Target Of Statins Research Articles

Identifying Translational Longevity Targets With Genetically Mediated Transcriptome-Wide Association Studies

We hypothesized that trait associations with genetically mediated gene expression could be used to screen for genes that are good candidates for translational studies of longevity. We compiled a collection of genetically-mediated transcriptome-wide association studies using 33 traits and outcomes from large-scale, publicly-available GWAS meta-analysis results. The traits/outcomes were grouped within eight categories (aging, anthropometric, cardiovascular, inflammation, lung function, metabolic, musculoskeletal, and neurological). To test the utility of this approach, we examined trait associations with the drug target of statins, and we correctly identified known therapeutic effects and adverse events of statins. Specifically addressing the hypothesis, we examined a collection of candidate longevity-associated genes and identified one gene associated with lifespan that appears to also be associated with protection from atrial fibrillation and hearing impairment without being associated with adverse events. This screening approach can be used to prioritize gene targets for longevity translational efforts.

Atorvastatin and pravastatin stimulate nitric oxide and reactive oxygen species generation, affect mitochondrial network architecture and elevate nicotinamide N-methyltransferase level in endothelial cells.

Statins belong to the most often prescribed medications, which efficiently normalise hyperlipidaemia and prevent cardiovascular complications in obese and diabetic patients. However, beside expected therapeutic results based on the inhibition of 3-hydroxyl-3-methylglutaryl-CoA reductase, these drugs exert multiple side effects of poorly understood characteristic. In this study, side effects of pravastatin and atorvastatin on EA.hy926 endothelial cell line were investigated. It was found that both statins activate proinflammatory response, elevate nitric oxide and reactive oxygen species (ROS) generation and stimulate antioxidative response in these cells. Moreover, only slight stimulation of the mitochondrial biogenesis and significant changes in the mitochondrial network organisation have been noted. Although biochemical bases behind these effects are not clear, they may partially be explained as an elevation of AMP-activated protein kinase (AMPK) activity and an increased activating phosphorylation of sirtuin 1 (Sirt1), which were observed in statins-treated cells. In addition, both statins increased nicotinamide N-methyltransferase (NNMT) protein level that may explain a reduced fraction of methylated histone H3. Interestingly, a substantial reduction of the total level of histone H3 in cells treated with pravastatin but not atorvastatin was also observed. These results indicate a potential additional biochemical target for statins related to reduced histone H3 methylation due to increased NNMT protein level. Thus, NNMT may directly modify gene activity.

HMG-CoA Reductase Inhibitors as Drug Leads against Naegleria fowleri

Primary amebic meningoencephalitis (PAM), caused by the free-living ameba Naegleria fowleri, has a fatality rate of over 97%. Treatment of PAM relies on amphotericin B in combination with other drugs, but few patients have survived with the existing drug treatment regimens. Therefore, development of effective drugs is a critical unmet need to avert deaths from PAM. Since ergosterol is one of the major sterols in the membrane of N. fowleri, disruption of isoprenoid and sterol biosynthesis by small-molecule inhibitors may be an effective intervention strategy against N. fowleri. The genome of N. fowleri contains a gene encoding HMG-CoA reductase (HMGR); the catalytic domains of human and N. fowleri HMGR share <60% sequence identity with only two amino acid substitutions in the active site of the enzyme. Considering the similarity of human and N. fowleri HMGR, we tested well-tolerated and widely used HMGR inhibitors, known as cholesterol-lowering statins, against N. fowleri. We identified blood-brain-barrier-permeable pitavastatin as a potent amebicidal agent against the U.S., Australian, and European strains of N. fowleri. Pitavastatin was equipotent to amphotericin B against the European strain of N. fowleri; it killed about 80% of trophozoites within 16 h of drug exposure. Pretreatment of trophozoites with mevalonate, the product of HMGR, rescued N. fowleri from inhibitory effects of statins, demonstrating that HMGR of N. fowleri is the target of statins. Because of the good safety profile and availability for both adult and pediatric uses, consideration should be given to repurposing the fast-acting pitavastatin for the treatment of PAM.

Statin-Associated Autoimmune Myopathy: Current Perspectives.

Although generally well tolerated, statin users frequently report muscle-related side effects, ranging from self-limiting myalgias to rhabdomyolysis or the rare clinical entity of statin-associated immune-mediated necrotizing myopathy (IMNM). Statin-associated IMNM is based on the development of autoantibodies against 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme in cholesterol synthesis and the pharmacologic target of statins, and leads to a necrotizing myopathy requiring immunosuppressive therapy. This review attempts to recapitulate the diverse aspects of anti-HMGCR IMNM, including clinical presentation, diagnostic modalities, genetic risk associations, therapeutic options and potential pathogenetic pathways.

Association Between Genetically Proxied Inhibition of HMG-CoA Reductase and Epithelial Ovarian Cancer

Preclinical and epidemiological studies indicate a potential chemopreventive role of statins in epithelial ovarian cancer risk. To evaluate the association of genetically proxied inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (ie, genetic variants related to lower function of HMG-CoA reductase, target of statins) with epithelial ovarian cancer among the general population and in BRCA1/2 mutation carriers. Single-nucleotide polymorphisms (SNPs) in HMGCR, NPC1L1, and PCSK9 associated with low-density lipoprotein (LDL) cholesterol in a genome-wide association study (GWAS) meta-analysis (N ≤196 475) were used to proxy therapeutic inhibition of HMG-CoA reductase, Niemann-Pick C1-Like 1 (NPC1L1) and proprotein convertase subtilisin/kexin type 9 (PCSK9), respectively. Summary statistics were obtained for these SNPs from a GWAS meta-analysis of case-control analyses of invasive epithelial ovarian cancer in the Ovarian Cancer Association Consortium (OCAC; N = 63 347) and from a GWAS meta-analysis of retrospective cohort analyses of epithelial ovarian cancer among BRCA1/2 mutation carriers in the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA; N = 31 448). Across the 2 consortia, participants were enrolled between 1973 and 2014 and followed up through 2015. OCAC participants came from 14 countries and CIMBA participants came from 25 countries. SNPs were combined into multi-allelic models and mendelian randomization estimates representing lifelong inhibition of targets were generated using inverse-variance weighted random-effects models. Primary exposure was genetically proxied inhibition of HMG-CoA reductase and secondary exposures were genetically proxied inhibition of NPC1L1 and PCSK9 and genetically proxied circulating LDL cholesterol levels. Overall and histotype-specific invasive epithelial ovarian cancer (general population) and epithelial ovarian cancer (BRCA1/2 mutation carriers), measured as ovarian cancer odds (general population) and hazard ratio (BRCA1/2 mutation carriers). The OCAC sample included 22 406 women with invasive epithelial ovarian cancer and 40 941 control individuals and the CIMBA sample included 3887 women with epithelial ovarian cancer and 27 561 control individuals. Median ages for the cohorts ranged from 41.5 to 59.0 years and all participants were of European ancestry. In the primary analysis, genetically proxied HMG-CoA reductase inhibition equivalent to a 1-mmol/L (38.7-mg/dL) reduction in LDL cholesterol was associated with lower odds of epithelial ovarian cancer (odds ratio [OR], 0.60 [95% CI, 0.43-0.83]; P = .002). In BRCA1/2 mutation carriers, genetically proxied HMG-CoA reductase inhibition was associated with lower ovarian cancer risk (hazard ratio, 0.69 [95% CI, 0.51-0.93]; P = .01). In secondary analyses, there were no significant associations of genetically proxied inhibition of NPC1L1 (OR, 0.97 [95% CI, 0.53-1.75]; P = .91), PCSK9 (OR, 0.98 [95% CI, 0.85-1.13]; P = .80), or circulating LDL cholesterol (OR, 0.98 [95% CI, 0.91-1.05]; P = .55) with epithelial ovarian cancer. Genetically proxied inhibition of HMG-CoA reductase was significantly associated with lower odds of epithelial ovarian cancer. However, these findings do not indicate risk reduction from medications that inhibit HMG-CoA reductase; further research is needed to understand whether there is a similar association with such medications.

Lipid lowering and Alzheimer disease risk: A mendelian randomization study.

ObjectiveTo examine whether genetic variation affecting the expression or function of lipid‐lowering drug targets is associated with Alzheimer disease (AD) risk, to evaluate the potential impact of long‐term exposure to corresponding therapeutics.MethodsWe conducted Mendelian randomization analyses using variants in genes that encode the protein targets of several approved lipid‐lowering drug classes: HMGCR (encoding the target for statins), PCSK9 (encoding the target for PCSK9 inhibitors, eg, evolocumab and alirocumab), NPC1L1 (encoding the target for ezetimibe), and APOB (encoding the target of mipomersen). Variants were weighted by associations with low‐density lipoprotein cholesterol (LDL‐C) using data from lipid genetics consortia (n up to 295,826). We meta‐analyzed Mendelian randomization estimates for regional variants weighted by LDL‐C on AD risk from 2 large samples (total n = 24,718 cases, 56,685 controls).ResultsModels for HMGCR, APOB, and NPC1L1 did not suggest that the use of related lipid‐lowering drug classes would affect AD risk. In contrast, genetically instrumented exposure to PCSK9 inhibitors was predicted to increase AD risk in both of the AD samples (combined odds ratio per standard deviation lower LDL‐C inducible by the drug target = 1.45, 95% confidence interval = 1.23–1.69). This risk increase was opposite to, although more modest than, the degree of protection from coronary artery disease predicted by these same methods for PCSK9 inhibition.InterpretationWe did not identify genetic support for the repurposing of statins, ezetimibe, or mipomersen for AD prevention. Notwithstanding caveats to this genetic evidence, pharmacovigilance for AD risk among users of PCSK9 inhibitors may be warranted. ANN NEUROL 2020;87:30–39

Cloning, Purification, and Characterization of the Catalytic C-Terminal Domain of the Human 3-Hydroxy-3-methyl glutaryl-CoA Reductase: An Effective, Fast, and Easy Method for Testing Hypocholesterolemic Compounds.

3-hydroxy-3-methyl glutaryl-CoA reductase, also known as HMGR, plays a crucial role in regulating cholesterol biosynthesis and represents the main pharmacological target of statins. In mammals, this enzyme localizes to the endoplasmic reticulum membrane. HMGR includes different regions, an integral N-terminal domain connected by a linker-region to a cytosolic C-terminal domain, the latter being responsible for enzymatic activity. The aim of this work was to design a simple strategy for cloning, expression, and purification of the catalytic C-terminal domain of the human HMGR (cf-HMGR), in order to spectrophotometrically test its enzymatic activity. The recombinant cf-HMGR protein was heterologously expressed in Escherichia coli, purified by Ni+-agarose affinity chromatography and reconstituted in its active form. MALDI mass spectrometry was adopted to monitor purification procedure as a technique orthogonal to the classical Western blot analysis. Protein identity was validated by MS and MS/MS analysis, confirming about 82% of the recombinant sequence. The specific activity of the purified and dialyzed cf-HMGR preparation was enriched about 85-fold with respect to the supernatant obtained from cell lysate. The effective, cheap, and easy method here described could be useful for screening statin-like molecules, so simplifying the search for new drugs with hypocholesterolemic effects.

Statins interfere with the attachment of S. cerevisiae mtDNA to the inner mitochondrial membrane

The 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme of the mevalonate pathway for the synthesis of cholesterol in mammals (ergosterol in fungi), is inhibited by statins, a class of cholesterol lowering drugs. Indeed, statins are in a wide medical use, yet statins treatment could induce side effects as hepatotoxicity and myopathy in patients. We used Saccharomyces cerevisiae as a model to investigate the effects of statins on mitochondria. We demonstrate that statins are active in S.cerevisiae by lowering the ergosterol content in cells and interfering with the attachment of mitochondrial DNA to the inner mitochondrial membrane. Experiments on murine myoblasts confirmed these results in mammals. We propose that the instability of mitochondrial DNA is an early indirect target of statins.

Current perspectives on statins as potential anti-cancer therapeutics: clinical outcomes and underlying molecular mechanisms.

Statins have been shown to inhibit cell proliferation in vitro and tumor growth in animal models. Various studies have also shown a decreased cancer-specific mortality rate in patients who were prescribed these medications. Statins inhibit 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme of the mevalonate pathway. Statins induce tumour-specific apoptosis through mitochondrial apoptotic signaling pathways, which are activated by the suppression of mevalonate or geranylgeranyl pyrophosphate (GGPP) biosynthesis. However, there is no consensus on the molecular targets of statins for their anti-cancer effects. Several studies have been conducted to further assess the association between statin use and mortality in different types of cancer. In this review, current perspectives on clinical significance of statins in prevention and treatment of various types of cancers and proposed mechanisms are discussed.

Elevated N‐methyltransferase expression induced by hepatic stellate cells contributes to the metastasis of hepatocellular carcinoma via regulation of the CD44v3 isoform

The cross‐talk between hepatic stellate cells (HSCs) and hepatic carcinoma cells contributes to hepatocellular carcinoma (HCC) progression, but the underlying mechanism is largely unknown. We report here that activated HSCs induce upregulation of nicotinamide N‐methyltransferase (NNMT), which is known to regulate multiple metabolic pathways in hepatoma cells of the liver. High levels of NNMT in HCC tissues were positively correlated with vascular invasion, increased serum HBV‐DNA levels, and distant metastasis. In addition, functional assays showed that NNMT promoted HCC cell invasion and metastasis by altering the histone H3 methylation on 27 methylation pattern and transcriptionally activating cluster of differentiation 44 (CD44). NNMT‐mediated N6‐methyladenosine modification of CD44 mRNA resulted in the formation of a CD44v3 splice variant, while its product 1‐methyl‐nicotinamide stabilized CD44 protein by preventing ubiquitin‐mediated degradation. Finally, NNMT was also shown to be a target of statins that inhibited metastasis of hepatoma cells. Taken together, our study shows for the first time that the NNMT/CD44v3 axis regulates HCC metastasis and presents NNMT as a promising prognostic biomarker and therapeutic target for HCC.

Improving coding and primary care management for patients with chronic kidney disease: an observational controlled study in East London.

The UK national chronic kidney disease (CKD) audit in primary care shows diagnostic coding in the electronic health record for CKD averages 70%, with wide practice variation. Coding is associated with improvements to risk factor management; CKD cases coded in primary care have lower rates of unplanned hospital admission. To increase diagnostic coding of CKD (stages 3-5) and primary care management, including blood pressure to target and prescription of statins to reduce cardiovascular disease risk. Controlled, cross-sectional study in four East London clinical commissioning groups (CCGs). Interventions to improve coding formed part of a larger system change to the delivery of renal services in both primary and secondary care in East London. Quarterly anonymised data on CKD coding, blood pressure values, and statin prescriptions were extracted from practice computer systems for 1-year pre- and post-initiation of the intervention. Three intervention CCGs showed significant coding improvement over a 1 year period following the intervention (regression for post-intervention trend P<0.001). The CCG with highest coding rates increased from 76-90% of CKD cases coded; the lowest coding CCG increased from 52-81%. The comparison CCG showed no change in coding rates. Combined data from all practices in the intervention CCGs showed a significant increase in the proportion of cases with blood pressure achieving target levels (difference in proportion P<0.001) over the 2-year study period. Differences in statin prescribing were not significant. Clinically important improvements to coding and management of CKD in primary care can be achieved by quality improvement interventions that use shared data to track and monitor change supported by practice-based facilitation. Alignment of clinical and CCG priorities and the provision of clinical targets, financial incentives, and educational resource were additional important elements of the intervention.

NNMT Involvement in CD44v3 Regulation Induced by Hepatic Stellate Cells Contributes to the Metastasis of Hepatocarcinoma Cells

The crosstalk between hepatic stellate cells (HSCs) and hepatic carcinoma cells contributes to hepatocellular carcinoma (HCC) progression, although the underlying mechanism is largely unknown. We found that activated HSCs upregulated nicotinamide (NAM) N-methyltransferase (NNMT) expression in hepatoma cells. NNMT regulates multiple metabolic pathways in the liver, and aberrantly high levels of NNMT in the HCC tissues were positively correlated with vascular invasion, serum HBV levels and distant metastasis in our study. Functional assays showed that NNMT promoted cell migration, invasion and metastasis in vitro and in vivo. Mechanistically, NNMT regulated the intracellular methylation potential which in turn altered histone H3K27 methylation pattern, resulting in the transcriptional activation of CD44. NNMT-mediated m6A modification of the CD44 mRNA resulted in the formation of the CD44v3 splice variant, while its product 1-MNA stabilized CD44 protein by preventing ubiquitin-mediated degradation. Finally, NNMT was also a target of statins which inhibited the metastatic ability of hepatoma cells. Taken together, our study provides evidence for the first time on the potential role of the NNMT/CD44v3 axis in regulating HCC metastasis, and presents NNMT as a promising prognostic biomarker and therapeutic target for HCC. Funding Statement: This study was supported by the National Natural Science Foundation of China (No.81672418 and 81871961, to Zhenyu Yin. No. 81802344,to Jie Li. No. 81572335,to Wenxiu Zhao) and the Xiamen Science and Technology Project of People-benefit (No. 3502Z20174089, to J.L.). Declaration of Interests: All of the authors have declared that no competing interests exist. Ethics Approval Statement: Specimen collection was performed after obtaining informed consent from each patient, and the utilization of the tumor materials for research purposes was carried out in accordance with the approved guidelines and approved by the Ethics Committee (No: 20111008) of Zhong Shan Hospital Xiamen University

Mendelian Randomization Study of ACLY and Cardiovascular Disease

BackgroundATP citrate lyase is an enzyme in the cholesterol–biosynthesis pathway upstream of 3-hydroxy-3-methylglutaryl–coenzyme A reductase (HMGCR), the target of statins. Whether the genetic inhibition of ATP citrate lyase is associated with deleterious outcomes and whether it has the same effect, per unit decrease in the low-density lipoprotein (LDL) cholesterol level, as the genetic inhibition of HMGCR is unclear.MethodsWe constructed genetic scores composed of independently inherited variants in the genes encoding ATP citrate lyase (ACLY) and HMGCR to create instruments that mimic the effect of ATP citrate lyase inhibitors and HMGCR inhibitors (statins), respectively. We then compared the associations of these genetic scores with plasma lipid levels, lipoprotein levels, and the risk of cardiovascular events and cancer.ResultsA total of 654,783 participants, including 105,429 participants who had major cardiovascular events, were included in the study. The ACLY and HMGCR scores were associated with similar patterns of changes in plasma lipid and lipoprotein levels and with similar effects on the risk of cardiovascular events per decrease of 10 mg per deciliter in the LDL cholesterol level: odds ratio for cardiovascular events, 0.823 (95% confidence interval [CI], 0.78 to 0.87; P=4.0×10−14) for the ACLY score and 0.836 (95% CI, 0.81 to 0.87; P=3.9×10−19) for the HMGCR score. Neither lifelong genetic inhibition of ATP citrate lyase nor lifelong genetic inhibition of HMGCR was associated with an increased risk of cancer.ConclusionsGenetic variants that mimic the effect of ATP citrate lyase inhibitors and statins appeared to lower plasma LDL cholesterol levels by the same mechanism of action and were associated with similar effects on the risk of cardiovascular disease per unit decrease in the LDL cholesterol level. (Funded by Esperion Therapeutics and others.)

From the Circulation Family of Journals.

From the Circulation Family of Journals.

Genetic Assessment of Potential Long-Term On-Target Side Effects of PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Inhibitors.

Although short-term trials have suggested that PCSK9 (proprotein convertase subtilisin/kexin type 9) inhibitors are safe and reduce risk of cardiovascular diseases, their long-term safety is unclear. Genetic variants associated with lower activity of a gene can act as proxies to identify potential long-term side effects of drugs as recently exemplified by association of LDL (low-density lipoprotein)-lowering variants in the HMGCR (target for statins) and PCSK9 genes with increased risk of type 2 diabetes mellitus (T2DM). However, analyses of the full spectrum of potential side effects of PCSK9 inhibition using a genetic approach have not been undertaken. We examined the association of an LDL-lowering variant in the PCSK9 gene (T allele of rs1159147), as well as 2 LDL-lowering HGCMR variants (G allele of rs17238484 and T allele of rs12916) with 80 diseases and traits in up to 479 522 individuals in UK Biobank. The PCSK9 T allele was significantly (Bonferroni P<6.25×10-4) associated with risk of T2DM, increased body mass index, waist circumference, waist-hip ratio, diastolic blood pressure, type 1 diabetes mellitus, and insulin use. The HMGCR variants were also associated with risk of T2DM, although their previously reported associations with anthropometric traits were found to be confounded. Mediation analysis suggested that the association of the PCSK9 T allele with risk of T2DM but not diastolic blood pressure was largely independent of its association with body mass index and central obesity. Nominally significant associations of the PCSK9 T allele were also seen with peptic ulcer disease, depression, asthma, chronic kidney disease, and venous thromboembolism. Our findings support previous genetic analyses suggesting that long-term use of PCSK9 inhibitors, like statins, may be associated with increased risk of T2DM. Some other potential side effects need to be looked for in future studies of PCSK9 inhibitors, although we did not find signals that raise substantial concerns about their long-term safety.

Expression of gene and content of adiponectin in fatty tissue in patients with ischemic heart disease

The purpose of the study was to investigate the features of expression and adiponectin content in the adipocyte culture of subcutaneous, epicardial, and perivascular adipose tissue and the effect of various doses of rosuvastatin on these processes. 29 patients with coronary artery disease were examined. Adipocytes were isolated from the samples of SAT, EAT and PVAT which were taken during coronary artery bypass surgery, followed by cultivation in the presence of rosuvastatin and evaluation of gene expression and adiponectin concentration. Adipocytes SAT, EAT and PVAT differed in the level of adiponectin secretion and expression of its gene. On day 1 of cultivation the expression of the adiponectin gene in the EAT was 2.3 times lower than in the PVAT. On day 2 of cultivation the expression of the adiponectin gene was reduced both in the EAT and the PVAT as compared to the SAT. When rosuvastatin was added at a concentration of 1 mmol/L, adiponectin gene expression in PVAT was higher than when rosuvastatin was added at a concentration of 5 mmol/L, in the adipocyte culture of SAT effect was opposite. Thus, the adipocytes of EZhT and, to a greater extent, PAS, can be a therapeutic target for statins in the case of the pathological activation of adipose tissue.

Identification of DKK-1 as a novel mediator of statin effects in human endothelial cells

This study shows that DKK-1, a member of the Dickkopf family and a regulator of the Wnt pathways, represents a novel target of statins which, through the inhibition of HMG-CoA reductase and of non-steroidal isoprenoid intermediates, exert extra-beneficial effect in preventing atherosclerosis beyond their effect on the lipid profile. We found that atorvastatin downregulates DKK-1 protein (−88.3 ± 4.1%) and mRNA expression (−90 ± 4.2%) through the inhibition of Cdc42, Rho and Rac geranylgeranylated proteins. Further, a combined approach based on the integration of label-free quantitative mass spectrometry based-proteomics and gene silencing allowed us to demonstrate that DKK-1 itself mediates, at least in part, statin effects on human endothelial cells. Indeed, DKK-1 is responsible for the regulation of the 21% of the statin-modulated proteins, which include, among others, clusterin/apoJ, plasminogen activator inhibitor type 1 (PAI-1), myristoylated alanine-rich C-kinase substrate (MARCKS), and pentraxin 3 (PTX3). The Gene Ontology enrichment annotation revealed that DKK-1 is also a potential mediator of the extracellular matrix organization, platelet activation and response to wounding processes induced by statin. Finally, we found that plasma level of DKK-1 from cholesterol-fed rabbits treated with atorvastatin (2.5 mg/kg/day for 8 weeks) was lower (−42 ± 23%) than that of control animals. Thus, DKK-1 is not only a target of statin but it directly regulates the expression of molecules involved in a plethora of biological functions, thus expanding its role, which has been so far restricted mainly to cancer.

Interactions Between ABCB1 Genotype and Preoperative Statin Use Impact Clinical Outcomes Among Breast Cancer Patients.

Multiple clinical trials investigate statins' effects in breast cancer. The ABCB1 genotype appears to influence statin response and toxicity in the cardiovascular setting. This exploratory study aimed to investigate the interplay between preoperative statin use, ABCB1 genotype, and tumor-specific expression of the statin target 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in breast cancer. Preoperative statin use, ABCB1 C3435T genotype, and HMGCR expression in relation to outcome were analyzed in 985 primary breast cancer patients from a population-based prospective cohort in Sweden from 2002 to 2012. Preoperative statin use (n = 80) was not associated with ABCB1 C3435T genotype (n = 576), HMGCR expression (n = 848), or clinical outcomes. ABCB1 C3435T TT-carriers had lower risk of breast cancer events than any C-carriers (adjusted hazard ratio (HRadj) 0.74; 95%CI 0.49, 1.12), but only in non-statin users (Pinteraction = 0.042). Statin users with TT genotype had higher risk of distant metastasis (HRadj 4.37; 95%CI 1.20, 15.91; Pinteraction = 0.009) and shorter overall survival than other patients (HRadj 3.77; 95%CI 1.37, 10.39; Pinteraction = 0.019). In conclusion, there were nominally significant interactions between ABCB1 genotype and preoperative statin use on clinical outcomes, while preoperative statin use was not associated with outcomes. Since this is an exploratory study of the impact of the ABCB1 genotype in relation to statin use and clinical outcomes in the breast cancer setting, the results should be interpreted with caution and warrant replication in an independent cohort, preferably in a randomized setting. Since statin use is common in breast cancer patients, it would be of interest to further elucidate the clinical impact of the ABCB1 genotype in breast cancer.

A Mendelian randomization study of the effects of blood lipids on breast cancer risk

Observational studies have reported inconsistent associations between circulating lipids and breast cancer risk. Using results from >400,000 participants in two-sample Mendelian randomization, we show that genetically raised LDL-cholesterol is associated with higher risk of breast cancer (odds ratio, OR, per standard deviation, 1.09, 95% confidence interval, 1.02–1.18, P = 0.020) and estrogen receptor (ER)-positive breast cancer (OR 1.14 [1.05–1.24] P = 0.004). Genetically raised HDL-cholesterol is associated with higher risk of ER-positive breast cancer (OR 1.13 [1.01–1.26] P = 0.037). HDL-cholesterol-raising variants in the gene encoding the target of CETP inhibitors are associated with higher risk of breast cancer (OR 1.07 [1.03–1.11] P = 0.001) and ER-positive breast cancer (OR 1.08 [1.03–1.13] P = 0.001). LDL-cholesterol-lowering variants mimicking PCSK9 inhibitors are associated (P = 0.014) with lower breast cancer risk. We find no effects related to the statin and ezetimibe target genes. The possible risk-promoting effects of raised LDL-cholesterol and CETP-mediated raised HDL-cholesterol have implications for breast cancer prevention and clinical trials.

Abstract 216: Modeling Statin Hepatotoxicity with Acute Liver Specific Deletion of HmgCoA Reductase

Hmg-CoA Reductase (Hmgcr) catalyzes the conversion of Hmg-CoA to mevalonate, which is the rate-limiting step in the cholesterol biosynthetic pathway. Hmgcr is the target of statins, which are the front line therapy for hypercholesterolemia. Statin-responsiveness varies greatly between individuals, and liver toxicity and transaminase elevations are observed in 1-3% of patients. In addition to cholesterol, Hmgcr activity is also required for the synthesis of heme A, dolichol, ubiquinone (Coenzyme Q), farnesylated and geranylgeranylated proteins, isopentenyl tRNA, and vitamin K2. Surprisingly, very little is known about the effects of statins on these non-sterol isoprenoids in vivo , which may be essential for hepatocyte viability and function. The goal of this project is to investigate the effects of Hmgcr inhibition in the liver, in order to better understand the physiological regulation and function of the mevalonate pathway. We have developed a new inducible genetic model of Hmgcr deletion, which enables us acutely inhibit the mevalonate pathway in the liver, thus avoiding well-known compensatory responses to statins in rodents. Hmgcr floxed mice were injected with liver-specific AAV-Cre recombinase (AAV-Cre) and followed for 1, 2, 4 and 8 weeks. We observed massive apoptosis followed by a burst of hepatocyte proliferation at 2 weeks post-injection. We also observed compensatory upregulation of genes in the mevalonate pathway, likely a response to sterol depletion. Hepatocytes from AAV-Cre mice had expanded and swollen endoplasmic reticulum (ER), and upregulation of Chop and Bax, suggesting ER stress-induced apoptosis. Genetic analysis of AAV-Cre treated livers showed progressive loss of the null allele over time, indicating a selective advantage for hepatocytes that escaped complete Hmgcr deletion. The injection of a five-fold higher dose of AAV-Cre was acutely lethal in less than 2 weeks, confirming that liver Hmgcr activity is essential for survival. This new model will be used to identify the essential mevalonate-derived products in the liver, and the molecular pathways underlying statin hepatotoxicity and responsiveness.