Lovastatin and tumor necrosis factor-alpha exhibit potentiated antitumor effects against Ha-ras-transformed murine tumor via inhibition of tumor-induced angiogenesis

Statins as anti-tumor agents: A paradigm for repurposed drugs

BACKGROUND

Statins, frequently prescribed medications, work by inhibiting the rate-limiting enzyme HMG-CoA reductase (HMGCR) in the mevalonate pathway to reduce cholesterol levels. Due to their multifaceted benefits, statins are being adapted for use as cost-efficient, safe and effective anti-cancer treatments. Several studies have shown that specific types of cancer are responsive to statin medications since they rely on the mevalonate pathway for their growth and survival.

RECENT FINDINGS

Statin are a class of drugs known for their potent inhibition of cholesterol production and are typically prescribed to treat high cholesterol levels. Nevertheless, there is growing interest in repurposing statins for the treatment of malignant neoplastic diseases, often in conjunction with chemotherapy and radiotherapy. The mechanism behind statin treatment includes targeting apoptosis through the BCL2 signaling pathway, regulating the cell cycle via the p53-YAP axis, and imparting epigenetic modulations by altering methylation patterns on CpG islands and histone acetylation by downregulating DNMTs and HDACs respectively. Notably, some studies have suggested a potential chemo-preventive effect, as decreased occurrence of tumor relapse and enhanced survival rate were reported in patients undergoing long-term statin therapy. However, the definitive endorsement of statin usage in cancer therapy hinges on population based clinical studies with larger patient cohorts and extended follow-up periods.

CONCLUSIONS

The potential of anti-cancer properties of statins seems to reach beyond their influence on cholesterol production. Further investigations are necessary to uncover their effects on cancer promoting signaling pathways. Given their distinct attributes, statins might emerge as promising contenders in the fight against tumorigenesis, as they appear to enhance the efficacy and address the limitations of conventional cancer treatments.

Topological data analysis distinguishes parameter regimes in the Anderson-Chaplain model of angiogenesis

Angiogenesis is the process by which blood vessels form from pre-existing vessels. It plays a key role in many biological processes, including embryonic development and wound healing, and contributes to many diseases including cancer and rheumatoid arthritis. The structure of the resulting vessel networks determines their ability to deliver nutrients and remove waste products from biological tissues. Here we simulate the Anderson-Chaplain model of angiogenesis at different parameter values and quantify the vessel architectures of the resulting synthetic data. Specifically, we propose a topological data analysis (TDA) pipeline for systematic analysis of the model. TDA is a vibrant and relatively new field of computational mathematics for studying the shape of data. We compute topological and standard descriptors of model simulations generated by different parameter values. We show that TDA of model simulation data stratifies parameter space into regions with similar vessel morphology. The methodologies proposed here are widely applicable to other synthetic and experimental data including wound healing, development, and plant biology.

Pleiotropic effects of statins: A focus on cancer

The statin drugs ('statins') potently inhibit hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase by competitively blocking the active site of the enzyme. Statins decrease de novo cholesterol biosynthesis and thereby reduce plasma cholesterol levels. Statins exhibit "pleiotropic" properties that are independent of their lipid-lowering effects. For example, preclinical evidence suggests that statins inhibit tumor growth and induce apoptosis in specific cancer cell types. Furthermore, statins show chemo-sensitizing effects by impairing Ras family GTPase signaling. However, whether statins have clinically meaningful anti-cancer effects remains an area of active investigation. Both preclinical and clinical studies on the potential mechanisms of action of statins in several cancers have been reviewed in the literature. Considering the contradictory data on their efficacy, we present an up-to-date summary of the pleiotropic effects of statins in cancer therapy and review their impact on different malignancies. We also discuss the synergistic anti-cancer effects of statins when combined with other more conventional anti-cancer drugs to highlight areas of potential therapeutic development.

Pleiotropic use of Statins as non-lipid-lowering drugs

Statins, known as HMG-CoA reductase (HMGCR) inhibitors, have primarily been utilized for metabolic and angiographic medical applications because of their cholesterol-lowering effects. Similar to other drugs, statins may also induce a series of potential side effects. Statins inhibit the HMGCR (rate-limiting enzyme) activity in early stages of mevalonate pathway and then indirectly affect a number of intermediate products, including non-sterol isoprenoids (coenzyme Q10, dolichol etc.), which can result in impaired functions of body organs. Recently, scores of studies have uncovered additional functional mechanisms of statins in other diseases, such as diabetes mellitus, nervous system diseases, coronary heart disease, inflammation and cancers. This review aims to summarize the positive and adverse mechanisms of statin therapy. Statin care should be taken in the treatment of many diseases including cancers. Since the underlying mechanisms are not fully elucidated, future studies should spend more time and efforts on basic research to explore the mechanisms of statins.

Cholesterol Trafficking: An Emerging Therapeutic Target for Angiogenesis and Cancer

Cholesterol is an essential structural component of cellular membranes. In addition to the structural role, it also serves as a precursor to a variety of steroid hormones and has diverse functions in intracellular signal transduction. As one of its functions in cell signaling, recent evidence suggests that cholesterol plays a key role in regulating angiogenesis. This review discusses the role of cholesterol in angiogenesis, with a particular emphasis on cholesterol trafficking in endothelial cell signaling. Small molecule inhibitors of cholesterol trafficking and their preclinical and clinical development targeting angiogenesis and cancer are also discussed.

Statins use and cancer: an update

After initial concerns regarding the association of statins with increased incidences of cancer and elevated cancer-related mortality, there are now plenty of data on the antitumor, cytostatic and cytotoxic effectiveness of this class of drugs. Here, we present a short review of possible mechanisms of antineoplastic activity obtained from preclinical research and the influence of statins on cancer treatment. In the second part of the article, we focus on the most recent data from observational clinical trials, as well as meta-analyses regarding cancer incidence and mortality in patients treated with statins.

Pharmacological blockade of cholesterol trafficking by cepharanthine in endothelial cells suppresses angiogenesis and tumor growth

Cholesterol is an important modulator of membrane protein function and signaling in endothelial cells, thus making it an emerging target for anti-angiogenic agents. In this study, we employed a phenotypic screen that detects intracellular cholesterol distribution in endothelial cells (HUVEC) and identified 13 existing drugs as cholesterol trafficking inhibitors. Cepharanthine, an approved drug for anti-inflammatory and cancer management use, was amongst the candidates, which was selected for in-depth mechanistic studies to link cholesterol trafficking and angiogenesis. Cepharanthine inhibited the endolysosomal trafficking of free-cholesterol and low-density lipoprotein in HUVEC by binding to Niemann-Pick disease, type C1 (NPC1) protein and increasing the lysosomal pH. The blockade of cholesterol trafficking led to a cholesterol-dependent dissociation of mTOR from the lysosomes and inhibition of its downstream signaling. Cepharanthine inhibited angiogenesis in HUVEC and in zebrafish in a cholesterol-dependent manner. Furthermore, cepharanthine suppressed tumor growth in vivo by inhibiting angiogenesis and it enhanced the antitumor activity of the standard chemotherapy cisplatin in lung and breast cancer xenografts in mice. Altogether, these results strongly support the idea that cholesterol trafficking is a viable drug target for anti-angiogenesis and that the inhibitors identified among existing drugs, such as cepharanthine, could be potential anti-angiogenic and antitumor agents.

Marketed drugs used for the management of hypercholesterolemia as anticancer armament

The design of novel pharmacologic agents as well as their approval for sale in markets all over the world is a tedious and pricey process. Inevitably, oncologic patients commonly experience unwanted effects of new anticancer drugs, while the acquisition of clinical experience for these drugs is largely based on doctor–patient partnership which is not always effective. The repositioning of marketed non-antineoplastic drugs that hopefully exhibit anticancer properties into the field of oncology is a challenging option that gains ground and attracts preclinical and clinical research in an effort to override all these hindrances and minimize the risk for reduced efficacy and/or personalized toxicity. This review aims to present the anticancer properties of drugs used for the management of hypercholesterolemia. A global view of the antitumorigenicity of all marketed antihypercholesterolemic drugs is of major importance, given that atherosclerosis, which is etiologically linked to hypercholesterolemia, is a leading worldwide cause of morbidity and mortality, while hypercholesterolemia and tumorigenesis are known to be interrelated. In vitro, in vivo and clinical literature data accumulated so far outline the mechanistic basis of the antitumor function of these agents and how they could find application at the clinical setting.

Effects of Lovastatin on MDA-MB-231 Breast Cancer Cells: An Antibody Microarray Analysis

Despite the tremendous improvement in cancer therapeutics, treatment of late-stage breast cancer remains a challenge for both basic scientists and clinicians. Lovastatin, a natural product derived from Aspergillus terreus or Monascus ruber, has been widely used as cholesterol-lowing drug in the clinic. It also has anti-cancer properties through poorly defined molecular mechanisms. In the present study, we employed a novel antibody microarray technology to investigate the molecular mechanisms through which lovastatin inhibits breast cancer. We found that lovastatin up-regulated 17 proteins and down-regulated 20 proteins in MDA-MB-231 breast cancer cells. These included proteins that modulate apoptosis, cell proliferation, differentiation, signal transduction, epithelial-to-mesenchymal transition and tumor metastasis. Modulation of these pathways may mediate, in part, the inhibitory activity of lovastatin on breast cancer.

Exploitation of pleiotropic actions of statins by using tumour-targeted delivery systems

Statins are drugs traditionally used to lower cholesterol levels in blood. At concentrations 100- to 500-fold higher than those needed for reaching cholesterol lowering activity, they have anti-tumour activity. This anti-tumour activity is based on statins pleiotropic effects derived from their ability to inhibit the mevalonate synthesis and include anti-proliferative, pro-apoptotic, anti-angiogenic, anti-inflammatory, anti-metastatic actions and modulatory effects on intra-tumour oxidative stress. Thus, in this review, we summarise the possible pleiotropic actions of statins involved in tumour growth inhibition. Since the administration of these high doses of statins is accompanied by severe side effects, targeted delivery of statins seems to be the appropriate strategy for efficient application of statins in oncology. Therefore, we also present an overview of the current status of targeted delivery systems for statins with possible utilisation in oncology.

Statins are potential anticancerous agents (review)

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

Statins 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.

Simvastatin radiosensitizes differentiated and stem-like breast cancer cell lines and is associated with improved local control in inflammatory breast cancer patients treated with postmastectomy radiation

Reported rates of local failure after adjuvant radiation for women with inflammatory breast cancer (IBC) and triple-negative non-IBC are higher than those of women with receptor-expressing non-IBC. These high rates of locoregional recurrence are potentially influenced by the contribution of radioresistant cancer stem cells to these cancers. Statins have been shown to target stem cells and improve disease-free survival among IBC patients. We examined simvastatin radiosensitization of multiple subtypes of breast cancer cell lines in vitro in monolayer and mammosphere-based clonogenic assays and examined the therapeutic benefit of statin use on local control after postmastectomy radiation (PMRT) among IBC patients. We found that simvastatin radiosensitizes mammosphere-initiating cells (MICs) of IBC cell lines (MDA-IBC3, SUM149, SUM190) and of the metaplastic, non-IBC triple-negative receptor cell line (SUM159). However, simvastatin radioprotects MICs of non-IBC cell lines MCF-7 and SKBR3. In a retrospective clinical study of 519 IBC patients treated with PMRT, 53 patients used a statin. On univariate analysis, actuarial 3-year local recurrence-free survival (LRFS) was higher among statin users, and on multivariate analysis, triple negative breast cancer, absence of lymphatic invasion, neoadjuvant pathological tumor response to preoperative chemotherapy, and statin use were independently associated with higher LRFS. In conclusion, patients with IBC and triple-negative non-IBC breast cancer have the highest rates of local failure, and there are no available known radiosensitizers. We report significant improvement in local control after PMRT among statin users with IBC and significant radiosensitization across triple-negative and IBC cell lines of multiple subtypes using simvastatin. These data suggest that simvastatin should be justified as a radiosensitizing agent by a prospective clinical trial.

Statin use is associated with decreased prostate cancer recurrence in men treated with brachytherapy

PURPOSE/OBJECTIVE(S)

Recent in vitro and in vivo evidence has suggested that statin medications may have anticancer activity. We sought to determine whether statin use was associated with improved clinical outcome in men treated with brachytherapy for prostate cancer.

MATERIALS/METHODS

A database of men with prostate cancer treated with permanent Iodine-125 brachytherapy between January 1999 and February 2009 was retrospectively analyzed. Standard guidelines (i.e., American Brachytherapy Society selection criteria) were used for selecting patients for brachytherapy. Biochemical failure was defined using the Phoenix definition.

RESULTS

From a total of 247 men with prostate adenocarcinoma treated with brachytherapy, 174 patients (70 %) were identified as using statin medications, either during initial visit or during follow-up. Median PSA follow-up was 51 months after date of implant (range 9.4-140.35). Overall biochemical failure rate was 7.3 % (18 patients). On univariate analysis, statin use was associated with significantly improved freedom from biochemical failure [hazard ratio (HR) 0.28; 95 % CI 0.10-0.72; p < 0.01 by log-rank test]. In multivariate Cox analysis performed with the variables statin use, pretreatment PSA, clinical T stage, Gleason score, and D90 or V100, statin use remained significantly associated with improved freedom from biochemical failure (HR 0.288; 95 % CI 0.086-0.886; p = 0.0299).

CONCLUSIONS

Statin use was associated with a significant improvement in freedom from biochemical failure in this cohort of men treated with brachytherapy for prostate cancer. Further investigation into the favorable effect of statin use on brachytherapy and radiation therapy in general is warranted, including prospective trials.

Targeting the mevalonate cascade as a new therapeutic approach in heart disease, cancer and pulmonary disease

The cholesterol biosynthesis pathway, also known as the mevalonate (MVA) pathway, is an essential cellular pathway that is involved in diverse cell functions. The enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase (HMGCR) is the rate-limiting step in cholesterol biosynthesis and catalyzes the conversion of HMG-CoA to MVA. Given its role in cholesterol and isoprenoid biosynthesis, the regulation of HMGCR has been intensely investigated. Because all cells require a steady supply of MVA, both the sterol (i.e. cholesterol) and non-sterol (i.e. isoprenoid) products of MVA metabolism exert coordinated feedback regulation on HMGCR through different mechanisms. The proper functioning of HMGCR as the proximal enzyme in the MVA pathway is essential under both normal physiologic conditions and in many diseases given its role in cell cycle pathways and cell proliferation, cholesterol biosynthesis and metabolism, cell cytoskeletal dynamics and stability, cell membrane structure and fluidity, mitochondrial function, proliferation, and cell fate. The blockbuster statin drugs ('statins') directly bind to and inhibit HMGCR, and their use for the past thirty years has revolutionized the treatment of hypercholesterolemia and cardiovascular diseases, in particular coronary heart disease. Initially thought to exert their effects through cholesterol reduction, recent evidence indicates that statins also have pleiotropic immunomodulatory properties independent of cholesterol lowering. In this review we will focus on the therapeutic applications and mechanisms involved in the MVA cascade including Rho GTPase and Rho kinase (ROCK) signaling, statin inhibition of HMGCR, geranylgeranyltransferase (GGTase) inhibition, and farnesyltransferase (FTase) inhibition in cardiovascular disease, pulmonary diseases (e.g. asthma and chronic obstructive pulmonary disease (COPD)), and cancer.

Pharmacological actions of statins: a critical appraisal in the management of cancer

Statins, among the most commonly prescribed drugs worldwide, are cholesterol-lowering agents used to manage and prevent cardiovascular and coronary heart diseases. Recently, a multifaceted action in different physiological and pathological conditions has been also proposed for statins, beyond anti-inflammation and neuroprotection. Statins have been shown to act through cholesterol-dependent and -independent mechanisms and are able to affect several tissue functions and modulate specific signal transduction pathways that could account for statin pleiotropic effects. Typically, statins are prescribed in middle-aged or elderly patients in a therapeutic regimen covering a long life span during which metabolic processes, aging, and concomitant novel diseases, including cancer, could occur. In this context, safety, toxicity, interaction with other drugs, and the state of health have to be taken into account in subjects treated with statins. Some evidence has shown a dichotomous effect of statins with either cancer-inhibiting or -promoting effects. To date, clinical trials failed to demonstrate a reduced cancer occurrence in statin users and no sufficient data are available to define the long-term effects of statin use over a period of 10 years. Moreover, results from clinical trials performed to evaluate the therapeutic efficacy of statins in cancer did not suggest statin use as chemotherapeutic or adjuvant agents. Here, we reviewed the pharmacology of the statins, providing a comprehensive update of the current knowledge of their effects on tissues, biological processes, and pathological conditions, and we dissected the disappointing evidence on the possible future use of statin-based drugs in cancer therapy.

Immunohistochemistry Evaluation of the Effect in Vivo of Tumor Necrosis Factor (TNF)-alpha on Blood Vessel Density in Murine Fibrosarcoma

Purpose: Angiogenesis is essential for tumor growth and metastases, thus bestowing obvious importance upon methodologies which could enable its inhibition.

Materials: C57BL/6 female mice bearing a subcutaneous (s.c.) MCA205 fibrosarcoma were used.

Methods: Ten mice were divided equally into two groups. One group was injected intraperitoneally (i.p.) with 10 μg tumor necrosis factor-α (TNF-α and the other (controls) with Hanks balanced salt solution (HBSS). Tumor growth was monitored at least twice weekly. The number of endothelial cells in the blood microvessels was assessed by immunohistostaining on paraffin-embedded tumor tissue sections using vascular endothelial growth factor (VEGF) and Factor 8 antibodies. Expression of the p53 gene was similarly assessed by immunohistostaining.

Results: Injection of 10 μg TNF-α into the tumor-bearing mice reduced the number of endothelial cells in the blood microvessels by 46% on day 3 post-injection which was accompanied by an increase (by 37%) in the expression of p53 in these cells. It also inhibited tumor growth compared to the HBSS-injected group starting at 17 days post-cytokine injection.

Discussion: The antitumor in vivo effect exerted by TNF-α on established murine sarcoma s.c. tumors may be due to an earlier effect of the cytokine on the tumor's blood microvessels, probably through an apoptotic mechanism involving the p53 gene.

Thalidomide, dexamethasone and lovastatin with autologous stem cell transplantation as a salvage immunomodulatory therapy in patients with relapsed and refractory multiple myeloma

The treatment of patients with multiple myeloma usually includes many drugs including thalidomide, lenalidomide and bortezomib. Lovastatin and other inhibitors of HMG-CoA reductase demonstrated to exhibit antineoplasmatic and proapoptotic properties in numerous in vitro studies involving myeloma cell lines. We treated 91 patients with relapsed or refractory multiple myeloma with thalidomide, dexamethasone and lovastatin (TDL group, 49 patients) or thalidomide and dexamethasone (TD group, 42 patients). A clinical response defined of at least 50% reduction of monoclonal band has been observed in 32% of TD patients and 44% of TDL patients. Prolongation of overall survival and progression-free survival in the TDL group as compared with the TD group has been documented. The TDL regimen was safe and well tolerated. The incidence of side effects was comparable in both groups. Plasma cells have been cultured in vitro with thalidomide and lovastatin to assess the impact of both drugs on the apoptosis rate of plasma cells. In vitro experiments revealed that the combination of thalidomide and lovastatin induced higher apoptosis rate than apoptosis induced by each drug alone. Our results suggest that the addition of lovastatin to the TD regimen may improve the response rate in patients with relapsed or refractory myeloma.

VEGF targeted therapy in acute myeloid leukemia

The cooperation of two classes of mutations in hematopoietic cells is hypothesized in a multistep pathogenesis model of acute myeloid leukemia (AML). Class I mutations confer a proliferative and/or survival advantage, whereas Class II mutations block hematopoietic differentiation and impair apoptosis in AML cells. In addition to these two classes of mutations, a relevant role for angiogenesis in the pathophysiology of AML has been recently proposed. The recognition that the vascular endothelial growth factor (VEGF) pathway is a key regulator of angiogenesis has led to the development of several VEGF-targeted approaches. These include neutralizing antibodies, VEGF traps or selective tyrosine kinase inhibitors for VEGFRs. Other drugs that indirectly affect VEGF pathway, such as statins or arsenic trioxide, also have been shown to possess antiangiogenic activity in leukemias. The benefits of these VEGF targeted agents and their current stage of development as novel anti-antiangiogenic therapies in AML are discussed in this review.

Statins can modulate effectiveness of antitumor therapeutic modalities

Despite significant, frequently very strong, antiproliferative and tumoricidal effects of statins demonstrated in vitro, their antitumor effects in animal models are modest, and their efficacy in clinical trials has not been proven. As such, statins seem unlikely to be ever regarded as antitumor agents. However, statins are regularly taken by many elderly cancer patients for the prevention of cardiovascular events. Owing to their pleiotropic effects in normal and tumor cells, statins interact in various ways with many antitumor treatment modalities, either potentiating or diminishing their effectiveness. Elucidation of these interactions might affect the choice of treatment to be planned in cancer patients as some combinations might be contraindicated, whereas others might elicit potentiated antitumor effects but at a cost of increased general toxicity. Some other combinations might induce either comparable or even stronger antitumor effects, but with a beneficial concomitant reduction of specific side effects. Most of the studies reviewed in this article have been carried in vitro or in experimental tumor models, but clinical relevance of the findings is also discussed.

Statins May Reduce Breast Cancer Risk, Particularly Hormone Receptor-Negative Disease

Estrogen and progesterone receptor-negative breast cancer disproportionately affects young women and African Americans, has a poor prognosis, and lacks an effective chemoprevention agent. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, known as "statins," are appealing candidate agents for breast cancer chemoprevention because of their demonstrated safety after decades of widespread use. In preclinical studies, statins inhibit multiple cancer-associated pathways in both hormone receptor (HR)-negative and HR-positive cell lines. Epidemiologic studies of statins and breast cancer show inconsistent results, with some suggesting a reduction in HR-negative breast cancer incidence in lipophilic statin users. However, large meta-analyses show no association between statin use and overall risk of breast cancer, although most did not evaluate tumor HR status. Multiple phase 1 and 2 prevention studies of statins for breast cancer risk reduction are ongoing. If results are promising, they may justify a randomized trial of statins for breast cancer chemoprevention, with a focus on HR-negative disease.

Dual roles of tumor necrosis factor-alpha receptor-1 in a mouse model of hindlimb ischemia

Signals in the tumor necrosis factor alpha (TNF-alpha) pathway are upregulated after ischemia, yet its role in peripheral ischemia remains unclear. We investigated the effect of TNF-alpha receptor 1 (TNFR-1) in acute limb ischemia of TNFR-1 knockout (TNFR-1-/-) and wild type (WT, TNFR-1+/+) mice. Laser Doppler scanning showed that although pre-ischemia blood flow levels were similar in these mice, the limb reperfusion after ischemia was significantly higher in TNFR-1-/- mice 1-7 days after injury. Consistently, fewer TUNEL-positive cells, less DNA fragmentation, and a lower ischemic score were detected in the TNFR-1-/- group when compared to WT controls. Western blot analysis revealed less expression of pro-apoptotic markers Bax and cleaved caspase-3 in TNFR-1-/- mice 1 day after ischemia, supporting the hypothesis that the absence of TNFR-1 results in a reduction of apoptosis. The rate of post-ischemia amputation was 50% in WT mice versus 0% in TNFR-1-/- mice. However, immunohistochemical co-staining of microvessel marker CD31 and cellular proliferation marker BrdU 21 days after ischemia showed an impaired angiogenic activity in the TNFR-1-/- mice. These data were supported by Western blot analysis, which indicated a decreased expression of angiopoietin-1 (Ang-1) and its receptor Tie-2 in TNFR-1-/- mice. Our results suggest that a deficiency in TNFR-1 prevents the activation of death-related proteins downstream to TNF-alpha and attenuates apoptosis in acute limb ischemia, but the lack of TNFR-1 signaling hinders the belated angiogenesis mediated by the Ang-1/Tie-2 pathway.

Synergistic anti-tumor efficacy of lovastatin and protein kinase C-beta inhibitor in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is characterized by hypervascularity and chemoresistance. Protein kinase C (PKC) participates in cancer progression by enhancing anti-apoptotic signals, angiogenesis, and chemoresistance. Statins have a selective anti-cancer effect due to over-expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR) in cancer cells, but statins may also activate PKC. Thus, we hypothesized that simultaneous treatment with statin and PKC inhibitor might synergistically enhance their anti-tumor efficacies against HCCs.

METHODS

Hepatocellular carcinoma cell growth was assessed using MTS assays, apoptotic cell death by DAPI staining, and apoptotic signaling cascades were explored by immunoblotting. An in vivo model of HCC was established in C3H mice intradermally implanted with MH134 cells. Lovastatin and/or a PKC inhibitor (enzastaurin) was subsequently administered. Anti-tumor efficacies were evaluated by measuring tumor volumes and quantifying apoptotic cells and microvessel densities (MVD).

RESULTS

Co-treatment with lovastatin and enzastaurin was found to synergistically suppress HCC cell growth in vitro. Lovastatin induced HCC cellular apoptosis by activating mitochondrial apoptotic signals, and although enzastaurin alone did not induce apoptosis, its addition significantly enhanced lovastatin-induced apoptosis. This enhanced apoptosis was attributed to increased caspase-9 activation in these cells. Moreover, tumor growth was significantly suppressed in mice co-treated with lovastatin and enzastaurin, and percentages of TUNEL-positive cells were significantly increased and MVDs were significantly decreased in those mice.

CONCLUSION

Combinatorial treatment with statin and PKC inhibitor was found to enhance anti-tumor efficacy in vivo and in vitro. Further studies are warranted to prove anti-tumor efficacy of this potential therapy in human HCCs.

Differences in antitumor effects of various statins on human pancreatic cancer

Statins are widely used for the treatment of hypercholesterolemia. However, their inhibitory action on HMG-CoA reductase also results in the depletion of intermediate biosynthetic products, which importantly contribute to cell proliferation. The aim of the present study was to compare the effects of the individual commercially available statins on experimental pancreatic cancer. The in vitro effects of individual statins (pravastatin, atorvastatin, simvastatin, lovastatin, cerivastatin, rosuvastatin and fluvastatin) on the viability of human pancreatic cancer were evaluated in CAPAN-2, BxPc-3 and MiaPaCa-2 cell lines. The in vivo experiments were performed on nude mice xenotransplanted with CAPAN-2 cells. The mice received oral treatments either with a placebo, or with the statins mentioned earlier in a daily dose corresponding to a hypocholesterolemic dose in humans. The effect of these statins on the intracellular Ras protein, trafficking in MiaPaCa-2 transfected cells, was also investigated. Substantial differences in the tumor-suppressive effects of all statins were detected in both in vitro and in vivo experiments. While simvastatin exerted the highest tumor-suppressive effects in vitro, rosuvastatin (p = 0.002), cerivastatin (p = 0.002) and fluvastatin (p = 0.009) were the most potent compounds in an animal model. All statins (except pravastatin) inhibited intracellular Ras protein translocation. In summary, substantial tumor-suppressive effects of various statins on the progression of experimental pancreatic adenocarcinoma were demonstrated, with marked differences among individual statins. These results support greatly the potential of statins for the chemoadjuvant treatment of pancreatic cancer.

Lovastatin enhances phenylbutyrate-induced MR-visible glycerophosphocholine but not apoptosis in DU145 prostate cells

In this study the effects of lovastatin on DU145 prostate cancer cells treated with phenylbutyrate (PB) was investigated in order to determine the NMR-detectable metabolic changes resulting from the cooperative activity of these two agents. DU145 cells were perfused with PB in the presence or absence of 10 microM of the HMG-CoA reductase inhibitor lovastatin, and the results monitored by 31P and diffusion-weighted 1H NMR spectroscopy. Lovastatin had additive effects on the PB-induced NMR-visible total choline in 1H spectra, and glycerophosphocholine in 31P spectra but no significant effect on NMR-visible lipid. Moreover, lovastatin had no effect on the ability of PB to either promote the formation of oil red O-detectable lipid droplets or arrest the cell cycle. The most remarkable observations from these studies were that lovastatin enhanced the increase in glycerophosphocholine while reversing late markers of apoptosis and the loss of NTP caused by PB. These results identify a branch point separating the neutral lipid production and the apoptotic cell death caused by the actions of differentiating agents.

Human umbilical vein endothelial cells and human dermal microvascular endothelial cells offer new insights into the relationship between lipid metabolism and angiogenesis

Human umbilical vein endothelial cells (HUVECs) have played a major role as a model system for the study of the regulation of endothelial cell function and the role of the endothelium in the response of the blood vessel wall to stretch, shear forces, and the development of atherosclerotic plaques and angiogenesis. Here, we use HUVECs and human microvascular endothelial cells to study the role of the HMG-CoA reductase inhibitor, simvastatin, and the small GTP-binding protein Rho in the regulation of angiogenesis. Simvastatin inhibited angiogenesis in response to FGF-2 in the corneal pocket assay of the mouse and in vascular endothelial growth factor (VEGF)-stimulated angiogenesis in the chick chorioallontoic membrane. Furthermore, simvastatin inhibited VEGF-stimulated tube formation by human dermal microvascular endothelial cells and the formation of honeycomb-like structures by HUVECs. The effect was dose-dependent and was not secondary to apoptosis. Geranylgeranyl-pyrophosphate (GGPP), a product of the cholesterol metabolic pathway that serves as a substrate for the posttranslational lipidation of RhoA, was required for membrane localization, but not farnesylpyrophosphate (FPP), the substrate for the lipidation of Ras. Furthermore, GGTI, a specific inhibitor of GGPP, mimicked the effect of simvastatin of tube formation and the formation of honeycombs whereas FTI, a specific inhibitor of the farnesylation of Ras, had no effect. Adenoviral expression of a DN-RhoA mutant mimicked the effect of simvastatin on tube formation and the formation of honeycombs, whereas a dominant activating mutant of RhoA reversed the effect of simvastatin on tube formation. Finally, simvastatin interfered with the membrane localization of RhoA with a dose-dependence similar to that for the inhibition of tube formation. Simvastatin also inhibited the VEGFstimulated phosphorylation of the VEGF receptor KDR, and the tyrosine kinase FAK, which plays a role in cell migration. These data demonstrate that simvastatin interfered with angiogenesis via the inhibition of RhoA. Data supporting a role for angiogenesis in the development and growth of atherosclerotic plaques suggest that this antiangiogenic effect of Statins might prevent the progression of atherosclerosis via the inhibition of plaque angiogenesis.

Nitropravastatin stimulates reparative neovascularisation and improves recovery from limb Ischaemia in type-1 diabetic mice

BACKGROUND AND PURPOSE

Mature endothelial cells and their progenitors are dysfunctional in diabetes, resulting in deficient neovascularisation following arterial occlusion. This study aimed to evaluate the therapeutic activity of a nitric oxide (NO) releasing statin in the setting of experimental diabetes and peripheral ischaemia.

EXPERIMENTAL APPROACH

The effects of NCX 6550, an NO-releasing pravastatin derivative, on angiogenesis in ischaemic limbs was studied in normoglycaemic mice or mice made diabetic by treatment with streptozotocin (STZ). Control mice received an equimolar dosage of the parent statin compound, pravastatin. The therapeutic action of NCX 6550 was also tested in mice lacking the gene for endothelial nitric oxide synthase (eNOS).

KEY RESULTS

In normoglycaemic or STZ-diabetic CD1 mice, only NCX 6550 stimulated skeletal muscle revascularisation. In addition, NCX 6550 induced greater improvement in limb reperfusion and salvage, than pravastatin. The number of circulating endothelial progenitor cells was decreased in STZ-diabetic mice, this defect being prevented by NCX 6550 and, to a lesser extent by pravastatin. In vitro, high glucose concentrations reduced the migratory capacity of endothelial progenitor EPCs, which was partly reversed by preincubation with pravastatin and completely reversed by NCX 6550. The postischaemic recovery of eNOS knockout mice was severely impaired as a consequence of depressed angiogenesis and this recovery was improved by treatment with NCX 6550, but not with pravastatin.

CONCLUSIONS AND IMPLICATIONS

These findings indicate that incorporation of a bioactive NO moiety improves the therapeutic profile of statins for the treatment of peripheral vascular disease.

Cardiovascular disease could be contained based on currently available data!

Largely due to better control of infectious diseases and significant advances in biomedical research, life expectancy worldwide has increased dramatically in the last three decades. However, as the average age of the population has risen, the incidence of chronic age-related diseases such as arthritis, Alzheimer's, Parkinson's, cardiovascular disease, cancer, osteoporosis, benign prostatic hyperplasia, and late-onset diabetes have increased and have become serious public health problem, as well. The etiology of these disorders is still incompletely understood, therefore, neither preventive strategies nor long-term effective treatment modalities are available for these disorders. In keeping with the aforementioned, the ultimate goal in cardiovascular research is to prevent the onset of cardiovascular episodes and thereby allow successful ageing without morbidity and cognitive decline. Herein, I argue that cardiovascular episodes could be contained with relatively simple approaches. Cardiovascular disorder is characterized by cellular and molecular changes that are commonplace in age-related diseases in other organ system, such alterations include increased level of oxidative stress, perturbed energy metabolism, and "horror autotoxicus" largely brought about by the perturbation of ubiquitin -proteasome system, and excessive oxidative stress damage to the cardiac muscle cells and tissues, and cross-reactions of specific antibodies against human heat shock protein 60 with that of mycobacterial heat shock protein 65. "Horror autotoxicus", a Latin expression, is a term coined by Paul Ehrlich at the turn of the last century to describe autoimmunity to self, or the attack of "self" by immune system, which ultimately results to autoimmune condition. Based on the currently available data, the risk of cardiovascular episodes and several other age-related disorders, including cancer, Alzheimer's disease and diabetes, is known to be influenced by the nature and level of food intake. Now, a wealth of scientific data from studies of rodents and monkeys has documented the significant beneficial effects of calorie restriction (CR) or dietary restriction (DR), and multiple antioxidant agents in extending life span and reducing the incidence of progeroid-related diseases. Reduced levels of cellular oxidative stress, protection of genome from deleterious damage, detoxification of toxic molecules, and enhancement of energy homeostasis, contribute to the beneficial effects of dietary restriction and multiple antioxidant agents. Recent findings suggest that employment of DR and multiple antioxidant agents (including, catalase, glutathione peroxidase, CuZn superoxide dismutase, and Mn superoxide dismutase = enzymes forming the primary defense against oxygen toxicity), and ozone therapy may mount an effective resistance to pathogenic factors relevant to the pathogenesis of cardiovascular episodes. Hence, while further studies will be needed to establish the extent to which CR and multiple antioxidant agents will reduce incidence of cardiovascular episodes in humans, it would seem prudent to recommend CR and multiple antioxidant agents as widely applicable preventive approach for cardiovascular disorders and other progeroid-related disorders.

Simvastatin potentiates tumor necrosis factor α-mediated apoptosis of human vascular endothelial cells via the inhibition of the geranylgeranylation of RhoA

HMG-CoA reductase inhibitors (statins) are widely used in the treatment and prevention of atherosclerosis. Here we demonstrate that the HMG-CoA reductase inhibitor simvastatin potentiates TNFalpha-mediated apoptosis and TNFalpha signaling in human umbilical vein endothelial cells (HUVECs). While 2.5 microM simvastatin or 40 ng/ml TNFalpha alone had only a small effect on apoptosis in HUVECs, co-incubation with simvastatin and TNFalpha markedly increased apoptosis in a time- and dose-dependent manner as measured by FACS analysis of propidium iodide-stained cells. Geranylgeraniol, which serves as a substrate for the geranylgeranylation of small GTP binding proteins such as RhoA, which is required for the function and membrane localization of Rho, reversed the effect of simvastatin on apoptosis. GGTI, an inhibitor of protein geranylgeranylation, mimicked the effect of simvastatin on apoptosis and interfered with the membrane localization of RhoA. Furthermore, simvastatin increased the expression of the TNFalpha type I receptor (TNFalphaRI) with a dose dependence and a dependence on geranylgeranylation similar to that demonstrated for the potentiation of TNFalpha-mediated apoptosis. Adenoviral expression of a dominant-negative RhoA mimicked the effect of simvastatin on the expression of TNFalphaRI, while adenoviral expression of a dominant-activating RhoA mutant reversed the effect of simvastatin on the expression of TNFalphaRI. Simvastatin also potentiated TNFalpha signaling as determined by increased TNFalpha-mediated E-selectin expression. These data support the conclusion that TNFalpha signaling is under the negative control of RhoA and that statins potentiate TNFalpha signaling at least in part via interference with RhoA inhibition of TNFalpha type I receptor expression.

Flavonoids and vitamin E reduce the release of the angiogenic peptide vascular endothelial growth factor from human tumor cells

Neoangiogenesis is required for tumor development and progression. Many solid tumors induce vascular proliferation by production of angiogenic factors, prominently vascular endothelial growth factor (VEGF). Because nutrition is a causative factor for tumor prevention and promotion, we determined whether secondary plant constituents, i.e., flavonoids, tocopherols, curcumin, and other substances regulate VEGF in human tumor cells in vitro. VEGF release (concurrent with synthesis) from MDA human breast cancer cells and, for comparison, U-343 and U-118 glioma cells was measured by ELISA. Of 21 compounds tested, 9 showed significant inhibitory activity at 0.1 micromol/L in MDA human breast cancer cells. The rank order of inhibitory potency was naringin > rutin > alpha-tocopheryl succinate (alpha-TOS) > lovastatin > apigenin > genistein > alpha-tocopherol >or= kaempferol > gamma-tocopherol; chrysin and curcumin were inactive except at a concentration of 100 micromol/L. Glioma cells were similarly sensitive, with U343 more than U118, especially for alpha-TOS and tocopherols. Among the tocopherol derivatives, alpha-TOS (0.1 micromol/L) was the most effective in reducing VEGF release. Overall, the glycosylated flavonoids (i.e., naringin, a constituent of citrus fruits, and rutin, a constituent of cranberries) induced the greatest response to treatment at the lowest concentration in MDA human breast cancer cells. Inhibition of VEGF release by flavonoids, tocopherols, and lovastatin in these models of neoplastic cells suggests a novel mechanism for mammary cancer prevention.

Anti-angiogenic and anti-inflammatory effects of statins: relevance to anti-cancer therapy

Angiogenesis is indispensable for the growth of solid tumors and angiogenic factors are also involved in the progression of hematological malignancies. Targeting the formation of blood vessels is therefore regarded as a promising strategy in cancer therapy. Interestingly, besides demonstration of some beneficial effects of novel anti-angiogenic compounds, recent data on the activity of already available drugs point to their potential application in anti-angiogenic therapy. Among these are the statins, the inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Statins are very efficient in the treatment of hypercholesterolemia in cardiovascular disorders; however, their effects are pleiotropic and some are not directly related to the inhibition of cholesterol synthesis. Some reports particularly highlight the pro-angiogenic effects of statins, which are caused by low, nanomolar concentrations and are regarded as beneficial for the treatment of cardiovascular diseases. On the other hand, the anti-angiogenic activities, observed at micromolar concentrations of statins, may be of special significance for cancer therapy. Those effects are caused by the inhibition of both proliferation and migration and induction of apoptosis in endothelial cells. Moreover, the statin-mediated inhibition of vascular endothelial growth factor synthesis, the major angiogenic mediator, may contribute to the attenuation of angiogenesis. It has been suggested that the anti-cancer effect of statins can be potentially exploited for the cancer therapy. However, several clinical trials aimed at the inhibition of tumor growth by treatment with very high doses of statins did not provide conclusive data. Herein, the reasons for those outcomes are discussed and the rationale for further studies is presented.

Cutaneous melanoma: pathogenesis and rationale for chemoprevention

OBJECTIVE

To critically review aspects of melanoma pathogenesis that lend themselves to a chemoprevention strategy. To discuss potential candidate chemoprevention agents with an emphasis on the lipid lowering drugs, the statins, currently, the most promising agents.

DATA SOURCES

A retrospective review of the literature.

STUDY SELECTION

Studies included those relevant to melanoma pathogenesis, to the scientific rationale of chemoprevention, and pertinent epidemiologic, pre-clinical, and clinical studies. The referenced study designs and methodologies varied.

DATA EXTRACTION AND SYNTHESIS

Data were extracted by two reviewers, and the main results are presented in a quantitative descriptive manner.

CONCLUSION

Melanoma is a preventable disease by altering behavior (sun exposure) among at-risk individuals. There is also considerable evidence to suggest that melanoma development may be prevented or delayed by drugs of sufficiently low toxicity to make clinical trials of chemoprevention feasible and potentially successful. Among potential candidate agents, statins have compelling data for long-term safety and sufficient pre-clinical and clinical evidence for efficacy to justify their evaluation in well-designed trials in high-risk individuals, incorporating intermediate biologic endpoints.

The potential of statins as part of anti-cancer treatment

Statins are known to reduce mortality related to cardiovascular diseases. In recent years, evidence has accumulated that statins also exert anti-tumour activity for which numerous potential underlying mechanisms of action have been suggested. Accordingly, several case-control studies showed a reduction in cancer incidence in patients treated with statins. Furthermore, statins interact synergistically with several anti-tumour treatments in preclinical studies. Until now, only a few clinical studies are available that explore the optimal dose, feasibility, and efficacy of statins applied as single agents to control the growth of existing tumours. Studies investigating statins as part of a multi-drug regimen are completely lacking. Nevertheless, the interesting pre-clinical anti-tumour activity of statins combined with a favourable toxicity profile warrant their further development as anti-tumour agents, in particular as part of multi-drug regimens.

Functional Interplay Between the Macrophage Scavenger Receptor Class B Type I and Pitavastatin (NK-104)

Background— Scavenger receptor class B type I (SR-BI), a receptor for high-density lipoprotein (HDL), plays an important role in the bidirectional cholesterol exchange between cells and HDL particles and the atherosclerotic lesion development. Enhancement of SR-BI expression significantly reduces, whereas lack of SR-BI expression accelerates, the atherosclerotic lesion development in proatherogenic mice. Statins, a class of inhibitors for 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, significantly suppress de novo cholesterol synthesis and reduce the incidence of coronary heart disease. Statins also display multiple pleiotropic effects independently of cholesterol synthesis in the vascular cells. Here, we investigated the effects of pitavastatin (NK-104), a newly synthesized statin, on macrophage SR-BI expression.

Methods and Results— We found that pitavastatin significantly increased SR-BI mRNA and protein expression in a macrophage cell line in a concentration- and time-dependent manner. It also increased SR-BI expression in both mouse peritoneal and human monocyte-derived macrophages. Associated with increased SR-BI expression, pitavastatin enhanced macrophage HDL binding, uptake of [ 14 C]cholesteryl oleate/HDL, and efflux of [ 3 H]cholesterol to HDL. Pitavastatin abolished the inhibition of macrophage SR-BI expression by cholesterol biosynthetic intermediates. It also restored SR-BI expression inhibited by lipopolysaccharide and tumor necrosis factor-α through its inactivation of the transcription factor nuclear factor-κB.

Conclusions— Our data demonstrate that pitavastatin can stimulate macrophage SR-BI expression by reduction of cholesterol biosynthetic intermediates and antiinflammatory action and suggest additional pleiotropic effects of statins by which they may reduce the incidence of coronary heart disease.

The association between 3-hydroxy-3-methylglutaryl conenzyme A inhibitor use and breast carcinoma risk among postmenopausal women: a case-control study

BACKGROUND

Statin use has increased dramatically in the U.S. in the past decade. Animal and mechanistic studies suggested that statins may have an inhibitory effect on cancer proliferation, including breast carcinoma. However, statins have been found to be carcinogenic in rodents and one clinical trial found an excess of breast carcinoma cases in the treatment group.

METHODS

The current study assessed whether the use of statins altered the risk of breast carcinoma in older women. The population-based, case-control study comprised female residents from three western Washington State counties. Cases included 975 women identified from the Cancer Surveillance System who were diagnosed with primary invasive breast carcinoma between 1997-1999, whose names appeared on a list of Social Security recipients provided by the Centers for Medicare and Medicaid Services. The cases were ages 65-79 years at the time of diagnosis. The comparison group was comprised of 1007 women without breast carcinoma who were randomly selected from the same list of Social Security recipients. Information pertaining to statin use, medical history, and health behaviors was ascertained through an in-person interview.

RESULTS

Compared with nonusers, women who were currently using statins or had ever used statins were not found to be at an increased risk for breast carcinoma (odds ratios [OR] = 0.9; 95% confidence interval [95% CI], 0.7-1.2). There was some indication that long-term statin use (> 5 years) was related to a slight decrease in breast carcinoma risk (OR = 0.7; 95% CI, 0.4-1.0).

CONCLUSIONS

The results of the current study provided some degree of reassurance to the increasing numbers of women using statins that such use is not associated with an increased risk of breast carcinoma. Although the data gave some support to a reduced risk of breast carcinoma among long-term users of statins, further research is needed to confirm this association.

Stimulation of angiogenesis by Ras proteins

Cells that have acquired a proliferative advantage form islets of hyperplasia during the initial stages of tumor development. Like normal cells, they require oxygen and nutrients to survive and proliferate. The centre of the islets is characterized by low oxygen pressure and low pH, conditions that stimulate the sprouting of new capillaries from nearby vascular beds. It is now well established that neovascularisation (angiogenesis) of the hyperplasias is essential for further development of the tumor. The family of ras oncogenes promotes the initiation of tumor growth by stimulating tumor cell proliferation, but also ensures tumor progression by stimulating tumor-associated angiogenesis. Oncogenic Ras proteins stimulate a number of effector pathways that culminate in the transcriptional activation of genes that control angiogenesis. Moreover, Ras signaling leads to stabilization of the produced mRNAs and, possibly, to enhanced initiation of their translation. In this review we describe the mechanisms that underlie Ras regulation of vascular endothelial growth factor (VEGF), cyclooxygenases (COX-1/-2), thrombospondins (TSP-1/-2), urokinase plasminogen activator (uPA) and matrix metalloproteases-2 and -9 (MMP-2/-9). As a result of these Ras-regulated changes in gene expression, the tumor cells cause stimulation of endothelial cells in nearby vascular beds (directly via VEGF, and indirectly via COX-produced prostaglandins) and promote remodeling of the extracellular matrix (by lowering TSP and increasing uPA/MMPs). The latter effect makes growth factors available for endothelial cell activation and migration. In addition, tumor cell-activated stromal cells also contribute to the stimulation of angiogenesis by further enhancing the production and secretion of pro-angiogenic factors into the tumor stroma.

Simvastatin inhibits leukocyte accumulation and vascular permeability in the retinas of rats with streptozotocin-induced diabetes

Leukocytes play important roles in the pathogenesis of diabetic retinopathy. Recently, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors have been reported to exert various effects in addition to their lipid-lowering ability. We investigated the effects of simvastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor, on leukocyte-induced diabetic changes in retinas. Diabetes was induced in Long-Evans rats with streptozotocin, and simvastatin administration was begun immediately after the induction of diabetes. Two weeks of treatment with simvastatin suppressed significantly the number of leukocytes adhering to retinal vessel endothelium and the number of leukocytes accumulated in the retinal tissue by 72.9% and 41.0%, respectively (P < 0.01). The expression of intercellular adhesion molecule-1 (ICAM-1) and the CD18 (the common beta-chain of ICAM-1 ligands) were both suppressed with simvastatin. The amount of vascular endothelial growth factor in the retina was attenuated in the simvastatin-treated group. To evaluate the effects of simvastatin on leukocyte-induced endothelial cell damage, vascular permeability in the retina was measured with fluorescein-labeled dextran. Treatment with simvastatin markedly reduced retinal permeability (P = 0.014). This suggests that simvastatin attenuates leukocyte-endothelial cell interactions and subsequent blood-retinal barrier breakdown via suppression of vascular endothelial growth factor-induced ICAM-1 expression in the diabetic retina. Simvastatin may thus be useful in the prevention of diabetic retinopathy.

The cardioprotective effects of statins

In addition to their lipid-modulating properties, statins have a large number of beneficial cardiovascular effects that have emerged over time and that were not anticipated during drug development. The lipid and nonlipid effects act in a concerted way to reduce the ischemic burden of the myocardium and to protect it against injury. By acting on the vessel wall, statins may prevent lesion initiation and repair injuries, enhance myocardial perfusion, slow lesion progression, and prevent coronary occlusion. They may also directly reduce myocardial damage, favor myocardial repair, and protect against immune injury. This review focuses on properties of statins that contribute to their cardioprotective effect. The first section includes information on modulation of vascular tone, endothelial permeability and function, inhibition of complement injury, curbing of foam cell formation, antioxidant and anti-inflammatory properties, and profibrinolytic and anticoagulant activities. The second section relates to reduction of myocardial necrosis, myocardial hypertrophy, blood pressure, and heart failure, as well as mobilization of endothelial progenitor cells for repair, angiogenic effects, and immunomodulation. In many instances, results of in vitro and animal studies have raised expectations and prompted studies in humans. Several clinical trials have confirmed these expectations and have strengthened the value of statins as valuable antiatherosclerotic and cardioprotective agents.

Statins differentially regulate vascular endothelial growth factor synthesis in endothelial and vascular smooth muscle cells

OBJECTIVES

HMG-CoA reductase inhibitors (statins) can modulate the formation of new blood vessels, but the reports on their contribution to angiogenesis are contradictory. Therefore, we investigated whether the effect of statins is dependent either on the concentration of the drug or on the cell type.

METHODS AND RESULTS

Under basal conditions human vascular smooth muscle cells (HVSMC) and microvascular endothelial cells (HMEC-1) constitutively generate and release vascular endothelial growth factor (VEGF). In contrast, primary macrovascular endothelial cells (HUVEC) produce minute amounts of VEGF. Different statins (atorvastatin, simvastatin and lovastatin, 1-10 micromol/l) significantly reduced basal and cytokine-, nitric oxide- or lysophosphatidylcholine (LPC)-induced VEGF synthesis in HMEC-1 and HVSMC. Interestingly, at the same concentrations statins upregulated VEGF generation in HUVEC. Furthermore, statins exerted dual, concentration-dependent influence on angiogenic activities of HUVEC as determined by tube formation assay. At low concentrations (0.03-1 micromol/l) the pro-angiogenic activity of statins is prevalent, whereas at higher concentrations statins inhibit angiogenesis, despite increasing VEGF synthesis.

CONCLUSION

Our data show that statins exert concentration- and cell type-dependent effects on angiogenic activity of endothelial cells and on VEGF synthesis. The data are of relevance for elucidating the differential activity of statins on angiogenesis in cardiovascular diseases and cancer.

Alzheimer's disease and angiogenesis

Despite enormous investigative efforts, the pathological basis for Alzheimer's disease remains unclear. Suggested mechanisms for the disorder include cerebral hypoperfusion, inflammation, gene polymorphisms, and molecular lesions in the brain. In this Hypothesis, we argue that the vascular endothelial cell has a central role in the progressive destruction of cortical neurons in Alzheimer's disease. In Alzheimer's disease, the brain endothelium secretes the precursor substrate for the beta-amyloid plaque and a neurotoxic peptide that selectively kills cortical neurons. Large populations of endothelial cells are activated by angiogenesis due to brain hypoxia and inflammation. Results of epidemiological studies have shown that long-term use of non-steroidal anti-inflammatory drugs, statins, histamine H2-receptor blockers, or calcium-channel blockers seems to prevent Alzheimer's disease. We think this benefit is largely due to these drugs' ability to inhibit angiogenesis. If Alzheimer's disease is an angiogenesis-dependent disorder, then development of antiangiogenic drugs targeting the abnormal brain endothelial cell might be able to prevent and treat this disease. We suggest several laboratory and clinical approaches for testing our hypothesis.

Mevastatin can increase toxicity in primary AMLs exposed to standard therapeutic agents, but statin efficacy is not simply associated with ras hotspot mutations or overexpression

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is a rate-limiting enzyme in the mevalonate biochemical pathway and HMG-CoA reductase inhibitors (statins) show toxicity for certain tumors, including acute myeloid leukemia (AML). This toxicity has been attributed to statin inhibition of Ras isoprenylation in tumors like AML where oncogenic ras mutations and/or overexpression are common. We show that mevastatin kills certain AML cell lines and is more toxic to a majority of primary AML cell samples than to myeloid cells in bone marrow (BM) samples from normal donors, and that mevastatin can produce more than additive kill with standard chemotherapeutics. Mevastatin reduces Ras membrane localization, but statin sensitivity in primary AML cells is not consistently associated with ras mutations nor with Ras overexpression, suggesting that another mevalonate pathway by-product(s) is the statin target in at least some AMLs.

Chemoprevention of melanoma: an unexplored strategy

The incidence and mortality of melanoma has continued to increase steeply-faster than most other preventable cancers in the United States. Current sun protection strategies have yet to reduce this increased incidence and mortality. Chemoprevention, defined as the use of natural or synthetic agents to delay, reverse, suppress, or prevent premalignant molecular or histologic lesions from progressing to invasive cancer, has become an important area in cancer research. Melanoma, with its associated risk factors and its known precursors or premalignant lesions, should lend itself well to chemoprevention. Prerequisites for this research should include determination of the molecular mechanisms of ultraviolet (UV) melanomagenesis; use of animal models to test candidate prevention agents; use of molecular and histologic markers as surrogate end point markers; collection of epidemiological, basic science, or in vitro data on potential chemoprevention candidate drugs; and selection of a high-risk patient population in which to carry out clinical chemoprevention trials. Preliminary data available in all these areas are reviewed. Possible mechanisms and molecular targets for the chemoprevention of UV-induced melanoma are discussed. This recent information should stimulate research in the chemoprevention of melanoma.

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors interfere with angiogenesis by inhibiting the geranylgeranylation of RhoA

Angiogenesis is implicated in the pathogenesis of cancer, rheumatoid arthritis, and atherosclerosis and in the treatment of coronary artery and peripheral vascular disease. Here, cholesterol-lowering agents, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, are shown to interfere with angiogenesis. In vivo, the HMG-CoA reductase inhibitor simvastatin dose-dependently inhibited capillary growth in both vascular endothelial growth factor-stimulated chick chorioallantoic membranes and basic fibroblast growth factor-stimulated mouse corneas. In vitro, the development of tubelike structures by human microvascular endothelial cells cultured on 3D collagen gels was inhibited at simvastatin concentrations similar to those found in the serum of patients on therapeutic doses of this agent. HMG-CoA reductase inhibitors interfered with angiogenesis via inhibition of the geranylgeranylation and membrane localization of RhoA. Simvastatin inhibited membrane localization of RhoA with a concentration dependence similar to that for the inhibition of tube formation, whereas geranylgeranyl pyrophosphate, the substrate for the geranylgeranylation of Rho, reversed the effect of simvastatin on tube formation and on the membrane localization of RhoA. Furthermore, tube formation was inhibited by GGTI, a specific inhibitor of the geranylgeranylation of Rho; by C3 exotoxin, which inactivates Rho; and by the adenoviral expression of a dominant-negative RhoA mutant. The expression of a dominant-activating RhoA mutant reversed the effect of simvastatin on tube formation. Finally, HMG-CoA reductase inhibitors inhibited signaling by vascular endothelial growth factor, Akt, and focal adhesion kinase, three RhoA-dependent pathways known to be involved in angiogenesis. This study demonstrates a new relationship between lipid metabolism and angiogenesis and an antiangiogenic effect of HMG-CoA reductase inhibitors with possible important therapeutic implications.

Lovastatin potentiates antitumor activity of doxorubicin in murine melanoma via an apoptosis-dependent mechanism

Lovastatin, a drug successfully used in the clinic to prevent and to treat coronary heart disease, has recently been reported to decrease the incidence of melanoma in lovastatin-treated patients. Lovastatin has also been proved to potentiate antitumor effects of both cisplatin and TNF-alpha in murine melanoma models. Recently, an augmented therapeutic effect of lovastatin and doxorubicin has been reported in 3 tumor models in mice. In our preliminary study lovastatin caused retardation of melanoma growth in mice treated with doxorubicin (Feleszko et al. J Natl Cancer Inst 1998;90:247-8). In the present report, we supplement our preliminary observations and demonstrate in 2 murine and 2 human melanoma cell lines that lovastatin effectively potentiates the cytostatic/cytotoxic activity of doxorubicin in vitro via an augmentation of apoptosis (estimated with PARP-cleavage assay, annexin V assay and TUNEL). The combined antiproliferative activity of lovastatin and doxorubicin was evaluated using the combination index (CI) method of Chou and Talalay, revealing synergistic interactions in melanoma cells exposed to lovastatin and doxorubicin. In B16F10 murine melanoma model in vivo, we have demonstrated significantly increased sensitivity to the combined treatment with both lovastatin (5 mg/kg for 14 days) and doxorubicin (4 x 1 mg/kg) as compared with either agent acting alone. Lovastatin treatment resulted also in significant reduction of the number of experimental metastasis in doxorubicin-treated mice. The results of our studies suggest that lovastatin may enhance the effectiveness of chemotherapeutic agents in the treatment of malignant melanomas.

The cholesterol lowering drug lovastatin induces cell death in myeloma plasma cells

Lovastatin is an irreversible inhibitor of HMG-CoA reductase and blocks the production of mevalonate, a critical compound in the production of cholesterol and isoprenoids. Isoprenylation of target proteins, like the GTP-binding protein Ras, is essential for their membrane localization and subsequent participation in intracellular signaling cascades. Lovastatin effectively decreased the viability of plasma cells from cell lines (n = 10) and myeloma patients' samples (n = 8) in a dose- and time-dependent way. Importantly, co-incubation of lovastatin with dexamethasone had a synergistic effect in inducing plasma cell cytotoxity. This effect was not the consequence of a change in the protein expression levels of Bcl-2 or Bax induced by lovastatin. The decrease in plasma cell viability was the result of induction of apoptosis and inhibition of proliferation. Mevalonate effectively reversed the cytotoxic and cytostatic effects of lovastatin in plasma cells. The cytotoxic activity of lovastatin was higher in Pgp expressing cell lines, but did not correlate with the multidrug resistance (MDR)-related proteins LRP, Bcl-2 and Bax. Lovastatin treatment resulted in a shift of Ras localization from the membrane to the cytosol that was reversed by mevalonate. The data presented in this paper warrant study of lovastatin alone or in combination with therapeutic drugs, in the treatment of myeloma patients.