open access

https://hdl.handle.net/2115/50770

Radiolabeled uracil derivative as a novel SPECT probe for thymidine phosphorylase : suppressed accumulation into tumor cells by target gene knockdown

英語

thymidine phosphorylase

2011-12

Lippincott Williams & Wilkins

Nuclear Medicine Communications

32(12)

1211-1215

Objectives: We developed a radiolabeled uracil derivative, 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil (IIMU), as a novel SPECT probe for thymidine phosphorylase (TP). This radioiodinated IIMU has a high affinity for TP, and highly accumulates in the TP-expressing tumor cell line A431 (human epidermoid carcinoma). To evaluate the specificity of the cellular uptake of IIMU to TP expression, we examined the effects of TP knockdown on the uptake of 125I-labeled IIMU (125I-IIMU) in the tumor cells. Methods: TP-specific siRNA, glyceraldehyde 3-phosphate dehydrogenase (GAPDH)-specific siRNA (positive control), and negative control siRNA were transfected into A431 cells, respectively. Target-mRNA and protein expression levels of TP and GAPDH were examined 48 and 72 hours after transfection, respectively. The cellular uptake level of 125I-IIMU was also evaluated 72 hours after transfection. The results were compared after normalization with the corresponding negative controls. Results: After TP- and GAPDH-specific siRNA transfection, the expression levels of TP and GAPDH mRNA significantly decreased to 41% and 29%, respectively, as compared with the negative control (p < 0.001 for both). The expression levels of TP and GAPDH protein also significantly decreased to 34% and 30%, respectively (p < 0.001 for both). After TP-specific siRNA transfection, the cellular uptake level of 125I-IIMU significantly decreased to 66% (p < 0.001). In contrast, GAPDH siRNA transfection did not significantly affect the cellular uptake level of 125I-IIMU. Conclusion: siRNA-mediated TP knockdown significantly decreased the cellular uptake level of 125I-IIMU. This finding indicates that the uptake of IIMU in tumor cells is TP-specific and directly corresponds to TP expression levels.

学術雑誌論文

Accepted Manuscript

This is a non-final version of an article published in final form in Nuclear Medicine Communications 32(12), December 2011, pp.1211–1215

0143-3636