Breast Cancer: Targets and Therapy (Jul 2019)
Chloroquine sensitizes MDA-MB-231 cells to osimertinib through autophagy–apoptosis crosstalk pathway
Abstract
Brett Fleisher, Hardik Mody, Carolin Werkman, Sihem Ait-OudhiaCenter for Pharmacometrics and Systems Pharmacology, Department of Pharmaceutics, College of Pharmacy, University of Florida, Orlando, FL, USABackground: Triple-negative breast cancer (TNBC) is a breast cancer that tests negative for estrogen receptor (ER), progesterone receptors, and human epidermal growth factor receptors 2 (HER2). It is aggressive and invasive in nature and lacks targeted therapy.Purpose: The EGFR is frequently overexpressed in TNBC, and the EGFR-overexpressing TNBC presumably escapes EGFR inhibitor therapy by upregulating autophagy and inhibiting apoptosis.Methods: To parse the autophagy–apoptosis crosstalk pathway as a potential targeted therapy in TNBC, the activity of an EGFR inhibitor, osimertinib, alone and in combination with an autophagy inhibitor, chloroquine, was examined in EGFR-overexpressing TNBC cell line, MDA-MB-231. The nature of interaction between both drugs at various concentrations was determined by calculating combination indexes (CI) using CompuSyn software. Temporal changes in the expression of the autophagy marker, LC3B-II, and several apoptosis signaling molecules were measured using Western blot and luminex assay with MAGPIX®, after exposure to drugs. A synergistic interaction (CI <1) was identified with combinations of 4–6.5 μM osimertinib with 30–75 μM chloroquine.Results: A combination of osimertinib (6 μM) with chloroquine (30 μM) resulted in a 6-fold increase of LC3B-II relative to control compared to 2.5-fold increase for either drug alone. The caspase-3 expression increased 2-fold compared to a 0.5-fold decrease with chloroquine and 1.5-fold increase with osimertinib.Conclusion: Our results indicate that inhibition of the autophagic flux via chloroquine improves the effectiveness of osimertinib in TNBC cancer cells, warranting further investigations of this combination in vivo.Keywords: EGFR inhibitor, drug-drug interaction, autophagic flux, programed cell death, synergy
