Statins are logical candidates for overcoming limitations of targeting therapies on malignancy: their potential application to gastrointestinal cancers

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.

Lovastatin Inhibits RhoA to Suppress Canonical Wnt/β-Catenin Signaling and Alternative Wnt-YAP/TAZ Signaling in Colon Cancer

Statins are first-line drugs used to control patient lipid levels, but there is recent evidence that statin treatment can lower colorectal cancer (CRC) incidence by 50% and prolong CRC patient survival through mechanisms that are poorly understood. In this study, we found that the treatment of APCmin mice by the mevalonate pathway inhibitor lovastatin significantly reduced the number of colonic masses and improved hypersplenism and peripheral anemia. Furthermore, reverse transcription polymerase chain reaction (RT-PCR) analysis of colonic mass tissues showed a potent inhibitory effect in both Wnt/β-catenin signaling and YAP/TAZ signaling in the lovastatin treatment group. The results of our transcriptomic analyses in RKO indicated that lovastatin regulated several proliferation-related signaling pathways. Moreover, lovastatin suppressed important genes and proteins related to the canonical Wnt/β-catenin and alternative Wnt-YAP/TAZ signaling pathways in RKO and SW480 cells, and these effects were rescued by mevalonic acid (MVA), as confirmed through a series of Western blotting, RT-PCR, and reporter assays. Given that statins suppress oncogenic processes primarily through the inhibition of Rho GTPase in the mevalonate pathway, we speculate that lovastatin can inhibit certain Rho GTPases to suppress both canonical Wnt/β-catenin signaling and alternative Wnt-YAP/TAZ signaling. In RKO cells, lovastatin showed similar inhibitory properties as the RhoA inhibitor CCG1423, being able to inhibit β-catenin, TAZ, and p-LATS1 protein activity. Our results revealed that lovastatin inhibited RhoA activity, thereby suppressing the downstream canonical Wnt/β-catenin and alternative Wnt-YAP/TAZ pathways in colon cancer cells. These inhibitory properties suggest the promise of statins as a treatment for CRC. Altogether, the present findings support the potential clinical use of statins in non-cardiovascular contexts and highlight novel targets for anticancer treatments.

Statin and Cancer Mortality and Survival: An Umbrella Systematic Review and Meta-Analysis

The aim of this study is to provide an overview and understand the strength of evidence and the extent of potential biases and the validity of claimed associations between the use of statins and cancer mortality or survival. We performed a comprehensive umbrella review of meta-analyses and systematically appraised the relevant meta-analyses of observational studies on the associations between statin use and cancer mortality or survival in various kinds of cancer. We searched the PubMed database and screened the reference list of relevant articles. We obtained the summary effect, 95% confidence interval, heterogeneity, and also examined small study effects and 95% prediction intervals for effect sizes, and the level of evidence was determined from the criteria. Regarding cancer mortality, statin use showed convincing evidence for an association with a reduced cancer-specific mortality rate for colorectal cancer. Four associations with reduced all-cause mortality (for breast cancer, colorectal cancer, endocrine-related gynecological cancer, and ovarian cancer) had a suggestive evidence. Moreover, analyses in nine cancers showed a weak level of evidence, while the remaining 15 did not indicate significant changes in either direction. Although there was a preventive effect of statin on cancer mortality in some cancer types, the evidence supporting the use of statins to reduce cancer mortality or survival was low.

Lovastatin-mediated MCF-7 cancer cell death involves LKB1-AMPK-p38MAPK-p53-survivin signalling cascade

There is increasing evidence that statins, which are widely used in lowering serum cholesterol and the incidence of cardiovascular diseases, also exhibits anti‐tumour properties. The underlying mechanisms by which statins‐induced cancer cell death, however, remain incompletely understood. In this study, we explored the anti‐tumour mechanisms of a lipophilic statin, lovastatin, in MCF‐7 breast cancer cells. Lovastatin inhibited cell proliferation and induced cell apoptosis. Lovastatin caused p21 elevation while reduced cyclin D1 and survivin levels. Lovastatin also increased p53 phosphorylation, acetylation and its reporter activities. Results from chromatin immunoprecipitation analysis showed that p53 binding to the survivin promoter region was increased, while Sp1 binding to the region was decreased, in MCF‐7 cells after lovastatin exposure. These actions were associated with liver kinase B1 (LKB1), AMP‐activated protein kinase (AMPK) and p38 mitogen‐activated protein kinase (p38MAPK) activation. Lovastatin's enhancing effects on p53 activation, p21 elevation and survivin reduction were significantly reduced in the presence of p38MAPK signalling inhibitor. Furthermore, LKB1‐AMPK signalling blockade abrogated lovastatin‐induced p38MAPK and p53 phosphorylation. Together these results suggest that lovastatin may activate LKB1‐AMPK‐p38MAPK‐p53‐survivin cascade to cause MCF‐7 cell death. The present study establishes, at least in part, the signalling cascade by which lovastatin induces breast cancer cell death.

Drug repurposing to overcome resistance to various therapies for colorectal cancer

Emergence of novel treatment modalities provides effective therapeutic options, apart from conventional cytotoxic chemotherapy, to fight against colorectal cancer. Unfortunately, drug resistance remains a huge challenge in clinics, leading to invariable occurrence of disease progression after treatment initiation. While novel drug development is unfavorable in terms of time frame and costs, drug repurposing is one of the promising strategies to combat resistance. This approach refers to the application of clinically available drugs to treat a different disease. With the well-established safety profile and optimal dosing of these approved drugs, their combination with current cancer therapy is suggested to provide an economical, safe and efficacious approach to overcome drug resistance and prolong patient survival. Here, we review both preclinical and clinical efficacy, as well as cellular mechanisms, of some extensively studied repurposed drugs, including non-steroidal anti-inflammatory drugs, statins, metformin, chloroquine, disulfiram, niclosamide, zoledronic acid and angiotensin receptor blockers. The three major treatment modalities in the management of colorectal cancer, namely classical cytotoxic chemotherapy, molecular targeted therapy and immunotherapy, are covered in this review.

Statin uses and mortality in colorectal cancer patients: An updated systematic review and meta-analysis

BACKGROUND

Colorectal cancer (CRC) remains one of the most common types of cancer and a leading cause of death worldwide. Previous studies indicated that statins may have a potential protective effect on CRC.

METHODS

We conducted this meta-analysis to systematically assess the overall and cancer-specific survival benefit of statin uses on CRC patients. Related references were identified through PubMed, the Cochrane Library, Web of Science, EMBASE, and SCOPUS from inception to August 2017. Adjusted hazard ratios (HRs) were adopted to calculate summary hazard ratios (HRs) with 95% confidence intervals (95% CIs), using a random-effects model.

RESULTS

Total fourteen studies involving 130 994 patients were included in this meta-analysis. Six studies reported the association between pre-diagnosis statin uses and CRC mortality, while 11 studies investigated mortality in patients using statins after CRC diagnosis. For pre-diagnosis statin uses, the pooled HR of all-cause mortality (ACM) was 0.85 (95% CI, 0.79-0.92) and the pooled HR of cancer-specific mortality (CSM) was 0.82 (95% CI, 0.79-0.86). In terms of post-diagnosis statin uses, the pooled HR of ACM was 0.86 (95% CI, 0.76-0.98), and the pooled HR of CSM was 0.79 (95% CI, 0.70-0.89). For post-diagnosis statin uses, there is no difference in ACM when stratified by KRAS gene (KRAS) mutation status. Results of ACM and CSM did not markedly alter in other subgroup analyses.

CONCLUSION

Our meta-analysis demonstrates that both pre-diagnosis and post-diagnosis statin uses are associated with reduced ACM and CSM for CRC patients.

Effect of survivin downregulation by simvastatin on the growth and invasion of salivary adenoid cystic carcinoma

Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, is been used in the clinic due to its pleiotropic effects, such as breast cancer, prostate cancer, pancreatic cancer. Simvastatin has recently been demonstrated to serve a potential role in the prophylaxis and therapeutics of a number of human cancers. The majority of reports concerning simvastatin treatment in the majority of human cancers have demonstrated that survivin is significantly decreased as a result and has been implicated in tumorigenesis. However, only a limited number of studies have investigated the use of simvastatin for the treatment of salivary gland adenoid cystic carcinoma (SACC). Therefore, this agent is a candidate for further investigation. The aim of the present study was to investigate the effects of simvastatin on the proliferation, invasion and apoptosis of the human salivary adenoid cystic carcinoma cell line, SACC-83, as well as survivin expression in the cells. The Cell Counting kit-8 assay results revealed that simvastatin inhibited the proliferation of SACC-83 cells in a dose-dependent (10 to 50 µM) and time-dependent (24 to 48 h) manner when compared with the untreated cells. Flow cytometry analysis indicated that simvastatin increased the percentage of cells in early and late apoptosis. Invasion assays revealed that simvastatin treatment inhibited the invasiveness of SACC-83 cells in a dose-dependent manner. In addition, simvastatin downregulated survivin expression in SACC-83 cells. In conclusion, simvastatin significantly inhibited the proliferation and invasion of SACC-83 cells, induced apoptosis, and reduced the expression of survivin, which suggests that simvastatin may be a novel target for SACC therapy.

Exploring the relationship between nonalcoholic fatty liver disease and pancreatic cancer by computed tomographic survey

Pancreatic cancer is difficult to diagnose in an early stage, and has the highest mortality of all types of cancer. Obesity, high body mass index, and increased abdominal girth are established risk factors. Some studies have postulated that there is a correlation between organ steatosis and pancreatic cancer. This study aims to explore whether nonalcoholic fatty liver disease (NAFLD) is a risk factor and a prognostic factor for pancreatic cancer. The study enrolled 557 patients (143 with and 414 without pancreatic cancer) who were diagnosed between January 2009 and December 2013. We reviewed the abdominal computed tomographic scans of the patients to confirm the diagnosis of NAFLD. Clinical parameters, laboratory data, and personal information were analyzed. NAFLD is an independent risk factor for pancreatic cancer according to adjusted multivariate logistic regression analysis (OR 2.63, 95% CI 1.24-5.58, p = 0.011). The Kaplan-Meier survival curve reveals that patients without NAFLD have longer survival than patients with NAFLD (p = 0.005, log-rank test). NAFLD is positively correlated with pancreatic cancer, a result suggesting that NAFLD may increase the incidence and risk of pancreatic cancer. Patients with pancreatic cancer and NAFLD have poorer overall survival than patients without NAFLD, perhaps, because dysregulated cytokine status leads to progression of pancreatic cancer. NAFLD may be a prognostic factor for pancreatic cancer.

DNAJA1 controls the fate of misfolded mutant p53 through the mevalonate pathway

Stabilization of mutant p53 (mutp53) in tumours greatly contributes to malignant progression. However, little is known about the underlying mechanisms and therapeutic approaches to destabilize mutp53. Here, through high-throughput screening we identify statins, cholesterol-lowering drugs, as degradation inducers for conformational or misfolded p53 mutants with minimal effects on wild-type p53 (wtp53) and DNA contact mutants. Statins preferentially suppress mutp53-expressing cancer cell growth. Specific reduction of mevalonate-5-phosphate by statins or mevalonate kinase knockdown induces CHIP ubiquitin ligase-mediated nuclear export, ubiquitylation, and degradation of mutp53 by impairing interaction of mutp53 with DNAJA1, a Hsp40 family member. Knockdown of DNAJA1 also induces CHIP-mediated mutp53 degradation, while its overexpression antagonizes statin-induced mutp53 degradation. Our study reveals that DNAJA1 controls the fate of misfolded mutp53, provides insights into potential strategies to deplete mutp53 through the mevalonate pathway-DNAJA1 axis, and highlights the significance of p53 status in impacting statins' efficacy on cancer therapy.

Lovastatin causes FaDu hypopharyngeal carcinoma cell death via AMPK-p63-survivin signaling cascade

Statins are used widely to lower serum cholesterol and the incidence of cardiovascular diseases. Growing evidence shows that statins also exhibit beneficial effects against cancers. In this study, we investigated the molecular mechanisms involved in lovastatin-induced cell death in Fadu hypopharyngeal carcinoma cells. Lovastatin caused cell cycle arrest and apoptosis in FaDu cells. Lovastatin increased p21^cip/Waf1 level while the survivin level was decreased in the presence of lovastatin. Survivin siRNA reduced cell viability and induced cell apoptosis in FaDu cells. Lovastatin induced phosphorylation of AMP-activated protein kinase (AMPK), p38 mitogen-activated protein kinase (MAPK) and transcription factor p63. Lovastatin also caused p63 acetylation and increased p63 binding to survivin promoter region in FaDu cells. AMPK-p38MAPK signaling blockade abrogated lovastatin-induced p63 phosphorylation. Lovastatin’s enhancing effect on p63 acetylation was reduced in HDAC3- or HDAC4- transfected cells. Moreover, transfection of cells with AMPK dominant negative mutant (AMPK-DN), HDAC3, HDAC4 or p63 siRNA significantly reduced lovastatin’s effects on p21^cip/Waf1 and survivin. Furthermore, lovastatin inhibited subcutaneous FaDu xenografts growth in vivo. Taken together, lovastatin may activate AMPK-p38MAPK-p63-survivin cascade to cause FaDu cell death. This study establishes, at least in part, the signaling cascade by which lovastatin induces hypopharyngeal carcinoma cell death.

Targeting Oncogenic Mutant p53 for Cancer Therapy

Among genetic alterations in human cancers, mutations in the tumor suppressor p53 gene are the most common, occurring in over 50% of human cancers. The majority of p53 mutations are missense mutations and result in the accumulation of dysfunctional p53 protein in tumors. These mutants frequently have oncogenic gain-of-function activities and exacerbate malignant properties of cancer cells, such as metastasis and drug resistance. Increasing evidence reveals that stabilization of mutant p53 in tumors is crucial for its oncogenic activities, while depletion of mutant p53 attenuates malignant properties of cancer cells. Thus, mutant p53 is an attractive druggable target for cancer therapy. Different approaches have been taken to develop small-molecule compounds that specifically target mutant p53. These include compounds that restore wild-type conformation and transcriptional activity of mutant p53, induce depletion of mutant p53, inhibit downstream pathways of oncogenic mutant p53, and induce synthetic lethality to mutant p53. In this review article, we comprehensively discuss the current strategies targeting oncogenic mutant p53 in cancers, with special focus on compounds that restore wild-type p53 transcriptional activity of mutant p53 and those reducing mutant p53 levels.

Statin use and risk of liver cancer: an update meta-analysis

OBJECTIVE

Statins are commonly prescribed cholesterol-lowering drugs. Preclinical studies suggest that statins may possess cancer preventive properties. The primary objective of this meta-analysis was to determine the association between statin use and risk of liver cancer.

DESIGN

Meta-analysis.

SETTING

International.

PARTICIPANTS

A comprehensive literature search of PubMed, BIOSIS Previews, Web of Science, EMBASE, EBSCO and Cochrane Library was conducted through March 2014. The effect estimate was reported as pooled relative risk (RR) with 95% CIs, using the random-effects model.

RESULTS

A total of 12 studies (1 individual patient data analysis of 22 randomised controlled trials, 5 cohorts and 6 case-controls) were qualified for this meta-analysis, involving 5,640,313 participants including 35,756 liver cancer cases. Our results indicated a significant risk reduction of liver cancer among all statin users (RR=0.58, 95% CIs 0.51 to 0.67). The difference of the study designs can partly explain the significant heterogeneity found in the overall analysis (I(2)=65%, p=0.0006). No evidence of publication bias was observed in this meta-analysis. Similar risk reductions were found in the subgroups analysis of Western and Asian countries, lipophilic and hydrophilia statins. There was a trend towards more risk reductions in subgroups with higher baseline risk, inadequate adjustment and higher cumulative dosage of statin use.

CONCLUSIONS

This meta-analysis suggests that statin is associated with a significant risk reduction of liver cancer when taken daily for cardiovascular event prevention. However, this preventive effect might be overestimated due to the exposure period, the indication and contraindication of statins and other confounders. Statins might be considered as an adjuvant in the treatment of liver cancer.

Novel prospects of statins as therapeutic agents in cancer

Statins are well known competitive inhibitors of hydroxymethylglutaryl-CoA reductase enzyme (HMG-CoA reductase), thus traditionally used as cholesterol-lowering agents. In recent years, more and more effects of statins have been revealed. Nowadays alterations of lipid metabolism have been increasingly recognized as a hallmark of cancer cells. Consequently, much attention has been directed toward the potential of statins as therapeutic agents in the oncological field. Accumulated in vitro and in vivo clinical evidence point out the role of statins in a variety of human malignancies, in regulating tumor cell growth and anti-tumor immune response. Herein, we summarize and discuss, in light of the most recent observations, the anti-tumor effects of statins, underpinning the detailed mode of action and looking for their true significance in cancer prevention and treatment, to determine if and in which case statin repositioning could be really justified for neoplastic diseases.

Aspirin may prevent cholangiocarcinoma: a case-control study from the United kingdom

BACKGROUND

The proliferation of cholangiocarcinoma cells is suppressed in cell culture by nonsteroidal antiinflammatory drugs (NSAIDs) through the inhibition of cyclo-oxygenase-2 enzyme and also by statins which decrease the production of mediators of the cell cycle.

AIMS

To investigate whether there is an inverse association between NSAIDs, including aspirin, and the development of cholangiocarcinoma and, for the first time in a Western population, between statin use and the development of cholangiocarcinoma.

METHODS

This epidemiological study had a case-control design in which cases of cholangiocarcinoma diagnosed in Norwich between 2004 and 2010 and in Leicester in 2007 were identified from clinical databases. Controls were patients with basal cell carcinomas treated in the respective dermatology departments. The case notes of all subjects were reviewed to confirm diagnoses and obtain information on medication use. The data were analyzed using unconditional logistic regression to calculate odds ratios (OR) with 95 % confidence intervals (CI).

RESULTS

In total, 81 cases of cholangiocarcinoma and 275 controls were identified. For all cases there was radiological evidence of cancer and 86 % of the cases involved the extrahepatic biliary system. Aspirin use was inversely associated with the development of cholangiocarcinoma (OR 0.45, 95 % CI 0.22-0.92), but there were no significant associations between the development of cholangiocarcinoma and NSAIDs (OR 0.39; 95 % CI 0.11-1.42) or statins (OR 0.58; 95 % CI 0.28-1.19).

CONCLUSIONS

The epidemiological data from this study support the biological evidence for aspirin having a protective effect against the development of cholangiocarcinoma. Aspirin use should be measured in future etiological studies and assessed as a chemoprevention agent in those at high risk of developing this type of cancer.

Effect of onion flavonoids on colorectal cancer with hyperlipidemia: an in vivo study

Objectives

This study aims to find the effect of onion’s extraction on the colorectal cancer with hyperlipidemia.

Method

We established a hyperlipidemia-subcutaneously heterotopic colorectal cancer orthotopic transplant model and fed mice a high fat diet and performing transplantation. Animal models were treated with capecitabine and/or simvastatin and low-, middle-, high- dose of onion’s extraction and both tumor growth rate and blood lipid levels were monitored.

Results

We found that colorectal cancer in onion’s extraction groups was significantly inhibited, and the effect of high dose of onion’s extraction was equivalent to capecitabine. Onion’s extraction effectively decreased levels of apoB and TC.

Conclusion

Our study established a hyperlipidemia colon tumor model involving subcutaneous colon translocation and orthotopic transplantation, this model was an ideal research model for mutual influence of hyperlipidemia and colorectal cancer. Onion’s extraction could inhibit the proliferation of colorectal cancer; the function of the high-dose of onion’s extraction was fairly to capecitabine, which provided a new direction in protecting and treating colorectal cancer.

Statins: perspectives in cancer therapeutics

Virtually any cell type in a mammalian organism uses Acetyl CoA to yield mevalonate, through the activity of the 3-hydroxy-3-methyl-glutaryl-CoA reductase enzyme and, ultimately, cholesterol. Statins have long and quite successfully been used as cholesterol lowering drugs. They reversibly inhibit the 3-hydroxy-3-methyl-glutaryl-CoA reductase activity, which is rate limiting in the early steps of the cholesterol synthesis pathway. In addition to these effects, it has also been amply shown that statins may efficiently trigger cancer cell apoptosis, making them a plausible therapeutic option for the treatment of cancer. Whether statins may prevent cancer occurrence is a matter of debate and an unanswered question; undoubtedly experimental models have clearly demonstrated the potential of statins as direct cytotoxic agents, which can reduce tumour development or metastasis spread, even more so when combined with cytotoxic drugs. Until now, however, only few data in humans support the idea that statins could rightfully belong to the group of anticancer drugs. Nevertheless, as cancer cell metabolism is being thoroughly revisited, the mevalonate pathway has recently been reported as truly oncogenic, presenting the attractive possibility that mevalonate pathway inhibitors, such as statins, may join the ranks of anticancer drugs.

Simvastatin induced HCT116 colorectal cancer cell apoptosis through p38MAPK-p53-survivin signaling cascade

BACKGROUND

Statins, the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors with cholesterol-lowering properties, were recently shown to exhibit anti-cancer effects. However, the molecular mechanism underlying statin-induced cancer cell death remains to be elucidated. Elevated level of survivin is often found over-expressed in human cancers and has been implicated in the progression of tumorigenesis. Given its central role in cell division and action as an apoptosis suppressor, survivin represents a potential molecular target in cancer management.

METHODS

In this study, we explored the underlying mechanisms in simvastatin-induced HCT116 colorectal cancer cell apoptosis.

RESULTS

Simvastatin decreased cell viability and induced cell apoptosis in HCT116 cells. These results are associated with the modulation of p21(cip/Waf1) and survivin. Survivin knockdown using survivin siRNAs also decreased cell viability and induced cell apoptosis. Simvastatin's actions on p21(cip/Waf1), survivin and apoptosis were reduced in p53 null HCT116 cells. Simvastatin caused an increase in p53 phosphorylation and acetylation. In addition, simvastatin activated p38 mitogen-activated protein kinase (p38MAPK), whereas an inhibitor of p38MAPK signaling abrogated simvastatin's effects of increasing p53 and p21(cip/Waf1) promoter luciferase activity. Cell viability and survivin promoter luciferase activity in the presence of simvastatin were also restored by p38MAPK inhibitor. Furthermore, Sp1 binding to the survivin promoter region decreased while p53 and p63 binding to the promoter region increased after simvastatin exposure.

CONCLUSIONS

Simvastatin activates the p38MAPK-p53-survivin cascade to cause HCT116 colorectal cancer cell apoptosis.

GENERAL SIGNIFICANCE

This study delineates, in part, the underlying mechanisms of simvastatin in decreasing survivin and subsequent colorectal cancer cell apoptosis.

Clinical outcomes of chemotherapy for diabetic and nondiabetic patients with pancreatic cancer: better prognosis with statin use in diabetic patients

OBJECTIVES

The aim of this study was to clarify the impact of diabetes mellitus (DM) as well as antidiabetic, antihypertensive, and antihyperlipidemic medications such as metformin and statins on survival in patients with advanced pancreatic cancer receiving chemotherapy.

METHODS

We retrospectively reviewed the medical records of 250 patients with advanced pancreatic cancer receiving chemotherapy. Multivariate analyses of prognostic factors for survival were performed both in overall population and in subgroups with and without DM.

RESULTS

Diabetes mellitus was diagnosed in 124 patients (50%) who had less distant metastasis and more hypertension. Thirty patients received statin for hyperlipidemia. Overall survival was 13.3 versus 10.0 months with and without DM (P = 0.084), but hazard ratio of DM was 1.05 (P = 0.758) in the multivariate analysis. Subgroup analysis of diabetic patients, but not in non-diabetic patients, demonstrated use of statins (hazard ratio, 0.40; P = 0.010) as a prognostic factor, as well as distant metastasis, performance status, combination therapy with gemcitabine and S-1, and use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. No antidiabetic medications were prognostic factors.

CONCLUSIONS

Neither DM nor antidiabetic treatment had prognostic impact on advanced pancreatic cancer. Statin use was associated with better survival in the diabetic patients.

Statin use and risk of pancreatic cancer: a meta-analysis

PURPOSE

Statins are commonly prescribed medications that potently reduce cholesterol levels and the risk of cardiovascular events. Preclinical studies suggested statins also possess cancer chemopreventive properties. However, the clinical studies provided contradictory results as to whether statins influence the risk of pancreatic cancer. Herein, we present this meta-analysis to assess the association between statin use and risk of pancreatic cancer.

METHODS

We conducted a comprehensive search up to August 2011 for the eligible studies. Pooled relative risk (RR) estimates and corresponding 95 % confidence intervals (CIs) were calculated using the inverse-variance-weighted random-effects model. Subgroup analyses were conducted where data were available. Heterogeneity was assessed by the Cochran's Q test and the I(2) statistic.

RESULTS

We included 16 studies that involving 1,692,863 participants and 7,807 pancreatic cancer cases. Pooled results only indicated a non-significant decrease of pancreatic cancer risk among all statin users (RR 0.89; 95 % CIs, 0.74-1.07). Similar results were obtained in the subgroup analyses of the long-term (more than 4 years) follow-up (RR 0.94, 0.81-1.08) and statin use (RR 0.97, 0.76-1.23), and a null association was found between lipophilic statin use and pancreatic cancer risk (RR 1.03, 0.92-1.16). No evidence of publication bias was observed in the present meta-analysis. However, significant heterogeneity was detected among all studies (p < 0.00001, I(2) = 81 %).

CONCLUSIONS

In conclusion, our results suggest that there is no association between statin use and pancreatic cancer risk, when statins are taken at daily doses for cardiovascular event prevention.

Role of squalene synthase in prostate cancer risk and the biological aggressiveness of human prostate cancer

BACKGROUND

We previously conducted a genome-wide linkage analysis of Japanese nuclear families affected with prostate cancer and showed that the susceptibility to prostate cancer was closely linked to D8S550 at 8p23. The role of farnesyl diphosphate farnesyltransferase (FDFT1), which is located under the peak marker D8S550 at 8p23, and squalene synthase, the enzyme encoded by FDFT1, in prostate cancer was studied.

METHODS

The association among common variants of FDFT1 with prostate cancer risk, the promoter activities of FDFT1 with different genotypes and the effects of inhibition of squalene synthase were studied, and the FDFT1 transcript levels of human prostate samples were quantified.

RESULTS

The A allele of rs2645429 was significantly associated with prostate cancer risk in a Japanese familial prostate cancer population. Rs2645429 was located in the promoter region of FDFT1, and the AA genotype showed significantly increased promoter activity. The knockdown of FDFT1 mRNA expression or squalene synthase inhibition led to a significant decrease in prostate cancer cell proliferation. Additionally, human prostate cancer specimens expressed significantly higher levels of FDFT1 mRNA compared with noncancerous specimens. Finally, aggressive cancers showed higher transcript levels.

CONCLUSIONS

FDFT1 and its encoded enzyme, squalene synthase, may play an important role in prostate cancer development and its aggressive phenotypes.

Esophageal and gastric cancer incidence and mortality in alendronate users

Recent studies have reached conflicting conclusions regarding the risk of esophageal cancer with oral bisphosphonates. Prior studies did not record the number of cancer deaths or endoscopy rates, which could be higher in bisphosphonate users and lead to more cancers being diagnosed at a stage when their esophageal or gastric location could be accurately distinguished. We conducted a register-based, open cohort study using national healthcare data for Denmark. Upper endoscopy frequency, cancer incidence and mortality was examined in 30,606 alendronate users (female, age 50+) and 122,424 matched controls. Primary outcomes were esophageal cancer incidence and death because of esophageal cancer. The analysis showed that alendronate users were more likely to have undergone recent upper endoscopy (4.1 versus 1.7%, p < 0.001). Alendronate users had a lower risk of incident gastric cancer [odds ratio (OR) 0.61; 95% confidence interval (CI): 0.39-0.97) and no increased risk of esophageal cancer (OR 0.71; 95% CI: 0.43-1.19). Risk reductions were greater in users with 10+ prescriptions. The risk of dying of esophageal cancer was significantly reduced in alendronate users after 3 years OR 0.45 (95% CI: 0.22-0.92) but not after 9 years (OR 1.01; 95% CI: 0.52-1.95). An additional comparison with etidronate users revealed no statistically significant difference in outcomes. In conclusion, we found no excess in esophageal cancer deaths or incidence. The early decrease in esophageal cancer rates may relate to the greater use of endoscopy before starting alendronate. Longer term observations also indicated no excess risk of esophageal cancer death and a significantly decreased risk of gastric cancer death.

Differential effects of pravastatin and simvastatin on the growth of tumor cells from different organ sites

3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) inhibitors, commonly known as statins, may possess cancer preventive and therapeutic properties. Statins are effective suppressors of cholesterol synthesis with a well-established risk-benefit ratio in cardiovascular disease prevention. Mechanistically, targeting HMGCR activity primarily influences cholesterol biosynthesis and prenylation of signaling proteins. Pravastatin is a hydrophilic statin that is selectively taken up by a sodium-independent organic anion transporter protein-1B1 (OATP1B1) exclusively expressed in liver. Simvastatin is a hydrophobic statin that enters cells by other mechanisms. Poorly-differentiated and well-differentiated cancer cell lines were selected from various tissues and examined for their response to these two statins. Simvastatin inhibited the growth of most tumor cell lines more effectively than pravastatin in a dose dependent manner. Poorly-differentiated cancer cells were generally more responsive to simvastatin than well-differentiated cancer cells, and the levels of HMGCR expression did not consistently correlate with response to statin treatment. Pravastatin had a significant effect on normal hepatocytes due to facilitated uptake and a lesser effect on prostate PC3 and colon Caco-2 cancer cells since the OATP1B1 mRNA and protein were only found in the normal liver and hepatocytes. The inhibition of cell growth was accompanied by distinct alterations in mitochondrial networks and dramatic changes in cellular morphology related to cofilin regulation and loss of p-caveolin. Both statins, hydrophilic pravastatin and hypdrophobic simvastatin caused redistribution of OATP1B1 and HMGCR to perinuclear sites. In conclusion, the specific chemical properties of different classes of statins dictate mechanistic properties which may be relevant when evaluating biological responses to statins.