The impact of intermittent versus continuous exposure to EGFR tyrosine kinase inhibitor on selection of EGFR T790M-mutant drug-resistant clones in a lung cancer cell line carrying activating EGFR mutation.
Drug-resistant cell lines are essential tools for investigating the mechanisms of resistance to molecular-targeted anti-cancer drugs. However, little is known about how to establish clinically relevant drug-resistant cell lines. Our study examined the impact of a drug-free period on the establishment of a cell line with clinically relevant resistance to molecular-targeted drugs. We used PC9 cells, a lung cancer cell line carrying EGFR mutation, because this is a validated target for EGFR tyrosine kinase inhibitors (TKI). PC9 cells were intermittently or continuously exposed to increasing concentrations of gefitinib (0.01 μM to 1.0 μM) and the emergence of the most common acquired resistance mutation in EGFR, T790M, was determined. T790M was detected at a 25-fold lower drug concentration in cells continuously exposed to gefitinib (PC9/GRc) than in cells intermittently exposed to gefitinib (PC9/GRi) (0.04 μM vs 1.0 μM, respectively). The mutation frequencies at those drug concentrations were 19.8% and 8.0% in PC9/GRc and PC9/GRi cells, respectively. After drug-free culture for 8 weeks, resistance to gefitinib decreased in the PC9/GRi cells but not in the PC9/GRc cells. In the PC9/GRc cells, the frequency of the T790M mutation was consistently about 20% from 0.04 μM to 1.0 μM of gefitinib. In the PC9/GRc cells, the T790M mutation was detected in all single-cell clones, at frequencies ranging from 7.0% to 37.0%, with a median of 19.5% (95% confidence interval, 17.3%-20.9%). In conclusion, compared with intermittent drug exposure, continuous exposure might select better minor drug-resistant clones when creating cell lines resistant to molecular-targeted drugs.
Center for Lung Cancer, National Cancer Center, Goyang, Republic of Korea.|Lung Cancer Branch, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea.
Youngjoo
Y
Lee
Lung Cancer Branch, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea.
Yu-Ra
YR
Choi
Lung Cancer Branch, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea.
Kyoung-Yeon
KY
Kim
Lung Cancer Branch, Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea.
Dong Hoon
DH
Shin
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D018929:Cell Culture Techniques / Q000379:methods; D045744:Cell Line, Tumor; D004334:Drug Administration Schedule; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics*; D000073659:Gain of Function Mutation / Q000187:drug effects*; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use
D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; C512478:EGFR protein, human; D066246:ErbB Receptors; D000077156:Gefitinib
EGFR mutation; EGFR tyrosine kinase inhibitor; drug resistance; drug sensitivity; non-small-cell lung cancer