FGFR1 and ductal breast carcinoma in situ: As predicted, the levels of phosphorylated ERK1/2 (p-ERK1/2), the downstream MAPKs of the FGFR1 signaling pathway, were increased in AP20187-treated DCIS-iFGFR1 cells (line #1) with HA-iFGFR1 protein expression but not in DCIS-Ctrl cells without HA-iFGFR1 protein expression, indicating that AP20187 treatment activated FGFR1 signaling in DCIS-iFGFR1 cells (Fig.