Abstract 632: AKT supports cancer cell survival through modulation of cholesterol homeostasis

Abstract

Abstract AKT is a critical effector kinase downstream of PI3K activation. It has been shown to regulate a variety of cellular processes important for homeostasis, many of which are altered during oncogenesis. Not surprisingly, AKT is constitutively activated in a large number of human cancers, and has consequently been pursued as a therapeutic target for many years. Some of these functions are directly involved in establishing one or more hallmarks of cancer including sustained proliferative signaling, resisting cell death, and reprogrammed cellular metabolism. Although AKT inhibitors have demonstrated clinical benefit (most recently in a phase III trial) in combination with other therapies, single agent activity has been limited to a few cases with relatively infrequent activating AKT1 mutations. We have previously proposed that the clear disconnect between the high frequency of AKT activation in cancer and the lack of broad clinical activity of AKT inhibitors is due, at least in part, to the inability of existing compounds to block non-catalytic functions. We have found that while allosteric AKT inhibitors are partial suppressors of these functions, ATP-competitive inhibitors fail to suppress these functions to any significant extent. We now provide evidence that one important non-catalytic function of AKT that impinges on its oncogenic function is the regulation of cholesterol metabolism. We show that AKT represses the activation of LXRβ, thereby maintaining a level of intracellular cholesterol that is compatible with cancer cell viability, and that this repression does not require catalytic activity. Consistently, we find that allosteric AKT inhibitors induce LXRβ activation, and that genetic or pharmacological suppression of LXRβ function limit the growth inhibiting effects of these drugs. Our findings suggest that through a kinase-independent activity, AKT may play a significant role in the regulation of cholesterol homeostasis, and that the therapeutic potential of AKT inhibitors could be broaden by optimizing their ability to interfere with these functions. Citation Format: Igor Vivanco, Khine N. Myint, Sean Wallace, Glorianne Lazaro, Eleftherios Kostaras, Nikolaos Palaskas. AKT supports cancer cell survival through modulation of cholesterol homeostasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 632.