MAPK3 and breast cancer: Previous studies have found that VEGFR2 phosphorylation could further stimulate ERK signaling in breast cancer cells, in which cell proliferation, migration, invasion, and differentiation are triggered by the phosphorylation and activation of the mitogen-activated protein kinases 1 and 2 (MEK1/2), which in turn phosphorylates and activates the extracellular signal-regulated kinases 1 and 2 (ERK1/2) [59,60].