Fig. 5: Drug resistance and drug-sensitizing variants in EGFR.

a, Drug resistance variants to the EGFR inhibitor gefitinib, profiled with CBE and ABE base editors in PC9 lung cancer cells. Comparison of gRNA z-scores for the control treated arm versus plasmid library, and the drug-treated arm versus plasmid library is shown. b, Drug resistance variants to the EGFR inhibitor, osimertinib, profiled with CBE and ABE base editors in PC9 lung cancer cells. Comparison of gRNA z-scores for the control treated arm versus plasmid library, and the drug-treated arm versus plasmid library is shown. Data represent the average of two independent screens performed on separate days. c, Prime editing mutagenesis screens of EGFR in the presence and absence of osimertinib. PC9 ∆MLH1 cells were prime edited for 7 days with doxycycline (1 µg ml⁻¹) before growth for 10 days in DMSO (control) or osimertinib (75 nM). Data represent the z-score for each pegRNA derived from the average of two independent screens performed on separate days. Samples were compared with the plasmid library. d, Competition flow cytometry assays in PC9 ∆MLH1 cells comparing the growth of NT gRNA GFP cells with epegRNA BFP cells harboring different EGFR variants in the presence and absence of osimertinib (75 nM) for 5 days. Data are normalized to day 0 ratios and represent the mean ± s.d. of biological triplicates. Unpaired, two-tailed Student’s t-test comparing with the EGFR C797C synonymous variant control; *P = 0.0003, **P = 0.0002, ***p < 0.0001. Predicted amino acid editing consequences are labeled for drug resistance variant screens. See also Extended Data Fig. 5.