Noninvasive imaging of human telomerase reverse transcriptase (hTERT) messenger RNA with 99mTc-radiolabeled antisense probes in malignant tumors

作者：Men Liu; Ron-Fu Wang^*; Chun Li Zhang; Ping Yan; Ming Ming, Yu; Li Juan Di; Hong Jie Liu; Feng Qin Guo

来源：Journal of Nuclear Medicine, 2007, 48(12): 2028-2036.

DOI：10.2967/jnumed.107.042622

• Tc-99m
• antisense
• molecular imaging
• human telomerase reverse transcriptase
• hTERT
• biodistribution

The expression of human telomerase reverse transcriptase (hTERT) is present in most malignant cells (>85%) but is undetectable in most normal somatic cells. Visualization of hTERT expression using radionuclide targeting can provide important diagnostic information in malignant tumors. The overall aim of this study was to evaluate whether Tc-99m-radiolabeled antisense oligonucleotide (ASON) targeting hTERT messenger RNA (mRNA) can be used for imaging of hTERT expression in vivo. Methods: One 18-mer antisense or sense uniformly phosphorothioate-modified oligonucleotide targeting hTERT mRNA was radiolabeled with Tc-99m through the bifunctional chelator N-hydroxysuccinimidyl derivative of S-acetylmercaptoacetyltriglycine (S-acetyl NHS-MAG3). Then the radiolabeled probe was characterized in vitro. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to assay the mRNA level after proliferating cells had been incubated with the antisense and sense probes. Tc-99m-MAG3-ASON or Tc-99m-MAG3-SON was injected intravenously in mammary tumor-bearing BALB/c nude mice. Biodistribution and in vivo imaging was performed periodically. All data were analyzed by statistical software. Results: The labeling efficiencies of Tc-99m-MAG3-ASON/SON reached 76% +/- 5% (n = 5) within 15-30 min at room temperature, the specific activity was up to 1,850 kBq/mu g, and the radiochemical purity was >96% after purification. Tc-99m-MAG3-ASON showed complete stability at room temperature and in fresh 37 degrees C human serum. In comparison with Tc-99m-MAG3-SON, Tc-99m-MAG3-ASON preserved the capacity to bind living hTERT-expressing cells specifically and to inhibit the expression of hTERT mRNA significantly as well as ASON. In nude mice bearing hTERT-expressing MCF-7 xenografts, tumor radioactivity uptake of 99mTc-MAG3-ASON after injection was significantly higher than that of 99mTc-MAG3-SON after injection (P < 0.05). The hTERT-expressing xenografts were clearly imaged at 4-8 h noninvasively after injection of Tc-99m-MAG3-ASON, whereas the xenografts were not imaged at any time after injection of Tc-99m-MAG3-SON. Conclusion: This in vivo study provides evidence that Tc-99m-MAG3-ASON targeting hTERT mRNA can be used as a potential candidate for visualization of hTERT expression in carcinomas.

• 出版日期2007-12
• 单位北京大学