just one single metabolite was observed for one of the tracers, [18F]6g. By LC-MS/MS analysis this metabolite was identified as C-terminally saponified [18F]6g. This metabolite was also found to be a potent TG2 inhibitor in vitro. In vitro binding to isolated TG2 and in vitro autoradiography on MDA-MB-231 tumor sections using [18F]6g demonstrated high specific and selective binding of [18F]6g to active TG2. CONCLUSIONS: Whereas based on the intensive metabolism [18F]6f seems unsuitable as a TG2 PET tracer, the results warrant further evaluation of [18F]6gin vivo.
INTRODUCTION: The protein-protein crosslinking activity of the enzyme tissue transglutaminase (TG2; EC 2.3.2.13) is associated with the pathogenesis of various diseases, including celiac disease, lung-, liver- and kidney fibrosis, cancer and neurodegenerative diseases. This study aims at developing a TG2 PET tracer based on the peptidic irreversible TG2 inhibitor Z006. METHODS: Initially, the carbon-11 labeling of Z006 at the diazoketone position was explored. Subsequently, a set of analogues that allow for fluorine-18 labeling was synthesized. Two potent analogues, 6f and 6g, were radiolabeled with fluorine-18 and biodistribution and metabolite analysis in Wistar rats was performed. The identity of the main metabolite of [18F]6g was elucidated using LC-MS/MS. In vitro binding to isolated TG2 and in vitro autoradiography on MDA-MB-231 breast cancer tissue using [18F]6g was performed. RESULTS: [18F]6f and [18F]6g were obtained in 20 and 9% yields, respectively. Following administration to healthy Wistar rats, rapid metabolism of both tracers was observed. Remarkably, full conversion to just one single metabolite was observed for one of the tracers, [18F]6g. By LC-MS/MS analysis this metabolite was identified as C-terminally saponified [18F]6g. This metabolite was also found to be a potent TG2 inhibitor in vitro. In vitro binding to isolated TG2 and in vitro autoradiography on MDA-MB-231 tumor sections using [18F]6g demonstrated high specific and selective binding of [18F]6g to active TG2. CONCLUSIONS: Whereas based on the intensive metabolism [18F]6f seems unsuitable as a TG2 PET tracer, the results warrant further evaluation of [18F]6gin vivo.
Authors: Berend van der Wildt; Micha M M Wilhelmus; Wissam Beaino; Esther J M Kooijman; Robert C Schuit; John G J M Bol; John J P Breve; Ralf Pasternack; Adriaan A Lammertsma; Albert D Windhorst; Benjamin Drukarch Journal: EJNMMI Res Date: 2018-05-25 Impact factor: 3.138
Authors: Micha M M Wilhelmus; Osoul Chouchane; Maarten Loos; Cornelis A M Jongenelen; John J P Brevé; Allert Jonker; John G J M Bol; August B Smit; Benjamin Drukarch Journal: Neuropathol Appl Neurobiol Date: 2022-02-23 Impact factor: 6.250