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18F-glutathione conjugate as a PET tracer for imaging tumors that overexpress L-PGDS enzyme.

Huang HL, Huang YC, Lee WY, Yeh CN, Lin KJ, Yu CS - PLoS ONE (2014)

Bottom Line: The inhibition percentage of the production of PGD2 from PGH2 at the presence of 200 µM of FBuEA-GS and 4-Dibenzo[a,d]cyclohepten-5-ylidene-1-[4-(2H-tetrazol-5-yl)butyl]piperidine (AT-56) were 74.1 ± 4.8% and 97.6 ± 16.0%, respectively. [18F]FBuEA-GS bound L-PGDS (16.3-21.7%) but not the isoform, microsomal prostaglandin E synthase 1.No binding to GST-alpha and GST-pi was observed.The contrasted images indicated that the radiotracer accumulation in tumor lesions is probably related to the overexpression of L-PGDS.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsinghua University, Hsinchu, Taiwan.

ABSTRACT
Lipocalin-type prostaglandin D synthase (L-PGDS) has been correlated with the progression of neurological disorders. The present study aimed at evaluating the imaging potency of a glutathione conjugate of fluorine-18-labeled fluorobutyl ethacrynic amide ([18F]FBuEA-GS) for brain tumors. Preparation of [18F]FBuEA-GS has been modified from the -4-tosylate derivative via radiofluorination in 5% radiochemical yield. The mixture of nonradioactive FBuEA-GS derived from a parallel preparation has be resolved to two isomers in a ratio of 9:1 using analytic chiral reversed phase high performance liquid chromatography (RP-HPLC). The two fluorine-18-labeled isomers purified through nonchiral semipreparative RP-HPLC as a mixture were studied by assessing the binding affinity toward L-PGDS through a gel filtration HPLC, by analyzing radiotracer accumulation in C6 glioma cells, and by evaluating the imaging of radiotracer in a C6 glioma rat with positron emission tomography. The inhibition percentage of the production of PGD2 from PGH2 at the presence of 200 µM of FBuEA-GS and 4-Dibenzo[a,d]cyclohepten-5-ylidene-1-[4-(2H-tetrazol-5-yl)butyl]piperidine (AT-56) were 74.1 ± 4.8% and 97.6 ± 16.0%, respectively. [18F]FBuEA-GS bound L-PGDS (16.3-21.7%) but not the isoform, microsomal prostaglandin E synthase 1. No binding to GST-alpha and GST-pi was observed. The binding strength between [18F]FBuEA-GS and L-PGDS has been evaluated using analytic gel filtration HPLC at the presence of various concentrations of the cold competitor FBuEA-GS. The contrasted images indicated that the radiotracer accumulation in tumor lesions is probably related to the overexpression of L-PGDS.

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Comparison between the cellular uptake of two radiotracers.The radioactivity uptake of [18F]FBuEA-GS 3 (a) and [18F]FBuEA 2 (b) by C-6 tumor cells (redline) and fibroblasts (blue line).
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pone-0104118-g006: Comparison between the cellular uptake of two radiotracers.The radioactivity uptake of [18F]FBuEA-GS 3 (a) and [18F]FBuEA 2 (b) by C-6 tumor cells (redline) and fibroblasts (blue line).

Mentions: As shown in Fig. 6a, the accumulation of radioactivity of [18F]FBuEA-GS 3 was higher in tumor cells compared to that of normal cells (9% vs. 6%). Although the difference in tracer uptake between C6 glioma and fibroblast lies within the statistic error (p<0.001 at 0 min and p>0.05 at rest time points), the accumulation level in C-6 glioma cell is higher. The accumulation pattern also differed from that of [18F]FBuEA 2, which had a lower uptake in tumor cells compared to normal cell (Fig. 6b). These data indicate that the higher tumor cell uptake of [18F]FBuEA-GS 3 was due to the GSH moiety. However, the accumulation levels of radioactivity in tumor and normal cells decreased at late stages, which may imply that an initial supply of GSH was required by both cells in order for early antioxidation to maintain homeostatic functions. After reaching a steady state (approximately 15 min), the preferential radioactivity accumulation in tumors cell was maintained but then steadily decreased. The aforementioned insignificant difference in tracer uptake was also observed in that case of [18F]fluorothymidine ([18F]FLT); 4% vs. 3% for tracer uptake in the two cells (unpublished work). [18F]FLT is nevertheless a potential tracer for brain tumor imaging as described in the introduction part. The higher tracer accumulation in tumor cells at a later stage may imply an overexpression of GSH-binding membrane proteins. Thus, immunohistological staining for L-PGDS and COXs enzymes of tumor cells and normal cells was performed (Fig. 7). The results showed that, with the exception of COX-1, L-PGDS and COX-2 were both overexpressed in tumor cells.


18F-glutathione conjugate as a PET tracer for imaging tumors that overexpress L-PGDS enzyme.

Huang HL, Huang YC, Lee WY, Yeh CN, Lin KJ, Yu CS - PLoS ONE (2014)

Comparison between the cellular uptake of two radiotracers.The radioactivity uptake of [18F]FBuEA-GS 3 (a) and [18F]FBuEA 2 (b) by C-6 tumor cells (redline) and fibroblasts (blue line).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128654&req=5

pone-0104118-g006: Comparison between the cellular uptake of two radiotracers.The radioactivity uptake of [18F]FBuEA-GS 3 (a) and [18F]FBuEA 2 (b) by C-6 tumor cells (redline) and fibroblasts (blue line).
Mentions: As shown in Fig. 6a, the accumulation of radioactivity of [18F]FBuEA-GS 3 was higher in tumor cells compared to that of normal cells (9% vs. 6%). Although the difference in tracer uptake between C6 glioma and fibroblast lies within the statistic error (p<0.001 at 0 min and p>0.05 at rest time points), the accumulation level in C-6 glioma cell is higher. The accumulation pattern also differed from that of [18F]FBuEA 2, which had a lower uptake in tumor cells compared to normal cell (Fig. 6b). These data indicate that the higher tumor cell uptake of [18F]FBuEA-GS 3 was due to the GSH moiety. However, the accumulation levels of radioactivity in tumor and normal cells decreased at late stages, which may imply that an initial supply of GSH was required by both cells in order for early antioxidation to maintain homeostatic functions. After reaching a steady state (approximately 15 min), the preferential radioactivity accumulation in tumors cell was maintained but then steadily decreased. The aforementioned insignificant difference in tracer uptake was also observed in that case of [18F]fluorothymidine ([18F]FLT); 4% vs. 3% for tracer uptake in the two cells (unpublished work). [18F]FLT is nevertheless a potential tracer for brain tumor imaging as described in the introduction part. The higher tracer accumulation in tumor cells at a later stage may imply an overexpression of GSH-binding membrane proteins. Thus, immunohistological staining for L-PGDS and COXs enzymes of tumor cells and normal cells was performed (Fig. 7). The results showed that, with the exception of COX-1, L-PGDS and COX-2 were both overexpressed in tumor cells.

Bottom Line: The inhibition percentage of the production of PGD2 from PGH2 at the presence of 200 µM of FBuEA-GS and 4-Dibenzo[a,d]cyclohepten-5-ylidene-1-[4-(2H-tetrazol-5-yl)butyl]piperidine (AT-56) were 74.1 ± 4.8% and 97.6 ± 16.0%, respectively. [18F]FBuEA-GS bound L-PGDS (16.3-21.7%) but not the isoform, microsomal prostaglandin E synthase 1.No binding to GST-alpha and GST-pi was observed.The contrasted images indicated that the radiotracer accumulation in tumor lesions is probably related to the overexpression of L-PGDS.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering and Environmental Sciences, National Tsinghua University, Hsinchu, Taiwan.

ABSTRACT
Lipocalin-type prostaglandin D synthase (L-PGDS) has been correlated with the progression of neurological disorders. The present study aimed at evaluating the imaging potency of a glutathione conjugate of fluorine-18-labeled fluorobutyl ethacrynic amide ([18F]FBuEA-GS) for brain tumors. Preparation of [18F]FBuEA-GS has been modified from the -4-tosylate derivative via radiofluorination in 5% radiochemical yield. The mixture of nonradioactive FBuEA-GS derived from a parallel preparation has be resolved to two isomers in a ratio of 9:1 using analytic chiral reversed phase high performance liquid chromatography (RP-HPLC). The two fluorine-18-labeled isomers purified through nonchiral semipreparative RP-HPLC as a mixture were studied by assessing the binding affinity toward L-PGDS through a gel filtration HPLC, by analyzing radiotracer accumulation in C6 glioma cells, and by evaluating the imaging of radiotracer in a C6 glioma rat with positron emission tomography. The inhibition percentage of the production of PGD2 from PGH2 at the presence of 200 µM of FBuEA-GS and 4-Dibenzo[a,d]cyclohepten-5-ylidene-1-[4-(2H-tetrazol-5-yl)butyl]piperidine (AT-56) were 74.1 ± 4.8% and 97.6 ± 16.0%, respectively. [18F]FBuEA-GS bound L-PGDS (16.3-21.7%) but not the isoform, microsomal prostaglandin E synthase 1. No binding to GST-alpha and GST-pi was observed. The binding strength between [18F]FBuEA-GS and L-PGDS has been evaluated using analytic gel filtration HPLC at the presence of various concentrations of the cold competitor FBuEA-GS. The contrasted images indicated that the radiotracer accumulation in tumor lesions is probably related to the overexpression of L-PGDS.

Show MeSH
Related in: MedlinePlus