KDM4B is a histone demethylase which is upregulated in ERα+ breast tumors and can regulate the expression of both ERα and FOXA1 as well as modulate ERα and p53 signaling [61–64], ERBB4/HER4 is critical for progesterone receptor (PR) expression [65] and has also been suggested to be responsible for promoting an autocrine proliferation pathway induced by estrogen [66, 67]. The gene discussed is ESR1; the disease is breast neoplasm.