Abstract 4801: Laurine acid enhances GEM-chemosensitivity targeting hypoxia-induced mitochondrial disfunction and stemness in pancreatic ductal adenocarcinoma
Authors: Takagi Tadataka , Kuniyasu Hiroki , Sho Masayuki , Tani Rina , Mori Shiori , Kishi Shingo , Nishiguchi Yukiko , Hojo Yudai 
Published: April 2023

Hypoxia is a feature of the pancreatic ductal adenocarcinoma (PDA). Although gemcitabine (GEM) is widely used in chemotherapy for PDA, drug resistance restricts its clinical effectiveness. We have found that hypoxia contributes to chemoresistance, however the mechanism is still unclear. The aim of this study is to clarify the mechanism and to develop a new therapeutic strategy. First, we examined the effect of hypoxia to GEM sensitivity, stemness and energy metabolism in three human pancreatic ductal carcinoma cell lines. The inhibition rate by GEM was lower under CoCl2-induced chemical hypoxia than normoxia. Reactive oxygen species (ROS) after GEM was increased under normoxia but not under hypoxia. Flux analysis showed that both oxidative phosphorylation (OXPHOS) and glycolysis were suppressed under hypoxia, indicating a quiescent state. Next, we investigated the relationship between hypoxia and stemness. Hypoxia increased stem cell markers mRNA (C-Myc, Oct-3/4, CD24, CD44, CD133) expression and tumorsphere formation efficiency (TFE). In addition, hypoxia and GEM administration reduced sphere size but increased the number of spheres and TFE. This indicated that hypoxia and GEM suppressed proliferation, however promoted stemness. Second, to examine the mechanism of GEM resistance, we established two GEM-resistant cell lines from human PDA cells by continuous treatment with GEM and CoCl2-induced chemical hypoxia. One resistant cell line possessed reduced OXPHOS and decreased mitochondrial ROS levels, while the other resistant cell line possessed increased stemness. In both cell lines, ethidium bromide-stained mitochondrial DNA levels decreased, suggesting mitochondrial DNA damage. In addition, tetramethylrhodamine-stained mitochondrial membrane potential levels decreased, suggesting mitochondrial impairment. This indicated that long hypoxia and treatment with GEM induced mitochondrial impairment and acquisition of stemness, causing chemoresistance. We further investigated the effect of lauric acid (LAA), a medium-chain fatty acid, on GEM resistance. We have previously reported that LAA causes reprogramming of energy metabolism and induces cell death in cancer cells. Treatment with LAA restored GEM sensitivity in both GEM-resistant cell lines. Flux analysis showed that both OXPHOS and glycolysis were promoted, indicating displacement from quiescent state by LAA. These results suggest that decreased energy production, decreased mitochondrial ROS levels, and increased stemness associated with mitochondrial damage caused by GEM lead to GEM resistance, and that hypoxia may promote this process. Furthermore, forced activation of OXPHOS by LAA could be a tool to overcome GEM resistance.

Citation Format: Tadataka Takagi, Hiroki Kuniyasu, Masayuki Sho, Rina Tani, Shiori Mori, Shingo Kishi, Yukiko Nishiguchi, Yudai Hojo. Laurine acid enhances GEM-chemosensitivity targeting hypoxia-induced mitochondrial disfunction and stemness in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4801.