Abstract PO037: Oxidized phosphatidylcholines induce tumorigenesis and metastasis through autophagy
Authors: Seok Jin Kyung , Hong Eun-Hee , Lee Joo Young 
Published: March 2021

Abstract
Increased levels of oxidized phosphatidylcholines have been observed in many diseases and act as damage-associated molecular patterns, mediating immune responses. However, the roles of oxidized phospholipids in tumor metastasis have not been entirely elucidated. By using western blotting and confocal fluorescence imaging of human breast cancer cells (MCF7) and hepatocellular carcinoma cells (HepG2), we found that 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) induces changes in EMT-marker expression with increased expression of relative transcription factors to promote the EMT process. POVPC treatment significantly increased the migration and invasion capabilities in cancer cell lines, including HepG2 cells, MCF7 cells, murine skin melanoma cells (B16F10), human colon cancer cells (HCT116), and murine mammary carcinoma cells (4T1). Oxidized phospholipids such as POVPC, 1-palmitoyl-2-glutaroyl-sn-glycero-phosphocholine (PGPC), and 1-palmitoyl-2-(5-keto-6-octenedioyl)-sn-glycero-3-phosphocholine (KOdiA-PC) treatment induced autophagic flux, while nonoxidized phospholipids do not have such abilities. To identify whether POVPC regulates cancer metastasis via autophagy pathways, cells were treated with the pharmacological inhibitors of autophagy, 3-MA or CQ, followed by treatment with POVPC. Autophagy inhibitors decreased pro-metastatic ability compared to POVPC alone. Because ATG5 or ATG7 are critical components of autophagy pathway, cells were transfected with siATG5 or siATG7, followed by treatment with POVPC. Knockdown of ATG5 or ATG7 restored the epithelial markers and decreased both migration and invasion capabilities compared to POVPC alone. Using an LC-MS/MS analysis, the levels of oxidized phosphatidylcholines including POVPC and PGPC did not change in 18 of patient-derived intrahepatic cholangiocarcinoma tissues compared to 18 of corresponding adjacent nontumor tissues; however, POVPC and PGPC levels were greatly higher at stage II of intrahepatic cholangiocarcinoma tissues. In 16 of human breast tumor tissues, the levels of PGPC were higher than those in 16 of adjacent nontumor tissues and 4 of benign tumor tissues. In patient-derived intrahepatic cholangiocarcinoma tissues and breast cancer tissues, the protein levels of autophagy markers were significantly higher compared to nontumor tissues throughout all stages. Together, these results show that oxidized phosphatidylcholines accumulated in the tumor microenvironment associate with the regulation of tumorigenesis and metastasis through autophagic flux.
Citation Format: Jin Kyung Seok, Eun-Hee Hong, Joo Young Lee. Oxidized phosphatidylcholines induce tumorigenesis and metastasis through autophagy [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PO037.