[Show abstract][Hide abstract] ABSTRACT: A series of novel 2,4,5-substituted pyrimidine derivatives were synthesized and evaluated for inhibition against the human hepatocellular carcinoma BEL-7402 cancer cell line. Several compounds showed potent inhibition with an IC(50) value less than 0.10 microM. Structure-activity relationships for this class of compounds at the 2- and 5-position of the pyrimidine scaffold have been elucidated. The most active compound 7gc showed good inhibition of several different human cancer cell lines with IC(50) values from 0.024 to 0.55 microM.
[Show abstract][Hide abstract] ABSTRACT: Combretastatin A4 (CA4) is a novel vascular disrupting agent that has promising clinical efficacy because of its ability to inhibit microtubule assembly and subsequently disrupt tumor blood flow. In this study, we demonstrate that mitogen-activated protein kinases (MAPKs) are critically involved in the cytotoxicity of CA4. CA4 stimulates both extracellular signal-regulated kinases (ERK1/2) and p38 MAPK in the BEL-7402 hepatocellular carcinoma cell line in a time- and dose-dependent manner. This stimulation is a result of CA4-induced microtubule disassembly, which is a reversible process. Reversibility of microtubule disassembly is evidenced by the ability of disassembled microtubules to reassemble just a few hours after CA4 treatment. p38 MAPK, but not ERK1/2, contributes to this microtubule reassembly following CA4 exposure, and only inhibition of p38 MAPK, but not ERK1/2, synergistically enhances CA4-induced G(2)/M cell cycle arrest. Consistent with this, p38 MAPK inhibitors such as SB203580 and SB202190 also synergistically enhance the cytotoxicity of CA4 in cells where p38 MAPK is activated by CA4. This enhancement appears to be specific for CA4 because the cytotoxicity of other microtubule-targeted agents such as paclitaxel, vinorelbine and colchicine was not affected by p38 MAPK inhibitors. These data indicate that p38 MAPK is a potential anticancer target and that the combination of CA4 with p38 MAPK inhibitors may be a novel and promising strategy for cancer therapy.
International Journal of Cancer 05/2008; 122(8):1730-7. · 6.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: P-glycoprotein (P-gp) pumps multiple types of drugs out of the cell, using energy generated from ATP, and confers multidrug resistance (MDR) on cancer cells. ZD6474 is an orally active, selective inhibitor of the vascular endothelial growth factor receptor, epidermal growth factor receptor, and rearranged during transfection tyrosine kinases. This study was designed to examine whether ZD6474 reverses P-gp-mediated MDR in cancer cells. Here, we show that clinically achievable levels of ZD6474 reverse P-gp-mediated MDR of the P-gp-overexpressing cell lines derived from breast cancer, MCF-7/adriamycin (ADR), and human oral epidermoid carcinoma, KBV200 to ADR, docetaxel, and vinorelbine. This ability to reverse the P-gp-mediated resistance is comparable to that of another frequently used reversal agent known as verapamil. ZD6474 itself moderately inhibits the proliferation of both MCF-7 and MCF-7/ADR cells with almost equal activity, but its inhibitory effect is not altered by co-incubation with verapamil, suggesting that ZD6474 may not be a substrate of P-gp. In addition, ZD6474 increases the intracellular accumulation of the P-gp substrate, rhodamine-123, and ADR, by enhancing the uptake and/or decreasing the efflux of these compounds in resistant cells. Further studies show that ZD6474 stimulates ATPase activity in a dose-dependent manner, which is required for the proper function of P-gp. In contrast, ZD6474 does not inhibit the expression level of P-gp. Our results suggest that ZD6474 is capable of reversing MDR in cancer cells by directly inhibiting the function of P-gp, a finding that may have clinical implications for ZD6474.
British Journal of Cancer 11/2007; 97(7):934-40. · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A series of 3-demethoxycarbonyl-3-carbamate methyl anhydrovinblastine derivatives (compounds 8b-32b) were designed, synthesized, and evaluated for their inhibition activities against human non-small cell lung cancer cell line (A549) and a human cervix epithelial adenocarcinoma cell line (HeLa). The structure-activity relationships of this new series are described in this paper. Cytotoxicity data revealed that the size of substituents and substitution position had important influence on cytotoxic activity. On two cell lines, compounds (8b and 30b) had more potent cytotoxic activity than the lead compound (1e, AVLB). The preliminary antitumor studies of 8b in vivo showed that it might be promising for the development of new antitumor agents.
[Show abstract][Hide abstract] ABSTRACT: Phytochemical investigation of the whole plants of Wollastonia biflora led to the isolation and identification of three new germacrane-type sesquiterpenes (1-3), two new pimarane-type diterpenes (4, 5), and a new naphthalene glycoside (6), along with 11 known compounds. Their structures were characterized on the basis of spectroscopic analyses and chemical methods. Compounds 1, 2, and 3 showed significant cytotoxic activity against the growth of hepatocellular carcinoma BEL-7402 cells in vitro.
Journal of Natural Products 05/2007; 70(4):567-70. · 3.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
[Show abstract][Hide abstract] ABSTRACT: The marine natural product scalaradial (SLD) is a potent inhibitor of secretory phospholipase A(2) (sPLA(2)). Our previous work has demonstrated that SLD inhibits epidermal growth factor receptor-mediated Akt phosphorylation, and this effect is independent of sPLA(2). Here we report the role of SLD in extracellular signal-regulated kinase (ERK)1/2 activation. SLD inhibited ERK1/2 phosphorylation within the first 15 min (early inhibition), then stimulated ERK1/2 phosphorylation after 15 min of SLD treatment (late stimulation) in BEL-7402 cells, displaying biphasic regulatory features. Other PLA(2) inhibitors such as the cytosolic and Ca(2+)-independent PLA(2) inhibitor methyl arachidonyl fluorophosphonate, and another sPLA(2) inhibitor, thioetheramide-phosphatidylcholine, only transiently inhibited ERK1/2 phosphorylation and did not display the stimulatory effect. The early inhibition of ERK1/2 phosphorylation by SLD was reversed by the PLA(2) metabolite arachidonic acid, while the late stimulation was abrogated by constitutively active myristolated-Akt. Furthermore, SLD dose- and time-dependently inhibited the phosphorylation of Raf-1 on Ser 259, which is an established event by which Akt inhibits ERK1/2 activation. Taken together, these data demonstrate a biphasic regulation of ERK1/2 phosphorylation by SLD in a time-dependent manner, i.e., early inhibition and late stimulation. The early inhibition of ERK1/2 phosphorylation is mediated by sPLA(2), at least in part, and the late stimulation is effected through SLD inhibition of Akt. These findings provide further insight into the mechanisms underlying the pharmacological effect of SLD.
Cancer biology & therapy 09/2006; 5(8):988-92. · 3.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Eleven compounds have been identified from the whole plants of Syzygium levinei (Myrtaceae) on the basis of spectroscopic analysis and chemical methods. Among these compounds, (Z)-1-(2,6-dihydroxy-4-methoxyphenyl)-oct-5-en-1-one (1), (3 E,7 Z)-1-(2,6-dihydroxy-4-methoxyphenyl)-deca-3,7-dien-1-one (2), and 1-(2-O-beta-D-glucopyranosyl-5,6-dihydroxy-4-methoxyphenyl)-octan-1-one (3) were characterized as new alkyl phloroglucinol derivatives, and 1-(2,6-dihydroxy-4-methoxyphenyl)-hexan-1-one (4) was identified as a new natural product. Compounds 1, 2, and 4 were found to inhibit the proliferation of leukemia K562 and HL-60 cells and also to induce the differentiation of K562 cells as determined by the appearance of matured morphology and the increase in the intracellular hemoglobin level.
[Show abstract][Hide abstract] ABSTRACT: 2alpha,7beta,20alpha-Trihydroxy-3beta,21-dimethoxy-5-pregnene (1), 6,7,9alpha-trihydroxy-3,8,11alpha-trimethylcyclohexo-[d,e]-coumarin (2), 3beta-hydroxy-27-benzoyloxylup-20(29)-en-28-oic acid (3), and 3beta-hydroxy-27-benzoyloxylup-20(29)-en-28-oic acid methyl ester (4), along with 24 known compounds were isolated and structurally characterized from roots and aerial parts of Helicteres angustifolia (Sterculiaceae). In a preliminary bioassay, the two cucurbitacin derivatives, cucurbitacin D and J exhibited significant inhibitory activities against the growth of both hepatocellular carcinoma BEL-7402 cells and malignant melanoma SK-MEL-28 cells in vitro.
[Show abstract][Hide abstract] ABSTRACT: The Ras/Raf/extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling pathway is known to cross-talk with other signaling pathways, including phosphatidylinositol 3-kinase (PI3K)/Akt pathway. However, the role of PI3K in ERK-1/2 activation induced by tyrosine kinase receptors was not fully understood. Here, we report that two structurally distinct PI3K inhibitors, wortmannin and LY294002, inhibited insulin-induced activation of ERK1/2 but had no effect on EGF-induced activation of ERK1/2 in hepatocellular carcinoma BEL-7402 and SMMC-7721 cells, breast cancer MCF-7 cells, and prostate cancer LNCaP cells. Although protein kinase C could act as a mediator between PI3K and ERK1/2, protein kinase C inhibitor chelerythrine chloride did not inhibit insulin-induced ERK1/2 activation. Both insulin- and EGF-induced ERK1/2 activation are strictly dependent on Ras activation, however, wortmannin only inhibited insulin-induced, but not EGF-induced Ras activation. These results indicate that PI3K plays different roles in the activation of Ras/ERK1/2 signaling by insulin and EGF, and that insulin-stimulated, but not EGF-stimulated, ERK1/2 and Akt signalings diverge at PI3K.
European Journal of Cell Biology 06/2006; 85(5):367-74. · 3.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cyclic AMP (cAMP), one of the most important intracellular second messengers, has been reported to inhibit proliferation of human hepatocellular carcinoma (HCC) cells via negatively regulating p42/44 mitogen-activated protein kinase. Here, we reported that cAMP inhibited the proliferation of HCC BEL-7402 cells via a novel mechanism. Forskolin, an activator of adenylate cyclase, inhibited fetal bovine serum (FBS)-stimulated BEL-7402 cell proliferation in a dose- and time-dependent manner, along with the inhibition of FBS-stimulated serine/threoine protein kinase Akt (also known as PKB) phosphorylation which is required for Akt activation and this effect was mimicked by 8-Br cAMP. Forskolin also inhibited Akt phosphorylation stimulated by other growth factors such as IGF-1, epidermal growth factor, and insulin. These inhibitions were found not only in BEL-7402 cells, but also in another HCC cell line SMMC-7721 cells. Myr-Akt (myristolated-Akt), a constitutively active Akt which was relatively resistant to cAMP inhibition, conferred BEL-7402 cells resistance to cAMP treatment. However, overexpression of Myr-Akt alone was not sufficient to stimulate BEL-7402 cell proliferation. cAMP inhibited FBS-stimulated Akt phosphorylation in a cAMP-dependent protein kinase-dependent manner. Further studies demonstrated that cAMP inhibited FBS-induced membrane localization of 3-phosphoinositide-dependent kinase 1 (PDK-1) which is a required process for PDK-1 to phosphorylate Akt, but had no significant effect on phosphoinositide 3-kinase activity. These results indicate that cAMP inhibition of proliferation of HCC cells is mediated by Akt and cAMP inhibits Akt activation via blocking membrane localization of PDK-1.
Cancer biology & therapy 12/2005; 4(11):1240-7. · 3.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The marine natural product 12-epi-scalaradial (SLD) is a specific secretory phospholipase A(2) (sPLA(2)) inhibitor. However, little is known about whether this compound has other pharmacological effects. Here, we revealed a novel effect of SLD on epidermal growth factor receptor (EGFR)-mediated Akt phosphorylation. SLD dose- and time-dependently inhibited epidermal growth factor (EGF)-stimulated Akt phosphorylation, which is required for Akt activation. SLD also blocked the EGF-stimulated membrane translocation of 3-phosphoinositide-dependent protein kinase 1 and inhibited phosphatidylinositol 3-kinase activity. This inhibition is specific for SLD because other phospholipase inhibitors, including sPLA(2) inhibitor thioetheramide-phosphatidylcholine, cytosolic PLA(2) inhibitor arachidonyl trifluoromethyl ketone, cytosolic PLA(2) and Ca(2+)-independent PLA(2) inhibitor methyl arachidonyl fluorophosphonate, phospholipase C inhibitor U73122, and cyclooxygenases inhibitor indomethacin, failed to inhibit EGF-stimulated Akt phosphorylation. Furthermore, arachidonic acid, the main sPLA(2)-catalyzed metabolite, was not able to rescue SLD inhibition of EGF-stimulated Akt phosphorylation. Overexpression of group IIA or group X sPLA(2) did not reverse the inhibitory effect of SLD on Akt phosphorylation, either. Our results demonstrate that SLD inhibits EGFR-mediated Akt phosphorylation, and this novel effect of SLD is independent of sPLA(2).
Journal of Pharmacology and Experimental Therapeutics 10/2005; 314(3):1210-7. · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A convergent synthesis of pyrrolidine analogues of solamin, which possessed a pyrrolidine in place of the tetrahydrofuran ring, was presented in a facile route from 2,5-trans-bis(methoxycarbonyl)pyrrolidine. The stereochemistry of pyrrolidine core unit was determined by 1H NMR spectroscopic analysis.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2005; 46(32):5309-5312.
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.