Cholesterol selectively activates canonical Wnt signalling over non-canonical Wnt signalling

Novel LBR pathogenic variants with loss of sterol reductase activity participate in the pathogenesis of skeletal dysplasia via dysregulating canonical Wnt pathway

Biallelic pathogenic variants in the lamin B receptor (LBR) with impaired sterol reductase function are associated with the development of perinatal lethal Greenberg dysplasia (GRBGD) and mild nonfatal skeletal dysplasia with or without Pelger-Huet anomaly (PHASK), as well as other related hereditary skeletal dysplasia. However, the underlying molecular mechanism remains unclear. In this study, we found two novel pathogenic variants of LBR, namely missense mutation (c.1011 T > G, NM_002296.4; p.Cys337Trp, NP_002287.2) and LBR gene deletion (Chr1q42.12 (225,515,082-225,633,464), NC_000001.10). LBR is a novel substrate of FBW7, which is degraded by GSK3β/FBW7-mediated proteasome pathway and whose C337W mutation promotes its degradation through enhanced interaction with FBW7. Wild-type but not C337W mutant LBR is upregulated by WNT3A-mediated inactivation of GSK3β/FBW7 axis and then participated in WNT3A-activated Wnt pathway through its mediated cholesterol synthesis. MC3T3-E1 cells with Lbr knockdown or cholesterol removal exhibited reduced mineralized nodules in the presence of WNT3A, but addition of cholesterol in the culture medium reversed this phenotype. Collectively, we detected two novel variants in LBR and our study revealed for the first time that disruption of cholesterol synthesis by LBR impairs Wnt pathway and thus disrupts the cell osteogenic differentiation, providing new insights into the pathogenesis of skeletal dysplasia caused by LBR variation.

ABCG8‑mediated sterol efflux increases cancer cell progression via the LRP6/Wnt/β‑catenin signaling pathway in radiotherapy‑resistant MDA‑MB‑231 triple‑negative breast cancer cells

Expression levels of ATP‑binding cassette (ABC) transporters are known to be increased in various tumor cells, including in breast cancer, and they are responsible for mediating drug resistance, leading to treatment failure. In the present study, gene expression array analysis revealed that among ABC transporter subtypes, ABC subfamily G member 8 (ABCG8) was one of the most increased in radiotherapy‑resistant triple‑negative breast cancer (RT‑R‑TNBC) cells compared with in TNBC cells. ABCG8 is involved in sterol efflux; however, its role in cancer is not well known. Therefore, the present study investigated the effect of ABCG8 on tumor progression in RT‑R‑TNBC cells. Gene expression profiling was conducted using the QuantiSeq 3' mRNA‑Seq Service, followed by western blotting to confirm protein levels. Loss‑of‑function assays using small interfering RNA (si) transfection were performed to assess the roles of ABCG8 and its regulatory signaling pathways. RT‑R‑MDA‑MB‑231 cells exhibited increased cholesterol levels in both cells and the surrounding media via induction of sterol regulatory element binding protein 1 (mature form) and fatty acid synthase. siABCG8 transfection increased intracellular cholesterol levels but decreased cholesterol levels in the media, indicating an accumulation of cholesterol inside cells. Additionally, RT‑R‑MDA‑MB‑231 cells exhibited increased levels of β‑catenin compared with MDA‑MB‑231 cells, which was significantly reduced by ABCG8 knockdown. Furthermore, ABCG8 knockdown led to cell cycle arrest in the G2/M phase in RT‑R‑MDA‑MB‑231 cells by reducing Polo‑like kinase 1 (PLK1) and Cyclin B1 expression. RT‑R‑MDA‑MB‑231 cells also exhibited increased phosphorylated‑low‑density lipoprotein (LDL) receptor‑related protein 6 (LRP6) levels compared with MDA‑MB‑231 cells, and these were decreased by siABCG8 transfection. LRP6 siRNA transfection decreased β‑catenin, PLK1 and Cyclin B1 expression. In addition, feedback mechanisms such as liver X receptor and inducible degrader of LDL were decreased in RT‑R‑MDA‑MB‑231 cells under normal conditions compared with in MDA‑MB‑231 cells. To the best of our knowledge, the present study was the first to suggest that the cholesterol exported by ABCG8, not inside the cells, may affect cancer progression via the LRP6/Wnt/β‑catenin signaling pathway in RT‑R‑TNBC. The regulation of this pathway may offer a potential therapeutic strategy for the treatment of RT‑R‑TNBC.

Molecular architecture of human LYCHOS involved in lysosomal cholesterol signaling

Lysosomal membrane protein LYCHOS (lysosomal cholesterol signaling) translates cholesterol abundance to mammalian target of rapamycin activation. Here we report the 2.11-Å structure of human LYCHOS, revealing a unique fusion architecture comprising a G-protein-coupled receptor (GPCR)-like domain and a transporter domain that mediates homodimer assembly. The NhaA-fold transporter harbors a previously uncharacterized intramembrane Na+ pocket. The GPCR-like domain is stabilized, by analogy to canonical GPCRs, in an inactive state through 'tethered antagonism' by a lumenal loop and strong interactions at the cytosol side preventing the hallmark swing of the sixth transmembrane helix seen in active GPCRs. A cholesterol molecule and an associated docosahexaenoic acid (DHA)-phospholipid are entrapped between the transporter and GPCR-like domains, with the DHA-phospholipid occupying a pocket previously implicated in cholesterol sensing, indicating inter-domain coupling via dynamic lipid-protein interactions. Our work provides a high-resolution framework for functional investigations of the understudied LYCHOS protein.

Highly Branched Poly(β-amino ester)s for Efficient mRNA Delivery and Nebulization Treatment of Silicosis

mRNA therapeutics hold tremendous promise for disease prevention and treatment. Development of high-performance mRNA delivery systems with enhanced transfection efficiency and a safety profile will further fulfill their therapeutic potential and expedite their translation. The synthesis of "four-in-one" highly branched poly(β-amino ester)s (O-LhPAEs) is reported by integrating the essential components of lipid nanoparticles (LNPs) for spleen-selective mRNA enrichment and nebulization treatment of silicosis. 60 O-LhPAEs with distinct branched structure and chemical composition, including tertiary/quaternary amines, cholesterol moieties, zwitterionic species, and hydrophobic alkyl tails, are synthesized using sequential Michael addition, ring-opening, and nucleophilic substitution reactions. The unique topological structure and chemical composition collectively enhanced O-LhPAEs/mRNA polyplex serum resistance, cellular uptake, and endosomal escape. The optimal O-LhPAE, 20%b-3C-2P12, exhibits up to 93.1% mRNA transfection across 11 different cell types, including epithelial cells, fibroblasts, cancer cells, stem cells, neurological cells, and astrocytes. Biodistribution study reveals that 20%b-3C-2P12/mRNA polyplexes are mainly enriched in the spleen following systemic administration. Through nebulization, 20%b-3C-2P12 mediated high Tbx2 mRNA expression in the lungs of silicosis mice, effectively restoring lung functions. This study not only establishes a strategy for development of LNP-like O-LhPAEs but also provides promising candidates for highly safe, efficient, and spleen-selective mRNA delivery and nebulization treatment of silicosis.

Cholesterol-targeting Wnt-β-catenin signaling inhibitors for colorectal cancer

Most persons with colorectal cancer (CRC) carry adenomatous polyposis coli (APC) truncation leading to aberrant Wnt-β-catenin signaling; however, effective targeted therapy for them is lacking as the mechanism by which APC truncation drives CRC remains elusive. Here, we report that the cholesterol level in the inner leaflet of the plasma membrane (IPM) is elevated in all tested APC-truncated CRC cells, driving Wnt-independent formation of Wnt signalosomes through Dishevelled (Dvl)-cholesterol interaction. Cholesterol-Dvl interaction inhibitors potently blocked β-catenin signaling in APC-truncated CRC cells and suppressed their viability. Because of low IPM cholesterol level and low Dvl expression and dependence, normal cells including primary colon epithelial cells were not sensitive to these inhibitors. In vivo testing with a xenograft mouse model showed that our inhibitors effectively suppressed truncated APC-driven tumors without causing intestinal toxicity. Collectively, these results suggest that the most common type of CRC could be effectively and safely treated by blocking the cholesterol-Dvl-β-catenin signaling axis.

Proteogenomic characterization reveals tumorigenesis and progression of lung cancer manifested as subsolid nodules

Lung adenocarcinoma (LUAD) radiologically displayed as subsolid nodules (SSNs) is prevalent. Nevertheless, the precise clinical management of SSNs necessitates a profound understanding of their tumorigenesis and progression. Here, we analyze 66 LUAD displayed as SSNs covering 3 histological stages including adenocarcinoma in situ (AIS), minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IAC) by incorporating genomics, proteomics, phosphoproteomics and glycoproteomics. Intriguingly, cholesterol metabolism is aberrantly regulated in the preneoplastic AIS stage. Importantly, target ablation of proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the initiation of LUAD. Furthermore, sustained endoplasmic reticulum stress is demonstrated to be a hallmark and a reliable biomarker of AIS progression to IAC. Consistently, target promotion of ER stress profoundly retards LUAD progression. Our study provides comprehensive proteogenomic landscape of SSNs, sheds lights on the tumorigenesis and progression of SSNs and suggests preventive and therapeutic strategies for LUAD.

Role of Protein Regulators of Cholesterol Homeostasis in Immune Modulation and Cancer Pathophysiology

Cholesterol metabolism and homeostasis have emerged as important factors governing various aspects of cancer biology. Clinical associations between circulating cholesterol and poor prognosis or use of cholesterol-lowering medication and improved prognosis have been noted for several different solid tumors. Mechanistically, cholesterol has many different direct and indirect effects on cancer cells themselves but is also critically involved in shaping the function of other cells of the tumor microenvironment, especially immune cells. There are 2 major feedback loops regulating cholesterol homeostasis. Here we highlight the major proteins involved in the so-called oxysterol-bile acid feedback loop and discuss how each has been implicated in cancer biology. We focus on roles within the immune system with implications for cancer. Given that many of these proteins are enzymes or nuclear receptors, both of which are amenable to small molecule intervention, we posit that this axis may represent a promising area for therapeutic intervention.

Cholesterol efflux protein, ABCA1, supports anti-cancer functions of myeloid immune cells

Although immune therapy has seen significant advances, the majority of breast and other solid tumors do not respond or quickly develop de novo resistance. One factor driving resistance is highly immune suppressive myeloid cells (MCs) such as macrophages. Previous work has established clinical links between cholesterol and cancer outcome, and that MC function can be regulated through disruption in cholesterol metabolism. Thus, we screened for proteins that were expressed in MCs, involved in cholesterol homeostasis and whose expression was associated with survival; we identify the cholesterol efflux protein ABCA1. Preclinical studies revealed that ABCA1 activity resulted in increased anti-cancer functions of macrophages: enhanced tumor infiltration, decreased angiogenic potential, reduced efferocytosis, and improved support of CD8+ T cell activity. Mechanistically, different AKT isoforms are involved, through both PI3K dependent and independent mechanisms. Assessment of human blood and breast tumors revealed correlations between ABCA1 in macrophages and angiogenic potential, VEGFA , and CD8 T cell abundance and activity, highlighting the clinical relevance of our findings. The culmination of the effects of ABCA1 on MC function were demonstrated through increased tumor growth and metastasis in mice with MC specific knockout of ABCA1. Therefore, modulating ABCA1 activity within MCs may represent a novel approach to immune therapy.

Tracking Cholesterol Flip-Flop in Mammalian Plasma Membrane through Coarse-Grained Molecular Dynamics Simulations

Plasma membrane (PM) simulations at longer length and time scales at nearly atomistic resolution can provide invaluable insights into cell signaling, apoptosis, lipid trafficking, and lipid raft formation. We propose a coarse-grained (CG) model of a mammalian PM considering major lipid head groups distributed asymmetrically across the membrane bilayer and validate the model against bilayer structural properties from atomistic simulation. Using the proposed CG model, we identify a recurring pattern in the passive collective cholesterol transbilayer motion and study the individual cholesterol flip-flop events and associated pathways along with lateral ordering in the bilayer during a flip-flop event. We identify two discrete cholesterol flip-flop pathways: (i) a systematic rototranslational pathway and (ii) intraleaflet inversion followed by interleaflet translation (or reverse). We observe a periodic cholesterol enrichment in the exoplasmic leaflet of the PM bilayer and examine the underlying cholesterol-lipid affinities. We observe closer association between cholesterol and palmitoylsphingomyelin (PSM) lipid, relative to other lipids, and conclude that the cholesterol enrichment in the exoplasmic leaflet can be attributed to higher PSM content in that leaflet, together leading to formation of short-lived PSM-cholesterol-rich domains.

Cupric Doping Hollow Prussian Blue Nanoplatform for Enhanced Cholesterol Depletion: a Promising Strategy for Breast Cancer Therapy and Metastasis Inhibition

The dysregulated cholesterol metabolism in breast cancer cells drives malignancy, invasion, and metastasis, emphasizing the significance of reducing abnormal cholesterol accumulation for effective cancer treatment and metastasis inhibition. Despite its promise, cholesterol oxidase (ChOx) encounters challenge due to limited catalytic efficiency and susceptibility to harsh conditions. To overcome these hurdles, biocompatible nanoplatforms (Cu-HPB/C) tailored for efficient cholesterol depletion are introduced. Cu2+-doped hollow Prussian blue (Cu-HPB) acts as a carrier, shelter, and enhancer for ChOx, bolstering tumor-targeting ability, stability, and enzymatic activity. Tumor-responsive released Cu2+ notably augments ChOx activity, facilitating cholesterol depletion and disrupting lipid rafts, thereby impeding cell invasion and migration. Additionally, H2O2 generated from the oxidase reaction enhances Cu-HPB's chemo dynamic therapeutic efficacy. Transcriptomic analysis validates Cu-HPB/C's impact on cholesterol homeostasis and reveals cell death mechanisms including oxidative stress, ferroptosis, cuproptosis, and apoptosis. Demonstrating therapeutic efficacy in both 4T1 tumor subcutaneous and metastasis mouse models, the study presents a direct and effective strategy for tumor therapy and metastasis inhibition through enhanced cholesterol depletion.

Cellular and molecular mechanisms underlying obesity in degenerative spine and joint diseases

Degenerative spine and joint diseases, including intervertebral disc degeneration (IDD), ossification of the spinal ligaments (OSL), and osteoarthritis (OA), are common musculoskeletal diseases that cause pain or disability to the patients. However, the pathogenesis of these musculoskeletal disorders is complex and has not been elucidated clearly to date. As a matter of fact, the spine and joints are not independent of other organs and tissues. Recently, accumulating evidence demonstrates the association between obesity and degenerative musculoskeletal diseases. Obesity is a common metabolic disease characterized by excessive adipose tissue or abnormal adipose distribution in the body. Excessive mechanical stress is regarded as a critical risk factor for obesity-related pathology. Additionally, obesity-related factors, mainly including lipid metabolism disorder, dysregulated pro-inflammatory adipokines and cytokines, are reported as plausible links between obesity and various human diseases. Importantly, these obesity-related factors are deeply involved in the regulation of cell phenotypes and cell fates, extracellular matrix (ECM) metabolism, and inflammation in the pathophysiological processes of degenerative spine and joint diseases. In this study, we systematically discuss the potential cellular and molecular mechanisms underlying obesity in these degenerative musculoskeletal diseases, and hope to provide novel insights for developing targeted therapeutic strategies.

Activated PARP1/FAK/COL5A1 signaling facilitates the tumorigenesis of cholesterol-resistant ovarian cancer cells through promoting EMT

Cancer cells require plentiful cholesterol for membrane biogenesis and other functional needs due to fast proliferating, leading to the interaction of cholesterol or its metabolites with cancer-related pathways. However, the impact of long-lasting high cholesterol concentrations on tumorigenesis and its underlying mechanisms remains largely unexplored. To the best of our knowledge, this study is the first to establish a cholesterol-resistant ovarian cancer cells, whose intracellular total cholesterol level up to 6-8 mmol/L. We confirmed that high cholesterol facilitated the progression of ovarian cancer in vitro and in vivo. Notably, our findings revealed significant upregulation of collagen type V alpha 1 chain (COL5A1) expression in cholesterol-resistant ovarian cancer cells and human ovarian cancer tissue, which was depended on FAK/Src activation. Mechanistically, PARP1 directly bound to FAK in response to activate FAK/Src/COL5A1 signaling. Intriguingly, COL5A1 depletion significantly impeded the tumorigenesis of these cells, concomitant with a decrease in epithelial-mesenchymal transition (EMT) progression. In conclusion, PARP1/FAK/COL5A1 signaling activation facilitated progression of cholesterol-resistant ovarian cancer cells by promoting EMT, thereby broadening a new therapeutic opportunity.

Differential analysis of sorting nexin 10 and sterol regulatory element-binding protein 2 expression in inflammatory bowel disease

Sorting nexin 10 (SNX10) expression induces intestinal barrier dysfunction and inflammatory responses; in contrast, its inhibition promotes intestinal mucosal healing through sterol regulatory element-binding protein 2 (SREBP2)-mediated cholesterol synthesis. However, its regulatory mechanism for the pathogenesis of inflammatory bowel disease (IBD) remains unclear. In this study, we examined SNX10 and SREBP2 expression in ulcerative colitis (UC) and Crohn's disease (CD). A total of 30 and 28 patients with UC and CD, respectively, were recruited. The expression of SNX10 and SREBP2 in the colonic mucosa was measured by immunohistochemistry (IHC). We discovered that patients with CD had significantly higher expression levels of SNX10 and SREBP2 than patients with UC and healthy controls. In addition, the expression of SREBP2 in patients with UC was significantly higher than that in healthy controls. In our study, we indicated that SNX10 and SREBP2 may serve as biomarkers for identifying patients with UC and CD, thereby providing a clinical therapeutic strategy for the treatment of IBD by inhibiting SNX10.

Shared genetics between breast cancer and predisposing diseases identifies novel breast cancer treatment candidates

BACKGROUND

Current effective breast cancer treatment options have severe side effects, highlighting a need for new therapies. Drug repurposing can accelerate improvements to care, as FDA-approved drugs have known safety and pharmacological profiles. Some drugs for other conditions, such as metformin, an antidiabetic, have been tested in clinical trials for repurposing for breast cancer. Here, we exploit the genetics of breast cancer and linked predisposing diseases to propose novel drug repurposing opportunities. We hypothesize that if a predisposing disease contributes to breast cancer pathology, identifying the pleiotropic genes related to the risk of cancer could prioritize drugs, among all drugs treating a predisposing disease. We aim to develop a method to not only prioritize drugs for repurposing, but also to highlight shared etiology explaining repurposing.

METHODS

We compile breast cancer's predisposing diseases from literature. For each predisposing disease, we use GWAS summary statistics data to identify genes in loci showing genetic correlation with breast cancer. Then, we use a network approach to link these shared genes to canonical pathways. Similarly, for all drugs treating the predisposing disease, we link their targets to pathways. In this manner, we are able to prioritize a list of drugs based on each predisposing disease, with each drug linked to a set of implicating pathways. Finally, we evaluate our recommendations against drugs currently under investigation for breast cancer.

RESULTS

We identify 84 loci harboring mutations with positively correlated effects between breast cancer and its predisposing diseases; these contain 194 identified shared genes. Out of the 112 drugs indicated for the predisposing diseases, 74 drugs can be linked to shared genes via pathways (candidate drugs for repurposing). Fifteen out of these candidate drugs are already in advanced clinical trial phases or approved for breast cancer (OR = 9.28, p = 7.99e-03, one-sided Fisher's exact test), highlighting the ability of our approach to identify likely successful candidate drugs for repurposing.

CONCLUSIONS

Our novel approach accelerates drug repurposing for breast cancer by leveraging shared genetics with its known predisposing diseases. The result provides 59 novel candidate drugs alongside biological insights supporting each recommendation.

Loss of Sc5d results in micrognathia due to a failure in osteoblast differentiation

INTRODUCTION

Mutations in genes related to cholesterol metabolism, or maternal diet and health status, affect craniofacial bone formation. However, the precise role of intracellular cholesterol metabolism in craniofacial bone development remains unclear.

OBJECTIVE

The aim of this study is to determine how cholesterol metabolism aberrations affect craniofacial bone development.

METHODS

Mice with a deficiency in Sc5d, which encodes an enzyme involved in cholesterol synthesis, were analyzed with histology, micro computed tomography (microCT), and cellular and molecular biological methods.

RESULTS

Sc5d null mice exhibited mandible hypoplasia resulting from defects in osteoblast differentiation. The activation of the hedgehog and WNT/β-catenin signaling pathways, which induce expression of osteogenic genes Col1a1 and Spp1, was compromised in the mandible of Sc5d null mice due to a failure in the formation of the primary cilium, a cell surface structure that senses extracellular cues. Treatments with an inducer of hedgehog or WNT/β-catenin signaling or with simvastatin, a drug that restores abnormal cholesterol production, partially rescued the defects in osteoblast differentiation seen in Sc5d mutant cells.

CONCLUSION

Our results indicate that loss of Sc5d results in mandibular hypoplasia through defective primary cilia-mediated hedgehog and WNT/β-catenin signaling pathways.

DPP an extracellular matrix molecule induces Wnt5a mediated signaling to promote the differentiation of adult stem cells into odontogenic lineage

Dentin phosphophoryn (DPP) an extracellular matrix protein activates Wnt signaling in DPSCs (dental pulp stem cells). Wnt/β catenin signaling is essential for tooth development but the role of DPP-mediated Wnt5a signaling in odontogenesis is not well understood. Wnt5a is typically considered as a non-canonical Wnt ligand that elicits intracellular signals through association with a specific cohort of receptors and co-receptors in a cell and context-dependent manner. In this study, DPP facilitated the interaction of Wnt5a with Frizzled 5 and LRP6 to induce nuclear translocation of β-catenin. β-catenin has several nuclear binding partners that promote the activation of Wnt target genes responsible for odontogenic differentiation. Interestingly, steady increase in the expression of Vangl2 receptor suggest planar cell polarity signaling during odontogenic differentiation. In vitro observations were further strengthened by the low expression levels of Wnt5a and β-catenin in the teeth of DSPP KO mice which exhibit impaired odontoblast differentiation and defective dentin mineralization. Together, this study suggests that the DPP-mediated Wnt5a signaling could be exploited as a therapeutic approach for the differentiation of dental pulp stem cells into functional odontoblasts and dentin regeneration.

Up-regulation of MSMO1 was associated with poor survival in cervical cancer

Background

Methylsterol monooxygenase 1 (MSMO1) catalyzes C4-methylsterols demethylation in cholesterol biosynthesis pathway. MSMO1 is increased and up-regulation of MSMO1 is correlated with progression of some tumor. But the correlation of MSMO1 to cervical cancer is unknown. The current study aimed to explore the expression pattern of MSMO1 in cervical cancer and its correlation to clinical characteristics.

Methods

In this study, 306 cervical cancer cases and 13 non-tumor cases were included. We compared MSMO1 expression level in non-tumor cervical tissues and cervical cancer samples using the Wilcoxon rank sum test. Univariate regression was used to investigate the correlation between MSMO1 expression as well as other clinical characteristics and prognosis. Clinical characteristics associated with prognosis in univariate analysis were used as adjustments for multivariate analysis to further validate the relationship between MSMO1 expression and cervical cancer prognosis. Patients' survival in different subgroups was compared by Kaplan-Meier (KM) method. The potential protein interaction was analyzed. T cell infiltration level in MSMO1 high and low group patients was compared.

Results

MSMO1 expression level was up-regulated in cervical cancer (P<0.001). Patients who had stage III-IV diseases (P=0.04) and did not achieve complete response after primary treatment had higher MSMO1 expression (P<0.001). High MSMO1 expression patients showed a lower overall survival (OS) (P=0.004), disease-specific survival (DSS) (P=0.004) and progression-free survival (PFS) (P=0.002). High MSMO1 expression was a risk factor to OS (P=0.01), DSS (P=0.009) and PFS (P=0.009). Multiple variate analysis showed that high MSMO1 expression was an independent risk factor to OS [hazard ratio (HR) =1.902, 95% confidence interval (CI): 1.156-3.129, P=0.01], DSS (HR =2.172, 95% CI: 1.210-3.897, P=0.009) and PFS (HR =1.975, 95% CI: 1.189-3.282, P=0.009) in cervical squamous cell carcinoma (CESC). The prognostic value of high MSMO1 expression was further examined in other databases, including KM-plotter, Gene Expression Profiling Interactive Analysis (GEPIA) and Gene Expression Omnibus (GEO) database.

Conclusions

The current research showed that MSMO1 was increased and was associated with poor prognosis in CESC.

Structural basis of frizzled 7 activation and allosteric regulation

Frizzleds (ten paralogs: FZD1-10) belong to the class F of G protein-coupled receptors (GPCRs), which remains poorly understood despite its crucial role in multiple key biological functions including embryonic development, stem cell regulation, and homeostasis in the adult. FZD7, one of the most studied members of the family, is more specifically involved in the migration of mesendoderm cells during the development and renewal of intestinal stem cells in adults. Moreover, FZD7 has been highlighted for its involvement in tumor development predominantly in the gastrointestinal tract. This study reports the structure of inactive FZD7, without any stabilizing mutations, determined by cryo-electron microscopy (cryo-EM) at 1.9 Å resolution. We characterize a fluctuating water pocket in the core of the receptor important for FZD7 dynamics. Molecular dynamics simulations are used to investigate the temporal distribution of those water molecules and their importance for potential conformational changes in FZD7. Moreover, we identify lipids interacting with the receptor core and a conserved cholesterol-binding site, which displays a key role in FZD7 association with a transducer protein, Disheveled (DVL), and initiation of downstream signaling and signalosome formation.

Softening the tumor matrix through cholesterol depletion breaks the physical barrier for enhanced antitumor therapy

The tumor develops defense tactics, including conversing the mechanical characteristics of tumor cells and their surrounding environment. A recent study reported that cholesterol depletion stiffens tumor cells, which could enhance adaptive T-cell immunotherapy. However, it remains unclear whether reducing the cholesterol in tumor cells contributes to re-educating the stiff tumor matrix, which serves as a physical barrier against drug penetration. Herein, we found that depleting cholesterol from tumor cells can demolish the intratumor physical barrier by disrupting the mechanical signal transduction between tumor cells and the extracellular matrix through the destruction of lipid rafts. This disruption allows nanoparticles (H/S@hNP) to penetrate deeply, resulting in improved photodynamic treatment. Our research also indicates that cholesterol depletion can inhibit the epithelial-mesenchymal transition and repolarize tumor-associated macrophages from M2 to M1, demonstrating the essential role of cholesterol in tumor progression. Overall, this study reveals that a cholesterol-depleted, softened tumor matrix reduces the difficulty of drug penetration, leading to enhanced antitumor therapeutics.

Shared genetics between breast cancer and predisposing diseases identifies novel breast cancer treatment candidates

Background

Current effective breast cancer treatment options have severe side effects, highlighting a need for new therapies. Drug repurposing can accelerate improvements to care, as FDA-approved drugs have known safety and pharmacological profiles. Some drugs for other conditions, such as metformin, an antidiabetic, have been tested in clinical trials for repurposing for breast cancer. Here, we exploit the genetics of breast cancer and linked predisposing diseases to propose novel drug repurposing. We hypothesize that if a predisposing disease contributes to breast cancer pathology, identifying the pleiotropic genes related to the risk of cancer could prioritize drug targets, among all drugs treating a predisposing disease. We aim to develop a method to not only prioritize drug repurposing, but also to highlight shared etiology explaining repurposing.

Methods

We compile breast cancer's predisposing diseases from literature. For each predisposing disease, we use GWAS summary statistics to identify genes in loci showing genetic correlation with breast cancer. Then, we use a network approach to link these shared genes to canonical pathways, and similarly for all drugs treating the predisposing disease, we link their targets to pathways. In this manner, we are able to prioritize a list of drugs based on each predisposing disease, with each drug linked to a set of implicating pathways. Finally, we evaluate our recommendations against drugs currently under investigation for breast cancer.

Results

We identify 84 loci harboring mutations with positively correlated effects between breast cancer and its predisposing diseases; these contain 194 identified shared genes. Out of the 112 drugs indicated for the predisposing diseases, 76 drugs can be linked to shared genes via pathways (candidate drugs for repurposing). Fifteen out of these candidate drugs are already in advanced clinical trial phases or approved for breast cancer (OR = 9.28, p = 7.99e-03, one-sided Fisher's exact test), highlighting the ability of our approach to identify likely successful candidate drugs for repurposing.

Conclusions

Our novel approach accelerates drug repurposing for breast cancer by leveraging shared genetics with its known risk factors. The result provides 59 novel candidate drugs alongside biological insights supporting each recommendation.

DHCR7 links cholesterol synthesis with neuronal development and axonal integrity

The DHCR7 enzyme converts 7-DHC into cholesterol. Mutations in DHCR7 can block cholesterol production, leading to abnormal accumulation of 7-DHC and causing Smith-Lemli-Opitz syndrome (SLOS). SLOS is an autosomal recessive disorder characterized by multiple malformations, including microcephaly, intellectual disability, behavior reminiscent of autism, sleep disturbances, and attention-deficit/hyperactivity disorder (ADHD)-like hyperactivity. Although 7-DHC affects neuronal differentiation in ex vivo experiments, the precise mechanism of SLOS remains unclear. We generated Dhcr7 deficient (dhcr7-/-) zebrafish that exhibited key features of SLOS, including microcephaly, decreased neural stem cell pools, and behavioral phenotypes similar to those of ADHD-like hyperactivity. These zebrafish demonstrated compromised myelination, synaptic anomalies, and neurotransmitter imbalances. The axons of the dhcr7-/- zebrafish showed increased lysosomes and attenuated autophagy, suggesting that autophagy-related neuronal homeostasis is disrupted.

Paradoxes: Cholesterol and Hypoxia in Preeclampsia

Preeclampsia, a hypertensive disease of pregnancy of unknown etiology, is intensely studied as a model of cardiovascular disease (CVD) not only due to multiple shared pathologic elements but also because changes that develop over decades in CVD appear and resolve within days in preeclampsia. Those affected by preeclampsia and their offspring experience increased lifetime risks of CVD. At the systemic level, preeclampsia is characterized by increased cellular, membrane, and blood levels of cholesterol; however, cholesterol-dependent signaling, such as canonical Wnt/βcatenin, Hedgehog, and endothelial nitric oxide synthase, is downregulated indicating a cholesterol deficit with the upregulation of cholesterol synthesis and efflux. Hypoxia-related signaling in preeclampsia also appears to be paradoxical with increased Hypoxia-Inducible Factors in the placenta but measurably increased oxygen in maternal blood in placental villous spaces. This review addresses the molecular mechanisms by which excessive systemic cholesterol and deficient cholesterol-dependent signaling may arise from the effects of dietary lipid variance and environmental membrane modifiers causing the cellular hypoxia that characterizes preeclampsia.

Cholesterol neutralized vemurafenib treatment by promoting melanoma stem-like cells via its metabolite 27-hydroxycholesterol

Vemurafenib has been used as first-line therapy for unresectable or metastatic melanoma with BRAFV600E mutation. However, overall survival is still limited due to treatment resistance after about one year. Therefore, identifying new therapeutic targets for melanoma is crucial for improving clinical outcomes. In the present study, we found that lowering intracellular cholesterol by knocking down DHCR24, the limiting synthetase, impaired tumor cell proliferation and migration and abrogated the ability to xenotransplant tumors. More importantly, administration of DHCR24 or cholesterol mediated resistance to vemurafenib and promoted the growth of melanoma spheroids. Mechanistically, we identified that 27-hydroxycholesterol (27HC), a primary metabolite of cholesterol synthesized by the enzyme cytochrome P450 27A1 (CYP27A1), reproduces the phenotypes induced by DHCR24 or cholesterol administration and activates Rap1-PI3K/AKT signaling. Accordingly, CYP27A1 is highly expressed in melanoma patients and upregulated by DHCR24 induction. Dafadine-A, a CYP27A1 inhibitor, attenuates cholesterol-induced growth of melanoma spheroids and abrogates the resistance property of vemurafenib-resistant melanoma cells. Finally, we confirmed that the effects of cholesterol on melanoma resistance require its metabolite 27HC through CYP27A1 catalysis, and that 27HC further upregulates Rap1A/Rap1B expression and increases AKT phosphorylation. Thus, our results suggest that targeting 27HC may be a useful strategy to overcome treatment resistance in metastatic melanoma.

Dishevelled localization and function are differentially regulated by structurally distinct sterols

The Dishevelled (DVL) family of proteins form supramolecular protein and lipid complexes at the cytoplasmic interface of the plasma membrane to regulate tissue patterning, proliferation, cell polarity, and oncogenic processes through DVL-dependent signaling, such as Wnt/β-catenin. While DVL binding to cholesterol is required for its membrane association, the specific structural requirements and cellular impacts of DVL-sterol association are unclear. We report that intracellular sterols which accumulate within normal and pathological conditions cause aberrant DVL activity. In silico and molecular analyses suggested orientation of the β- and α-sterol face within the DVL-PDZ domain regulates DVL-sterol binding. Intracellular accumulation of naturally occurring sterols impaired DVL2 plasma membrane association, inducing DVL2 nuclear localization via Foxk2. Changes to intracellular sterols also selectively impaired DVL2 protein-protein interactions This work identifies sterol specificity as a regulator of DVL signaling, suggests intracellular sterols cause distinct impacts on DVL activity, and supports a role for intracellular sterol homeostasis in cell signaling.

Development of a chemically disclosed serum-free medium for mouse pluripotent stem cells

Mouse embryonic stem cells (mESCs) have been widely used as a model system to study the basic biology of pluripotency and to develop cell-based therapies. Traditionally, mESCs have been cultured in a medium supplemented with fetal bovine serum (FBS). However, serum with its inconsistent chemical composition has been problematic for reproducibility and for studying the role of specific components. While some serum-free media have been reported, these media contain commercial additives whose detailed components have not been disclosed. Recently, we developed a serum-free medium, DA-X medium, which can maintain a wide variety of adherent cancer lines. In this study, we modified the DA-X medium and established a novel serum-free condition for both naïve mESCs in which all components are chemically defined and disclosed (DA-X-modified medium for robust growth of pluripotent stem cells: DARP medium). The DARP medium fully supports the normal transcriptome and differentiation potential in teratoma and the establishment of mESCs from blastocysts that retain the developmental potential in all three germ layers, including germ cells in chimeric embryos. Utility of chemically defined DA-X medium for primed mouse epiblast stem cells (mEpiSCs) revealed that an optimal amount of cholesterol is required for the robust growth of naïve-state mESCs, but is dispensable for the maintenance of primed-state mEpiSCs. Thus, this study provides reliable and reproducible culture methods to investigate the role of specific components regulating self-renewal and pluripotency in a wide range of pluripotent states.

FOXA3 regulates cholesterol metabolism to compensate for low uptake during the progression of lung adenocarcinoma

Cholesterol metabolism is vital for multiple cancer progression, while how cholesterol affects lung, a low-cholesterol tissue, for cancer metastasis and the underlying mechanism remain unclear. In this study, we found that metastatic lung adenocarcinoma cells acquire cellular dehydrocholesterol and cholesterol by endogenous cholesterol biosynthesis, instead of uptake upon cholesterol treatment. Besides, we demonstrated that exogenous cholesterol functions as signaling molecule to induce FOXA3, a key transcription factor for lipid metabolism via GLI2. Subsequently, ChIP-seq analysis and molecular studies revealed that FOXA3 transcriptionally activated Hmgcs1, an essential enzyme of cholesterol biosynthesis, to induce endogenous dehydrocholesterol and cholesterol level for membrane composition change and cell migration. Conversely, FOXA3 knockdown or knockout blocked cholesterol biosynthesis and lung adenocarcinoma metastasis in mice. In addition, the potent FOXA3 inhibitor magnolol suppressed metastatic gene programs in lung adenocarcinoma patient-derived organoids (PDOs). Altogether, our findings shed light onto unique cholesterol metabolism and FOXA3 contribution to lung adenocarcinoma metastasis.

Dysregulation of cellular membrane homeostasis as a crucial modulator of cancer risk

Cellular membranes serve as an epicentre combining extracellular and cytosolic components with membranous effectors, which together support numerous fundamental cellular signalling pathways that mediate biological responses. To execute their functions, membrane proteins, lipids and carbohydrates arrange, in a highly coordinated manner, into well-defined assemblies displaying diverse biological and biophysical characteristics that modulate several signalling events. The loss of membrane homeostasis can trigger oncogenic signalling. More recently, it has been documented that select membrane active dietaries (MADs) can reshape biological membranes and subsequently decrease cancer risk. In this review, we emphasize the significance of membrane domain structure, organization and their signalling functionalities as well as how loss of membrane homeostasis can steer aberrant signalling. Moreover, we describe in detail the complexities associated with the examination of these membrane domains and their association with cancer. Finally, we summarize the current literature on MADs and their effects on cellular membranes, including various mechanisms of dietary chemoprevention/interception and the functional links between nutritional bioactives, membrane homeostasis and cancer biology.

Transcriptome Analysis of Granulosa Cells Reveals Regulatory Mechanisms Related to Chicken Follicle Development

In this study, we aimed to better understand the difference between the functions of the two types of granulosa cells and sought to discover more key genes involved in follicle development and follicle selection. Herein, we separately collected pre-hierarchical follicle granulosa cells (PHGCs) and preovulatory follicle granulosa cells (POGCs) for RNA extraction; the transcriptomes of the two groups were compared via RNA-seq. A total of 5273 differentially expressed genes (DEGs) were identified between the PHGCs and POGCs; 2797 genes were up-regulated and 2476 were down-regulated in the PHGCs compared with the POGCs. A qPCR analysis confirmed that the expression patterns of 16 randomly selected DEGs were highly consistent with the RNA-seq results. In the POGCs, many of the genes with the most significant increase in expression were related to steroid hormone synthesis. In addition, the genes with the most significant decline in expression, including AMH and WT1, were related to the inhibition of steroid hormone synthesis. These results suggest that steroid hormones play a key role in follicle development. Furthermore, a Gene Ontology (GO) analysis revealed that these DEGs were mainly involved in the primary metabolic process, the carbohydrate metabolic process, the cellular process, ribosomes, the cytoplasm, and intracellular processes. A Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were mainly enriched in steroid biosynthesis, the cell cycle, ribosomes, the TGF-beta signaling pathway, focal adhesion, and so on. We also observed the morphology of the follicles at different developmental stages, and the results showed that the thickness of the granular layer of the small yellow follicles (SYFs) decreased significantly with further development. In addition, we also found that the thickness of the granulosa layer of hens over 300 days old was significantly lower than that of 200-day-old hens. In short, these data indicate that the tissue morphology and function of granulosa cells change throughout follicle development.

Cholesterol induction in CD8+ T cell exhaustion in colorectal cancer via the regulation of endoplasmic reticulum-mitochondria contact sites

BACKGROUND

Hypercholesterolemia is one of the risk factors for colorectal cancer (CRC). Cholesterol can participate in the regulation of human T cell function and affect the occurrence and development of CRC.

OBJECTIVE

To elucidate the pathogenesis of CRC immune escape mediated by CD8+ T cell exhaustion induced by cholesterol.

METHODS

CRC samples (n = 217) and healthy individuals (n = 98) were recruited to analyze the relationship between peripheral blood cholesterol levels and the clinical features of CRC. An animal model of CRC with hypercholesterolemia was established. Intraperitoneal intervention with endoplasmic reticulum stress (ERS) inhibitors in hypercholesterolemic CRC mice was performed. CD69, PD1, TIM-3, and CTLA-4 on CD8+ T cells of spleens from C57BL/6 J mice were detected by flow cytometry. CD8+ T cells were cocultured with MC38 cells (mouse colon cancer cell line). The proliferation, apoptosis, migration and invasive ability of MC38 cells were detected by CCK-8 assay, Annexin-V APC/7-AAD double staining, scratch assay and transwell assay, respectively. Transmission electron microscopy was used to observe the ER structure of CD8+ T cells. Western blotting was used to detect the expression of ERS and mitophagy-related proteins. Mitochondrial function and energy metabolism were measured. Immunoprecipitation was used to detect the interaction of endoplasmic reticulum-mitochondria contact site (ERMC) proteins. Immunofluorescence colocalization was used to detect the expression and intracellular localization of ERMC-related molecules.

RESULTS

Peripheral blood cholesterol-related indices, including Tc, low density lipoproteins (LDL) and Apo(a), were all increased, and high density lipoprotein (HDL) was decreased in CRCs. The proliferation, migration and invasion abilities of MC38 cells were enhanced, and the proportion of tumor cell apoptosis was decreased in the high cholesterol group. The expression of IL-2 and TNF-α was decreased, while IFN-γ was increased in the high cholesterol group. It indicated high cholesterol could induce exhaustion of CD8+ T cells, leading to CRC immune escape. Hypercholesterolemia damaged the ER structure of CD8+ T cells and increased the expression of ER stress molecules (CHOP and GRP78), lead to CD8+ T cell exhaustion. The expression of mitophagy-related proteins (BNIP3, PINK and Parkin) in exhausted CD8+ T cells increased at high cholesterol levels, causing mitochondrial energy disturbance. High cholesterol enhanced the colocalization of Fis1/Bap31, MFN2/cox4/HSP90B1, VAPB/PTPIP51, VDAC1/IPR3/GRP75 in ERMCs, indicated that high cholesterol promoted the intermolecular interaction between ER and mitochondrial membranes in CD8+ T cells.

CONCLUSION

High cholesterol regulated the ERS-ERMC-mitophagy axis to induce the exhaustion of CD8+ T cells in CRC.

Acetyl-CoA is a key molecule for nephron progenitor cell pool maintenance

Nephron endowment at birth impacts long-term renal and cardiovascular health, and it is contingent on the nephron progenitor cell (NPC) pool. Glycolysis modulation is essential for determining NPC fate, but the underlying mechanism is unclear. Combining RNA sequencing and quantitative proteomics we identify 267 genes commonly targeted by Wnt activation or glycolysis inhibition in NPCs. Several of the impacted pathways converge at Acetyl-CoA, a co-product of glucose metabolism. Notably, glycolysis inhibition downregulates key genes of the Mevalonate/cholesterol pathway and stimulates NPC differentiation. Sodium acetate supplementation rescues glycolysis inhibition effects and favors NPC maintenance without hindering nephrogenesis. Six2Cre-mediated removal of ATP-citrate lyase (Acly), an enzyme that converts citrate to acetyl-CoA, leads to NPC pool depletion, glomeruli count reduction, and increases Wnt4 expression at birth. Sodium acetate supplementation counters the effects of Acly deletion on cap-mesenchyme. Our findings show a pivotal role of acetyl-CoA metabolism in kidney development and uncover new avenues for manipulating nephrogenesis and preventing adult kidney disease.

RNF2 regulates Wnt/ß-catenin signaling via TCF7L1 destabilization

The Wnt signaling pathway is a crucial regulator of various biological processes, such as development and cancer. The downstream transcription factors in this pathway play a vital role in determining the threshold for signaling induction and the length of the response, which vary depending on the biological context. Among the four transcription factors involved in canonical Wnt/ß-catenin signaling, TCF7L1 is known to possess an inhibitory function; however, the underlying regulatory mechanism remains unclear. In this study, we identified the E3 ligase, RNF2, as a novel positive regulator of the Wnt pathway. Here, we demonstrate that RNF2 promotes the degradation of TCF7L1 through its ubiquitination upon activation of Wnt signaling. Loss-of-function studies have shown that RNF2 consistently destabilizes nuclear TCF7L1 and is required for proper Wnt target gene transcription in response to Wnt activation. Furthermore, our results revealed that RNF2 controls the threshold, persistence, and termination of Wnt signaling by regulating TCF7L1. Overall, our study sheds light on the previously unknown degradation mechanism of TCF7L1 by a specific E3 ligase, RNF2, and provides new insights into the variability in cellular responses to Wnt activation.

Dysregulation of cholesterol metabolism in cancer progression

Cholesterol homeostasis has been implicated in the regulation of cellular and body metabolism. Hence, deregulated cholesterol homeostasis leads to the development of many diseases such as cardiovascular diseases, and neurodegenerative diseases, among others. Recent studies have unveiled the connection between abnormal cholesterol metabolism and cancer development. Cholesterol homeostasis at the cellular level dynamically circulates between synthesis, influx, efflux, and esterification. Any dysregulation of this dynamic process disrupts cholesterol homeostasis and its derivatives, which potentially contributes to tumor progression. There is also evidence that cancer-related signals, which promote malignant progression, also regulate cholesterol metabolism. Here, we described the relationship between cholesterol metabolism and cancer hallmarks, with particular focus on the molecular mechanisms, and the anticancer drugs that target cholesterol metabolism.

Effect of Lipid Levels on Tumor-Infiltrating Lymphocytes and Prognosis in Patients with Triple-Negative Breast Cancer

Objective

Dyslipidemia can promote cell proliferation, malignant transformation, metastasis, and cancer recurrence. Moreover, it could also affect immune infiltration in the tumor microenvironment. Therefore, we aimed to explore the effects of lipid levels on tumor-infiltrating lymphocytes (TILs) and prognosis in patients with triple-negative breast cancer (TNBC).

Methods

Samples from 222 patients with TNBC from July 2007 to December 2019 were obtained from the tissue specimen banks in 3 hospitals. The blood samples were used to detect the levels of lipid levels such as apolipoprotein B (Apo B), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C). The TILs in the 222 TNBC tissues were detected using hematoxylin and eosin (H&E) staining, and the relationship between the lipid levels, clinical characteristics, and prognosis was analyzed.

Results

Among TNBC patients, the overall survival (OS) time and disease-free survival (DFS) time were lower in patients with high LDL-C levels than those with low LDL-C levels (p < 0.01, respectively). The DFS was shorter in patients with low stromal TIL (STIL) levels than those with moderate or high STIL levels (p = 0.023). Multifactor Cox regression analysis showed that LDL-C level, Apo B level, and lymphocyte-predominant breast cancer were independent risk factors for OS in TNBC patients. The number of positive lymph nodes, postoperative staging, and total amount of TILs were independent risk factors for DFS in TNBC patients.

Conclusion

The LDL-C and STIL levels were correlated with survival and prognosis in patients with TNBC.

Inhibiting sorting nexin 10 promotes mucosal healing through SREBP2-mediated stemness restoration of intestinal stem cells

Intestinal stem cell (ISC) is a promising therapeutic target for inflammatory bowel disease. Cholesterol availability is critical for ISC stemness. Low plasma cholesterol is a typical feature of Crohn's disease (CD); however, its impact on mucosal healing remains unclear. Here, we identified an essential role of sorting nexin 10 (SNX10) in maintaining the stemness of ISCs. SNX10 expression in intestinal tissues positively correlates with the severity of human CD and mouse colitis. Conditional SNX10 knockout in intestinal epithelial cells or ISCs promotes intestinal mucosal repair by maintaining the ISC population associated with increased intracellular cholesterol synthesis. Disassociation of ERLIN2 with SCAP by SNX10 deletion enhances the activation of SREBP2, resulting in increased cholesterol biosynthesis. DC-SX029, a small-molecule inhibitor of SNX10, was used to verify the druggable potential of SNX10 for the treatment of patients with CD. Our study provides a strategy for mucosal healing through SREBP2-mediated stemness restoration of ISCs.

APOE deficiency impacts neural differentiation and cholesterol biosynthesis in human iPSC-derived cerebral organoids

BACKGROUND

The apolipoprotein E (APOE) gene is the strongest genetic risk factor for Alzheimer's disease (AD); however, how it modulates brain homeostasis is not clear. The apoE protein is a major lipid carrier in the brain transporting lipids such as cholesterol among different brain cell types.

METHODS

We generated three-dimensional (3-D) cerebral organoids from human parental iPSC lines and its isogenic APOE-deficient (APOE-/-) iPSC line. To elucidate the cell-type-specific effects of APOE deficiency in the cerebral organoids, we performed scRNA-seq in the parental and APOE-/- cerebral organoids at Day 90.

RESULTS

We show that APOE deficiency in human iPSC-derived cerebral organoids impacts brain lipid homeostasis by modulating multiple cellular and molecular pathways. Molecular profiling through single-cell RNA sequencing revealed that APOE deficiency leads to changes in cellular composition of isogenic cerebral organoids likely by modulating the eukaryotic initiation factor 2 (EIF2) signaling pathway as these events were alleviated by the treatment of an integrated stress response inhibitor (ISRIB). APOE deletion also leads to activation of the Wnt/β-catenin signaling pathway with concomitant decrease of secreted frizzled-related protein 1 (SFRP1) expression in glia cells. Importantly, the critical role of apoE in cell-type-specific lipid homeostasis was observed upon APOE deletion in cerebral organoids with a specific upregulation of cholesterol biosynthesis in excitatory neurons and excessive lipid accumulation in astrocytes. Relevant to human AD, APOE4 cerebral organoids show altered neurogenesis and cholesterol metabolism compared to those with APOE3.

CONCLUSIONS

Our work demonstrates critical roles of apoE in brain homeostasis and offers critical insights into the APOE4-related pathogenic mechanisms.

Identification of cholesterol metabolism-related subtypes in nonfunctioning pituitary neuroendocrine tumors and analysis of immune infiltration

OBJECTIVE

This study aimed to investigate the role of cholesterol metabolism-related genes in nonfunctioning pituitary neuroendocrine tumors (NF-PitNETs) invading the cavernous sinus and analyze the differences in immune cell infiltration between invasive and noninvasive NF-PitNETs.

METHODS

First, a retrospective analysis of single-center clinical data was performed. Second, the immune cell infiltration between invasive and noninvasive NF-PitNETs in the GSE169498 dataset was further analyzed, and statistically different cholesterol metabolism-related gene expression matrices were obtained from the dataset. The hub cholesterol metabolism-related genes in NF-PitNETs were screened by constructing machine learning models. In accordance with the hub gene, 73 cases of NF-PitNETs were clustered into two subtypes, and the functional differences and immune cell infiltration between the two subtypes were further analyzed.

RESULTS

The clinical data of 146 NF-PitNETs were evaluated, and the results showed that the cholesterol (P = 0.034) between invasive and noninvasive NF-PitNETs significantly differed. After binary logistic analysis, cholesterol was found to be an independent risk factor for cavernous sinus invasion (CSI) in NF-PitNETs. Bioinformatics analysis found three immune cells between invasive and noninvasive NF-PitNETs were statistically significant in the GSE169498 dataset, and 34 cholesterol metabolism-related genes with differences between the two groups were obtained 12 hub genes were selected by crossing the two machine learning algorithm results. Subsequently, cholesterol metabolism-related subgroups, A and B, were obtained by unsupervised hierarchical clustering analysis. The results showed that 12 immune cells infiltrated differentially between the two subgroups. The chi-square test revealed that the two subgroups had statistically significance in the invasive and noninvasive samples (P = 0.001). KEGG enrichment analysis showed that the differentially expressed genes were mainly enriched in the neural ligand-receptor pathway. GSVA analysis showed that the mTORC signaling pathway was upregulated and played an important role in the two-cluster comparison.

CONCLUSION

By clinical data and bioinformatics analysis, cholesterol metabolism-related genes may promote the infiltration abundance of immune cells in NF-PitNETs and the invasion of cavernous sinuses by NF-PitNETs through the mTOR signaling pathway. This study provides a new perspective to explore the pathogenesis of cavernous sinus invasion by NF-PitNETs and determine potential therapeutic targets for this disease.

Cholesterol-Depletion-Induced Membrane Repair Carries a Raft Conformer of P-Glycoprotein to the Cell Surface, Indicating Enhanced Cholesterol Trafficking in MDR Cells, Which Makes Them Resistant to Cholesterol Modifications

The human P-glycoprotein (P-gp), a transporter responsible for multidrug resistance, is present in the plasma membrane's raft and non-raft domains. One specific conformation of P-gp that binds to the monoclonal antibody UIC2 is primarily associated with raft domains and displays heightened internalization in cells overexpressing P-gp, such as in NIH-3T3 MDR1 cells. Our primary objective was to investigate whether the trafficking of this particular P-gp conformer is dependent on cholesterol levels. Surprisingly, depleting cholesterol using cyclodextrin resulted in an unexpected increase in the proportion of raft-associated P-gp within the cell membrane, as determined by UIC2-reactive P-gp. This increase appears to be a compensatory response to cholesterol loss from the plasma membrane, whereby cholesterol-rich raft micro-domains are delivered to the cell surface through an augmented exocytosis process. Furthermore, this exocytotic event is found to be part of a complex trafficking mechanism involving lysosomal exocytosis, which contributes to membrane repair after cholesterol reduction induced by cyclodextrin treatment. Notably, cells overexpressing P-gp demonstrated higher total cellular cholesterol levels, an increased abundance of stable lysosomes, and more effective membrane repair following cholesterol modifications. These modifications encompassed exocytotic events that involved the transport of P-gp-carrying rafts. Importantly, the enhanced membrane repair capability resulted in a durable phenotype for MDR1 expressing cells, as evidenced by significantly improved viabilities of multidrug-resistant Pgp-overexpressing immortal NIH-3T3 MDR1 and MDCK-MDR1 cells compared to their parents when subjected to cholesterol alterations.

Mutant APC reshapes Wnt signaling plasma membrane nanodomains by altering cholesterol levels via oncogenic β-catenin

Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly dynamic nano-assemblies at the plasma membrane. However, little is known regarding the role of oncogenic APC in reshaping Wnt nanodomains. This is noteworthy, because oncogenic APC does not act autonomously and requires activation of Wnt effectors upstream of APC to drive aberrant Wnt signaling. Here, we demonstrate the role of oncogenic APC in increasing plasma membrane free cholesterol and rigidity, thereby modulating Wnt signaling hubs. This results in an overactivation of Wnt signaling in the colon. Finally, using the Drosophila sterol auxotroph model, we demonstrate the unique ability of exogenous free cholesterol to disrupt plasma membrane homeostasis and drive Wnt signaling in a wildtype APC background. Collectively, these findings provide a link between oncogenic APC, loss of plasma membrane homeostasis and CRC development.

The cholesterol transporter NPC1 is essential for epigenetic regulation and maturation of oligodendrocyte lineage cells

The intracellular cholesterol transporter NPC1 functions in late endosomes and lysosomes to efflux unesterified cholesterol, and its deficiency causes Niemann-Pick disease Type C, an autosomal recessive lysosomal disorder characterized by progressive neurodegeneration and early death. Here, we use single-nucleus RNA-seq on the forebrain of Npc1^-/- mice at P16 to identify cell types and pathways affected early in pathogenesis. Our analysis uncovers significant transcriptional changes in the oligodendrocyte lineage during developmental myelination, accompanied by diminished maturation of myelinating oligodendrocytes. We identify upregulation of genes associated with neurogenesis and synapse formation in Npc1^-/- oligodendrocyte lineage cells, reflecting diminished gene silencing by H3K27me3. Npc1^-/- oligodendrocyte progenitor cells reproduce impaired maturation in vitro, and this phenotype is rescued by treatment with GSK-J4, a small molecule inhibitor of H3K27 demethylases. Moreover, mobilizing stored cholesterol in Npc1^-/- mice by a single administration of 2-hydroxypropyl-β-cyclodextrin at P7 rescues myelination, epigenetic marks, and oligodendrocyte gene expression. Our findings highlight an important role for NPC1 in oligodendrocyte lineage maturation and epigenetic regulation, and identify potential targets for therapeutic intervention.

Cholesterol homeostasis in hair follicle keratinocytes is disrupted by impaired ABCA5 activity

The importance of cholesterol in hair follicle biology is underscored by its links to the pathogenesis of alopecias and hair growth disorders. Reports have associated defects in ABCA5, a membrane transporter, with altered keratinocyte cholesterol distribution in individuals with a form of congenital hypertrichosis, yet the biological basis for this defect in hair growth remains unknown. This study aimed to determine the impact of altered ABCA5 activity on hair follicle keratinocyte behaviour. Primary keratinocytes isolated from the outer root sheath of plucked human hair follicles were utilised as a relevant cell model. Following exogenous cholesterol loading, an increase in ABCA5 co-localisation to intracellular organelles was seen. Knockdown of ABCA5 revealed a dysregulation in cholesterol homeostasis, with LXR agonism leading to partial restoration of the homeostatic response. Filipin staining and live BODIPY cholesterol immunofluorescence microscopy revealed a reduction in endo-lysosomal cholesterol following ABCA5 knockdown. Analysis of oxysterols showed a significant increase in the fold change of 25-hydroxycholesterol and 7-β-hydroxycholesterol following cholesterol loading in ORS keratinocytes, after ABCA5 knockdown. These data suggest a role for ABCA5 in the intracellular compartmentalisation of free cholesterol in primary hair follicle keratinocytes. The loss of normal homeostatic response, following the delivery of excess cholesterol after ABCA5 knockdown, suggests an impact on LXR-mediated transcriptional activity. The loss of ABCA5 in the hair follicle could lead to impaired endo-lysosomal cholesterol transport, impacting pathways known to influence hair growth. This avenue warrants further investigation.

NUCB2/Nesfatin-1 drives breast cancer metastasis through the up-regulation of cholesterol synthesis via the mTORC1 pathway

BACKGROUND

Reprogramming lipid metabolism for tumor metastasis is essential in breast cancer, and NUCB2/Nesfatin-1 plays a crucial role in regulating energy metabolism. Its high expression is associated with poor prognosis in breast cancer. Here, we studied whether NUCB2/Nesfatin-1 promotes breast cancer metastasis through reprogramming cholesterol metabolism.

METHODS

ELISA was employed to measure the concentration of Nesfatin-1 in the serum of breast cancer patients and the control group. Database analysis suggested that NUCB2/Nesfatin-1 might be acetylated in breast cancer, which was confirmed by treating the breast cancer cells with acetyltransferase inhibitors. Transwell migration and Matrigel invasion assays were conducted, and nude mouse lung metastasis models were established to examine the effect of NUCB2/Nesfatin-1 on breast cancer metastasis in vitro and in vivo. The Affymetrix gene expression chip results were analyzed using IPA software to identify the critical pathway induced by NUCB2/Nesfatin-1. We evaluated the effect of NUCB2/Nesfatin-1 on cholesterol biosynthesis through the mTORC1-SREBP2-HMGCR axis by utilizing mTORC1 inhibitor and rescue experiments.

RESULTS

NUCB2/Nesfatin-1 was found to be overexpressed in the breast cancer patients, and its overexpression was positively correlated with poor prognosis. NUCB2 was potentially acetylated, leading to high expression in breast cancer. NUCB2/Nesfatin-1 promoted metastasis in vitro and in vivo, while Nesfatin-1 rescued impaired cell metastasis induced by NUCB2 depletion. Mechanistically, NUCB2/Nesfatin-1 upregulated cholesterol synthesis via the mTORC1 signal pathway, contributing to breast cancer migration and metastasis.

CONCLUSIONS

Our findings demonstrate that the NUCB2/Nesfatin-1/mTORC1/SREBP2 signal pathway is critical in regulating cholesterol synthesis, essential for breast cancer metastasis. Thus, NUCB2/Nesfatin-1 might be utilized as a diagnostic tool and also used in cancer therapy for breast cancer in the future.

A theoretical model of dietary lipid variance as the origin of primary ciliary dysfunction in preeclampsia

Serving as the cell's key interface in communicating with the outside world, primary cilia have emerged as an area of multidisciplinary research interest over the last 2 decades. Although the term "ciliopathy" was first used to describe abnormal cilia caused by gene mutations, recent studies focus on abnormalities of cilia that are found in diseases without clear genetic antecedents, such as obesity, diabetes, cancer, and cardiovascular disease. Preeclampsia, a hypertensive disease of pregnancy, is intensely studied as a model for cardiovascular disease partially due to many shared pathophysiologic elements, but also because changes that develop over decades in cardiovascular disease arise in days with preeclampsia yet resolve rapidly after delivery, thus providing a time-lapse view of the development of cardiovascular pathology. As with genetic primary ciliopathies, preeclampsia affects multiple organ systems. While aspirin delays the onset of preeclampsia, there is no cure other than delivery. The primary etiology of preeclampsia is unknown; however, recent reviews emphasize the fundamental role of abnormal placentation. During normal embryonic development, trophoblastic cells, which arise from the outer layer of the 4-day-old blastocyst, invade the maternal endometrium and establish extensive placental vascular connections between mother and fetus. In primary cilia of trophoblasts, Hedgehog and Wnt/catenin signaling operate upstream of vascular endothelial growth factor to advance placental angiogenesis in a process that is promoted by accessible membrane cholesterol. In preeclampsia, impaired proangiogenic signaling combined with an increase in apoptotic signaling results in shallow invasion and inadequate placental function. Recent studies show primary cilia in preeclampsia to be fewer in number and shortened with functional signaling abnormalities. Presented here is a model that integrates preeclampsia lipidomics and physiology with the molecular mechanisms of liquid-liquid phase separation in model membrane studies and the known changes in human dietary lipids over the last century to explain how changes in dietary lipids might reduce accessible membrane cholesterol and give rise to shortened cilia and defects in angiogenic signaling, which underlie placental dysfunction of preeclampsia. This model offers a possible mechanism for non-genetic dysfunction in cilia and proposes a proof-of-concept study to treat preeclampsia with dietary lipids.

Potential role of TREM2 in high cholesterol‑induced cell injury and metabolic dysfunction in SH‑SY5Y cells

Triggering receptor expressed on myeloid cells 2 (TREM2) is an important member of the immunoglobulin family of inflammatory stimulating receptors and is involved in a number of pathophysiological processes. The present study aimed to investigate the role of TREM2 in neurotoxicity induced by high cholesterol levels in SH-SY5Y cells and explore the potential mechanism. SH-SY5Y cells were routinely cultured and stimulated with a range of cholesterol concentrations. Cell viability was assessed using an MTT assay, morphological changes were observed, and the cell cycle distribution was measured using flow cytometry. Lipid deposition was measured by Oil red O staining, and the mRNA and protein expression levels of SRBEP-1 and SRBEP-2 were detected by quantitative PCR and western blotting, respectively. Moreover, the protein expression levels of BDNF, Copine-6, TREM1, TREM2, and key molecules of the Wnt signaling pathways were detected by western blotting. Finally, TREM2 was overexpressed to investigate its potential role in high cholesterol-induced neurotoxicity. The results showed that cell viability was significantly decreased in SH-SY5Y cells stimulated with cholesterol (0.1~100 µM) in a dose- and time-dependent manner. Stimulation with 100 µM cholesterol for 24 h resulted in morphological injuries, increased the proportion of SH-SY5Y cells at G0/G1, the degree of lipid accumulation, and the protein expression levels of sterol regulatory element binding protein (SREBP)1 and SREBP2, markedly decreased the protein expression levels of BDNF, Copine-6, and TREM2, and the p-β-catenin/β-catenin ratio, and increased the expression levels of nesfatin-1, TREM1 and the p-GSK3β/GSK3β ratio. Furthermore, the imbalanced expression of BDNF, Copine-6, nesfatin-1, and p-GSK3β induced by high cholesterol levels was reversed after overexpression of TREM2. These results suggest that a high concentration of cholesterol could induce cell injury and lipid deposition in SH-SY5Y cells and that the underlying mechanism may be associated with imbalanced TREM2 expression.

Cholesterol biosynthesis modulates differentiation in murine cranial neural crest cells

Cranial neural crest cells (cNCC) are a multipotent embryonic cell population that give rise to a diverse set of cell types. These cells are particularly vulnerable to external metabolic stressors, as exemplified by the association between maternal hyperglycemia and congenital malformations. We were interested in studying the effect of various concentrations of glucose and pyruvate on cNCC metabolism, migration, and differentiation using an established murine neural crest cell model (O9-1). We unexpectedly observed a pattern of gene expression suggestive of cholesterol biosynthesis induction under glucose depletion conditions in O9-1 cells. We further showed that treatment with two different cholesterol synthesis inhibitors interfered with cell migration and differentiation, inhibiting chondrogenesis while enhancing smooth muscle cell differentiation. As congenital arhinia (absent external nose), a malformation caused by mutations in SMCHD1, appears to represent, in part, a defect in cNCC, we were also interested in investigating the effects of glucose and cholesterol availability on Smchd1 expression in O9-1 cells. Smchd1 expression was induced under high glucose conditions whereas cholesterol synthesis inhibitors decreased Smchd1 expression during chondrogenesis. These data highlight a novel role for cholesterol biosynthesis in cNCC physiology and demonstrate that human phenotypic variability in SMCHD1 mutation carriers may be related, in part, to SMCHD1's sensitivity to glucose or cholesterol dosage during development.

Phosphomevalonate Kinase Controls β-Catenin Signaling via the Metabolite 5-Diphosphomevalonate

β-catenin signaling is abnormally activated in cancer. Here, this work screens the mevalonate metabolic pathway enzyme PMVK to stabilize β-catenin signaling using a human genome-wide library. On the one hand, PMVK-produced MVA-5PP competitively binds to CKIα to prevent β-catenin Ser45 phosphorylation and degradation. On the other hand, PMVK functions as a protein kinase to directly phosphorylate β-catenin Ser184 to increase its protein nuclear localization. This synergistic effect of PMVK and MVA-5PP together promotes β-catenin signaling. In addition, PMVK deletion impairs mouse embryonic development and causes embryonic lethal. PMVK deficiency in liver tissue alleviates DEN/CCl4 -induced hepatocarcinogenesis. Finally, the small molecule inhibitor of PMVK, PMVKi5, is developed and PMVKi5 inhibits carcinogenesis of liver and colorectal tissues. These findings reveal a non-canonical function of a key metabolic enzyme PMVK and a novel link between the mevalonate pathway and β-catenin signaling in carcinogenesis providing a new target for clinical cancer therapy.

Cholesterol in the ciliary membrane as a therapeutic target against cancer

Primary cilium is a non-motile, antenna-like structure that develops in the quiescent G0 phase-cell surface. It is composed of an array of axonemal microtubules polymerized from the centrosome/basal body. The plasma membrane surrounding the primary cilium, which is called the ciliary membrane, contains a variety of receptors and ion channels, through which the cell receives extracellular chemical and physical stimuli to initiate signal transduction. In general, primary cilia disappear when cells receive the proliferative signals to re-enter the cell cycle. Primary cilia thus cannot be identified in many malignant and proliferative tumors. In contrast, some cancers, including basal cell carcinoma, medulloblastoma, gastrointestinal stromal tumor, and other malignancies, retain their primary cilia. Importantly, it has been reported that the primary cilia-mediated oncogenic signals of Hedgehog, Wnt, and Aurora kinase A are involved in the tumorigenesis and tumor progression of basal cell carcinoma and some types of medulloblastoma. It has also been demonstrated that cholesterol is significantly more enriched in the ciliary membrane than in the rest of the plasma membrane to ensure Sonic hedgehog signaling. A series of epidemiological studies on statin drugs (cholesterol-lowering medication) demonstrated that they prevent recurrence in a wide range of cancers. Taken together, ciliary cholesterol could be a potential therapeutic target in primary cilia-dependent progressive cancers.

PCSK9 facilitates melanoma pathogenesis via a network regulating tumor immunity

BACKGROUND

PCSK9 regulates cholesterol homeostasis and promotes tumorigenesis. However, the relevance of these two actions and the mechanisms underlying PCSK9's oncogenic roles in melanoma and other cancers remain unclear.

METHODS

PCSK9's association with melanoma was analysed using the TCGA dataset. Empty vector (EV), PCSK9, gain-of-function (D374Y), and loss-of-function (Q152H) PCSK9 mutant were stably-expressed in murine melanoma B16 cells and studied for impact on B16 cell-derived oncogenesis in vitro and in vivo using syngeneic C57BL/6 and Pcsk9^-/- mice. Intratumoral accumulation of cholesterol was determined. RNA-seq was performed on individual tumor types. Differentially-expressed genes (DEGs) were derived from the comparisons of B16 PCSK9, B16 D374Y, or B16 Q152H tumors to B16 EV allografts and analysed for pathway alterations.

RESULTS

PCSK9 expression and its network negatively correlated with the survival probability of patients with melanoma. PCSK9 promoted B16 cell proliferation, migration, and growth in soft agar in vitro, formation of tumors in C57BL/6 mice in vivo, and accumulation of intratumoral cholesterol in a manner reflecting its regulation of the low-density lipoprotein receptor (LDLR): Q152H, EV, PCSK9, and D374Y. Tumor-associated T cells, CD8 + T cells, and NK cells were significantly increased in D374Y tumors along with upregulations of multiple immune checkpoints, IFNγ, and 143 genes associated with T cell dysfunction. Overlap of 36 genes between the D374Y DEGs and the PCSK9 DEGs predicted poor prognosis of melanoma and resistance to immune checkpoint blockade (ICB) therapy. CYTH4, DENND1C, AOAH, TBC1D10C, EPSTI1, GIMAP7, and FASL (FAS ligand) were novel predictors of ICB therapy and displayed high level of correlations with multiple immune checkpoints in melanoma and across 30 human cancers. We observed FAS ligand being among the most robust biomarkers of ICB treatment and constructed two novel and effective multigene panels predicting response to ICB therapy. The profiles of allografts produced by B16 EV, PCSK9, D374Y, and Q152H remained comparable in C57BL/6 and Pcsk9^-/- mice.

CONCLUSIONS

Tumor-derived PCSK9 plays a critical role in melanoma pathogenesis. PCSK9's oncogenic actions are associated with intratumoral cholesterol accumulation. PCSK9 systemically affects the immune system, contributing to melanoma immune evasion. Novel biomarkers derived from the PCSK9-network effectively predicted ICB therapy responses.

Targeting 7-dehydrocholesterol reductase against EV-A71 replication by upregulating interferon response

Recent studies have shown a close link between viral infections and cholesterol metabolism. Here, we reported that 7-dehydrocholesterol reductase (DHCR7), a terminal enzyme for catalyzing cholesterol synthesis in the Kandutsch-Russell pathway, is harnessed by enterovirus A71 (EV-A71) benefitting for its replication. Overexpression of DHCR7 resulted in upregulating of EV-A71 replication, while the S14A mutation, which reduces DHCR7 enzyme activity, has no effect on EV-A71 replication. Knockdown of DHCR7 expression with small interfering RNA (siRNA) or enzyme activity inhibition with pharmacological inhibitor AY9944 could significantly inhibit EV-A71 replication. Adding cholesterol to DHCR7 knockdown cells or AY9944-treated cells could rescue EV-A71 replication. More importantly, prophylactic administration of AY9944 effectively protected mice from lethal EV-A71 infection. In addition, the natural cholesterol precursor 7-dehydrocholesterol (7-DHC), which is converted to cholesterol by DHCR7, has a similar effect against EV-A71 infection. Mechanistically, AY9944 or 7-DHC treatment can specifically promote IRF3 phosphorylation to activate interferon response. Moreover, AY9944 effectively cleared coxsackievirus B3 (CVB3) and coxsackievirus A16 (CVA16) infections in vitro. In conclusion, pharmacological modulation of DHCR7 might provide a chance for treatment of enterovirus infection, including EV-A71.

Lipid Binding of SH2 Domains

The Src homology 2 (SH2) domain is a modular protein interaction domain that specifically recognizes the phosphotyrosine (pY) motif of a target molecule. We recently reported that a large majority of human SH2 domains tightly bind membrane lipids, and many show high lipid specificity. Most of them can bind a lipid and the pY motif coincidently because their lipid-binding sites are topologically distinct from pY-binding pockets. Lipid binding of SH2 domain-containing kinases and phosphatases is functionally important because it exerts exquisite spatiotemporal control on protein-protein interaction and cell signaling activities mediated by these proteins. Here, we describe two assays, surface plasmon resonance analysis and fluorescence quenching analysis, which allow quantitative determination of the affinity and specificity of SH2-lipid interaction and high-throughput screening for SH2 domain-lipid-binding inhibitors.