The EGFR-mutant NSCLC cell lines, HCC827, PC-9 and gefitinib-resistant PC-9/GR (T790M), were provided by Dr. P. A. Jänne (Dana Faber Cancer Institute, Boston, MA) in 2009. The EGFR-wild type NSCLC cell lines, H226 and H596, were originally obtained from Dr. R. Lotan (M. D. Anderson Cancer Center, Houston, TX) in 2003. Erlotinib-resistant HCC827/ER and AZD9291-resistant HCC827/AR cell lines were established in our laboratory and described previously (14 (link),17 (link)). The AZD9291-resistant cell lines, PC-9/AR and PC-9/GR/AR, were newly established in our laboratory by exposing PC-9 or PC-9/GR cells to gradually increasing concentrations of AZD9291 (starting at 10 nM and ending with 500 nM) for approximately 6 months (Fig. S1). These cell lines were routinely cultured in the presence of 500 nM AZD9291 and maintained resistance to AZD9291 even after withdrawal of AZD9291 from the culture medium for over 6 months, indicating an irreversible phenotype. MET gene amplification and protein hyperactivation were detected in HCC827/ER and HCC827/AR cells (14 (link)). Using ICE COLD-PCR developed by Transgenomic, Inc (Omaha, NE), EGFR exon 20 T790M mutation was detected in PC-9/GR/AR cells. However, C797S mutation in EGFR exon 20 and other mutations around codon C797S region and in EGFR exon 21 were not detected in HCC827/AR, PC-9/AR and PC-9/GR/AR cells (Fig. S1). Moreover, no K-RAS exon 2 mutations were detected in these cell lines. HCC827/Mcl-1 and PC-9/Mcl-1 stable cell lines (pooled populations) were generated by infecting cells with lentiviruses carrying ectopic Mcl-1 or vector for 48 h followed with selection with zeocin (500 ng/ml) for another 7 days as described previously (18 (link)). PC-9 cell line with EGFR 19del+T790M+C797S triple mutation used in a previous study (12 (link))(we named it PC-9/3M) was kindly provided by Dr. A. N. Hata (Harvard Medical School, Boston, MA) on January of 2017. This cell line was resistant to AZD9291 as well as CO1686 and erlotinib (Fig. S2), thus confirming its resistance to these EGFR inhibitors. These cell lines were not genetically authenticated. Mycoplasma was detected annually or upon receiving using MycoAlert@ Mycoplasma Detection Kit (Lonza; Rockland, ME) to ensure mycoplasma negative. All cell lines were cultured in RPMI 1640 containing 5% fetal bovine serum at 37 °C in a humidified atmosphere of 5% CO2 and 95% air.