Our previous studies reported that docosahexaenoic acid (DHA) induces autophagy through p53 inhibition in the wild-type p53 cancer cells. This study attempts to elucidate the molecular mechanism underlying DHA-induced autophagy in PC3 and DU145 prostate cancer cells harboring mutant p53. DHA increased both the level of microtubule-associated protein light-chain 3 (LC3) and the number of autophagic vacuoles. Autophagic flux assay confirmed that DHA-induced increase in LC3-II and autophagic vesicles was an outcome of autophagic process activation, indicating that DHA also induces autophagy in p53 mutant cancer cells. DHA treatment also increased the level of reactive oxygen species (ROS) as measured by dihydroethidine staining, and pretreatment of an antioxidant, N-acetylcysteine (NAC), significantly inhibited the ROS production as well as autophagy induced by DHA, suggesting that ROS regulates the autophagic process triggered by DHA. Further experiments showed that the mechanism of DHA-induced autophagy associated with ROS production was related to a decrease in the activity of mammalian target of rapamycin (mTOR). NAC remarkably restored the decreases in the levels of phospho-mTOR and 4EBP, an mTOR downstream molecule, induced by DHA as analyzed by the Western blot assay. Furthermore, the level of phospho-AMPK, which negatively regulates mTOR was increased, while phospho-Akt was reduced during the DHA-induced autophagy, indicating the involvement of AMPK and Akt signalings. Collectively, our results demonstrate that DHA induces autophagy through the ROS-mediated mTOR inactivation in p53 mutant prostate cancer cells. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2011-0006232].

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4654. doi:1538-7445.AM2012-4654