Synthesis and biological evaluation of 11C-labeled β-galactosyl triazoles as potential PET tracers for in vivo LacZ reporter gene imaging
作者:Sofie Celen、Jan Cleynhens、Christophe Deroose、Tjibbe de Groot、Abdelilah Ibrahimi、Rik Gijsbers、Zeger Debyser、Luc Mortelmans、Alfons Verbruggen、Guy Bormans
DOI:10.1016/j.bmc.2009.05.056
日期:2009.7
In our aim to develop LacZ reporter probes with a good retention in LacZ expressing cells, we report the synthesis and preliminary evaluation of two carbon-11 labeled beta-galactosyl triazoles 1-(beta-D-galactopyranosyl)4-(p-[C-11]methoxyphenyl)-1,2,3-triazole ([C-11]-6) and 1-(beta-D-galactopyranosyl)-4-(6-[C-11]methoxynaphthyl)-1,2,3-triazole ([C-11]-13). The precursors for the radiolabeling and the non-radioactive analogues (6 and 13) were synthesized using straightforward 'click' chemistry. In vitro incubation experiments of 6 with beta-galactosidase in the presence of o-nitrophenyl beta-D-galactopyranoside (ONPG) showed that the triazolic compound was an inhibitor of beta-galactosidase activity. Radiolabeling of both precursors was performed using [C-11] methyl iodide as alkylating agent at 70 degrees C in DMF in the presence of a small amount of base. The log P values were -0.1 and 1.4, respectively, for [C-11]-6 and [C-11]-13, the latter therefore being a good candidate for increased cellular uptake via passive diffusion. Biodistribution studies in normal mice showed a good clearance from blood for both tracers. [C-11]-6 was mainly cleared via the renal pathway, while the more lipophilic [C-11]-13 was excreted almost exclusively via the hepatobiliary system. Despite the lipophilicity of [C-11]-13, no brain uptake was observed. Reversed phase HPLC analysis of murine plasma and urine revealed high in vivo stability for both tracers. In vitro evaluation in HEK-293T cells showed an increased cell uptake for the more lipophilic [C-11]-13, however, there was no statistically higher uptake in LacZ expressing cells compared to control cells. (C) 2009 Elsevier Ltd. All rights reserved.