| Objective:This study was to prepare 99Tcm-ZHER2:V2-Pemetrexed and investigate its distribution and molecular imagingin nude mice bearing xenografted lung adenocarcinoma with different levels of HER2 expression includes H2009 model?A549 model and H23 model.The aim of this study was to explore the feasibility of the probe 99Tcm-ZHER2:V2-Pemetrexed with combination of diagnosis and treatment used for target uptake characteristics and diagnostic value of HER2 expression in vivo.Methods:For biodistribution studies,BALB/c nude mice?n=12?bearing high HER2-expressing H2009 xenograftswere injected 100?l?37kBq?99Tcm-ZHER2:V2-Pemetrexed into each mouse via the tail vein.And prepare99Tcm-ZHER2:V2-Pemetrexed with the same radioactivty and volume as the standard source.The mice were sacrificed by cervical dislocation at different time point:1,2,4 and 6 h Blood,heart,liver,spleen,lung,kidney,stomach,small intestine,brain,bone,muscle and tumor were collected,weighed and measured for radioactivty by gamma counter.The biodistribution of the agent was measured as%ID/g were calculated.The same method was taken in nude mice bearing A549 and H23 xenografts.Then,analyze the biodistribution state in above three xenografts.In molecular imaging studieswas performed on 5 nude mice with H2009?A549 or H23 xenografts at1,2,4 and 6 h after intravenous injection of99Tcm-ZHER2:V2-Pemetrexed 100?l?37MBq,100?l?The ratio of radioactive counts in the tumor to that in the contralateral equivalent region?target to nontarget ratio[T/NT]?were calculated by drawing regions of interest?ROI?at each time point.In addition,5 mice bearing the H2009 and A549 tumor xenografts were randomly select and pre-injected with500?g non-labelled ZHER2:V2-Pemetrexed,to saturate the HER2 receptors of tumours.At 1,2,4and 6h after injection,the mice were imaged.Analyze the blocking effect of excessofnon-labelledZHER2:V2-Pemetrexedtotheprobe99Tcm-ZHER2:V2-Pemetrexed and its specificity.All experimental variables were expressed as mean±SD and were performed with Two-sample t?or t??test or Wilcoxon rank sum test using SPSS?version 22.0?.P values of less than 0.05were considered significant.Results:The results of biodistribution showed that radioactive accumulations in high HER2 expression lung adenocarcinoma H2009 and high HER2 expression lung adenocarcinoma A549 xenografts were high,and the uptake gradually increases with time,while low HER2 expression lung adenocarcinoma H23 xenografts were extremely low.the tumor uptake of H2009 was 3.42±2.54,4.76±2.27,5.29±3.16,5.67±3.43%ID/g at 1,2,4 and 6h,respectively.and the tumor uptake of A549 was extremely low1.79±0.23,2.17±0.44,2.68±0.58,3.22±0.71%ID/gat 1,2,4 and6h,respectively.ThebiodistributionofH23xenograftswas0.19±0.04,0.17±0.08,0.23±0.05,0.08±0.05%ID/g.Inaddition,arapid clearance of 99Tcm-ZHER2:V2-Pemetrexed from most of the normal organs except the kidneys and the HER2-expressing tumors.In vivo imaging,A549 tumor-bearing mice were visualized as early as 1h and were shown most clearly at 6h after the administration of99Tcm-ZHER2:V2-Pemetrexed.The T/NT ratios of H2009 models was1.85±0.52,2.61±0.65,3.43±1.07,4.62±1.65 at 1,2,4 and 6h,respectively.The T/NT ratios of A549 models was 1.79±0.23,2.17±0.44,2.68±0.58,3.22±0.71 at1,2,4 and 6h,respectively.There was no obvious tumor uptake in low HER2-expressing H23 xenografts at 1h and afterwards light radioactivity uptake were visualized,but had no radioactivity uptake peak.The T/NT ratios of H23 models was 1.19±0.13,1.53±0.31,1.80±0.33,2.07±0.30 at 1,2,4 and6h,respectively.The tumors in H2009 and A549 tumor-bearing mice accumulated obviously more radioactivity than did the H23 xenografts.The P or Z values of H2009 and H23 was 0.008,0.001,0.000,0.008 at 1,2,4 and6h,respectively?differences are statistically significant?.The P or Z values of H2009 and H23 was 0.002,0.009,0.004,0.002 at 1,2,4 and 6h,respectively?differences are statistically significant?.All the time point did not observe the uptake in tumors of blocked HER2-expressing H2009 and A549models,indicate that the probe 99Tcm-ZHER2:V2-Pemetrexed can be blocked by excessofnon-labelledZHER2:V2-Pemetrexed.Themolecularagent99Tcm-ZHER2:V2-Pemetrexed.The radioactive uptake in tumors was further confirmed to be HER2 receptor-specific.Conclusions:Molecular probe 99Tcm-ZHER2:V2-Pemetrexed has good biodistribution in vivo,which is uptake obversely in tumors of HER2-expressing H2009 and A549 models,kidneys second.This molecular probe showed high specificity for HER2 overexpressing lung adenocarcinoma models.,and could be used in high HER2-expression tumor imaging.99Tcm-ZHER2:V2-Pemetrexed maybe developed as a potentially new method of tracer for precision diagnosis for high HER2-expressing tumors. |
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