In 1999, the role of GRP as a stimulatory growth factor in human BC was further elucidated, by autoradiography studies performed with the radioiodinated bombesin analog [125I]I-Tyr4-BBN (please see the corresponding structure in Figure 3, yellow shadow), that exhibits high and specific GRPR affinity, and the universal [125I]I-dTyr6-βAla11-Phe13-Nle14-BBN (6–14), that binds to all four BBN receptor subtypes. Here, GRP is linked to breast cancer.