Apolipoprotein E: a potent inhibitor of endothelial and tumor cell proliferation

Apolipoprotein E is a prognostic factor for pancreatic cancer and associates with immune infiltration

BACKGROUND

The expression level of apolipoprotein E (APOE) in pancreatic ductal adenocarcinoma (PDAC) and its effect on the prognosis of PDAC patients are not clear. The effect of APOE on the immune status of patients with PDAC has not been elucidated.

METHODS

We obtained pancreatic cancer data from the TCGA and GETx databases. Patients with PDAC who underwent pancreatic surgery at the Second Affiliated Hospital of Jiaxing University between 2012 and 2021 were included. Clinical pathological data were recorded, plasma APOE levels were measured, and tissue samples were collected. A tissue microarray was generated using the collected tissue samples. APOE and CD4 staining was performed to determine immunoreactive scores (IRSs). The expression of APOE in the plasma and tumour tissues of pancreatic cancer patients was analysed and compared. The correlations between plasma APOE levels, tissue APOE levels and clinicopathological characteristics were analysed. Survival prognosis was analysed using Kaplan-Meier survival analysis and Cox multivariate regression analysis. The correlations between APOE expression levels and immune biomarkers and immune cells were further analysed. Single-cell analysis of APOE distribution in various cells was performed on the TISCH website.

RESULTS

APOE was highly expressed in the tumour tissue of pancreatic cancer patients, and high plasma APOE levels were associated with poor prognosis. Females, patients with high-grade disease and patients with pancreatic head carcinoma had high plasma APOE levels. High APOE expression in tumour tissues was associated with good prognosis. Mononuclear macrophages in the pancreatic cancer microenvironment primarily expressed APOE. APOE levels positively correlated with immune biomarkers, such as CD8A, PDCD1, GZMA, CXCL10, and CXCL9, in the tumour microenvironment. APOE promoted CD4 + T cell or dendritic cell infiltration in the tumour microenvironment.

CONCLUSIONS

APOE may affect the occurrence and development of pancreatic cancer by regulating the infiltration of immune cells in the tumour microenvironment.

Comparative Serum Proteome Profiling of Canine Benign Prostatic Hyperplasia before and after Castration

BPH is the most prevalent prostatic condition in aging dogs. Nevertheless, clinical diagnosis and management remain inconsistent. This study employed in-solution digestion coupled with nano-liquid chromatography tandem mass spectrometry to assess serum proteome profiling of dogs with BPH and those dogs after castration. Male dogs were divided into two groups; control and BPH groups. In the BPH group, each dog was evaluated at two time points: Day 0 (BF subgroup) and Day 30 after castration (AT subgroup). In the BF subgroup, three proteins were significantly upregulated and associated with dihydrotestosterone: solute carrier family 5 member 5, tyrosine-protein kinase, and FRAT regulator of WNT signaling pathway 1. Additionally, the overexpression of polymeric immunoglobulin receptors in the BF subgroup hints at its potential as a novel protein linked to the BPH development process. Conversely, alpha-1-B glycoprotein (A1BG) displayed significant downregulation in the BF subgroup, suggesting A1BG's potential as a predictive protein for canine BPH. Finasteride was associated with increased proteins in the AT subgroup, including apolipoprotein C-I, apolipoprotein E, apolipoprotein A-II, TAO kinase 1, DnaJ homolog subfamily C member 16, PH domain and leucine-rich repeat protein phosphatase 1, neuregulin 1, and pseudopodium enriched atypical kinase 1. In conclusion, this pilot study highlighted alterations in various serum proteins in canine BPH, reflecting different pathological changes occurring in this condition. These proteins could be a source of potential non-invasive biomarkers for diagnosing this disease.

The Role of ApoE Serum Levels and ApoE Gene Polymorphisms in Patients with Laryngeal Squamous Cell Carcinoma

Recent studies have revealed that the inflammatory ApoE effect may play a significant role in various cancer development. However, this effect has still not been analyzed in patients with laryngeal squamous cell carcinoma (LSCC). In the present study, we evaluated two single nucleotide polymorphisms (SNPs) of ApoE (rs7412 and rs429358) and determined their associations with LSCC development and the LSCC patients’ five-year survival rate. Additionally, we analyzed serum ApoE levels using an enzyme-linked immunosorbent assay. A total of 602 subjects (291 histologically verified LSCC patients and 311 healthy controls) were involved in this study. The genotyping was carried out using the real-time PCR. We revealed that ApoE ε3/ε3 was associated with a 1.7-fold higher probability of developing LSCC (p = 0.001), with 1.7-fold increased odds of developing LSCC without metastasis to the lymph nodes (p = 0.002) and with a 2.0-fold increased odds of developing well-differentiated LSCC (p = 0.008), as well as 1.6-fold increased odds of developing poorly differentiated LSCC development (p = 0.012). The ApoE ε2/ε4 and ε3/ε4 genotypes were associated with a 2.9-fold and 1.5-fold decrease in the likelihood of developing LSCC (p = 0.042; p = 0.037, respectively). ApoE ε3/ε4 was found associated with a 2.4-fold decreased likelihood of developing well-differentiated LSCC (p = 0.013). Conclusion: ApoE ε2/ε4 and ε3/ε4 were found to play a protective role in LSCC development, while ApoE ε3/ε3 may have a risk position in LSCC development.

Atherogenesis, Transcytosis, and the Transmural Cholesterol Flux: A Critical Review

The recently described phenomenon of cholesterol-loaded low-density lipoproteins (LDL) entering the arterial wall from the lumen by transcytosis has been accepted as an alternative for the long-held concept that atherogenesis involves only passive LDL movement across an injured or dysfunctional endothelial barrier. This active transport of LDL can now adequately explain why plaques (atheromas) appear under an intact, uninjured endothelium. However, the LDL transcytosis hypothesis is still questionable, mainly because the process serves no clear physiological purpose. Moreover, central components of the putative LDL transcytosis apparatus are shared by the counter process of cholesterol efflux and reverse cholesterol transport (RCT) and therefore can essentially create an energy-wasting futile cycle and paradoxically be pro- and antiatherogenic simultaneously. Hence, by critically reviewing the literature, we wish to put forward an alternative interpretation that, in our opinion, better fits the experimental evidence. We assert that most of the accumulating cholesterol (mainly as LDL) reaches the intima not from the lumen by transcytosis, but from the artery's inner layers: the adventitia and media. We have named this directional cholesterol transport transmural cholesterol flux (TCF). We suggest that excess cholesterol, diffusing from the avascular (i.e., devoid of blood and lymph vessels) media's smooth muscle cells, is cleared by the endothelium through its apical membrane. A plaque is formed when this cholesterol clearance rate lags behind its rate of arrival by TCF.

Destabilizing heterochromatin by APOE mediates senescence

Apolipoprotein E (APOE) is a component of lipoprotein particles that function in the homeostasis of cholesterol and other lipids. Although APOE is genetically associated with human longevity and Alzheimer's disease, its mechanistic role in aging is largely unknown. Here, we used human genetic, stress-induced and physiological cellular aging models to explore APOE-driven processes in stem cell homeostasis and aging. We report that in aged human mesenchymal progenitor cells (MPCs), APOE accumulation is a driver for cellular senescence. By contrast, CRISPR-Cas9-mediated deletion of APOE endows human MPCs with resistance to cellular senescence. Mechanistically, we discovered that APOE functions as a destabilizer for heterochromatin. Specifically, increased APOE leads to the degradation of nuclear lamina proteins and a heterochromatin-associated protein KRAB-associated protein 1 via the autophagy-lysosomal pathway, thereby disrupting heterochromatin and causing senescence. Altogether, our findings uncover a role of APOE as an epigenetic mediator of senescence and provide potential targets to ameliorate aging-related diseases.

In silico identification of single nucleotide variations at CpG sites regulating CpG island existence and size

Genetic and epigenetic modifications of genes involved in the key regulatory pathways play a significant role in the pathophysiology and progression of multifactorial diseases. The present study is an attempt to identify single nucleotide variations (SNVs) at CpG sites of promoters of ACAT1, APOB, APOE, CYBA, FAS, FLT1, KSR2, LDLR, MMP9, PCSK9, PHOX2A, REST, SH2B3, SORT1 and TIMP1 genes influencing CpG island (CGI) existence and size associated with the pathophysiology of Diabetes mellitus, Coronary artery disease and Cancers. Promoter sequences located between -2000 to + 2000 bp were retrieved from the EPDnew database and predicted the CpG island using MethPrimer. Further, SNVs at CpG sites were accessed from NCBI, Ensembl while transcription factor (TF) binding sites were accessed using AliBaba2.1. CGI existence and size were determined for each SNV at CpG site with respect to wild type and variant allele by MethPrimer. A total of 200 SNVs at CpG sites were analyzed from the promoters of ACAT1, APOB, APOE, CYBA, FAS, FLT1, KSR2, LDLR, MMP9, PCSK9, PHOX2A, REST, SH2B3, SORT1 and TIMP1 genes. Of these, only 17 (8.5%) SNVs were found to influence the loss of CGI while 70 (35%) SNVs were found to reduce the size of CGI. It has also been found that 59% (10) of CGI abolishing SNVs are showing differences in binding of TFs. The findings of the study suggest that the candidate SNVs at CpG sites regulating CGI existence and size might influence the DNA methylation status and expression of genes involved in molecular pathways associated with several diseases. The insights of the present study may pave the way for new experimental studies to undertake challenges in DNA methylation, gene expression and protein assays.

Research progress on exosomal proteins as diagnostic markers of gastric cancer (review article)

Gastric cancer (GC) is one of the most common types of tumors and the most common cause of cancer mortality worldwide. The diagnosis of GC is critical to its prevention and treatment. Available tumor markers are the crucial step for GC diagnosis. Recent studies have shown that proteins in exosomes are potential diagnostic and prognostic markers for GC. Exosomes, secreted by cells, are cup-shaped with a diameter of 30–150 nm under the electron microscope. They are also surrounded by lipid bilayers and are widely found in various body fluids. Exosomes contain proteins, lipids and nucleic acid. The examination of exosomal proteins has the advantages of quickness, easy sampling, and low pain and cost, as compared with the routine inspection method of GC, which may lead to marked developments in GC diagnosis. This article summarized the exosomal proteins with a diagnostic and prognostic potential in GC, as well as exosomal proteins involved in GC progression.

Heart function assessment during aging in apolipoprotein E knock-out mice

BACKGROUND

Apolipoprotein (apo) E isoforms have strong correlations with metabolic and cardiovascular diseases. However, it is not clear if apoE has a role in development of non-ischemic cardiomyopathy. Our study aims to analyze the involvement of apoE in non-ischemic cardiomyopathy.

METHODS AND RESULTS

Serial echo-cardiographic measurements were performed in old wildtype and apoE deficient (apoE-/-) mice. Morphological and functional cardiac parameters were in normal range in both groups at the age of 12 month. At the age of 18 months, both groups had shown ventricular dilation and increased heart rates. However, the apoE-/- mice presented signs of diastolic dysfunction by hypertrophic changes in left ventricle, due probably to arterial hypertension. The right ventricle was not affected by age or genotype.  CONCLUSION: Even in the absence of high fat diet, apoE deficiency in mice induces mild changes in the cardiac function of the left ventricle during aging, by developing diastolic dysfunction, which leads to heart failure with preserved ejection fraction. However, further studies are necessary to conclude over the role of apoE in cardiac physiology and its involvement in development of heart failure.

Apolipoprotein E4 Is Associated with Right Ventricular Dysfunction in Dilated Cardiomyopathy-An Animal and In-Human Comparative Study

ApoE abnormality represents a well-known risk factor for cardiovascular diseases. Beyond its role in lipid metabolism, novel studies demonstrate a complex involvement of apoE in membrane homeostasis and signaling as well as in nuclear transcription. Due to the large spread of apoE isoforms in the human population, there is a need to understand the apoE’s role in pathological processes. Our study aims to dissect the involvement of apoE in heart failure. We showed that apoE-deficient rats present multiple organ damages (kidney, liver, lung and spleen) besides the known predisposition for obesity and affected lipid metabolism (two-fold increase in tissular damages in liver and one-fold increase in kidney, lung and spleen). Heart tissue also showed significant morphological changes in apoE^−/− rats, mostly after a high-fat diet. Interestingly, the right ventricle of apoE^−/− rats fed a high-fat diet showed more damage and affected collagen content (~60% less total collagen content and double increase in collagen1/collagen3 ratio) compared with the left ventricle (no significant differences in total collagen content or collagen1/collagen3 ratio). In patients, we were able to find a correlation between the presence of ε4 allele and cardiomyopathy (χ² = 10.244; p = 0.001), but also with right ventricle dysfunction with decreased TAPSE (15.3 ± 2.63 mm in ε4-allele-presenting patients vs. 19.8 ± 3.58 mm if the ε4 allele is absent, p < 0.0001*) and increased in systolic pulmonary artery pressure (50.44 ± 16.47 mmHg in ε4-allele-presenting patients vs. 40.68 ± 15.94 mmHg if the ε4 allele is absent, p = 0.0019). Our results confirm that the presence of the ε4 allele is a lipid-metabolism-independent risk factor for heart failure. Moreover, we show for the first time that the presence of the ε4 allele is associated with right ventricle dysfunction, implying different regulatory mechanisms of fibroblasts and the extracellular matrix in both ventricles. This is essential to be considered and thoroughly investigated before the design of therapeutical strategies for patients with heart failure.

Identification of Key Genes in Gastric Cancer by Bioinformatics Analysis

Gastric cancer (GC) is one of the most common malignancies of the digestive system with few genetic markers for its early detection and prevention. In this study, differentially expressed genes (DEGs) were analyzed using GEO2R from GSE54129 and GSE13911 of the Gene Expression Omnibus (GEO). Then, gene enrichment analysis, protein-protein interaction (PPI) network construction, and topological analysis were performed on the DEGs by the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, STRING, and Cytoscape. Finally, we performed survival analysis of key genes through the Kaplan-Meier plotter. A total of 1034 DEGs were identified in GC. GO and KEGG results showed that DEGs mainly enriched in plasma membrane, cell adhesion, and PI3K-Akt signaling pathway. Subsequently, the PPI network with 44 nodes and 333 edges was constructed, and 18 candidate genes in the network were focused on by centrality analysis and module analysis. Furthermore, data showed that high expressions of fibronectin 1(FN1), the tissue inhibitor of metalloproteinases 1 (TIMP1), secreted phosphoprotein 1 (SPP1), apolipoprotein E (APOE), and versican (VCAN) were related to poor overall survivals in GC patients. In summary, this study suggests that FN1, TIMP1, SPP1, APOE, and VCAN may act as the key genes in GC.

Apolipoprotein: prospective biomarkers in digestive tract cancer

Digestive tract cancer, which is characterized by high morbidity and mortality, seriously affects the quality of life of patients worldwide. The digestive tract has abundant blood supply and nutriment, providing a suitable environment for tumor cells. Under chemical, physical, and biological stimuli, the activated cancer-related genes promote tumorigenesis. The synthesis of apolipoprotein occurs in the liver, intestine, and other digestive organs. However, the functions of apolipoproteins are not limited to lipid metabolism. An increasing number of studies have revealed that apolipoproteins take part in the regulation of tumor behavior. Apolipoprotein A (apoA) has recently been acknowledged as a beneficial indicator of several cancers, including colon, hepatocellular, and pancreatic cancer. Apolipoprotein E (apoE) can affect tumor susceptibility on account of genetic polymorphism. Levels of apolipoprotein C (apoC), B (apoB), and D (apoD) also impact tumor progression and the prognosis of patients. However, because of individual, racial, and genetic differences, a consensus has not yet been reached. Based on clinical data and analysis, apolipoproteins could be a novel target and marker in tumor therapy and prevention.

Apolipoproteins, as the carrier proteins for lipids, are involved in the development of breast cancer

Apolipoproteins, the key components of lipoproteins, play vital roles in the combination and transportation of lipids. Numerous research articles have accumulated solid evidence that lipoproteins are closely related to various types of tumorigenesis. In this review, we focused on the associations between several apolipoproteins and breast carcinoma and distinguished the effects and significance of apolipoproteins in different locations to validate their roles in breast carcinoma development. For example, apoD and apoE in serum are viewed as risk factors for breast carcinoma. ApoD, apoE and apoA-I in mammary tissues inhibit tumor growth. Moreover, apoB, apoJ and apoA-I have the potential to function as diagnostic or prognostic markers in the clinic. ApoEdp and apoJ treatment on breast carcinoma could significantly restrict tumor growth. In general, the aim of this review was to further analyze the associations between some members of the apolipoprotein family and breast cancer.

Association of ApoE haplotype with clinical evidence of pituitary adenoma

PURPOSE

To evaluate the association of the presence, invasiveness, hormonal activity and recurrence of pituitary adenoma (PA) with ApoE genotypes and alleles.

MATERIALS AND METHODS

Our study group included 142 patients with PA and the control group included 256 healthy individuals. The genotyping of ApoE (rs7412 and rs429358) was performed using a real-time PCR method.

RESULTS

After statistical analysis we found that ApoE genotype E2/E3 was associated with 2.6-fold increased odds of active PA (OR = 2.609; 95%CI: 1.380-4.932; p = 0.003), while the presence of ApoE E3/E3 decreased odds of active PA by 65% (OR = 0.343; 95%CI: 0.205-0.575; p < 0.001). The frequency of the allele ε3 was lesser in the PA group (74.3% vs. 83%, p = 0.003) when compared to controls but it was statistically significantly more frequent in the invasive PA than in the noninvasive PA subgroup (80.4% vs. 65.5%, p = 0.005). The ApoE E2/E4 genotype was more frequent in the noninvasive PA subgroup (10.3% vs. 0%, p = 0.003) than in the invasive PA subgroup. The ApoE E4/E4 genotype was more frequent in the recurrent than in the non-recurrent PA subgroup (6.6% vs. 0%, p = 0.006). No associations between ApoE polymorphisms and Ki-67 labelling index were found.

CONCLUSION

The ApoE E2/E3 genotype is associated with the presence of PA while the ApoE genotype E2/E4 is associated with noninvasive PA development. The allele ε3 could possibly have a protective effect against PA. The genotype E4/E4 is associated with the development of recurrent PA.

Structure, synthesis and biological properties of the pentacyclic guanidinium alkaloids

The pentacyclic guanidinium alkaloids (PGAs) are a family of marine natural products that possess a polycyclic guanidine-containing core and a long alkyl chain tethered spermidine-derived tail that is rarely observed in other natural products. These natural products exhibit potent activities on a wide range of organisms and therefore have attracted the attention of many synthetic chemists; however, the structure-activity relationships and mechanisms of action of PGAs remain largely elusive. Herein we summarize the structure, synthesis, toxicity and mechanisms of action of PGAs and highlight their potential as chemical probes and/or therapeutic leads.

Severe pulmonary hypertension in aging female apolipoprotein E-deficient mice is rescued by estrogen replacement therapy

Background

Apolipoprotein E (ApoE) is a multifunctional protein, and its deficiency leads to the development of atherosclerosis in mice. Patients with pulmonary hypertension (PH) have reduced expression of ApoE in lung tissue. ApoE is known to inhibit endothelial and smooth muscle cell proliferation and has anti-inflammatory and anti-platelet aggregation properties. Young ApoE-deficient mice have been shown to develop PH on high fat diet. The combined role of female sex and aging in the development of PH has not been investigated before. Here, we investigated the development of PH in young and middle-aged (MA) female ApoE-deficient mice and explored the role of exogenous estrogen (E2) replacement therapy for the aging females.

Methods

Wild type (WT) and ApoE-deficient female mice (Young and MA) were injected with a single intraperitoneal dose of monocrotaline (MCT, 60 mg/kg). Some ApoE-deficient MA female mice that received MCT were also treated with subcutaneous E2 pellets (0.03 mg/kg/day) from day 21 to 30 after MCT injection. Direct cardiac catheterization was performed terminally to record right ventricular systolic pressure (RVSP). Right ventricular (RV), left ventricular (LV), and interventricular septum (IVS) were dissected and weighed. Lung sections were examined using trichrome and immunofluorescence staining. Western blot analyses of lung and RV lysates were performed.

Results

In WT female mice, the severity of PH was similar between young and MA mice as RVSP was not significantly different (RVSP = 38.2 ± 1.2 in young vs. 40.5 ± 8.3 mmHg in MA, p < 0.05). In ApoE-deficient mice, MA females developed significantly severe PH (RVSP = 63 ± 10 mmHg) compared to young females (RVSP; 36 ± 3 mmHg, p < 0.05 vs. MA female). ApoE-deficient MA females also developed more severe RV hypertrophy compared to young females (RV hypertrophy index (RV/[LV + IVS]) = 0.53 ± 0.06 vs. 0.33 ± 0.01, p < 0.05). ApoE-deficient MA female mice manifested increased peripheral pulmonary artery muscularization and pulmonary fibrosis. E2 treatment of MA female ApoE-deficient mice resulted in a significant decrease in RVSP, reversal of pulmonary vascular remodeling, and RV hypertrophy. In MA female ApoE-deficient mice with PH, only the expression of ERβ in the lungs, but not in RV, was significantly downregulated, and it was restored by E2 treatment. The expression of ERα was not affected in either lungs or RV by PH. GPR30 was only detected in the RV, and it was not affected by PH in MA female ApoE-deficient mice.

Conclusions

Our results suggest that only aging female ApoE-deficient but not WT mice develop severe PH compared to younger females. Exogenous estrogen therapy rescued PH and RV hypertrophy in aging female ApoE-deficient mice possibly through restoration of lung ERβ.

Inverse relationship between Alzheimer's disease and cancer, and other factors contributing to Alzheimer's disease: a systematic review

Background

The AD etiology is yet not properly known. Interactions among environmental factors, multiple susceptibility genes and aging, contribute to AD. This study investigates the factors that play role in causing AD and how changes in cellular pathways contribute to AD.

Methods

PUBMED database, MEDLINE database and Google Scholar were searched with no date restrictions for published articles involving cellular pathways with roles in cancers, cell survival, growth, proliferation, development, aging, and also contributing to Alzheimer’s disease. This research explores inverse relationship between AD and cancer, also investigates other factors behind AD using several already published research literature to find the etiology of AD.

Results

Cancer and Alzheimer’s disease have inverse relationship in many aspects such as P53, estrogen, neurotrophins and growth factors, growth and proliferation, cAMP, EGFR, Bcl-2, apoptosis pathways, IGF-1, HSV, TDP-43, APOE variants, notch signals and presenilins, NCAM, TNF alpha, PI3K/AKT/MTOR pathway, telomerase, ROS, ACE levels. AD occurs when brain neurons have weakened growth, cell survival responses, maintenance mechanisms, weakened anti-stress responses such as Vimentin, Carbonic anhydrases, HSPs, SAPK. In cancer, these responses are upregulated and maintained. Evolutionarily conserved responses and maintenance mechanisms such as FOXO are impaired in AD.

Countermeasures or compensatory mechanisms by AD affected neurons such as Tau, Beta Amyloid, S100, are last attempts for survival which may be protective for certain time, or can speed up AD in Alzheimer’s microenvironment via C-ABL activation, GSK3, neuro-inflammation.

Conclusions

Alzheimer’s disease and Cancer have inverse relationship; many factors that are upregulated in any cancer to sustain growth and survival are downregulated in Alzheimer’s disease contributing to neuro-degeneration. When aged neurons or genetically susceptible neurons have weakened growth, cell survival and anti-stress responses, age related gene expression changes, altered regulation of cell death and maintenance mechanisms, they contribute to Alzheimer’s disease. Countermeasures by AD neurons such as Beta Amyloid Plaques, NFTs, S100, are last attempts for survival and this provides neuroprotection for certain time and ultimately may become pathological and speed up AD. This study may contribute in developing new potential diagnostic tests, interventions and treatments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0765-2) contains supplementary material, which is available to authorized users.

Strategies to Protect the Brain During Cardiac Surgery

Despite significant advances in cardiopulmonary by pass (CPB) technology, surgical techniques, and anes thetic management, central nervous system (CNS) com plications remain a common and costly problem after CPB. Stroke is often considered a rare and unprevent able complication of cardiac surgery. Recent studies have shown that through the use of echocardiography and historical risk stratification strategies, we can de fine which patients are at substantially greater risk for CNS injury. Through enhanced understanding of the etiology of stroke and perioperative factors, which are associated with potential for neuroprotection or injury extension, there now exists a greater potential than ever to substantially reduce neurological injury associ ated with cardiac surgery. Strategies and theories of stratifying patients at risk and secondarily reducing that risk are described, as well as consideration for early postoperative assessment to allow treatment when events occur.

Different Susceptibilities between Apoe- and Ldlr-Deficient Mice to Inflammation-Associated Colorectal Carcinogenesis

Hypercholesterolemia resulting in atherosclerosis is associated with an increased risk of ischemic heart disease and colorectal cancer (CRC). However, the roles of apoliprotein (Apo) E (Apoe) and low-density lipoprotein (Ldl) receptor (Ldlr) in colorectal carcinogenesis have not yet been investigated. In this study, we examined the susceptibility of Apoe-deficient and Ldlr-deficient mice, which are genetic animal models of atherosclerosis to azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colorectal carcinogenesis. In Experiment 1, male Apoe-deficient (n = 20) and wild type (WT) mice (C57BL/6J, n = 21) were treated with a single intraperitoneal (i.p.) injection of AOM (10 mg/kg body weight) and then given 1.5% DSS in drinking water for seven days. They were maintained up to week 20 and sacrificed for the histopathological examination of colorectal tumors. The mRNA expression of cyclooxygenase (Cox)-2, inducible nitric oxide synthase (Nos2), tumor necrosis factor (Tnf)-α interleukin (Il)-1β, and Il-6 was assayed in the colorectal mucosa. In Experiment 2, male Ldlr-deficient (n = 14) and WT mice (C57BL/6J, n = 10) were given a single i.p. injection of AOM (10 mg/kg body weight) and then given 2% DSS in drinking water for seven days. They were sacrificed at week 20 to evaluate their colorectum histopathologically. In Experiment 1, the multiplicity of CRCs was significantly higher in the Apoe-deficient mice (2.75 ± 1.48) than in the WT mice (0.62 ± 0.67). The serum lipoprotein levels in the Apoe-deficient mice were also significantly higher than in the WT mice. In Experiment 2, the incidence (29%) and multiplicity (0.50 ± 0.94) of CRCs in the Ldlr mice were significantly lower than in the WT mice (80% incidence and 3.10 ± 2.38 multiplicity). The mRNA expression of two inducible enzymes and certain pro-inflammatory cytokines in the colorectum of each genotype was greater than in the respective WT mice. The values in the Apoe-deficient mice were much greater than in the Ldlr mice. These findings suggest that Apoe-deficient mice showed increased susceptibility to inflammation-associated colorectal carcinogenesis due to their high reactivity to inflammatory stimuli.

Genetic Predictors of Perioperative Neurologic and Neuropsychological Injury and Recovery

Central nervous system (CNS) dysfunction after cardio pulmonary bypass represents a continuum from coma and focal stroke to cognitive deficits after surgery. Despite the marked increase in investigation of neuro logic and neurocognitive deficits after cardiac surgery, causative factors fail to predict the majority of the variance in the observed incidence of both early and late neurocognitive decline pointing to some inherent indi vidual susceptibility to injury. The authors' investigative team recently discovered a genetic association be tween late-onset Alzheimer's disease and the apolipo protein E (APOE, gene; apoE, protein) ∈-4 gene. This finding triggered many recent studies that have shown an important role of apoE in the determination of neurologic injury and recovery following a variety of acute ischemic insults including intracerebral hemor rhage, closed-head injury, as well as acute stroke and dementia pugilistica. Most important to the current discussion is the authors' recent report documenting preliminary evidence of an association of APOE4 with neurocognitive decline after cardiac surgery. This re view discusses the authors' hypothesis that the bio chemical products coded by this gene are not available to protect and repair the neurons of the CNS during cardiac surgery resulting in deficits of memory, atten tion, and concentration. Potential mechanisms of apoE's association with acute neurologic injury are discussed including regulation of the inflammatory response. The authors have recently determined that apoE, in vivo, modulates the release of nitric oxide and tumor necro sis factor a. This may compound the autonomic dysreg ulation recently reported in the aging population. The authors' preliminary data associating APOE4 with cogni tive impairment after cardiac surgery support this hy pothesis. The different potential mechanisms of apoE function in neuronal injury and recovery are not mutu ally exclusive, and it is likely that apoE modulates the CNS injury response at several functional levels.

Anti-migratory activity of marine alkaloid monanchocidin A - proteomics-based discovery and confirmation

Monanchocidin A (MonA) is a novel marine alkaloid with promising anti-cancer properties. We recently demonstrated its high efficacy in human urogenital cancers including germ cell tumors. Here, we applied a global proteome screening approach to investigate molecular targets and biological processes affected by MonA in the human cisplatin-resistant germ cell cancer cell line NCCIT-R. Bioinformatical analysis of the proteomics data predicted an effect of MonA on cancer cell migration. Thus, proteins known to be involved in cancer cell migration and invasion were chosen for further validation. The protein alterations identified by proteomics resulted from both, regulation of the total protein expression and post-transcriptional modifications. Among others, regulation of an isoform of vimentin, up-regulation of multiple apolipoprotein E isoforms, and inhibition of hypusination of eukaryotic translation initiation factor 5A-1 were found upon treatment with MonA. Further functional analyses were performed and revealed decreased cell migration and colony formation of cancer cells treated with MonA at non-cytotoxic and non-antiproliferative concentrations. This work provides further insights into the molecular mechanisms behind MonA bioactivity. Furthermore, our research is exemplary for the ability of proteomics to predict drug targets and mode of action of natural anti-cancer agents.

Apolipoprotein E epsilon 2 allele and low serum cholesterol as risk factors for gastric cancer in a Chinese Han population

Apolipoprotein E (apoE) mediates lipid metabolism both in peripheral and in the brain. The human APOE gene has three polymorphic alleles that influence the risk for various types of cancer and neurodegenerative diseases. A potential association between APOE allele and the risk for gastric cancer has been implicated, but the specific allele involved and potential associations with the subtype and the grade of cancer malignancy need further clarification. We screened the APOE genotype in 550 gastric cancer patients and 550 non-cancer control individuals and found that the presence of the APOE ε2 and lower serum total cholesterol are associated with an increased risk for gastric cancer (all P ≤ 0.0005). Interestingly, APOE ε2 is also correlated with increased risk for both intestinal and diffuse histotypes but not with TN classification or stage in gastric cancer patients, suggesting that APOE polymorphic alleles are associated with the risk of development but unlikely the progression of gastric cancer. Since ε2 carriers have lower levels of serum total cholesterol than non-ε2 carriers, our findings suggest that the increased risk for gastric cancer by APOE ε2 allele might be mediated through lowered serum total cholesterol levels.

Causal relevance of circulating high-density lipoprotein cholesterol with cancer: a Mendelian randomization meta-analysis

We summarized published data on the associations of apolipoprotein E (APOE) gene ε2/ε3/ε4 polymorphism with both cancer risk and circulating lipid profiles, aiming to examine the causal relevance between lipids and cancer risk. Article identification and data abstraction were conducted in duplicate and independently by two authors. Data were analyzed by STATA software. Twenty-five articles that examined the associations of APOE gene ε2/ε3/ε4 polymorphism with either cancer risk (n = 22) or circulating lipid changes (n = 4) were eligible. The presence of ε2 and ε4 alleles showed no overall associations with overall cancer risk when compared with ε3 allele. The ε4 allele was significantly associated with 1.40-fold (odds ratio or OR = 1.40; 95% confidence interval or CI: 1.00–1.94; P = 0.047) increased risk of developing cancer in Asian populations, and the presence of heterogeneity was low (I² = 37.6%). Carriers of ε3/ε4 genotype had a significant reduction in circulating HDL-C (WMD = −2.62; 95% CI: −4.19 to −1.04; P = 0.001) without heterogeneity (I² = 16.6%). The predicted odds of having cancer for 1 mg/dL reduction in circulating HDL-C was 1.14 (95% CI: 1.00 to 1.89). The findings of this Mendelian randomization meta-analysis demonstrate that reduced circulating HDL-C might be a potentially causal risk factor for the development of overall cancer in Asians.

Predicting response to vascular endothelial growth factor inhibitor and chemotherapy in metastatic colorectal cancer

BACKGROUND

Bevacizumab improves progression free survival (PFS) and overall survival (OS) in metastatic colorectal cancer patients however currently there are no biomarkers that predict response to this treatment. The aim of this study was to assess if differential protein expression can differentiate patients who respond to chemotherapy and bevacizumab, and to assess if select proteins correlate with patient survival.

METHODS

Pre-treatment serum from patients with metastatic colorectal cancer (mCRC) treated with chemotherapy and bevacizumab were divided into responders and nonresponders based on their progression free survival (PFS). Serum samples underwent immunoaffinity depletion and protein expression was analysed using two-dimensional difference gel electrophoresis (2D-DIGE), followed by LC-MS/MS for protein identification. Validation on selected proteins was performed on serum and tissue samples from a larger cohort of patients using ELISA and immunohistochemistry, respectively (n = 68 and n = 95, respectively).

RESULTS

68 proteins were identified following LC-MS/MS analysis to be differentially expressed between the groups. Three proteins (apolipoprotein E (APOE), angiotensinogen (AGT) and vitamin D binding protein (DBP)) were selected for validation studies. Increasing APOE expression in the stroma was associated with shorter progression free survival (PFS) (p = 0.0001) and overall survival (OS) (p = 0.01), DBP expression (stroma) was associated with shorter OS (p = 0.037). Increasing APOE expression in the epithelium was associated with a longer PFS and OS, and AGT epithelial expression was associated with a longer PFS (all p < .05). Increasing serum AGT concentration was associated with shorter OS (p = 0.009).

CONCLUSIONS

APOE, DBP and AGT identified were associated with survival outcomes in mCRC patients treated with chemotherapy and bevacizumab.

Apolipoprotein E polymorphism and colorectal neoplasm: results from a meta-analysis

To investigate the relationship of Apolipoprotein E (APOE) gene polymorphism to colorectal neoplasia (CRN), we performed a systematic review and meta-analysis. Eligible studies were identified through a systematic literature review from PubMed, EMBASE, and the Science Citation Index up to February 2014. A combined analysis was performed, followed by a subgroup analyses stratified by the study design. We used data collected from 8 prospective studies involving respectively a total of 9243 participants and 4310 CRN cases which including 438 patients with colorectal adenoma (CRA), and 3873 patients with colorectal carcinoma (CRC). The pooled data from this meta-analysis indicated there was no significant association between APOE polymorphism and CRN (ε2: P = 0.51, OR 1.04 95% CI 0.93 to 1.16; ε4: P = 0.72, OR 0.98 95% CI 0.90 to 1.07). Interestingly, subgroup analysis demonstrated there was a significant decreased risk for proximal CRN in patients with APOE ε4 (P = 0.0007, OR 0.52 95% CI 0.35 to 0.76). Data showed no significant association between APOE genotype and overall CRN. However, compared with those carry APOE ε3 alleles, persons with APOE ε4 genotype have significant decreased risk suffering from proximal CRN but not from distal CRN.

Association between apolipoprotein E genotype and cancer susceptibility: a meta-analysis

BACKGROUND

Apolipoprotein E (ApoE), a protein primarily involved in lipoprotein metabolism, occurs in three isoforms (E2, E3 and E4). Studies evaluating the association between APOE genotype and incidence of malignancies have given inconclusive results.

OBJECTIVE

The objective of the present study was to analyze the association between APOE genotype and incidence of cancer by a meta-analysis.

METHODS

We conducted a literature search in the electronic databases for studies with information on APOE genotype in malignancies. Sixteen studies (14 case-control and 2 cohort; 77,970 controls and 12,010 cases) were included for the present meta-analysis. Pooled odds ratios (OR) with 95 % confidence intervals (CI) were calculated assuming a random-effect model for all the genotypes and alleles. Subgroup analyses based on study design, ethnicity of populations, site of cancer and source of controls were performed as a post hoc measure. Appropriate tests to detect heterogeneity, publication bias and sensitivity were done at all stages. The review protocol is registered with the PROSPERO database vide registration number CRD42013006496.

RESULTS

The pooled effect measure for the comparisons did not reveal an association in primary analyses. In the subgroup analyses, we observed a negative association between APOE4+ genotypes and overall risk of cancer in the cohort study subgroup (pooled OR 0.86; 95 % CI 0.82-0.91; p < 0.00001; I (2) = 0 %). Sensitivity analyses did not alter the overall pooled effect measure, and there were no evidences to suggest a publication bias.

CONCLUSION

Overall, the present meta-analysis did not show any association between APOE alleles and genotypes with incidence of cancer in general.

Prevalence of the apolipoprotein E Arg145Cys dyslipidemia at-risk polymorphism in African-derived populations

Apolipoprotein E, a protein component of blood lipid particles, plays an important role in lipid transport. Different mutations in the apolipoprotein E gene have been associated with various clinical phenotypes. In an initiated study of Qataris, we observed that 17% of the African-derived genetic subgroup were heterozygotes for a rare Arg145Cys (R145C) variant that functions as a dominant trait with incomplete penetrance associated with type III hyperlipoproteinemia. On the basis of this observation, we hypothesized that the R145C polymorphism might be common in African-derived populations. The prevalence of the R145C variant was assessed worldwide in the "1000 Genomes Project" and in 1,012 whites and 1,226 African-Americans in New York, New York. The 1000 Genomes Project data demonstrated that the R145C polymorphism is rare in non-African-derived populations but present in 5% to 12% of Sub-Saharan African-derived populations. The R145C polymorphism was also rare in New York whites (1 of 1,012, 0.1%); however, strikingly, 53 of the 1,226 New York African-Americans (4.3%) were R145C heterozygotes. The lipid profiles of the Qatari and New York R145C heterozygotes were compared with those of controls. The Qatari R145C subjects had higher triglyceride levels than the Qatari controls (p <0.007) and the New York African-American R145C subjects had an average of 52% greater fasting triglyceride levels than the New York African-American controls (p <0.002). From these observations, likely millions of people worldwide derived from Sub-Saharan Africans are apolipoprotein E R145C. In conclusion, although larger epidemiologic studies are necessary to determine the long-term consequences of this polymorphism, the available evidence suggests it is a common cause of a mild triglyceride dyslipidemia.

Plasma levels of apolipoprotein-E in residents of the European North of Russia

Background

Apolipoprotein-E (apoE) is one of the metabolically active apoproteins and plays an important role in lipid metabolism. However, there are no data on levels of apoE in residents of the North in spite of the fact that specific features of lipid metabolism in the northerners are described. The present work was designed to study plasma levels of apoE in residents of the European North of Russia.

Methods

A total of 937 native residents of the European North of Russia (463 men and 474 women) aged 13–60 years were included in the study. ApoE concentrations in the blood plasma were measured by immunoturbidimetric method.

Results

Plasma levels of apoE in residents of the European North of Russia were low. ApoE concentrations below the defined normal values were detected in 57.0% of the men and in 59.2% of the women. The mean plasma levels of apoE did not significantly differ in men and women (2.80 mg/dl vs 2.87 mg/dl). Plasma apoE concentrations in residents of the European North of Russia changed with age. Plasma levels of apoE decreased from 13 to 21 years in men and from 13 to 35 years in women and then increased in both sexes (p < 0.001).

Conclusion

The limits of variation of plasma apoE levels in residents of the European North of Russia shift towards lower values. Plasma levels of apoE below normal values were observed in approximately half of investigation subjects.

A case-control study on the effect of Apolipoprotein E genotypes on gastric cancer risk and progression

Background

Apolipoprotein E (ApoE) is a multifunctional protein playing both a key role in the metabolism of cholesterol and triglycerides, and in tissue repair and inflammation. The ApoE gene (19q13.2) has three major isoforms encoded by ε2, ε3 and ε4 alleles with the ε4 allele associated with hypercholesterolemia and the ε2 allele with the opposite effect. An inverse relationship between cholesterol levels and gastric cancer (GC) has been previously reported, although the relationship between apoE genotypes and GC has not been explored so far.

Methods

One hundred and fifty-six gastric cancer cases and 444 hospital controls were genotyped for apoE polymorphism (ε2, ε3, ε4 alleles). The relationship between GC and putative risk factors was measured using the adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) from logistic regression analysis. A gene-environment interaction analysis was performed. The effect of the apoE genotypes on survival from GC was explored by a Kaplan–Meier analysis and Cox proportional hazard regression model.

Results

Subjects carrying at least one apoE ε2 allele have a significant 60% decrease of GC risk (OR=0.40, 95% CI: 0.19 – 0.84) compared with ε3 homozygotes. No significant interaction emerged between the ε4 or ε2 allele and environmental exposures, nor ε2 or ε4 alleles affected the median survival times, even after correcting for age, gender and stadium.

Conclusions

Our study reports for the first time a protective effect of the ε2 allele against GC, that might be partly attributed to the higher antioxidant properties of ε2 compared with the ε3 or ε4 alleles. Given the study’s sample size, further studies are required to confirm our findings.

Targeted In Situ Gene Correction of Dysfunctional APOE Alleles to Produce Atheroprotective Plasma ApoE3 Protein

Cardiovascular disease is the leading worldwide cause of death. Apolipoprotein E (ApoE) is a 34-kDa circulating glycoprotein, secreted by the liver and macrophages with pleiotropic antiatherogenic functions and hence a candidate to treat hypercholesterolaemia and atherosclerosis. Here, we describe atheroprotective properties of ApoE, though also potential proatherogenic actions, and the prevalence of dysfunctional isoforms, outline conventional gene transfer strategies, and then focus on gene correction therapeutics that can repair defective APOE alleles. In particular, we discuss the possibility and potential benefit of applying in combination two technical advances to repair aberrant APOE genes: (i) an engineered endonuclease to introduce a double-strand break (DSB) in exon 4, which contains the common, but dysfunctional, ε2 and ε4 alleles; (ii) an efficient and selectable template for homologous recombination (HR) repair, namely, an adeno-associated viral (AAV) vector, which harbours wild-type APOE sequence. This technology is applicable ex vivo, for example to target haematopoietic or induced pluripotent stem cells, and also for in vivo hepatic gene targeting. It is to be hoped that such emerging technology will eventually translate to patient therapy to reduce CVD risk.

Apolipoprotein E mimetics and cholesterol-lowering properties

Apolipoprotein E (apoE) is a ligand for clearance of lipoprotein remnants such as chylomicrons and very low-density lipoproteins. It has anti-atherogenic and anti-inflammatory properties. Therefore, there is extensive ongoing research to create peptides that can mimic properties of apoE. A number of synthetic peptides that encompass different regions of apoE have been studied for inhibiting inflammatory states, including Alzheimer disease. However, peptides that clear atherogenic lipoproteins, analogous to apoE, via enhanced hepatic uptake have not been previously reviewed. Toward this end, we describe the design and studies of a dual-domain apoE mimetic peptide, Ac-hE18A-NH(2). This peptide consists of residues 141-150, the putative receptor-binding region of human apoE, covalently linked to a well characterized class A amphipathic helix, 18A, which has no sequence homology to any other exchangeable apolipoprotein sequences. It demonstrates dramatic effects in reducing plasma cholesterol levels in dyslipidemic mouse and rabbit models. We discuss the scientific rationale and review the literature for the design and efficacy of the peptide. Analogous to apoE, this peptide bypasses the low-density lipoprotein receptor for the hepatic uptake of atherogenic lipoproteins via heparan sulfate proteoglycan (HSPG). ApoE mimetics such as Ac-hE18A-NH(2) may therefore restore or replace ligands in genetically induced hyperlipidemias to enable reduction in atherogenic lipoproteins via HSPG even in the absence of functional low-density lipoprotein receptors. Therefore, this and similar peptides may be useful in the treatment of dyslipidemic disorders such as familial hyperlipidemia and atherosclerosis.

Dual action of apolipoprotein E-interacting HCCR-1 oncoprotein and its implication for breast cancer and obesity

Obese women have an increased risk for post-menopausal breast cancer. The physiological mechanism by which obesity contributes to breast tumourigenesis is not understood. We previously showed that HCCR-1 oncogene contributes to breast tumourigenesis as a negative regulator of p53 and detection of HCCR-1 serological level was useful for the diagnosis of breast cancer(.) In this study, we found that the HCCR-1 level is elevated in breast cancer tissues and cell lines compared to normal breast tissues. We identified apolipoprotein E (ApoE) interacting with HCCR-1. Our data show that HCCR-1 inhibits anti-proliferative effect of ApoE, which was mediated by diminishing ApoE secretion of breast cancer cells. Finally, HCCR-1 induced the severe obesity in transgenic mice. Those obese mice showed severe hyperlipidaemia. In conclusion, our results suggest that HCCR-1 might play a role in the breast tumourigenesis while the overexpression of HCCR-1 induces the obesity probably by inhibiting the cholesterol-lowering effect of ApoE. Therefore, HCCR-1 seems to provide the molecular link between the obesity and the breast cancer risk.

Dual action of apolipoprotein E-interacting HCCR-1 oncoprotein and its implication for breast cancer and obesity

Obese women have an increased risk for post-menopausal breast cancer. The physiological mechanism by which obesity contributes to breast tumourigenesis is not understood. We previously showed that HCCR-1 oncogene contributes to breast tumourigenesis as a negative regulator of p53 and detection of HCCR-1 serological level was useful for the diagnosis of breast cancer_. In this study, we found that the HCCR-1 level is elevated in breast cancer tissues and cell lines compared to normal breast tissues. We identified apolipoprotein E (ApoE) interacting with HCCR-1. Our data show that HCCR-1 inhibits anti-proliferative effect of ApoE, which was mediated by diminishing ApoE secretion of breast cancer cells. Finally, HCCR-1 induced the severe obesity in transgenic mice. Those obese mice showed severe hyperlipidaemia. In conclusion, our results suggest that HCCR-1 might play a role in the breast tumourigenesis while the overexpression of HCCR-1 induces the obesity probably by inhibiting the cholesterol-lowering effect of ApoE. Therefore, HCCR-1 seems to provide the molecular link between the obesity and the breast cancer risk.

Trade-off in the effects of the apolipoprotein E polymorphism on the ages at onset of CVD and cancer influences human lifespan

Progress in unraveling the genetic origins of healthy aging is tempered, in part, by a lack of replication of effects, which is often considered a signature of false-positive findings. We convincingly demonstrate that the lack of genetic effects on an aging-related trait can be because of trade-offs in the gene action. We focus on the well-studied apolipoprotein E (APOE) e2/3/4 polymorphism and on lifespan and ages at onset of cardiovascular diseases (CVD) and cancer, using data on 3924 participants of the Framingham Heart Study Offspring cohort. Kaplan-Meier estimates show that the e4 allele carriers live shorter lives than the non-e4 allele carriers (log rank = 0.016). The adverse effect was attributed to the poor survival of the e4 homozygotes, whereas the effect of the common e3/4 genotype was insignificant. The e3/4 genotype, however, was antagonistically associated with onsets of those diseases predisposing to an earlier onset of CVD and a later onset of cancer compared to the non-e4 allele genotypes. This trade-off explains the lack of a significant effect of the e3/4 genotype on survival; adjustment for it in the Cox regression model makes the detrimental effect of the e4 allele highly significant (P = 0.002). This trade-off is likely caused by the lipid-metabolism-related (for CVD) and nonrelated (for cancer) mechanisms. An evolutionary rationale suggests that genetic trade-offs should not be an exception in studies of aging-related traits. Deeper insights into biological mechanisms mediating gene action are critical for understanding the genetic regulation of a healthy lifespan and for personalizing medical care.

The Fat-Fed Apolipoprotein E Knockout Mouse Brachiocephalic Artery in the Study of Atherosclerotic Plaque Rupture

Atherosclerosis has been studied in animals for almost a century, yet the events leading up to the rupture of an atherosclerotic plaque (the underlying cause of the majority of fatal thrombosis formation) have only been studied in the past decade, due in part to the development of a mouse model of spontaneous plaque rupture. Apolipoprotein E knockout mice, when fed a high-fat diet, consistently develop lesions in the brachiocephalic artery that rupture at a known time point. It is therefore now possible to observe the development of lesions to elucidate the mechanisms behind the rupture of plaques. Critics argue that the model does not replicate the appearance of human atherosclerotic plaque ruptures. The purpose of this review is to highlight the reasons why we should be looking to the apolipoprotein E knockout mouse to further our understanding of plaque rupture.

High incidence of tumors in diabetic thrombin activatable fibrinolysis inhibitor and apolipoprotein E double-deficient mice

BACKGROUND

Activation of the complement system has been implicated in tumor growth. The antifibrinolytic protein, activated thrombin-activatable fibrinolysis inhibitor (TAFIa), can modulate the activation of the complement system by inactivating the anaphylatoxins C3a and C5a. The apolipoprotein-E (ApoE) genotype has been associated with carcinogenesis.

OBJECTIVE

The aim of this study was to evaluate whether TAFIa can affect the development of cancer in the ApoE-deficient mouse model.

METHODS

TAFI and ApoE double-knockout mice were generated. A group of mice was treated with the diabetogenic and carcinogenic compound streptozotocin (stz). Mice treated with saline, single knockout mice and wild-type (wt) mice served as controls.

RESULTS

Six months after treatment with stz, mice were sacrificed. Hepatic tumors were found in male double-knockout mice treated with stz but none was found in control animals that were not treated with stz or in single knockout of ApoE or wt animals. There was no significant difference in coagulation system activation between the groups of mice. The plasma concentrations of C5a, factor D and transforming growth factor-β1 were increased in TAFI/ApoE double-deficient mice treated with stz compared with the mice of the same genotype treated with saline.

CONCLUSION

Apo-E deficiency alone was not associated with tumors but the lack of TAFI appears to make the mice permissive for tumor formation in ApoE mice.

A case-control study on the effect of apoliprotein E genotype on head and neck cancer risk

BACKGROUND

The apolipoprotein E gene (apoE) has three major isoforms encoded by the ε2, ε3, and ε4 alleles, with the ε4 allele associated with hypercholesterolemia and the ε2 allele with the opposite effect. An inverse relationship between cholesterolemia and head and neck cancer (HNC) has been previously reported, although the relationship between apoE genotypes and HNC has not been explored to date.

METHODS

Four hundred and seventeen HNC cases and 436 hospital controls were genotyped for apoE polymorphisms. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) from logistic regression were used to explore the relationship between HNC and putative risk factors. A gene-environment interaction analysis was done.

RESULTS

A borderline significant 40% decreased HNC risk (OR, 0.58; 95% CI, 0.31-1.05) was observed for individuals carrying at least one ε2 allele. Females carrying at least one ε2 allele showed a 60% risk reduction (OR, 0.43; 95% CI, 0.21-0.90) for HNC compared with ε3 homozygotes. A statistically significant interaction was found between alcohol use and the ε4 allele (P for interaction = 0.04), with a 2-fold increased risk (OR, 2.06; 95% CI, 0.95-4.48) among ever drinkers with an ε4 allele, with respect to ε3 homozygote nondrinkers.

CONCLUSIONS

Our study provides novel evidence of a possible protective effect of the ε2 allele against HNC, probably due to its increased antioxidant properties.

IMPACT

According to our results, apolipoprotein E may play a different role in carcinogenesis other than its well-known role in regulating blood serum cholesterol levels.

Association of apolipoprotein E and angiotensin converting enzyme gene polymorphisms with the multidimensional impairment in older patients

The role of the apolipoprotein E (APOE) and the angiotensin converting enzyme (ACE) polymorphisms on health and functional status deterioration in old age is still undefined. Recently, a Multidimensional Prognostic Index (MPI) for 1-year mortality derived from a Comprehensive Geriatric Assessment (CGA) was developed and validated in hospitalized elderly patients. The aim of this study was to investigate the possible association of the APOE and ACE gene polymorphisms with the multidimensional impairment, as evaluated by the MPI, in older patients. These polymorphisms were assessed in 1894 geriatric inpatients divided into three groups according to their MPI values: MPI-1 low risk (n = 988), MPI-2 moderate risk (n = 671), and MPI-3 severe risk of mortality (n = 235). A slight deviation from Hardy-Weinberg equilibrium was observed for the APOE genotypes. With the increasing of the MPI grade, a significant increase in the frequencies of epsilon4 allele and the ACE D/D genotype was observed. The APOE epsilon4(+) and ACE D/D genotypes were associated with severe MPI grade (APOE epsilon4(+), odds ration [OR] = 1.79, 95% confidence interval [CI] 1.20-2.67; ACE D/D, OR = 1.42, 95% CI 1.05-1.92). The combined APOE epsilon4(+) and ACE D/D genetic status was associated with higher MPI grade (OR = 2.85, 95% CI 1.75-4.65), without interaction. No significant associations between APOE and ACE polymorphisms and 2-year mortality were found. APOE and ACE genes might predispose individuals to health and functional status deterioration in old age, and their effect is additive.

Association of apolipoprotein E polymorphisms and dietary factors in colorectal cancer

ApoE single nucleotide polymorphisms (SNPs) Cys112Arg (Epsilon-4), and Arg158Cys (Epsilon-2) have been implicated in cardiovascular and Alzheimer's disease, but their role in colorectal cancer (CRC) has not been extensively studied. We investigated whether ApoE polymorphisms alone or in combination with dietary factors selectively contribute to mismatch-repair (MMR) proficient (microsatellite stable/low or MSS/L) vs deficient (microsatellite unstable or MSI-H) CRCs. We carried out a case–control study with 906 CRC cases and 911 unaffected controls to examine the associations between ApoE polymorphisms and dietary factors and assessed their contribution to MSS/L and MSI-H CRCs. We used unconditional logistic regression to evaluate the associations between ApoE SNPs, tumour MSI status, and dietary factors after adjusting for age and sex. All statistical tests were two-sided. No significant differences in ApoE genotype frequencies were observed between CRC cases and unaffected controls. We observed that increased dietary intake of total fat, saturated fat, cholesterol, and red meat was significantly associated with CRC. Among non-ApoE4 carriers, 2–4 and >4 red meat servings/week were associated with developing MSS/L CRC (OR=1.51, 95% CI 1.10–2.07 and OR=1.80, 95% CI 1.30–2.48, respectively), whereas among ApoE4 allele carriers, four or more red meat servings/week were associated with MSI-H CRC (OR=4.62, 95% CI 1.20–17.77) when compared with the controls. ApoE isoforms modulate the risk of MSI-H and MSS/L CRCs among high red meat consumers.

Dendritic cell differentiation induced by a self-peptide derived from apolipoprotein E

Dendritic cells (DCs) are professional APCs and potent stimulators of naive T cells. Since DCs have the ability to immunize or tolerize T cells they are unique candidates for use in immunotherapy. Our laboratory has discovered that a naturally processed self-peptide from apolipoprotein E, Ep1.B, induces DC-like morphology and surface marker expression in a murine monocytic cell line (PU5-1.8), human monocytic cell line (U937), murine splenocytes, and human peripheral blood monocytes. Microscopy and flow cytometric analysis revealed that Ep1.B-treated cells display decreased adherence to plastic and increased aggregation, dendritic processes, and expression of DC surface markers, including DEC-205, CD11c, B7.1, and B7.2. These effects were observed in both PU5-1.8 cells and splenocytes from various mouse strains including BALB/c, C57BL/6, NOD/Lt, and C3H/HeJ. Coadministration of Ep1.B with OVA antigenic peptide functions in dampening specific immune response to OVA. Ep1.B down-regulates proliferation of T cells and IFN-gamma production and stimulates IL-10 secretion in immunized mice. Ep1.B-induced differentiation resulted in the activation of PI3K and MAPK signaling pathways, including ERK1/2, p38, and JNK. We also found that NF-kappaB, a transcription factor essential for DC differentiation, is critical in mediating the effects of Ep1.B. Ep1.B-induced differentiation is independent of MyD88-dependent pathway of TLR signaling. Cumulatively, these findings suggest that Ep1.B acts by initiating a signal transduction cascade in monocytes leading to their differentiation into DCs.

Cleavage and functional loss of human apolipoprotein E by digestion of matrix metalloproteinase-14

By means of a degradomic approach applying proteomic techniques, we previously suggested that apolipoprotein E (apoE) is a substrate of matrix metalloproteinase-14 (MMP-14). Here we confirm that apoE is, in fact, a substrate of MMP-14 and also of MMP-7 and MMP-2 to a lesser extent. The 34 kDa apoE protein was initially processed by MMP-14 into fragments with molecular masses of 28, 23, 21, and 11 kDa. MMP-14 cleavage sites within the apoE protein were determined by C-terminal labeling of MMP-14-digested apoE fragments with isotope ((18)O/(16)O = 1:1) and identification of the doublet fragments or peptides showing 2 Da difference by MS, along with N-terminal sequencing of the fragments. It was determined that the primary MMP-14 cleavage sites were A(176)-I(177), P(183)-L(184), P(202)-L(203), and Q(249)-I(250). The MMP-14-mediated cleavage of apoE was consistent regardless of whether apoE existed in its lipid-bound or lipid-free form. Upon digestion with MMP-14, apoE loses its ability to suppress the platelet-derived growth factor-induced migration of rat vascular smooth muscle cells. Considering the important role of apoE for lipid metabolism and atherosclerosis protection, our findings suggest that MMP-14 plays an essential role for the development of hyperlipidemia and atherosclerosis as a result of degradation of apoE.

Polymorphisms of genes in the lipid metabolism pathway and risk of biliary tract cancers and stones: a population-based case-control study in Shanghai, China

Biliary tract cancers, encompassing the gallbladder, extrahepatic bile duct, and ampulla of Vater, are uncommon yet highly fatal malignancies. Gallstones, the primary risk factor for biliary cancers, are linked with hyperlipidemia. We examined the associations of 12 single nucleotide polymorphisms of five genes in the lipid metabolism pathway with the risks of biliary cancers and stones in a population-based case-control study in Shanghai, China. We included 235 gallbladder, 125 extrahepatic bile duct, and 46 ampulla of Vater cancer cases, 880 biliary stone cases, and 779 population controls. Subjects completed an in-person interview and gave blood. Genotyping was conducted by TaqMan assay using DNA from buffy coats. The effects of APOE IVS1+69 (rs440446) and APOB IVS6+360C>T (rs520354) markers were limited to men. Men carrying the G allele of APOE IVS1+69 had a 1.7-fold risk of stones [95% confidence interval (95% CI), 1.2-2.4], a 1.8-fold risk of gallbladder cancer (95% CI, 1.0-3.3), a 3.7-fold risk of bile duct cancer (95% CI, 2.0-7.0), and a 4-fold risk of ampullary cancer (95% CI, 1.4-12.4). Male carriers of the T allele of APOB IVS6+360C>T had a 2-fold risk of bile duct cancer (95% CI, 1.2-3.4). The APOB T-T haplotype (APOB IVS6+360C>T, EX4+56C>T) was associated with a 1.6-fold risk of bile duct cancer (95% CI, 1.1-2.3). Male and female carriers of the T allele of LDLR IVS9-30C>T (rs1003723) had a 1.5-fold risk of bile duct cancer. Our findings suggest that gene variants in the lipid metabolism pathway contribute to the risk of biliary tract stones and cancers, particularly of the bile duct.

Oncoproteomics of hepatocellular carcinoma: from cancer markers' discovery to functional pathways

Hepatocellular carcinoma (HCC) is a heterogeneous cancer with no promising treatment and remains one of the most prevailing and lethal malignancies in the world. Researchers in many biological areas now routinely identify and characterize protein markers by a mass spectrometry-based proteomic approach, a method that has been commonly used to discover diagnostic biomarkers for cancer detection. The proteomic research platforms span from the classical two-dimensional polyacrylamide gel electrophoresis (2-DE) to the latest Protein Chip or array technology, which are often integrated with the MALDI (matrix-assisted laser-desorption ionization), SELDI (surface-enhanced laser desorption/ionization) or tandem mass spectrometry (MS/MS). New advances on quantitative proteomic analysis (e.g. SILAC, ICAT, and ITRAQ) and multidimensional protein identification technology (MudPIT) have greatly enhanced the capability of proteomic methods to study the expressions, modifications and functions of protein markers. The present article reviews the latest proteomic development and discovery of biomarkers in HCC that may provide insights into the underlying mechanisms of hepatocarcinogenesis and the readiness of biomarkers for clinical uses.

Impaired secretion of apolipoprotein E2 from macrophages

Human apoE is a multifunctional and polymorphic protein synthesized and secreted by liver, brain, and tissue macrophages. Here we show that apoE isoforms and mutants expressed through lentiviral transduction display cell-specific differences in secretion efficiency. Whereas apoE3, apoE4, and a natural mutant of apoE4 (apoE-Cys(142)) were efficiently secreted from macrophages, apoE2 and a non-natural apoE mutant (apoE-Cys(112)/Cys(142)) were retained in the perinuclear region and only minimally secreted. The secretory block for apoE2 in macrophages was not affected by the ablation of LDLR (low density lipoprotein receptor), ABCA-1, or SR-BI (scavenger receptor class B type I) but was released in the absence of low density lipoprotein receptor related protein (LRP). In co-immunoprecipitation experiments, an anti-apoE antibody pulled down two times more LRP in apoE2-transduced macrophages than in apoE3-expressing macrophages. Non-reducing SDS-PAGE/Western blot analyses showed that macrophage apoE2 is mostly dimeric and multimeric, whereas apoE3 is predominantly monomeric. ApoE2 retention and multimer formation also occurred in human macrophages derived from the monocyte cell line THP-1. These results were specific for macrophages, as in transduced mouse primary hepatocytes: 1) ApoE2 was secreted as efficiently as apoE3 and apoE4; 2) all isoforms were exclusively in monomeric form; 3) there was no co-immunoprecipitation of apoE and LRP. A microsomal triglyceride transfer protein (MTP) inhibitor nearly deleted apoB100 secretion from hepatocytes without affecting apoE secretion. These data show that macrophages retain apoE2, a highly expressed protein carried by about 8% of the human population. Given the role of locally produced apoE in regulating cholesterol efflux, modulating inflammation, and controlling oxidative stress, this unique property of apoE2 may have important impacts on atherogenesis.

Factor V Leiden and apolipoprotein E genotypes in severe femoropopliteal atherosclerosis with restenosis

BACKGROUND

The role of factor V (Leiden) mutation, thrombophilia, and apolipoprotein E (apoE) alleles in the pathogenesis of accelerated atherosclerosis and restenosis was studied in patients requiring reoperation within five years after femoropopliteal angioplasty with artificial grafts.

METHODS

One hundred ninety-eight consecutive patients with femoropopliteal atherosclerotic disease, reoperated for restenosis were contacted by phone and 100 of them returned for laboratory and clinical work-up. In addition to clinical evaluation and routine laboratory investigations, parameters of lipoprotein metabolism, factor V (Leiden) mutation and apolipoprotein E (apoE) allele were studied by PCR amplification of DNA and endonuclease digestion techniques.

RESULTS

A significantly higher incidence of factor V (Leiden) mutation was found in patients with atherosclerosis and restenosis, compared to 445 healthy blood donors (13/200, 6.5% vs. 34/890, 3.8%, p=0.0379). Distribution of the alleles of the apolipoprotein E (apoE) gene was different, when the patients were compared to 372 controls; however, the difference only approached the level of statistical significance (25/200, 12.5% vs. 56/744, 7.5%, p=0.0515). Comparing the two groups, the number of epsilon4 allele carriers was significantly higher among patients with restenosis (25/100, 25% vs. 53/272, 14%, p=0.0147).

CONCLUSION

Factor V (Leiden) mutation may influence the progression of atherosclerosis and the development of restenosis after revascularization in patients with accelerated femoropopliteal atherosclerosis. Further investigation is needed whether long-term anticoagulation has an impact or not on the course of disease in such cases. ApoE epsilon4 allele should be screened in patients with femoropopliteal atherosclerosis, because it indicates a faster progression of atherosclerosis and may predict restenosis after revascularization procedure.

Gene-gene, gene-environment & multiple interactions in colorectal cancer

This review comprehensively evaluates the influence of gene-gene, gene-environment and multiple interactions on the risk of colorectal cancer (CRC). Methods of studying these interactions and their limitations have been discussed herein. There is a need to develop biomarkers of exposure and of risk that are sensitive, specific, present in the pathway of the disease, and that have been clinically tested for routine use. The influence of inherited variation (polymorphism) in several genes has been discussed in this review; however, due to study limitations and confounders, it is difficult to conclude which ones are associated with the highest risk (either individually or in combination with environmental factors) to CRC. The majority of the sporadic cancer is believed to be due to modification of mutation risk by other genetic and/or environmental factors. Micronutrient deficiency may explain the association between low consumption of fruit/vegetables and CRC in human studies. Mitochondrial modulation by dietary factors influences the balance between cell renewal and death critical in colon mucosal homeostasis. Both genetic and epigenetic interactions are intricately dependent on each other, and collectively influence the process of colorectal tumorigenesis. The genetic and environmental interactions present a good prospect and a challenge for prevention strategies for CRC because they support the view that this highly prevalent cancer is preventable.

Proteomic analysis of differentially expressed proteins in hepatocellular carcinoma developed in patients with chronic viral hepatitis C

Hepatocellular carcinoma (HCC) is a major complication of chronic viral hepatitis C. Therapy for HCC is still disappointing. It is thus of great importance to identify novel HCC markers for early detection of the disease, and tumor-specific proteins as potential therapeutic targets. We have used a proteomic approach to identify new proteins involved in HCC development. Four cases of HCC developing from chronic viral hepatitis C were analyzed by two-dimensional electrophoresis (2-DE), and results were compared to those of paired adjacent non-tumorous liver tissues. For MS fingerprinting, protein spots with differential intensity between HCC and non-tumorous liver were directly cut out of gels and processed for MALDI-MS and nano-LC-ESI-MS/MS analysis. Approximately 850 spots were visualized in each gel. The comparative analysis of paired samples indicated that 345 protein spots showed significant differences in expression level between non-tumor and tumor tissue. Among the 345 protein spots analyzed, 238 spots corresponding to 155 different proteins were identified; 49 proteins were up-regulated, whereas 106 proteins were down-regulated. Among these 155 proteins, 91 proteins were regulated in at least three cases. Although 52 out of these 91 proteins have been already described by previous proteomic or transcriptomic studies, or are already known to be involved in hepatocarcinogenesis, this experiment revealed 39 new proteins differentially expressed in HCC developing from viral hepatitis C. Variations in protein accumulation were confirmed for two selected proteins (apolipoprotein E, chloride intracellular channel 1) by Western blotting in ten additional cases of HCC developing in patients with viral hepatitis C.

An interaction between apolipoprotein E and TERE1 with a possible association with bladder tumor formation

TERE1, a recently discovered gene/protein appears to play a role in bladder tumor growth regulation but to date does not have clear functional correlates. The objective of this study was to gain further insight into the function of the TERE1 protein by identifying potential protein to protein interactions with TERE1 and determining whether these interactions are associated with putative growth regulatory pathways and/or bladder tumor formation. Towards this aim, we have performed a bacterial two hybrid assay and isolated interacting clones, which then were sequenced and further examined by affinity chromatography and immunoprecipitation. From among several positive clones, we isolated a putative interacting plasmid containing the C-terminal portion of preapolipoprotein E starting from amino acid number 124 from the pBT-TERE1/pTarget-cDNA bacterial two hybrid system. The C-terminal portion of apoE interaction with the TERE1 was confirmed using ProBond columns by the expression of 6XHis recombinant and (35)S methionine/cysteine labeled proteins. We found that there was ubiquitous expression of the apoE transcript in normal bladder and in various grades and stages of transitional cell carcinoma (TCC) of the bladder. Likewise, we detected the apoE protein in both normal and malignant bladder tissues by Western blot. There was a significant decrease in the apoE protein in 12 of 16 muscle invasive TCCs of the bladder compared to normal bladder mucosa samples. Previous studies in rat fibroblasts have found that expression of apoE can decrease the phosphorylation of the growth factor-related p42/44 MAP kinase. A significant decrease in p44/p42 MAPK phophorylation was also apparent using a phosphorylation specific antibody in human 293 kidney cells upon transfection and expression of apoE. In conclusion, the results from this study suggest that the expression and regulation of the apoE pathway may yield clues toward understanding the function of TERE1.