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  • Dual Inhibition of Autophagy and PI3K/AKT/MTOR Pathway as a Therapeutic Strategy in Head and Neck Squamous Cell Carcinoma.

Dual Inhibition of Autophagy and PI3K/AKT/MTOR Pathway as a Therapeutic Strategy in Head and Neck Squamous Cell Carcinoma.

Cancers (2020-08-23)
Monique Bernard, Guillaume B Cardin, Maxime Cahuzac, Tareck Ayad, Eric Bissada, Louis Guertin, Houda Bahig, Phuc Felix Nguyen-Tan, Edith Filion, Olivier Ballivy, Denis Soulieres, Francis Rodier, Apostolos Christopoulos
ABSTRACT

Genomic analyses of head and neck squamous cell carcinoma (HNSCC) have highlighted alterations in the phosphatidylinositol 3-kinase (PI3K) signaling pathway, presenting a therapeutic target for multiple ongoing clinical trials with PI3K or PI3K/MTOR inhibitors. However, these inhibitors can potentially increase autophagy in HNSCC and indirectly support cancer cell survival. Here, we sought to understand the relationship between the PI3K signaling pathway and autophagy during their dual inhibition in a panel of HNSCC cell lines. We used acridine orange staining, immunoblotting, and tandem sensor Red Fluorescent Protein- Green Fluorescent Protein-, microtubule-associated protein 1 light chain 3 beta (RFP-GFP-LC3B) expression analysis to show that PI3K inhibitors increase autophagosomes in HNSCC cells, but that chloroquine treatment effectively inhibits the autophagy that is induced by PI3K inhibitors. Using the Bliss independence model, we determined that the combination of chloroquine with PI3K inhibitors works in synergy to decrease cancer cell proliferation, independent of the PIK3CA status of the cell line. Our results indicate that a strategy focusing on autophagy inhibition enhances the efficacy of therapeutics already in clinical trials. Our results suggest a broader application for this combination therapy that can be promptly translated to in vivo studies.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ponceau S, BioReagent, suitable for electrophoresis
Sigma-Aldrich
Chloroquine diphosphate salt, powder or crystals, 98.5-101.0% (EP)
Sigma-Aldrich
Acridine Orange hydrochloride solution, ≥95.0% (HPLC), 10 mg/mL in H2O
Sigma-Aldrich
UM-SCC-22A Squamous Carcinoma Cell Line, UM-SCC-22A is a unique head and neck squamous carcinoma cell line obtained from the surgical resection of the primary cancer of the hypopharynx of a female patient and is a suitable in vitro model of H&N carcinoma studies.
Millipore
Protease Inhibitor Cocktail Set III, Animal-Free, Protease Inhibitor Cocktail Set III, Animal-Free, is a cocktail of six protease inhibitors with broad specificity for the inhibition of aspartic, cysteine & serine proteases & aminopeptidases.
Sigma-Aldrich
Bafilomycin A1 from Streptomyces griseus, ≥90% (HPLC)