The human breast cancer cell lines (MCF-7 and MDA-MB-231) with over-expressed GnRH receptors [25], [26], [27], HepG2 (human hepatoblastoma cells) with a low level of GnRH surface receptors [28] and HELF (human embryo lung fibroblasts), a cell line with no expression of GnRH receptor [29] were used in this study. This evidence concerns the gene GNRHR and breast cancer.