Estudi de la inhibició de la sintasa d'àcids grassos (FASN) per revertir la resistència al gefitinib en adenocarcinoma de pulmó

Abstract

Lung cancer is the most common cancer and the leading cause of cancer death worldwide. Lung adenocarcinoma is the most frequent type of non-small cell lung cancer (NSCLC) and the one with a higher incidence in non-smokers. The Epidermal Growth Factor Receptor (EGFR) may harbor activating mutations on tyrosine kinase domain, which trigger loss of growth control through sustaining activation of EGFR-related signaling pathways. In these cases, epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI), such as gefitinib are administrated. Thus, EGFRTKI selectively blocks tumor cell signal transduction. However, a secondary mutation in EGFR can provide resistance to EGFR-TKI in tumor cells. This situation has led to search for alternatives to slow down the progression of resistant cells. A promising target to do so is fatty acid synthase (FASN), an overexpressed enzyme in tumor cells that synthesize fatty acids de novo, instead of acquiring them from the diet. FASN inhibition allows to reduce the energy contribution that helps to get the excessive growth of the cell. In order to overcome resistance to gefitinib, the objective of this project is to analyze in vitro the effect of gefitinib and G28, a FASN inhibitor, on PC9 cell line and on three PC9-derived cell lines resistant to gefitinib: PC9-GR1 and PC9-GR4, both carrying T790M secondary mutation, and PC9- GR3. It has been studied the effect of gefitinib and G28 on the expression levels of EGFR and FASN, their respective targets, by Western Blot analysis. Also, it has been evaluated the effect of these drugs on apoptosis induction (PARP cleavage) and on key proteins of the PI3K/AKT and the Ras/MAPK signaling pathways. To do so, treatments with the IC50 of each drug for 72 hours and with ten times IC50 for 24 hours have been performed. Generally, the results obtained show that gefitinib reduces phosphorylation of EGFR and induces apoptosis in all cell lines. Gefitinib blocks EGFR-derived signaling pathways in all cell lines, in 24- hour treatment. The G28 treatment clearly diminishes FASN levels and induces apoptosis in all cell lines. The 24- hour treatment reduces EGFR activation, that inhibits its related signaling pathways in all PC9 resistant cell lines