The antitumor natural compound falcarindiol promotes cancer cell death by inducing endoplasmic reticulum stress.
Falcarindiol (FAD) is a natural polyyne with various beneficial biological activities. We show here that FAD preferentially kills colon cancer cells but not normal colon epithelial cells. Furthermore, FAD inhibits tumor growth in a xenograft tumor model and exhibits strong synergistic killing of cancer cells with 5-fluorouracil, an approved cancer chemotherapeutic drug. We demonstrate that FAD-induced cell death is mediated by induction of endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR). Decreasing the level of ER stress, either by overexpressing the ER chaperone protein glucose-regulated protein 78 (GRP78) or by knockout of components of the UPR pathway, reduces FAD-induced apoptosis. In contrast, increasing the level of ER stress by knocking down GRP78 potentiates FAD-induced apoptosis. Finally, FAD-induced ER stress and apoptosis is correlated with the accumulation of ubiquitinated proteins, suggesting that FAD functions at least in part by interfering with proteasome function, leading to the accumulation of unfolded protein and induction of ER stress. Consistent with this, inhibition of protein synthesis by cycloheximide significantly decreases the accumulation of ubiquitinated proteins and blocks FAD-induced ER stress and cell death. Taken together, our study shows that FAD is a potential new anticancer agent that exerts its activity through inducing ER stress and apoptosis.
Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637, USA.
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D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy; D053280:Diynes / Q000627:therapeutic use / Q000633:toxicity*; D004357:Drug Synergism; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005233:Fatty Alcohols / Q000627:therapeutic use / Q000633:toxicity*; D005472:Fluorouracil / Q000633:toxicity; D045325:HCT116 Cells; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D014183:Transplantation, Heterologous; D054875:Ubiquitination / Q000187:drug effects; D056811:Unfolded Protein Response / Q000187:drug effects
D000972:Antineoplastic Agents, Phytogenic; D053280:Diynes; D000091342:Endoplasmic Reticulum Chaperone BiP; D005233:Fatty Alcohols; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; C034379:falcarindiol; D005472:Fluorouracil