In our present study using lung cancer cell lines, FGFR1 is most abundant receptor of the four family proteins in afatinib-resistant clones of PC9, and there was no enhancement in expression of other FGFR family proteins FGFR2, FGFR3 and FGFR4 (see Figure 4A). This evidence concerns the gene FGFR4 and lung carcinoma.