ABSTRACT
ObjectiveTo investigate the value of 99Tcm labeled survivin mRNA antisense peptide nucleic acid (PNA) as an imaging agent in the specific diagnosis for carcinoma.MethodsSurvivin mRNA antisense PNA was labeled directly with 99Tcm by the ligand-exchange method.Twenty nude mice with lung carcinoma A549 xenografts were randomly divided into 4 groups.Three groups were used for biodistribution study and one group was used for imaging study.Other twenty mice infected by staphylococcus aureus underwent the same procedure.The biodistribution and imaging of 99Tcm-survivin mRNA antisense PNA was studied at 1,2 and 4 h respectively after the intravenous injection in nude mice bearing lung carcinoma A549 xenografts or inflammation models.SPSS 13.0 was used in the study and all data were analyzed by t test.ResultsBiodistribution results showed that the highest radioactivity was found in the liver,and then in the kidney.Four hours after the administration of the imaging agent,the radioactivity ratios of target-tonon target (T/NT,tumor or inflamumatory lesions to the contralateral regions) in tumor model group were significantly higher than those in inflammation model group ( 3.69 ± 1.13 vs 2.03 ± 0.47,t =3.01,P =0.02 ).Tumors were clearly visible in the tumor model groups at 0.5 h and still clearly seen at 4 h after the injection of antisense PNA.On the contrary,inflammatory lesions could not be seen clearly.Conclusion 99Tcm labeled survivin mRNA antisense PNA can be used to distinguish tumor from inflammation and it may provide a new feasible method for specific tumor diagnosis.
ABSTRACT
Objective To prepare the 99Tcm-survivin mRNA antisense peptide nucleic acid (PNA)and investigate its value as a gene imaging agent in tumor bearing mice and early diagnosis in tumor.Methods Survivin mRNA antisense PNA and mismatch PNA were synthesized.Four amino acids (Gly- (D)Ala-Gly-Gly) and Aba (4-aminobutyric acid) were linked to the 5' end of PNA.Gly- (D)Ala-Gly-Gly served as a chelating moiety for strong chelation of 99Tcm and Aba acted as a spacer to minimize the steric hindrance.PNAs were labeled with 99Tcm by the ligand-exchange method.The labeling efficiency and radiochemical purity were measured by HPLC and ITLC methods.There were five BALB/c nude mice bearing human lung carcinoma ( A549 ) in each of antisense PNA and mismatch PNA groups.Gene imaging of 99Tcm-survivin mRNA antisense and mismatch PNAs were performed at 1,2 and 4 h post the injection,respectively,and the T/NT ratio was measured by the method of ROI.The statistical comparisons of average values were performed with the two-group t-test for independent sample by SPSS 13.0.Results The product kept stable in vitro.The labeling efficiency of 99Tcm-survivin mRNA antisense PNA was (95.48 ±1.92)％ and more than 85％ after the incubation for24 h in serum.The radiochemical purity was ＞ 95％.The labeling efficiency of mismatch PNA was similar to the antisense PNA.99Tcm-survivin mRNA antisense PNA was especially uptaken by tumor lesion,and its accumulation reached the top at 4 h post the injection.T/NT ratios at 1,2,and 4 h were 2.70 ± 0.28,3.44 ± 0.35,4.21 ± 0.63,respectively.In the comparison,the T/NT ratio of 99Tcm-survivin mRNA mismatch PNA at 4 h (3.12 ±0.50) was significantly lower (t =2.918,P =0.019).Conclusions 99Tcm-survivin mRNA antisense PNA has high labeling efficiency,good stability and no need of purification.Its characteristic of especial uptake by tumor lesion provides the potential value in early diagnosis of tumor.