The complex interplay between cholesterol and prostate malignancy

Obesity and main urologic cancers: Current systematic evidence, novel biological mechanisms, perspectives and challenges

Urologic cancers (UC) account for 13.1% of all new cancer cases and 7.9% of all cancer-related deaths. A growing body of evidence has indicated a potential causal link between obesity and UC. The aim of the present review is to appraise in a critical and integrative manner evidence from meta-analyses and mechanistic studies on the role of obesity in four prevalent UC (kidney-KC, prostate-PC, urinary bladder-UBC, and testicular cancer-TC). Special emphasis is given on Mendelian Randomization Studies (MRS) corroborating a genetic causal association between obesity and UC, as well as on the role of classical and novel adipocytokines. Furthermore, the molecular pathways that link obesity to the development and progression of these cancers are reviewed. Available evidence indicates that obesity confers increased risk for KC, UBC, and advanced PC (20-82%, 10-19%, and 6-14%, respectively), whereas for TC adult height (5-cm increase) may increase the risk by 13%. Obese females tend to be more susceptible to UBC and KC than obese males. MRS have shown that a higher genetic-predicted BMI may be causally linked to KC and UBC but not PC and TC. Biological mechanisms that are involved in the association between excess body weight and UC include the Insulin-like Growth Factor axis, altered availability of sex hormones, chronic inflammation and oxidative stress, abnormal secretion of adipocytokines, ectopic fat deposition, dysbiosis of the gastrointestinal and urinary tract microbiomes and circadian rhythm dysregulation. Anti-hyperglycemic and non-steroidal anti-inflammatory drugs, statins, and adipokine receptor agonists/antagonists show potential as adjuvant cancer therapies. Identifying obesity as a modifiable risk factor for UC may have significant public health implications, allowing clinicians to tailor individualized prevention strategies for patients with excess body weight.

Metabolic syndrome and its components predict the biochemical recurrence and adverse pathological features of patients following radical prostatectomy: a propensity score matching study

BACKGROUND

To investigate the predictive value of metabolic syndrome (MetS) and its components in biochemical recurrence (BCR) and adverse pathological features of patients with prostate cancer (PCa) after radical prostatectomy (RP).

METHODS

A total of 525 PCa patients who underwent RP between 2010 and 2019 at Peking University Third Hospital were analyzed retrospectively. The Kaplan-Meier method was performed to assess BCR-free survival (BCRFS). Univariate and multivariate Cox regression models and multivariate logistic regression models were conducted to identify the predictive factors of BCRFS and adverse pathological features respectively before and after propensity score matching (PSM).

RESULTS

Enrolled patients were allocated into MetS group (n = 136) and non-MetS group (n = 389) according to the presence or absence of MetS, and 127 new matched pairs were identified to balance the baseline characteristics after 1:1 PSM. In propensity matched patients, the Kaplan-Meier analysis revealed that MetS (P = 0.020), hyperglycemia (P = 0.015) and hypertriglyceridemia (P = 0.001) were significantly associated with worse BCRFS; the results of multivariate Cox analyses showed that hyperglycemia (P = 0.040), hypertriglyceridemia (P = 0.017), percentage of positive biopsy cores (P = 0.041) and prostate specific antigen (P = 0.019) were identified as independent prognostic factors for BCRFS. In addition, hypertriglyceridemia was independently associated with non-organ confined disease (NOCD) (P = 0.010), extra-capsular extension (ECE) (P = 0.010) and upgrading (P = 0.017) in the multivariate logistic analyses.

CONCLUSIONS

Hyperglycemia and hypertriglyceridemia are the two effective MetS components both identified as independent risk factors for worse BCRFS after RP, while hypertriglyceridemia was independently associated with NOCD, ECE and upgrading as well.

Relationship between 4-Hydroxynonenal (4-HNE) as Systemic Biomarker of Lipid Peroxidation and Metabolomic Profiling of Patients with Prostate Cancer

An oxidative degradation product of the polyunsaturated fatty acids, 4-hydroxynonenal (4-HNE), is of particular interest in cancer research due to its concentration-dependent pleiotropic activities affecting cellular antioxidants, metabolism, and growth control. Although an increase in oxidative stress and lipid peroxidation was already associated with prostate cancer progression a few decades ago, the knowledge of the involvement of 4-HNE in prostate cancer tumorigenesis is limited. This study investigated the appearance of 4-HNE-protein adducts in prostate cancer tissue by immunohistochemistry using a genuine 4-HNE monoclonal antibody. Plasma samples of the same patients and samples of the healthy controls were also analyzed for the presence of 4-HNE-protein adducts, followed by metabolic profiling using LC-ESI-QTOF-MS and GC-EI-Q-MS. Finally, the analysis of the metabolic pathways affected by 4-HNE was performed. The obtained results revealed the absence of 4-HNE-protein adducts in prostate carcinoma tissue but increased 4-HNE-protein levels in the plasma of these patients. Metabolomics revealed a positive association of different long-chain and medium-chain fatty acids with the presence of prostate cancer. Furthermore, while linoleic acid positively correlated with the levels of 4-HNE-protein adducts in the blood of healthy men, no correlation was obtained for cancer patients indicating altered lipid metabolism in this case. The metabolic pathway of unsaturated fatty acids biosynthesis emerged as significantly affected by 4-HNE. Overall, this is the first study linking 4-HNE adduction to plasma proteins with specific alterations in the plasma metabolome of prostate cancer patients. This study revealed that increased 4-HNE plasma protein adducts could modulate the unsaturated fatty acids biosynthesis pathway. It is yet to be determined if this is a direct result of 4-HNE or whether they are produced by the same underlying mechanisms. Further mechanistic studies are needed to grasp the biological significance of the observed changes in prostate cancer tumorigenesis.

PCSK9 facilitates melanoma pathogenesis via a network regulating tumor immunity

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Tissue cholesterol metabolism and prostate cancer aggressiveness: Ethno-geographic variations

BACKGROUND

Prostate cancer (PCa) is more frequent and more aggressive in populations of African descent than in Caucasians. Since the fatty acid composition of peri-prostatic adipose tissue (PPAT) has been shown to differ according to the ethno-geographic origin and is involved in PCa aggressiveness, we aimed to analyze the cholesterol content of PPAT from Caucasian and African-Caribbean patients, in correlation with markers of disease aggressiveness and cholesterol metabolism in cancer tissues.

METHODS

The quantification of cholesterol in PPAT was analyzed in 52 Caucasian and 52 African-Caribbean PCa patients, with in each group 26 indolent tumors (ISUP Group1 and pT2) and 26 potentially aggressive tumors (ISUP Group 3-5 and/or pT3). The expression of proteins involved in cholesterol metabolism was analyzed by immunohistochemistry on cancer tissue samples included in tissue microarrays.

RESULTS

The amount of cholesterol esters was lower in PPAT from African-Caribbean patients compared with Caucasians, without any correlation with markers of disease aggressiveness. In cancer tissues from African-Caribbean patients, the expression of ABCA1 (involved in cholesterol efflux) was decreased, and that of SREBP-2 (involved in cholesterol uptake) was increased. In both groups of patients, SREBP-2 expression was strongly associated with that of Zeb1, a key player in the epithelial-to-mesenchymal transition (EMT) process.

CONCLUSION

These results suggest that cholesterol metabolism differs according to the ethno-geographic origin, in both PPAT and cancer tissues. In African-Caribbeans, the orientation towards accumulation of cholesterol in cancer cells is associated with a more frequent state of EMT, which may promote PCa aggressiveness in this population.

Inhibition of Scavenger Receptor Class B Type 1 (SR-B1) Expression and Activity as a Potential Novel Target to Disrupt Cholesterol Availability in Castration-Resistant Prostate Cancer

There have been several studies that have linked elevated scavenger receptor class b type 1 (SR-B1) expression and activity to the development and progression of castration-resistant prostate cancer (CRPC). SR-B1 facilitates the influx of cholesterol to the cell from lipoproteins in systemic circulation. This influx of cholesterol may be important for many cellular functions, including the synthesis of androgens. Castration-resistant prostate cancer tumors can synthesize androgens de novo to supplement the loss of exogenous sources often induced by androgen deprivation therapy. Silencing of SR-B1 may impact the ability of prostate cancer cells, particularly those of the castration-resistant state, to maintain the intracellular supply of androgens by removing a supply of cholesterol. SR-B1 expression is elevated in CRPC models and has been linked to poor survival of patients. The overarching belief has been that cholesterol modulation, through either synthesis or uptake inhibition, will impact essential signaling processes, impeding the proliferation of prostate cancer. The reduction in cellular cholesterol availability can impede prostate cancer proliferation through both decreased steroid synthesis and steroid-independent mechanisms, providing a potential therapeutic target for the treatment of prostate cancer. In this article, we discuss and highlight the work on SR-B1 as a potential novel drug target for CRPC management.

Predictive role of serum cholesterol and triglycerides in cervical cancer survival

OBJECTIVE

Lipids have been evaluated for their possible role in cancer survival prediction. The aim of the current study was to investigate the prognostic value of lipids on overall survival for stage IB1-IIA2 cervical cancer patients.

METHODS

A retrospective study including cervical cancer patients with early-stage (FIGO 2009 stage IB1-IIA2) disease was conducted from January 2012 to February 2017. Patients with any history of liver disease or other cancers, and patients who took any medications known to influence lipid metabolism, were excluded. We measured various factors in patients' lipid profiles including total cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein, and assessed these four parameters together with clinicopathological features to identify the significant prognostic factors for overall survival.

RESULTS

A total of 583 patients with median age 53 (range 25-82) years were included. Among them, 283 (48.5%) patients were in FIGO stage IB1, 44 patients (7.6%) in stage IB2, 189 (32.4%) patients in stage IIA1, and the remaining 67 (11.5%) patients were in stage IIA2. Using univariable Cox proportional hazard analysis and subsequent multivariable analysis, total cholesterol, triglycerides, and pelvic lymph node status were shown to be independent prognostic factors for overall survival (p<0.05 for all). Furthermore, the results of the Kaplan-Meier survival curves showed that both the high total cholesterol group and the high triglycerides group were associated with worse overall survival (p=0.002 and p=0.001, respectively) CONCLUSIONS: Our study showed that total triglycerides and total cholesterol may serve as potential predictors for overall survival in patients with cervical cancer. Cervical cancer patients may benefit from treatments after adjusting their triglycerides and total cholesterol levels.

The role of cholesterol and cholesterol-driven membrane raft domains in prostate cancer

Membrane rafts are heterogeneous and dynamic domains that are characterized by tight packing of lipids. They are enriched in cholesterol, sphingolipids, and certain types of proteins. Among these are various cell signaling proteins, which indicate that rafts play an important role in cell signal transduction pathways, including some involved in cancer development, progression, and invasiveness. Due to their increased cholesterol content, raft domains exhibit lower fluidity than the surrounding membrane. The cell membranes of some solid tumors, such as breast and prostate cancer, contain higher levels of cholesterol, which means larger raft domain can form in those membranes. This may stimulate signaling pathways to promote tumor growth and progression. This review focuses on the known raft-dependent regulatory mechanisms that promote prostate cancer progression.

Impact statement

Prostate cancer remains the most common malignancy and second most frequent cause of cancer-related death in men. Cholesterol levels are usually higher in prostate cancer cells. This affects the cell membrane composition, with cholesterol and sphingolipid-containing raft membrane domains becoming a greater component. In addition to polar lipids, these domains recruit and regulate certain types of protein, including various cell signaling proteins that are critical to cancer cell survival and invasiveness. This suggests that membrane rafts have a regulatory role in tumor progression, making them a potential target in prostate cancer treatment.

Physical resistance training-induced changes in lipids metabolism pathways and apoptosis in prostate

BACKGROUND

Altered lipid metabolism is an important characteristic of neoplastic cells, with androgens and growth factors being major regulatory agents of the lipid metabolism process. We investigated the effect of physical resistance training on lipid metabolism and apoptosis in the adult Wistar rat prostate.

METHODS

Two experimental groups represented sedentary and physical resistance training. Three days per week for 13 weeks, rats performed jumps in water carrying a weight load strapped to their chests as part of a physical resistance exercise protocol. Two days after the last training session, rats were anesthetized and sacrificed for blood and prostate analysis.

RESULTS

Physical exercise improved feeding efficiency, decreased weight gain, regulated the serum-lipid profile, and modulated insulin-like growth factor-1 (IGF-1) and free testosterone concentration. Furthermore, upregulation of cluster of differentiation 36 (CD36), sterol regulatory element binding protein-1 (SREBP-1), sterol regulatory element-binding protein cleavage-activating protein (SCAP), and reduced lysosome membrane protein (LIMPII) expression were also observed in the blood and prostates of trained rats. Consistent with these results, caspase-3 expression was upregulating and the BCL-2/Bax index ratio was decreased in trained rats relative to sedentary animals.

CONCLUSIONS

In this work, physical resistance training can alter lipid metabolism and increase markers of apoptosis in the prostate, suggesting physical resistance training as a potential novel therapeutic strategy for treating prostate cancer.

Atorvastatin Improves Hepatic Lipid Metabolism and Protects Renal Damage in Adenine-Induced Chronic Kidney Disease in Sprague-Dawley Rats

Objective

Chronic kidney disease (CKD), including nephrotic syndrome, is a major cause of cardiovascular morbidity and mortality. The literature indicates that CKD is associated with profound lipid disorders largely due to the dysregulation of lipoprotein metabolism which further aggravates the progression of kidney disease. The present study sought to determine the efficacy of atorvastatin treatment on hepatic lipid metabolism and renal tissue damage in CKD rats.

Methods

Serum, hepatic and faecal lipid contents and the expression and enzyme activity of molecules involved in cholesterol and triglyceride metabolism, along with kidney function, were determined in untreated adenine-induced CKD, atorvastatin-treated CKD (10 mg/kg/day oral for 24 days) and control rats.

Key Findings

CKD resulted in metabolic dyslipidaemia, renal insufficiency, hepatic lipid accumulation, upregulation of 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase, acyl-CoA cholesterol acyltransferase-2 (ACAT2) and the downregulation of LDL receptor protein, VLDL receptor, hepatic lipase, lipoprotein lipase (LPL), lecithin–cholesterol acyltransferase (LCAT) and scavenger receptor class B type 1 (SR-B1). CKD also resulted in increased enzymatic activity of HMG-CoA reductase and ACAT2 together with decreased enzyme activity of lipase and LCAT. Atorvastatin therapy attenuated dyslipidaemia, renal insufficiency, reduced hepatic lipids, HMG-CoA reductase and ACAT2 protein abundance and raised LDL receptor and lipase protein expression. Atorvastatin therapy decreased the enzymatic activity of HMG-CoA reductase and increased enzymatic activity of lipase and LCAT.

Conclusions

Atorvastatin improved hepatic tissue lipid metabolism and renal function in adenine-induced CKD rats.

Statin Use and the Risk of Prostate Cancer in Ischemic Heart Disease Patients in Taiwan

Patients with ischemic heart disease (IHD) are more likely to be diagnosed with prostate cancer. Statins, which are widely used in such patients, are shown to modify the risk of prostate cancer. To clarify the association between statin use and the risk of prostate cancer among patients with higher risk of developing prostate cancer in Taiwan, a cohort of 26,628 men with IHD and aged between 55 and 100 were acquired from the National Health Insurance Research Database and followed over a period of 8 years. The risk of prostate cancer was calculated by time-dependent Cox regression model. Statin use was associated with significantly lower risk of both total and advanced prostate cancer (adjusted hazard ratio (HR): 0.719, 95% confidence interval (CI): 0.570-0.908; adjusted HR: 0.718, 95% CI: 0.530-0.972 respectively). In Taiwan IHD population, the reduction in risk of prostate cancer was observed in statin users as compared with nonusers.

Prostate cancer incidence and mortality among men using statins and non-statin lipid-lowering medications

BACKGROUND

Statins have demonstrated protection against aggressive/late-stage and/or lethal prostate cancer (PC), but prior studies are limited by small populations, short follow-up and unequal health-care access. Research has not demonstrated that non-statin lipid-lowering medications (NSLLMs) provide a similar benefit, which would support a cholesterol-based mechanism. We sought to rigorously test the hypothesis that cholesterol-lowering drugs affect PC incidence and severity.

METHODS

A retrospective cohort study was conducted by abstracting prescription and health service records for 249,986 Saskatchewan men aged ≥40 years between January 1, 1990 and December 31, 2014 and comparing first-time statin and NSLLM users with age-matched non-users and glaucoma medication (GM) users for PC incidence, metastases at diagnosis and PC mortality using Cox proportional hazards regression.

RESULTS

In comparing statin users to non-users, a weak association was detected with increased PC incidence (hazard ratio [HR] 1.07, 95% confidence interval [CI]: 1.02-1.12) that disappeared when compared with GM users. Substantial protective associations were observed between statin use and metastatic PC and PC mortality (HRs 0.69, 95% CI: 0.61-0.79 and 0.73, 95% CI: 0.66-0.81, respectively), which were stronger when compared with GM use (HRs 0.52, 95% CI: 0.40-0.68 and 0.51, 95% CI: 0.41-0.63, respectively). Similar associations were found for NSLLM versus GM for metastatic PC (HR 0.57, 95% CI: 0.41-0.79) and PC mortality (HR 0.66, 95% CI: 0.51-0.85).

CONCLUSIONS

Our analyses provide one of the more comprehensive findings to date that statins may reduce risk of metastatic PC and PC mortality, and the first to demonstrate that NSLLM have similar effects, supporting a cholesterol-based mechanism.

The role of cholesterol metabolism in cancer

Cholesterol plays an important role in cancer development. Both clinical and experimental studies have found that hypercholesterolemia and a high-fat high-cholesterol diet can affect cancer development. External cholesterol can directly activate the oncogenic Hedgehog pathway, and internal cholesterol can induce mTORC1 signaling. Cholesterol is a key component of lipid rafts, which are the major platforms for signaling regulation in cancer, and chelating membrane cholesterol is an effective anti-cancer strategy that disrupts the functions of lipid rafts. Cholesterol metabolism is often reprogrammed in cancer cells. Targeting cholesterol metabolism as a new therapeutic approach has received increasing attention. Here, we summarize some key molecular mechanisms supporting the use of anti-cholesterol therapy for cancer treatment.

High-density lipoprotein functionality and breast cancer: A potential therapeutic target

Breast cancer is a major cause of death globally, and particularly in developed countries. Breast cancer is influenced by cholesterol membrane content, by affecting the signaling pathways modulating cell growth, adherence, and migration. Furthermore, steroid hormones are derived from cholesterol and these play a key role in the pathogenesis of breast cancer. Although most findings have reported an inverse association between serum high-density lipoprotein (HDL)-cholesterol level and the risk of breast cancer, there have been some reports of the opposite, and the association therefore remains unclear. HDL is principally known for participating in reverse cholesterol transport and has an inverse relationship with the cardiovascular risk. HDL is heterogeneous, with particles varying in composition, size, and structure, which can be altered under different circumstances, such as inflammation, aging, and certain diseases. It has also been proposed that HDL functionality might have a bearing on the breast cancer. Owing to the potential role of cholesterol in cancer, its reduction using statins, and particularly as an adjuvant during chemotherapy may be useful in the anticancer treatment, and may also be related to the decline in cancer mortality. Reconstituted HDLs have the ability to release chemotherapeutic drugs inside the cell. As a consequence, this may be a novel way to improve therapeutic targeting for the breast cancer on the basis of detrimental impacts of oxidized HDL on cancer development.

Detection of Lipid and Amphiphilic Biomarkers for Disease Diagnostics

Rapid diagnosis is crucial to effectively treating any disease. Biological markers, or biomarkers, have been widely used to diagnose a variety of infectious and non-infectious diseases. The detection of biomarkers in patient samples can also provide valuable information regarding progression and prognosis. Interestingly, many such biomarkers are composed of lipids, and are amphiphilic in biochemistry, which leads them to be often sequestered by host carriers. Such sequestration enhances the difficulty of developing sensitive and accurate sensors for these targets. Many of the physiologically relevant molecules involved in pathogenesis and disease are indeed amphiphilic. This chemical property is likely essential for their biological function, but also makes them challenging to detect and quantify in vitro. In order to understand pathogenesis and disease progression while developing effective diagnostics, it is important to account for the biochemistry of lipid and amphiphilic biomarkers when creating novel techniques for the quantitative measurement of these targets. Here, we review techniques and methods used to detect lipid and amphiphilic biomarkers associated with disease, as well as their feasibility for use as diagnostic targets, highlighting the significance of their biochemical properties in the design and execution of laboratory and diagnostic strategies. The biochemistry of biological molecules is clearly relevant to their physiological function, and calling out the need for consideration of this feature in their study, and use as vaccine, diagnostic and therapeutic targets is the overarching motivation for this review.

27-hydroxycholesterol: A novel player in molecular carcinogenesis of breast and prostate cancer

Several studies have suggested an etiological role for hypercholesterolemia in the pathogenesis of breast cancer and prostate cancer (PCa). However, the molecular mechanisms that underlie and mediate the hypercholesterolemia-fostered increased risk for breast cancer and PCa are yet to be determined. The discovery that the most abundant cholesterol oxidized metabolite in the plasma, 27 hydroxycholesterol (27-OHC), is a selective estrogen receptor modulator (SERM) and an agonist of Liver X receptors (LXR) partially fills the void in our understanding and knowledge of the mechanisms that may link hypercholesterolemia to development and progression of breast cancer and PCa. The wide spectrum and repertoire of SERM and LXR-dependent effects of 27-OHC in the context of all facets and aspects of breast cancer and prostate cancer biology are reviewed in this manuscript in a very comprehensive manner. This review highlights recent findings pertaining to the role of 27-OHC in breast cancer and PCa and delineates the signaling mechanisms involved in the governing of different facets of tumor biology, that include tumor cell proliferation, epithelial-mesenchymal transition (EMT), as well as tumor cell invasion, migration, and metastasis. We also discuss the limitations of contemporary studies and lack of our comprehension of the entire gamut of effects exerted by 27-OHC that may be relevant to the pathogenesis of breast cancer and PCa. We unveil and propose potential future directions of research that may further our understanding of the role of 27-OHC in breast cancer and PCa and help design therapeutic interventions against endocrine therapy-resistant breast cancer and PCa.

Long-term allopurinol use decreases the risk of prostate cancer in patients with gout: a population-based study

BACKGROUND

Clinical observations indicated an increased risk of developing prostate cancer in gout patients. Chronic inflammation is postulated to be one crucial mechanism for prostate carcinogenesis. Allopurinol, a widely used antigout agent, possesses potent anti-inflammation capacity. We elucidated whether allopurinol decreases the risk of prostate cancer in gout patients.

METHODS

We analyzed data retrieved from Taiwan National Health Insurance Database between January 2000 and December 2012. Patients diagnosed with gout during the study period with no history of prostate cancer and who had never used allopurinol were selected. Four allopurinol use cohorts (that is, allopurinol use (>365 days), allopurinol use (181-365 days), allopurinol use (91-180 days) and allopurinol use (31-90 days)) and one cohort without using allopurinol (that is, allopurinol use (No)) were included. The study end point was the diagnosis of new-onset prostate cancer. Multivariable Cox proportional hazards regression and propensity score-adjusted Cox regression models were used to estimate the association between the risk of prostate cancer and allopurinol treatment in gout patients after adjusting for potential confounders.

RESULTS

A total of 25 770 gout patients (aged between 40 and 100 years) were included. Multivariable Cox regression analyses revealed that the risk of developing prostate cancer in the allopurinol use (>365 days) cohort was significantly lower than the allopurinol use (No) cohort (adjusted hazard ratio (HR)=0.64, 95% confidence interval (CI)=0.45-0.9, P=0.011). After propensity score adjustment, the trend remained the same (adjusted HR=0.66, 95% CI=0.46-0.93, P=0.019).

CONCLUSIONS

Long-term (more than 1 year) allopurinol use may associate with a decreased risk of prostate cancer in gout patients.

The current evidence on statin use and prostate cancer prevention: are we there yet?

An increasing amount of data supports an inverse association between statin use and cancer risk. The findings for prostate cancer, particularly advanced disease, are the most promising of all cancers studied. Use of these agents seems to also be associated with improved prostate- cancer-specific survival, particularly in men undergoing radiotherapy, suggesting usefulness of statins in secondary and tertiary prevention. Some study results might be influenced by increased PSA screening and health-conscious behaviour in statin users but these factors are unlikely to completely account for observed beneficial effects. The epidemiological evidence is supported by preclinical studies that show that statins directly inhibit prostate cancer development and progression in cell-based and animal-based models. The antineoplastic effect of statins might arise from a number of cholesterol-mediated and non-cholesterol-mediated mechanisms that affect pathways essential for cancer formation and progression. Understanding these mechanisms is instrumental in drug discovery research for the development of future prostate cancer therapeutics, as well as in designing clinical trials to test a role for statins in prostate cancer prevention. Currently, sufficient data are lacking to support the use of statins for the primary prevention of prostate cancer and further research is clearly warranted. Secondary and tertiary prevention trials in men who have been diagnosed with prostate cancer might soon be performed.

Cyp3a deficiency enhances androgen receptor activity and cholesterol synthesis in the mouse prostate

Testosterone regulates cellular functions in the prostate through activation of the androgen receptor (AR), which may enhance expression levels of cholesterogenic enzymes through activation of sterol regulatory element-binding protein2 (SREBP2). Because testosterone is inactivated to 6β-hydroxytestosterone by cytochrome P450 3A (CYP3A), we examined the effects of Cyp3a deficiency on circulating testosterone levels and its effects on activation of the AR and expression levels of cholesterogenic enzymes in the prostate using Cyp3a-knockout (Cyp3a(-/-)) mice. The results showed that Cyp3a(-/-) mice had remarkably increased free testosterone levels in plasma along with suppressed testosterone 6β-hydroxylation activities in liver microsomes, suggesting that Cyp3a is a major determinant of systemic levels of testosterone in mice. The results also showed that mRNA expression levels of the AR target genes were increased significantly, and that AR bindings to the promoter region of the AR target genes were more abundant in the prostates of Cyp3a(-/-) mice. These findings suggest that AR activation was stimulated in the prostate of Cyp3a(-/-) mice. In addition, the protein expression levels of SREBP cleavage-activating protein (SCAP), mRNA expression levels of SREBP2 target genes and total cholesterol contents were increased in the prostates of Cyp3a(-/-) mice. The findings suggest that Cyp3a deficiency stimulated the expression of Scap via activation of the AR, which elevated cholesterogenic gene expression levels through activation of SREBP2 and increased total cholesterol contents in the prostate.

Cholesterol and prostate cancer risk: a long-term prospective cohort study

BACKGROUND

Few studies have taken risk of competing events into account when examining the relationship between cholesterol and prostate cancer incidence, and few studies have a follow-up over several decades. We aimed to use these approaches to examine the relationship between cholesterol and prostate cancer.

METHODS

A cohort of 1997 healthy Norwegian men aged 40-59 years in 1972-75 was followed throughout 2012. Cancer data were extracted from the Cancer Registry of Norway. The association between cholesterol and prostate cancer incidence was assessed using competing risk regression analysis, with adjustment for potential confounders. Date and cause of death was obtained from the Cause of Death Registry of Norway.

RESULTS

The study cohort had a cancer risk similar to the general Norwegian population. Prostate cancer was registered in 213 men (11 %), including 62 (3 %) with advanced stage at diagnosis. For overall and advanced stage prostate cancer, the incidence was twice as high in the lowest quartile of cholesterol compared to the highest quartile. These associations remained significant after adjustment for age, smoking, physical fitness, BMI, and systolic blood pressure. Furthermore, high physical fitness and low BMI were associated with increased prostate cancer incidence. Sensitivity analyses excluding events during the first 20 years of observation revealed similar results.

CONCLUSION

Low cholesterol, as well as high physical fitness and low BMI, may be associated with increased risk of prostate cancer. These findings conflict with current prostate cancer prevention recommendations.

Heart healthy equals prostate healthy and statins, aspirin, and/or metformin (S.A.M.) are the ideal recommendations for prostate cancer prevention

Cardiovascular disease (CVD) has been the number one cause of death in the U.S. for 114 of the last 115 years. Lifestyle factors that promote CVD also appear to increase prostate cancer risk and those that reduce CVD risk also appear to reduce the risk of prostate cancer. The largest randomized trials utilizing dietary supplements or pharmacologic agents for prostate cancer prevention (Selenium and Vitamin E Cancer Prevention Trial [SELECT]) have also shed light on the problems and future solutions in this area. Dietary supplements that have not been found to be CVD protective, such as selenium and Vitamin E have not been found to be prostate protective. In addition, over exposure to specific anti-oxidants in nutritionally replete populations may be encouraging cancer growth. Future trials of dietary supplements to prevent prostate cancer could be problematic because by the time a definitive trial is initiated the participants will no longer be “deficient” in the nutrient being tested, which arguably occurred in the SELECT trial. It is also interesting that statins, aspirin, and/or metformin (S.A.M.) are 3 generic, low-cost, heart healthy agents derived from natural sources with separate mechanism of actions, which all appear to have the best benefit to risk ratio compared to any other agent available for prostate cancer prevention, especially aggressive disease, or as an ancillary agent (s) to conventional cancer treatment. It is time to focus on the forest over the trees and recommend proven CVD protective measures for men concerned about their risk of prostate cancer.

Association between preoperative serum total cholesterol level and biochemical recurrence in prostate cancer patients who underwent radical prostatectomy

The aim of this study was to investigate the association between serum total cholesterol (TC) level and biochemical recurrence (BCR) following radical prostatectomy (RP). The study included 562 patients with T1-3N0M0 prostate cancer, who underwent RP at our institution between 2002 and 2010. No patients received neoadjuvant and/or adjuvant therapy. The associations between preoperative TC level, clinicopathological factors and BCR were assessed using univariate and multivariate analyses. During follow-up (mean, 54.0 months), 168 patients (168/562, 29.9%) experienced BCR, with a 5-year BCR-free rate of 67.2%. Of the clinicopathological characteristics investigated, statin use and lymphovascular invasion (LVI) status were associated with lower TC level (P=0.003 and P=0.014, respectively). In the univariate analysis, a higher serum prostate-specific antigen (PSA) level at diagnosis, extracapsular extension, positive surgical margin, seminal vesicle invasion, LVI, perineural invasion, higher Gleason score (GS ≥8) based on the RP specimen, increased body mass index, and low preoperative TC level, were significantly associated with BCR. In the multivariate analysis, the TC level was an independent predictor of BCR (hazard ratio = 0.925 per 10 mg/dl; 95% confidence interval: 0.879-0.973; P=0.003), as was the serum PSA level, extracapsular extension, positive surgical margin and the GS. Low preoperative serum TC levels were associated with an increased risk of BCR among prostate cancer patients who underwent RP. Our findings suggest that the preoperative serum TC level may provide important clinical information that may prove to be useful in patient counseling.

Serum lipid profiles: novel biomarkers predicting advanced prostate cancer in patients receiving radical prostatectomy

This study aimed to evaluate the role of serum lipid profiles as novel biomarkers in predicting pathological characteristics of prostate cancer (PCa). We retrospectively analyzed 322 consecutive patients with clinically localized PCa receiving radical prostatectomy (RP) and extended pelvic lymphadenectomy. Unconditional logistic regression was used to estimate the prostatectomy Gleason score (pGS), pathological stage and lymph node involvement (LNI) in RP specimens. Preoperative prostate-specific antigen (PSA) levels, biopsy GS (bGS), and preoperative tumor, node, metastasis staging were used as basic variables to predict postoperative pathological characteristics. Preoperative serum lipid profiles were introduced as potential predictors. A receiver operating characteristic (ROC) curve was used to determine predictive efficacy. Significant differences in pathological characteristics were observed among patients with normal and abnormal total cholesterol (TC), triglyceride (TG), and low-density lipoprotein (LDL) levels, with the exception of pGS in the TG group. Multivariable regression analysis revealed that the odds ratio for high levels of TC for LNI compared with normal TC levels was 6.386 (95% confidence interval [CI] 1.510–27.010), 3.270 (95% CI: 1.470–7.278) for high levels of TG for pT3–4 disease, and 2.670 (95% CI: 1.134–6.287) for high levels of LDL for pGS. The area under the ROC curve of the models with dyslipidemia was larger than that in models without dyslipidemia, in predicting pathological characteristics. Abnormal TC, TG, and LDL levels are significantly associated with postoperative pathological status in PCa patients. Together with preoperative PSA levels, bGS, and clinical stage, dyslipidemia is more accurate in predicting pathological characteristics.

Metabolic syndrome and prostate cancer risk in a population-based case-control study in Montreal, Canada

Background

The role of metabolic syndrome (MetS) in prostate cancer risk is still debated. We investigated it in a large population-based case–control study.

Methods

Cases were 1937 men with incident prostate cancer, aged ≤75 years, diagnosed across French hospitals in the Montreal area between 2005 and 2009. Concurrently, 1995 population controls from the same residential area and age distribution were randomly selected from electoral list of French-speaking men. Detailed lifestyle and medical histories, and anthropometric measures, were collected during in-person interviews. Prevalence of MetS components (type 2 diabetes, high blood pressure, dyslipidemia and abdominal obesity) was estimated at 2 years before diagnosis for cases/ interview for controls, and at ages 20, 40, 50 and 60. Logistic regression was used to estimate odds ratios (OR) and 95 % confidence intervals for the association between MetS and prostate cancer risk.

Results

A history of MetS (≥3 components vs <3) was associated with a reduced risk of prostate cancer (OR = 0.70 [0.60, 0.82]) after considering potential confounders. The negative association was particularly pronounced with a young age (≤40 years) at MetS onset (OR = 0.38 [0.16-0.89]), did not vary according to prostate cancer aggressiveness, and was only partly explained by the presence of type 2 diabetes. A risk decrease was observed with the number of MetS components, suggesting a synergistic interaction of the components.

Discussion

The observed negative association, consistent with results from other North American populations undergoing regular prostate cancer screening, underlines the importance of considering PSA-testing when studying the MetS-prostate cancer association.

Conclusions

Findings from this study are consistent with an inverse association between MetS and prostate cancer risk.

Cholesterol Levels in Blood and the Risk of Prostate Cancer: A Meta-analysis of 14 Prospective Studies

BACKGROUND

As a neutral lipid and prominent component of the Western diet, cholesterol levels might be a risk factor for prostate cancer. However, current evidence has been inconsistent. This meta-analysis aimed to evaluate the association between blood cholesterol levels and the risk of prostate cancer.

METHODS

An extensive search was performed in MEDLINE and EMBASE for prospective studies that have reported the association between total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL) levels in blood and risk of prostate cancer. Random-effects models were used to summarize the study-specific results.

RESULTS

Fourteen studies were included in this meta-analysis. In the meta-analysis, the summarized risk ratios (RR) for the highest to lowest cholesterol levels were as follows: 1.05 [95% confidence interval (CI), 0.97-1.14; P = 0.21] for TC, 0.93 (95% CI, 0.80-1.10; P = 0.40) for HDL, and 1.17 (95% CI, 0.88-1.55; P = 0.51) for LDL. When restricting to high-grade prostate cancer, the pooled RR was 1.32 (95% CI, 0.93-1.87; P = 0.13) for TC. In dose-response analyses, a 1 mmol/L increment in blood TC, HDL, and LDL level conferred an RR of 1.01 (95% CI, 0.99-1.02; P = 0.38), 0.98 (95% CI, 0.91-1.07; P = 0.72), and 1.04 (95% CI, 0.98-1.10; P = 0.24), respectively.

CONCLUSION

In this meta-analysis of 14 large prospective studies, blood TC, HDL, and LDL levels were not associated with the risk of either overall prostate cancer or high-grade prostate cancer.

IMPACT

Our findings did not appear to support the hypothesis that hypercholesterolemia increases the risk of prostate cancer.

Uncoupling nuclear receptor LXR and cholesterol metabolism in cancer

Liver X receptors (LXRs) are members of the nuclear receptor superfamily of DNA-binding transcription factors and act as sensors of cholesterol homeostasis. Under normal conditions, when intracellular cholesterol concentration increases, cells synthesize oxysterols and activate the LXR transcriptional network to drive cholesterol efflux and reduce cholesterol influx and synthesis. During normal and cancer cell proliferation, there is a net uncoupling between intracellular cholesterol increase and LXR activation resulting from the reduced intracellular oxysterol concentration. This review dissects the novel mechanisms of a previously unrecognized metabolic uncoupling, supporting the activation of the LXR axis as a bona fide therapeutic approach in cancer.

Hypertriglyceridemia is a potential preoperative predictor for biochemical recurrence after radical prostatectomy

Objectives

Many previous studies have suggested that the outcome of prostate cancer (PCa) may be closely related to abnormal lipid metabolism. Therefore, in this study, we evaluated the preoperative lipid profiles of patients with clinically localized prostate cancer (PCa) who underwent radical prostatectomy (RP), with particular emphasis on the relationship between these profiles and biochemical recurrence (BCR).

Patients and Methods

We evaluated 715 consecutive men with clinically localized PCa who underwent RP at our institution between January 2011 and December 2013. We defined hypertriglyceridemia as a fasting serum triglyceride (TG) level greater than 200 mg/dL. We used the Kaplan—Meier method to predict BCR-free survival and applied the log-rank test to determine the statistical significance between survival curves. Cox proportional hazard ratio (HR) models were used to identify the significant predictors of BCR according to clinicopathological variables.

Results

Of 663 patients who underwent RP for clinically localized PCa, 66 (10.0%) showed BCR during a median follow-up period of 21 months. Patients without BCR had higher levels of serum TG, and patients with hypertriglyceridemia were significantly more likely to achieve BCR-free survival in the Kaplan—Meier analysis (log-rank test, P = 0.009). In the multivariable analysis, the presence of hypertriglyceridemia (HR 0.22), pathologic Gleason score (≥8; HR 2.85), pathologic T stage (≥pT3; HR 3.44), and a positive surgical margin (HR, 2.39) were still significant BCR predictors.

Conclusions

We found that preoperative hypertriglyceridemia was associated with a lower risk of BCR after RP in patients with clinically localized PCa. Our results could help to clarify the currently conflicting evidence on the relationship between serum lipid profiles, particularly the presence of hypertriglyceridemia, and the risk of BCR in PC a patients after surgery.

Synthetic high-density lipoprotein-like nanoparticles as cancer therapy

High-density lipoproteins (HDL) are diverse natural nanoparticles that carry cholesterol and are best known for the role that they play in cardiovascular disease. However, due to their unique targeting capabilities, diverse molecular cargo, and natural functions beyond cholesterol transport, it is becoming increasingly appreciated that HDLs are critical to cancer development and progression. Accordingly, this chapter highlights ongoing research focused on the connections between HDL and cancer in order to design new drugs and targeted drug delivery vehicles. Research is focused on synthesizing biomimetic HDL-like nanoparticles (NP) that can be loaded with diverse therapeutic cargo (e.g., chemotherapies, nucleic acids, proteins) and specifically targeted to cancer cells. Beyond drug delivery, new data is emerging that HDL-like NPs may be therapeutically active in certain tumor types, for example, B cell lymphoma. Overall, HDL-like NPs are becoming increasingly appreciated as targeted, biocompatible, and efficient therapies for cancer, and may soon become indispensable agents in the cancer therapeutic armamentarium.

Metabolic syndrome in the development and progression of prostate cancer

Prostate cancer (PCa) is the most common noncutaneous malignancy and second leading cause of cancer-specific mortality for men in the United States. There is a wide spectrum of aggressiveness ranging from biologically significant to indolent disease, which has led to an interest in the identification of risk factors for its development and progression. Emerging evidence has suggested an association between metabolic syndrome (MetS) and PCa. MetS represents a cluster of metabolic derangements that confer an increased risk of cardiovascular disease and type 2 diabetes mellitus. Its individual components include obesity, dyslipidemias, high blood pressure, and high fasting glucose levels. MetS has become pervasive and is currently associated with a high socioeconomic cost in both industrialized and developing countries throughout the world. The relationship between MetS and PCa is complex and yet to be fully defined. A better understanding of this relationship will facilitate the development of novel therapeutic targets for the prevention of PCa and improvement of outcomes among diagnosed men in the future. In this review, we evaluate the current evidence on the role of MetS in the development and progression of PCa. We also discuss the clinical implications on the management of PCa and consider the future direction of this subject.

Statins in oncological research: from experimental studies to clinical practice

Statins, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors are commonly used drugs in the treatment of dyslipidemias, primarily raised cholesterol. Recently, many epidemiological and preclinical studies pointed to anti-tumor properties of statins, including anti-proliferative activities, apoptosis, decreased angiogenesis and metastasis. These processes play an important role in carcinogenesis and, therefore, the role of statins in cancer disease is being seriously discussed among oncologists. Anti-neoplastic properties of statins combined with an acceptable toxicity profile in the majority of individuals support their further development as anti-tumor drugs. The mechanism of action, current preclinical studies and clinical efficacy of statins are reviewed in this paper. Moreover, promising results have been reported regarding the statins' efficacy in some cancer types, especially in esophageal and colorectal cancers, and hepatocellular carcinoma. Statins' hepatotoxicity has traditionally represented an obstacle to the prescription of this class of drugs and this issue is also discussed in this review.

Effects of Marine Phospholipids Extract on the Lipid Levels of Metastatic and Nonmetastatic Prostate Cancer Patients

High intake of omega-3 fatty acids (n-3 FAs) from fish has shown to reduce metastatic progression of prostate cancer. This clinical trial investigated the influence of high n-3 FA intake (marine phospholipids, MPL) on the FA composition of blood lipids, lysophosphatidylcholine (LPC), and on lipoproteins in prostate cancer patients and elderly men without prostate cancer. MPL supplementation resulted in a significant increase of n-3 FAs (eicosapentaenoic and docosahexaenoic acid) in blood lipids, while arachidonic acid (n-6 FA) decreased significantly. Low density lipoprotein (LDL) and high density lipoprotein (HDL) increased significantly, but the LDL increase was observed only in subjects with an inactive tumour. Similarly, LPC plasma concentration increased significantly only in patients without tumour. The missing increase of LDL and LPC after MPL supplementation in patients with actively growing (metastasizing) prostate cancer suggests that tumour cells have an elevated demand for LDL and LPC. Due to the MPL-induced increase of n-3 FAs in these blood lipids, it can be assumed that especially actively growing and metastasizing prostate cancer cells are provided with elevated amounts of these antimetastatic n-3 FAs. A hypothetic model explaining the lower incidence of metastatic progression in prostate cancer patients with high fish consumption is presented.

Shared common variants in prostate cancer and blood lipids

BACKGROUND

Epidemiological and clinical studies suggest comorbidity between prostate cancer (PCA) and cardiovascular disease (CVD) risk factors. However, the relationship between these two phenotypes is still not well understood. Here we sought to identify shared genetic loci between PCA and CVD risk factors.

METHODS

We applied a genetic epidemiology method based on conjunction false discovery rate (FDR) that combines summary statistics from different genome-wide association studies (GWAS), and allows identification of genetic overlap between two phenotypes. We evaluated summary statistics from large, multi-centre GWA studies of PCA (n=50 000) and CVD risk factors (n=200 000) [triglycerides (TG), low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol, systolic blood pressure, body mass index, waist-hip ratio and type 2 diabetes (T2D)]. Enrichment of single nucleotide polymorphisms (SNPs) associated with PCA and CVD risk factors was assessed with conditional quantile-quantile plots and the Anderson-Darling test. Moreover, we pinpointed shared loci using conjunction FDR.

RESULTS

We found the strongest enrichment of P-values in PCA was conditional on LDL and conditional on TG. In contrast, we found only weak enrichment conditional on HDL or conditional on the other traits investigated. Conjunction FDR identified altogether 17 loci; 10 loci were associated with PCA and LDL, 3 loci were associated with PCA and TG and additionally 4 loci were associated with PCA, LDL and TG jointly (conjunction FDR <0.01). For T2D, we detected one locus adjacent to HNF1B.

CONCLUSIONS

We found polygenic overlap between PCA predisposition and blood lipids, in particular LDL and TG, and identified 17 pleiotropic gene loci between PCA and LDL, and PCA and TG, respectively. These findings provide novel pathobiological insights and may have implications for trials using targeting lipid-lowering agents in a prevention or cancer setting.

Cholesterol-induced activation of TRPM7 regulates cell proliferation, migration, and viability of human prostate cells

Cholesterol has been shown to promote cell proliferation/migration in many cells; however the mechanism(s) have not yet been fully identified. Here we demonstrate that cholesterol increases Ca(2+) entry via the TRPM7 channel, which promoted proliferation of prostate cells by inducing the activation of the AKT and/or the ERK pathway. Additionally, cholesterol mediated Ca(2+) entry induced calpain activity that showed a decrease in E-cadherin expression, which together could lead to migration of prostate cancer cells. An overexpression of TRPM7 significantly facilitated cholesterol dependent Ca(2+) entry, cell proliferation and tumor growth. Whereas, TRPM7 silencing or inhibition of cholesterol synthesis by statin showed a significant decrease in cholesterol-mediated activation of TRPM7, cell proliferation, and migration of prostate cancer cells. Consistent with these results, statin intake was inversely correlated with prostate cancer patients and increase in TRPM7 expression was observed in samples obtained from prostate cancer patients. Altogether, we provide evidence that cholesterol-mediated activation of TRPM7 is important for prostate cancer and have identified that TRPM7 could be essential for initiation and/or progression of prostate cancer.

Statin use and the risk of recurrence after radical prostatectomy in a cohort of men with inherited and/or early-onset forms of prostate cancer

OBJECTIVE

To investigate whether the use of statin medications is associated with a reduced risk of biochemical recurrence (BCR) in men with inherited and/or early-onset prostate cancer who have been treated with radical retropubic prostatectomy (RRP).

METHODS

Study patients are men with inherited and/or early-onset prostate cancer enrolled in the University of Michigan Prostate Cancer Genetics Project. Men enrolled in Prostate Cancer Genetics Project were surveyed to determine statin medication use history from 1999 to 2009. Diagnosis and treatment data were taken from medical records. BCR was defined as a single increase in prostate-specific antigen level to ≥0.4 ng/mL after treatment with RRP. Statin use was modeled as a time-dependent variable, and BCR after RRP was both examined using crude Cox proportional hazards models and adjusted for known clinical prognostic factors.

RESULTS

A total of 539 men treated with RRP were included in this study. Of these, 47.9% of men used statin medications, and 115 (21%) men experienced a recurrence. Ever-statin use was not associated with risk of recurrence in crude models (hazards ratio=1.04, 95% confidence interval=0.72-1.49, P value=.86) or in models adjusted for clinical characteristics (hazards ratio=1.06, 95% confidence interval=0.68-1.64, P value=.81). Furthermore, no association was observed when comparing men with high-Gleason grade cancers with those with low-Gleason grade cancers.

CONCLUSION

Statin use was not associated with a reduced risk of BCR after RRP in this study; however, these men at increased risk for prostate cancer represent a subgroup of men who may benefit from further study of statin medication use to slow or prevent BCR.

Risk adapted chemoprevention for prostate cancer: an option?

A high disease prevalence, the presentation in older age, a frequently slowly progressing course of disease, and high costs make diagnosis and therapy of prostate cancer a special challenge for urologists. Effective prevention of the disease may help to resolve some of the problems mentioned above. Two randomised, controlled studies prove that effective chemoprevention of prostate cancer is possible using 5-α reductase inhibitors (finasteride, dutasteride) (LoE 1) both in individuals at low and those at high risk developing prostate cancer. Furthermore, there is evidence that other compounds, e.g. selective estrogen receptor modulators (SERMs), non-steroidal anti-inflammatory drugs (NSAIDs) and statins might also be effective. This review investigates potential risks and benefits of chemoprevention including a consideration of health economic aspects. The authors conclude that chemoprevention in a high risk cohort using 5-α reductase inhibitors is a viable option and may even be cost effective. In consequence, the options of chemoprevention in prostate cancer should be further explored in an open and unbiased way.

The role of cholesterol metabolism and cholesterol transport in carcinogenesis: a review of scientific findings, relevant to future cancer therapeutics

While the unique metabolic activities of malignant tissues as potential targets for cancer therapeutics has been the subject of several recent reviews, the role of cholesterol metabolism in this context is yet to be fully explored. Cholesterol is an essential component of mammalian cell membranes as well as a precursor of bile acids and steroid hormones. The hypothesis that cancer cells need excess cholesterol and intermediates of the cholesterol biosynthesis pathway to maintain a high level of proliferation is well accepted, however the mechanisms by which malignant cells and tissues reprogram cholesterol synthesis, uptake and efflux are yet to be fully elucidated as potential therapeutic targets. High and low density plasma lipoproteins are the likely major suppliers of cholesterol to cancer cells and tumors, potentially via receptor mediated mechanisms. This review is primarily focused on the role(s) of lipoproteins in carcinogenesis, and their future roles as drug delivery vehicles for targeted cancer chemotherapy.

The role of signalling in cellular cholesterol homeostasis

Cholesterol is a vital lipid and performs diverse functions on a whole body and cellular level. However, excess cellular cholesterol is toxic, and thus, elegant mechanisms have evolved to tightly regulate this important lipid. The regulation of cholesterol homeostasis is an area of intense research, and the role that signalling plays is gradually becoming more widely recognised. Cholesterol homeostasis is achieved through intricate mechanisms involving synthesis, uptake, and efflux. Although there is a large body of work elucidating these cholesterol-related pathways, less is known about the role of signalling in these processes. Here, we discuss the variety of ways that signalling impacts on these modes and levels of cholesterol homeostasis, including transcriptional regulation. Most work thus far has investigated the role of kinases in cholesterol efflux (especially on ATP-binding cassette transporter A1, ABCA1), and therefore constitutes a major focus of this review. We also indicate further avenues to explore in the area of signalling in cellular cholesterol homeostasis.

Loss of caveolin-1 in prostate cancer stroma correlates with reduced relapse-free survival and is functionally relevant to tumour progression

Levels of caveolin-1 (Cav-1) in tumour epithelial cells increase during prostate cancer progression. Conversely, Cav-1 expression in the stroma can decline in advanced and metastatic prostate cancer. In a large cohort of 724 prostate cancers, we observed significantly decreased levels of stromal Cav-1 in concordance with increased Gleason score (p = 0.012). Importantly, reduced expression of Cav-1 in the stroma correlated with reduced relapse-free survival (p = 0.009), suggesting a role for stromal Cav-1 in inhibiting advanced disease. Silencing of Cav-1 by shRNA in WPMY-1 prostate fibroblasts resulted in up-regulation of Akt phosphorylation, and significantly altered expression of genes involved in angiogenesis, invasion, and metastasis, including a > 2.5-fold increase in TGF-β1 and γ-synuclein (SNCG) gene expression. Moreover, silencing of Cav-1 induced migration of prostate cancer cells when stromal cells were used as attractants. Pharmacological inhibition of Akt caused down-regulation of TGF-β1 and SNCG, suggesting that loss of Cav-1 in the stroma can influence Akt-mediated signalling in the tumour microenvironment. Cav-1-depleted stromal cells exhibited increased levels of intracellular cholesterol, a precursor for androgen biosynthesis, steroidogenic enzymes, and testosterone. These findings suggest that loss of Cav-1 in the tumour microenvironment contributes to the metastatic behaviour of tumour cells by a mechanism that involves up-regulation of TGF-β1 and SNCG through Akt activation. They also suggest that intracrine production of androgens, a process relevant to castration resistance, may occur in the stroma.

Cholesterol accumulation in prostate cancer: a classic observation from a modern perspective

Prostate cancer (PCa) is the most common cancer in men in developed countries. Epidemiological studies have associated high blood-cholesterol levels with an increased risk of PCa, whilst cholesterol-lowering drugs (statins) reduce the risk of advanced PCa. Furthermore, normal prostate epithelial cells have an abnormally high cholesterol content, with cholesterol levels increasing further during progression to PCa. In this review, we explore why and how this occurs. Concurrent to this observation, intense efforts have been expended in cardiovascular research to better understand the regulators of cholesterol homeostasis. Here, we apply this knowledge to elucidate the molecular mechanisms driving the accumulation of cholesterol in PCa. For instance, recent evidence from our group and others shows that major signalling players in prostate growth and differentiation, such as androgens and Akt, modulate the key transcriptional regulators of cholesterol homeostasis to enhance cholesterol levels. This includes adjusting central carbon metabolism to sustain greater lipid synthesis. Perturbations in cholesterol homeostasis appear to be maintained even when PCa approaches the advanced, 'castration-resistant' state. Overall, this provides a link between cholesterol accumulation and PCa cell growth. Given there is currently no cure for castration-resistant PCa, could cholesterol metabolism be a novel target for PCa therapy? Overall, this review presents a picture that cholesterol metabolism is important for PCa development: growth-promoting factors stimulate cholesterol accumulation, which in turn presents a possible target for chemotherapy. Consequently, we recommend future investigations, both to better elucidate the mechanisms driving this accumulation and applying it in novel chemotherapeutic strategies.

Dysregulation of cholesterol homeostasis in human prostate cancer through loss of ABCA1

Recent epidemiologic data show that low serum cholesterol level as well as statin use is associated with a decreased risk of developing aggressive or advanced prostate cancer, suggesting a role for cholesterol in aggressive prostate cancer development. Intracellular cholesterol promotes prostate cancer progression as a substrate for de novo androgen synthesis and through regulation of AKT signaling. By conducting next-generation sequencing-based DNA methylome analysis, we have discovered marked hypermethylation at the promoter of the major cellular cholesterol efflux transporter, ABCA1, in LNCaP prostate cancer cells. ABCA1 promoter hypermethylation renders the promoter unresponsive to transactivation and leads to elevated cholesterol levels in LNCaP. ABCA1 promoter hypermethylation is enriched in intermediate- to high-grade prostate cancers and not detectable in benign prostate. Remarkably, ABCA1 downregulation is evident in all prostate cancers examined, and expression levels are inversely correlated with Gleason grade. Our results suggest that cancer-specific ABCA1 hypermethylation and loss of protein expression direct high intracellular cholesterol levels and hence contribute to an environment conducive to tumor progression.

Statin use and risk of prostate cancer: a meta-analysis of observational studies

BACKGROUND

Emerging evidence suggests that statins may decrease the risk of cancers. However, available evidence on prostate cancer (PCa) is conflicting. We therefore examined the association between statin use and risk of PCa by conducting a detailed meta-analysis of all observational studies published regarding this subject.

METHODS

Literature search in PubMed database was undertaken through February 2012 looking for observational studies evaluating the association between statin use and risk of PCa. Before meta-analysis, the studies were evaluated for publication bias and heterogeneity. Pooled relative risk (RR) estimates and 95% confidence intervals (CIs) were calculated using random-effects model (DerSimonian and Laird method). Subgroup analyses, sensitivity analysis and cumulative meta-analysis were also performed.

RESULTS

A total of 27 (15 cohort and 12 case-control) studies contributed to the analysis. There was heterogeneity among the studies but no publication bias. Statin use significantly reduced the risk of both total PCa by 7% (RR 0.93, 95% CI 0.87-0.99, p = 0.03) and clinically important advanced PCa by 20% (RR 0.80, 95% CI 0.70-0.90, p<0.001). Long-term statin use did not significantly affect the risk of total PCa (RR 0.94, 95% CI 0.84-1.05, p = 0.31). Stratification by study design did not substantially influence the RR. Furthermore, sensitivity analysis confirmed the stability of results. Cumulative meta-analysis showed a change in trend of reporting risk from positive to negative in statin users between 1993 and 2011.

CONCLUSIONS

Our meta-analysis provides evidence supporting the hypothesis that statins reduce the risk of both total PCa and clinically important advanced PCa. Further research is needed to confirm these findings and to identify the underlying biological mechanisms.

Cholesterol and prostate cancer

Prostate cancer risk can be modified by environmental factors, however the molecular mechanisms affecting susceptibility to this disease are not well understood. As a result of a series of recently published studies, the steroidal lipid, cholesterol, has emerged as a clinically relevant therapeutic target in prostate cancer. This review summarizes the findings from human studies as well as animal and cell biology models, which suggest that high circulating cholesterol increases risk of aggressive prostate cancer, while cholesterol lowering strategies may confer protective benefit. Relevant molecular processes that have been experimentally tested and might explain these associations are described. We suggest that these promising results now could be applied prospectively to attempt to lower risk of prostate cancer in select populations.

Cancer, inflammation, and insights from ayurveda

A recent, exciting discovery relates to the concept of "shared pathology" between cancer and metabolic syndrome. One major pathway common to cancer and metabolic syndrome is chronic inflammation, which is a major driving force in carcinogenesis. Indeed, chronic inflammation precedes most cancers and is considered a "hallmark" of the neoplastic process. We discuss molecular and biochemical evidence which links diet, obesity, abnormal lipid metabolism, and type 2 diabetes mellitus with chronic inflammation. We also explain how each of these factors is linked with biochemical aberrations of carcinogenesis and the prevalence and risk of cancer. While there are reliable biomarkers for chronic inflammation, there are few markers for a mechanistic link between early inflammation and digestive disorders. Discovery of such a marker could lead to identification of a new subtype of patients with digestive disorders that predispose them to cancer and/or metabolic syndrome. In this context, we discuss the ayurvedic concept of "Ama" which is thought to be a toxic, proinflammatory waste-product of improper digestion. We then develop hypotheses and outline preclinical and clinical experiments designed to prove whether "Ama" can serve as a novel and reliable biomarker that links abnormal digestive status, with the onset of chronic inflammation.