Genetic variation in 3-hydroxy-3-methylglutaryl CoA reductase modifies the chemopreventive activity of statins for colorectal cancer

Colorectal Cancer Chemoprevention: A Dream Coming True?

Colorectal cancer (CRC) is one of the deadliest forms of cancer worldwide. CRC development occurs mainly through the adenoma-carcinoma sequence, which can last decades, giving the opportunity for primary prevention and early detection. CRC prevention involves different approaches, ranging from fecal occult blood testing and colonoscopy screening to chemoprevention. In this review, we discuss the main findings gathered in the field of CRC chemoprevention, focusing on different target populations and on various precancerous lesions that can be used as efficacy evaluation endpoints for chemoprevention. The ideal chemopreventive agent should be well tolerated and easy to administer, with low side effects. Moreover, it should be readily available at a low cost. These properties are crucial because these compounds are meant to be used for a long time in populations with different CRC risk profiles. Several agents have been investigated so far, some of which are currently used in clinical practice. However, further investigation is needed to devise a comprehensive and effective chemoprevention strategy for CRC.

Pathogenic role of 25-hydroxycholesterol in cancer development and progression

Cholesterol is an essential lipid that serves several important functions, including maintaining the homeostasis of cells, acting as a precursor to bile acid and steroid hormones and preserving the stability of membrane lipid rafts. 25-hydroxycholesterol (25-HC) is a cholesterol derivative that may be formed from cholesterol. 25-HC is a crucial component in various biological activities, including cholesterol metabolism. In recent years, growing evidence has shown that 25-HC performs a critical function in the etiology of cancer, infectious diseases and autoimmune disorders. This review will summarize the latest findings regarding 25-HC, including its biogenesis, immunomodulatory properties and role in innate/adaptive immunity, inflammation and the development of various types of cancer.

Statin as a therapeutic agent in gastroenterological cancer

Statins inhibit 3-hydroxy-3-methylglutaryl-CoA reductase, the rate-limiting enzyme of the mevalonate pathway, and are widely used as an effective and safe approach handle hypercholesterolemia. The mevalonate pathway is a vital metabolic pathway that uses acetyl-CoA to generate isoprenoids and sterols that are crucial to tumor growth and progression. Multiple studies have indicated that statins improve patient prognosis in various carcinomas. Basic research on the mechanisms underlying the antitumor effects of statins is underway. The development of new anti-cancer drugs is progressing, but increasing medical costs from drug development have become a major obstacle. Readily available, inexpensive and well-tolerated drugs like statins have not yet been successfully repurposed for cancer treatment. Identifying the cancer patients that may benefit from statins is key to improved patient treatment. This review summarizes recent advances in statin research in cancer and suggests important considerations for the clinical use of statins to improve outcomes for cancer patients.

Computer-Aided Design for Identifying Anticancer Targets in Genome-Scale Metabolic Models of Colon Cancer

Simple Summary

Discovery of anticancer targets with minimal side effects is a major challenge in drug discovery and development. This study developed a fuzzy optimization framework for identifying anticancer targets. The framework was applied to identify not only gene regulator targets but also metabolite- and reaction-centric targets. The computational results show that the combination of a carbon metabolism target and any one-target gene that participates in the sphingolipid, glycerophospholipid, nucleotide, cholesterol biosynthesis, or pentose phosphate pathways is more effective for treatment than one-target inhibition is, and a two-target combination of 5-FU and folate supplement can improve cell viability, reduce metabolic deviation, and reduce side effects of normal cells.

Abstract

The efficient discovery of anticancer targets with minimal side effects is a major challenge in drug discovery and development. Early prediction of side effects is key for reducing development costs, increasing drug efficacy, and increasing drug safety. This study developed a fuzzy optimization framework for Identifying AntiCancer Targets (IACT) using constraint-based models. Four objectives were established to evaluate the mortality of treated cancer cells and to minimize side effects causing toxicity-induced tumorigenesis on normal cells and smaller metabolic perturbations. Fuzzy set theory was applied to evaluate potential side effects and investigate the magnitude of metabolic deviations in perturbed cells compared with their normal counterparts. The framework was applied to identify not only gene regulator targets but also metabolite- and reaction-centric targets. A nested hybrid differential evolution algorithm with a hierarchical fitness function was applied to solve multilevel IACT problems. The results show that the combination of a carbon metabolism target and any one-target gene that participates in the sphingolipid, glycerophospholipid, nucleotide, cholesterol biosynthesis, or pentose phosphate pathways is more effective for treatment than one-target inhibition is. A clinical antimetabolite drug 5-fluorouracil (5-FU) has been used to inhibit synthesis of deoxythymidine-5′-triphosphate for treatment of colorectal cancer. The computational results reveal that a two-target combination of 5-FU and a folate supplement can improve cell viability, reduce metabolic deviation, and reduce side effects of normal cells.

The Heterogeneity of Lipid Metabolism in Cancer

The study of cancer cell metabolism has traditionally focused on glycolysis and glutaminolysis. However, lipidomic technologies have matured considerably over the last decade and broadened our understanding of how lipid metabolism is relevant to cancer biology [1-3]. Studies now suggest that the reprogramming of cellular lipid metabolism contributes directly to malignant transformation and progression [4, 5]. For example, de novo lipid synthesis can supply proliferating tumor cells with phospholipid components that comprise the plasma and organelle membranes of new daughter cells [6, 7]. Moreover, the upregulation of mitochondrial β-oxidation can support tumor cell energetics and redox homeostasis [8], while lipid-derived messengers can regulate major signaling pathways or coordinate immunosuppressive mechanisms [9-11]. Lipid metabolism has, therefore, become implicated in a variety of oncogenic processes, including metastatic colonization, drug resistance, and cell differentiation [10, 12-16]. However, whether we can safely and effectively modulate the underlying mechanisms of lipid metabolism for cancer therapy is still an open question.

The Association Between Statin Use and Outcomes in Patients Initiating Androgen Deprivation Therapy

BACKGROUND

Studies have conflicting results regarding the association between statin use and biochemical recurrence for prostate cancer (PCa). A limited number of studies examining statins in advanced stages report positive results, with a few specifically examining statins and androgen deprivation therapy (ADT).

OBJECTIVE

To perform a post hoc secondary analysis of a randomised controlled trial (RCT) of men initiating ADT to examine the association between statin use and outcomes.

DESIGN, SETTING, AND PARTICIPANTS

Patients with prostate-specific antigen (PSA) >3 ng/ml >1 yr following primary/salvage radiotherapy were enrolled in an RCT of intermittent androgen deprivation (IAD) versus continuous ADT (NCT00003653). Baseline and on-study statin use was modelled as a time-dependent covariate.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was overall survival. Models were adjusted for age, time from radiotherapy to ADT, baseline PSA, and prior ADT.

RESULTS AND LIMITATIONS

Of 1364 patients, statin users (585; 43%) were younger (72.7 vs 73.8 yr, p = 0.001) and less likely to have PSA >15 ng/ml (20% vs 25%, p = 0.04). After a median follow-up of 6.9 yr, statin use was associated with reduced overall (hazard ratio [HR]: 0.64; 95% confidence interval [CI] 0.53-0.78, p < 0.001) and PCa-specific (HR: 0.65, 95% CI 0.48-0.87, p = 0.004) mortality. Statin users had 13% longer time to castration resistance, but this did not reach statistical significance (p = 0.15). As an exploratory endpoint, in the IAD arm, statin users had longer time off treatment (median: 0.85 vs 0.64 yr, p = 0.06). Limitations include potential for residual confounding between statin users and nonusers, and confounding by indication.

CONCLUSIONS

In men treated with ADT following primary or salvage radiotherapy, statin use was associated with improved overall and PCa-specific survival. In patients treated with IAD, statin use was associated with a trend towards longer time off treatment. A prospective trial of statins in men commencing ADT is warranted.

PATIENT SUMMARY

We found a favourable association between statin use and survival outcomes in patients initiating androgen deprivation therapy.

Molecular Targets in Precision Chemoprevention of Colorectal Cancer: An Update from Pre-Clinical to Clinical Trials

Colorectal cancer (CRC) is one of the leading causes of cancer deaths worldwide. The initiation and progression of CRC is a multi-step process that proceeds via precursor lesions to carcinoma, with each stage characterized by its distinct molecular and tissue microenvironment changes. Precursor lesions of CRC, aberrant crypt foci, and adenoma exhibit drastic changes in genetic, transcriptomic, and proteomic profiles compared to normal tissue. The identification of these changes is essential and provides further validation as an initiator or promoter of CRC and, more so, as lesion-specific druggable molecular targets for the precision chemoprevention of CRC. Mutated/dysregulated signaling (adenomatous polyposis coli, β-catenin, epidermal growth factor receptor, V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS), tumor protein53, Akt, etc.), inflammatory (cyclooxygenase-2, microsomal prostaglandin E synthase-1, inducible nitric oxide synthase, and other pro-inflammatory mediators), and metabolic/growth factor (fatty acid synthase, β-Hydroxy β-methylglutaryl-CoA reductase, and ornithine decarboxylase) related targets are some of the well-characterized molecular targets in the precision chemoprevention of CRC. In this review, we discuss precursor-lesion specific targets of CRC and the current status of pre-clinical studies regarding clinical interventions and combinations for better efficacy and safety toward future precision clinical chemoprevention. In addition, we provide a brief discussion on the usefulness of secondary precision chemopreventive targets for tertiary precision chemoprevention to improve the disease-free and overall survival of advanced stage CRC patients.

Chemoprevention of Colorectal Cancer

Although colorectal cancer (CRC) screening has reduced the incidence of and mortality from CRC, chemoprevention strategies have the potential to further reduce CRC incidence and mortality. Chemoprevention agents might be used for average-risk as well as high-risk groups, and to prevent CRC recurrence after therapy. CRC chemoprevention agents that have been studied include aspirin, nonaspirin nonsteroidal anti-inflammatory drugs, statins, agents that target metabolic pathways, and vitamins and minerals. We review the prospect of chemoprevention of CRC, results from preclinical and human studies, challenges, and future directions.

Statins reduce the progression of non-advanced adenomas to colorectal cancer: a postcolonoscopy study in 187 897 patients

BACKGROUND AND AIMS

Postcolonoscopy colorectal cancer (PCCRC) accounts for up to 9% of all CRCs. Statins have been shown to be associated with a lower CRC risk. We aimed to investigate whether PCCRC risk was also lower among statin users.

METHODS

This is a retrospective cohort study using a territory-wide electronic healthcare database in Hong Kong including patients aged 40 years or above who had undergone colonoscopies between 2005 and 2013. Exclusion criteria included prior colorectal cancer (CRC), inflammatory bowel disease, prior colectomy and CRC detected within 6 months of index colonoscopy. We defined statin use as at least 90-day use before index colonoscopy. Medication use was traced up to 5 years before index colonoscopy. PCCRC-3y was defined as cancer diagnosed between 6 and 36 months after index colonoscopy. Sites of CRC were categorised as proximal (proximal to splenic flexure) and distal cancer. The subdistribution HR (SHR) of PCCRC-3y with statin use was derived by propensity score matching based on covariates (including patient factors, concurrent medication use and endoscopy centre's performance).

RESULTS

Of 187 897 eligible subjects, 854 (0.45%) were diagnosed with PCCRC-3y. Statin use was associated with a lower PCCRC-3y risk (SHR: 0.72; 95% CI 0.55 to 0.95; p=0.018). Subgroup analysis shows that SHRs were 0.50 (95% CI 0.28 to 0.91; p=0.022) for proximal and 0.80 (95% CI 0.59 to 1.09; p=0.160) for distal cancer. Older (>60 years) patients, women and those without diabetes mellitus or polyps appeared to benefit more from statins.

CONCLUSIONS

Statins were associated with a lower PCCRC risk, particularly for proximal cancer.

Fluvastatin Inhibits HMG-CoA Reductase and Prevents Non-Small Cell Lung Carcinogenesis

Lung cancer is the leading cause of cancer-related death worldwide. However, promising agents for lung cancer prevention are still very limited. Identification of preventive targets and novel effective preventive agents is urgently needed for clinical applications. In this study, we found that fluvastatin targeted 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (HMGCR), which a rate-limiting enzyme in the mevalonate pathway, and inhibited non-small cell lung cancer (NSCLC) tumorigenesis. Initially, we demonstrated that HMGCR is overexpressed in human lung adenocarcinoma tissues compared with normal tissues. Knockdown of HMGCR in NSCLC cells attenuated growth and induced apoptosis in vitro and in vivo Furthermore, we found that fluvastatin, an inhibitor of HMGCR, suppressed NSCLC cell growth and induced apoptosis. Intriguingly, fluvastastin functions by inhibiting the HMGCR-driven Braf/MEK/ERK1/2 and Akt signaling pathways. Notably, fluvastatin attenuated tumor growth in 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis and in a patient-derived xenograft lung tumor model. Overall, our findings suggest that fluvastatin might be promising chemopreventive or potential therapeutic drug against NSCLC tumorigenesis, providing hope for rapid clinical translation.

Mendelian randomization analysis rules out disylipidaemia as colorectal cancer cause

Dyslipidemia and statin use have been associated with colorectal cancer (CRC), but prospective studies have shown mixed results. We aimed to determine whether dyslipidemia is causally linked to CRC risk using a Mendelian randomization approach and to explore the association of statins with CRC. A case-control study was performed including 1336 CRC cases and 2744 controls (MCC-Spain). Subjects were administered an epidemiological questionnaire and were genotyped with an array which included polymorphisms associated with blood lipids levels, selected to avoid pleiotropy. Four genetic lipid scores specific for triglycerides (TG), high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), or total cholesterol (TC) were created as the count of risk alleles. The genetic lipid scores were not associated with CRC. The ORs per 10 risk alleles, were for TG 0.91 (95%CI: 0.72-1.16, p = 0.44), for HDL 1.14 (95%CI: 0.95-1.37, p = 0.16), for LDL 0.97 (95%CI: 0.81-1.16, p = 0.73), and for TC 0.98 (95%CI: 0.84-1.17, p = 0.88). The LDL and TC genetic risk scores were associated with statin use, but not the HDL or TG. Statin use, overall, was a non-significant protective factor for CRC (OR 0.84; 95%CI: 0.70-1.01, p = 0.060), but lipophilic statins were associated with a CRC risk reduction (OR 0.78; 95%CI 0.66-0.96, p = 0.018). Using the Mendelian randomization approach, our study does not support the hypothesis that lipid levels are associated with the risk of CRC. This study does not rule out, however, a possible protective effect of statins in CRC by a mechanism unrelated to lipid levels.

Pharmacogenetics of statins treatment: Efficacy and safety

WHAT IS KNOWN AND OBJECTIVE

Statins are widely used worldwide in the prevention and treatment of coronary atherosclerotic heart disease and ischaemic stroke. However, in clinical application, statins have shown great individual differences in terms of the efficacy and safety, some of which are related to genetic factors. The purpose of this article was to summarize the recent advances about the correlation between gene polymorphisms and the efficacy/safety of statins.

METHODS

We searched the databases including PharmGKB and PubMed (published before June 2019) using the keywords such as 'statin', 'gene polymorphism' and 'SNP' and obtained more than 100 articles. In this review, we described the clinical studies of genetic variants associated with both the efficacy and adverse reactions of statins. We also clarified the importance of taking pharmacogenetic variation into account to improve the clinical application of statins.

RESULTS AND DISCUSSION

The available data were collected and analysed to present the polymorphisms of candidate genes encoding the most promising proteins including SLCO1B1 (encoding uptake transporters); ABCB1, ABCC2, ABCG2 (encoding effluent transporter); APOE, APOA5 (encoding apolipoprotein); genes encoding cytochrome P450 enzyme system; KIF6, HMGCR, LDLR, LPA, PCSK9, COQ2, CETP, etc These genes were proved to be related to the pharmacodynamics and pharmacokinetics of statins, thus affecting the efficacy and safety.

WHAT IS NEW AND CONCLUSION

In this paper, the correlation between gene polymorphisms and the efficacy/safety of statins was summarized. The authors reached a consensus that the variants of the genes encoding uptake and effluent transporters have the most effect on the efficacy/safety of statins. It pointed out that it is desirable to do genetic testing of these transporter genes to reduce the incidence of myopathy or to achieve better outcomes before patients use statins, especially in the regions with high frequency of risk allele.

Oxysterols and Gastrointestinal Cancers Around the Clock

This review focuses on the role of oxidized sterols in three major gastrointestinal cancers (hepatocellular carcinoma, pancreatic, and colon cancer) and how the circadian clock affects the carcinogenesis by regulating the lipid metabolism and beyond. While each field of research (cancer, oxysterols, and circadian clock) is well-studied within their specialty, little is known about the intertwining mechanisms and how these influence the disease etiology in each cancer type. Oxysterols are involved in pathology of these cancers, but final conclusions about their protective or damaging effects are elusive, since the effect depends on the type of oxysterol, concentration, and the cell type. Oxysterol concentrations, the expression of key regulators liver X receptors (LXR), farnesoid X receptor (FXR), and oxysterol-binding proteins (OSBP) family are modulated in tumors and plasma of cancer patients, exposing these proteins and selected oxysterols as new potential biomarkers and drug targets. Evidence about how cholesterol/oxysterol pathways are intertwined with circadian clock is building. Identified key contact points are different forms of retinoic acid receptor related orphan receptors (ROR) and LXRs. RORs and LXRs are both regulated by sterols/oxysterols and the circadian clock and in return also regulate the same pathways, representing a complex interplay between sterol metabolism and the clock. With this in mind, in addition to classical therapies to modulate cholesterol in gastrointestinal cancers, such as the statin therapy, the time is ripe also for therapies where time and duration of the drug application is taken as an important factor for successful therapies. The final goal is the personalized approach with chronotherapy for disease management and treatment in order to increase the positive drug effects.

The effect of genetic variants on the relationship between statins and breast cancer in postmenopausal women in the Women's Health Initiative observational study

PURPOSE

Statins have been postulated to have chemopreventive activity against breast cancer. We evaluated whether germline genetic polymorphisms modified the relationship between statins and breast cancer risk using data from the Women's Health Initiative. We evaluated these interactions using both candidate gene and agnostic genome-wide approaches.

METHODS

To identify candidate gene-statin interactions, we tested interactions between 22 SNPS in nine candidate genes implicated in the effect of statins on lipid metabolism in 1687 cases and 1687 controls. We then evaluated statin use interaction with the remaining 30,380 SNPs available in this sample from the CGEMS GWAS study.

RESULTS

After adjusting for multiple comparisons, no SNP interactions with statin usage and risk of breast cancer were statistically significant in either the candidate genes or genome-wide approaches.

CONCLUSIONS

We found no evidence of SNP interactions with statin usage for breast cancer risk in a population of 3374 individuals. These results suggest that genome-wide common genetic variants do not moderate the association between statin usage and breast cancer in the population of women in the Women's Health Initiative.

Potentiating the effects of radiotherapy in rectal cancer: the role of aspirin, statins and metformin as adjuncts to therapy

BACKGROUND

Complete tumour response (pCR) to neo-adjuvant chemo-radiotherapy for rectal cancer is associated with a reduction in local recurrence and improved disease-free and overall survival, but is achieved in only 20-30% of patients. Drug repurposing for anti-cancer treatments is gaining momentum, but the potential of such drugs as adjuncts, to increase tumour response to chemo-radiotherapy in rectal cancer, is only just beginning to be recognised.

METHODS

A systematic literature search was conducted and all studies investigating the use of drugs to enhance response to neo-adjuvant radiation in rectal cancer were included. 2137 studies were identified and following review 12 studies were extracted for full text review, 9 studies were included in the final analysis.

RESULTS

The use of statins or aspirin during neo-adjuvant therapy was associated with a significantly higher rate of tumour downstaging. Statins were identified as a significant predictor of pCR and aspirin users had a greater 5-year progression-free survival and overall survival. Metformin use was associated with a significantly higher overall and disease-free survival, in a subset of diabetic patients.

CONCLUSIONS

Aspirin, metformin and statins are associated with increased downstaging of rectal tumours and thus may have a role as adjuncts to neoadjuvant treatment, highlighting a clear need for prospective randomised controlled trials to determine their true impact on tumour response and overall survival.

Current and Emerging Uses of Statins in Clinical Therapeutics: A Review

Statins, a class of cholesterol-lowering medications that inhibit 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, are commonly administered to treat atherosclerotic cardiovascular disease. Statin use may expand considerably given its potential for treating an array of cholesterol-independent diseases. However, the lack of conclusive evidence supporting these emerging therapeutic uses of statins brings to the fore a number of unanswered questions including uncertainties regarding patient-to-patient variability in response to statins, the most appropriate statin to be used for the desired effect, and the efficacy of statins in treating cholesterol-independent diseases. In this review, the adverse effects, costs, and drug–drug and drug–food interactions associated with statin use are presented. Furthermore, we discuss the pleiotropic effects associated with statins with regard to the onset and progression of autoimmune and inflammatory diseases, cancer, neurodegenerative disorders, strokes, bacterial infections, and human immunodeficiency virus. Understanding these issues will improve the prognosis of patients who are administered statins and potentially expand our ability to treat a wide variety of diseases.

HMGCR positively regulated the growth and migration of glioblastoma cells

The metabolic program of cancer cells is significant different from the normal cells, which makes it possible to develop novel strategies targeting cancer cells. Mevalonate pathway and its rate-limiting enzyme HMG-CoA reductase (HMGCR) have shown important roles in the progression of several cancer types. However, their roles in glioblastoma cells remain unknown. In this study, up-regulation of HMGCR in the clinical glioblastoma samples was observed. Forced expression of HMGCR promoted the growth and migration of U251 and U373 cells, while knocking down the expression of HMGCR inhibited the growth, migration and metastasis of glioblastoma cells. Molecular mechanism studies revealed that HMGCR positively regulated the expression of TAZ, an important mediator of Hippo pathway, and the downstream target gene connective tissue growth factor (CTGF), suggesting HMGCR might activate Hippo pathway in glioblastoma cells. Taken together, our study demonstrated the oncogenic roles of HMGCR in glioblastoma cells and HMGCR might be a promising therapeutic target.

Statin use and risk of primary liver cancer in the Clinical Practice Research Datalink

BACKGROUND

Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are widely prescribed to reduce cholesterol levels. Studies have suggested that statins are associated with reduced risk of liver cancer, but much of the evidence is from regions of the world with high liver cancer incidence rates. The current study examined the statins-liver cancer relationship in a low-rate region and examined the effects of preexisting liver disease and diabetes on that association.

METHODS

A nested case-control study was conducted within the United Kingdom's Clinical Practice Research Datalink (CPRD). Persons diagnosed with primary liver cancer between 1988 and 2011 were matched to controls at a four-to-one ratio. Matches stratified on liver disease and on diabetes were also completed. Odds ratios (ORs) and 95% confidence intervals (CIs) for associations of statins with liver cancer were estimated using conditional logistic regression.

RESULTS

In total, 1195 persons with primary liver cancer were matched to 4640 control patients. Statin use was associated with a statistically significantly reduced risk of liver cancer (ORadj = 0.55, 95% CI = 0.45 to 0.69), especially among current users (ORadj = 0.53, 95% CI = 0.42 to 0.66). The reduced risk was statistically significant in the presence (ORadj = 0.32, 95% CI = 0.17 to 0.57) and absence of liver disease (ORadj = 0.65, 95% CI = 0.52 to 0.81) and in the presence (ORadj = 0.30, 95% CI = 0.21 to 0.42) and absence of diabetes (ORadj = 0.66, 95% CI = 0.51 to 0.85).

CONCLUSIONS

In the current study in a low-rate area, statin use was associated with a statistically significantly reduced risk of liver cancer overall. Risk was particularly reduced among persons with liver disease and persons with diabetes, suggesting that statin use may be especially beneficial in persons at elevated risk of liver cancer.

Statins are potential anticancerous agents (review)

Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), which is a rate-limiting enzyme in the mevalonate pathway. The pleiotropic effects of statins may be mediated by the inhibition of downstream products such as small GTP-binding proteins, Rho, Ras and Rac whose localization and function are dependent on isoprenylation. Preclinical studies of statins in different cancer cell lines and animal models showed antiproliferative, pro‑apoptotic and anti-invasive effects. Notably, statins showed targeted action in cancerous cell lines compared to normal cells. Previous studies have also shown the synergistic effects of statins with chemotherapeutic agents and radiotherapy. This effect of statins was also observed in chemotherapeutic-resistant tumors. Statins were reported to sensitize the cells to radiation by arresting them in the late G1 phase of the cell cycle. Similarly, population-based studies also demonstrated a chemopreventive and survival benefit of statins in various types of cancers. However, this benefit has yet to be proven in clinical trials. The inter-individual variation in response to statins may be contributed to many genetic and non-genetic factors, including single-nucleotide polymorphisms in HMGCR gene and the overexpression of heterogeneous nuclear ribonucleoprotein A1, which was reported to reduce HMGCR enzyme activity. However, more studies with large phase III randomized controlled trials in cancer patients should be conducted to establish the effect of stains in cancer prevention and treatment.

Statins and cancers

Statins (inhibitors of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase) are a group of drugs used to treat lipid disorders. They inhibit cholesterol synthesis at an early stage of the biosynthesis pathway, thus eliminating numerous metabolites involved in the cycle. Numerous studies point to different possible effects of statins on cancer cells. Statins inhibit growth of a tumor, invasion and metastasis formation. They block the production of isoprenoids, which are necessary for post-translational modifications of many proteins, including those involved in normal cell signaling. They also contribute to the reduction in the expression of vascular endothelial growth factor, sensitize tumor cells to NK cell activity, and modify the body inflammatory response. Due to different pharmacokinetic properties of individual statins, they may have opposite effects on the risk of cancer. Currently, most information on the effects of statins on the risk of developing cancer is obtained from observational studies. The studies have different results depending on the location of cancer. The protective effect of statins was observed in the meta-analysis of numerous studies including prostate cancer, stomach cancer, esophagus cancer, and hepatocellular carcinoma; however, it has not yet been confirmed that statins influence the risk of developing colorectal cancer, breast cancer, or lung cancer. The protective effect of statins on the development of many kinds of cancer can be a valuable and easy way to reduce morbidity. However, further research is necessary to thoroughly determine the value of this group of drugs.

Role of EZH2 polymorphisms in esophageal squamous cell carcinoma risk in Han Chinese population

Gene single nucleotide polymorphisms play a critical role in the development of esophageal squamous cell carcinoma (ESCC). The aim of this study is to investigate the associations between EZH2 gene polymorphisms and ESCC risk. We undertook a case-control study to analyze three EZH2 polymorphisms (148505302C>T, 2110+6A>C and 626-394T>C) in an Han Chinese population, by extraction of genomic DNA from the peripheral blood of 476 patients with ESCC and 492 control participants, and performed EZH2 genotyping using DNA sequencing. The obtained results indicated that overall, no statistically significant association was observed in 148505302C>T and 2110+6A>C. However, 626-394T>C genotype was at increased risk of ESCCs (p=0.006; odds ratio (OR)=1.131, CI 95%: 1.034-1.236). Moreover, 626-394C/C genotype ESCCs were more significantly common in patients with tumor size of >5 cm than T allele ESCC and in cases of poor differentiation and lower advanced pathological stage. In conclusion, polymorphism in 626-394T>C was observed to be associated with susceptibility of ESCC. Nevertheless, further investigation with a larger sample size is needed to support our results.

Chemopreventive drugs: Mechanisms via inhibition of cancer stem cells in colorectal cancer

Recent epidemiological studies, basic research and clinical trials on colorectal cancer (CRC) prevention have helped identify candidates for effective chemopreventive drugs. However, because of the conflicting results of clinical trials or side effects, the effective use of chemopreventive drugs has not been generalized, except for patients with a high-risk for developing hereditary CRC. Advances in genetic and molecular technologies have highlighted the greater complexity of carcinogenesis, especially the heterogeneity of tumors. We need to target cells and processes that are critical to carcinogenesis for chemoprevention and treatment of advanced cancer. Recent research has shown that intestinal stem cells may serve an important role in tumor initiation and formation of cancer stem cells. Moreover, studies have shown that the tumor microenvironment may play additional roles in dedifferentiation, to enable tumor cells to take on stem cell features and promote the formation of tumorigenic stem cells. Therefore, early tumorigenic changes of stem cells and signals for dedifferentiation may be good targets for chemoprevention. In this review, I focus on cancer stem cells in colorectal carcinogenesis and the effect of major chemopreventive drugs on stem cell-related pathways.

HMG-CoA reductase expression in primary colorectal cancer correlates with favourable clinicopathological characteristics and an improved clinical outcome

BACKGROUND

An association between tumor-specific HMG-CoA reductase (HMGCR) expression and good prognosis has previously been demonstrated in breast and ovarian cancer. In this study, the expression, clinicopathological correlates and prognostic value of HMGCR expression in colorectal cancer was examined.

FINDINGS

Immunohistochemical expression of HMGCR was assessed in tissue microarrays with primary tumours from 557 incident cases of colorectal cancer in the Malmö Diet and Cancer Study. Pearson's Chi Square test was applied to explore the associations between HMGCR expression and clinicopathological factors and other investigative biomarkers. Kaplan Meier analysis and Cox proportional hazards modeling were used to assess the relationship between HMGCR expression and cancer-specific survival (CSS) according to negative vs positive HMGCR expression. A total number of 535 (96.0%) tumours were suitable for analysis, of which 61 (11.4%) were HMGCR negative. Positive cytoplasmic HMGCR expression was associated with distant metastasis-free disease at diagnosis (p = 0.002), lack of vascular invasion (p = 0.043), microsatellite-instability (p = 0.033), expression of cyclin D1 (p = <0.001) and p21 (p = <0.001). Positive HMGCR expression was significantly associated with a prolonged CSS in unadjusted Cox regression analysis in the entire cohort (HR = 1.79; 95% CI 1.20-2.66) and in Stage III-IV disease (HR = 1.71; 95% CI 1.09-2.68), but not after adjustment for established clinicopathological parameters.

CONCLUSIONS

Findings from this prospective cohort study demonstrate that HMGCR is differentially expressed in colorectal cancer and that positive expression is associated with favourable tumour characteristics and a prolonged survival in unadjusted analysis. The utility of HMGCR as a predictor of response to neoadjuvant or adjuvant statin treatment in colorectal cancer merits further study.

VIRTUAL SLIDES

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2115647072103464.

Statins and the risk of colorectal cancer: an updated systematic review and meta-analysis of 40 studies

AIM

To investigate the association between statin use and colorectal cancer risk, we conducted an updated meta-analysis of published studies.

METHODS

We performed a comprehensive search for studies published up to July 2013. Eligible studies for this meta-analysis were either randomized controlled trials (RCTs) or observational studies (case-control or cohort) evaluating any exposure to statins and the risk of colorectal cancer. Two reviewers selected studies based on predefined inclusion criteria, and abstracted the data. Pooled relative risk (RR) estimates with their 95%CI were calculated using fixed- and random-effects models. Then, we assessed the potential presence of publication bias and between-studies heterogeneity. To evaluate the results, we also performed a "leave-one-out" sensitivity analysis.

RESULTS

A total of 40 studies, involving more than eight million subjects, contributed to the analysis. They were grouped on the basis of study design and, consequently, three separate meta-analyses were conducted. A similar modest reduction in the risk of colorectal cancer with statin use was observed, which was not statistically significant among RCTs (RR = 0.89, 95%CI: 0.74-1.07; n = 8), but reached statistical significance among cohort studies (RR = 0.91, 95%CI: 0.83-1.00; n = 13) and case-control studies (RR = 0.92, 95%CI: 0.87-0.98; n = 19). While we did not find significant evidence of selective outcome reporting or publication bias, substantial heterogeneity was detected, mainly among the observational studies. The sensitivity analysis confirmed the stability of our results.

CONCLUSION

A modest reduction in risk of colorectal cancer among statin users cannot be disproved. Further targeted research is warranted.

Association between EZH2 polymorphisms and colorectal cancer risk in Han Chinese population

The aim of this study is to investigate the associations between EZH2 gene polymorphisms and colorectal cancer (CRC) risk. We undertook a case-control study to analyze three EZH2 polymorphisms (148505302C>T, 2110+6A>C and 626-394T>C) in an Han Chinese population, by extraction of genomic DNA from the peripheral blood of 512 patients with CRC and 546 control participants, and performed EZH2 genotyping using DNA sequencing. The obtained results indicated that overall, no statistically significant association was observed in 2,110+6A>C. Nevertheless, 148505302C>T genotype demonstrated a protective effect in CRCs (P=0.014; odds ratio (OR) 0.777, CI 95%:0.647-0.933). Furthermore, 148505302 T allele CRC was more significantly common in patients with tumor size of <4 cm than C allele CRC and in cases of good differentiation and lower advanced pathological stage. However, 626-394T>C genotype was at increased risk of CRCs (P<0.001; odds ratio (OR) 1.457, CI 95%:1.160-1.829). Moreover, 626-394C/C genotype CRCs were more significantly common in patients with tumor size of >4 cm than T allele CRC and in cases of poor differentiation and lower advanced pathological stage. In conclusion, polymorphism in 626-394T>C was observed to be associated with susceptibility of CRC. However, 148505302C>T polymorphism indicated to play a protective role in susceptibility to CRC. Nevertheless, further investigation with a larger sample size is needed to support our results.

[Chemoprevention of colorectal cancer in inflammatory bowel disease]

The risk of developing colorectal cancer is increased in patients with inflammatory bowel disease. Surveillance colonoscopy has not been shown to prolong survival and rates of interval cancer are reported to be high. Continuing colonic inflammation has been shown to be important in the development of colorectal cancer and therefore anti-inflammatory agents such as the 5-aminosalicylates and immunomodulators have been considered as potential chemopreventive agents. This review focuses on various chemopreventive agents that have been clearly shown to reduce the risk of colorectal adenoma and cancer in the patients with inflammatory bowel disease.

Prediction of survival in resected non-small cell lung cancer using a protein expression-based risk model: implications for personalized chemoprevention and therapy

PURPOSE

Patients with resected non-small cell lung cancer (NSCLC) are at risk for recurrence of disease, but we do not have tools to predict which patients are at highest risk. We set out to create a risk model incorporating both clinical data and biomarkers.

EXPERIMENTAL DESIGN

We assembled a comprehensive database with archival tissues and clinical follow-up from patients with NSCLC resected between 2002 and 2005. Twenty-one proteins identified from our preclinical studies as related to lung carcinogenesis were investigated, including pathways related to metabolism, DNA repair, inflammation, and growth factors. Expression of proteins was quantified using immunohistochemistry. Immunohistochemistry was chosen because it is widely available and can be performed on formalin-fixed paraffin-embedded specimens. Cox models were fitted to estimate effects of clinical factors and biomarkers on recurrence-free survival (RFS) and overall survival (OS).

RESULTS

A total of 370 patients are included in our analysis. With median follow-up of 5.3 years, median OS is 6.4 years. A total of 209 cases with recurrence or death were observed. Multicovariate risk models for RFS and OS were developed including relevant biomarkers, age, and stage. Increased expression of phospho-adenosine monophosphate-activated protein kinase (pAMPK), phospho-mTOR (pmTOR), epithelial cell adhesion molecule (EpCAM), and calcium/calmodulin-dependent serine protein kinase were significant (P < 0.05) predictors for favorable RFS; insulin receptor, chemokine (C-X-C motif) receptor 2 (CXCR2), and insulin-like growth factor-1 receptor predicted for unfavorable RFS. Significant (P < 0.05) predictors for favorable OS include pAMPK, pmTOR, and EpCAM; CXCR2 and flap structure-specific endonuclease-1 predicted unfavorable OS.

CONCLUSION

We have developed a comprehensive risk model predictive for recurrence in our large retrospective database, which is one of the largest reported series of resected NSCLC.

Polymorphisms in alcohol metabolism genes ADH1B and ALDH2, alcohol consumption and colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Epidemiological risk factors for CRC included alcohol intake, which is mainly metabolized to acetaldehyde by alcohol dehydrogenase and further oxidized to acetate by aldehyde dehydrogenase; consequently, the role of genes in the alcohol metabolism pathways is of particular interest. The aim of this study is to analyze the association between SNPs in ADH1B and ALDH2 genes and CRC risk, and also the main effect of alcohol consumption on CRC risk in the study population.

METHODOLOGY/PRINCIPAL FINDINGS

SNPs from ADH1B and ALDH2 genes, included in alcohol metabolism pathway, were genotyped in 1694 CRC cases and 1851 matched controls from the Molecular Epidemiology of Colorectal Cancer study. Information on clinicopathological characteristics, lifestyle and dietary habits were also obtained. Logistic regression and association analysis were conducted. A positive association between alcohol consumption and CRC risk was observed in male participants from the Molecular Epidemiology of Colorectal Cancer study (MECC) study (OR = 1.47; 95%CI = 1.18-1.81). Moreover, the SNPs rs1229984 in ADH1B gene was found to be associated with CRC risk: under the recessive model, the OR was 1.75 for A/A genotype (95%CI = 1.21-2.52; p-value = 0.0025). A path analysis based on structural equation modeling showed a direct effect of ADH1B gene polymorphisms on colorectal carcinogenesis and also an indirect effect mediated through alcohol consumption.

CONCLUSIONS/SIGNIFICANCE

Genetic polymorphisms in the alcohol metabolism pathways have a potential role in colorectal carcinogenesis, probably due to the differences in the ethanol metabolism and acetaldehyde oxidation of these enzyme variants.

Association between statin use and colorectal cancer risk: a meta-analysis of 42 studies

PURPOSE

There is a long-standing debate about whether statins have chemopreventive properties against colorectal cancer (CRC), but the results remain inconclusive. We therefore present a meta-analysis to investigate the association between statin use and risk of CRC.

METHODS

A comprehensive literature search was undertaken through July 2013 looking for eligible studies. Pooled relative risk (RR) estimates and 95 % confidence intervals (CIs) were used to calculate estimated effect.

RESULTS

Forty-two studies [18 case-control studies, 13 cohort studies, and 11 randomized controlled trials (RCTs)] were included in this analysis. Overall, statin use was associated with a modest reduction in the risk of CRC (RR = 0.90, 95 % CI 0.86-0.95). When the analyses were stratified into subgroups, a significant decreased association of CRC risk was observed in observational studies (RR = 0.89, 95 % CI 0.84-0.95), rectal cancer (RR = 0.81, 95 % CI 0.66-0.99), and lipophilic statin (RR = 0.88, 95 % CI 0.85-0.93), but not in RCTs (RR = 0.96, 95 % CI 0.85-1.08), colon cancer, and hydrophilic statin. However, long-term statin use (≥5 years) did not significantly affect the risk of CRC (RR = 0.96, 95 % CI 0.90-1.03). Cumulative meta-analysis showed that statin use significantly reduces the risk of CRC, which has been available between 2007 and 2013.

CONCLUSIONS

Our results suggest that statin use is associated with a modest reduced risk of CRC; apparent associations were found for lipophilic statin use. However, long-term statin use did not appear to significantly affect the risk of CRC.

A clinical trial of lovastatin for modification of biomarkers associated with breast cancer risk

Pre-clinical and epidemiologic studies provide rationale for evaluating lipophilic statins for breast cancer prevention. We conducted a single-arm, biomarker modulation trial of lovastatin among women with increased risk of breast cancer. Eligibility criteria included a deleterious germline mutation in BRCA1, BRCA2, CDH1, or TP53; lifetime breast cancer risk of ≥20 % as estimated by the Claus model; or personal history of estrogen receptor and progesterone receptor-negative breast cancer. Participants received 40 mg of lovastatin orally twice daily for 6 months. We evaluated the following biomarkers before and after lovastatin use: breast duct cytology (primary endpoint), serum lipids, C-reactive protein, insulin-like growth factor-1, IGF binding protein-3, lipid peroxidation, oxidative DNA damage, 3-hydroxy-3-methylglutaryl CoA reductase genotype, and mammographic density. Thirty women were enrolled, and 26 (86.7 %) completed the study. For the primary endpoint of changes in breast duct cytology sampled by random periareolar fine needle aspiration, most participants [57.7 %, 95 % confidence interval (CI) 38.9-74.5 %] showed no change after lovastatin; 19.2 % (CI 8.1-38.3 %) had a favorable change in cytology, 7.7 % (95 % CI 1.0-25.3 %) had an unfavorable change, and 15.4 % (95 % CI 5.5-34.2 %) had equivocal results due to acellular specimens, usually after lovastatin. No significant changes were observed in secondary biomarker endpoints. The study was generally well-tolerated: 4 (13.3 %) participants did not complete the study, and one (3.8 %) required a dose reduction. This trial was technically feasible, but demonstrated no significant biomarker modulation; contributing factors may include insufficient sample size, drug dose and/or duration. The results are inconclusive and do not exclude a favorable effect on breast cancer risk.

Prospective analysis of association between statin use and breast cancer risk in the women's health initiative

BACKGROUND

Statins are a class of cholesterol-lowering drugs that affect many intracellular pathways that may have implications for chemoprevention against cancer. Epidemiologic data on statins and breast cancer are conflicting. We analyzed updated data from the Women's Health Initiative (WHI) to assess the relationship between statins and breast cancer risk.

METHODS

The population included 154,587 postmenopausal women ages 50 to 79 years, with 7,430 pathologically confirmed cases of breast cancer identified over an average of 10.8 (SD, 3.3) years. Information on statins was collected at baseline and years one, three, six, and nine. Self- and interviewer-administered questionnaires were used to collect information on risk factors. Cox proportional hazards regression was used to calculate HRs with 95% confidence intervals (CI) to evaluate the relationship between statin use and cancer risk. Statistical tests were two-sided.

RESULTS

Statins were used by 11,584 (7.5%) women at baseline. The annualized rate of breast cancer was 0.42% among statin users and 0.42% among nonusers. The multivariable adjusted HR of breast cancer for users versus nonusers was 0.94 (95% CI, 0.83-1.06). In the multivariable-adjusted, time-dependent model, the HR for simvastatin was 0.87 (95% CI, 0.71-1.07). There was no significant trend by overall duration of use (P value for trend 0.68). There was no effect of tumor stage, grade, or hormone receptor status.

CONCLUSION

Overall, statins were not associated with breast cancer risk.

IMPACT

Our study is one of the largest prospective observational studies on this topic, and substantially adds to the literature suggesting no relationship between statins and breast cancer risk.

Beyond aspirin-cancer prevention with statins, metformin and bisphosphonates

Cancer risk reduction using pharmacological means is an attractive modern preventive approach that supplements the classical behavioural prevention recommendations. Medications that are commonly used by large populations to treat a variety of common, non-cancer-related, medical situations are an attractive candidate pool. This Review discusses three pharmacological agents with the most evidence for their potential as cancer chemopreventive agents: anti-hypercholesterolaemia medications (statins), an antidiabetic agent (metformin) and antiosteoporosis drugs (bisphosphonates). Data are accumulating to support a significant negative association of certain statins with cancer occurrence or survival in several major tumour sites (mostly gastrointestinal tumours and breast cancer), with an augmented combined effect with aspirin or other non-steroidal anti-inflammatory drugs. Metformin, but not other hypoglycaemic drugs, also seems to have some antitumour growth activity, but the amount of evidence in human studies, mainly in breast cancer, is still limited. Experimental and observational data have identified bisphosphonates as a pharmacological group that could have significant impact on incidence and mortality of more than one subsite of malignancy. At the current level of evidence these potential chemopreventive drugs should be considered in high-risk situations or using the personalized approach of maximizing individual benefits and minimizing the potential for adverse effects with the aid of pharmacogenetic indicators.

Effects of EZH2 polymorphisms on susceptibility to and pathological development of hepatocellular carcinoma

Background

The enhancer of zeste 2 (EZH2) gene encodes the histone methyltransferase that is the catalytic component of the polycomb repressive complex-2, which initiates epigenetic silencing of genes. The expression level of EZH2 in hepatocellular carcinoma (HCC) is highly correlated with tumor progression; however, it has not been determined if specific EZH2 genetic variants are associated with the risk of HCC. This study investigated the potential associations of EZH2 single-nucleotide polymorphisms with HCC susceptibility and its clinicopathologic characteristics.

Methodology/Principal Findings

A total of 220 HCC patients and 552 cancer-free controls were analyzed for four EZH2 single-nucleotide polymorphisms (rs6950683, rs2302427, rs3757441, and rs41277434) using real-time PCR genotyping. After adjusting for other co-variants, the individuals carrying at least one C allele at EZH2 rs6950683 and rs3757441 had a 0.611-fold and a 0.660-fold lower risk of developing HCC than did wild-type (TT) carriers, respectively. The CCCA or CCTA haplotype among the four EZH2 sites (rs6950683, rs2302427, rs3757441, and rs41277434), respectively, was also associated with a reduced risk of HCC. Furthermore, HCC patients who carried at least one C allele at rs6950683 or rs3757441 had a higher lymph–node-metastasis risk but a lower liver-cirrhosis risk than did patients carrying the wild-type allele.

Conclusions

The rs6950683 and rs3757441 polymorphic genotypes of EZH2 might contribute to the prediction of susceptibility to and pathological development of HCC. This is the first study to provide insight into risk factors associated with EZH2 variants in carcinogenesis of HCC in Taiwan.

The effects of age and gender on the relationship between HMGCR promoter-911 SNP (rs33761740) and serum lipids in patients with coronary heart disease

BACKGROUND

Hydroxymethylglutaryl-Coenzyme A Reductase (HMGCR) catalyzes the rate-limiting step of cholesterol biosynthesis. This enzyme is the target of the widely available cholesterol lowering statins. In this population-based case-control study, the frequencies of -911 C>A polymorphism (rs3761740) of the HMGCR gene in patients with coronary heart disease (CHD) and healthy subjects were investigated and the correlations between the different genotypes and hypercholesterolemia with cardiovascular risk factors were analyzed.

METHODS

The HMGCR genotypes were determined in 365 patients with CHD and 365 controls by PCR-RFLP assay. Anthropometric measurements were measured in all participants.

RESULTS

There was no significant difference in the genotype frequencies of the HMGCR polymorphism between the male subjects of both patient and control groups, however, the HMGCR-CC genotype was found to be more frequent in female patients with CHD than female controls (p=0.002). The HMGCR-CC genotype showed higher total-cholesterol (TC) and LDL-cholesterol (LDL-C) levels than the CA+AA genotypes in male CHD patients (p=0.018). Due to this significant sex interaction, a multivariate analysis was conducted on the patient group. In the multivariate logistic regression analysis, the HMGCR-CC genotype was significantly associated with age<55 (OR=2.837, p=0.001) and TC ≥ 5.18 mmol/L (OR=1.970, p=0.027) in male subjects. However, this association was not observed in female patients (p>0.05). This analysis confirmed that the HMGCR-CC genotype was associated with elevated TC levels in male CHD patients with age<55 years.

CONCLUSION

These results suggest that age and sex modify the contribution of the HMGCR-911 polymorphism to fasting serum TC, LDL-C levels and risk of CHD.

The effect of statins on risk and survival of gynecological malignancies

PURPOSE

The use of statins has been associated with reduced risk of malignancies in a variety of organ sites. This study was aimed at studying the effects of statins on gynecological cancers.

METHODS

The Cancer in The Ovary and Uterus Study (CITOUS) is a case-control study of newly diagnosed cases of gynecological malignancies and age/sex/clinic/ethnic-group matched population controls. Use of statins prior to and following diagnosis was assessed in a subset of 424 cases of ovarian and endometrial cancers and 341 controls, enrolled in Clalit Health Services (CHS), using pharmacy records.

RESULTS

The use of statins for more than one year prior to diagnosis was associated with a significantly reduced risk of ovarian cancer (OR=0.56, 95% CI: 0.33-0.94) and of endometrial cancer (OR=0.59, 95% CI: 0.40-0.87). The association with endometrial cancer, but not with ovarian cancer (OR=0.54, 0.26-1.13), remained statistically significant after adjustment for fruit and vegetable consumption, sports activity, family history of endometrial and colorectal cancer, ethnicity, BMI, duration of breast feeding, age at 1st pregnancy and use of menopausal hormones (RR=0.48, 0.26-0.89). Women who used statins only after diagnosis of cancer had a significantly better survival of both ovarian cancer (Log rank test, p=0.021, age adjusted HR=0.47, 0.26-0.85) and endometrial cancer (p=0.06, age adjusted HR=0.45, 0.23-0.87).

CONCLUSION

The use of statins for more than one year before diagnosis was associated with a reduction in the risk of endometrial cancer and possibly ovarian cancer. A significantly improved survival of cases of both malignancies was noticed when statins were taken only after diagnosis.

Alternative splicing in the regulation of cholesterol homeostasis

PURPOSE OF REVIEW

With the advent of whole-transcriptome sequencing, or RNA-seq, we now know that alternative splicing is a generalized phenomenon, with nearly all multiexonic genes subject to alternative splicing. In this review, we highlight recent studies examining alternative splicing as a modulator of cellular cholesterol homeostasis and as an underlying mechanism of dyslipidemia.

RECENT FINDINGS

A number of key genes involved in cholesterol metabolism are known to undergo functionally relevant alternative splicing. Recently, we have identified coordinated changes in alternative splicing in multiple genes in response to alterations in cellular sterol content. We and others have implicated several splicing factors as regulators of lipid metabolism. Furthermore, a number of cis-acting human gene variants that modulate alternative splicing have been implicated in a variety of human metabolic diseases.

SUMMARY

Alternative splicing is of importance in various types of genetically influenced dyslipidemias and in the regulation of cellular cholesterol metabolism.

Statin use is associated with a reduced incidence of colorectal adenomatous polyps

BACKGROUND

Hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) have been shown to have potentially useful anticancer effects against colorectal cancers in experimental studies, but clinical studies have shown inconsistent results on colorectal cancer incidence. Most colorectal cancers are believed to develop through the polyp-cancer sequence. We hypothesized that statins may protect against the development of adenomatous polyps, and this may contribute to the apparent cancer-protective effects.

OBJECTIVE

This study aims to compare previous statin use in patients with newly diagnosed adenomatous polyps against a control group without polyps.

METHOD

A case-control study involving 264 patients attending for diagnostic colonoscopy at the Norfolk and Norwich University Hospital was used. Polyp cases were age and sex matched against controls with normal colonoscopies. Structured patient interviews and clinical notes were used to ascertain drug and risk factor. Logistic regression was used to compare statin exposure and correct for confounding factors.

RESULTS

There was a significant negative association between prior statin use and a diagnosis of adenomatous polyps [odds ratio (OR) = 0.40 (0.24-0.76)]. The association was significantly stronger with higher statin doses [≥40 mg simvastatin or equivalent; OR 0.33 (0.10-0.53)] or longer duration of use [>5 years; OR 0.36 (0.10-0.67)]. Statin use was negatively associated with both high- and low-risk polyps.

CONCLUSIONS

Statins may have a protective effect against the development of adenomatous polyps. The negative association between statin use and polyp incidence showed a significant dose and duration relationship.

BAYESIAN SEMIPARAMETRIC ANALYSIS FOR TWO-PHASE STUDIES OF GENE-ENVIRONMENT INTERACTION

The two-phase sampling design is a cost-efficient way of collecting expensive covariate information on a judiciously selected sub-sample. It is natural to apply such a strategy for collecting genetic data in a sub-sample enriched for exposure to environmental factors for gene-environment interaction (G × E) analysis. In this paper, we consider two-phase studies of G × E interaction where phase I data are available on exposure, covariates and disease status. Stratified sampling is done to prioritize individuals for genotyping at phase II conditional on disease and exposure. We consider a Bayesian analysis based on the joint retrospective likelihood of phase I and phase II data. We address several important statistical issues: (i) we consider a model with multiple genes, environmental factors and their pairwise interactions. We employ a Bayesian variable selection algorithm to reduce the dimensionality of this potentially high-dimensional model; (ii) we use the assumption of gene-gene and gene-environment independence to trade-off between bias and efficiency for estimating the interaction parameters through use of hierarchical priors reflecting this assumption; (iii) we posit a flexible model for the joint distribution of the phase I categorical variables using the non-parametric Bayes construction of Dunson and Xing (2009). We carry out a small-scale simulation study to compare the proposed Bayesian method with weighted likelihood and pseudo likelihood methods that are standard choices for analyzing two-phase data. The motivating example originates from an ongoing case-control study of colorectal cancer, where the goal is to explore the interaction between the use of statins (a drug used for lowering lipid levels) and 294 genetic markers in the lipid metabolism/cholesterol synthesis pathway. The sub-sample of cases and controls on which these genetic markers were measured is enriched in terms of statin users. The example and simulation results illustrate that the proposed Bayesian approach has a number of advantages for characterizing joint effects of genotype and exposure over existing alternatives and makes efficient use of all available data in both phases.

Statins and colorectal cancer

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, more commonly referred to as statins, comprise a family of lipid-lowering drugs that are prescribed on a global scale on account of their proven safety and efficacy in reducing mortality from cardiovascular disease. Beyond their potent pharmacologic inhibition of cholesterol biosynthesis, statins appear to have pleiotropic effects, including modulation of cell growth, apoptosis, and inflammation. Through modulation of these pathways, statins have the potential to influence a wide range of disease processes, including cancer. Much attention has focused on the association between statins and colorectal cancer, raising the prospect that these well-tolerated compounds could form the basis of future chemopreventive strategies. Herein, we review the epidemiologic, clinical, and preclinical data relevant to statins and colorectal neoplasia, and discuss the current status and future potential of statins as chemopreventive agents.

Mevalonate pathway is a therapeutic target in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common lethal tumors in the world. Thus, it is very urgent to develop new therapeutic targets against this disease. The mevalonate (MVA) pathway, paced by its rate-limiting enzyme, hydroxymethylglutaryl coenzyme A reductase, is required for the generation of several fundamental end products including cholesterol and isoprenoids. The function of the MVA pathway in ESCC has not been investigated. In this study, it was found that the MVA pathway was upregulated in ESCC clinical samples. Statin, the inhibitor of the MVA pathway, exerted potent cytotoxicity against human ESCC cells by inhibiting cell growth and proliferation, while it exerted lesser effects on non-tumorigenic SHEE cells. Further study revealed that statin could potently induce cell apoptosis and cell cycle arrest and also dose-dependently inhibit the growth of xenograft tumors in nude mice. With regard to the molecular mechanism, statin treatment was related to decreased extracellular signal-regulated kinase activation and proliferating cell nuclear antigen, cyclin D1 expression, and increased cleavage of poly(ADP-ribose) polymerase. Taken together, our findings suggest that the MVA pathway plays an important role in the progression of ESCC by modulating cell growth and statin might be a potential therapeutic agent in ESCC.

Potentially important considerations in choosing specific statin treatments to reduce overall morbidity and mortality

Hypercholesterolemia and dyslipidemia are independent risk factors for cardiovascular disease and death. Statins are the drugs of choice to decrease plasma cholesterol and have other beneficial actions beyond lipid-lowering leading to substantial improvements in cardiovascular morbidity and mortality. However, evaluation of the effects of statins to reduce overall morbidity and mortality must integrate metabolic consequences of statin therapy with its lipid-lowering effect. Indeed, reduction in LDL-cholesterol to target level achieved by statins does not completely eliminate risk of cardiovascular disease and may elevate metabolic risk factors that contribute to dysregulation of metabolic homeostasis. This may lead to increased incidence of diabetes and its cardiovascular complications that are explained, in part, by reciprocal relationships between insulin resistance and endothelial dysfunction. Genetic factors may determine 40-60% of total cholesterol levels and 70% of the efficacy of statin treatments. Metabolic and cardiovascular phenotypes that are either genetically determined or environmentally acquired are also important determinants of responses to specific statins. Moreover, differences between biological outcomes of specific statins or increasing dosages of statins result in differential metabolic actions due to off-target or unknown mechanism that have important implications for the use of statins to reduce overall morbidity and mortality. In this review, we discuss differential cardiovascular and metabolic pleiotropic actions of specific statins that interact in a context-dependent manner with patient phenotypes and genotypes. These important considerations may influence progression of atherosclerosis, risk of diabetes, and modulation of insulin resistance that help determine overall morbidity and mortality in patients undergoing statin therapy.

Cholesterol metabolism and colorectal cancers

Colorectal cancer (CRC) is primarily a lifestyle disease of the western world. As such it can be likened to cardiovascular disease and indeed it shares many of the same risk factors. It is therefore perhaps unsurprising that cholesterol metabolism and colorectal cancer are also intricately linked. Many of the initial studies suggesting a link between dietary cholesterol, blood cholesterol levels and cholesterol lowering drugs were performed more than a decade ago. The most recent insights in this field are the result of meta-analyses, advances in pharmacogenetics and the new field of molecular pathological epidemiology. This review summarises the current evidence linking cholesterol metabolism with colorectal cancer including the suggested underlying molecular causes and the implications for colorectal cancer prevention.

Genetic polymorphisms in fatty acid metabolism genes and colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Epidemiological risk factors for CRC included dietary fat intake; consequently, the role of genes in the fatty acid biosynthesis and metabolism pathways is of particular interest. Moreover, hyperlipidaemia has been associated with different type of cancer and serum lipid levels could be affected by genetic factors, including polymorphisms in the lipid metabolism pathway. The aim of this study is to assess the association between single-nucleotide polymorphisms (SNPs) in fatty acid metabolism genes, serum lipid levels, body mass index (BMI) and dietary fat intake and CRC risk; 30 SNPs from 8 candidate genes included in fatty acid biosynthesis and metabolism pathways were genotyped in 1780 CRC cases and 1864 matched controls from the Molecular Epidemiology of Colorectal Cancer study. Information on clinicopathological characteristics, lifestyle and dietary habits were also obtained. Logistic regression and association analysis were conducted. Several LIPC (lipase, hepatic) polymorphisms were found to be associated with CRC risk, although no particular haplotype was related to CRC. The SNP rs12299484 showed an association with CRC risk after Bonferroni correction. We replicate the association between the T allele of the LIPC SNP rs1800588 and higher serum high-density lipoprotein levels. Weak associations between selected polymorphism in the LIPC and PPARG genes and BMI were observed. A path analysis based on structural equation modelling showed a direct effect of LIPC gene polymorphisms on colorectal carcinogenesis as well as an indirect effect mediated through serum lipid levels. Genetic polymorphisms in the hepatic lipase gene have a potential role in colorectal carcinogenesis, perhaps though the regulation of serum lipid levels.

An EZH2 polymorphism is associated with clinical outcome in metastatic colorectal cancer patients

BACKGROUND

Despite therapeutic innovations, metastatic colorectal cancer (mCRC) is still characterized by poor prognosis and few molecular markers predict the risk of progression. Polycomb group genes (PcGs) are epigenetic modifiers involved in tumor suppressor gene silencing. PcG member EZH2 mediates gene silencing through histone-H3 lysine-27 methylation. In colorectal cancer (CRC), EZH2 overexpression predicts shorter survival. Recently, four EZH2 single-nucleotide polymorphisms (SNPs) have been described. The present study was aimed at evaluating the correlation between EZH2 SNPs and outcome parameters in mCRC patients.

PATIENTS AND METHODS

DNA was extracted from blood samples of 110 mCRC patients treated with first-line 5-fluorouracil, folinic acid, irinotecan (FOLFIRI) and bevacizumab. Genotyping was carried out by real-time PCR. Genotype was used to predict objective response, progression-free survival (PFS) and overall survival (OS). EZH2 messenger RNA levels were evaluated on lymphocytes of a parallel cohort of 50 CRC patients.

RESULTS

One allelic variant (rs3757441 C/C versus C/T or T/T) was significantly associated with shorter PFS and OS (P < 0.01 and P < 0.05, respectively). At multivariate analysis, the same variant resulted an independent predictor of PFS and OS (P < 0.05). The C/C variant was associated with significantly higher EZH2 expression (P < 0.05).

CONCLUSION

An EZH2 SNP may be useful to predict clinical outcome in mCRC patients.