Abstract 4651: Docosahexaenoic acid-induced degradation of epidermal growth factor receptor through lysosome and ubiquitin/proteasomal system in human non-small cell lung cancer cells
Authors: Jeong Soyeon , Jing Kaipeng , Shin Soyeon , Kim Soyeon , Jeon Young-Joo , Heo Jun-Young , Kweon Gi-Ryang , Park Seung-Kiel , Park Jong-Il , Lim Kyu 
Published: July 2016

Abstract
Mutations in EGFR gene frequently occurr in lung cancer and their expressions are related to poor prognosis and drug resistance. Although docosahexaenoic acid (DHA) has anti-cancer activity, the underlying mechanism is not well known in human non-small cell lung cancer (NSCLC) yet. In this study, we show a molecular mechanism of DHA-induced degradation of EGFR in human NSCLC cells. To determine whether DHA modulates EGFR degradation, we used three NSCLC cell lines, which is A549 (EGFR WT), and two mutant cells (PC9 and H1975). We confirmed that the viability of three lung cancer cells was decreased by DHA in a dose- and time-dependent manner. DHA augmented EGFR degradation and its ubiquitin in all three cell lines. Indeed, DHA increased the levels of E3-ligase, c-cbl and endosome-related molecules (Rab5, EEA1, Rab7, and LAMP1). Chloroquin (CQ) effectively blocked the DHA-induced EGFR degradation. Moreover, knockdown of lysosome associated membrane protein (LAMP) by its siRNAs, which regulates lysosome fusion, partially prevented EGFR degradation induced by DHA, and co-localization of EGFR with lysosome in immunocytochemistry, suggesting that DHA-induced EGFR degradation is associated with lysosomal degradation. On the other hand, MG132 (proteasome inhibitor) also protected DHA-triggered EGFR degradation, demonstrating that proteasomes also contribute to EGFR degradation in response to DHA treatment. To confirm the effects of endogenous ω3-PUFAs on EGFR degradation, fat-1-stablyexpressing A549 (f-A549) and PC9 cells (f-PC9) were established (The cells express a C. elegansω3-desaturase converting ω6- to ω3-PUFAs endogenously). The level of EGFR was reduced in f-A549 and f-PC9 cells, indicating ω3-PUFAs diminish EGFR level. The cell growth was retarded and the tumorigenicity was inhibited in nude mice. In addition, EGFR levels were significantly decreased in tumor tissues from f-A549 and f-PC9 cells-bearing mice. Taken together, DHA may induce the degradation of EGFR through lysosome and ubiquitin/proteosomal system in EGFR WT and EGFR mutant NSCLC cells. Thus, these findings provide important preclinical evidence and molecular insight for utilization of ω3-PUFAs in the chemoprevention and treatment of human NSCLC.[This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2007-0054932)]
Citation Format: Soyeon Jeong, Kaipeng Jing, Soyeon Shin, Soyeon Kim, Young-Joo Jeon, Jun-Young Heo, Gi-Ryang Kweon, Seung-Kiel Park, Jong-Il Park, Kyu Lim. Docosahexaenoic acid-induced degradation of epidermal growth factor receptor through lysosome and ubiquitin/proteasomal system in human non-small cell lung cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4651.