HMG-CoA reductase inhibitors reduce adhesion of human monocytes to endothelial cells.

HMG-CoA reductase inhibitors (statins) are believed to reduce coronary heart disease by mechanisms in addition to their well-known cholesterol-lowering effect. We studied the effect of these drugs on monocyte cell adhesion to endothelium. Pretreatment of monocytic cells (U937, THP-1, human CD14(+) monocytes) with 0.01-10 microM concentrations of atorvastatin, cerivastatin, or simvastatin significantly reduced cell adhesion to endothelium. In contrast, pretreatment of endothelium with statins did not affect adhesion of monocytes. Adhesion of monocytes to vascular cell adhesion molecule-1-coated dishes was reduced by these drugs. Cerivastatin also reduced PMA induction of NF-kappaB. Since monocyte adhesion to endothelium is an early event in atherogenesis, treatment with statins in prevention of coronary heart disease may have additional salutary effects to lowering of plasma LDL cholesterol. Our results indicate that the reduction of monocyte adhesion by HMG-CoA reductase inhibitors may be considered as a class effect.     

Pleiotropic effects of statin therapy: molecular mechanisms and clinical results

Statins inhibit the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which is required for cholesterol biosynthesis, and are beneficial in the primary and secondary prevention of cardiovascular disease. Most of the benefits of statin therapy are owing to the lowering of serum cholesterol levels. However, by inhibiting HMG-CoA reductase, statins can also inhibit the synthesis of isoprenoids, which are important lipid attachments for intracellular signaling molecules, such as Rho, Rac and Cdc42. Therefore, it is possible that statins might exert cholesterol-independent or 'pleiotropic' effects through direct inhibition of these small GTP-binding proteins. Recent studies have shown that statins might have important roles in diseases that are not mediated by cholesterol. Here, we review data from recent clinical trials that support the concept of statin pleiotropy and provide a rationale for their clinical importance.     

Essential fatty acids as possible mediators of the actions of statins

Statins and polyunsaturated fatty acids have similar actions: both enhance endothelial nitric oxide synthesis, inhibit the production of pro-inflammatory cytokines, lower cholesterol levels, prevent atherosclerosis and are of benefit in coronary heart disease, stroke and osteoporosis. Statins enhance the conversion of linoleic acid and eicosapentaenoic acid to their long chain derivatives. Animals with essential fatty acid deficiency show an increase in HMG-CoA reductase activity, which reverts to normalcy following topical application of linoleic acid. Similarly to statins, polyunsaturated fatty acids also inhibit HMG-CoA reductase activity. In view of the similarity in their actions and as statins influence essential fatty acid metabolism, it is suggested that essential fatty acids and their metabolites may serve as second messengers of the actions of statins.     

Clinical pharmacology of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.

In this article, de novo cholesterol synthesis, its inhibition by HMG-CoA reductase inhibitors (statins) and clinical pharmacology aspects of the statins have been reviewed. Statins are available in both active and pro-drug forms. Their affinity to bind and subsequently to inhibit HMG-CoA reductase activity is approximately 3 orders of magnitude higher than that of natural substrate (HMG-CoA). All members of this group of lipid-lowering agents are, to a varying degree, absorbed from the gut. However, their bioavailability depends on their lipophobicity and their concomitant use with meals. The interaction between HMG-CoA reductase inhibitors and other lipid-lowering agents has been reviewed in more detail. One major side-effect of lipid-lowering combination therapy is myopathy with or without rhabdomyolysis. Combination of statins with gemfibrozil seems to increase risk of this adverse event, particularly in patients with renal impairment, more than combination with other lipid-lowering agents. Combination therapy with other agents including anticoagulants, antihypertensive, anti-inflammatory, oral hypoglycemic and antifungal agents as well as beta-blockers, H2 blockers, cyclosporine and digoxin has been also reviewed. The pleiotropic non-lipid lowering properties of statins and their effects on the quality of lipoprotein particles, the activities of cholesteryl ester transfer protein and lecithin:cholesterol acyltransferase as well as their possible synergistic effects with n-3 fatty acids, phytosterols, vitamin E and aspirin in reducing cardiovascular events warrant further investigation.     

Isoprenoid depletion by statins antagonizes cytokine-induced down-regulation of endothelial nitric oxide expression and increases NO synthase activity in human umbilical vein endothelial cells.

Endothelial dysfunction and atherosclerosis are associated with an inflammation-induced decrease in endothelial nitric oxide synthase (eNOS) expression. Based on the differences between hydrophobic and hydrophilic statins in their reduction of cardiac events, we analyzed the effects of rosuvastatin and cerivastatin on eNOS and inducible NO synthase (iNOS) expression and NOS activity in TNF-alpha-stimulated human umbilical vein endothelial cells (HUVEC). Both statins reversed down-regulation of eNOS mRNA and protein expression by inhibiting HMG-CoA reductase and isoprenoid synthesis. Cerivastatin tended to a more pronounced effect on eNOS expression compared to rosuvastatin. NOS activity - measured by conversion of [(3)H]-L-arginine to [(3)H]-L-citrulline - was enhanced under treatment with both drugs due to inhibition of HMG-CoA reductase. Statin-treatment reduced iNOS mRNA expression under normal conditions, but had no relevant effects on iNOS mRNA expression in cytokine-treated cells. Rosuvastatin and cerivastatin reverse the detrimental effects of TNF-alpha-induced down-regulation in eNOS protein expression and increase NO synthase activity by inhibiting HMG-CoA reductase and subsequent blocking of isoprenoid synthesis. These results provide evidence that statins have beneficial effects by increasing eNOS expression and activity during the atherosclerotic process.     

Statin therapy for native and peri-interventional coronary heart disease

Atherosclerosis is a slow, complex process involving many different cell types and their interactions producing excessive oxidant stress, increased inflammation, abnormal endothelium-dependent vasodilation, and localized increases in thrombogenic and decreases in fibrinolytic factors. Numerous factors incite these processes, but oxidized LDL particles seem the most essential component of this pathologic cascade. These oxidized particles set up a chain of biochemical events eventually leading to clinical atherosclerotic events. Statins have been shown to reduce such events by 40 to 50% when LDL cholesterol is lowered to less than 80 mg/dL. But in-vitro studies have shown that the provision of mevalonate, not cholesterol, can result in reversal of some of the beneficial effects of statins, suggesting that other mechanisms such as inhibiting the formation of the isoprenoids, farnesyl pyrophosphate and geranylgeranyl pyrophosphate, and thus prenylation of many cell-signaling proteins may be important in the preventive effects of statins. Clinically, these more rapid, non-lipid-altering effects may be more apparent in acute coronary syndromes. Now that we have more LDL-cholesterol lowering agents which lower LDL-cholesterol without blocking HMG CoA reductase, we may be better able to dissect and understand the importance of these non-lipid-altering effects of statins in human disease.     

Statins downregulate myeloperoxidase gene expression in macrophages

Statins, inhibitors of HMG-CoA reductase, have pleiotropic benefits independent of cholesterol levels, including anti-oxidant and anti-inflammatory effects. Here, we investigate the effect of statins on myeloperoxidase (MPO) expression. MPO, expressed in foam cell macrophages, was recently shown to oxidize the ApoA-1 component of HDL, impairing ABCA-1 mediated cholesterol efflux. High levels of serum MPO correlate with increased risk of CAD events. Findings here show that statins strongly inhibit MPO mRNA expression in human and murine monocyte-macrophages. Suppression was reversed by downstream intermediates of HMG-CoA reductase, mevalonate, and geranylgeranylpyrophosphate, but not farnesylpyrophosphate. An inhibitor of geranylgeranyltransferase, GGTI-286, mimics the effects of statins, indicating geranylgeranylation is key to MPO expression. Reduction of MPO mRNA levels was observed in vivo in leukocytes from statin-fed mice, correlating with reductions in MPO protein and enzyme activity. These findings suggest that the pleiotropic protections afforded by statins may be due in part to suppression of MPO expression.     

Biosynthesis and biotechnological production of statins by filamentous fungi and application of these cholesterol-lowering drugs

Hypercholesterolemia is considered an important risk factor in coronary artery disease. Thus the possibility of controlling de novo synthesis of endogenous cholesterol, which is nearly two-thirds of total body cholesterol, represents an effective way of lowering plasma cholesterol levels. Statins, fungal secondary metabolites, selectively inhibit hydroxymethyl glutaryl-coenzyme A (HMG-CoA) reductase, the first enzyme in cholesterol biosynthesis. The mechanism involved in controlling plasma cholesterol levels is the reversible inhibition of HMG-CoA reductase by statins, related to the structural similarity of the acid form of the statins to HMG-CoA, the natural substrate of the enzymatic reaction. Currently there are five statins in clinical use. Lovastatin and pravastatin (mevastatin derived) are natural statins of fungal origin, while symvastatin is a semi-synthetic lovastatin derivative. Atorvastatin and fluvastatin are fully synthetic statins, derived from mevalonate and pyridine, respectively. In addition to the principal natural statins, several related compounds, monacolins and dihydromonacolins, isolated fungal intermediate metabolites, have also been characterized. All natural statins possess a common polyketide portion, a hydroxy-hexahydro naphthalene ring system, to which different side chains are linked. The biosynthetic pathway involved in statin production, starting from acetate units linked to each other in head-to-tail fashion to form polyketide chains, has been elucidated by both early biogenetic investigations and recent advances in gene studies. Natural statins can be obtained from different genera and species of filamentous fungi. Lovastatin is mainly produced by Aspergillus terreus strains, and mevastatin by Penicillium citrinum. Pravastatin can be obtained by the biotransformation of mevastatin by Streptomyces carbophilus and simvastatin by a semi-synthetic process, involving the chemical modification of the lovastatin side chain. The hypocholesterolemic effect of statins lies in the reduction of the very low-density lipoproteins (VLDL) and LDL involved in the translocation of cholesterol, and in the increase in the high-density lipoproteins (HDL), with a subsequent reduction of the LDL- to HDL-cholesterol ratio, the best predictor of atherogenic risk. The use of statins can lead to a reduction in coronary events related to hypercholesterolemia, but the relationship between benefit and risk, and any possible interaction with other drugs, must be taken into account.     

Simvastatin reduces ergosterol levels, inhibits growth and causes loss of mtDNA in Candida glabrata

Statins are widely used for lowering cholesterol levels through their action on 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase. Yeasts use HMG-CoA reductase for the same enzymatic step as humans, but in yeasts the main end-product of the pathway is ergosterol rather than cholesterol. We considered that insights into the effects of statins in humans could be gained by examination of the effects of simvastatin on the petite-positive yeast Candida glabrata. Simvastatin was found to inhibit growth, and this was associated with lower ergosterol levels. As simvastatin-treated cultures of yeast were passaged, the frequencies of petite cells (respiratory-deficient yeast mutants with deletions in the mitochondrial genome) increased with time and with simvastatin concentration. DNA staining of the petite mutants showed that they were devoid of mtDNA, suggesting a defect in the maintenance of mtDNA. These observations in C. glabrata may provide further insights into the molecular effects of statins in humans undergoing treatment for hypercholesterolemia. In addition, if C. glabrata is a valid model for studying statin treatments, it would be very useful for the preliminary screening of agents to reduce statin side-effects.     

Cyclic nucleotides and mitogen-activated protein kinases: regulation of simvastatin in platelet activation

Background  

3-Hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have been widely used to reduce cardiovascular risk. These statins (i.e., simvastatin) may exert other effects besides from their cholesterol-lowering actions, including inhibition of platelet activation. Platelet activation is relevant to a variety of coronary heart diseases. Although the inhibitory effect of simvastatin in platelet activation has been studied; the detailed signal transductions by which simvastatin inhibit platelet activation has not yet been completely resolved.     

Effect of geraniol on fatty-acid and mevalonate metabolism in the human hepatoma cell line Hep G2.

Monoterpenes have multiple pharmacological effects on the metabolism of mevalonate. Geraniol, a dietary monoterpene, has in vitro and in vivo anti-tumor activity against several cell lines. We have studied the effects of geraniol on growth, fatty-acid metabolism, and mevalonate metabolism in the human hepatocarcinoma cell line Hep G2. Up to 100 micromol geraniol/L inhibited the growth rate and 3-hydroxymethylglutaryl coenzyme A reductase (HMG-CoA) reductase activity of these cells. At the same concentrations, it increased the incorporation of cholesterol from the medium in a dose-dependent manner. Geraniol-treated cells incorporated less 14C-acetate into nonsaponifiable lipids, inhibiting its incorporation into cholesterol but not into squalene and lanosterol. This is indicative of an inhibition in cholesterol synthesis at a step between lanosterol and cholesterol, a fact confirmed when cells were incubated with 3H-mevalonate. The incorporation of 3H-mevalonate into protein was also inhibited, whereas its incorporation into fatty acid increased. An inhibition of delta5 desaturase activity was demonstrated by the inhibition of the conversion of 14C-dihomo-gamma-linolenic acid into arachidonic acid. Geraniol has multiple effects on mevalonate and lipid metabolism in Hep G2 cells, affecting cell proliferation. Although mevalonate depletion is not responsible for cellular growth, it affects cholesterogenesis, protein prenylation, and fatty-acid metabolism.     

Effects of statins on the secretion of human serum albumin in cultured HepG2 cells

Statins reduce cholesterol biosynthesis by inhibiting HMG-CoA reductase and thereby lower total cholesterol and LDL cholesterol levels in serum, which in turn lower the incidence of cardiovascular disease (CVD). Statins are also known to modulate various cellular functions such as gene expression, cell proliferation, and programmed cell death through inhibition of downstream intermediates in cholesterol synthesis. In this study, we have investigated the possible effects of statins on the secretion of serum albumin from cultured HepG2 cells since high levels of serum albumin are associated with reduced risks for CVD and statins are effective in lowering the risk of CVD through other effects in addition to their effects on serum total cholesterol and LDL cholesterol levels, known as pleiotropic effects. Our results showed that simvastatin increased HSA secretion up to 32.3% compared to the control group. Among 3 statin analogs we tested, simvastatin exhibited the highest stimulatory effects on HSA secretion compared to the control group. Our study also showed that the increased HSA secretions from HepG2 cells by simvastatin treatments were due to the increased rate of HSA synthesis, not due to the reduced posttranslational degradation rate of HSA. Our finding suggests another added benefit of statins'' treatments in preventing CVD through stimulation of HSA biosynthesis.     

LDL-induced impairment of human vascular smooth muscle cells repair function is reversed by HMG-CoA reductase inhibition

Growing human atherosclerotic plaques show a progressive loss of vascular smooth muscle cells (VSMC) becoming soft and vulnerable. Lipid loaded-VSMC show impaired vascular repair function and motility due to changes in cytoskeleton proteins involved in cell-migration. Clinical benefits of statins reducing coronary events have been related to repopulation of vulnerable plaques with VSMC. Here, we investigated whether HMG-CoA reductase inhibition with rosuvastatin can reverse the effects induced by atherogenic concentrations of LDL either in the native (nLDL) form or modified by aggregation (agLDL) on human VSMC motility. Using a model of wound repair, we showed that treatment of human coronary VSMC with rosuvastatin significantly prevented (and reversed) the inhibitory effect of nLDL and agLDL in the repair of the cell depleted areas. In addition, rosuvastatin significantly abolished the agLDL-induced dephosphorylation of myosin regulatory light chain as demonstrated by 2DE-electrophoresis and mass spectrometry. Besides, confocal microscopy showed that rosuvastatin enhances actin-cytoskeleton reorganization during lipid-loaded-VSMC attachment and spreading. The effects of rosuvastatin on actin-cytoskeleton dynamics and cell migration were dependent on ROCK-signalling. Furthermore, rosuvastatin caused a significant increase in RhoA-GTP in the cytosol of VSMC. Taken together, our study demonstrated that inhibition of HMG-CoA reductase restores the migratory capacity and repair function of VSMC that is impaired by native and aggregated LDL. This mechanism may contribute to the stabilization of lipid-rich atherosclerotic plaques afforded by statins.     

Interaction of statins with phospholipid bilayers studied by solid-state NMR spectroscopy

Statins are drugs that specifically inhibit the enzyme HMG-CoA reductase and thereby reduce the concentration of low-density lipoprotein cholesterol, which represents a well-established risk factor for the development of atherosclerosis. The results of several clinical trials have shown that there are important intermolecular differences responsible for the broader pharmacologic actions of statins, even beyond HMG-CoA reductase inhibition. According to one hypothesis, the biological effects exerted by these compounds depend on their localization in the cellular membrane. The aim of the current work was to study the interactions of different statins with phospholipid membranes and to investigate their influence on the membrane structure and dynamics using various solid-state NMR techniques. Using ¹H NOESY MAS NMR, it was shown that atorvastatin, cerivastatin, fluvastatin, rosuvastatin, and some percentage of pravastatin intercalate the lipid-water interface of POPC membranes to different degrees. Based on cross-relaxation rates, the different average distribution of the individual statins in the bilayer was determined quantitatively. Investigation of the influence of the investigated statins on membrane structure revealed that lovastatin had the least effect on lipid packing and chain order, pravastatin significantly lowered lipid chain order, while the other statins slightly decreased lipid chain order parameters mostly in the middle segments of the phospholipid chains.     

Cholesterol and Alzheimer's disease

Accumulation of a 40-42-amino acid peptide, termed amyloid-beta peptide (A beta), is associated with Alzheimer's disease (AD), and identifying medicines that inhibit A beta could help patients with AD. Recent evidence suggests that a class of medicines that lower cholesterol by blocking the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase), termed statins, can inhibit A beta production. Increasing evidence suggests that the enzymes that generate A beta function best in a high-cholesterol environment, which might explain why reducing cholesterol would inhibit A beta production. Studies using both neurons and peripheral cells show that reducing cellular cholesterol levels, by stripping off the cholesterol with methyl-beta-cyclodextrin or by treating the cells with HMG-CoA reductase inhibitors, decreases A beta production. Studies performed on animal models and on humans concur with these results. In humans, lovastatin, an HMG-CoA reductase inhibitor, has been shown to reduce A beta levels in blood of patients by up to 40%. The putative role of A beta in AD raises the possibility that treating patients with statins might lower A beta, and thereby either delay the occurrence of AD or retard the progression of AD. Two large retrospective studies support this hypothesis. Both studies suggest that patients taking statins had an approx. 70% lower risk of developing AD. Since statins are widely used by doctors, their ability to reduce A beta offers a putative therapeutic strategy for treating AD by using medicines that have already been proved safe to use in humans.     

Effect of ethanol on cell growth and cholesterol metabolism in cultured Hep G2 cells.

The Hep G2 human hepatoma cell line has been recognized as an excellent in vitro human model system. For this reason, this line was used to study the effect of ethanol on HMG-CoA reductase activity concerning cell growth and cholesterol metabolism. Cells were incubated in ethanol-containing medium (0-400 mmol/L) for up to 102 h. Ethanol caused an inhibition in the growth rate and in HMG-CoA reductase activity that could be reverted by the removal of ethanol from the culture medium, indicating no cellular damage. These changes cannot be ascribed to the regulatory effect of cholesterol levels, since its content was not modified either in the cells or in the medium. The addition of mevalonate to the culture medium could not revert the growth rate inhibition evoked by ethanol. Moreover, ethanol produced an increment in the cholesterol efflux in [3H]cholesterol-prelabeled cells. We conclude that the decrease in HMG-CoA reductase activity evoked by ethanol treatment on Hep G2 cells would not be the cause but the consequence of the impairment in cellular growth, since this impairment could not be reverted by the addition of mevalonate to the culture medium.     

Atorvastatin stimulates the production of osteoprotegerin by human osteoblasts

Recently, HMG-CoA reductase inhibitors (statins), potent inhibitors of cholesterol biosynthesis, have been linked to protective effects on bone metabolism. Because of their widespread use, prevention of bone loss and fractures would be a desirable side effect. However, the mechanisms how statins may affect bone metabolism are poorly defined. Here, we evaluated the effect of atorvastatin on osteoblastic production of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG), cytokines that are essential for osteoclast cell biology. While RANKL enhances osteoclast formation and activation, thereby, promoting bone loss, OPG acts as a soluble decoy receptor and antagonizes the effects of RANKL. In primary human osteoblasts (hOB), atorvastatin increased OPG mRNA levels and protein secretion by hOB by up to three fold in a dose-dependent manner with a maximum effect at 10(-6) M (P < 0.001). Time course experiments indicated a time-dependent stimulatory effect of atorvastatin on OPG mRNA levels after 24 h and on OPG protein secretion after 48-72 h (P < 0.001). Treatment of hOB with substrates of cholesterol biosynthesis that are downstream of the HMG-CoA reductase reaction (mevalonate, geranylgeranyl pyrophosphate) reversed atorvastatin-induced enhancement of OPG production. Of note, atorvastatin abrogated the inhibitory effect of glucocorticoids on OPG production. Treatment of hOB with atorvastatin enhanced the expression of osteoblastic differentiation markers, alkaline phosphatase and osteocalcin. In summary, our data suggest that atorvastatin enhances osteoblastic differentiation and production of OPG. This may contribute to the bone-sparing effects of statins.     

Toward a role for statins in immunomodulation

The family of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) inhibitors, collectively known as statins, is used clinically to reduce cholesterol levels in patients. Recent reports suggest that not only would statin therapy be beneficial for at-risk (genetically predisposed) people without symptoms of hypercholesterolemia, but that statins may have beneficial, pleiotropic effects in the treatment of autoimmune diseases. Youssef et al. have described how an HMG-CoA inhibitor, atorvastatin, might ameliorate experimental autoimmune encephalomyelitis (EAE), the mouse model for human multiple sclerosis. The possible clinical use of statins as anti-inflammatory drugs has also been demonstrated in other published reports. These provocative results suggest a role for statins in relieving autoimmune diseases such as multiple sclerosis.     

Abrogation of insulin-like growth factor-I (IGF-I) and insulin action by mevalonic acid depletion: synergy between protein prenylation and receptor glycosylation pathways

The vasculoprotective effects of hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors (statins) correlate with cholesterol lowering. HMG-CoA reductase inhibitors also disrupt cellular processes by the depletion of isoprenoids and dolichol. Insulin and insulin-like growth factor (IGF) signaling appear particularly prone to such disruption as intracellular receptor processing requires dolichol for correct N-glycosylation, whereas downstream signaling through Ras requires the appropriate prenylation (farnesol). We determined how HMG-CoA reductase inhibition affected the mitogenic effects of IGF-I and metabolic actions of insulin in 3T3-L1 cells and examined the respective roles of receptor glycosylation and Ras prenylation. IGF-I- and insulin-induced proliferation was significantly reduced by all statins tested, although cerivastatin (10 nm) had the greatest effect (p < 0.005). Although inhibitors of Ras prenylation induced similar results (10 microm FTI-277 89% +/- 7.4%, p < 0.01), the effect of HMG-CoA reductase inhibition could only be partially reversed by farnesyl pyrophosphate refeeding. Treatment with statins resulted in decreased membrane expression of receptors and accumulation of proreceptors, suggesting disruption of glycosylation-dependent cleavage. Glycosylation inhibitors inhibited IGF-I-induced proliferation (tunicamycin p < 0.005, castanospermine p < 0.01, deoxymannojirimycin p < 0.01). High concentrations of statin were necessary to impair insulin-mediated glucose uptake (300 nm = 33% +/- 12% p < 0.05), and this process was not effected by farnesyl transferase inhibition. Gycosylation inhibitors mimicked the effect of statin treatment (tunicamycin p < 0.001, castanospermine p < 0.05, deoxymannojirimycin p < 0.05), and there was insulin proreceptor accumulation. These data imply that HMG-CoA reductase inhibitors disrupt IGF-I signaling by combined effects on Ras prenylation and IGF receptor glycosylation, whereas insulin signaling is only affected by disrupted receptor glycosylation.     

Inhibition of lung cancer growth: ATP citrate lyase knockdown and statin treatment leads to dual blockade of mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-kinase (PI3K)/AKT pathways

ATP citrate lyase (ACL) catalyzes the conversion of cytosolic citrate to acetyl-CoA and oxaloacetate. A definitive role for ACL in tumorigenesis has emerged from ACL RNAi and chemical inhibitor studies, showing that ACL inhibition limits tumor cell proliferation and survival and induces differentiation in vitro. In vivo, it reduces tumor growth leading to a cytostatic effect and induces differentiation. However, the underlying molecular mechanisms are poorly understood and agents that could enhance the efficacy of ACL inhibition have not been identified. Our studies focus on non-small cell lung cancer (NSCLC) lines, which show phosphatidylinositol 3-kinase (PI3K)/AKT activation secondary to a mutation in the K-Ras gene or the EGFR gene. Here we show that ACL knockdown promotes apoptosis and differentiation, leading to the inhibition of tumor growth in vivo. Moreover, in contrast to most studies, which elucidate how activation/suppression of signaling pathways can modify metabolism, we show that inhibition of a metabolic pathway "reverse signals" and attenuates PI3K/AKT signaling. Additionally, we find that statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, which act downstream of ACL in the cholesterol synthesis pathway, dramatically enhance the anti-tumor effects of ACL inhibition, even regressing established tumors. With statin treatment, both PI3K/AKT and the MAPK pathways are affected. Moreover, this combined treatment is able to reduce the growth of EGF receptor resistant tumor cell types. Given the essential role of lipid synthesis in numerous cancers, this work may impact therapy in a broad range of tumors.