In addition, significantly higher tumor uptake of 68Ga-NOTA-G3-NGR in CD13-positive HT-1080 tumors versus CD13-negative HT-29 tumors, and effective blocking in HT-1080 tumors were observed, demonstrating that 68Ga-NOTA-G3-NGR is indeed a CD13-specific PET probe. Here, ANPEP is linked to neoplasm.