As shown in Fig. 5b, when compared with normal levels, the mRNA levels of EGFR, IGF1 and MAPK1 were decreased significantly in stages one to four BC tissues, while the expression levels of AKT1, ESR1, HSP90AA1, CASP3, SRC, and MDM2 were increased significantly, with the exception of the levels of HSP90AA1 and MDM2, which were not significantly increased in stage four BC tissues. The gene discussed is ESR1; the disease is breast cancer.