1979MO Inhibition of fatty acid synthase (FASN) activity induces cytotoxicity on gefitinib- and osimertinib-resistant EGFR-mutated non-small cell lung cancer cells

Lung cancer is the most diagnosed cancer and the first leading cause of cancer death worldwide. EGFR is mutated in roughly 10-30% of non-small cell lung cancer (NSCLC) patients. Although several EGFR tyrosine kinases inhibitors (TKI) are developed to treat tumours which possess an EGFR sensitizing mutation, primary and secondary resistance to EGFR TKIs arise due to different mechanisms, such as T790M mutation or hyperactivation of transducer and activator of transcription 3 (STAT3). We and other authors have described the overexpression of fatty acid synthase (FASN), an enzyme responsible for endogenous synthesis of long-chain fatty acids, as a resistance mechanism. Therefore, in this work we studied the effect of a novel FASN inhibitor compound AZ12756122 in EGFR mutated (EGFRm) NSCLC sensitive and resistant to EGFR-TKIs. Cell models used were EGFRm lung adenocarcinoma sensitive to EGFR-TKIs (PC9), two derived T790M+ gefitinib resistant models (PC9-GR1 and PC9-GR4) and T790M- cells resistant to both gefitinib and osimertinib (PC9-GR3). Cell proliferation was assessed through the MTT assay, FASN activity by counting radiolabelled fatty acids synthesized de novo, gene expression and signalling pathways related to FASN/EGFR were evaluated by means of qRT-PCR and Western blot, respectively. Besides, the interaction of AZ12756122 with EGFR TKIs (gefitinib or osimertinib) was determined in resistant cell models using the CompuSynTM software. AZ12756122 treatment showed a cytotoxic effect in all cell models analysed exhibiting a reduction of FASN activity, gene expression, and protein levels. Moreover, a decrease of phosphorylated levels of EGFR and STAT3 has been observed after AZ12756122 treatment in sensitive and gefitinib-resistant cell models. The combination of AZ12756122 with osimertinib exhibited synergistic effects in PC9-GR3 cell model. We show cytotoxic effect of the inhibition of FASN by AZ12756122 in EGFRm NSCLC cell models. Our results suggest the combinatorial inhibition of FASN/EGFR/STAT3 signalling pathway as a promising therapeutic option to overcome the resistance to EGFR TKI treatment for further in vivo experiments.