Bixin Prevents Colorectal Cancer Development through AMPK-Activated Endoplasmic Reticulum Stress

Chemicals isolated from natural products have been broadly applied in the treatment of colorectal cancer (CRC). Bixin, an apocarotenoid from the seeds of Bixa orellana, exerts multiple pharmacological properties, including neuroprotective, anti-inflammatory, cardioprotective, and antitumor effects; yet, the therapeutic effects of Bixin on CRC are still unknown. Here, we described that Bixin treatment significantly inhibited the proliferation and motility of two CRC cell lines (CaCO2 and SW480) in vitro and in vivo. In addition, Bixin administration has sensitized CRC cells to TNF-related apoptosis-inducing ligand- (TRAIL-) induced cell apoptosis. Moreover, we showed that Bixin treatment initiated the activation of PERK/eIF-2α signal in CaCO2 and SW480 cells, leading to endoplasmic reticulum stress-associated apoptosis. Pharmacological inhibition of AMP-activated protein kinase (AMPK) abrogated the Bixin-induced activation of protein kinase RNA-like endoplasmic reticulum kinase (PERK)/eukaryotic initiation factor 2 alpha (eIF-2α) pathway, as well as reversed the inhibitory effects of Bixin on CRC development. In conclusion, this study indicated that Bixin treatment inhibits the progression of CRC through activating the AMPK/PERK/eIF-2α pathway, providing a novel potential strategy for clinical prevention of CRC.