Mevalonate promotes the growth of tumors derived from human cancer cells in vivo and stimulates proliferation in vitro with enhanced cyclin-dependent kinase-2 activity

The role of cholesterol metabolism and cholesterol transport in carcinogenesis: a review of scientific findings, relevant to future cancer therapeutics

While the unique metabolic activities of malignant tissues as potential targets for cancer therapeutics has been the subject of several recent reviews, the role of cholesterol metabolism in this context is yet to be fully explored. Cholesterol is an essential component of mammalian cell membranes as well as a precursor of bile acids and steroid hormones. The hypothesis that cancer cells need excess cholesterol and intermediates of the cholesterol biosynthesis pathway to maintain a high level of proliferation is well accepted, however the mechanisms by which malignant cells and tissues reprogram cholesterol synthesis, uptake and efflux are yet to be fully elucidated as potential therapeutic targets. High and low density plasma lipoproteins are the likely major suppliers of cholesterol to cancer cells and tumors, potentially via receptor mediated mechanisms. This review is primarily focused on the role(s) of lipoproteins in carcinogenesis, and their future roles as drug delivery vehicles for targeted cancer chemotherapy.

Statin use in primary inflammatory breast cancer: a cohort study

Background:

Some studies have suggested that statins, which have cholesterol-lowering and anti-inflammatory properties, may have antitumor effects. Effects of statins on inflammatory breast cancer (IBC) have never been studied.

Methods:

We reviewed 723 patients diagnosed with primary IBC in 1995–2011 and treated at The University of Texas MD Anderson Cancer Center. Statin users were defined as being on statins at the initial evaluation. Based on Ahern et al's statin classification (JNCI, 2011), clinical outcomes were compared by statin use and type (weakly lipophilic to hydrophilic (H-statin) vs lipophilic statins (L-statin)). We used the Kaplan–Meier method to estimate the median progression-free survival (PFS), overall survival (OS) and disease-specific survival (DSS), and a Cox proportional hazards regression model to test the statistical significance of potential prognostic factors.

Results:

In the multivariable Cox model, H-statins were associated with significantly improved PFS compared with no statin (hazard ratio=0.49; 95% confidence interval=0.28–0.84; P<0.01); OS and DSS P-values were 0.80 and 0.85, respectively. For L-statins vs no statin, P-values for PFS, DSS, and OS were 0.81, 0.4, and 0.74, respectively.

Conclusion:

H-statins were associated with significantly improved PFS. A prospective randomised study evaluating the survival benefits of statins in primary IBC is warranted.

Statins and colorectal cancer

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, more commonly referred to as statins, comprise a family of lipid-lowering drugs that are prescribed on a global scale on account of their proven safety and efficacy in reducing mortality from cardiovascular disease. Beyond their potent pharmacologic inhibition of cholesterol biosynthesis, statins appear to have pleiotropic effects, including modulation of cell growth, apoptosis, and inflammation. Through modulation of these pathways, statins have the potential to influence a wide range of disease processes, including cancer. Much attention has focused on the association between statins and colorectal cancer, raising the prospect that these well-tolerated compounds could form the basis of future chemopreventive strategies. Herein, we review the epidemiologic, clinical, and preclinical data relevant to statins and colorectal neoplasia, and discuss the current status and future potential of statins as chemopreventive agents.

A comparison of cholesterol uptake and storage in inflammatory and noninflammatory breast cancer cells

Although there are many subtypes of breast cancer, inflammatory breast cancer (IBC) is arguably the deadliest. Research over the past decade has demonstrated that IBC is a distinct entity from other forms of breast cancer. Important risk factors that have been associated with the development of aggressive breast cancers, such as IBC, include obesity and diet, which are evident in the United States, where the overconsumption of high-fat foods continues to contribute to obesity in the nation. Here we investigate differences in cholesterol uptake and storage between IBC, non-IBC, and mammary epithelial cell lines. Our results demonstrate that compared with human mammary epithelial cells (HMECs), both IBC and non-IBC cells have increased cholesterol content. IBC cells retain intracellular cholesterol esters, free cholesterol, and triglycerides in lipid-deficient environments. In contrast, we observe in cell-type-of-origin-matched non-IBC a significant decrease in lipid content under the same lipid-deficient conditions. These data suggest that cholesterol storage may be affected by the cholesterol content of the environment where the tumor cell was isolated. Here, we suggest that breast cancer cells may migrate when they are unable to obtain cholesterol from their extracellular environments.

Mevalonate pathway is a therapeutic target in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common lethal tumors in the world. Thus, it is very urgent to develop new therapeutic targets against this disease. The mevalonate (MVA) pathway, paced by its rate-limiting enzyme, hydroxymethylglutaryl coenzyme A reductase, is required for the generation of several fundamental end products including cholesterol and isoprenoids. The function of the MVA pathway in ESCC has not been investigated. In this study, it was found that the MVA pathway was upregulated in ESCC clinical samples. Statin, the inhibitor of the MVA pathway, exerted potent cytotoxicity against human ESCC cells by inhibiting cell growth and proliferation, while it exerted lesser effects on non-tumorigenic SHEE cells. Further study revealed that statin could potently induce cell apoptosis and cell cycle arrest and also dose-dependently inhibit the growth of xenograft tumors in nude mice. With regard to the molecular mechanism, statin treatment was related to decreased extracellular signal-regulated kinase activation and proliferating cell nuclear antigen, cyclin D1 expression, and increased cleavage of poly(ADP-ribose) polymerase. Taken together, our findings suggest that the MVA pathway plays an important role in the progression of ESCC by modulating cell growth and statin might be a potential therapeutic agent in ESCC.

Monascus-fermented red mold rice exhibits cytotoxic effect and induces apoptosis on human breast cancer cells

Red mold rice (RMR) is a traditional food and folk medicine to Asian people and has recently become a popular health supplement. RMR has been shown to have some anticancer activities, although the mechanism for inducing cell death of human breast cancer cells is still not fully understood. In this study, bioactive extracts of RMR fermented by Monascus purpureus NTU 803 were analyzed for effects on apoptosis induction in human breast cancer cells. The RMR ethanol extract and ethyl acetate extract contain monacolin K, total phenols, and flavonoids, the three components that have been reported to have anticancer activity. Red mold rice extracts (RMRE) exhibited selective cytotoxic effect on MCF-7 cells. RMRE treatment induced apoptosis and cell cycle arrest at G2/M phase. Apoptosis was confirmed by annexin V-fluorescein isothiocyanate (FITC)/propidium iodide staining, the observation of characteristic chromatin condensation, nuclear DNA fragmentation, and poly(ADP-ribose) polymerase cleavage. Furthermore, the RMRE-induced apoptosis in MCF-7 cells may occur through a mitochondria-dependent pathway while triggering an appropriate balance of bax/bcl-2 and activation of caspase-9 and caspase-3 in a time-dependent manner. To conclude, RMRE exhibits direct cytotoxic and proapoptotic effects on MCF-7 cells and could be considered as a potential functional food for breast cancer prevention.

Propiconazole-enhanced hepatic cell proliferation is associated with dysregulation of the cholesterol biosynthesis pathway leading to activation of Erk1/2 through Ras farnesylation

Propiconazole is a mouse hepatotumorigenic fungicide designed to inhibit CYP51, a key enzyme in the biosynthesis of ergosterol in fungi and is widely used in agriculture to prevent fungal growth. Metabolomic studies in mice revealed that propiconazole increased levels of hepatic cholesterol metabolites and bile acids, and transcriptomic studies revealed that genes within the cholesterol biosynthesis, cholesterol metabolism and bile acid biosyntheses pathways were up-regulated. Hepatic cell proliferation was also increased by propiconazole. AML12 immortalized hepatocytes were used to study propiconazole's effects on cell proliferation focusing on the dysregulation of cholesterol biosynthesis and resulting effects on Ras farnesylation and Erk1/2 activation as a primary pathway. Mevalonate, a key intermediate in the cholesterol biosynthesis pathway, increases cell proliferation in several cancer cell lines and tumors in vivo and serves as the precursor for isoprenoids (e.g. farnesyl pyrophosphate) which are crucial in the farnesylation of the Ras protein by farnesyl transferase. Farnesylation targets Ras to the cell membrane where it is involved in signal transduction, including the mitogen-activated protein kinase (MAPK) pathway. In our studies, mevalonic acid lactone (MVAL), a source of mevalonic acid, increased cell proliferation in AML12 cells which was reduced by farnesyl transferase inhibitors (L-744,832 or manumycin) or simvastatin, an HMG-CoA reductase inhibitor, indicating that this cell system responded to alterations in the cholesterol biosynthesis pathway. Cell proliferation in AML12 cells was increased by propiconazole which was reversed by co-incubation with L-744,832 or simvastatin. Increasing concentrations of exogenous cholesterol muted the proliferative effects of propiconazole and the inhibitory effects of L-733,832, results ascribed to reduced stimulation of the endogenous cholesterol biosynthesis pathway. Western blot analysis of subcellular fractions from control, MVAL or propiconazole-treated cells revealed increased Ras protein in the cytoplasmic fraction of L-744,832-treated cells, while propiconazole or MVAL reversed these effects. Western blot analysis indicated that phosphorylation of Erk1/2, a protein downstream of Ras, was increased by propiconazole. These data indicate that propiconazole increases cell proliferation by increasing the levels of cholesterol biosynthesis intermediates presumably through a negative feedback mechanism within the pathway, a result of CYP51 inhibition. This feedback mechanism increases Erk1/2 signaling through mevalonate-mediated Ras activation. These results provide an explanation for the observed effects of propiconazole on hepatic cholesterol pathways and on the increased hepatic cell proliferation induced by propiconazole in mice.

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

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

Novel effects of statins in enhancing efficacy of chemotherapy in vitro in nasopharyngeal carcinoma

BACKGROUND

Nasopharyngeal cancer (NPC) is a relatively uncommon malignant epithelial cancer seen worldwide. The treatment of NPC has evolved toward combined modality treatment with radiation therapy and chemotherapy. However, chemotherapeutic agents currently have a secondary role, due to their lack of efficacy as curative agents. Recent identification of a novel property of statin drugs raises a promising hope that concurrent use of statins may enhance the efficacy of single-drug chemotherapy in NPC. However, the effects of statins have not been studied before in NPC. In this in vitro study, we demonstrate a unique property of statins that can enhance the efficacy of cisplatin in NPC.

METHODS

Primary human NPC cells (CCL-30) were treated with statins and cisplatin concurrently, and the effects on cell proliferation, apoptosis, and cell colony formation were examined.

RESULTS

Statins caused significant decrease in cell proliferation and viability in NPC. Statins also induced loss of cell attachment, change in cellular morphology, decrease in colony forming units, and loss of sphere formation in soft gel agar, which are the important properties of tumorigenicity in NPC. Furthermore, we found that the effects of statins occur by a mevalonate (MA)-mediated pathway in these cells.

CONCLUSIONS

We demonstrate a unique property of statins that can enhance the antitumor effects of cisplatin in NPC. Statins may act as a relatively safe and cost effective chemoadjuvant agent in the treatment of NPC.

Propiconazole induces alterations in the hepatic metabolome of mice: relevance to propiconazole-induced hepatocarcinogenesis

Propiconazole is a mouse hepatotumorigenic fungicide and has been the subject of recent investigations into its carcinogenic mechanism of action. The goals of this study were (1) to identify metabolomic changes induced in the liver by increasing doses of propiconazole in mice, (2) to interpret these results with key previously reported biochemical, transcriptomic, and proteomic findings obtained from mouse liver under the same treatment conditions, and (3) to relate these alterations to those associated with the carcinogenesis process. Propiconazole was administered to male CD-1 mice in the feed for 4 days with six mice per feed level (500, 1250, and 2500 ppm). The 2500 ppm dose level had previously been shown to induce both adenocarcinomas and adenomas in mouse liver after a 2-year continuous feed regimen. Endogenous biochemicals were profiled using liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry methods and 261 were detected. The most populous biochemical class detected was lipids, followed by amino acids and then carbohydrates. Nucleotides, cofactors and vitamins, energy, peptides, and xenobiotics were also represented. Of the biochemicals detected, 159 were significantly altered by at least one dose of propiconazole and many showed strong dose responses. Many alterations in the levels of biochemicals were found in the glycogen metabolism, glycolysis, lipolysis, carnitine, and the tricarboxylic acid cycle pathways Several groups of metabolomic responses were ascribed to the metabolism and clearance of propiconazole: glucuronate, glutathione, and cysteine pathways. Groups of metabolic responses supported previous hypotheses on key events that can lead to propiconazole-induced tumorigenesis: oxidative stress and increases in the cholesterol biosynthesis pathway. Groups of metabolomic responses identified biomarkers associated with neoplasia: increases in glycolysis and increases in the levels of spermidine, sarcosine, and pseudouridine. These results extended the companion transcriptomic and proteomic studies and provided a more complete understanding of propiconazole's effects in mouse liver.

Simvastatin impairs murine melanoma growth

Background

Statins induces cell cycle arrest, apoptosis, reduction of angiogenic factors, inhibition of the endothelial growth factor, impairing tissue adhesion and attenuation of the resistance mechanisms. The aim of this study was evaluate the anti-tumoral activity of simvastatin in a B16F10 melanoma-mouse model.

Methods

Melanoma cells were treated with different concentrations of simvastatin and assessed by viability methods. Melanoma cells (5 × 10⁴) were implanted in two month old C57Bl6/J mice. Around 7 days after cells injection, the oral treatments were started with simvastatin (5 mg/kg/day, p.o.). Tumor size, hematological and biochemical analyses were evaluated.

Results

Simvastatin at a concentration of 0.8 μM, 1.2 μM and 1.6 μM had toxic effect. Concentration of 1.6 μM induced a massive death in the first 24 h of incubation. Simvastatin at 0.8 μM induces early cell cycle arrest in G0/G1, followed by increase of hypodiploidy. Tumor size were evaluated and the difference of treated group and control, after ten days, demonstrates that simvastatin inhibited the tumor expansion in 68%.

Conclusion

Simvastatin at 1.6 μM, presented cytototoxicity after 72 h of treatment, with an intense death. In vivo, simvastatin being potentially useful as an antiproliferative drug, with an impairment of growth after ten days.

Association of lipid metabolism with ovarian cancer

Defects in lipid metabolism have been found to be linked to several diseases, among which atherosclerosis, hypertension, obesity, and diabetes are the most important. Although cancer is chiefly a genetic disease, dietary lipid intake and metabolism are related to some cancer risks, including the risk for ovarian cancer. Higher intake of dietary lipids, systemic lipid metabolism malfunction, and abnormal serum lipid levels are somehow related to ovarian cancer. Overexpression of some lipid metabolic enzymes are also found in ovarian cancer. In this review article, we summarize the relationships between lipid intake, lipid metabolism, and ovarian cancer.

Dysregulation of the mevalonate pathway promotes transformation

The importance of cancer metabolism has been appreciated for many years, but the intricacies of how metabolic pathways interconnect with oncogenic signaling are not fully understood. With a clear understanding of how metabolism contributes to tumorigenesis, we will be better able to integrate the targeting of these fundamental biochemical pathways into patient care. The mevalonate (MVA) pathway, paced by its rate-limiting enzyme, hydroxymethylglutaryl coenzyme A reductase (HMGCR), is required for the generation of several fundamental end-products including cholesterol and isoprenoids. Despite years of extensive research from the perspective of cardiovascular disease, the contribution of a dysregulated MVA pathway to human cancer remains largely unexplored. We address this issue directly by showing that dysregulation of the MVA pathway, achieved by ectopic expression of either full-length HMGCR or its novel splice variant, promotes transformation. Ectopic HMGCR accentuates growth of transformed and nontransformed cells under anchorage-independent conditions or as xenografts in immunocompromised mice and, importantly, cooperates with RAS to drive the transformation of primary mouse embryonic fibroblasts cells. We further explore whether the MVA pathway may play a role in the etiology of human cancers and show that high mRNA levels of HMGCR and additional MVA pathway genes correlate with poor prognosis in a meta-analysis of six microarray datasets of primary breast cancer. Taken together, our results suggest that HMGCR is a candidate metabolic oncogene and provide a molecular rationale for further exploring the statin family of HMGCR inhibitors as anticancer agents.

Ezetimibe reverses the inhibitory effects of dietary cholesterol on mammary tumorigenesis in rats

There are concerns regarding increased cancer incidence in patients treated with ezetimibe, an inhibitor of the absorption of dietary cholesterol. Here we tested the hypothesis that ezetimibe will accelerate mammary tumorigenesis in rats. The drug was administered at a dose of 1 ppm in an AIN-93G diet that contained 0.3% cholesterol. This experimental diet and control diets that contained either no additions or cholesterol or ezetimibe only, were fed to groups of 30 Sprague-Dawley rats 3 days after they were treated with 50 mg/kg methylnitrosourea (MNU). All rats were euthanized 22 weeks after MNU administration. Tumor multiplicity was significantly smaller in rats fed cholesterol than those fed no cholesterol (1.84 +/- 0.42 vs. 3.86 +/- 0.86 respectively, P < 0.05), but was significantly greater in the cholesterol/ezetimibe group than the group fed only cholesterol (3.48 +/- 0.59 vs. 1.84 +/- 0.42 respectively, P < 0.04). The average weight of tumors/rat was also significantly larger in the cholesterol/ezetimibe group than those fed cholesterol alone (5.67 +/- 1.15 vs. 2.56 +/- 0.71 respectively, P < 0.04). As expected, ezetimibe prevented the cholesterol raising effect of the dietary cholesterol. These results show that ezetimibe reverses the inhibitory effect of dietary cholesterol on the development of rat mammary tumors.

Blockade of the RhoA-JNK-c-Jun-MMP2 cascade by atorvastatin reduces osteosarcoma cell invasion

Osteosarcoma is characterized by a high malignant and metastatic potential, which points to the need for new therapeutic strategies to prevent cell metastasis. In this study, we show that statin-induced HMG-CoA reductase inhibition reduces cell migration and invasion in human and murine osteosarcoma cells, independently of the genotype. The statin-induced reduction of cell migration and invasion was independent of induction of apoptosis and was geranylgeranylpyrophosphate-dependent. The statin reduced matrix metalloproteinase (MMP) 2, 9, and 14 and TIMP2 expression or activity in invading cells. Forced expression of MMP2 and MMP14 overcame the inhibitory effect of the statin on cell invasion, suggesting a role for these MMPs in invasive potential. We also investigated the mechanisms involved in the reduced MMP2 activity and cell invasion. Inhibition of JNK, but not ERK1/2 signaling, reduced MMP2 activity. Pharmacological or constitutive activation of JNK overcame the reduced MMP2 activity and cell invasion induced by the statin. The statin decreased JNK phosphorylation and c-Jun nuclear translocation, suggesting that HMG-CoA reductase inhibition targets the JNK-c-Jun signaling pathway. We showed that mevalonate or geranylgeranylpyrophosphate treatment prevented the statin-induced reduction in JNK phosphorylation, MMP2 activity, and cell invasion. Forced expression of a constitutively active form of RhoA increased JNK phosphorylation and overcame the inhibitory effect of atorvastatin on MMP2 activity and cell invasion. The data establish a link between RhoA, JNK, c-Jun, and MMP2 activity that is functionally involved in the reduction in osteosarcoma cell invasion by the statin. This suggests a novel strategy targeting RhoA-JNK-c-Jun signaling to reduce osteosarcoma cell tumorigenesis.

Statins and cancer risk

OBJECTIVE

Despite numerous randomized clinical trials and observational epidemiologic studies, evidence on the potential effectiveness of statins for prevention of cancer remains controversial. The objective of this study was to investigate the relation between lipophilic statin use and cancer occurrence.

METHODS

We conducted a retrospective observational study based on a medical administrative database in the province of Quebec, Canada (1998-2004). Patients aged 45 years or more and discharged from the hospital alive after admission for acute myocardial infarction were included. High- and low-dose statin use were defined as a filled prescription, within 3 days after index discharge, at or above (below) the statin-specific target dose, for any of the 4 lipophilic statin medications: atorvastatin, simvastatin, lovastatin, or fluvastatin. Statin non-use was defined as non-use of any statins while simultaneously using major non-statin cardiac medications. A total of 30,076 patients, including high-dose statin users (n=6015), low-dose statin users (n=5323), and non-users (n=18,738), were followed for up to 7 years. Multivariable Cox regression analyses were performed to estimate associations between statin dose category and the incidence of admission to hospital with a diagnosis of any type of cancer.

RESULTS

The crude incidence rates of hospital admission with the diagnosis of any type of cancer were 13.9, 17.2, and 26.0 per 1000 person-years in statin high-dose users, low-dose users, and non-users, respectively. The estimated adjusted hazard ratios were 0.75 (95% confidence interval [CI], 0.60-0.95) for statin use at high dose and 0.89 (95% CI, 0.75-1.07) for statin use at low dose. No significant time-dependence of the effect of statins at either dose was detected.

CONCLUSION

The use of lipophilic statins at sufficiently high dose might be associated with a clinically important reduction in the incidence of cancer.

Postmenopausal hormone therapy in clinical perspective

Although many of the risks and benefits of postmenopausal hormone therapy are known, only recently has the magnitude of these effects and their perspective to other therapies become more fully understood. Careful review of randomized controlled trials indicates that the risks of postmenopausal hormone therapy including breast cancer, stroke and venous thromboembolism are similar to other commonly used agents. Overall, these risks are rare (less than 1 event per 1,000 women) and even rarer when initiated in women less than 60 years of age or within 10 years of menopause. In addition, the literature indicates similar benefit of postmenopausal hormone therapy, in women who initiate hormone therapy in close proximity to menopause, to other medications used for the primary prevention of coronory heart disease in women.

Lipid mediators in membrane rafts are important determinants of human health and disease

The new field of membrane rafts has provided fresh insight and a novel framework in which to understand the interaction, relation, and organization of lipids and proteins within cell membranes. This review will examine our current understanding of membrane rafts and their role in human health. In addition, the effect of various lipids, including dietary lipids, on membrane raft structure and function will be discussed. Membrane rafts are found in all cells and are characterized by their high concentration of cholesterol, sphingolipids, and saturated fatty acids. These lipids impart lateral segregation of membrane proteins, thus facilitating the spatial organization and regulation of membrane proteins involved in many cellular processes, such as cell proliferation, apoptosis, and cell signaling. Therefore, membrane rafts are shedding new light on the origins of metabolic disturbances and diseases such as cancer, insulin resistance, inflammation, cardiovascular disease, and Alzheimer's disease, which will be further discussed in this review.

Cholesterol sensitivity of endogenous and myristoylated Akt

The serine-threonine kinase, Akt, has been linked to cholesterol-sensitive signaling mechanisms, suggesting a possible means whereby cholesterol might affect tumor cell growth and survival. However, it has not been shown whether Akt itself, as distinct from upstream components of the pathway (e.g., membrane phosphoinositides), can be directly responsible for cholesterol-mediated effects. Consistent with this possibility, we identified an Akt1 subpopulation in cholesterol-rich lipid raft fractions prepared from LNCaP human prostate cancer cells. Phosphorylation of this Akt subspecies was ablated with methyl-beta-cyclodextrin, a cholesterol-binding compound, under conditions where nonlipid raft-resident Akt was unaffected. A myristoylated Akt1 (MyrAkt1) fusion protein expressed in LNCaP cells was found to be highly enriched in lipid rafts, indicating that oncogenic Akt is overrepresented in cholesterol-rich membranes compared with wild-type Akt. Notably, lipid raft-resident MyrAkt1 exhibited a markedly distinct substrate preference compared with MyrAkt1 immunoprecipitated from cytosol and nonraft membrane fractions, suggesting a redirection of signal transduction when the protein is present in cholesterol-rich membranes. Expression of MyrAkt1 in LNCaP cells overcame their characteristic dependence on constitutive signaling through the phosphoinositide 3'-kinase pathway. This protective effect was substantially diminished with cyclodextrin treatment. Phosphorylation of Akt substrates in lipid raft fractions, but not in cytosol/nonraft membrane fractions, was ablated with cyclodextrin. In addition, in control (LacZ transfected) cells, lipid raft fractions were relatively enriched in phosphorylated Akt substrates. Collectively, these data show that a subpopulation of Akt is cholesterol sensitive and that the oncogenic effects conferred by myristoylation arise, in part, from the tendency of the membrane-targeted form of the protein to reside in cholesterol-rich membrane microdomains.

Simvastatin inactivates beta1-integrin and extracellular signal-related kinase signaling and inhibits cell proliferation in head and neck squamous cell carcinoma cells

The 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitors, also called statins, are commonly used as lipid-lowering drugs that inhibit cholesterol biosynthesis. An anticancer effect, as a pleiotropic function of certain statins, has been hypothesized. In the present study, we investigated the effect of simvastatin, one of the natural statins, on cell proliferation, cell cycle, invasive activity, and molecular expressions associated with cell-extracellular matrix adhesion, signal transduction, and DNA synthesis in Tu167 and JMAR cells from head and neck squamous cell carcinoma. The addition of simvastatin resulted in a dose-dependent inhibition of cell growth and migration into the extracellular matrix. Considerable morphological changes occurred after treatment with simvastatin, demonstrating loss of cell adhesion and disruption of actin filaments in cytoplasm. The inhibitory effect of simvastatin on cell proliferation seemed to be associated with cell cycle arrest and increased expression of p21, p27, and activated caspase-3. The expression of beta1-integrin, a counter adhesion for the extracellular matrix, phosphorylated FAK, and phosphorylated ERK was decreased by treatment with simvastatin. The proapoptotic effect of simvastatin was inhibited by treatment with mevalonate. cDNA microarray assay demonstrated that molecular changes resulting from treatment with simvastatin included the up-regulation of cell cycle regulators and apoptosis-inducing factors and the down-regulation of integrin-associated molecules and cell proliferation markers. Of down-regulated genes induced by simvastatin treatment, a significant depletion of thymidylate synthase was confirmed using western blot analysis. These results imply that simvastatin has the potential to be effective for the prevention of the growth and metastasis of cancer cells.

Simvastatin induces apoptosis in human breast cancer cells: p53 and estrogen receptor independent pathway requiring signalling through JNK

The effect of simvastatin, a widely used statin for the treatment of hypercholesterolemia, was investigated in the estrogen receptor (ER)-positive MCF-7, and the ER-negative MDA-MB 231 human breast cancer cell lines. Simvastatin induced cell cycle arrest and apoptosis in both cells. These effects of simvastatin were not altered by 17-beta-estradiol treatment. MCF-7 cells express wild-type tumor suppressor protein p53, whereas MDA-MB 231 cells carry a p53 mutation. However, no alteration in the level or localisation of p53 was observed with simvastatin treatment in either cell line. On the other hand, simvastatin strongly stimulated phosphorylation of c-jun which was completely abolished by the c-jun NH2-terminal kinase (JNK) inhibitor SP600125, which also significantly reduced the antiproliferative and apoptotic effects of simvastatin in these cells. In conclusion, we describe here that simvastatin induces apoptosis via involvement of JNK in breast cancer cells independent of their ER or p53 expression status. These findings indicate a great potential for statins for the treatment of cancers resistant to currently used drugs, and target the JNK signalling pathway for a novel approach of breast cancer treatment.

Statins and risk of cancer: a systematic review and metaanalysis

We conducted a systematic review of the association between HMG-CoA reductase inhibitor (statin) use and cancer risk. We searched MEDLINE, EMBASE, Web of Science, ISI Proceedings and BIOSIS Previews bibliographic databases, electronic trials registers and reference lists for potentially eligible randomized trials and observational studies. Thirty-eight individual studies (26 randomized trials involving 103,573 participants and 12 observational studies with 826,854 participants) were included. Median follow-up was 3.6 and 6.2 years for trials and observational studies, respectively. In metaanalyses of randomized trials, there was no evidence that statin therapy was associated with incidence of all-cancers (26 trials; pooled risk ratio = 1.00; 95% CI 0.95-1.05; I(2) = 0%) or the following site-specific cancers: breast (7 trials; risk ratio = 1.01; 0.79-1.30; I(2) = 43%), prostate (4 trials; risk ratio = 1.00; 0.85-1.17; I(2) = 0%), colorectum (9 trials; risk ratio = 1.02; 0.89-1.16; I(2) = 0%), lung (9 trials; risk ratio = 0.96; 0.84-1.09; I(2) = 0%), genito-urinary (5 trials; risk ratio = 0.95; 0.83-1.09; I(2) = 0%), melanoma (4 trials; risk ratio = 0.86; 0.62-1.20; I(2) = 17%) or gastric (1 trial; risk ratio = 1.00; 0.35-2.85). There was no evidence of differential effects by length of follow-up, statin type (lipophilic vs. lipophobic) or potency. Trial results were generally consistent with observational studies. We conclude that statin use is not associated with short-term cancer risk, but longer-latency effects remain possible.

Identification of molecular markers and signaling pathway in endometrial cancer in Hong Kong Chinese women by genome-wide gene expression profiling

Endometrial cancer is the third most common gynecologic malignancy and the ninth most common malignancy for females overall in Hong Kong. Approximately 80% or more of these cancers are endometrioid endometrial adenocarcinomas. The aim of this study was to reveal genes contributing to the development of endometrioid endometrial cancer, which may impact diagnosis, prognosis and treatment of the disease. Whole-genome gene expression analysis was completed for a set of 55 microdissected sporadic endometrioid endometrial adenocarcinomas and 29 microdissected normal endometrium specimens using the Affymetrix Human U133 Plus 2.0 oligonucleotide microarray. Selected genes of interest were validated by quantitative real-time-polymerase chain reaction (qRT-PCR). Pathway analysis was performed to reveal gene interactions involved in endometrial tumorigenesis. Unsupervised hierarchical clustering displayed a distinct separation between the endometrioid adenocarcinomas and normal endometrium samples. Supervised analysis identified 117 highly differentially regulated genes (>or=4.0-fold change), which distinguished the endometrial cancer specimens from normal endometrium. Twelve novel genes including DKK4, ZIC1, KIF1A, SAA2, LOC16378, ALPP2, CCL20, CXCL5, BST2, OLFM1, KLRC1 and MBC45780 were deregulated in the endometrial cancer, and further validated in an independent set of 56 cancer and 29 normal samples using qRT-PCR. In addition, 10 genes were differentially regulated in late-stage cancer, as compared to early-stage disease, and may be involved in tumor progression. Pathway analysis of the expression data from this tumor revealed an interconnected network consisting of 21 aberrantly regulated genes involved in angiogenesis, cell proliferation and chromosomal instability. The results of this study highlight the molecular features of endometrioid endometrial cancer and provide insight into the events underlying the development and progression of endometrioid endometrial cancer.

Elevated levels of cholesterol-rich lipid rafts in cancer cells are correlated with apoptosis sensitivity induced by cholesterol-depleting agents

Lipid rafts/caveolae are membrane platforms for signaling molecules that regulate various cellular functions, including cell survival. To better understand the role of rafts in tumor progression and therapeutics, we investigated the effect of raft disruption on cell viability and compared raft levels in human cancer cell lines versus their normal counterparts. Here, we report that cholesterol depletion using methyl-beta cyclodextrin caused anoikis-like apoptosis, which in A431 cells involved decreased raft levels, Bcl-xL down-regulation, caspase-3 activation, and Akt inactivation regardless of epidermal growth factor receptor activation. Cholesterol repletion replenished rafts on the cell surface and restored Akt activation and cell viability. Moreover, the breast cancer and the prostate cancer cell lines contained more lipid rafts and were more sensitive to cholesterol depletion-induced cell death than their normal counterparts. These results indicate that cancer cells contain increased levels of rafts and suggest a potential use of raft-modulating agents as anti-cancer drugs.

Lipid phosphate phosphatase-2 activity regulates S-phase entry of the cell cycle in Rat2 fibroblasts

Lipid phosphates are potent mediators of cell signaling and control processes including development, cell migration and division, blood vessel formation, wound repair, and tumor progression. Lipid phosphate phosphatases (LPPs) regulate the dephosphorylation of lipid phosphates, thus modulating their signals and producing new bioactive compounds both at the cell surface and in intracellular compartments. Knock-down of endogenous LPP2 in fibroblasts delayed cyclin A accumulation and entry into S-phase of the cell cycle. Conversely, overexpression of LPP2, but not a catalytically inactive mutant, caused premature S-phase entry, accompanied by premature cyclin A accumulation. At high passage, many LPP2 overexpressing cells arrested in G(2)/M and the rate of proliferation declined severely. This was accompanied by changes in proteins and lipids characteristic of senescence. Additionally, arrested LPP2 cells contained decreased lysophosphatidate concentrations and increased ceramide. These effects of LPP2 activity were not reproduced by overexpression or knock-down of LPP1 or LPP3. This work identifies a novel and specific role for LPP2 activity and bioactive lipids in regulating cell cycle progression.

Statins and cancer development

There is epidemiologic evidence that the hydrophilic 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase inhibitor pravastatin increases the incidence of some extrahepatic cancers, although this finding has been attributed to chance. We hypothesize that pravastatin is able to promote the development of cancer by causing an induction of HMG-CoA reductase and, hence, mevalonate synthesis in extrahepatic tissues. We have shown that mevalonate, the product of HMG-CoA reductase, promotes the growth of breast cancer cells. Because there is no uptake of pravastatin by most extrahepatic cells, this statin will be unable to mitigate the increase in mevalonate synthesis in extrahepatic tissues that accompanies the decrease in circulating cholesterol caused by its inhibition of hepatic HMG-CoA reductase.

Regulation of HMG-CoA reductase in MCF-7 cells by genistein, EPA, and DHA, alone and in combination with mevastatin

We investigated the regulation of HMG-CoA reductase in MCF-7 human breast cancer cells by genistein, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). All three compounds down-regulated reductase activity, primarily through post-transcriptional effects. In mevastatin-treated cells, only genistein and DHA abrogated the induction of reductase activity caused by this competitive inhibitor. Diets rich in soy isoflavones and fish oils, therefore, may exert anti-cancer effects through the inhibition of mevalonate synthesis in the breast. Genistein and DHA, in particular, may augment the efficacy of statins, increasing the potential for use of these drugs in adjuvant therapy for breast cancer.

Advances that are changing the diagnosis and treatment of malignant bone tumors

PURPOSE OF REVIEW

Several neoplastic conditions may affect bone. These include primary bone tumors as well as metastatic disease from distant primary sites. Often, these entities produce symptoms that may be difficult to distinguish from those of various rheumatologic entities. The purpose of this review is to discuss recent developments in orthopedic oncology, with special attention given to advances that are changing the diagnosis and treatment of bone sarcomas and carcinomas metastatic to bone.

RECENT FINDINGS

Much effort in the field of musculoskeletal oncology has been dedicated to the elucidation of the molecular mechanisms underlying bone sarcomas, especially in the case of osteogenic sarcoma and Ewing family tumor. Telomere maintenance mechanisms are emerging as potential targets for anticancer therapy. The most exciting advances have been in the development of novel treatments for cancers affecting bone. The anticancer effects of bisphosphonates, cyclooxygenase-2 inhibitors, and statins may expand their indications to the treatment of primary bone tumors. Finally, new expandable implants have been developed for the treatment of bone tumors in growing children. These devices may help solve some of the problems encountered with reconstruction of the growing skeleton.

SUMMARY

Recent discoveries in the molecular mechanisms of bone sarcomas may help to elucidate the pathogenesis of these rare diseases. This, combined with the recent findings of the anticancer effects of bisphosphonates, cyclooxygenase-2 inhibitors, and statins, may lead to the development of novel treatments for sarcomas of bone and of carcinomas metastatic to bone.

Dietary factors and the regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase: Implications for breast cancer development

A role for mevalonate in cancer development has long been suggested by findings that 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity is elevated in malignant cells. Increased synthesis mevalonate and mevalonate-derived nonsterol isoprenoids supports increased cell proliferation through the activation of growth-regulatory proteins and oncoproteins, and by promoting DNA synthesis. We have recently shown that mevalonate promotes the growth of human breast cancer cells both in culture and as tumors grown in nude mice. Inhibition mevalonate synthesis, therefore, may be an effective strategy to impair the growth of malignant breast cells. Several dietary compounds with known anti-cancer effects are also reported to inhibit HMG-CoA reductase activity. Here, we review evidence suggesting that inhibition of mevalonate synthesis may mediate the protective effects of cholesterol, plant isoprenoids, genistein, and long-chain n-3 polyunsaturated fatty acids (PUFAs) on experimental breast cancer.