GRP and breast cancer: Santos-Cevas [114] designed a hybrid combination consisting of a peptide derived from HIV Tat and bombesin ((99m)Tc-N(2)-Tat(49-57)-Lys3-bombesin; (99m)Tc-Tat-BN), which was evaluated in prostate cancer cell lines, but also in breast cancer cell lines MDA-MB231 and MCF7 in vitro.