Antisense imaging of colon cancer-bearing nude mice with liposome-entrapped 99m-technetium-labeled antisense oligonucleotides of c-mycmRNA

AIM: To investigate the feasibility for antisense imaging of the colon cancer with liposome-entrapped 99 m-technetium labeled antisense oligonucleotides as tracers.METHODS: Fifteen mer single-stranded aminolinked phosphorothioate antisense oligonucleotides of c-myc mRNA were labeled with .^99mTc-pertechnetate, then purified and finally entrapped with liposomes to form the labeling compounds, liposome-entrapped ^99mTc-labeled antisense oligonucleotides. The LS-174-T cells (colon of adenocarcinoma cell line) were incubated with the labeling compounds to test the uptake rates of LS-174-T cells. Later on, a model of 30 tumor bearing nude mice was constructed by inoculating with 5×10^6 of LS-174-T cells at right flank of each nude mouse. About 10 d later, the model were adminstered by intravenous injection of the liposomeentrapped ^99mTc-labeled antisense oligonucleotides. Then some of the tumour bearing nude mice were sacrificed at 0.5, 1, 2, and 4 h after intravenous injection, and proper quantity of liver, spleen, tumor, etc. was obtained. The tissues were counted in a gamma counter, and after correction for decay and background activity, expressed as a percentage of the injected dose. The others whose anterior and posterior whole-body scans were obtained at 1, 1.5, 2, 4,6 and 24 h with a dual-head bodyscan camera equipped with parallel-hole low-energy collimaters. The ratios of radioactive counts in tumor to that in contralateral equivalent region of abdomen were calculated.RESULTS: The uptake rates of LS-174-T cells for liposomeentrapped ^99mTc-labeled antisense oligonucleotides increased as time prolonged and reach the peak (17.77±2.41%) at 7 h.The biodistributions showed that the rdioactivity in the tumor (13.46±0.20%) of injected dose was the highest at 2 h of intravenous injection of liposome-entrapped ^99mTclabeled antisense oligonucleotides, and then decreased sharply to 4.58±0.45% at 4 h. The tumor was shown clearly in the whole-body scan at 2 h of intravenous injection. The ratios, radioactive counts in tumor to that in contralateral equivalent region of abdomen (1.7332±0.2537), was the highest one at 2 h after intravenous injection of liposomeentrapped ^99mTc-labeled antisense oligonucleotides.CONCLUSION: The liposome-entrapped ^99mTc-labeled antisense oligonucleotides deserve being developed into radiopharmaceutics for the colon cancer imaging,

AIM:To investigate the feasibility for antisense imaging of the colon cancer with liposome-entrapped 99 m-technetium labeled antisense oligonucleotides as tracers. METHODS:Fifteen mer single-stranded aminolinked phosphorothioate antisense oligonucleotides of c-myc mRNA were labeled with ^(99m)Tc-pertechnetate,then purified and finally entrapped with liposomes to form the labeling compounds,liposome-entrapped ^(99m)Tc-labeled antisense oligonudeotides.The LS-174-T cells(colon of adenocardnoma cell line)were incubated with the labeling compounds to test the uptake rates of LS-174-T cells.Later on,a model of 30 tumor bearing nude mice was constructed by inoculating with 5×10~6 of LS-174-T cells at right flank of each nude mouse.About 10 d later,the model were adminstered by intravenous injection of the liposome- entrapped ^(99m)Tc-labeled antisense oligonucleotides.Then some of the tumour bearing nude mice were sacrificed at 0.5,1,2,and 4 h after intravenous injection,and proper quantity of liver,spleen,tumor,etc.was obtained.The tissues were counted in a gamma counter,and after correction for decay and background activity,expressed as a percentage of the injected dose.The others whose anterior and posterior whole-body scans were obtained at 1,1.5,2,4, 6 and 24 h with a dual-head bodyscan camera equipped with parallel-hole low-energy collimaters.The ratios of radioactive counts in tumor to that in contralateral equivalent region of abdomen were calculated. RESULTS:The uptake rates of LS-174-T cells for liposome- entrapped ^(99m)Tc-labeled antisense oligonucleotides increased as time prolonged and reach the peak(17.77±2.41%)at 7 h. The biodistributions showed that the rdioactivity in the tumor(13.46±0.20%)of injected dose was the highest at 2 h of intravenous injection of liposome-entrapped ^(99m)Tc- labeled antisense oligonucleotides,and then decreased sharply to 4.58±0.45% at 4 h.The tumor was shown clearly in the whole-body scan at 2 h of intravenous injection.The ratios,radioactive counts in tumor to that in contralateral equivalent region of abdomen(1.7332±0.2537),was the highest one at 2 h after intravenous injection of liposome- entrapped ^(99m)Tc-labeled antisense oligonucleotides. The liposome-entrapped ^(99m)Tc-labeled antisense oligonucleotides deserve being developed into radiopharmaceutics for the colon cancer imaging.