MAPK3 and breast cancer: The presence of a CREB inhibitor during LPA- treatment of SAE BC prevented LPA-induced expression of CTGF, EDN1, and PDGFB. Inhibitors of ERK1/2 and EGFR pathways failed to block LPA-induced expression of EDN1 or PDGFB although both blocked LPA-induced expression of CTGF. Since CREB inhibition covered the broadest range of LPA-stimulated activities, the effect of CREB inhibitor was assessed with respect to changing the pro-fibrotic character of the conditioned medium.