To explore the mechanisms underlying osimertinib resistance of NSCLC cells, HCC827/OR and PC-9/OR, two osimertinib-resistant cell lines, were established from parental osimertinib-sensitive HCC827 and PC-9 cells with EGFR mutation through the dose escalation method [23] (Supplementary Fig. 1A). The gene discussed is EGFR; the disease is non-small cell lung carcinoma.