直接和间接^(99)mTc标记GX1短肽对荷瘤小鼠SPECT成像的对比分析

Comparative analysis of direct and indirect ^(99)mTc-labeled GX1 peptides for single-photon emission computed tomography imaging in tumor-bearing mice

目的采用直接和间接标记法制备胃癌靶向探针,对比分析2种探针的成像能力。方法利用胃癌血管靶向肽GX1,采用直接标记法标记^(99)mTc,制备^(99)mTc-GX1;GX1偶连双功能螯合剂肼基尼古酰胺(HYNIC)后,采用间接标记法标记^(99)mTc,制备^(99)mTc-HYNIC-GX1;对2种探针测定标记率和稳定性后,进行受体放射配基结合分析。将2种探针通过尾静脉注入荷胃癌BALB/c裸鼠体内(每组3只)进行SPECT成像,计算瘤心比,对2种探针进行定量评价。结果成功制备^(99)mTc-GX1和^(99)mTc-HYNIC-GX1探针,标记率达(97.15±1.33)%和(96.68±0.60)%,在小鼠血清中的标记率分别为(96.96±0.73)%和(96.36±0.77)%,差异无统计学意义,t值分别为0.2207和0.5691,均P>0.05。体外受体放射配基结合分析显示,2种探针与Co-HUVEC结合后测得的放射性计数分别为(149.17±8.27)和(146.10±11.55)Bq,差异无统计学意义(t=0.3539,P>0.05),且可以被未标记的GX1所抑制。SPECT成像显示,2种探针可以在体靶向到胃癌组织,12 h的瘤心比为1.63±0.22和1.72±0.24,差异无统计学意义,t=0.4788,P>0.05。结论采用直接和间接标记法制备的探针特异性和靶向性没有显著差别,均可以用于荷瘤裸鼠的SPECT成像。

Objective To prepare targeting probes to gastric cancer by direct or indirect labeling methods,and to compare the imaging abilities of the two probes.Methods The GX1 peptide homing to gastric cancer vasculature was labeled with ^(99)mTc by direct labeling method to prepare ^(99)mTc-GX1.GX1 was coupled with the bifunctional chelating agent Hydrazinonic(HYNIC),and was labeled with ^(99)mTc by indirect labeling method to prepare ^(99)mTc-HYNIC-GX.The labeling rate and stability of the two probes were determined,the radioligand binding analysis of the two probes were performed.Two probes were injected into BALB/c nude mice with gastric cancer through tail vein(n=3 in each group)for single-photon emission computed tomography(SPECT)imaging.The tumor/heart ratios were calculated and the two probes were quantitatively evaluated.Results ^(99)mTc-GX1 and ^(99)mTc-HYNIC-GX1 probes were successfully prepared and their labeling rates were(97.15±1.33)%and(96.68±0.60)%.The labeling rates in mouse serum were(96.96±0.73)%and(96.36±0.77)%respectively and the difference was not statistically significant within 24 hours(t values were 0.2207 and 0.5691,both P>0.05).In vitro receptor radioligand binding assay showed that the radioactivity counts of the two probes bound to Co-HUVEC were(149.17±8.27)and(146.10±11.55)Bq respectively(t=0.3539,P>0.05).They could be inhibited by unlabeled GX1.SPECT imaging showed that the two probes could target gastric cancer tissue in vivo,and the tumor-to-heart ratio at 12 hours was 1.63±0.22 and 1.72±0.24.There was no significant difference statistically between the two probes(t=0.4788,P>0.05).Conclusion There is no significant difference in the specificity and targeting of the probes prepared by direct and indirect labeling methods,and both probes can be used for SPECT imaging of gastric cancer-bearing nude mice.