MAPK3 and breast cancer: To validate the RPPA data showing potential PI3K and MAPK pathway inhibition by miR-564, we examined AKT and ERK1/2 phosphorylation levels in miR-564 transfected MDA-MB-231 and MCF-7 cells, which represent triple negative breast cancer (TNBC) and estrogen receptor positive (ER+) breast cancer subtypes, respectively.