Vitto et al. Cancer & Metabolism (2020) 8:28 https://doi.org/10.1186/s40170-020-00234-5 RESEARCH Open Access Estrogen-related receptor alpha directly binds to p53 and cooperatively controls colon cancer growth through the regulation of mitochondrial biogenesis and function Humberto De Vitto1, Joohyun Ryu1, Ali Calderon-Aparicio1, Josh Monts1, Raja Dey1, Abhijit Chakraborty1, Mee-Hyun Lee2, Ann M. Bode1* and Zigang Dong2* Abstract Background: Of the genes that control mitochondrial biogenesis and function, ERRα emerges as a druggable metabolic target to be exploited for cancer therapy. Of the genes mutated in cancer, TP53 remains the most elusive to target. A clear understanding of how mitochondrial druggable targets can be accessed to exploit the underlying mechanism(s) explaining how p53-deficient tumors promote cell survival remains elusive. Methods: We performed protein-protein interaction studies to demonstrate that ERRα binds to p53. Moreover, we used gene silencing and pharmacological approaches in tandem with quantitative proteomics analysis by SWATH- MS to investigate the role of the ERRα/p53 complex in mitochondrial biogenesis and function in colon cancer. Finally, we designed in vitro and in vivo studies to investigate the possibility of targeting colon cancers that exhibit defects in p53. Results: Here, we are the first to identify a direct protein-protein interaction between the ligand-binding domain (LBD) of ERRα and the C-terminal domain (CTD) of p53. ERRα binds to p53 regardless of p53 mutational status. Furthermore, we show that the ERRα and p53 complex cooperatively control mitochondrial biogenesis and function. Targeting ERRα creates mitochondrial metabolic stresses, such as production of reactive oxygen species (ROS) and mitochondrial membrane permeabilization (MMP), leading to a greater cytotoxic effect that is dependent on the presence of p53. Pharmacological inhibition of ERRα impairs the growth of p53-deficient cells and of p53 mutant patient-derived colon xenografts (PDX). Conclusions: Therefore, our data suggest that by using the status of the p53 protein as a selection criterion, the ERRα/p53 transcriptional axis can be exploited as a metabolic vulnerability. Keywords: ERRα, p53-deficient, Mitochondrial biogenesis, Mitochondrial oxidative phosphorylation (mtOxPhos), PDX colon cancer model, Apoptosis * Correspondence: [email protected]; [email protected] 1The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin 55912, USA 2Department of Pathophysiology, Zhengzhou University School of Medicine, 40 North Road, 27 District University, Zhengzhou 450052, China © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Vitto et al. Cancer & Metabolism (2020) 8:28 Page 2 of 19 Background position of the full-length protein. These mutations pro- Reprogramming of energy metabolism is included in the vide several advantages for the mutant forms of p53, select list of biological hallmarks acquired during the de- such as a prolonged half-life and dominant negative ef- velopment of cancer [1, 2]. The adaptive metabolic re- fects of the mutant forms of p53 on the remaining wild- sponses make achieving clinical benefits difficult when type allele [35, 36]. Although, the p53 protein is one of targeting a single metabolic pathway [3–5]. Conversely, the most studied targets in cancer biology, the science therapeutically exploiting these metabolic liabilities can surrounding the role of p53 continues to intrigue scien- render cancer cells more susceptible to treatment with tists, especially the complexity of p53 protein status, potential and selective metabolic inhibitors [6–8]. For functions, and networks [35, 37]. instance, several researchers have suggested that target- The role of the p53 protein in inhibiting cell growth ing mitochondrial bioenergetics and function to over- by inducing cell cycle arrest and apoptosis is very well come drug resistance in cancer treatment could be established [38, 39]. Recently, the p53 protein has been therapeutically exploited, whereas the resistance mech- shown to influence multiple processes in metabolism, anism in cancer might be associated with a shift toward especially in response to metabolic stress [40–43]. Inter- an increased mtOxPhos status [9–14]. Mitochondrial estingly, targeting the mitochondrial uncoupling biogenesis is a key component of adaptive activities mechanism using niclosamide impaired the growth of needed for cancer cells to survive periods of metabolic p53-deficient cells and p53 mutant patient-derived ovar- stress [15, 16]. Therefore, mitochondrial turnover and ian xenografts [44]. Also, the status of the p53 protein mtOxPhos activity might be considered as metabolic re- (with GOF activity) has been shown to determine the quirements of tumor cells, and therefore, understanding p53’s ability to bind and regulate different protein net- the major regulators of mitochondrial biogenesis and works, which control tumor metabolism and metastasis function might guide the treatments that could be [45]. Indeed, the p53 mutant protein can drive the ex- exploited for effective cancer therapy. pression of key regulators of proliferation, invasion, and Given the importance of nuclear receptors (NRs) in metastasis through its binding with several transcription steroid, retinoid, and thyroid hormone signaling net- factors, such as Yes-associated protein (YAP), PGC-1α, works, hypothesizing that NRs are implicated in a wide and nuclear factor erythroid 2–related factor 2 (NRF2) range of pathologies is tempting [17]. Historically, NRs [46]. However, despite the advances in the discovery of serve as important targets for hormone therapies [18]. new functions of p53 that are dependent on the status of The estrogen-related receptor family (ERRα, ERRβ, and the protein [47, 48], the metabolic network of p53 inter- ERRγ) was first described as an orphan nuclear receptor actions with key regulators of mitochondrial metabolism family and was originally identified based on its hom- that lead to colon cancer cell survival has not yet been ology to estrogen receptor alpha (ERα)[19, 20]. Based determined. on Warburg’s prediction, cancer cells increase metabolic In this study, for the first time, we provide indirect requirements to sustain their proliferation [21]. ERRα is and direct evidence for the protein-protein interaction of emerging as a major transcription factor that regulates the ERRα LBD and the p53 CTD, which occurs inde- an extremely broad repertoire of mitochondrial and pendently of p53 status. Mechanistically, we describe in metabolic genes [12, 16, 22–27], making this druggable depth how the ERRα and p53 complex cooperatively protein very attractive for cancer treatment [28]. regulates mitochondrial biogenesis and mtOxPhos lead- The function of the ERRα and peroxisome ing to colon cancer cell survival. Notably, our study re- proliferator-activated receptor gamma coactivator 1- veals an unexpected metabolic vulnerability for targeting alpha (PGC-1α) transcriptional axis in the metabolic ERRα in p53-deficient (nonsense) cells compared to reprogramming of cancer cells toward mitochondrial wild-type p53 colon cancer cells. Because ERRα belongs metabolism in breast, melanoma, ovarian, prostate, and to a class of druggable NRs, our in vitro and in vivo colorectal tumors is well-known [12, 28–32]. However, studies suggest that the ERRα antagonist XCT790 might whether different transcriptional networks exist, whereby be considered as a potential drug to treat colon cancer ERRα could interact with important transcription factors patients with defective p53 status. (TFs) leading to the regulation of cancer metabolism and survival, is not clear. Results TP53 is known to be the most frequently altered gene ERRα directly binds to p53 in human cancer [33, 34]. Unlike other tumor suppres- The ERRα/PGC1α complex drives cancer cell survival sors, the vast majority of cancer-associated mutations in through mitochondrial metabolic programs favoring TP53 are missense mutations or gain-of-function (GOF) tumor development [28, 49, 50]. Moreover, the p53/ mutations leading to single base-pair substitutions (SNP) PGC1α complex drives tumor metabolism and metasta- in the translation of a different amino acid in that sis through mitochondrial energy programs enabling Vitto et al. Cancer & Metabolism (2020) 8:28 Page 3 of 19 mitochondria to cope with metabolic stress [45, 51]. p53 CTDΔ300-393 with a Flag tag. Next, we performed However, the ability of both ERRα and p53 to