Comparative global methylation profile in DMS114 cells before and after acquired resistance to PD173074. Comparative global methylation profile in DMS114 cells before and after acquired resistance to PD173074

The development of acquired resistance (AR) to tyrosine kinase inhibitors (TKIs) of FGFR1 activation is currently not well understood. To gain a deeper insight into this matter in lung cancer, we used the FGFR1-amplified DMS114 cell line and generated multiple clones with AR to an FGFR1-TKI. We molecularly scrutinized the resistant cells, using whole-exome sequencing, RNA sequencing and global DNA methylation analysis. Our results show a de novo activation of AKT and ERK, and a reactivation of mTOR. Furthermore, the resistant cells exhibited strong upregulation and activation of MET, indicating crosstalk between the FGFR1 and MET axes. The resistant cells also underwent a global decrease in promoter hypermethylation of the CpG islands. Finally, we observed clonal expansion of a pre-existing change in AKT1, leading to S266L substitution, within the kinase domain of AKT. Our results demonstrate that AR to FGFR1-TKI involves deep molecular changes that promote the activation of MET and AKT, coupled with common gene expression and DNA methylation profiles. The expansion of a substitution at AKT was the only shared genetic change, and this may have contributed to the AR. Overall design: The lung cancer cell line DMS114, which carries genetic activation of FGFR1, was used as a cancer cell model to investigate acquired resistance to FGFR1 tyrosine kinase inhibitors. We obtained three clones from the DMS114 parental cells that had become refractory to the inhibitor, PD173074 (DMS114-PR1, DMS114-PR3, DMS114-PR4).