Pc 9 cells

HCC78 cells harboring the SLC34A2‐ROS1 fusion gene were kindly provided by Dr William Pao (Vanderbilt University, Nashville, TN, USA). ABC‐20 cells were established in our laboratory from pleural effusion obtained from a Japanese male former smoker who had lung adenocarcinoma harboring the CD74‐ROS1 fusion gene. The experiment regarding ABC‐20 cells was approved by the Institutional Review Board of Okayama University Hospital. Written informed consent was obtained from the patient. PC‐9 cells harboring EGFR 19 del E746_A750 were purchased from the European Collection of Cell Cultures (Salisbury, UK). 293T cells were purchased from the RIKEN Cell Bank (Ibaragi, Japan). Cells were cultured in RPMI 1640 medium (Sigma‐Aldrich, St. Louis, MO, USA) supplemented with 10% heat‐inactivated FBS and 1% penicillin/streptomycin in a tissue culture incubator at 37°C with 5% CO₂. To establish a crizotinib‐resistant cell line, HCC78 cells were treated with gradually increasing concentrations of crizotinib, starting at .2 μmol/L (lower than the IC₅₀ of HCC78 cells). After 4 months, the cells grew in the presence of 2 μmol/L crizotinib and were designated as HCC78R cells. HCC78R cells were maintained in culture medium containing 1 μmol/L crizotinib. The resistant cell lines were tested using the PowerPlex 16 STR System (Promega Corporation, Madison, WI, USA).