Abstract 4377: Liver X receptor mediated lipotoxicity represents a treatment option for liver cancer
Authors: Rudalska Ramona , Harbig Jule , Snaebjoernsson Marteinn , Taranets Lyudmyla , Heinzmann Florian , Zwirner Stefan , Hu Wei Ciu , Kronenberger Thales , Kang Tae-Won , Poso Antti , Laufer Stefan , Rosenfeldt Mathias , Malek Nisar P. , Pichler Bernd , Popov Nikita , Schulze Almut , Zender Lars , Dauch Daniel 
Published: August 2019

Abstract
Solid tumors evolve significant changes in metabolic pathways during development by virtue of their specific biosynthetic demands, their particular microenvironment and the potential occurrence of toxic metabolites such as reactive oxygen species. However, the development of cancer treatment approaches that are based on the inhibition of biosynthetic routes is impaired due to the high plasticity of metabolic networks, e.g. resulting in activation of compensatory pathways or in an increased exchange of metabolites between cancer cells and the tumor environment. Therefore, such therapies could not be translated into efficient clinical applications so far.
Here we show that an enhanced lipogenesis, triggered by a pharmacological activation of the Liver X receptor (LXR), represents a new therapeutic strategy for the treatment of liver carcinoma (HCC). A combination of LXR mediated fatty acid synthesis and concomitant Raf suppression results in oxidative stress, induction of a critical ER stress response and subsequently in apoptosis of different murine and human liver cancer cells. Our mechanistic studies identified Raf as an important regulator of lipid metabolism in liver cancer. We found that Raf-1 directly interacts with Stearoyl-CoA desaturase-1 (Scd1), the central enzyme for the conversion of saturated into mono-unsaturated fatty acids and thereby maintains Scd1 protein stability in HCC cells. Thus, inhibition of Raf by Sorafenib diminished Scd1 protein abundance leading to toxic accumulation of saturated fatty acids and metabolic stress in cancer cells under sustained lipogenesis. Treatment studies in autochthonous liver cancer mouse models and xenograft models of human HCC revealed that a combinatorial therapy, consisting of the LXR agonist T0901317 and Sorafenib is highly potent to suppress liver cancer development and to extend the survival of tumor bearing animals. Such a therapy was efficient against hepatic neoplasia with different metabolic phenotypes and well tolerated by mice, even by animals that already suffer from a fatty liver disease.
Taken together, we here propose a pharmacologically induced accumulation of toxic metabolites in cancer cells as a new strategy for efficient metabolic targeting of therapy refractory solid tumors.
Citation Format: Ramona Rudalska, Jule Harbig, Marteinn Snaebjoernsson, Lyudmyla Taranets, Florian Heinzmann, Stefan Zwirner, Wei Ciu Hu, Thales Kronenberger, Tae-Won Kang, Antti Poso, Stefan Laufer, Mathias Rosenfeldt, Nisar P. Malek, Bernd Pichler, Nikita Popov, Almut Schulze, Lars Zender, Daniel Dauch. Liver X receptor mediated lipotoxicity represents a treatment option for liver cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4377.