Quercetin Increases Expression of Membrane-TRAIL in Glioblastoma Cells Resulting in Apoptosis

Glioblastoma isocitrate dehydrogenase (IDH)-wild type (GBM) belongs to a deadly class of cancers with a limited number of effective therapies and a dismal prognosis. Quercetin is a natural flavonoid with proven anti-cancer effects. This study aimed to assess the effect of quercetin on recombinant human tumor necrosis factor-related apoptosis-inducing ligand (rhTRAIL)-mediated apoptosis in various GBM cells and control astrocytes.

Two astrocyte cell lines and three GBM cell lines, M059K, T98G, and A172, were treated with quercetin (±rhTRAIL), and the results were evaluated by Western blotting, confocal microscopy, and flow cytometry analyses.

Quercetin alone did not induce apoptosis in normal astrocytes. Surprisingly, quercetin alone induced apoptosis in all GBM cell lines through both the intrinsic and extrinsic pathways of apoptosis in a TRAIL-dependent manner. M059K were the most sensitive to quercetin-induced apoptosis, followed by T98G and A172. We determined that GBM cells possess endogenous membrane-TRAIL, and that quercetin, in a time- and concentration-dependent manner, increased the trafficking of membrane-TRAIL to the cell surface.

We demonstrate that quercetin alone induces apoptosis in GBM cell lines by facilitating endogenous membrane-TRAIL trafficking to the cell surface, where it can interact with death receptors already present on the surface of neighboring cancer cells, resulting in cell death. This unexpected finding may prove to be invaluable for potential future treatment of patients with GBM, since administration of quercetin can cause increased trafficking of membrane-TRAIL to the cell surface, inducing cancer cell apoptosis without affecting neighboring normal cells.