Defining the role of fatty acids in cetuximab resistance in squamous cell carcinoma of the head and neck

Details

Supervisors

Corbet, Cyril ; Larondelle, Yvan

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Treatment resistance has become a common issue in cancer management. Although new advances and the implementation of multi-modal approaches have resulted in improved responses in patients with head and neck cancer, more than half of all patients experience a clinical relapse within three years of treatment. The only targeted therapy approved by the FDA and EMA is cetuximab, an anti-Epidermal Growth Factor Receptor (EGFR) antibody. Lipid metabolism is increasingly described as a key player in the acquisition of resistance to targeted therapies. The aim of this master thesis is therefore to study lipid metabolism in resistant and sensitive FaDu (hypopharygeal cancer) cells and to use it as a therapeutic approach to try to overcome this resistance. All experiments were performed in both cell lines in order to compare them. Model of acquired resistance to cetuximab was established in the FATH pole. After the validation of the resistance with cell viability tests in 2D and on spheroids (3D models), we used the preliminary results acquired within Prof. Cyril Corbet's research team to continue the characterization of the lipid metabolism of the two lines via Western blots and gas chromatography. This second step allowed us to target some of the lipid metabolism enzymes with inhibitors. We also performed these analyses via cell viability assays. In parallel, we administered different families of fatty acids to the cells. These families include saturated, monounsaturated, polyunsaturated omega 3 and 6 fatty acids and conjugated linolenic acids. These analyses were performed via 2D cell viability assays and spheroid assays for the conjugated linolenic acid. Thanks to all these analyses, we observed a greater decrease in cell viability in resistant cells (versus cetuximab-sensitive parental cells) when certain inhibitors were added: carnitine palmitoyl transferase, a fatty acyl transporter from the cytosol to the mitochondria, or HMG-CoA reductase, an enzyme present in the mevalonate pathway. A stronger effect of DHA, DPA and PunA was also observed. All these compounds are therefore leads for potential therapeutic approaches to re-sensitize cetuximab-resistant cells. When we cultured resistant cells in the absence of fatty acids, they became sensitive to cetuximab, and the resistance was rescued when a mixture of fatty acids was added. Unfortunately, specific extracellular fatty acids failed to trigger this rescue. Other factors or combination of factors are needed to promote resistance. Further analysis will be required to confirm the results obtained and it would also be interesting to investigate other factors potentially capable of inducing resistance such as cells present in the tumour microenvironment which are increasingly being studied in the acquisition of resistance as they seem to be able to interact with cancer cells in different ways.