PR also mediates progesterone's effects on breast cancer development and progression by activating the Src/ERK1/2 or PI3K/Akt pathways (Saitoh et al., 2005; Fu et al., 2008), which leads to activation of the transcription factor Elk-1 and consequent changes in gene expression (Boonyaratanakornkit et al., 2008). The gene discussed is PGR; the disease is breast cancer.