Clear cell renal cell carcinoma (ccRCC) is characterized by large intracellular lipid droplets containing free and esterified cholesterol; however, the functional significance of cholesterol accumulation in ccRCC cells is unknown. We demonstrate that, surprisingly, genes encoding cholesterol biosynthetic enzymes are repressed in ccRCC, suggesting a dependency on exogenous cholesterol. Mendelian randomization analyses based on 31,000 individuals indicate a causal link between elevated circulating high-density lipoprotein (HDL) cholesterol and ccRCC risk. Depriving ccRCC cells of either cholesterol or HDL compromises proliferation and survival in vitro and tumor growth in vivo; in contrast, elevated dietary cholesterol promotes tumor growth. Scavenger Receptor B1 (SCARB1) is uniquely required for cholesterol import, and inhibiting SCARB1 is sufficient to cause ccRCC cell-cycle arrest, apoptosis, elevated intracellular reactive oxygen species levels, and decreased PI3K/AKT signaling. Collectively, we reveal a cholesterol dependency in ccRCC and implicate SCARB1 as a novel therapeutic target for treating kidney cancer.Significance: We demonstrate that ccRCC cells are auxotrophic for exogenous cholesterol to maintain PI3K/AKT signaling pathway and ROS homeostasis. Blocking cholesterol import through the HDL transporter SCARB1 compromises ccRCC cell survival and tumor growth, suggesting a novel pharmacologic target for this disease.This article is highlighted in the In This Issue feature, p. 2945

Polycystic ovary syndrome (PCOS) is the most prevalent endocrinopathy in women. A common symptom of PCOS is hyperandrogenism (AE); however, the source of these androgens is uncertain. Aldo-keto reductase family 1 member C3 (AKR1C3) catalyzes the formation of testosterone (T) and 5α-dihydrotestosterone (DHT) in peripheral tissues, which activate the androgen receptor (AR). AKR1C3 is induced by insulin in adipocytes and may be central in driving the AE in PCOS. We elucidated the conversion of both classical and 11-oxygenated androgens to potent androgens in a model of PCOS adipocytes. Using high-performance liquid chromatography (HPLC) discontinuous kinetic assays to measure product formation by recombinant AKR1C3, we found that the conversion of 11-keto-Δ4-androstene-3,17-dione (11K-4AD) to 11-ketotestosterone (11K-T) and 11-keto-5α-androstane-3,17-dione (11K-5AD) to 11-keto-5α-dihydrotestosterone (11K-DHT) were superior to the formation of T and DHT. We utilized a stable isotope dilution liquid chromatography high resolution mass spectrometric (SID-LC-HRMS) assay for the quantification of both classical and 11-oxygenated androgens in differentiated Simpson-Golabi-Behmel syndrome adipocytes in which AKR1C3 was induced by insulin. Adipocytes were treated with adrenal derived 11β-hydroxy-Δ4-androstene-3,17-dione (11β-OH-4AD), 11K-4AD, or Δ4-androstene-3,17-dione (4AD). The conversion of 11β-OH-4AD and 11K-4AD to 11K-T required AKR1C3. We also found that once 11K-T is formed, it is inactivated to 11β-hydroxy-testosterone (11β-OH-T) by 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1). Our data reveal a unique role for HSD11B1 in protecting the AR from AE. We conclude that the 11-oxygenated androgens formed in adipocytes may contribute to the hyperandrogenic profile of PCOS women and that AKR1C3 is a potential therapeutic target to mitigate the AE of PCOS.

Friedreich’s ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a triplet guanine-adenine-adenine (GAA) repeat expansion in intron 1 of the FXN gene, which leads to decreased levels of the frataxin protein. Frataxin is involved in the formation of iron-sulfur (Fe-S) cluster prosthetic groups for various metabolic enzymes. To provide a better understanding of the metabolic status of patients with FRDA, here we used patient-derived fibroblast cells as a surrogate tissue for metabolic and lipidomic profiling by liquid chromatography-high resolution mass spectrometry. We found elevated HMG-CoA and β-hydroxybutyrate-CoA levels, implying dysregulated fatty acid oxidation, which was further demonstrated by elevated acyl-carnitine levels. Lipidomic profiling identified dysregulated levels of several lipid classes in FRDA fibroblast cells when compared with non-FRDA fibroblast cells. For example, levels of several ceramides were significantly increased in FRDA fibroblast cells; these results positively correlated with the GAA repeat length and negatively correlated with the frataxin protein levels. Furthermore, stable isotope tracing experiments indicated increased ceramide synthesis, especially for long-chain fatty acid-ceramides, in FRDA fibroblast cells compared with ceramide synthesis in healthy control fibroblast cells. In addition, PUFA-containing triglycerides and phosphatidylglycerols were enriched in FRDA fibroblast cells and negatively correlated with frataxin levels, suggesting lipid remodeling as a result of FXN deficiency. Altogether, we demonstrate patient-derived fibroblast cells exhibited dysregulated metabolic capabilities, and their lipid dysfunction predicted the severity of FRDA, making them a useful surrogate to study the metabolic status in FRDA.

Solid tumors possess heterogeneous metabolic microenvironments where oxygen and nutrient availability are plentiful (fertile regions) or scarce (arid regions). While cancer cells residing in fertile regions proliferate rapidly, most cancer cells in vivo reside in arid regions and exhibit a slow-cycling state that renders them chemoresistant. Here, we developed an in vitro system enabling systematic comparison between these populations via transcriptome analysis, metabolomic profiling, and whole-genome CRISPR screening. Metabolic deprivation led to pronounced transcriptional and metabolic reprogramming, resulting in decreased anabolic activities and distinct vulnerabilities. Reductions in anabolic, energy-consuming activities, particularly cell proliferation, were not simply byproducts of the metabolic challenge, but rather essential adaptations. Mechanistically, Bcl-xL played a central role in the adaptation to nutrient and oxygen deprivation. In this setting, Bcl-xL protected quiescent cells from the lethal effects of cell-cycle entry in the absence of adequate nutrients. Moreover, inhibition of Bcl-xL combined with traditional chemotherapy had a synergistic antitumor effect that targeted cycling cells. Bcl-xL expression was strongly associated with poor patient survival despite being confined to the slow-cycling fraction of human pancreatic cancer cells. These findings provide a rationale for combining traditional cancer therapies that target rapidly cycling cells with those that target quiescent, chemoresistant cells associated with nutrient and oxygen deprivation. Significance: The majority of pancreatic cancer cells inhabit nutrient- and oxygen-poor tumor regions and require Bcl-xL for their survival, providing a compelling antitumor metabolic strategy.