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Abstract

Imaging oncogene mRNA in tumours would provide a powerful tool for the early detection of occult malignant lesions. The goal was to prepare a chimera consisting of a dodecamer antisense peptide nucleic acid (PNA) specific for c-MYC oncogene overexpressed in human breast cancer cells and a chelating moiety that facilitates quantitative radiolabelling with 99mTc and evaluate it for hybridization and tissue distribution in laboratory animals. The pentapeptide chelator-PNA dodecamer specific for c-MYC mRNA was extended from a solid support by 9-fluorenylmethyloxycarbonyl (Fmoc) coupling. Similarly, a chelator-PNA chimera with four central mismatches was also prepared which served as a control. The chimeras were purified, characterized and evaluated for hybridization to c-MYC mRNA by fluorescent, real-time polymerase chain reaction (RT-PCR). The chimeras were labelled with 99mTc and their tissue distribution was examined in athymic nude mice bearing experimental human breast tumours. 99mTc radiolabelling was quantitative and presented a single peak in reversed phase liquid chromatography. Fluorescent real-time polymerase chain reactions using primer and fluorescent probe sets previously calculated for c-MYC mRNA demonstrated inhibition of reverse transcription by the c-MYC specific chimera as compared to that of the control. Tissue distribution studies of antisense and mismatch chimeras at 4 h and 24 h after administration displayed modest accumulation in the liver, and appreciable levels in tumours. These observations suggest that 99mTc-peptide-PNA probes might be useful for imaging gene expression in tumours, and the approach is worthy of further investigation.

Preparation, 99mTc-labeling and biodistribution studies of a PNA oligomer containing a new ligand derivative of 2,2′-dipicolylamine

“…In such constructs, the role of the PNA is to direct the bioconjugate to a specific mRNA -a unique or a uniquely over-expressed mRNA in a diseased cell -while the function of the radioactive probe is to allow imaging to possibly provide information on cellular gene expression pattern and detect molecular changes at relatively early stages [13,42]. Hence, a number of in vivo biodistribution/hybridization studies of radiolabeled PNAs were undertaken [14,[17][18][19][20]22,[24][25][26][27][28][29][30][31][32][33]36,39,41,[43][44][45][46]. The majority of these reports involved the use of 99m Tc, probably due its ideal nuclear properties and the convenient availability from a commercial generator [47][48][49][50].…”

Design of (Gd‐DO3A)n‐polydiamidopropanoyl‐peptide nucleic acid‐D(Cys‐Ser‐Lys‐Cys) magnetic resonance contrast agents

“…Noninvasive molecular imaging of gene expression by intracellular hybridization of complementary oligonucleotide derivatives to specific messenger RNAs in cells has been attempted by radionuclide imaging or fluorescent imaging to diagnose cancer and other diseases in living systems 1–13. Radionuclide imaging is very sensitive, but generally used in human subjects when suspect masses are evident or highly likely.…”

Towards the Preparation of Novel Re/99mTc Tricarbonyl-Containing Peptide Nucleic Acid Bioconjugates

“…The examples of successful preparations of Re-containing PNA oligomers are surprisingly scarce, 23,26,28,29 whilst those of 99m Tc-containing PNA oligomers are more common. 19,27,[29][30][31][32][33][34] Re tricarbonyl PNA bioconjugates can be used as IR spectroscopical biosensors for DNA/RNA sequences. Indeed, the presence of intense carbonyl absorptions in the 1800-2200 cm -1 region render possible the selective detection and even quantification of the metal-PNA bioconjugates by IR spectroscopy (carbonyl metallo immuno assay, CMIA).…”