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ABSTRACT: Peroxisome proliferator-activated receptor delta (PPAR-delta), one of three PPAR subtypes, is a lipid-sensing nuclear receptor that has been implicated in multiple processes, including inflammation and cancer. To directly establish the role of PPAR-delta in colon cancer development and progression, we selected high-affinity RNA aptamers and expressed them in several colon cancer cell lines. Nuclear-expressed aptamers efficiently inhibited PPAR-delta-dependent transcription from a synthetic peroxisome proliferator response element-driven luciferase reporter. PPAR-delta-specific aptamers suppressed transcription from natural promoters of vascular endothelial cell growth factor-A and cyclooxygenase-2. Moreover, vascular endothelial cell growth factor-A and cyclooxygenase-2 mRNA levels were significantly reduced by the PPAR-delta-specific aptamers in colon cancer cells. Most significantly, HCT116 colon cancer cells with high-level expression of PPAR-delta-specific aptamers exhibited a striking loss of tumorigenic potential. Further study on these RNA aptamers could provide an opportunity to modulate PPAR-delta-mediated colon cancer development and progression. Taken together, our results establish an important role for PPAR-delta in transcription of tumor-promoting genes, which can be specifically modulated by high-affinity RNA intramers in colon cancer cells. The RNA intramers may be further developed as specific inhibitors for cancer therapeutic strategies.
Molecular Cancer Therapeutics 10/2009; 8(9):2664-73. · 5.23 Impact Factor
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ABSTRACT: Nuclear beta-catenin forms a transcription complex with TCF-4, which is implicated in colon cancer development and progression. Recently, we and others have shown that beta-catenin could be a regulator of RNA splicing and it also stabilizes the cyclooxygenase-2 (COX-2) mRNA. Here, we further explored the role of beta-catenin in the RNA metabolism in colon cancer cells. To specifically modulate the subcellular functions of beta-catenin, we expressed the RNA aptamer in the form of RNA intramers with unique cellular localizations. The nucleus-expressed RNA intramer proved to be effective in reducing the protein-protein interaction between beta-catenin and TCF-4, thus shown to be a specific regulator of beta-catenin-activated transcription. It could also regulate the alternative splicing of E1A minigene in diverse colon cancer cell lines. In addition, we tested whether beta-catenin could stabilize any other mRNAs and found that cyclin D1 mRNA was also bound and stabilized by beta-catenin. Significantly, the cytoplasm-expressed RNA intramer reverted the beta-catenin-induced COX-2 and cyclin D1 mRNA stabilization. We show here that beta-catenin regulated multiple steps of RNA metabolism in colon cancer cells and might be the protein factor coordinating RNA metabolism. We suggest that the RNA intramers could provide useful ways for inhibiting beta-catenin-mediated transcription and RNA metabolism, which might further enhance the antitumorigenic effects of these molecules in colon cancer cells.
Cancer Research 11/2007; 67(19):9315-21. · 7.86 Impact Factor
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ABSTRACT: Several epidemiological studies have suggested that exposure to arsenic is strongly correlated with the development of cardiovascular diseases such as hypertension. To determine whether arsenic affects vasomotor tone in blood vessels, we investigated the effect of arsenic on vasorelaxation using isolated rat aortic rings in an organ-bath system. Treatment with arsenite inhibited acetylcholine-induced relaxation of the aortic rings in a concentration-dependent manner, whereas several other arsenic species did not have any effect. Consistent with these findings, the levels of guanosine 3',5'-cyclic monophosphate (cGMP) in the aortic rings were significantly reduced by arsenite treatment. In cultured human aortic endothelial cells, treatment with arsenite resulted in a concentration-dependent inhibition of endothelial nitric oxide synthase (eNOS). In addition, higher concentrations of arsenite decreased the relaxation induced by sodium nitroprusside (an NO donor) and 8-Br-cGMP (a cGMP analog) in aortic rings without endothelium. These in vitro results indicate that arsenite is capable of suppressing relaxation in blood vessels by inhibiting eNOS activity in endothelial cells and by impairing the relaxation machinery in smooth muscle cells. In vivo studies revealed that the reduction of blood pressure by acetylcholine infusion was significantly suppressed after arsenite was administered intravenously to rats. These data suggest that an impairment of vasomotor tone due to arsenite exposure may be a contributing factor in the development of cardiovascular disease.
Environmental Health Perspectives 05/2003; 111(4):513-7. · 7.04 Impact Factor
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ABSTRACT: CKD-602 (7-[2-(N-isopropylamino)ethyl]-(20S)-camptothecin) is a recently-developed synthetic camptothecin analogue and currently under clinical development by Chong Kun Dang Pharm (Seoul, Korea). CKD-602 showed potent topoisomerase inhibitory activity in vitro and broad antitumor activity against various human tumor cells in vitro and in vivo in animal models. This study describes the pharmacodynamics of the immediate and delayed cytotoxicity induced by CKD-602 in a human colorectal adenocarcinoma cell line, HT-29, and its intracellular drug accumulation by HPLC. The present study was designed to address whether the higher activity of CKD-602 with prolonged exposure is due to delayed exhibition of cytotoxicity and/or an accumulation of antiproliferative effect on continuous drug exposure. The drug uptake study was performed to determine whether the delayed cytotoxicity is due to a slow drug accumulation in cells. CKD-602 produced a cytotoxicity that was exhibited immediately after treatment (immediate effect) and after treatment had been terminated (delayed effect). Both the immediate and delayed effects of CKD-602 showed a time dependent decrease in IC50 values. Drug uptake was biphasic and the second equilibrium level was obtained as early as at 24 hr, indicating that the cumulative and delayed antitumor effects of CKD-602 were not due to slow drug uptake. On the other hand, CKD-602 treatment was sufficient to induce delayed cytotoxicity after 4 hr, however, longer treatment (>24 hr) enhanced its cytotoxicity due to the intracellular accumulation of the drug, which requires 24 hr to reach maximum equilibrium concentration. In addition, Cn x T=h analysis (n=0.481) indicated that increased exposure times may contribute more to the overall antitumor activity of CKD-602 than drug concentration. Additional studies to determine the details of the intracellular uptake kinetics (e.g., concentration dependency and retention studies) are needed in order to identify the optimal treatment schedules for the successful clinical development of CKD-602.
Archives of Pharmacal Research 11/2002; 25(5):718-23. · 1.59 Impact Factor
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ABSTRACT: Methamphetamine (METH) causes neurotoxic damages to the dopaminergic system in mammals, but whether it exerts toxicity to dopamine cells in culture has not been fully explored. In order to develop an in vitro model of METH-induced dopamine neurotoxicity toward more systemical examination of the mechanism, we investigated METH toxicity in a clonal dopamine producing cell line (CATH.a). We show in the present study that METH produces a time- and dose-dependent increase in cell death via a process similar to apoptosis. The METH toxicity seems to be produced by oxidative stress, as it was attenuated by the antioxidant glutathione, and to involve dopamine because dopamine release and synthesis inhibitors attenuated the toxicity. This catecholaminergic cell line derived from the central nervous system may become a useful in vitro model to elucidate the mechanism underlying the METH-induced dopaminergic neuronal damage.
Molecules and Cells 05/2002; 13(2):221-7. · 2.18 Impact Factor
