GNRH1 and breast cancer: In particular, the conjugate GnRH-III-[2ΔHis,3d-Tic,4Lys(Bu),8Lys(Dau=Aoa)] (2) (Figure 1), where 2His was deleted and 3Trp was exchanged by the unnatural amino acid d-Tic (d-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid), was selected as the best candidate, displaying an improved inhibitory effect on the growth of colon and breast cancer cell lines in vitro [37].