GNRH1 and cancer: In some human cancer cell models GnRH II(GNRH2, O43555) is more potent than GnRH I (GNRH1, P01148), implying mediation by GnRH2 receptors [690], but GnRH2 receptors are not expressed by humans because the human GNRHR2 gene contains a frame shift and internal stop codon [1377].