Noteworthy, the small peptide based on the wild-type sequence of the leptin binding site I (LDFI) synthetized by Andò and colleagues in 2015, by competing with leptin, blocks leptin/leptin receptor signaling and has shown important results in vitro and in vivo in several types of cancer, including breast, seminoma, and glioblastoma [83,171,174,211,238]. Here, LEP is linked to seminoma.