The demonstration that a GnRH analog is ineffective in inhibiting growth of breast cancer cell lines expressing high levels of the GnRH receptor, despite eliciting robust signalling, provides a valuable tool for determining the intracellular context which does (eg HEK 293 and WPE-1-NB26-8) or does not (breast cancer cell lines) facilitate anti-proliferative effects of GnRH signalling. Here, GNRH1 is linked to breast cancer.