To study the mechanism of FGFR1 signaling in human breast cancer progression, we generated DCIS-Ctrl control cell lines containing an empty vector and DCIS-iFGFR1 cell lines expressing the C-terminally HA-tagged iFGFR1 fusion protein (Fig. 1a). The gene discussed is FGFR1; the disease is ductal breast carcinoma in situ.