Cholesterol Homeostasis Research Articles

Decreased mRNA expression of NR1H3 and ABCA1 in pulmonary tuberculosis patients from population of Punjab, India.

Mycobacterium tuberculosis (MTB) is the causative organism of tuberculosis. Cholesterol is a crucial carbon source required for the survival of MTB in host cells. Transcription factor NR1H3 along with its important target genes ABCA1 and ApoE play important role in removal of extra cholesterol from cells. Changes in the gene expression of NR1H3, ABCA1 and ApoE can affect cholesterol homeostasis and thus the survival of MTB in host cells.Therefore, the present study was designed to analyze the mRNA expression of NR1H3, ABCA1 and ApoE in pulmonary TB (PTB) patients from the population of Punjab, India. In this study, mRNA expression of the transcription factor NR1H3 and its target genes ABCA1 and ApoE was analyzed in 89 subjects, including 41 PTB patients and 48 healthy controls (HCs) by real-time quantitative PCR. It was found that the mRNA expression of both NR1H3 and ABCA1 genes was significantly lower in TB patients than in HCs (p < 0.001). Even after sex-wise stratification of the subjects, mRNA expression of NR1H3 and ABCA1 was found to be down-regulated in both male and female TB patients. No significant difference was observed in expression of ApoE (p = 0.98). The present study found that the mRNA expression of NR1H3 and ABCA1 is down-regulated in TB patients from Punjab state of India.

SOAT1 regulates cholesterol metabolism to induce EMT in hepatocellular carcinoma

Cholesterol metabolism reprogramming is one of the significant characteristics of hepatocellular carcinoma (HCC). Cholesterol increases the risk of epithelial–mesenchymal transition (EMT) in cancer. Sterol O-acyltransferases 1 (SOAT1) maintains the cholesterol homeostasis. However, the exact mechanistic contribution of SOAT1 to EMT in HCC remains unclear. Here we demonstrated that SOAT1 positively related to poor prognosis of HCC, EMT markers and promoted cell migration and invasion in vitro, which was mediated by the increased cholesterol in plasmalemma and cholesterol esters accumulation. Furthermore, we reported that SOAT1 disrupted cholesterol metabolism homeostasis to accelerate tumorigenesis and development in HCC xenograft and NAFLD-HCC. Also, we detected that nootkatone, a sesquiterpene ketone, inhibited EMT by targeting SOAT1 in vitro and in vivo. Collectively, our finding indicated that SOAT1 promotes EMT and contributes to hepatocarcinogenesis by increasing cholesterol esterification, which is suppressed efficiently by nootkatone. This study demonstrated that SOAT1 is a potential biomarker and therapeutic target in NAFLD-HCC and SOAT1-targeting inhibitors are expected to be the potential new therapeutic treatment for HCC.

Estrogen induces LCAT to maintain cholesterol homeostasis and suppress hepatocellular carcinoma development.

Hepatocellular carcinoma (HCC) is an aggressive disease that occurs predominantly in men. Estrogen elicits protective effects against HCC development. Elucidation of the estrogen-regulated biological processes that suppress HCC could lead to improved prevention and treatment strategies. Here, we performed transcriptomic analyses on mouse and human liver cancer and identified LCAT as the most highly estrogen-upregulated gene and a biomarker of favorable prognosis. LCAT upregulation inhibited HCC in vitro and in vivo and mediated estrogen-induced suppression of HCC in an ESR1-dependent manner. LCAT facilitated high-density lipoprotein cholesterol (HDL-C) production and uptake via the LDLR and SCARB1 pathways. Consistently, high HDL-C levels corresponded to a favorable prognosis in HCC patients. The enhanced HDL-C absorption induced by LCAT impaired SREBP2 maturation, which ultimately suppressed cholesterol biosynthesis and dampened HCC cell proliferation. HDL-C alone inhibited HCC growth comparably to the cholesterol-lowering drug lovastatin, and SREBF2 overexpression abolished the inhibitory activity of LCAT. Clinical observations and cross-analyses of multiple databases confirmed the correlation of elevated LCAT and HDL-C levels to reduced cholesterol synthesis and improved HCC patient prognosis. Furthermore, LCAT deficiency mimicked whereas LCAT overexpression abrogated the tumor growth promoting effects of ovariectomy in HCC-bearing female mice. Most importantly, HDL-C and LCAT delayed the development of subcutaneous tumors in nude mice, and HDL-C synergized with lenvatinib to eradicate orthotopic liver tumors. Collectively, this study reveals that estrogen upregulates LCAT to maintain cholesterol homeostasis and dampen hepatocarcinogenesis. LCAT and HDL-C represent potential prognostic and therapeutic biomarkers for targeting cholesterol homeostasis as a strategy for treating HCC.

Methyl CpG binding protein 2 regulates CYP27A1-induced myometrial contraction during preterm labor.

Persistent and intense uterine contraction is a risk factor for preterm labor. We previously found that Methyl-CpG binding protein 2 (MeCP2), as a target of infection-related microRNA miR-212-3p, may play an inhibitory role in regulating myometrium contraction. However, the molecular mechanisms by which MeCP2 regulates myometrial contraction are still unknown. In this study, we found that MeCP2 protein expression was lower in myometrial specimens obtained from preterm labor cases, compared to those obtained from term labor cases. Herein, using RNA sequence analysis of global gene expression in human uterine smooth muscle cells (HUSMCs) following siMeCP2, we show that MeCP2 silence caused dysregulation of cholesterol metabolism pathway. Notably, MeCP2 silence resulted in the upregulation of CYP27A1, the key enzyme involved in regulating cholesterol homeostasis, in HUSMCs. Methylation Specific PCR (MSP), Chromatin Immunoprecipitation (ChIP) and dual luciferase reporter gene technology indicated that MeCP2 could bind to the methylated CYP27A1 promoter region and repress its transcription. Administration of siCYP27A1 in an LPS-induced preterm labor mouse model delayed the onset of preterm labor. Human preterm myometrium and the LPS-induced preterm labor mouse model both showed lower expression of MeCP2 and increased expression of CYP27A1. These results demonstrated that aberrant upregulation of CYP27A1 induced by MeCP2 silencing is one of the mechanisms facilitating inappropriate myometrial contraction. CYP27A1 could be exploited as a novel therapeutic target for preterm birth.

Cytotoxic sigma-2 ligands trigger cancer cell death via cholesterol-induced-ER-stress

Sigma-2-ligands (S2L) are characterized by high binding affinities to their cognate sigma-2 receptor, overexpressed in rapidly proliferating tumor cells. As such, S2L were developed as imaging probes (ISO1) or as cancer therapeutics, alone (SV119 [C6], SW43 [C10]) and as delivery vehicles for cytotoxic drug cargoes (C6-Erastin, C10-SMAC). However, the exact mechanism of S2L-induced cytotoxicity remains to be fully elucidated. A series of high-affinity S2L were evaluated regarding their cytotoxicity profiles across cancer cell lines. While C6 and C10 displayed distinct cytotoxicities, C0 and ISO1 were essentially non-toxic. Confocal microscopy and lipidomics analysis in cellular and mouse models revealed that C10 induced increases in intralysosomal free cholesterol and in cholesterol esters, suggestive of unaltered intracellular cholesterol trafficking. Cytotoxicity was caused by cholesterol excess, a phenomenon that contrasts the effects of NPC1 inhibition. RNA-sequencing revealed gene clusters involved in cholesterol homeostasis and ER stress response exclusively by cytotoxic S2L. ER stress markers were confirmed by qPCR and their targeted modulation inhibited or enhanced cytotoxicity of C10 in a predicted manner. Moreover, C10 increased sterol regulatory element-binding protein 2 (SREBP2) and low-density lipoprotein receptor (LDLR), both found to be pro-survival factors activated by ER stress. Furthermore, inhibition of downstream processes of the adaptive response to S2L with simvastatin resulted in synergistic treatment outcomes in combination with C10. Of note, the S2L conjugates retained the ER stress response of the parental ligands, indicative of cholesterol homeostasis being involved in the overall cytotoxicity of the drug conjugates. Based on these findings, we conclude that S2L-mediated cell death is due to free cholesterol accumulation that leads to ER stress. Consequently, the cytotoxic profiles of S2L drug conjugates are proposed to be enhanced via concurrent ER stress inducers or simvastatin, strategies that could be instrumental on the path toward tumor eradication.

Resistant starch from a tuberous root from the Andes cordillera improves metabolic and immune parameters in broilers

Resistant starch (RS) is a carbohydrate that exerts benefits on health. The present study aimed to research the effects of the Canna edulis Ker RS on metabolic and immune system indicators in broiler chickens. A total of 360 1- day-old male chicks were allotted to dietary treatments with 0% (RS0), 1% (RS1), and 2% (RS2) of RS inclusion. Chickens of RS1 and RS2 presented a lower rate of increase in serum glucose between the third and fifth week, with 50.9, 21.4, and 26.8% to RS0, RS1, and RS2, respectively. The higher serum cholesterol HDL was observed in broilers that consumed RS1 and RS2 diets at the fifth week of age (p < 0.05). The butyric acid levels of 16.59, 64.95, and 76.77 μmol/g were found in caecal content to RS0, RS1, and RS2, respectively (p < 0.01). The serum IgA levels were increased in broilers fed with the RS1 diet and decreased with the RS0 diet. The IgM was increased linearly as a function of age in the broilers RS1 and RS2. The subpopulation of T helper lymphocytes CD3+ CD4+ were increased in broilers fed with RS2 diet. The RS level that optimizes the humoral response was established as 1.07% and 1.56% for IgA and IgM, respectively (p < 0.05). The dietary inclusion of RS from C. edulis stimulated homeostasis of glucose and cholesterol with increase of HDL and caecal SCFA. Consequently, RS from C. edulis can be used as a nutraceutical additive in the broilers' diet.

Is cholesterol both the lock and key to abnormal transmembrane signals in Autism Spectrum Disorder?

Disturbances in cholesterol homeostasis have been associated with ASD. Lipid rafts are central in many transmembrane signaling pathways (including mTOR) and changes in raft cholesterol content affect their order function. Cholesterol levels are controlled by several mechanisms, including endoplasmic reticulum associated degradation (ERAD) of the rate limiting HMGCoA reductase. A new approach to increase cholesterol via temporary ERAD blockade using a benign bacterial toxin-derived competitor for the ERAD translocon is suggested.A new lock and key model for cholesterol/lipid raft dependent signaling is proposed in which the rafts provide both the afferent and efferent 'tumblers' across the membrane to allow 'lock and key' receptor transmembrane signals.

Murine Alox8 versus the human ALOX15B ortholog: differences and similarities.

Human arachidonate 15-lipoxygenase type B is a lipoxygenase that catalyzes the peroxidation of arachidonic acid at carbon-15. The corresponding murine ortholog however has 8-lipoxygenase activity. Both enzymes oxygenate polyunsaturated fatty acids in S-chirality with singular reaction specificity, although they generate a different product pattern. Furthermore, while both enzymes utilize both esterified fatty acids and fatty acid hydro(pero)xides as substrates, they differ with respect to the orientation of the fatty acid in their substrate-binding pocket. While ALOX15B accepts the fatty acid "tail-first," Alox8 oxygenates the free fatty acid with its "head-first." These differences in substrate orientation and thus in regio- and stereospecificity are thought to be determined by distinct amino acid residues. Towards their biological function, both enzymes share a commonality in regulating cholesterol homeostasis in macrophages, and Alox8 knockdown is associated with reduced atherosclerosis in mice. Additional roles have been linked to lung inflammation along with tumor suppressor activity. This review focuses on the current knowledge of the enzymatic activity of human ALOX15B and murine Alox8, along with their association with diseases.

Obeticholic Acid and Insulin Sensitivity in Overweight Patients with Prediabetes

BACKGROUND. Due to its role as a risk factor for the emergence of metabolic illnesses including type 2 diabetes, cardio-vascular disease, and certain cancers with pandemic evolution, obesity is a serious public health concern. Diabetes mellitus type 2 (T2DM) poses a major risk to human health. The byproducts of the breakdown of cholesterol are bile acids, which are crucial for preserving cholesterol homeostasis. Research indicates that bile acids might control insulin sensitivity, energy metabolism, and glucose tolerance. Farnesoid X receptors (FXRs) are crucial for controlling bile acid production and hepatic glucose metabolism. The ligand for FXR The semisynthetic derivative of chenodeoxycholic acid, a bile acid, is obeticholic acid (OCA). Research indicates that bile acids may be a viable therapeutic target for type 2 diabetes (T2DM) given that therapy with oleic acid (OCA) enhanced insulin sensitivity and decreased indicators of liver inflammation and fibrosis in individuals with T2DM and nonalcoholic steatohepatitis (NASH).AIM. To assess Obeticholic acid’s effectiveness in obese individuals with prediabetes.MATERIALS AND METHODS. Over the course of three months, we performed a randomized single blind placebo controlled trial on eighty-two overweight and obese patients with prediabetes in the outpatient clinic at Ain Shams University Hospital. Through block randomization, patients were split into two groups (Group A received daily oral tablets containing 5 mg of obeticholic acid, while Group B received non-sweet capsules as a placebo). Three follow-up visits were conducted to ensure adherence and monitor for any emergence of side effects.RESULTS. 82 patients of matched age and sex criteria who underwent block randomization into 2 equal groups, group (A) representing cases and group (B) the placebo controlled group, with 3 months’ regular follow up showed at end of treatment statistically significant difference in weight being lower in group (A) with p-value 0.004 with decreased parameters of glycemic profile (Fasting insulin, FPG, HOMA_IR, 2h PP, HbA1c) in group (A) with p-value &lt;0.001 except 2hpp which p-value is 0.006. Also ALT was much decreased in group(A) with p-value &lt;0.001. Lipid profile didn’t show significant difference between 2 groups except for TGs which deceased in follow up in group (A) with p-value &lt;0. 001. Additionally, it should be highlighted that there was no statistically significant difference between the control group’s baseline and post-treatment data.CONCLUSION. In individuals who are overweight or obese and have insulin resistance and prediabetes, activation of FXR by OCA results in enhanced insulin sensitivity. Patients who received OCA also lost weight.

The Role of Macrophage Dynamics in Atherosclerosis Analyzed Using a Petri Net-Based Model

Atherosclerosis, a chronic inflammatory and oxidative stress-mediated disease impacting the arterial system, stands as a primary cause of morbidity and mortality worldwide. The complexity of this disease, driven by numerous factors, requires a thorough investigation of its underlying mechanisms. In our study, we explore the complex interplay between cholesterol homeostasis, macrophage dynamics, and atherosclerosis development using a Petri net-based model anchored in credible, peer-reviewed biological and medical research. Our findings underscore the significant role of macrophage colony-stimulating factor (M-CSF) inhibition in reducing atherosclerotic plaque formation by modulating inflammatory responses and lipid accumulation. Furthermore, our model highlights the therapeutic potential of targeting the C-X-C motif ligand 12 (CXCL12)/ C-X-C motif chemokine receptor type 4 (CXCR4) pathway to hinder hematopoietic stem and progenitor cells’ (HSPCs’) mobilization and plaque development. Based on the results obtained, which are in agreement with current studies, additional strategies are also proposed, such as decreasing M1 macrophage polarization for therapeutic gains, opening the door to future research and novel treatment approaches.

House Dust-Derived Mixtures of Organophosphate Esters Alter the Phenotype, Function, Transcriptome, and Lipidome of KGN Human Ovarian Granulosa Cells.

Organophosphate esters (OPEs), used as flame retardants and plasticizers, are present ubiquitously in the environment. Previous studies suggest that exposure to OPEs is detrimental to female fertility in humans. However, no experimental information is available on the effects of OPE mixtures on ovarian granulosa cells, which play essential roles in female reproduction. We used high-content imaging to investigate the effects of environmentally relevant OPE mixtures on KGN human granulosa cell phenotypes. Perturbations to steroidogenesis were assessed using ELISA and qRT-PCR. A high-throughput transcriptomic approach, TempO-Seq™, was used to identify transcriptional changes in a targeted panel of genes. Effects on lipid homeostasis were explored using a cholesterol assay and global lipidomic profiling. OPE mixtures altered multiple phenotypic features of KGN cells, with triaryl OPEs in the mixture showing higher potencies than other mixture components. The mixtures increased basal production of steroid hormones; this was mediated by significant changes in the expression of critical transcripts involved in steroidogenesis. Further, the total-OPE mixture disrupted cholesterol homeostasis and the composition of intracellular lipid droplets. Exposure to complex mixtures of OPEs, similar to those found in house dust, may adversely affect female reproductive health by altering a multitude of phenotypic and functional endpoints in granulosa cells. This study provides novel insights into the mechanisms of actions underlying the toxicity induced by OPEs and highlights the need to examine the effects of human relevant chemical mixtures.

Circulating microRNA-33b levels are associated with the presence and severity of coronary heart disease

MicroRNA-33b (miR-33b) affected various biological pathways in regulating cholesterol homeostasis which may link to the pathogenesis of atherosclerotic lesions. However, whether this marker is associated with the presence and severity of coronary heart disease (CHD) is undetermined. We aim to explore the diagnostic value of circulating miR-33b level in the presence and severity of CHD. Altogether 320 patients were enrolled, including 240 patients diagnosed with CHD while 80 were classified as controls after CAG examination. Circulating miR-33b level was analyzed in all subjects, the Gensini score was calculated to assess the severity of stenotic lesions. The association between miR-33b and the presence and severity of CHD was analyzed, and the diagnostic potential of miR-33b of CHD was performed by the receiver operating characteristic (ROC) analysis. The CHD group had higher miR-33b levels (p < 0.001), and the miR-33b content significantly elevated following an increasing Gensini score (p for trend < 0.001). After adjustments for potential risk factors, such as several blood lipid markers, miR-33b remained a significant determinant for CHD (p < 0.001). ROC analysis disclosed that the AUC was 0.931. The optimal cutoff value of miR-33b was with a sensitivity of 81.3% and a specificity of 98.7% in differentiating CHD. It can prognosticate that the higher level of miR-33b was linked to increased severity of disease in CHD patients. Thus, the application of this marker might assist in the diagnosis and classification of CHD patients. Nevertheless, additional studies with larger sample sizes will be required to verify these results.

The Metabolism of Coenzyme A and Its Derivatives Plays a Crucial Role in Diseases.

Coenzyme A (CoA) functions as a crucial carrier of acyl groups within cells, playing a fundamental role in regulating acyl transfer reactions and participating in cellular metabolic processes. As the principal substrate and cofactor engaged in diverse metabolic reactions, CoA and its derivatives exert central influence over various physiological processes, primarily modulating lipid and ketone metabolism, as well as protein modification. This paper presents a comprehensive review of the molecular mechanisms by which CoA influences the onset and progression of cancer, cardiovascular disease (CVD), neurodegenerative disorders, and other illnesses. The main focal points include the following. (1) In cancer, enzymes such as acetyl-CoA synthetase 2, ATP citrate lyase, and acetyl-CoA carboxylase regulate lipid synthesis and energy metabolism by modulating acetyl-CoA levels. (2) In CVD, the effects of enzymes such as stearoyl-CoA desaturase-1, 3-hydroxy-3-methylglutaryl-CoA (HMGC) synthase 2, and HMGC reductase on the formation and advancement of these diseases are elucidated by their regulation of CoA metabolism across multiple organs. (3) In neurodegenerative disorders, the significance of CoA in maintaining cholesterol homeostasis in the brain and its implications on the development of such disorders are thoroughly discussed. The metabolic processes involving CoA and its derivatives span all physiological aspects within cells, playing a critical role in the onset and progression of various diseases. Elucidating the role of CoA in these conditions yields important insights that can serve as valuable references and guidance for disease diagnosis, treatment, and drug development.

Ligand-based Molecular Modeling of HDL Receptor SR-BI Inhibitors As Potent Anti-Hyperlipidemic Agents

Introduction:: The High-density lipoprotein (HDL) receptor, Scavenger receptor class B, type I (SRBI) plays a crucial role in lipoprotein metabolism, cholesterol homeostasis, and atherosclerosis. In the present study, a quantitative structure-activity relationship study (QSAR) investigation was conducted on a data set of 31 novel indolinyl thiazole-based inhibitors of SR-BI mediated lipid uptake. Method:: To build the QSAR model, Multiple linear regression analysis (MLR), partial least square analysis (PLS), and neural analysis (NN) were performed which were further evaluated internally as well as externally for the prediction of activity. The best QSAR model for MLR was selected with a correlation coefficient (r2) of 0.937, cross-validation r2cv of 0.908, and a standard error (S) value of 0.253. For PLS, r2 was 0.937 and for FFNN r2 was 0.961 (for the training set). This was further evaluated externally by a test set having r2 values 0.870 (MLR), 0.863(PLS), and 0.933(neural network) analysis. Result:: The final model comprised hydrophobic parameters (Lipole Z component) and steric parameters (molar refractivity and K alpha2 index). Conclusion:: All these descriptors generated comparable results which prove that the model generated is sound and has good predictability.

Abstract NG02: Distinct genomic and immunologic tumor evolution in germline TP53-driven breast cancers

Abstract Background: Acquired, somatic TP53 mutations leading to loss of p53 tumor suppressive functions are the most common genomic alteration across many cancer types. Breast cancer (BC) is the most common malignancy in females, and 50-75% of estrogen receptor (ER)-negative BC (with or without HER2 amplification) and 10-15% of ER+ BC acquire TP53 alterations. Pathogenic germline variants (PGVs) in TP53 occur in approximately 1:5000 people and lead to the Li Fraumeni Syndrome (LFS) in which individuals have an up to 90% risk of developing cancer over their lifetimes. The most common cancer in females with LFS is BC which occurs at a median age of onset of 30-35, nearly 30 years younger than sporadic BC. The distribution of BC subtypes is significantly different in LFS-BC patients compared to sporadic BC, with over half of LFS-BC being HER2+ BC and over 90% being ER+. The characteristics of LFS-BC, namely early onset and predominance of HER2+ disease, suggest different tumorigenesis mechanisms compared to sporadic breast cancer that may have implications for early detection, interception and treatment. Patients and Methods: We performed deep phenotyping on 93 LFS patients with 130 LFS-BC compared to 198 control patients with 209 nonLFS-BC. Controls were defined as having BC diagnosed age&amp;lt;50 and negative germline cancer susceptibility gene testing. We obtained clinical cases and/or blocks for histopathological analysis. DNA and RNA was extracted from available FFPE tumor blocks and analyzed using a targeted capture panel with copy number backbone-based DNA sequencing and RNAseq of ribosomal RNA depleted total RNA. A subset of LFS-BC underwent whole genome sequencing. Finally, slides underwent both single and multiplex immunohistochemistry (IHC) of immune markers. This series includes results of 22 LFS-BC, including seven cases of LFS ductal carcinoma in situ (LFS-DCIS) and 15 invasive ductal carcinomas (LFS-IDC). In addition, matched germline blood for all cases and surrounding (n=15) and/or contralateral (n=11) normal was analyzed. Finally, 27 non-LFS early onset breast cancer controls with matched blood normal were analyzed by the same pipeline. Results were also compared to sporadic BC from The Cancer Genome Atlas (TCGA). Results: Of the 137 adult women in our LFS cohort, 93 (68%) had developed at least one BC, with a total of 110 LFS-BC. The prevalence of BC in our cohort was nearly identical to the prevalence in the National Cancer Institute (NCI) public LFS database (69% of 698 females, p=0.82). The median (IQR) age of first BC diagnosis in our cohort was 36 (29,45) years, similar to the public cohort with a median (IQR) of 31 (27,38) years at first BC diagnosis. Of the 93 adult BC patients in our LFS cohort, 60 (64%) had developed synchronous or metachronous bilateral BC. In contrast, only 36 (18%) of the early-onset nonLFS-BC control cohort developed more than one BC (p&amp;lt;0.0001). LFS-BC was more commonly HER2+ compared nonLFS-BC (51% vs 20%, p&amp;lt;0.0001) Sixty pathological cases from LFS-BC were obtained including 40 (66%) invasive carcinomas, 19 (31%) pure DCIS, one malignant phyllodes. The majority of the invasive carcinomas were ductal (35, 88%) the other five were lobular, mixed ductal and lobular, and micropapillary types. All 40 invasive carcinomas were high grade, with associated DCIS in 27 (68%), lymphovascular invasion in 16 (40%), and sclerotic stroma in eight (20%). The majority of DCIS (either pure or with invasive carcinoma) was high grade (29, 63%) with comedonecrosis (19, 41%), and with associated calcifications (16). High-risk lesions such as radial scar, papilloma, atypical ductal hyperplasia, and lobular neoplasia were present in seven tumors. High p53 IHC nuclear expression (&amp;gt;50%) was seen in the majority of tumors from patients with missense mutations; whereas no protein expression (&amp;lt;1%, null pattern) was seen in majority of tumors from carriers of large exonic deletion, truncating, and splicing mutations in TP53. Using p53 IHC and sequencing results, we found evidence of biallelic loss of TP53 (fully mutant p53) in 21 of 22 (95%) LFS-BC, two of 15 surrounding normal (13%) and no contralateral normal breast tissue. Nearly all LFS-BC underwent biallelic loss of TP53 via focal copy neutral or deletion loss of heterozygosity (89%) or a somatically acquired TP53 mutation (9%). No recurrent oncogenic variants were identified except ERBB2 (HER2) copy number amplification. In contrast, recurrent oncogenic alterations in PIK3CA, GATA3 and MAP3K1 were seen in early onset nonLFS-BC, similar to sporadic BC in TCGA. Compared to nonLFS-BC, LFS-BC had lower or similar tumor mutational burden, copy number burden and aneuploid chromosome arm number. LFS-BC were instead marked by elevated focal segments of loss of heterozygosity (LOH) and allelic imbalance. Accordingly, copy number signature analysis from whole genome sequencing showed nearly all LFS-BC had undergone chromothripsis (CN5) with focal LOH on a diploid background (CN9). We identified 5115 significantly differentially expressed genes comparing LFS-BC to normal breast tissue from LFS patients. Using Gene Set Enrichment Analysis (GSEA), we found most significantly up and down regulated pathways in LFS-BC were similarly regulated in non-LFSBC compared to normal breast tissue. Notably, the apoptosis pathway was significantly down-regulated in LFS-BC but up-regulated in HER2+ early onset nonLFS-BC, likely reflecting a loss of p53 regulation of genes such as BAX and TP53I3. In addition, cholesterol homeostasis and androgen response pathways were significantly up-regulated in LFS-BC; whereas they were significantly down-regulated in both ER+Her2- and HER2+ non-LFSBC. We then performed multiplex IHC on ER+ TP53WT nonLFS-BC (n=7), nonLFS-TNBC (n=16), and LFS-BC (n=33). We found that CD8+ T cell infiltration in LFS-BC was comparable to non-LFS triple-negative BC (TNBC), a tumor type which responds well to immune checkpoint blockade therapy, and higher than in ER+ nonLFS-BC. CD20+ infiltration in LFS-BC was lower than both TNBC and ER+ nonLFS-BC. Using single stain IHC and comparing an LFS breast tumor to its surrounding normal, we found that FoxP3+ Tregs, CD68+ and CD20+ cells were enriched in the tumors compared to surrounding normal breast tissue. Finally, we compared genomic, transcriptomic and immune cell differences between DCIS and IDC in LFS. Interestingly, all genomic instability measures and gene expression profiles were similar, including focal LOH and allelic imbalances. However, CD4+ and CD8+ T-cells and CD20+ B-cells became more excluded from the tumor tissue with increasing stage of tumor. Using the ACT activity assay, we found that there was significantly higher Ki67+ and Granzyme B in LFS-DCIS as compared to LFS-IDC indicating active T-cell killing. Finally, FoxP3+ T-regulatory cell and CD68+ macrophages were lower in LFS-IDC compared to LFS-DCIS. Conclusions: Overall, our data suggest that TP53 related breast tumor formation, at least in the germline state, requires biallelic loss of TP53 as a first step. Loss of p53 tumor suppressive function in the female breast leads to focal genomic instability events, possibly with selection for ERBB2 amplification. p53 deficiency in LFS-BC leads to failure to induce apoptosis but maintained cell cycle arrest. LFS-BC resemble sporadic TNBC with high CD8+ T-cells but low CD20+ B-cells. Genomic instability and p53 transcriptional dysfunction occur very early in tumor formation; whereas the immune microenvironment evolves to be more tumor supportive during the progression from DCIS to IDC in LFS-BC. This work provides the first insights into the mechanism of germline TP53 mutation driven breast tumor formation in humans. Citation Format: Kara N. Maxwell. Distinct genomic and immunologic tumor evolution in germline TP53-driven breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr NG02.

Oncolytic adenovirus encoding apolipoprotein A1 suppresses metastasis of triple-negative breast cancer in mice

BackgroundDysregulation of cholesterol metabolism is associated with the metastasis of triple-negative breast cancer (TNBC). Apolipoprotein A1 (ApoA1) is widely recognized for its pivotal role in regulating cholesterol efflux and maintaining cellular cholesterol homeostasis. However, further exploration is needed to determine whether it inhibits TNBC metastasis by affecting cholesterol metabolism. Additionally, it is necessary to investigate whether ApoA1-based oncolytic virus therapy can be used to treat TNBC.MethodsIn vitro experiments and mouse breast cancer models were utilized to evaluate the molecular mechanism of ApoA1 in regulating cholesterol efflux and inhibiting breast cancer progression and metastasis. The gene encoding ApoA1 was inserted into the adenovirus genome to construct a recombinant adenovirus (ADV-ApoA1). Subsequently, the efficacy of ADV-ApoA1 in inhibiting the growth and metastasis of TNBC was evaluated in several mouse models, including orthotopic breast cancer, spontaneous breast cancer, and human xenografts. In addition, a comprehensive safety assessment of Syrian hamsters and rhesus monkeys injected with oncolytic adenovirus was conducted.ResultsThis study found that dysregulation of cholesterol homeostasis is critical for the progression and metastasis of TNBC. In a mouse orthotopic model of TNBC, a high-cholesterol diet promoted lung and liver metastasis, which was associated with keratin 14 (KRT14), a protein responsible for TNBC metastasis. Furthermore, studies have shown that ApoA1, a cholesterol reverse transporter, inhibits TNBC metastasis by regulating the cholesterol/IKBKB/FOXO3a/KRT14 axis. Moreover, ADV-ApoA1 was found to promote cholesterol efflux, inhibit tumor growth, reduce lung metastasis, and prolonged the survival of mice with TNBC. Importantly, high doses of ADV-ApoA1 administered intravenously and subcutaneously were well tolerated in rhesus monkeys and Syrian hamsters.ConclusionsThis study provides a promising oncolytic virus treatment strategy for TNBC based on targeting dysregulated cholesterol metabolism. It also establishes a basis for subsequent clinical trials of ADV-ApoA1 in the treatment of TNBC.

Altered Brain Cholesterol Machinery in a Down Syndrome Mouse Model: A Possible Common Feature with Alzheimer's Disease.

Down syndrome (DS) is a complex chromosomal disorder considered as a genetically determined form of Alzheimer's disease (AD). Maintenance of brain cholesterol homeostasis is essential for brain functioning and development, and its dysregulation is associated with AD neuroinflammation and oxidative damage. Brain cholesterol imbalances also likely occur in DS, concurring with the precocious AD-like neurodegeneration. In this pilot study, we analyzed, in the brain of the Ts2Cje (Ts2) mouse model of DS, the expression of genes encoding key enzymes involved in cholesterol metabolism and of the levels of cholesterol and its main precursors and products of its metabolism (i.e., oxysterols). The results showed, in Ts2 mice compared to euploid mice, the downregulation of the transcription of the genes encoding the enzymes 3-hydroxy-3-methylglutaryl-CoA reductase and 24-dehydrocholesterol reductase, the latter originally recognized as an indicator of AD, and the consequent reduction in total cholesterol levels. Moreover, the expression of genes encoding enzymes responsible for brain cholesterol oxidation and the amounts of the resulting oxysterols were modified in Ts2 mouse brains, and the levels of cholesterol autoxidation products were increased, suggesting an exacerbation of cerebral oxidative stress. We also observed an enhanced inflammatory response in Ts2 mice, underlined by the upregulation of the transcription of the genes encoding for α-interferon and interleukin-6, two cytokines whose synthesis is increased in the brains of AD patients. Overall, these results suggest that DS and AD brains share cholesterol cycle derangements and altered oxysterol levels, which may contribute to the oxidative and inflammatory events involved in both diseases.

Phytosterols in human serum as measured using a liquid chromatography tandem mass spectrometry

Phytosterols are lipophilic compounds found in plants with structural similarity to mammalian cholesterol. They cannot be endogenously produced by mammals and therefore always originate from diet. There has been increased interest in dietary phytosterols over the last few decades due to their association with a variety of beneficial health effects including low-density lipoprotein cholesterol lowering, anti-inflammatory and anti-cancerous effects. They are proposed as potential moderators for diseases associated with the central nervous system where cholesterol homeostasis is found to be imperative (multiple sclerosis, dementia, etc.) due to their ability to reach the brain. Here we utilised an enzyme-assisted derivatisation for sterol analysis (EADSA) in combination with a liquid chromatography tandem mass spectrometry (LC-MSn) to characterise phytosterol content in human serum. As little as 100 fg of plant sterol was injected on a reversed phase LC column. The method allows semi-quantitative measurements of phytosterols and their derivatives simultaneously with measurement of cholesterol metabolites. The identification of phytosterols in human serum was based on comparison of their LC retention times and MS2, MS3 spectra with a library of authentic standards. Free campesterol serum concentration was in the range from 0.30 - 4.10µg/mL, β-sitosterol 0.16 - 3.37µg/mL and fucosterol was at lowest concentration range from 0.05 - 0.38µg/mL in ten individuals. This analytical methodology could be applied to the analysis of other biological fluids and tissues.

Membrane specificity of the human cholesterol transfer protein STARD4

STARD4 regulates cholesterol homeostasis by transferring cholesterol between the plasma membrane and endoplasmic reticulum. The STARD4 structure features a helix-grip fold surrounding a large hydrophobic cavity holding the sterol. Its access is controlled by a gate formed by the Ω1 and Ω4 loops and the C-terminal α-helix. Little is known about the mechanisms by which STARD4 binds to membranes and extracts/releases cholesterol. All available structures of STARD4 are without a bound sterol and display the same closed conformation of the gate. The cholesterol transfer activity of the mouse STARD4 is enhanced in the presence of anionic lipids, and in particular of phosphatidylinositol biphosphates (PIP2) for which two binding sites were proposed on the mouse STARD4 surface. Yet only one of these sites is conserved in human STARD4. We here report the results of a liposome microarray-based assay and microseconds-long molecular dynamics simulations of human STARD4 with complex lipid bilayers mimicking the composition of the donor and acceptor membranes. We show that the binding of apo form of human STARD4 is sensitive to the presence of PIP2 through two specific binding sites, one of which was not identified on mouse STARD4. We report two novel conformations of the gate in holo-STARD4: a yet-unobserved close conformation and an open conformation of Ω4 shedding light on the opening/closure mechanism needed for cholesterol uptake/release. Overall, the modulation of human STARD4 membrane-binding by lipid composition, and by the presence of the cargo supports the capacity of human STARD4 to achieve directed transfer between specific organelle membranes.

Specific circulating miRNA are associated with plasma lipids in a healthy American cohort.

Low-density lipoprotein cholesterol (LDL-c) is both a therapeutic target and a risk factor for cardiovascular disease (CVD). MicroRNA (miRNA) have been shown to regulate cholesterol homeostasis, and miRNA in blood circulation have been linked to hypercholesterolemia. However, few studies to date have associated miRNA with phenotypes like LDL-c in a healthy population. To this end, we analyzed circulating miRNA in relation to LDL-c in a healthy cohort of 353 participants using two separate bioinformatic approaches. The first approach found that miR-15b-5p and miR-16-5p were upregulated in individuals with at-risk levels of LDL-c. The second approach identified two miRNA clusters, one that positively and a second that negatively, correlated with LDL-c. Included in the cluster that positively correlated with LDL-c were miR-15b-5p and miR-16-5p as well as other miRNA from the miR-15/107, miR-30, and let-7 families. Cross-species analyses suggested that several miRNA that associated with LDL-c are conserved between mice and humans. Finally, we examined the influence of diet on circulating miRNA. Our results robustly linked circulating miRNA with LDL-c suggesting that miRNA could be used as biomarkers for hypercholesterolemia or targets for developing cholesterol-lowering drugs.