Since AKT and ERK1/2 were potently activated by HRG in three luminal breast cancer cell lines and they are known to induce tumor cell proliferation in other contexts [51], we investigated the effects of HRG on proliferation of HRG-treated versus untreated MDA-MB-361, MCF7 and SKBr3 cells. The gene discussed is MAPK3; the disease is breast cancer.