FGFR1 and breast cancer: Importantly, the cell lines that expressed the highest levels of FGFR1 expressed low levels of FGFR3 and were all relatively resistant to BGJ-398-induced growth arrest when the effects of the drug were measured early (48–72 h), strongly suggesting that FGFR3 is a more important driver of BC cell proliferation than FGFR1.