Inhibition of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase pathway induces p53-independent transcriptional regulation of p21(WAF1/CIP1) in human prostate carcinoma cells

Statin induces apoptosis and cell growth arrest in prostate cancer cells

Statins are a class of low molecular weight drugs that inhibit the rate-limiting enzyme of the mevalonate pathway 3-hydroxy-3-methylglutaryl-CoA reductase. Statins have been approved and effectively used to control hypercholesterolemia in clinical setting. Recent study showed statin's antitumor activity and suggested a potential role for prevention of human cancers. In this study, we did cell viability, DNA fragmentation, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays to evaluate the action of statins on prostate cancer cells and used Western blotting and RhoA activation assay to investigate the underlying molecular mechanism of action. Our data showed that lovastatin and simvastatin effectively decreased cell viability in three prostate cancer cell lines (PC3, DU145, and LnCap) by inducing apoptosis and cell growth arrest at G(1) phase. Both lovastatin and simvastatin induced activation of caspase-8, caspase-3, and, to a lesser extent, caspase-9. Both statins suppressed expression of Rb, phosphorylated Rb, cyclin D1, cyclin D3, CDK4, and CDK6, but induced p21 and p27 expression in prostate cancer cells. Furthermore, lovastatin and simvastatin suppressed RhoA activation and c-JUN expression, but not cyclooxygenase-2 expression. Our data showed that the antitumor activity of statins is due to induction of apoptosis and cell growth arrest. The underlying molecular mechanism of statin's action is mediated through inactivation of RhoA, which in turn induces caspase enzymatic activity and/or G(1) cell cycle. Future studies should focus on examining statins and other apoptosis-inducing drugs (e.g., cyclooxygenase-2 inhibitors or curcumin) together to assess their efficacy in prevention of prostate cancer.

Molecular markers and targets for colorectal cancer prevention

Colorectal cancer is the third most prevalent cancer in the world. If detected at an early stage, treatment often might lead to cure. As prevention is better than cure, epidemiological studies reveal that having a healthy diet often protects from promoting/ developing cancer. An important consideration in evaluating new drugs and devices is determining whether a product can effectively treat a targeted disease. There are quite a number of biomarkers making their way into clinical trials and few are awaiting the preclinical efficacy and safety results to enter into clinical trials. Researchers are facing challenges in modifying trial design and defining the right control population, validating biomarker assays from the biological and analytical perspective and using biomarker data as a guideline for decision making. In spite of following all guidelines, the results are disappointing from many of the large clinical trials. To avoid these disappointments, selection of biomarkers and its target drug needs to be evaluated in appropriate animal models for its toxicities and efficacies. The focus of this review is on the few of the potential molecular targets and their biomarkers in colorectal cancers. Strengths and limitations of biomarkers/surrogate endpoints are also discussed. Various pathways involved in tumor cells and the specific agents to target the altered molecular biomarker in biomolecular pathway are elucidated. Importance of emerging new platforms siRNAs and miRNAs technology for colorectal cancer therapeutics is reviewed.

Statin use and risk of prostate cancer in the California Men's Health Study cohort

Statins have known anticarcinogenic effects, however, evidence for long-term statin use as effective chemoprevention for prostate cancer is inconsistent. We examined the association between statin use and risk of prostate cancer among 69,047 eligible participants in the California Men's Health Study, a prospective cohort of Northern and Southern California Kaiser Permanente (KP) members, ages 45 to 69 years, initiated in 2002. Prostate cancer cases were identified by linkage to the KP California Cancer Registries. Statin exposure, estimated from automated KP outpatient pharmacy records (available since 1991 in Southern California and since 1994 in Northern California), was treated as time-varying and defined as the cumulative days dispensed of any statin from the first dispensing until a prostate cancer diagnosis, radical prostatectomy, termination of membership, or end of study (December 31, 2004). Cox proportional hazards models with age as the time scale were used to estimate rate ratios, while controlling for confounding variables. During follow-up, 888 prostate cancer cases, including 131 advanced cases, were identified. There was no association between ever statin use or <5 years use and prostate cancer. Conversely, >or=5 years use was associated with a 28% lower risk for prostate cancer compared with nonuse (adjusted rate ratio, 0.72; 95% confidence interval, 0.53-0.99). This association did not differ markedly for advanced disease. However, the association did seem to be restricted to those who regularly take nonsteroidal anti-inflammatory drugs. Our findings suggest that long-term statin use might be associated with a reduced risk of prostate cancer but perhaps only among regular nonsteroidal anti-inflammatory drug users.

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.

A new proteasome inhibitor, TP-110, induces apoptosis in human prostate cancer PC-3 cells

Proteasome inhibitors are useful in the treatment of cancer. Recently, we found a new proteasome inhibitor, TP-110, derived from tyropeptin A produced by Kitasatospora sp. Here we report that TP-110 induces apoptosis in human prostate cancer PC-3 cells. TP-110 showed strong cytotoxicity to PC-3 cells (IC(50)=0.05 muM). It increased the number of cells in the G(2)-M phase and increased the accumulated amounts of the p21 and p27 proteins, which are negative regulators of cell cycle progression. Furthermore, it induced apoptosis along with chromatin condensation and DNA fragmentation in PC-3 cells, and TP-110-induced apoptosis appeared to be associated with caspase activation. Additionally, TP-110 inhibited not only the degradation of IkappaB and the nuclear translocation of nuclear factor-kappaB (NF-kappaB), but also the DNA binding activity of NF-kappaB. These results indicate that TP-110 shows a strong growth inhibition and apoptosis in PC-3 cells.

Chemoprevention of familial adenomatous polyposis by low doses of atorvastatin and celecoxib given individually and in combination to APCMin mice

Preclinical and clinical studies have established evidence that cyclooxygenase-2 (COX-2) inhibitors and statins [hydroxy-3-methylglutaryl CoA reductase (HMGR) inhibitors] inhibit colon carcinogenesis. Chronic use of high doses of COX-2 inhibitors may induce side effects, and combining the low doses of agents may be an effective way to increase their efficacy and minimize the side effects. We assessed the chemopreventive efficacy of atorvastatin (Lipitor) and celecoxib individually or in combination in an animal model of familial adenomatous polyposis. Six-week-old male C57BL/6J-APCmin/+ mice were either fed diets containing 0 or 100 ppm atorvastatin or 300 ppm celecoxib, or a combination of both for approximately 80 days. Mice were sacrificed, and their intestines were scored for tumors. Normal-seeming mucosa and intestinal tumors were harvested and assayed for apoptosis (terminal deoxynucleotidyl transferase-mediated nick-end labeling) and HMGR and COX-2 protein expression and activity. We observed that 100 ppm atorvastatin significantly (P < 0.002) suppressed intestinal polyp formation. As anticipated, 300 ppm celecoxib decreased the rate of formation of intestinal polyps by approximately 70% (P < 0.0001). Importantly, the combination of 100 ppm atorvastatin and 300 ppm celecoxib in the diet suppressed the colon polyps completely and small intestinal polyps by >86% (P < 0.0001) compared with the control group. The inhibition of tumor formation by the atorvastatin and celecoxib combination was significant (P < 0.005) when compared with tumor inhibition by celecoxib alone. In addition, increased rates of apoptosis in intestinal tumors (P < 0.01-0.0001) were observed in animals fed with atorvastatin and celecoxib and more so with the combinations. Tumors of animals fed atorvastatin showed a significant decrease in HMGR-R activity. Similarly, tumors of mice exposed to celecoxib showed significantly lower levels of COX-2 activity. These observations show that atorvastatin inhibits intestinal tumorigenesis and that, importantly, when given together with low doses of celecoxib, it significantly increases the chemopreventive efficacy in an APC(min) mice.

Prevention of azoxymethane-induced colon cancer by combination of low doses of atorvastatin, aspirin, and celecoxib in F 344 rats

Preclinical and clinical studies have provided evidence that aspirin, celecoxib, (cyclooxygenase-2 inhibitor), and statins (3-hydroxy-3-methylglutaryl CoA reductase inhibitors) inhibit colon carcinogenesis. Chronic use of high doses of these agents may induce side effects in ostensibly normal individuals. Combining low doses of agents may be an effective way to increase their efficacy and minimize toxicity. We assessed the efficacy of atorvastatin (lipitor), celecoxib, and aspirin, given individually at high dose levels and in combination at lower doses against azoxymethane-induced colon carcinogenesis, in male F 344 rats. One day after the last azoxymethane treatment (15 mg/kg body weight, s.c., once weekly for 2 weeks), groups of male F 344 rats were fed the AIN-76A diet or AIN-76A diet containing 150 ppm atorvastatin, 600 ppm celecoxib, and 400 ppm aspirin, 100 ppm atorvastatin + 300 ppm celecoxib, and 100 ppm atorvastatin + 200 ppm aspirin. Rats were killed 42 weeks later, and colon tumors were processed histopathologically and analyzed for cell proliferation and apoptosis immunohistochemically. Administration of these agents individually and in combination significantly suppressed the incidence and multiplicity of colon adenocarcinomas. Low doses of these agents in combination inhibited colon carcinogenesis more effectively than when they were given individually at higher doses. Inhibition of colon carcinogenesis by these agents is associated with the inhibition of cell proliferation and increase in apoptosis in colon tumors. These observations are of clinical significance because this can pave the way for the use of combinations of these agents in small doses against colon cancer.

Rho/ROCK pathway as a target of tumor therapy

This study emphasizes the importance of Rho/ROCK pathway in lovastatin-induced apoptosis as replenishment with exogenous isoprenoid, geranylgeranylpyrophosphate (GGPP), resulted in inhibition of apoptosis in cultured tumor cells. Treatment of C6 glioma cells with Toxin B and exoenzyme C3 resulted in cell death suggesting the role of geranylgeranylated protein(s) in the survival of glioma cells. Relative apoptotic death observed in cells transfected with dominant negative constructs of RhoA, Rac, and cdc42 imply Rho A as playing the major role in cell survival. Furthermore, the inhibition of Rho A kinase (ROCK), a direct downstream effector of Rho A, by Y-27632 or dominant negative of ROCK, induced apoptosis in glioma cells. These findings indicate that RhoA/ROCK pathway is involved negatively in the regulation of glioma cell death pathway. Moreover, in vivo studies of lovastatin treatment in animals implanted with C6 glioma cell tumors also resulted in smaller tumor size and induced apoptosis in the tumor tissue. The implantation of stably transfected C6 glioma cells with expression vector of C3 exoenzyme, dominant negative of RhoA and ROCK, resulted in significant smaller tumor mass, further establishing the importance of geranylgeranylated proteins, specifically RhoA and its downstream effecter ROCK, in cell survival and tumor genesis.

Proapoptotic and antitumor activities of the HMG-CoA reductase inhibitor, lovastatin, against Dalton's lymphoma ascites tumor in mice

BACKGROUND

Diet rich in fat have a clear effect on the tumor incidence in humans. Increased level of lipid peroxidation were found in colon, liver, breast and kidney carcinogenesis. Although the beneficial effects of statins for cardiovascular diseases are well established, their importance in the area of cancer therapeutics has recently gained recognition. Many studies of lovastatin in in vitro systems and experimental animals have been reported as an effective antitumor agent. However, phase I/II clinical trials in cancer patients demonstrated a minor to non-significant responses. Hence more studies in different tumor models using doses corresponding to that used to reduce lipid in human are required to support the antitumor activity.

METHODS

The antitumor activity was evaluated using Daltons' Lymphoma Ascites (DLA) cell line-induced ascites tumor model in mice. Proapoptotic activity was evaluated in DLA cell line induced ascites animals after the treatment of lovastatin. Apoptosis was analyzed morphologically by staining with Giemsa and biochemically by observing the laddering of DNA in agarose gel electrophoresis. In vitro cytotoxic activity of lovastatin was studied by trypan blue dye exclusion method. Lipid peroxidation inhibiting activity was demonstrated in Fe2+-ascorbate induced rat whole liver homogenate.

RESULTS

Lovastatin dose dependently inhibited the ascites tumor growth at 4 and 16 mg/kg body wt (p.o). The percentage increase in life span (%ILS) in the 16 mg/kg treated group was 61.8% (P<0.01). Single dose of lovastatin (16 mg/kg body wt, p.o) was also effective to accelerate the apoptosis in the ascites tumor bearing mice that was evident from the multiple fragmentation of DNA in gel electrophoresis. Further the morphological analysis of DLA cells aspirated from the lovastatin treated animals showed a significant (P<0.01) increase of apoptotic cells (15.5+/-3%) than the control animals (6.5+/-1%). Concentration of lovastatin required for the 50% of the cytotoxicity was 37+/-5 microg/ml. Lovastatin at its low concentrations were effective to inhibit lipid peroxidation.

CONCLUSIONS

The antitumor activity of lovastatin against the ascites tumor is due to its proapoptotic and cytotoxic activities. Lovastatin at low concentrations inhibited Fe2+ induced lipid peroxidation in in vitro system. The proapoptotic and lipid peroxidation inhibiting activities of the lipid lowering drug lovastatin may further suggest its possible therapeutic use as a cancer chemopreventive agent.

Potent inhibition of small-cell lung cancer cell growth by simvastatin reveals selective functions of Ras isoforms in growth factor signalling

The impact of the 3-hydroxy-3methylglutaryl CoA reductase inhibitor simvastatin on human small-cell lung cancer (SCLC) cell growth and survival was investigated. Simvastatin profoundly impaired basal and growth factor-stimulated SCLC cell growth in vitro and induced apoptosis. SCLC cells treated with simvastatin were sensitized to the effects of the chemotherapeutic agent etoposide. Moreover, SCLC tumour growth in vivo was inhibited by simvastatin. These responses correlated with the inhibition of stem cell factor (SCF)-stimulated activation of extracellular signal-regulated kinase (Erk), protein kinase B (PKB) and ribosomal S6 kinase by simvastatin. Constitutive activation of the Erk pathway was sufficient to rescue SCLC cell from the effects of simvastatin. The drug did not directly affect activation of c-Kit or its localization to lipid rafts, but in addition to its ability to block Ras membrane localization, it selectively downregulated H-Ras protein levels at the post-translational level. Downregulation of either H- or K-Ras by RNA interference (RNAi) did not impair Erk activation by growth factors, whereas an RNAi specific for N-Ras inhibited activation of Erk, PKB and SCLC cell growth. Together our data demonstrate that inhibiting Ras signalling with simvastatin potently disrupts growth and survival in human SCLC cells.

Lovastatin-induced RhoA modulation and its effect on senescence in prostate cancer cells

Lovastatin inhibits a 3-hydroxy 3-methylglutaryl coenzyme A reductase and prevents the synthesis of cholesterol precursors, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), responsible for important cell signaling in cell proliferation and migration. Recently, the anti-cancer effect of lovastatin has been suggested in various tumor types. In this study, we showed that a low dose lovastatin induced senescence and G1 cell cycle arrest in human prostate cancer cells. Addition of GGPP or mevalonate, but not FPP, prevented the lovastatin-induced G1 phase cell cycle arrest and cell senescence. We found that constitutively active RhoA (caRhoA) reversed lovastatin-induced senescence in caRhoA-transfected PC-3 cells. Thus, we postulate that modulation of RhoA may be critical in lovastatin-induced senescence in PC-3 cells.

Aaptamine, a spongean alkaloid, activates p21 promoter in a p53-independent manner

Aaptamine, a benzonaphthyridine alkaloid was isolated from a marine sponge on the guidance of a bioassay using the transfected human osteosarcoma MG63 cells (MG63luc(+)). Aaptamine activated p21 promoter stably transfected in MG63 cells dose-dependently at the concentrations of 20-50microM. Expression of p21 and its mRNA in the wild-type MG63 cells also increased by aaptamine-treatment. Furthermore, the cell cycle of MG63 cells was arrested at the G2/M phase within 48h by the aaptamine-treatment. To analyze a responsive element of p21 promoter in the up-regulation of p21 by aaptamine, MG63 cells were transiently transfected with a series of the deleted or mutated promoter segments, and induction of luciferase with aaptamine treatment was examined by using these corresponding transfected cells. The activation of p21 promoter by aaptamine was led through acting Sp1 sites between -82 and -50bp in a p53-independent manner.

Impact of diet on prostate cancer: a review

Epidemiological studies suggest that environmental factors may mediate the transformation of latent prostate cancer into clinically apparent tumors and that diet appears to influence this progression. Close correlations between average per capita fat intake and prostate cancer mortality internationally generated interest in underlying mechanisms for this link, such as through serum levels of androgens, free radicals, proinflammatory fatty acid metabolites, or insulin-like growth factor. Much interest currently lies in the potential of HMG-CoA reductase inhibitors (statins) to play a chemopreventative role in prostate cancer. Lycopene, a potent antioxidant found in tomatoes, may exert a protective effect in the prostate. Selenium and vitamin E have also been shown to decrease the risk of prostate cancer in some men. Calcium may support vitamin D-related antiproliferative effects in prostate cancer. Certain soy proteins, common in the Asian diet, have been shown to inhibit prostate cancer cell growth. Finally, green tea may also have a chemopreventive effect by inducing apoptosis. Despite confounding factors present in clinical studies assessing the effect of diet on cancer risk, the data remain compelling that a variety of nutrients may prevent the development and progression of prostate cancer.

Statin Monotherapy Attenuates Renal Injury in a Salt-Sensitive Hypertension Model of Renal Disease

BACKGROUND

Several salutary biological effects of statins have been described. We sought to investigate more closely the anti-inflammatory and antiproliferative effects of simvastatin (SIMV) in a model of hypertension and progressive renal disease, as well as its effects on the cyclin-cdk inhibitors p21 and p27.

METHODS

Munich-Wistar rats received the nitric oxide (NO) synthase inhibitor L-NAME (25 mg/kg/day p.o.) for 20 days accompanied by a high-salt diet (HS, 3% Na) and then were kept on HS for 60 days. Animals were then divided into two groups: vehicle (VH) or SIMV 2 mg/kg/day p.o. Albuminuria and tail-cuff pressure were determined at 30 and 60 days. RT-PCR was done to assess renal expression of TGF-beta1, collagen I and III, fibronectin, p27, p21 and monocyte chemoattractant protein-1 (MCP-1). Renal protein expression was assessed by Western blot (proliferating cell nuclear antigen (PCNA)) and immunostaining (macrophage, lymphocyte, PCNA).

RESULTS

SIMV did not prevent the development of severe hypertension or albuminuria. SIMV-treated animals had less severe renal interstitial inflammation and cell proliferation. MCP-1 expression was significantly diminished in the SIMV-treated animals (55.4 +/- 7.3 vs. 84.4 +/- 8.2 OD, p = 0.02). mRNA renal expression for p27 and TGF-beta did not change between groups, but p21 mRNA renal expression, highly induced in this model, significantly decreased with SIMV treatment (31.6 +/- 6.6 vs. 50.2 +/- 5.8 OD, p < 0.05). The interstitial fibrosis score significantly decreased with SIMV (2.46 +/- 0.40 vs. 4.07 +/- 0.38%, p < 0.01), which was confirmed by a decrease in renal collagen I and fibronectin expression. Serum cholesterol level did not change with SIMV.

CONCLUSION

SIMV attenuated interstitial fibrosis associated with this model of hypertensive renal disease. The mechanism involved MCP-1 downregulation. SIMV treatment was also associated with a p21 downregulation in the kidney, which might be involved in the protection of renal scarring.

3-hydroxy-3-methylglutaryl-coenzyme a reductase inhibitor, fluvastatin, as a novel agent for prophylaxis of renal cancer metastasis

PURPOSE

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, also called statins, are currently used widely as a safe, effective therapeutic in the treatment of hypercholesterolemia. Recently, statins have been recognized for their activity against cancer. In the present study, we examined the effect of a synthetic statin, fluvastatin, on the development of renal cancer.

EXPERIMENTAL DESIGN

The effects of fluvastatin on cell viability, cell cycle, in vitro angiogenesis, and invasive properties were examined in murine renal cancer cell Renca. The changes in cell cycle-associated proteins, p21(Waf1/Cip1) and p53, and rac1 phosphorylation were analyzed by Western blotting. The prophylactic efficacy of fluvastatin to murine pulmonary metastasis of Renca was examined.

RESULTS

Fluvastatin inhibited in vitro growth of Renca cells in a time- and dose-dependent manner, with up to 70% inhibition at a concentration of 10 mumol/L. This inhibitory effect was due to cell cycle arrest at the G(1) phase and induction of apoptosis accompanied by up-regulation of p21(Waf1/Cip1) and p53. The invasive properties of Renca cells through Matrigel were inhibited by fluvastatin, with decreased phosphorylation of rac1. In vitro angiogenesis was also inhibited by fluvastatin. Furthermore, oral administration at doses of 1 to 10 mg/kg/d, for 12 days after inoculation of Renca cells via the tail vein, significantly decreased the amount of pulmonary metastasis.

CONCLUSIONS

Because our results suggest that fluvastatin may effectively inhibit in vitro tumor growth, invasion, angiogenesis, and metastasis of Renca cells, oral administration of fluvastatin could be a novel, safe, and effective agent for preventing metastasis of renal cancer.

Chloramphenicol-induced mitochondrial stress increases p21 expression and prevents cell apoptosis through a p21-dependent pathway

Pretreatment of HepG2 and H1299 cells with chloramphenicol rendered the cells resistant to mitomycin-induced apoptosis. Both mitomycin-induced caspase 3 activity and PARP activation were also inhibited. The mitochondrial DNA-encoded Cox I protein, but not nuclear-encoded proteins, was down-regulated in chloramphenicol-treated cells. Cellular levels of the p21(waf1/cip1) protein and p21(waf1/cip1) mRNA were increased through a p53-independent pathway, possibly because of the stabilization of p21(waf1/cip1) mRNA in chloramphenicol-treated cells. The p21(waf1/cip1) was redistributed from the perinuclear region to the cytoplasm and co-localized with mitochondrial marker protein. Several morphological changes and activation of the senescence-associated biomarker, SA beta-galactosidase, were observed in these cells. Both p21(waf1/cip1) antisense and small interfering RNA could restore apoptotic-associated caspase 3 activity, PARP activation, and sensitivity to mitomycin-induced apoptosis. Similar effects were seen with other antibiotics that inhibit mitochondrial translation, including minocycline, doxycycline, and clindamycin. These findings suggested that mitochondrial stress causes resistance to apoptosis through a p21-dependent pathway.

The potential of statins as part of anti-cancer treatment

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

HMG-CoA reductase inhibitors, statins, induce phosphorylation of Mdm2 and attenuate the p53 response to DNA damage

3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors, statins, are widely used cholesterol-lowering drugs and have been shown to have anticancer effects in many models. We have investigated the effect of statins on Mdm2, a p53-specific ubiquitin ligase. It was found that pravastatin induced Mdm2 phosphorylation at Ser166 and at 2A10 antibody-specific epitopes in HepG2 cells, while mRNA levels were unchanged. Furthermore, pravastatin was found to induce phosphorylation of mTOR at Ser2448. Ser166 phosphorylation of Mdm2 was abrogated by an inhibitor of mTOR, rapamycin, but not by the PI3-kinase inhibitors LY294002 and wortmannin. Ser166 phosphorylation of Mdm2 has been associated to active Mdm2 and has been shown to increase its ubiquitin ligase activity and lead to increased p53 degradation. Our data show that statins attenuated the p53 response to DNA damage. Thus, in HepG2 cells pravastatin and simvastatin pretreatment attenuated the p53 response to DNA damage induced by 5-fluorouracil and benzo(a)pyrene. Similar attenuation was induced when p53 stabilization was induced by the inhibitor of nuclear export, leptomycin B. Furthermore, in the DNA-damaged cells, half-lives of Mdm2 and p53 were decreased by statins, indicating a more rapid formation of p53/Mdm2 complexes and facilitated p53 degradation. The induction of p53 responsive genes and apoptosis was attenuated. Mdm2 and p53 were also studied in vivo in rat liver employing immunohistochemistry, and it was found that constitutive Mdm2 expression was changed in livers of pravastatin-treated rats. We also show that the p53 response to a challenging dose of diethylnitrosamine was attenuated in hepatocytes in situ and in primary cultures of hepatocytes by pravastatin pretreatment. Taken together, these data indicate that statins induce an mTOR-dependent Ser166 phosphorylation of Mdm2, and this effect may attenuate the duration and intensity of the p53 response to DNA damage in hepatocytes.

Simple, sensitive and rapid LC–MS/MS method for the quantitation of cerivastatin in human plasma — application to pharmacokinetic studies

A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for estimation of cerivastatin (I) in human plasma, a potent hydroxy-methylglutaryl-coenzyme A reductase inhibitor. The analyte and internal standard (atorvastatin, II) were extracted by liquid/liquid extraction with diethyl ether/dichloromethane (70/30, v/v). The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of water/acetonitrile (30/70, v/v) with 0.03% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 460.4 --> 356.3 and 559.2 --> 440.3 were used to measure I and II, respectively. The lower limit of quantitation was 10pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.01-10ng/mL). Sample analysis time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The assay can be used to analyze human plasma samples to support phase I and II clinical studies.

Studies of the isoprenoid-mediated inhibition of mevalonate synthesis applied to cancer chemotherapy and chemoprevention

Pools of farnesyl diphosphate and other phosphorylated products of the mevalonate pathway are essential to the post-translational processing and physiological function of small G proteins, nuclear lamins, and growth factor receptors. Inhibitors of enzyme activities providing those pools, namely, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase and mevalonic acid-pyrophosphate decarboxylase, and of activities requiring substrates from the pools, the prenyl protein transferases, have potential for development as novel chemotherapeutic agents. Their potentials as suggested by the clinical responses recorded in Phase I and II investigations of inhibitors of HMG CoA reductase (the statins), of mevalonic acid-pyrophosphate decarboxylase (sodium phenylacetate and sodium phenylbutyrate), and of farnesyl protein transferase (R115777, SCH66336, BMS-214662, Tipifarnib, L-778,123, and, prematurely, perillyl alcohol) are dimmed by dose-limiting toxicities. These nondiscriminant growth-suppressive agents induce G1 arrest and initiate apoptosis and differentiation, effects attributed to modulation of cell signaling pathways either by modulating gene expression, suppressing the post-translational processing of signaling proteins and growth factor receptors, or altering diacylglycerol signaling. Diverse isoprenoids and the HMG CoA reductase inhibitor, lovastatin, modulate cell growth, induce cell cycle arrest, initiate apoptosis, and suppress cellular signaling activities. Perillyl alcohol, the isoprenoid of greatest clinical interest, initially was considered to inhibit farnesyl protein transferase; follow-up studies revealed that perillyl alcohol suppresses the synthesis of small G proteins and HMG CoA reductase. In sterologenic tissues, sterol feedback control, mediated by sterol regulatory element binding proteins (SREBPs) 1a and 2, exerts the primary regulation on HMG CoA reductase activity at the transcriptional level. Secondary regulation, a nonsterol isoprenoid-mediated fine-tuning of reductase activity, occurs at the levels of reductase translation and degradation. HMG CoA reductase activity in tumors is elevated and resistant to sterol feedback regulation, possibly as a consequence of aberrant SREBP activities. Nonetheless, tumor reductase remains sensitive to isoprenoid-mediated post-transcriptional downregulation. Farnesol, an acyclic sesquiterpene, and farnesyl homologs, gamma-tocotrienol and various farnesyl derivatives, inhibit reductase synthesis and accelerate reductase degradation. Cyclic monoterpenes, d-limonene, menthol and perillyl alcohol and beta-ionone, a carotenoid fragment, lower reductase mass; perillyl alcohol and d-limonene lower reductase mass by modulating translational efficiency. The elevated reductase expression and greater demand for nonsterol products to maintain growth amplify the susceptibility of tumor reductase to isoprenoids, therein rendering tumor cells more responsive than normal cells to isoprenoid-mediated growth suppression. Blends of lovastatin, a potent nondiscriminant inhibitor of HMG CoA reductase, and gamma-tocotrienol, a potent isoprenoid shown to post-transcription-ally attenuate reductase activity with specificity for tumors, synergistically affect the growth of human DU145 and LNCaP prostate carcinoma cells and pending extensive preclinical evaluation, potentially offer a novel chemotherapeutic strategy free of the dose-limiting toxicity associated with high-dose lovastatin and other nondiscriminant mevalonate pathway inhibitors.

Kinetic profiles of p300 occupancy in vivo predict common features of promoter structure and coactivator recruitment

Understanding the language encrypted in the gene regulatory regions of the human genome is a challenging goal for the genomic era. Although customary extrapolations from steady-state mRNA levels have been effective, deciphering these regulatory codes will require additional empirical data sets that more closely reflect the dynamic progression of molecular events responsible for inducible transcription. We describe an approach using chromatin immunoprecipitation to profile the kinetic occupancy of the transcriptional coactivator and histone acetyltransferase p300 at numerous mitogen-induced genes in activated T cells. Comparison of these profiles reveals a class of promoters that share common patterns of inducible expression, p300 recruitment, dependence on selective p300 domains, and sensitivity to histone deacetylase inhibitors. Remarkably, this class also shares an evolutionarily conserved promoter composition and structure that accurately predicts additional human genes with similar functional attributes. This "reverse genomic" approach will have broad application for the genome-wide classification of promoter structure and function.

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor (pravastatin) inhibits endothelial cell proliferation dependent on G1 cell cycle arrest

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors have been developed as lipid-lowering drugs, and are well recognized to reduce morbidity and mortality from coronary artery disease. Several recent experimental studies have focused on the inhibitory effects of HMG-CoA reductase inhibitor on tumor cell growth in vitro and in vivo, dependent on a direct effect on cancer cells. In the present study, we aimed to investigate the potential anti-angiogenic effect of pravastatin and its mechanism of action. Using human umbilical vein endothelial cells (HUVECs) as a model of angiogenesis, we investigated the effect of pravastatin on the various steps of angiogenesis, including endothelial cell proliferation and adhesion to extracellular matrix proteins. Pravastatin induced a dose-dependent decrease in the proliferative activity of endothelial cells, which was dependent on the cell cycle arrest to the G1 phase and not on cell apoptosis. G1 arrest was due to the decrease of cyclin D, cyclin E and cyclin-dependent kinase 2 levels. In addition, pravastatin inhibited tube formation on Matrigel and adhesion to extracellular matrix, but did not affect matrix metalloproteinase production. The present results demonstrate the anti-angiogenic activity of pravastatin and its potential use as an anticancer drug is suggested.

Expression of a Dominant Negative Heat Shock Factor-1 Construct Inhibits Aneuploidy in Prostate Carcinoma Cells*

Recent studies have implicated heat shock proteins (HSP) and heat shock transcription factor 1 (HSF1) in tumor progression. We have examined the role of HSF1 in the malignant phenotype of PC-3 prostate carcinoma cells. We have developed a dominant negative construct of HSF1 that antagonizes transcription from HSP promoters and results in the depletion of intracellular HSP 70. Our studies indicate that expression of DN-HSF1 dramatically alters the DNA content of PC-3 cells (derived from p53 null prostatic carcinoma) and inhibits aneuploidy in these cells. This effect is due to prolonged expression of DN-HSF1, and transient expression of the dominant negative factor from an inducible promoter failed to cause the effect. Inhibition of aneuploidy in p53 null PC-3 cells by DN-HSF1 expression was recapitulated by expression within the cells of wild type p53. Furthermore, cells expressing DN-HSF1 showed a profound inhibition in the development of aneuploidy when exposed to chemical agents that disrupt the mitotic spindle and prevent progression through metaphase. Inhibition of aneuploidy in PC-3 cells expressing DN-HSF1 was associated with delayed breakdown of cyclin B1 compared with controls, consistent with a role for wild type HSF1 in the regulation of cyclin B1 degradation, a key step in the control of mitosis. Our experiments therefore demonstrate that HSF1 plays a functional role in cancer cells under nonstress conditions and influences cell cycle behavior and progression through mitosis and promotes the development of the aneuploid state.

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.

Abrogation of p21 Expression by Flavopiridol Enhances Depsipeptide-Mediated Apoptosis in Malignant Pleural Mesothelioma Cells

PURPOSE

Recent insights regarding the pathogenesis of malignant pleural mesothelioma (MPM) provide new opportunities for targeted molecular therapies for this highly lethal disease. The present study was undertaken to examine the effects of the histone deacetylase inhibitor, Depsipeptide (DP) FK228, in conjunction with the cyclin-dependent kinase inhibitor, Flavopiridol (FLA), in cultured MPM cells.

EXPERIMENTAL DESIGN

Proliferation and apoptosis in drug-treated, virally transduced, or control cells were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and Apo-bromodeoxyuridine techniques. Western blot and ELISA techniques were used to examine signal transduction and cell cycle-related protein levels in MPM cells exposed to DP and/or FLA in the presence or absence of calphostin, phorbol-12,13-dibutyrate, 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole, or adenoviral p21 transduction.

RESULTS

DP (1-50 ng/ml x 6 h) or FLA (100-200 nM x 72 h) alone, mediated low-level, dose-dependent growth inhibition in MPM cells. In contrast, sequential DP/FLA treatment mediated marked growth inhibition and apoptosis in these cell lines. The cytotoxic effects of DP/FLA were considerably less pronounced in cultured normal cells. The proapoptotic effects of DP/FLA treatment coincided with inhibition of DP-mediated induction of p21 by FLA. Overexpression of p21 by adenoviral gene transfer techniques rendered MPM cells refractory to the cytotoxic effects of this treatment regimen. In p21 reporter assays, promoter activation by DP was antagonized by FLA. The magnitude of inhibition of DP-mediated p21 induction by FLA exceeded that observed with the pTEFb antagonist 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole. Calphostin C abrogated p21 induction mediated by DP and enhanced DP-mediated apoptosis in a manner comparable with FLA in MPM cells; in contrast, phorbol-12,13-dibutyrate blocked FLA-mediated inhibition of p21 induction by DP and markedly protected these cells from the apoptotic effects of sequential DP/FLA.

CONCLUSIONS

FLA abrogates DP-mediated induction of p21 expression, in part, via inhibition of protein kinase C signaling and markedly potentiates the cytotoxic effects of DP in MPM cells.

Involvement of cholesterol-rich lipid rafts in interleukin-6-induced neuroendocrine differentiation of LNCaP prostate cancer cells

IL-6 is an inflammatory cytokine that has been linked to aggressive prostate cancer (PCa). Previous studies have demonstrated that IL-6 can enhance the differentiation of PCa cells toward a neuroendocrine (NE) phenotype, a possible indicator of hormone-refractory disease. In this report, we present evidence that the mechanism of IL-6-stimulated NE differentiation employs a detergent-resistant (lipid raft) membrane compartment for signal transduction in LNCaP PCa cells. Signal transducer and activator of transcription (STAT)3, a mediator of IL-6 signaling, was rapidly phosphorylated and translocated to the nucleus in LNCaP cells treated with IL-6. Both processes were inhibited by filipin, a cholesterol-binding compound that disrupts plasma membrane lipid rafts. Isolation of Triton X-100-insoluble raft fractions from LNCaP cells by discontinuous sucrose gradient centrifugation demonstrated that the 80-kDa IL-6 receptor localized almost exclusively to the raft compartment. Although STAT3 was located predominantly in the Triton X-100-soluble subcellular fraction in exponentially growing cells, abundant phosphorylated STAT3 was detected in the raft fraction after stimulation with IL-6. Increases in expression of the NE marker, neuron-specific enolase, and neuron-specific enolase promoter activity after IL-6 treatment were reduced after membrane rafts were disrupted by filipin treatment. LNCaP cells expressed the raft-resident proteins flotillin-2 and G(ialpha2), but notably not caveolins, the predominant structural protein present in caveolar membrane rafts in many tissues and tumor cells. These results are the first to define a role for lipid raft membrane microdomains in signal transduction mechanisms capable of promoting the NE phenotype in PCa cells, and they demonstrate that the raft compartment is capable of mediating such signals in the absence of caveolins. Our results also suggest a mechanistic role for membrane cholesterol in cell signaling events relevant to PCa progression.

Opposite effects of Ha-Ras and Ki-Ras on radiation-induced apoptosis via differential activation of PI3K/Akt and Rac/p38 mitogen-activated protein kinase signaling pathways

It has been well known that Ras signaling is involved in various cellular processes, including proliferation, differentiation, and apoptosis. However, distinct cellular functions of Ras isozymes are not fully understood. Here we show the opposing roles of Ha-Ras and Ki-Ras genes in the modulation of cell sensitivity to ionizing radiation. Overexpression of active isoform of Ha-Ras (12V-Ha-Ras) in Rat2 cells increases resistance to the ionizing radiation. Constitutive activation of phosphoinositide-3-kinase (PI3K) and Akt is detected specifically in 12V-Ha-Ras-overexpressing cells. The specific PI3K inhibitor LY294002 inhibits PI3K/Akt signaling and potentiates the radiation-induced apoptosis, suggesting that activation of the PI3K/Akt signaling pathway is involved in the increased radio-resistance in cells overexpressing 12V-Ha-Ras. Overexpression of activated Ki-Ras (12V-Ki-Ras), on the other hand, markedly increases radiation sensitivity. The p38 mitogen-activated protein kinase (MAPK) activity is selectively enhanced by ionizing radiation in cells overexpressing 12V-Ki-Ras. The specific p38 MAPK inhibitor, PD169316, or dominant-negative p38 MAPK decreases radiation-induced cell death. We further show that the mechanism that underlies potentiation of cell death in cells overexpressing 12V-Ki-Ras involves Bax translocation to the mitochondrial membrane. Elevated Bax translocation following ionizing irradiation in 12V-Ki-Ras-overexpressing cells is completely inhibited by PD169316 or dominant-negative p38 MAPK. In addition, introduction of cells with RacN17, a dominant-negative mutant of Rac, resulted in a marked inhibition of radiation-induced Bax translocation and apoptotic cell death as well as p38 MAPK activation. Taken together, these findings explain the opposite effects of Ha-Ras and Ki-Ras on modulation of radiosensitivity, and suggest that differential activation of PI3K/Akt and Rac/p38 MAPK signaling by Ha-Ras and Ki-Ras may account for the opposing response to the ionizing radiation. These data provide an explanation for the diverse biological functions of Ras isozymes, and partly accounts for the differential response of transformed cells to anticancer treatments.

p21-dependent inhibition of colon cancer cell growth by mevastatin is independent of inhibition of G1 cyclin-dependent kinases

Mevastatin arrested HCT116 colon cancer cells at the G1/S transition and increased cellular levels of p21CIP1/WAF1. p21-deficient colon cancer cells continued to proliferate in the presence of mevastatin. Although p21 was necessary for the G1/S block, the G1 cyclin-dependent kinases (Cdks) cyclin E-Cdk2 and cyclin D-Cdk4 remained active. Despite the activity of the G1 Cdks the retinoblastoma protein was hypophosphorylated due to unknown mechanisms that were dependent on the p21 protein. The resulting decrease in cyclin A mRNA and protein led to a decrease in the activity of cyclin A-Cdk2. Therefore, although p21 was required for the G1/S arrest of HCT116 colon cancer cells by mevastatin, its mode of action was more complicated than the simple formation of a physical complex with cyclin-Cdk2. This mechanism of inhibition is different from that seen in prostate cancer cells (Ukomadu, C., and Dutta, A. (2003) J. Biol. Chem. 278, 4840-4846) where the activating phosphorylation of cyclin E-Cdk2 is suppressed and p21 is not required, suggesting the existence of cell line-specific differences in the mechanism by which statins arrest the cell cycle.

Unique induction of p21(WAF1/CIP1)expression by vinorelbine in androgen-independent prostate cancer cells

To study the mechanisms of the development of hormone refractory prostate cancer, we established an androgen-independent (AI) prostate cancer cell line derived from hormone-dependent (AD) LNCaP cells. Our previous studies have demonstrated that AI cells are deficient in expression of p21(WAFl/CIP1) (p21) due to overexpressed AR and are resistant to apoptosis. In this study, the induction of p53 and p21 expression by vinorelbine (Navelbine) was compared between AD and AI cells in an attempt to understand the difference(s) in apoptotic signalling pathways in these cells. Using a series of deletion of p21 reporter constructs, we found that vinorelbine mediated p21 induction in a p53-dependent manner in AD cells. In contrast, p21 expression restored by vinorelbine in AI cells was found to be through both p53-dependent and-independent pathways. In the absence of two p53 binding sites, Spl-3 and Spl-4 sites, in the promoter of human p21 gene, were found to be required for vinorelbine-mediated p21 activation. No p21 induction was observed by paclitaxel in AI cells. Exposure of AI cells to paciltaxel followed by vinorelbine produced synergism. Our data, thus, provide a basis for the synergistic combination of vinorelbine and paclitaxel for the treatment of advanced prostate cancer.

Apoptosis and modulation of cell cycle control by synthetic derivatives of ursodeoxycholic acid and chenodeoxycholic acid in human prostate cancer cells

The effects of synthetic derivatives of ursodeoxycholic acid (UDCA), HS-1183, and chenodeoxycholic acid (CDCA), HS-1199 and HS-1200, on the proliferation of human prostate carcinoma PC-3 cells were investigated. Whereas CDCA and UDCA had no effects on the growth of cells in a concentration range we have tested, HS-1199 and HS-1200 completely inhibited the cell proliferation, and HS-1183 showed a weak inhibitory activity. This proliferation-inhibitory effect of the synthetic bile acid derivatives was due to the induction of apoptosis, which was confirmed by observing DNA fragmentation, chromatin condensation and cleavage of PARP. Flow cytometric analysis also revealed that the synthetic bile acid derivatives arrested the cell cycle progression at the G1 phase, which effects were associated with inhibition of phosphorylation of pRB and enhanced binding of pRB and E2F-1. They also suppressed Cdk2 and cyclin E-dependent kinase activities without changes of their expressions. Furthermore, the synthetic bile acids increased the levels of Cdk inhibitor, p21WAF1/CIP1, expression and activated the reporter construct of p21WAF1/CIP1 promoter in p53-independent manner, and p21WAF1/CIP1 proteins induced by the synthetic bile acid derivatives were associated with Cdk2 and proliferating cell nuclear antigen. These distinctive features suggest that it is possible to create the new drugs useful for cancer therapy from the synthetic bile acid derivatives as lead compounds.

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.

Chemopreventive effect of farnesol and lanosterol on colon carcinogenesis

Cholesterol metabolites play a several critical roles in regulating cell growth and function. 3-Hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, the rate-limiting enzyme for this pathway, is down regulated by feedback mechanisms due to increased levels of cholesterol and its premetabolites. Several HMG-CoA metabolites, such as farnesyl pyrophosphate and geranyl pyrophosphate are implicated in oncogene activation and tumorigenesis. Recent studies suggest that inhibition of HMG-CoA reductase by specific inhibitors or by naturally-occurring phytochemicals, such as farnesol or squalene can modulate tumor cell growth. Thus, in this study, we have assessed the chemopreventive efficacy of farnesol and lanosterol on azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) in rats. In addition, we measured the effect of farnesol and lanosterol on serum high denisity lipoprotein (HDL) and cholesterol levels in the rats. Seven-week-old male F344 rats were fed the control diet (modified AIN-76A) or experimental diets containing I or 2% lanosterol or 1.5% farnesol. One week later, all animals except those in vehicle (normal saline)-treatment groups were s.c. injected with AOM (15 mg/kg body weight, once weekly for 2 weeks). At 16 weeks of age, all rats were killed, colons were evaluated for ACF and serum was assayed for HDL and cholesterol levels. Administration of dietary farnesol significantly inhibited ACF formation by about 34% (P < 0.001) and reduced crypt multiplicity by about 44% (P < 0.0001). Also, administration of lanosterol at dose levels of I or 2 % in the diet significantly suppressed AOM-induced colonic ACF as well as multicrypt foci formation. (P < 0.01-0.001). Further, farnesol at 1.5% and lanosterol at 1% did not show any significant effect on serum HDL nor on total cholesterol levels. However, lanosterol at 2% significantly increased serum HDL (P < 0.05) and cholesterol (P < 0.01) levels. That farnesol and lanosterol significantly suppress colonic ACF formation and crypt multiplicity strengthens the hypothesis that these agents possess chemopreventive activity against colon carcinogenesis.

Prostate Cancer Prevention: What Do We Know Now, and When Will We Know More?

Prostate cancer prevention is now one of the most aggressively investigated areas of urologic oncology, with > 30,000 men currently participating in clinical trials in the United States alone. The Prostate Cancer Prevention Trial will complete end-of-study prostate biopsies in May 2004, and the Selenium and Vitamin E Cancer Prevention Trial is rapidly reaching its accrual goal 1-2 years ahead of schedule. These 2 studies will give definitive answers regarding 3 of the most important potential preventive interventions: finasteride, vitamin E, and selenium. Many phase II and biomarker-modulation studies are also ongoing, testing a host of other interventions. It is hoped that, within a short period of time, the clinician will be provided with strategies to reduce the risk of the disease.

Inhibition of cdk2 activating phosphorylation by mevastatin

Phosphorylation of cdk2 on threonine 160 is essential for kinase activity. Mevastatin, an inhibitor of cholesterol synthesis, inhibits cell growth through inhibition of cdk2 and this has been suggested to be due to enhancement of p21 levels. In a prostate cancer cell line, PC3, mevastatin treatment led to elevated levels of p21 and caused a small increase in the p21 associated with cdk2. However, this increase in the associated p21 appeared out of proportion with the resulting dramatic inhibition of kinase activity. Using RNA interference we show that mevastatin inhibits cdk2 activity despite lack of induction of p21, p27, and p57. Instead the kinase was inhibited due to a decrease in activating phosphorylation. Phosphorylation of cdk2 from mevastatin-treated cells with exogenous cyclin-dependent kinase (cdk)-activating enzymes restored its functional activity. The only known mammalian cyclin H.cdk7.mat1 complex (cdk2-activating kinase, Cak), was not inhibited by mevastatin, suggesting either that a different CAK is responsible for cdk2 phosphorylation in vivo or that the regulation is at the level of substrate accessibility or of cdk2 dephosphorylation. These results suggest that mevastatin inhibits cdk2 activity in PC3 cells through the inhibition of Thr-160 phosphorylation of cdk2, providing a novel example of regulation of cdk2 at this level.

Plant-derived monoterpenes suppress hamster kidney cell 3-hydroxy-3-methylglutaryl coenzyme a reductase synthesis at the post-transcriptional level

The rate-limiting enzyme for mevalonate and cholesterol synthesis in mammalian cells is 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase. Control occurs through both transcriptional and post-transcriptional actions signaled by the end product, cholesterol, and by isoprenoid intermediates. End products of plant mevalonate metabolism, i.e., plant-derived isoprenoids, also suppress mammalian HMG-CoA reductase. Previous studies reported that isoprenoids suppress reductase synthesis at a post-transcriptional level. We tested the hypothesis that plant-derived isoprenoids also regulate mammalian HMG-CoA reductase synthesis at a post-transcriptional level by incubating lovastatin-treated C100 cells with mevalonate or a plant-derived isoprenoid (the monoterpenes, limonene, perillyl alcohol or geraniol) either alone or combined with the oxysterol, 25-hydroxycholesterol (25-OH C). Mevalonate decreased HMG-CoA reductase synthesis and mRNA levels by 65 and 66%, respectively (P < 0.05). The cyclic monoterpenes, limonene and perillyl alcohol, lowered HMG-CoA reductase synthesis by 70 and 89%, respectively (P < 0.05); although neither reduced HMG-CoA reductase mRNA levels (P = 0.88). Geraniol, an acyclic monoterpene, suppressed HMG-CoA reductase synthesis by 98% and lowered mRNA levels by 66% (P < 0.05). A combination of 25-OH C and either mevalonate or any three monoterpenes reduced HMG-CoA reductase mRNA levels (P < 0.05) compared with lovastatin-only treated cells. However, the dual combination of 25-OH C and either mevalonate or a monoterpene resulted in a greater decrease in HMG-CoA reductase synthesis than in mRNA levels. The difference between changes in HMG-CoA reductase synthesis and mRNA levels reflects a specific effect of isoprenoids on HMG-CoA reductase synthesis at the translational level. Mevalonate enhanced HMG-CoA reductase degradation, but no such effect was observed for the monoterpenes. These results indicate that the three plant-derived isoprenoids primarily suppress HMG-CoA reductase synthesis at a post-transcriptional level by attenuating HMG-CoA reductase mRNA translational efficiency.

Cerivastatin enhances the cytotoxicity of 5-fluorouracil on chemosensitive and resistant colorectal cancer cell lines

Cerivastatin is one of the synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors used for the treatment and prevention of hypercholesterolaemia. The observation that patients receiving this drug had a lower incidence at cancer led to our interest in using it as a putative anticancer agent. In this study, we tested the cytotoxicity of cerivastatin on a panel of 5-fluorouracil (5FU) sensitive and resistant cell lines in vitro. Cerivastatin was cytotoxic to both 5FU sensitive and resistant cells. Cerivastatin significantly augmented the cytotoxic effect of 5FU on drug sensitive (6-22-fold) and resistant (229-310-fold) cell lines. Cerivastatin and 5FU acted synergistically. Cerivastatin inhibited nuclear factor kappaB DNA binding activity. The enhancing effect of cerivastatin on 5FU was partially mevalonate pathway independent. Cerivastatin may allow successful 5FU therapy in chemoresistant patients.

Anticancer-drug-induced apoptotic cell death in leukemia cells is associated with proteolysis of beta-catenin

beta-Catenin is a known regulator of cell-cell adhesion and transcriptional regulation. However, the role of beta-catenin and its regulation in non-adherent cells has not been examined. Therefore, we examined the role and fate of beta-catenin during hematopoietic cell apoptosis using Jurkat T-acute lymphoblastic and U937 acute myeloblastic leukemia cells. The results presented here demonstrate that the treatment of Jurkat cells with the apoptosis inducers anti-Fas, TRAIL, staurosporine, and etoposide induces proteolytic fragments of beta-catenin, as did TRAIL and staurosporine in U937 cells. In Jurkat cells, beta-catenin was cleaved at both the N- and C-terminal after anti-Fas addition. Cleavage of intact beta-catenin was completely inhibited by caspase selective protease inhibitors. There was a clear accumulation of the large proteolytic fragment in Jurkat cells treated with lactacystin or N-acetyl-leucyl leucyl-methioninal (ALLM). These results suggest that both the proteasome and calpain may recognize the large beta-catenin fragment as a substrate for further degradation. Densitometric analysis demonstrated that the loss of intact beta-catenin was more rapid in the cell nucleus (beta-catenin T1/2 of approximately 1.5h in cytoplasm and 0.5h in nucleus). Down-regulation of beta-catenin-associated transcription was an early event in response to anti-Fas. These results suggest that beta-catenin plays a role in promoting Jurkat survival.

Hepatitis C virus core protein represses the p21 promoter through inhibition of a TGF-beta pathway

The increased proliferation rate of hepatocytes is one of the major risk factors for the development of hepatocellular carcinoma. In this study, we investigated the mechanism by which hepatitis C virus (HCV) core protein represses transcription of the universal cyclin-dependent kinase inhibitor p21 gene in murine fibroblast NIH 3T3 cells. From the transient reporter assays of p21 promoter, we found that the TGF-beta-responsive element (TbetaRE) located between -83 and -74 of the p21 promoter is responsible for the effect. The TGF-beta-induced p21 promoter activity was specifically decreased by HCV core protein and in the presence of the inhibitory Smad7 the repression effect was almost completely abolished. Furthermore, HCV core protein stimulated the growth rate of NIH 3T3 cells and could overcome growth arrest by TGF-beta but not by butyrate, suggesting that HCV core protein stimulates cell cycle progression by repressing p21 transcription through a TGF-beta pathway.

Regulation of leukemic cell adhesion, proliferation, and survival by beta-catenin

In epithelial cells beta-catenin plays a critical role as a component of the cell-cell adhesion apparatus and as a coactivator of the TCF/LEF (T-cell transcription factor/lymphoid enhancer binding factor) family of transcription factors. Deregulation of beta-catenin has been implicated in the malignant transformation of cells of epithelial origin. However, a function for beta-catenin in hematologic malignancies has not been reported. beta-Catenin is not detectable in normal peripheral blood T cells but is expressed in T-acute lymphoblastic leukemia cells and other tumor lines of hematopoietic origin and in primary lymphoid and myeloid leukemia cells. beta-Catenin function was examined in Jurkat T-acute lymphoblastic leukemia cells. Overexpression of dominant-negative beta-catenin or dominant-negative TCF reduced beta-catenin nuclear signaling and inhibited Jurkat proliferation and clonogenicity. Similarly, these constructs inhibited proliferation of K562 and HUT-102 cells. Reduction of beta-catenin expression with beta-catenin antisense down-regulated adhesion of Jurkat cells in response to phytohemagglutinin. Incubation of Jurkat cells with anti-Fas induced caspase-dependent limited proteolysis of beta-catenin N- and C-terminal regions and rapid redistribution of beta-catenin to the detergent-insoluble cytoskeleton, concomitant with a marked decline in nuclear beta-catenin signaling. Fas-mediated apoptosis was potentiated by inhibition of beta-catenin nuclear signaling. The data suggest that beta-catenin can play a significant role in promoting leukemic cell proliferation, adhesion, and survival.

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors prevent high glucose-induced proliferation of mesangial cells via modulation of Rho GTPase/ p21 signaling pathway: Implications for diabetic nephropathy

Inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, also known as statins, are lipid-lowering agents widely used in the prevention of coronary heart disease. Recent experimental and clinical data, however, indicate that the overall benefits of statin therapy may exceed its cholesterol-lowering properties. We postulate that statins may ameliorate the detrimental effects of high glucose (HG)-induced proliferation of mesangial cells (MCs), a feature of early stages of diabetic nephropathy, by preventing Rho isoprenylation. Rat MCs cultured in HG milieu were treated with and without simvastatin, an HMG-CoA reductase inhibitor. Simvastatin inhibited HG-induced MC proliferation as measured by [(3)H]thymidine incorporation. This inhibitory effect was reversed with geranylgeranyl pyrophosphate, an isoprenoid intermediate of the cholesterol biosynthetic pathway. At the cell-cycle level, the HG-induced proliferation of MCs was associated with a decrease in cyclin dependent kinase (CDK) inhibitor p21 protein expression accompanied by an increase in CDK4 and CDK2 kinase activities. Simvastatin reversed the down-regulation of p21 protein expression and decreased CDK4 and CDK2 kinase activities. Exposure of MCs to HG was associated with an increase in membrane-associated Ras and Rho GTPase protein expression. Cotreatment of MCs with simvastatin reversed HG-induced Ras and Rho membrane translocation. Immunofluorescence microscopy revealed that the overexpression of the dominant-negative RhoA led to a significant increase in p21 expression. Our data suggest that simvastatin represses the HG-induced Rho GTPase/p21 signaling in glomerular MCs. Thus, this study provides a molecular basis for the use of statins, independently of their cholesterol-lowering effect, in early stages of diabetic nephropathy.

H(2)O(2)-induced AP-1 activation and its effect on p21(WAF1/CIP1)-mediated G2/M arrest in a p53-deficient human lung cancer cell

Cellular response to oxidative stress is a complex process that is often connected to cell cycle regulation. The present study examines the effect of H(2)O(2) on cell cycle regulation and involvement of reactive oxygen species (ROS) in these H(2)O(2)-induced responses in a p53-deficient human lung carcinoma cell line, H1299. Treatment of the cells with H(2)O(2) caused a G2/M phase arrest. Among the redox-sensitive transcription factors, NF-kappaB and AP-1, we found that only AP-1 was activated by 200 microM H(2)O(2) in human lung cells. Furthermore, electrophoretic mobility shift assays revealed that H(2)O(2) enhanced the DNA binding of AP-1 to a putative AP-1 binding element (TGAGGAA) in the p21(WAF1/CIP1) promoter region (between -2203 and -2197 nucleotides upstream of the transcription initiation site). An increase in c-Jun phosphorylation by ERK was also found to accompany the increased AP-1 activity as detected by Western blot. PD98059, a specific inhibitor of MEK, diminished H(2)O(2)-induced phosphorylation of c-Jun and DNA binding activity of AP-1, decreased expression of p21(WAF1/CIP1), and released the cells from G2/M arrest. Taken together, these results revealed a novel AP-1 binding site in the promoter region of p21(WAF1/CIP1) and a possible cell cycle regulation mechanism mediated by activation of a redox-dependent ERK signaling pathway.

Cooperative repression of cyclin-dependent kinase inhibitor p21 gene expression by hepatitis B virus X protein and hepatitis C virus core protein

Co-infection with hepatitis B virus (HBV) and hepatitis C virus (HCV) is common and is associated with a more severe liver disease and increased frequency in the development of hepatocellular carcinoma (HCC). Here, we demonstrated that HBV X protein (HBx) and HCV core protein additively repress the universal cyclin-dependent kinase inhibitor p21 gene at the transcription level. The transforming growth factor-beta responsive element and Sp1 site of the p21 promoter were responsible for the effect of HCV core and HBx, respectively. Furthermore, cell growth was additively stimulated by them, suggesting that additive repression of the p21 might be important to understand the cooperative development of HCC by HBV and HCV.

Statin use and the risk of breast and prostate cancer

BACKGROUND

Laboratory data suggest that the cholesterol-lowering "statin" drugs may have chemopreventive potential against cancer at various sites, including breast and prostate. However, in one trial of pravastatin there was a significant excess of breast cancer in the treatment group. In the present study, we assessed the relation of statin use to the risk of breast and prostate cancer in our hospital-based Case-Control Surveillance Study of Drugs and Serious Illnesses.

METHODS

Cases were 1,132 women with breast cancer and 1,009 men with prostate cancer; controls were 1,331 women and 1,387 men admitted for conditions unrelated to statin use. We used multivariate unconditional logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for use of statins compared with no use.

RESULTS

The OR for breast cancer among statin users was 1.5 (95% CI = 1.0-2.3), largely accounted for by an OR of 1.8 (95% CI = 0.9-3.6) among cases with carcinoma in situ. Among invasive cases, the OR was 1.2 (95% CI = 0.7-2.0). The odds ratio for prostate cancer overall was 1.2 (95% CI = 0.8-1.7), and it was 1.4 (95% CI = 0.7-2.5) for Stage A.

CONCLUSIONS

The data from the present study do not support a protective effect of statins against breast or prostate cancer. Detection bias is a possible explanation for the higher ORs observed for carcinoma in situ or early-stage cancer as compared with more invasive cancer.

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.

Attenuation of matrix protein secretion by antisense oligodeoxynucleotides to the cyclin kinase inhibitor p21(Waf1/Cip1)

Progressive fibrosis in major organs, including the heart, the kidney and the vascular tree, plays an important role in mediating chronic disease and atherosclerosis. Production of extracellular matrix proteins, in many cases regulated by the growth factor TGF-beta is an essential component of this process. In a parallel manner to TGF-beta, the cyclin kinase inhibitors (CKIs; which are induced by TGF-beta) regulate transit through the cell cycle, and their effect on growth has been shown to be bimodal in the case of vascular smooth muscle (VSM) cells. Using an antisense oligodeoxynucleotide to the CKI p21(Waf1/Cip1), developed in our laboratory and shown to specifically inhibit p21(Waf1/Cip1) protein levels, we asked whether attenuation of the CKI p21(Waf1/Cip1) by transfection of this oligodeoxynucleotide results in the abolition of TGF-beta-mediated growth inhibition and/or diminished matrix protein production and secretion in the presence or absence of TGF-beta. Specific inhibition of p21(Waf1/Cip1) protein with the antisense oligodeoxynucleotide markedly reduces the production and secretion of the matrix proteins fibronectin and laminin, both in the presence and absence of TGF-beta stimulation, in VSM cells as observed by Western blotting of cell lysate and conditioned medium. In addition, TGF-beta-mediated cell growth inhibition, though attenuated by this oligo, is preserved. Due to the relative ease and safety of transfecting antisense oligodeoxynucleotides into VSM, we believe that this work unmasks a potentially powerful technique for inhibition of matrix protein synthesis in VSM and related cell lines, and may lead to new treatment strategies for atherosclerotic as well as other systemic diseases characterized by aberrant matrix protein secretion.