geranylgeranyl-pyrophosphate and Breast-Neoplasms

The YAP and TAZ mediators of the Hippo pathway (hereafter called YAP/TAZ) promote tissue proliferation and organ growth. However, how their biological properties intersect with cellular metabolism remains unexplained. Here, we show that YAP/TAZ activity is controlled by the SREBP/mevalonate pathway. Inhibition of the rate-limiting enzyme of this pathway (HMG-CoA reductase) by statins opposes YAP/TAZ nuclear localization and transcriptional responses. Mechanistically, the geranylgeranyl pyrophosphate produced by the mevalonate cascade is required for activation of Rho GTPases that, in turn, activate YAP/TAZ by inhibiting their phosphorylation and promoting their nuclear accumulation. The mevalonate-YAP/TAZ axis is required for proliferation and self-renewal of breast cancer cells. In Drosophila melanogaster, inhibition of mevalonate biosynthesis and geranylgeranylation blunts the eye overgrowth induced by Yorkie, the YAP/TAZ orthologue. In tumour cells, YAP/TAZ activation is promoted by increased levels of mevalonic acid produced by SREBP transcriptional activity, which is induced by its oncogenic cofactor mutant p53. These findings reveal an additional layer of YAP/TAZ regulation by metabolic cues.

Topics: Active Transport, Cell Nucleus; Acyltransferases; Adaptor Proteins, Signal Transducing; Animals; Breast Neoplasms; Cell Proliferation; Drosophila melanogaster; Drosophila Proteins; Female; HCT116 Cells; HEK293 Cells; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hydroxymethylglutaryl-CoA Reductases, NAD-Dependent; Intracellular Signaling Peptides and Proteins; Mevalonic Acid; Mice; Nuclear Proteins; Phosphoproteins; Phosphorylation; Polyisoprenyl Phosphates; Protein Serine-Threonine Kinases; Pyridines; rho GTP-Binding Proteins; RNA Interference; RNA, Small Interfering; Signal Transduction; Sterol Regulatory Element Binding Proteins; Trans-Activators; Transcription Factors; Transcription, Genetic; Tumor Suppressor Proteins; YAP-Signaling Proteins

Simvastatin (SVA) was shown to up-regulate expression of death receptor-5 (DR5), CCAAT/enhancer binding protein homologous protein (CHOP) and phosphorylated c-Jun N-terminal kinase (pJNK) in human breast cancer cell lines. siRNA knockdown of DR5, CHOP or JNK significantly blocked SVA-induced apoptosis, demonstrating the importance of JNK/CHOP/DR5 signaling pathway in SVA-induced apoptosis. Exogenous addition of either mevalonate or geranylgeranyl pyrophosphate (GGPP) inhibited SVA activation of JNK/CHOP/DR5 pro-apoptotic pathway, indicating that activation of JNK/CHOP/DR5 pro-apoptotic pathway is dependent on SVA inhibition of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase and its intermediate GGPP. Data provide novel insight into better understanding the anticancer mechanisms of SVA.

Topics: Antineoplastic Agents; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Female; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; JNK Mitogen-Activated Protein Kinases; MAP Kinase Signaling System; Mevalonic Acid; Polyisoprenyl Phosphates; Receptors, TNF-Related Apoptosis-Inducing Ligand; RNA, Small Interfering; Sesquiterpenes; Signal Transduction; Simvastatin; Transcription Factor CHOP

Statins are known to inhibit growth of a number of cancer cells, but their mechanism of action is not well established. In this study, human prostate adenocarcinoma PC-3 and breast adenocarcinoma MCF-7 cell lines were used as models to investigate the mechanism of action of atorvastatin, one of the statins. Atorvastatin was found to induce apoptosis in PC-3 cells at a concentration of 1 μM, and in MCF-7 cells at 50 μM. Initial survey of possible pathway using various pathway-specific luciferase reporter assays showed that atorvastatin-activated antioxidant response element (ARE), suggesting oxidative stress pathway may play a role in atorvastatin-induced apoptosis in both cell lines. Among the antioxidant response genes, heme oxygenase-1 (HO-1) was significantly up-regulated by atorvastatin. Pre-incubation of the cells with geranylgeranyl pyrophosphate blocked atorvastatin-induced apoptosis, but not up-regulation of HO-1, suggesting that atorvastatin-induced apoptosis is dependent on GTPase activity and up-regulation of HO-1 gene is not. Six ARE-like elements (designated StRE1 [stress response element] through StRE6) are present in the HO-1 promoter. Atorvastatin was able to activate all of the elements. Because these StRE sites are present in clusters in HO-1 promoter, up-regulation of HO-1 by atorvastatin may involve multiple StRE sites. The role of HO-1 in atorvastatin-induced apoptosis in PC-3 and MCF-7 remains to be studied.

Topics: Apoptosis; Atorvastatin; Breast Neoplasms; Cell Line, Tumor; Female; Heme Oxygenase-1; Heptanoic Acids; Humans; Male; Oxidative Stress; Polyisoprenyl Phosphates; Promoter Regions, Genetic; Prostatic Neoplasms; Pyrroles; Signal Transduction; Transcriptional Activation; Up-Regulation

The objective of this study was to determine whether geranylgeranyl diphosphate synthase inhibition, and therefore geranylgeranyl diphosphate depletion, interferes with breast cancer cell migration. Digeranyl bisphosphonate is a specific geranylgeranyl diphosphate synthase inhibitor. We demonstrate that digeranyl bisphosphonate depleted geranylgeranyl diphosphate and inhibited protein geranylgeranylation in MDA-MB-231 cells. Similar to GGTI-286, a GGTase I inhibitor, digeranyl bisphosphate significantly inhibited migration of MDA-MB-231 cells as measured by transwell assay. Similarly, digeranyl bisphosphonate reduced motility of MDA-MB-231 cells in a time-dependent manner as measured by large scale digital cell analysis system microscopy. Digeranyl bisphosphonate was mildly toxic and did not induce apoptosis. Treatment of MDA-MB-231 cells with digeranyl bisphosphonate decreased membrane while it increased cytosolic RhoA localization. In addition, digeranyl bisphosphonate increased RhoA GTP binding in MDA-MB-231 cells. The specificity of geranylgeranyl diphosphonate synthase inhibition by digeranyl bisphosphonate was confirmed by exogenous addition of geranylgeranyl diphosphate. Geranylgeranyl diphosphate addition prevented the effects of digeranyl bisphosphonate on migration, RhoA localization, and GTP binding to RhoA in MDA-MB-231 cells. These studies suggest that geranylgeranyl diphosphate synthase inhibitors are a novel approach to interfere with cancer cell migration.

Topics: Biosynthetic Pathways; Breast Neoplasms; Cell Line, Tumor; Cell Movement; Diphosphonates; Female; Guanosine Triphosphate; Humans; Polyisoprenyl Phosphates; Protein Binding; Protein Transport; rhoA GTP-Binding Protein; Terpenes

Nitrogen-containing bisphosphonates are the elected drugs for the treatment of diseases in which excessive bone resorption occurs, for example, osteoporosis and cancer-induced bone diseases. The only known target of nitrogen-containing bisphosphonates is farnesyl pyrophosphate synthase, which ensures prenylation of prosurvival proteins, such as Ras. However, it is likely that the action of nitrogen-containing bisphosphonates involves additional unknown mechanisms. To identify novel targets of nitrogen-containing bisphosphonates, we used a genome-wide high-throughput screening in which 5,936 Saccharomyces cerevisiae heterozygote barcoded mutants were grown competitively in the presence of sub-lethal doses of three nitrogen-containing bisphosphonates (risedronate, alendronate and ibandronate). Strains carrying deletions in genes encoding potential drug targets show a variation of the intensity of their corresponding barcodes on the hybridization array over the time.. With this approach, we identified novel targets of nitrogen-containing bisphosphonates, such as tubulin cofactor B and ASK/DBF4 (Activator of S-phase kinase). The up-regulation of tubulin cofactor B may explain some previously unknown effects of nitrogen-containing bisphosphonates on microtubule dynamics and organization. As nitrogen-containing bisphosphonates induce extensive DNA damage, we also document the role of DBF4 as a key player in nitrogen-containing bisphosphonate-induced cytotoxicity, thus explaining the effects on the cell-cycle.. The dataset obtained from the yeast screen was validated in a mammalian system, allowing the discovery of new biological processes involved in the cellular response to nitrogen-containing bisphosphonates and opening up opportunities for development of new anticancer drugs.

Topics: Alendronate; Blotting, Western; Breast Neoplasms; Cell Cycle; Cell Cycle Proteins; Cell Division; Cell Line, Tumor; Cell Movement; Diphosphonates; DNA Breaks, Double-Stranded; DNA Damage; Etidronic Acid; Gene Deletion; Humans; Ibandronic Acid; Microscopy, Confocal; Microscopy, Electron; Microtubules; Mutation; Polyisoprenyl Phosphates; Risedronic Acid; RNA Interference; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins

Bisphosphonates are widely used inhibitors of bone resorption. They also inhibit the growth of various cancer cells in vitro, but the clinical significance of this effect is unclear. The cancer growth inhibitory effects of nitrogen-containing bisphosphonates, (i.e. zoledronate) have been attributed to their ability to inhibit the mevalonate pathway. We have shown that bisphosphonates also induce p38 activation, which signals resistance against the drug-induced growth inhibition through an unknown mechanism. We show here that zoledronate induces a G1/S cell cycle arrest in human MDA-MB-231 breast cancer cells. Furthermore, p38 inhibitor augments bisphosphonate-induced growth inhibition by inducing an additional G2-phase cell cycle arrest. We also show that the nitrogen-containing bisphosphonate-induced effects on p38 phosphorylation occur before accumulation of unprenylated Rap1A or Rac1 activation. Geranylgeranyl pyrophosphate, an end-product of the mevalonate pathway, reversed the accumulation of unprenylated Rap1A but not phosphorylation of p38. Geranylgeranyl pyrophosphate also reversed n-BP induced growth inhibition, but the completeness of this reversal was nitrogen-containing bisphosphonate concentration dependent. Also mevastatin induced the accumulation of unprenylated Rap1A, but it did not induce p38 phosphorylation. In conclusion, our results suggest that in addition to the previously reported effects on apoptosis, nitrogen-containing bisphosphonates also inhibit the growth of MDA-MB-231 breast cancer cells by inducing G1/S cell cycle arrest. The bisphosphonate-induced p38 activation signals for resistance against these drugs, by promoting progression through the G2/M-checkpoint. Of these pathways only growth inhibition is mediated via inhibition of the mevalonate pathway in MDA-MB-231 cells. Combining p38 inhibitors with bisphosphonates may result in increased anti-cancer efficacy.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Diphosphonates; DNA; Humans; Lovastatin; Mevalonic Acid; Nitrogen; p38 Mitogen-Activated Protein Kinases; Polyisoprenyl Phosphates; rap1 GTP-Binding Proteins

Statins are widely used cholesterol-lowering drugs that selectively inhibit the enzyme 3-hydroxy-3-methylglutaryl CoA reductase, leading to decreased cholesterol biosynthesis. Emerging data indicate that statins stimulate apoptotic cell death in several types of proliferating tumor cells, including breast cancer cells, which is independent of its cholesterol-lowering property. The objective here was to elucidate the molecular mechanism(s) by which statins induce breast cancer cell death. Fluvastatin and simvastatin (5-10 mumol/L) treatment enhanced the caspase-3-like activity and DNA fragmentation in MCF-7 cells, and significantly inhibited the proliferation of MCF-7 cells but not MCF-10 cells (noncancerous epithelial cells). Statin-induced cytotoxic effects were reversed by mevalonate, an immediate metabolic product of the acetyl CoA/3-hydroxy-3-methylglutaryl CoA reductase reaction. Both simvastatin and fluvastatin enhanced nitric oxide ((.)NO) levels which were inhibited by mevalonate. Statin-induced (.)NO and tumor cell cytotoxicity were inhibited by 1400W, a more specific inhibitor of inducible nitric oxide synthase (iNOS or NOS II). Both fluvastatin and simvastatin increased iNOS mRNA and protein expression. Stimulation of iNOS by statins via inhibition of geranylgeranylation by GGTI-298, but not via inhibition of farnesylation by FTI-277, enhanced the proapoptotic effects of statins in MCF-7 cells. Statin-mediated antiproliferative and proapoptotic effects were exacerbated by sepiapterin, a precursor of tetrahydrobiopterin, an essential cofactor of (.)NO biosynthesis by NOS. We conclude that iNOS-mediated (.)NO is responsible in part for the proapoptotic, tumoricidal, and antiproliferative effects of statins in MCF-7 cells.

Topics: Anticholesteremic Agents; Antioxidants; Apoptosis; Arginase; Blotting, Western; Breast Neoplasms; Caspase 3; Cell Adhesion; Cell Cycle; Cells, Cultured; Colony-Forming Units Assay; Fatty Acids, Monounsaturated; Fluvastatin; Humans; In Situ Nick-End Labeling; Indoles; Mevalonic Acid; Nitric Oxide; Nitric Oxide Synthase Type II; Polyisoprenyl Phosphates; Protein Prenylation; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Simvastatin