Advanced genomic approaches have identified the presence of a genetic fusion between fibroblast growth factor receptor 3 (FGFR3) and transforming acidic coiled-coil 3 (TACC3) in non-small cell lung cancer (NSCLC), providing a novel target for FGFR inhibition.
These 5 cases of FGFR3-TACC3 fusions acquired post-EGFR TKI, while rare, indicate that FGFR3-TACC3 is a recurrent resistance mechanism, which can bypass EGFR blockade by all generations of EGFR TKIs in NSCLC.
Thus, this advanced EGFR-mutated NSCLC displayed very rapid onset and heterogeneous genetic and phenotypic mechanisms of TKI-resistance occurring at different times and locations of metastatic disease: concomitant FGFR3-mutation before and during TKI-treatment as potential intrinsic mechanism for the rapid progression; transformation to SCLC at first progression during TKI-therapy; acquired T790M EGFR-mutation at second progression.
Fibroblast growth factors (FGF) are expressed in many non-small cell lung carcinoma (NSCLC) primary tumors and derived cell lines, and mutations in FGF receptor 3 (FGFR3) have been identified in human lung adenocarcinoma.
Analysis of gefitinib action on a larger panel of NSCLC cell lines verified that FGFR2 and FGFR3 expression is increased at the mRNA and protein level in NSCLC cell lines in which the EGFR is dominant for growth signaling, but not in cell lines where EGFR signaling is absent.
The binding of exogenous nicotine to nicotinic acetylcholine (ACh) receptors (nAChR) and the binding of endogenous ACh to both nAChR and muscarinic ACh receptors (mAChR) stimulate growth of both small cell and non-small cell lung carcinomas.
In addition, SNaPshot multiplex assays (Applied Biosystems, Darmstadt, Germany) and restriction fragment length polymorphism analysis were used to screen for activating point mutations at the hot spots of FGFR3 in a cohort of 30 samples of NSCLC.