IGF1R and breast cancer: The binding specificity test indicated that the binding of 99mTc-ZIGF1R:4551-GGGC to IGF-1R-expressing cell lines (human prostate cancer cells DU-145 and human breast cancer cells MCF-7) was receptor mediated (Fig. 3), suggesting that labeling has not influenced the ability of ZIGF1R:4551-GGGC to bind specifically to IGF-1R.