In vivo characterization of 99mTc-spermine in mice bearing human breast cancer xenografts

Objectives Spermine is the most abundant polyamine in breast tumors and played a specific role in tumor cell growth and differentiation. Previous study indicated that 99mTc-labeled spermine has encouraged pharmacokinetics in mouse 4T1 breast tumor model. Herein, the usability of 99mTc-spermine for human breast tumor imaging was further evaluated.

Methods The biodistribution study of 99mTc-spermine was performed in mice bearing MDA-MB-231 human breast carcinoma. SPECT images of mice bearing tumors were also acquired at 1h postinjection with the tracer. 99mTc-MIBI was used for comparison.

Results Tumor uptake of 99mTc-spermine decreased as a function of time from 1.67±0.36 %ID/g at 30min to 1.10±0.18%ID/g at 120 min postinjection, and was significantly higher than that of 99mTc-MIBI at 60min postinjection. Tumor to blood and tumor to muscle uptake ratios of 99mTc-spermine and 99mTc-MIBI were 5.89±1.06 ,8.02±1.29 and 4.14±0.54, 5.61±0.72 at 60min postinjection respectively. Meanwhile, radioactivity accumulations in hearts were significantly lower for 99mTc-spermine than 99mTc-MIBI respectively at the same time point. In line with the biodistribution study, tumor was imaged clearly, and radiotracer accumulation was also displayed in the kidneys and liver after injection with 99mTc-spermine. Lower radio activities of 99mTc-spermine were observed in chest region than 99mTc-MIBI. The tumor to backgrounds of 99mTc-spermine and 99mTc-MIBI were 3.07±0.78 and 1.56±0.34 respectively.

Conclusions 99mTc-spermine has potential for the in vivo imaging of breast tumor. The application of 99mTc-spermine in diagnosis of different kinds of breast tumors is expected to explore.

Research Support This work was partially supported by National Natural Science Foundation (81171399 and 81101077,2012ZX09505-001-001), Jiangsu Province Foundation (BE2012622, BK2011166,BL2012031,RC2011095), CSC Foundation (2011832173).Health Ministry of Jiangsu Province Fund (RC2011095 and H201028)