Diosgenyl Saponin Inducing Endoplasmic Reticulum Stress and Mitochondria-Mediated Apoptotic Pathways in Liver Cancer Cells

Abstract

Diosgenin and diosgenyl saponins as the major bioactive compounds isolated from dietary fenugreek seeds, yam roots, etc. possessed strong antitumor effects. To understand their detailed antitumor mechanisms, a fluorophore-appended derivative of diosgenin [Glc/CNHphth-diosgenin (GND)] was synthesized, starting from diosgenin and glucosamine hydrochloride in overall yields of 7-12% over 7-10 steps. Co-localization of GND with organelle-specific stains, transmission electron microscopy, and relative protein analyses demonstrated that GND crossed the plasma membrane through organic anion-transporting polypeptide 1B1 and distributed in the endoplasmic reticulum (ER), lysosome, and mitochondria. In this process, GND induced ER swelling, mitochondrial damage, and autophagosome and upregulating IRE-1α to induce autophagy and apoptosis. Furthermore, autophagy inhibitor chloroquine delayed the appearance of cleaved poly(ADP-ribose) polymerase and inhibited cleaved caspase 8, which indicated that GND induced autophagy to activate caspase-8-dependent apoptosis. These observations suggested that diosgenyl saponin was a potent anticancer agent that elicited ER stress and mitochondria-mediated apoptotic pathways in liver cancer.

Keywords: IRE-1α; OATP1B1; apoptosis; diosgenin; endoplasmic reticulum stress; hepatocellular carcinoma.