FGFR1 and lung cancer: In order to study different mechanisms of resistance to FGFR1 inhibition in lung cancer cells, we compared the two lung cancer cell lines NCI-H1581 and NCI-H520, both of which harbor an FGFR1 gene amplification and a corresponding overexpression of FGFR1 RNA and protein (Fig. 1a and S1a, b).