Statin use and risk of prostate cancer in the prospective Osteoporotic Fractures in Men (MrOS) Study

Overcoming statin resistance in prostate cancer cells by targeting the 3-hydroxy-3-methylglutaryl-CoA-reductase

Prostate cancer is the most prevalent malignancy in men. While diagnostic and therapeutic interventions have substantially improved in recent years, disease relapse, treatment resistance, and metastasis remain significant contributors to prostate cancer-related mortality. Therefore, novel therapeutic approaches are needed. Statins are inhibitors of the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the rate-limiting enzyme of the mevalonate pathway which plays an essential role in cholesterol homeostasis. Numerous preclinical studies have provided evidence for the pleiotropic antitumor effects of statins. However, results from clinical studies remain controversial and have shown substantial benefits to even no effects on human malignancies including prostate cancer. Potential statin resistance mechanisms of tumor cells may account for such discrepancies. In our study, we treated human prostate cancer cell lines (PC3, C4-2B, DU-145, LNCaP) with simvastatin, atorvastatin, and rosuvastatin. PC3 cells demonstrated high statin sensitivity, resulting in a significant loss of vitality and clonogenic potential (up to - 70%; p < 0.001) along with an activation of caspases (up to 4-fold; p < 0.001). In contrast, C4-2B and DU-145 cells were statin-resistant. Statin treatment induced a restorative feedback in statin-resistant C4-2B and DU-145 cells through upregulation of the HMGCR gene and protein expression (up to 3-folds; p < 0.01) and its transcription factor sterol-regulatory element binding protein 2 (SREBP-2). This feedback was absent in PC3 cells. Blocking the feedback using HMGCR-specific small-interfering (si)RNA, the SREBP-2 activation inhibitor dipyridamole or the HMGCR degrader SR12813 abolished statin resistance in C4-2B and DU-145 and induced significant activation of caspases by statin treatment (up to 10-fold; p < 0.001). Consistently, long-term treatment with sublethal concentrations of simvastatin established a stable statin resistance of a PC3SIM subclone accompanied by a significant upregulation of both baseline as well as post-statin HMGCR protein (gene expression up to 70-fold; p < 0.001). Importantly, the statin-resistant phenotype of PC3SIM cells was reversible by HMGCR-specific siRNA and dipyridamole. Our investigations reveal a key role of a restorative feedback driven by the HMGCR/SREBP-2 axis in statin resistance mechanisms of prostate cancer cells.

Targeting lipid metabolism in metastatic prostate cancer

Despite key advances in the treatment of prostate cancer (PCa), a proportion of men have de novo resistance, and all will develop resistance to current therapeutics over time. Aberrant lipid metabolism has long been associated with prostate carcinogenesis and progression, but more recently there has been an explosion of preclinical and clinical data which is informing new clinical trials. This review explores the epidemiological links between obesity and metabolic syndrome and PCa, the evidence for altered circulating lipids in PCa and their potential role as biomarkers, as well as novel therapeutic strategies for targeting lipids in men with PCa, including therapies widely used in cardiovascular disease such as statins, metformin and lifestyle modification, as well as novel targeted agents such as sphingosine kinase inhibitors, DES1 inhibitors and agents targeting FASN and beta oxidation.

Influence of statins in metastatic castration-resistant prostate cancer patients treated with new antiandrogen therapies: a systematic review and meta-analysis

Objective

To evaluate whether the addition of statins to the new antiandrogens (enzalutamide or abiraterone) affects overall survival in patients with metastatic castration-resistant prostate cancer.

Methods

We searched studies in English language including the keywords statins, overall survival, and metastatic castration-resistant prostate cancer, at PubMed^® (MEDLINE^®), Embase and Cochrane databases.

Results

A total of 195 articles were initially identified, but only four met the inclusion criteria and were selected for the meta-analysis. A total of 955 patients, 632 on the new antiandrogens only group, and 323 on the new antiandrogens + statins group, were analyzed. In all four studies the combination therapy (new antiandrogens + statin) was well tolerated, regardless of which new antiandrogens were used. Neither the type of statin nor the doses and duration of use were well specified in the studies. The combination therapy in metastatic castration-resistant prostate cancer was associated with an overall survival improvement, and a 46% reduction in death (hazard ratio of 0.54; 95%CI 0.34-0.87; p<0.01) in multivariate analysis.

Conclusion

There seems to be a clinical benefit with the association of statins to the new antiandrogens in patients with metastatic castration-resistant prostate cancer, suggesting longer overall survival with no important collateral effect. However, due to fragility of the studies available in the literature, we are not yet capable of recommending this combination of drugs in the clinical practice. Further randomized prospective studies are warranted to confirm these beneficial outcomes.

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.

Effect of Statins on the Risk of Different Stages of Prostate Cancer: A Meta-Analysis

INTRODUCTION

The aim of this article was to investigate the relationship between statins and the risk of different stages or grades of prostate cancer.

METHODS

A comprehensive literature search was performed for articles published until December 18, 2020, on the PubMed, Embase, and the Cochrane Library databases. The pooled relative risk (RR) and 95% confidence interval (CI) were then analyzed using the STATA.16.0 software.

RESULTS

A total of 588,055 patients from 14 studies were included in the analysis. We found that the use of statins expressed a significant correlation with a lower risk of advanced prostate cancer (RR = 0.81, 95% CI: 0.73-0.91; RR = 0.86, 95% CI: 0.75-0.99, respectively). However, no evidence suggested that the use of statins was beneficial for the prevention of localized prostate cancer incidence. Similarly, the pooled results also revealed no association between the use of statins and the risk of high-grade and low-grade prostate cancer.

CONCLUSION

It has been found that the use of statins is associated with a lower risk of advanced prostate cancer but was not related to the risk of localized, low-grade, or high-grade prostate cancer.

Simvastatin enhances irinotecan-induced apoptosis in prostate cancer via inhibition of MCL-1

Prostate cancer is one of the most common malignant tumors around the world. Hyperlipidemia is considered as one of the most important risk factors for the development of prostate cancer. Simvastatin is widely used for the treatment of hyperlipidemia and was previously shown to induce apoptosis in several cancer types including lung, colon, pancreas, breast, and prostate cancer. In this study we aimed to explore the potential role of simvastatin in enhancing irinotecan-induced apoptosis in prostate cancer cells. In addition, the underlying molecular mechanisms driving this potential effect of simvastatin were also explored. PC3 cells were treated with simvastatin, irinotecan or combination. Cell viability was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) colorimetric assay. Flow cytometry technique was used to analyze apoptosis and cell cycle progression. Western blot was used for detection of protein expression. Results showed that simvastatin has a significant anti-proliferative activity on PC3 cells. Combined treatment of simvastatin with irinotecan exhibited a significant inhibition of PC3 cell growth compared to each treatment alone. Flow cytometry analysis showed that PC3 cell treatment with simvastatin and irinotecan combination demonstrated a remarkable increase in the percentage of apoptotic cells and those accumulated at G0/G1 phase when compared to each treatment alone. Moreover, induction of apoptosis was caspase-independent. Western blot showed that apoptosis was accompanied by upregulation of GRP-78 level and downregulation of Mcl-1 levels in a time-dependent manner. The results of this study demonstrated that combined treatment of simvastatin with chemotherapeutic agents such as irinotecan resulted in enhancement of growth inhibition and induction of prostate cancer cell apoptosis.

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.

LDL-lowering therapy and the risk of prostate cancer: a meta-analysis of 6 randomized controlled trials and 36 observational studies

The role of statins in preventing prostate cancer is currently a controversial issue. The aim of this review is to investigate the effects of statins use on prostate cancer risk. Electronic databases (the Cochrane Library, PubMed, Medline, Embase, Web of Science, and ClinicalTrials.gov) were searched systematically up to April, 2015. Weighted averages were reported as relative risk (RR) with 95% confidence intervals (CIs). Statistic heterogeneity scores were assessed with the standard Cochran’s Q test and I² statistic. The pooled estimates of randomized controlled trials (RCTs) and retrospective studies suggest that statins have a neutral effect on total prostate cancer (RR = 1·02, 95% CI: 0·90–1·14; and RR = 0·91, 95% CI: 0·79–1·02, respectively). This research provides no evidence to suggest that the use of statins for cholesterol lowering is beneficial for the prevention of low-grade or localized prostate cancer, although a plausible association between statins use and the reduction risk of advanced (RR = 0·87, 95% CI: 0·82–0·91) or high-grade prostate cancer (RR = 0·83, 95% CI: 0·66–0·99) is observed. Furthermore, it shows that prostate cancer risk does not statistically significant benefit from long-term statins use.

A review of statin use and prostate cancer

Prostate cancer is the second most common cause of cancer and, when it metastasizes, has a high mortality rate. Statins may affect prostate cancer progression through cholesterol- and pleiotropic-mediated effects. The data on statin effects on prostate cancer has been mixed with benefit most likely occurring in reducing prostate cancer recurrence after radiation therapy and reduced mortality due to prostate cancer. More research is needed in this area to better characterize potential statin-mediated mechanisms that affect cancer. Also, future studies should report patients' anatomic/prognostic stage based on the updated staging system of the American Joint Committee on Cancer, which is a more effective predictor of recurrence and mortality than anatomic stage alone.

Statins: protectors or pretenders in prostate cancer?

The role of statin therapy in prostate cancer (PCa) prevention and treatment is plagued by controversy. This critical review of published clinical series reveals several caveats in earlier studies, which reported no benefit. Recent studies that adjust for confounding factors have demonstrated statin therapy to be associated with PCa prevention and favorable clinical outcomes. Developed as inhibitors of cholesterol synthesis, the expected mechanism of statin action is systemic cholesterol reduction. By lowering circulating cholesterol, statins indirectly reduce cellular cholesterol levels in multiple cell types, impacting on membrane microdomains and steroidogenesis. Although non-cholesterol mechanisms of statin action have been proposed, they are limited by the uncertainties surrounding in vivo tissue statin concentrations.