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). Here, FGFR2 is linked to lung cancer.