Effect of simvastatin alone and in combination with cytosine arabinoside on the proliferation of myeloid leukemia cell lines

Application of omics in the diagnosis, prognosis, and treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is the most frequent leukemia in adults with a high mortality rate. Current diagnostic criteria and selections of therapeutic strategies are generally based on gene mutations and cytogenetic abnormalities. Chemotherapy, targeted therapies, and hematopoietic stem cell transplantation (HSCT) are the major therapeutic strategies for AML. Two dilemmas in the clinical management of AML are related to its poor prognosis. One is the inaccurate risk stratification at diagnosis, leading to incorrect treatment selections. The other is the frequent resistance to chemotherapy and/or targeted therapies. Genomic features have been the focus of AML studies. However, the DNA-level aberrations do not always predict the expression levels of genes and proteins and the latter is more closely linked to disease phenotypes. With the development of high-throughput sequencing and mass spectrometry technologies, studying downstream effectors including RNA, proteins, and metabolites becomes possible. Transcriptomics can reveal gene expression and regulatory networks, proteomics can discover protein expression and signaling pathways intimately associated with the disease, and metabolomics can reflect precise changes in metabolites during disease progression. Moreover, omics profiling at the single-cell level enables studying cellular components and hierarchies of the AML microenvironment. The abundance of data from different omics layers enables the better risk stratification of AML by identifying prognosis-related biomarkers, and has the prospective application in identifying drug targets, therefore potentially discovering solutions to the two dilemmas. In this review, we summarize the existing AML studies using omics methods, both separately and combined, covering research fields of disease diagnosis, risk stratification, prognosis prediction, chemotherapy, as well as targeted therapy. Finally, we discuss the directions and challenges in the application of multi-omics in precision medicine of AML. Our review may inspire both omics researchers and clinical physicians to study AML from a different angle.

Exploiting metabolic vulnerabilities for personalized therapy in acute myeloid leukemia

Changes in cell metabolism and metabolic adaptation are hallmark features of many cancers, including leukemia, that support biological processes involved into tumor initiation, growth, and response to therapeutics. The discovery of mutations in key metabolic enzymes has highlighted the importance of metabolism in cancer biology and how these changes might constitute an Achilles heel for cancer treatment. In this Review, we discuss the role of metabolic and mitochondrial pathways dysregulated in acute myeloid leukemia, and the potential of therapeutic intervention targeting these metabolic dependencies on the proliferation, differentiation, stem cell function and cell survival to improve patient stratification and outcomes.

The Roles of Cholesterol and Its Metabolites in Normal and Malignant Hematopoiesis

Hematopoiesis is sustained throughout life by hematopoietic stem cells (HSCs) that are capable of self-renewal and differentiation into hematopoietic progenitor cells (HPCs). There is accumulating evidence that cholesterol homeostasis is an important factor in the regulation of hematopoiesis. Increased cholesterol levels are known to promote proliferation and mobilization of HSCs, while hypercholesterolemia is associated with expansion of myeloid cells in the peripheral blood and links hematopoiesis with cardiovascular disease. Cholesterol is a precursor to steroid hormones, oxysterols, and bile acids. Among steroid hormones, 17β-estradiol (E2) induces HSC division and E2-estrogen receptor α (ERα) signaling causes sexual dimorphism of HSC division rate. Oxysterols are oxygenated derivatives of cholesterol and key substrates for bile acid synthesis and are considered to be bioactive lipids, and recent studies have begun to reveal their important roles in the hematopoietic and immune systems. 27-Hydroxycholesterol (27HC) acts as an endogenous selective estrogen receptor modulator and induces ERα-dependent HSC mobilization and extramedullary hematopoiesis. 7α,25-dihydroxycholesterol (7α,25HC) acts as a ligand for Epstein-Barr virus-induced gene 2 (EBI2) and directs migration of B cells in the spleen during the adaptive immune response. Bile acids serve as chemical chaperones and alleviate endoplasmic reticulum stress in HSCs. Cholesterol metabolism is dysregulated in hematologic malignancies, and statins, which inhibit de novo cholesterol synthesis, have cytotoxic effects in malignant hematopoietic cells. In this review, recent advances in our understanding of the roles of cholesterol and its metabolites as signaling molecules in the regulation of hematopoiesis and hematologic malignancies are summarized.

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.

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.

HMG-CoA reductase inhibitors as adjuvant treatment for hematologic malignancies: what is the current evidence?

Statins have been shown to possess properties that go beyond their lipid-lowering effects. These agents act on the mevalonate pathway and inhibit synthesis of cholesterol, geranylgeranyl pyrophosphate, and farnesyl pyrophosphate, which are necessary for posttranslational modification of the Rho, Rac, and Ras superfamily of proteins. Early phase studies have demonstrated that this modulation of cellular signaling can ultimately exert pro-apoptotic, anti-angiogenic, and immunomodulatory effects, and might even restore chemosensitivity in several hematologic cancers. Nonetheless, these promising preclinical results have not yet migrated from the bench to the bedside as their effectiveness as adjuvant agents in hematologic malignancies is currently uncertain. In the present review, we summarize the existing evidence stemming from preclinical and clinical studies pertaining to the use of statins as adjuvant therapies in hematologic malignancies, and discuss the new insights gained from the ongoing translational research.

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.

Geraniol and simvastatin show a synergistic effect on a human hepatocarcinoma cell line

Simvastatin is a competitive inhibitor of 3-hydroxymethylglutaryl coenzyme A reductase activity, whereas geraniol is a monoterpene with multiple pharmacologic effects on mevalonate metabolism. Both of them inhibit growth and proliferation of many cell lines. The present study was designed to determine the action of geraniol, in combination with simvastatin, by assessing their effects in vitro on human hepatocarcinoma cell line (Hep G2). The treatment of Hep G2 cells with concentrations of simvastatin or geraniol that did not inhibit cell proliferation (5 µmol·l⁻¹ of simvastatin and 50 µmol·l⁻¹ of geraniol) resulted in a significant inhibition of cell proliferation. We also examined the effect of simvastatin, geraniol and the combination of both on the biosynthesis of lipids from [¹⁴C]-acetate. Our results demonstrate that the combination of simvastatin and geraniol synergistically inhibited cholesterol biosynthesis and proliferation of Hep G2 cell line, contributing to a better understanding of the action of a component of essential oils targeting a complex metabolic pathway, which would improve the use of drugs or their combination in the fight against cancer and/or cardiovascular diseases.

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.

Regulation of translocator protein 18 kDa (TSPO) expression in health and disease states

Translocator protein (TSPO) is an 18 kDa high affinity cholesterol- and drug-binding protein found primarily in the outer mitochondrial membrane. Although TSPO is found in many tissue types, it is expressed at the highest levels under normal conditions in tissues that synthesize steroids. TSPO has been associated with cholesterol import into mitochondria, a key function in steroidogenesis, and directly or indirectly with multiple other cellular functions including apoptosis, cell proliferation, differentiation, anion transport, porphyrin transport, heme synthesis, and regulation of mitochondrial function. Aberrant expression of TSPO has been linked to multiple diseases, including cancer, brain injury, neurodegeneration, and ischemia-reperfusion injury. There has been an effort during the last decade to understand the mechanisms regulating tissue- and disease-specific TSPO expression and to identify pharmacological means to control its expression. This review focuses on the current knowledge regarding the chemicals, hormones, and molecular mechanisms regulating Tspo gene expression under physiological conditions in a tissue- and disease-specific manner. The results described here provide evidence that the PKCepsilon-ERK1/2-AP-1/STAT3 signal transduction pathway is the primary regulator of Tspo gene expression in normal and pathological tissues expressing high levels of TSPO.

Osteopontin is a new target molecule for ovarian clear cell carcinoma therapy

Recent studies have demonstrated overexpression of osteopontin (OPN) in ovarian clear cell carcinoma. Here, we revealed the role of OPN in invasiveness in ovarian clear cell carcinoma. We used immunofluorescence analysis to detect OPN in a total of 160 patient-derived specimens. Ovarian clear cell carcinoma cell lines, RMG-1 and TOV-21G, were used to monitor changes in OPN and integrin levels, and cell invasiveness following treatment with OPN, simvastatin, and transfection with siRNA. Immunofluorescence analysis revealed statistically significant differences among the histological groups, and ovarian clear cell carcinoma expressed a strong OPN signal. The OPN receptors, alpha v and 5, and beta 1 and 3 integrins, were increased after treatment with OPN. Invasion assays indicated that OPN enhanced in vitro extracellular matrix invasion dose-dependently in ovarian clear cell carcinoma. Simvastatin significantly reduced expression of OPN and the integrins, and decreased ECM invasion. RNA interference also suppressed ECM invasion. These results suggest that down- or up-regulation of OPN is involved in carcinoma cell invasion. We thus conclude that OPN regulation could have a crucial role in ovarian clear cell carcinoma therapy.

Simvastatin and purine analogs have a synergic effect on apoptosis of chronic lymphocytic leukemia cells

Despite many therapeutic regimens introduced recently, chronic lymphocytic leukemia (CLL) is still an incurable disorder. Thus, there is an urgent need to discover novel, less toxic and more effective drugs for CLL patients. In this study, we attempted to assess simvastatin, widely used as a cholesterol-lowering drug, both as a single agent and in combination with purine analogs-fludarabine and cladribine-in terms of its effect on apoptosis and DNA damage of CLL cells. The experiments were done in ex vivo short-term cell cultures of blood and bone marrow cells from newly diagnosed untreated patients. We analyzed expression of active caspase-3 and the BCL-2/BAX ratio as markers of apoptosis and the expression of phosphorylated histone H2AX (named γH2AX) and activated ATM kinase (ataxia telangiectasia mutated kinase), reporters of DNA damage. Results of our study revealed that simvastatin induced apoptosis of CLL cells concurrently with lowering of BCL-2/BAX ratio, and its pro-apoptotic effect is tumor-specific, not affecting normal lymphocytes. We observed that combinations of simvastatin+fludarabine and simvastatin+cladribine had a synergic effect in inducing apoptosis. Interestingly, the rate of apoptosis caused by simvastatin alone and in combination was independent of markers of disease progression like ZAP-70 and CD38 expression or clinical stage according to Rai classification. We have also seen an increase in γH2AX expression in parallel with activation of ATM in most of the analyzed samples. The results suggest that simvastatin can be used in the treatment of CLL patients as a single agent as well as in combination with purine analogs, being equally effective both in high-risk and good-prognosis patients. One of the mechanisms of simvastatin action is inducing DNA damage that ultimately leads to apoptosis.

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.

Statin Use and Cancer Risk: An Epidemiologic Review

While the beneficial effects of hydroxy-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) on cardiovascular disease are well established, much uncertainty remains about their effects on cancer. The statins inhibit the rate-limiting step in the mevalonate pathway, leading to reduced levels of cholesterol and other molecules of importance for critical cellular processes. A growing body of preclinical data indicates that statins may have antineoplastic properties, but some studies raise the possibility that statins may possess a carcinogenic potential. Clinical and observational studies of the association between statin use and cancer have been inconclusive with regard to any chemopreventive or therapeutic effect, but they do provide reassuring evidence that statins do not appear to be carcinogenic. The reasons for the varying results are unclear but they may relate to methodological issues. Additional studies, including Phase II randomized trials and epidemiological studies with accurate measures of statin use and comprehensive control for confounding factors, are needed to determine the potentially beneficially effects of statins on cancer development and progression.

Statins induce lethal effects in acute myeloblastic leukemia [corrected] cells within 72 hours

HMG-CoA Reductase inhibitors (statins) induce apoptosis in acute myeloid leukemia (AML) cells in vitro; however, the concentrations associated with cell death in AML cells are higher than those clinically tolerated during prolonged therapy. We therefore wished to determine whether short exposures to lovastatin might induce cell death in AML cells at clinically attainable concentrations. The time and concentration dependence of HL60 and U937 cells was determined and showed that cell death was delayed. IC₅₀ values and IC₉₀ values determined on day 6 suggested that the sensitivity of AML cells to statins may occur at lower concentrations than previously reported. After 72 h, mevalonate did not rescue AML cells from cytotoxic concentrations of statins, suggesting that, although cell death was delayed, lovastatin induced lethal effects within 72 h. In conjunction with previously reported Phase I studies, the data presented here suggest that the high-dose, short course statins may be useful for the treatment of patients with AML.

Lovastatin and thalidomide have a combined effect on the rate of multiple myeloma cell apoptosis in short term cell cultures

OBJECTIVE

Multiple myeloma is characterized by an accumulation of plasma cells in bone marrow. Despite many therapeutic regimens introduced recently, the prognosis for patients suffering from treatment-resistant or relapsing multiple myeloma is still very poor. Thus, there is an urgent medical need for novel innovative drugs. Thalidomide is successfully used in resistant or relapsing myeloma patients, being reported to induce apoptosis or G1 growth arrest of myeloma cells and to regulate microvessel density and cytokine secretion. Lovastatin, largely used for the treatment of hypercholesterolemia, is another promising drug in multiple myeloma. High doses of lovastatin have been shown to have antiproliferative effect by inhibition of malignant cell proliferation and inducing programmed cell death.

METHODS

In this study, we tried to assess whether thalidomide and lovastatin had a combined effect on apoptosis of myeloma cells. We analyzed apoptosis induced by mixture of these two drugs in short-term cell culture of myeloma plasmocytes. To assess apoptosis, we used Annexin V and propidium iodide binding. We also examined the regulation of BCL-2 and BAX protein expression in the population of CD138+ plasmocytes. The cells were analyzed with the use of flow cytometry technique. The experiments were done before and after 72 h of cell culture.

RESULTS

We detected a higher rate of apoptosis induced by lovastatin and thalidomide mixture in comparison to apoptosis induced by lovastatin or thalidomide alone. In most patients, the BCL-2/BAX ratio was lower in cell cultures supplemented with mixture of lovastatin and thalidomide in comparison with cell cultures supplemented with lovastatin or thalidomide alone.

CONCLUSION

Based on our research we conclude that the mixture of lovastatin and thalidomide may increase the rate of multiple myeloma cells apoptosis in comparison to the single drug and the precise mechanism of this effect should be approved by further research.

Statins and cholesterol lowering after a cancer diagnosis: why not?

The pleiotropic effects of statins continue to garner attention. One area of interest that requires more attention is their potential, or that of another heart healthy agent, to impact favorably or inhibit the progression of numerous cancers, especially prostate cancer. Statins have accumulated a plethora of data in the area of general cancer cell line inhibition, and the potential to have a synergistic impact in patients receiving a variety of conventional treatments for a diversity of cancers is endorsed at least by laboratory and some preliminary small clinical studies. However, prostate cancer is unique compared to other cancers because, despite a high prevalence, some men choose watchful waiting or no treatment, especially if they are older and/or have a well-differentiated tumor. Thus, prostate cancer is a good candidate for the potential investigation of statins after diagnosis, with or without standard therapy. Regardless, because the number 1 or 2 cause of death in men with prostate cancer is cardiovascular disease than even in the worst-case scenario, these agents appear attractive for more immediate clinical study because they could impact a major cause of morbidity and mortality in these men. It is time to see the forest over the tree, and statins seem to have an argument as good as many other agents for allocating more money and time to test their ability as adjuvant therapy in a randomized trial or, in some cases, of nonaggressive disease as a potential monotherapy.

Evaluation of apoptosis and necrosis induced by statins using fluorescence-enhanced flow cytometry

The purpose of this study was to evaluate the apoptosis and necrosis induced by five kinds of statins in IM-9 human lymphoblasts with fluorescence-enhanced flow cytometry using avidin-biotin complex. IM-9 human lymphoblasts (2 x 10(4) cells/cm2) were seeded into tissue culture plates and incubated with five kinds of statins. Statin-treated cells were first incubated with biotin-annexin V, followed by addition of avidin-FITC and propidium iodide, and then subjected to flow cytometry. The fluorescence intensity was enhanced using an avidin-biotin complex system, resulting in successful separate determination of the statin-induced apoptosis and necrosis by flow cytometry, which enabled us to quantitatively evaluate the statin-induced cell damage. Flow cytometric analysis results in the intensity of statin-induced apoptosis in IM-9 cells as follows: atorvastatin cerivastatin>fluvastatin simvastatin>pravastatin. The intensity of statin-induced necrosis in IM-9 cells was expressed as follows: atorvastatin cerivastatin>fluvastatin simvastatin>pravastatin. The total damage of IM-9 cells induced by five kinds of statins were expressed as the sum of both percentages of apoptosis and necrosis as follows: atorvastatin cerivastatin>fluvastatin simvastatin>pravastatin. Our studies show that fluorescence enhancement with avidin-biotin complex is useful for the identification and quantitation of annexin-positive apoptosis cells and thus, the fluorescence-enhanced flow cytometry was shown to be applicable for screening of statins as new anti-leukemia agents.

Pharmacodynamic effects of high dose lovastatin in subjects with advanced malignancies

Lovastatin, an inhibitor of the rate-limiting enzyme in the cholesterol biosynthetic pathway, hydroxymethylglutaryl coenzyme A reductase, has shown interesting antiproliferative activities in cell culture and in animal models of cancer. The goal of the current study is to determine whether lovastatin bioactivity levels, in a range equivalent to those used in in vitro and preclinical studies, can be safely achieved in human subjects. Here we present the findings from a dose-escalating trial of lovastatin in subjects with advanced malignancies. Lovastatin was administered every 6 h for 96 h in 4-week cycles in doses ranging from 10 mg/m2 to 415 mg/m2. Peak plasma lovastatin bioactivity levels of 0.06-12.3 microM were achieved in a dose-independent manner. Cholesterol levels decreased during treatment and normalized during the rest period. A dose-limiting toxicity was not reached and there were no clinically significant increases in creatine phosphokinase or serum hepatic aminotransferases levels. No antitumor responses were observed. These results demonstrate that high doses of lovastatin, given every 4 h for 96 h, are well-tolerated and in select cases, bioactivity levels in the range necessary for antiproliferative activity were achieved.

Lovastatin alters the isoprenoid biosynthetic pathway in acute myelogenous leukemia cells in vivo

Lovastatin, a competitive inhibitor of hydroxymethylglutaryl coenzyme A reductase (HMGR), is used therapeutically to lower plasma cholesterol levels and has garnered attention for its cytotoxic effects in leukemia cells. In this study, escalating doses of lovastatin were administered to nine patients with acute myelogenous leukemia. Peripheral blood leukemia cells were drawn pre- and post-lovastatin dosing. Plasma lovastatin bioactivity ranged up to 234 nM lovastatin equivalents. Our results show that in vivo lovastatin, at up to 200 mg/dose, induces an increased activity of leukemia cell HMGR and alters leukemia cell proliferation without discernibly altering Ras processing.

Cholesterol and prostate cancer

Cholesterol is a neutral lipid that accumulates in liquid-ordered, detergent-resistant membrane domains called lipid rafts. Lipid rafts serve as membrane platforms for signal transduction mechanisms that mediate cell growth, survival, and a variety of other processes relevant to cancer. A number of studies, going back many years, demonstrate that cholesterol accumulates in solid tumors and that cholesterol homeostasis breaks down in the prostate with aging and with the transition to the malignant state. This review summarizes the established links between cholesterol and prostate cancer (PCa), with a focus on how accumulation of cholesterol within the lipid raft component of the plasma membrane may stimulate signaling pathways that promote progression to hormone refractory disease. We propose that increases in cholesterol in prostate tumor cell membranes, resulting from increases in circulating levels or from dysregulation of endogenous synthesis, results in the coalescence of raft domains. This would have the effect of sequestering positive regulators of oncogenic signaling within rafts, while maintaining negative regulators in the liquid-disordered membrane fraction. This approach toward examining the function of lipid rafts in prostate cancer cells may provide insight into the role of circulating cholesterol in malignant growth and on the potential relationship between diet and aggressive disease. Large-scale characterization of proteins that localize to cholesterol-rich domains may help unveil signaling networks and pathways that will lead to identification of new biomarkers for disease progression and potentially to novel targets for therapeutic intervention.

Simvastatin Induces Death of Multiple Myeloma Cell Lines

Background

Accumulating reports indicate that statins widely prescribed for hypercholesteromia have antineoplastic activity. We hypothesized that because statins inhibit farnesylation of Ras that is often mutated in multiple myeloma (MM), as well as the production of interleukin (IL)-6, a key cytokine in MM, they may have antiproliferative and/or proapoptotic effects in this malignancy.

Methods

U266, RPMI 8226, and ARH77 were treated with simvastatin (0–30 μM) for 5 days. The following aspects were evaluated: viability (IC50), cell cycle, cell death, cytoplasmic calcium ion levels, supernatant IL-6 levels, and tyrosine kinase activity.

Results

Exposure of all cell lines to simvastatin resulted in reduced viability with IC50s of 4.5 μM for ARH77, 8 μM for RPMI 8226, and 13 μM for U266. The decreased viability is attributed to cell-cycle arrest (U266, G1; RPMI 8226, G2M) and cell death. ARH77 underwent apoptosis, whereas U266 and RPMI 8226 displayed a more necrotic form of death. Cytoplasmic calcium levels decreased significantly in all treated cell lines. IL-6 secretion from U266 cells was abrogated on treatment with simvastatin, whereas total tyrosine phosphorylation was unaffected. Conclusions: Simvastatin displays significant antimyeloma activity in vitro. Further research is warranted for elucidation of the modulated molecular pathways and clinical relevance.

Co-administration of simvastatin and cytotoxic drugs is advantageous in myeloma cell lines

We have evaluated the potential application of simvastatin (Sim) combined with conventional cytotoxic drugs for the treatment of multiple myeloma. RPMI 8226 and U266 myeloma cells seeded in culture plates were treated with Sim (5 and 10 microM, respectively) combined with melphalan (Mel; 25 and 20 microM, respectively) or dexamethasone (Dex; 1 microM). We assessed cell cycle (propidium iodide staining and flow cytometric analysis), cell morphology, viability (WST1), total cell count and cell death (Trypan blue exclusion). Sim significantly enhanced the anti-myeloma activity of cytotoxic agents in vitro (p<0.05). Incubation of U266 and RPMI 8226 with Sim prior to Mel increased the cytotoxicity in an additive manner, whereas the exposure of U266 to combined Sim and Dex resulted in a synergistic amplification of the individual effects. Combined application of Dex and Sim to RPMI 8226 cells resulted in antagonistic activity. The possible roles of Ras and phosphoinositol 3-kinase are discussed.

Effect of simvastatin on the uptake and metabolic conversion of palmitic, dihomo-gamma-linoleic and alpha-linolenic acids in A549 cells

It is well known that simvastatin affects cholesterol synthesis. Furthermore it inhibits growth and proliferation and perturbs fatty acid metabolism in some cell lines. We have studied the effects of simvastatin on the uptake and metabolism of exogenous fatty acid in the human lung adenocarcinoma A549 cells. Simvastatin inhibited the proliferation of A549, and caused an increment in phospholipid/cholesterol ratio due to an increment in phospholipid content without affecting cholesterol content. All the fatty acids were uptaken and metabolized in both control and treated cells. The conversion of palmitic, linoleic and dihomo-gamma-linoleic acids to their metabolites and products/precursor ratios for the desaturation and elongation reactions showed that simvastatin enhanced the Delta5 desaturation step and altered some elongating steps. The machinery for unsaturated fatty acid synthesis in A549 is quite sensitive to simvastatin and its effects could have important implication taking into account that highly unsaturated fatty acids are involved in the regulation of diverse cellular functions by themselves or through their metabolites.

Simvastatin induces apoptosis of B-CLL cells by activation of mitochondrial caspase 9

BACKGROUND AND OBJECTIVES

Chronic lymphocytic leukemia (CLL) is the most common leukemia in the western world. Despite several advances in therapeutic options, the disease remains incurable. Recently, it was repeatedly demonstrated that statins, competitive inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, have antineoplastic effects. Therefore we aimed to study the effects of simvastatin (Sim) on malignant B cells derived from patients with CLL and mechanisms of action of the drug.

METHODS AND RESULTS

Purified B-CLL cells from 15 patients were cultured either alone or with Sim at concentrations of 10, 50, and 100 microM. Viability, measured by the activity of mitochondrial dehydrogenases, was reduced significantly in the cells treated with Sim at 50 and 100 microM for 24 hours (p<0.005). The level of apoptosis, as measured by annexin binding to exposed phosphatidylserine moieties, increased significantly in the treated cells at concentrations higher than 50 microM for 24 hours (p<0.003). The level of necrosis, as measured by propidium iodide internalization, increased significantly after 24 hours exposure to Sim at 50 microM (p<0.01). The apoptotic cascade was studied by immunoblot analysis of caspases following Sim treatment. These showed cleavage of caspases 9, 8, and 3. Addition of the caspase inhibitor Z-VAD.fmk inhibited caspase 8 and 3 significantly but did not affect caspase 9.

CONCLUSION

Exposure of clonal B lymphocytes from patients with CLL to simvastatin decreases viability significantly by the induction of apoptosis. The apoptosis induced by Sim is probably initiated by the mitochondrial caspase 9, which indirectly leads to activation of caspase 3 and 8.

Therapeutic efficacy of prenylation inhibitors in the treatment of myeloid leukemia

Farnesyltransferase inhibitors (FTIs) represent a new class of anticancer agents that specifically target post-translational farnesylation of various proteins that mediate several cellular processes such as signal transduction, growth, differentiation, angiogenesis and apoptosis. These compounds were originally designed to block oncogenic RAS-induced tumor growth by impeding RAS localization to the membrane, but it is now evident that FTIs also affect processing of several other proteins. The need for novel therapies in myeloid leukemia is underscored by the high rate of treatment failure due to high incidences of relapse- and treatment-related toxicities. As RAS deregulation is important in the pathogenesis of myeloid leukemias, targeting of RAS signaling may provide a new therapeutic strategy. Several FTIs (eg BMS-214662, L-778,123, R-115777 and SCH66336) have entered phase I and phase II clinical trials in myeloid leukemias. This review discusses recent clinical results, potential combination therapies, mechanisms of resistance and the clinical challenges of toxicities associated with prenylation inhibitors.

Cholesterol-modulating agents kill acute myeloid leukemia cells and sensitize them to therapeutics by blocking adaptive cholesterol responses

The mevalonate pathway produces many critical substances in cells, including sterols essential for membrane structure and isoprenoids vital to the function of many membrane proteins. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase is a rate-limiting enzyme in the mevalonate pathway. Because cholesterol is a product of this pathway, HMG-CoA reductase inhibitors (statins) are used to treat hypercholesterolemia. Statins are also toxic to several malignancies, including acute myeloid leukemia (AML). Although this toxicity has been attributed to the inhibition of Ras/Rho isoprenylation, we have previously shown that statin toxicity in primary AML cells (AMLs) does not correlate with Ras isoprenylation or with activating Ras mutations. In other studies, we have shown that hypoxic and oxidant injuries induce cholesterol increments in renal tubule cells and that statins sensitize these cells to injury by blocking protective cholesterol responses. We now demonstrate that exposing particular AMLs to radiochemotherapy induces much greater cellular cholesterol increments than those seen in similarly treated normal bone marrow. Treatment of these AMLs with mevastatin or zaragozic acid (which inhibits cholesterol synthesis but not isoprenoid synthesis) attenuates the cholesterol increments and sensitizes cells to radiochemotherapy. The extent of toxicity is affected by the availability of extracellular lipoproteins, further suggesting that cellular cholesterol is critical to cell survival in particular AMLs. Because zaragozic acid does not inhibit isoprenoid synthesis, these data suggest that cholesterol modulation is an important mechanism whereby statins exert toxic effects on some AMLs and that cholesterol modulators may improve therapeutic ratios in AML by impacting cholesterol-dependent cytoresistance.

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.

HMG-CoA reductase inhibitors and the malignant cell: the statin family of drugs as triggers of tumor-specific apoptosis

The statin family of drugs target HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway, and have been used successfully in the treatment of hypercholesterolemia for the past 15 years. Experimental evidence suggests this key biochemical pathway holds an important role in the carcinogenic process. Moreover, statin administration in vivo can provide an oncoprotective effect. Indeed, in vitro studies have shown the statins can trigger cells of certain tumor types, such as acute myelogenous leukemia, to undergo apoptosis in a sensitive and specific manner. Mechanistic studies show bcl-2 expression is down-regulated in transformed cells undergoing apoptosis in response to statin exposure. In addition, the apoptotic response is in part due to the depletion of the downstream product geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate or other products of the mevalonate pathway including cholesterol. Clinically, preliminary phase I clinical trials have shown the achievable plasma concentration corresponds to the dose range that can trigger apoptosis of tumor types in vitro. Moreover, little toxicity was evident in vivo even at high concentrations. Clearly, additional clinical trials are warranted to further assess the safety and efficacy of statins as novel and immediately available anti-cancer agents. In this article, the experimental evidence supporting a role for the statin family of drugs to this new application will be reviewed.