MAP2K1 and breast cancer: To determine whether PDGFRβ signaling blockade enhances the growth-inhibitory effect of combined MEK1/2-JAK2 inhibition (AZD6244/AZD1480) in basal-like breast cancer cells in vivo, we first tested the combination therapy using a human cell line, MDA-MB-231 xenografts in immunocompromised nude mice.