MAPK3 and ductal breast carcinoma in situ: After treatment with AP20187, both total ERK1/2 and p-ERK1/2 showed no changes in DCIS-Ctrl cells, while the levels of pERK1/2 were significantly increased in DCIS-iFGFR1 cell lines although total ERK1/2 levels remained the same (Fig. 1b).