Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

P-glycoprotein (Pgp) is a 170 kDa phosphorylated glycoprotein encoded by human MDR1 gene. It is responsible for the systemic disposition of numerous structurally and pharmacologically unrelated lipophilic and amphipathic drugs, carcinogens, toxins, and other xenobiotics in many organs, such as the intestine, liver, kidney, and brain. Like cytochrome P450s (CYP3A4), Pgp is vulnerable to inhibition, activation, or induction by herbal constituents. This was demonstrated by using an ATPase assay, purified Pgp protein or intact Pgp-expressing cells, and proper probe substrates and inhibitors. Curcumin, ginsenosides, piperine, some catechins from green tea, and silymarin from milk thistle were found to be inhibitors of Pgp, while some catechins from green tea increased Pgp-mediated drug transport by heterotropic allosteric mechanism, and St. John's wort induced the intestinal expression of Pgp in vitro and in vivo. Some components (e.g., bergamottin and quercetin) from grapefruit juice were reported to modulate Pgp activity. Many of these herbal constituents, in particular flavonoids, were reported to modulate Pgp by directly interacting with the vicinal ATP-binding site, the steroid-binding site, or the substrate-binding site. Some herbal constituents (e.g., hyperforin and kava) were shown to activate pregnane X receptor, an orphan nuclear receptor acting as a key regulator of MDR1 and many other genes. The inhibition of Pgp by herbal constituents may provide a novel approach for reversing multidrug resistance in tumor cells, whereas the stimulation of Pgp expression or activity has implication for chemoprotective enhancement by herbal medicines. Certain natural flavonols (e.g., kaempferol, quercetin, and galangin) are potent stimulators of the Pgp-mediated efflux of 7,12-dimethylbenz(a)-anthracene (a carcinogen). The modulation of Pgp activity and expression by these herb constituents may result in altered absorption and bioavailability of drugs that are Pgp substrates. This is exemplified by increased oral bioavailability of phenytoin and rifampin by piperine and decreased bioavailability of indinavir, tacrolimus, cyclosporine, digoxin, and fexofenadine by coadministered St. John's wort. However, many of these drugs are also substrates of CYP3A4. Thus, the modulation of intestinal Pgp and CYP3A4 represents an important mechanism for many clinically important herb-drug interactions. Further studies are needed to explore the relative role of Pgp and CYP3A4 modulation by herbs and the mechanism for the interplay of these two important proteins in herb-drug interactions.
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PMID:Herbal modulation of P-glycoprotein. 1507 39

Curcumin (diferuloylmethane) is being considered as a potential chemopreventive agent in humans. In vitro it inhibits transcription by NF-kappaB, and the activity of lipoxygenase or cyclooxygenase enzymes, which facilitate tumor progression. In vivo it is protective in rodent models of chemical carcinogenesis. Curcumin contains an alpha,beta-unsaturated ketone, a reactive chemical substituent that is responsible for its repression of NF-kappaB. In compounds other than curcumin this same electrophilic moiety is associated with inactivation of the tumor suppressor, p53. Here we report that curcumin behaves analogously to these compounds. It disrupts the conformation of the p53 protein required for its serine phosphorylation, its binding to DNA, its transactivation of p53-responsive genes and p53-mediated cell cycle arrest.
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PMID:Curcumin impairs tumor suppressor p53 function in colon cancer cells. 1509 Apr 65

Curcumin, the active ingredient from the spice turmeric (Curcuma longa Linn), is known to be an anti-oxidant and an anti-inflammatory agent. It has been demonstrated recently to possess anti-angiogenic effects and pro-apoptotic activities against Ehrlich ascites tumor cells. In the current study, curcumin was found to be cytotoxic in vitro for B16-R melanoma cells resistant to doxorubicin either cultivated as monolayers or grown in three-dimensional (3-D) cultures (spheroids). We have demonstrated that the cytotoxic effect observed in the 2 culture types can be related to the induction of programmed cell death. In our in vivo studies, we examined the effectiveness of a prophylactic immune preparation of soluble proteins from B16-R cells, or a treatment with curcumin as soon as tumoral appearance, alone or in combination, on the murine melanoma B16-R. The combination treatment resulted in substantial inhibition of growth of B16-R melanoma, whereas each treatment by itself showed little effect. Moreover, animals receiving the combination therapy exhibited an enhancement of their humoral anti-soluble B16-R protein immune response and a significant increase in their median survival time (> 82.8% vs. 48.6% and 45.7% respectively for the immunized group and the curcumin-treated group). Our study shows that curcumin may provide a valuable tool for the development of a therapeutic combination against the melanoma.
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PMID:In vitro and in vivo anti-tumoral effect of curcumin against melanoma cells. 1522 65

Epidemiologic studies suggest that diet rich in plant-derived foods plays an important role in the prevention of prostate cancer. Curcumin, the yellow pigment in the spice turmeric, has been shown to exhibit chemopreventive and growth inhibitory activities against multiple tumor cell lines. We have shown previously that curcumin and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)/Apo2L interact to induce cytotoxicity in the LNCaP prostate cancer cell line. In this study, we investigated the mechanism by which curcumin augments TRAIL-induced cytotoxicity in LNCaP cells. Subtoxic concentrations of the curcumin-TRAIL combination induced strong apoptotic response in LNCaP cells as demonstrated by the binding of Annexin V-FITC and cleavage of procaspase-3. Furthermore, LNCaP cells express constitutively active nuclear factor-kappaB (NF-kappaB), which is inhibited by curcumin. Because NF-kappaB has been shown to mediate resistance to TRAIL-induced apoptosis in tumor cells, we investigated whether there is a relationship between NF-kappaB activation and resistance to TRAIL in LNCaP prostate cancer cells. Pretreatment with curcumin inhibited the activation of NF-kappaB and sensitized LNCaP cells to TRAIL. A similar increase in the sensitivity of LNCaP cells to TRAIL-induced apoptosis was observed following inhibition of NF-kappaB by dominant negative mutant IkappaBalpha, an inhibitor of NF-kappaB. Finally, curcumin was found to inhibit NF-kappaB by blocking phosphorylation of IkappaBalpha. We conclude that NF-kappaB mediates resistance of LNCaP cells to TRAIL and that curcumin enhances the sensitivity of these tumor cells to TRAIL by inhibiting NF-kappaB activation by blocking phosphorylation of IkappaBalpha and its degradation.
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PMID:Curcumin sensitizes prostate cancer cells to tumor necrosis factor-related apoptosis-inducing ligand/Apo2L by inhibiting nuclear factor-kappaB through suppression of IkappaBalpha phosphorylation. 1525 41

Curcumin (diferuloylmethane) is a major naturally-occurring polyphenol of Curcuma species, which is commonly used as a yellow coloring and flavoring agent in foods. Curcumin has shown anti-carcinogenic activity in animal models. Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase and inducible nitric oxide synthase; and an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C (PKC), EGF(Epidermal growth factor)-receptor tyrosine kinase and IkappaB kinase. Subsequently, curcumin inhibits the activation of NF(nucleor factor)kappaB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs and iNOS. It is proposed that curcumin may suppress tumor promotion through blocking signal transduction pathways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, while the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins play a pivotal role in the regulation of several basic cellular processes including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of ubiquitin-proteasome pathway. Curcumin was first biotransformed to dihydrocurcumin and tetrahydrocurcumin and that these compounds subsequently were converted to monoglucuronide conjugates. These results suggest that curcumin-glucuronide, dihydrocurcumin-glucuronide, tetrahydrocurcumin-glucuronide and tetrahydrocurcumin are the major metabolites of curcumin in mice, rats and humans.
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PMID:Suppression of protein kinase C and nuclear oncogene expression as possible action mechanisms of cancer chemoprevention by Curcumin. 1535 94

In a previous study, we observed that some synthetic curcumin analogs inhibited complex formations between Fos-Jun heterodimer and activator protein-1 (AP-1) DNA. These curcumin analogs have been observed to repress the AP-1 transcription in AP-1-transfected cells and they also inhibited the increased expression of Jun/AP-1 protein by 12-O-tetradecanoylphorbol-13-acetate (TPA) in the same cells. After the AP-1 inhibition by curcumin analogs in TPA-treated HT-1080 human fibrosarcoma cells, a decrease in mRNA expression of c-jun and MMP3 (stromelysin-1) has been observed. We also observed that curcumin analogs down-regulated the expression of MMP-9 (gelatinase-B), correlating with cellular invasion and migration in conditions such as tumor invasion and metastasis, through the electrophoretic mobility shift assay and gelatin zymography methods. Curcumin analogs showed an inhibitory effect on angiogenesis by various test methods including chicken chorioallantoic membrane assay, wound migration assay, invasion assay, and tube formation assay. Through the reverse transcriptase-polymerase chain reaction experiment, we confirmed that curcumin analogs down-regulated the expression of angiogenesis-associated genes, VEGF and MMP-9.
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PMID:Synthetic curcumin analogs inhibit activator protein-1 transcription and tumor-induced angiogenesis. 1535 81

Curcumin, a well-known dietary pigment derived from Curcuma longa, inhibited growth of several types of malignant cells both in vivo and in vitro. However, its mechanism of action still remains unclear. In this study, we have focused primarily on the cytotoxic effects of curcumin on three human tumor cell lines and rat primary hepatocytes. Curcumin induced apoptosis in MCF-7, MDAMB, and HepG2 cells in a dose-dependent and time-dependent manner. Apoptosis was mediated through the generation of reactive oxygen species. Attempts were made to establish the role played by endogenous glutathione on the apoptotic activity of curcumin. Depletion of glutathione by buthionine sulfoximine resulted in the increased generation of reactive oxygen species, thereby further sensitizing the cells to curcumin. Interestingly, curcumin had no effect on normal rat hepatocytes, which showed no superoxide generation and therefore no cell death. These observations suggest that curcumin, a molecule with varied actions, could be developed into an effective chemopreventive and chemotherapeutic agent.
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PMID:Effect of curcumin on normal and tumor cells: role of glutathione and bcl-2. 1536 4

Colorectal cancer is a leading cause of cancer-related morbidity and mortality in the United States. Curcumin, the yellow pigment in turmeric, possesses inhibitory effects on growth of a variety of tumor cells by reducing cell proliferation and inducing apoptosis. Effects of the peroxisome proliferator-activated receptor-gamma (PPARgamma) on stimulating cell differentiation and on inducing cell cycle arrest have attracted attention from the perspective of treatment and prevention of cancer. The aim of this study was to elucidate the mechanisms by which curcumin inhibits colon cancer cell growth. In the present report, we observed that curcumin, in a dose-dependent manner, inhibited the growth of Moser cells, a human colon cancer-derived cell line, and stimulated the trans-activating activity of PPARgamma. Further studies demonstrated that activation of PPARgamma was required for curcumin to inhibit Moser cell growth. Activation of PPARgamma mediated curcumin suppression of the expression of cyclin D1, a critical protein in the cell cycle, in Moser cells. In addition, curcumin blocked EGF signaling by inhibiting EGF receptor (EGFR) tyrosine phosphorylation and suppressing the gene expression of EGFR mediated by activation of PPARgamma. In addition to curcumin reduction of the level of phosphorylated PPARgamma, inhibition of cyclin D1 expression played a major and significant role in curcumin stimulation of PPARgamma activity in Moser cells. Taken together, our results demonstrated for the first time that curcumin activation of PPARgamma inhibited Moser cell growth and mediated the suppression of the gene expression of cyclin D1 and EGFR. These results provided a novel insight into the roles and mechanisms of curcumin in inhibition of colon cancer cell growth and potential therapeutic strategies for treatment of colon cancer.
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PMID:Activation of PPAR{gamma} by curcumin inhibits Moser cell growth and mediates suppression of gene expression of cyclin D1 and EGFR. 1548 48

Xanthorrhizol is a sesquiterpenoid compound isolated from the rhizome of Curcuma xanthorrhiza. In this study, the anti-metastatic activity of xanthorrhizol was evaluated by using an in vivo mouse lung metastasis model and a tumor mass formation assay. Interestingly, xanthorrhizol dramatically inhibited the formation of tumor nodules in the lung tissue and the intra-abdominal tumor mass formation. Next, to examine the mechanism of the anti-metastatic action of xanthorrhizol in the mouse lung metastasis, expression patterns of the several intracellular signaling molecules were evaluated using the lung tissues with tumor nodules. Higher expression levels of cyclooxygenase-2 (COX-2), matrix metalloproteinase-9 (MMP-9), and phosphorylated extracellular signal-regulated kinase (ERK) were observed in the metastatic group compared with control, but these were attenuated by the treatment of xanthorrhizol. In conclusion, xanthorrhizol exerts anti-metastatic activity in vivo and this effect could be highly linked to the metastasis-related multiplex signal pathway including ERK, COX-2, and MMP-9.
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PMID:Xanthorrhizol, a natural sesquiterpenoid from Curcuma xanthorrhiza, has an anti-metastatic potential in experimental mouse lung metastasis model. 1556 73

Cancer is a general term used to describe many disease states, each of which are characterized by abnormal cell proliferation. The causes which bring about this abnormal cellular behavior are specific to each type of cancer. The success of tumor-targeted therapy is limited by this diversity. One common denominator for all types of cancer is the requirement of a suitable blood supply. Therefore, tumor vasculature has emerged as a potential target for therapeutic intervention. New blood vessel growth from preexisting vasculature stimulated by biochemical signals is termed angiogenesis. Tumor masses require a constant supply of oxygen and nutrients, and a means of efficient waste removal to ensure sustained development. Diffusion from nearby capillaries can supply adequate nutrition for tumors less than 2 mm in size, but for continued growth the tumors must develop their own blood supply. Alteration of the delicate balance of angiogenic stimulating factors and angiogenic inhibitors results in the phenotypic change from quiescence to active endothelial proliferation. To date, this angiogenic switch is not completely understood. The goal of antiangiogenic therapy is to interfere with these mechanisms and prevent tumor cells from developing a viable blood supply. Fumagillin is a naturally occurring antifungal agent. Curcumin is a natural product isolated from the spice turmeric. Both compounds have been shown to have antiangiogenic properties in vitro and in vivo. This paper describes efforts to design and prepare fumagillin and curcumin analogs and evaluate their corresponding antiangiogenic activities.
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PMID:Antiangiogenic agents: studies on fumagillin and curcumin analogs. 1572 31


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