Additionally, 17β-estradiol (E2) activates EGFR, thus stimulating the MEK1/2 and PI3K pathways and further increasing the expression of CIP2A/p90 through the MEK1/2-induced transcription factor Ets1 to enhance the proliferation of cancer cells (Choi et al., 2014). This evidence concerns the gene MAP2K1 and cancer.