MAPK3 and breast cancer: FACS and immunoblot analysis revealed that abundances of intracellular ROS (Supplementary Figure S6), BLT1 and NOX4 proteins, and phosphorylated forms of Smad3 (Thr179 and Ser208), ERK1/2, and EGFR proteins (Figure 7A) were markedly greater in TGF-β1-resistant MDA-MB231 breast cancer cells compared with TGF-β1-responsive non-malignant MCF10A cells.