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ABSTRACT: Stromal cell-derived factor-1α (SDF-1α) is a ligand for C-X-C chemokine receptor type 4 (CXCR4), which contributes to the metastasis of cancer cells by promoting cell migration. Here, we show that the SDF-1α/CXCR4 axis can significantly increase invasion of esophageal carcinoma (EC) cells. We accomplished this by examining the effects of CXCR4 knockdown as well as treatment with a CXCR4-neutralizing antibody and the CXCR4-specific inhibitor AMD3100. Curcumin suppressed SDF-1α-induced cell invasion and matrix metalloproteinase-2 (MMP-2) promoter activity, cell surface localization of CXCR4 at lipid rafts, and lipid raft-associated ras-related C3 botulinum toxin substrate 1 (Rac1)/phosphatidylinositol 3-kinase (PI3K) p85α/Akt signaling. Curcumin inhibited SDF-1α-induced cell invasion by suppressing the Rac1-PI3K signaling complex at lipid rafts but did not abrogate lipid raft formation. We further demonstrate that the attenuation of lipid raft-associated Rac1 activity by curcumin was critical for the inhibition of SDF-1α-induced PI3K/Akt/NF-κB activation, cell surface localization of CXCR4 at lipid rafts, MMP-2 promoter activity, and cell invasion. Collectively, our results indicate that curcumin inhibits SDF-1α-induced EC cell invasion by suppressing the formation of the lipid raft-associated Rac1-PI3K-Akt signaling complex, the localization of CXCR4 with lipid rafts at the cell surface, and MMP-2 promoter activity, likely through the inhibition of Rac1 activity. © 2012 Wiley Periodicals, Inc.
Molecular Carcinogenesis 11/2012; · 3.16 Impact Factor
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ABSTRACT: Using short hairpin RNA against p53, transient ectopic expression of wild-type p53 or mutant p53 (R248W or R175H), and a p53- and p21-dependent luciferase reporter assay, we demonstrated that growth arrest and apoptosis of FaDu (human pharyngeal squamous cell carcinoma), Hep3B (hepatoma), and MG-63 (osteosarcoma) cells induced by aloe-emodin (AE) are p53-independent. Co-immunoprecipitation and small interfering RNA (siRNA) studies demonstrated that AE caused S-phase cell cycle arrest by inducing the formation of cyclin A-Cdk2-p21 complexes through extracellular signal-regulated kinase (ERK) activation. Ectopic expression of Bcl-X(L) and siRNA-mediated Bax attenuation significantly inhibited apoptosis induced by AE. Cyclosporin A or the caspase-8 inhibitor Z-IETD-FMK blocked AE-induced loss of mitochondrial membrane potential and prevented increases in reactive oxygen species and Ca(++). Z-IETD-FMK inhibited AE-induced apoptosis, Bax expression, Bid cleavage, translocation of tBid to mitochondria, ERK phosphorylation, caspase-9 activation, and the release of cytochrome c, apoptosis-inducing factor (AIF), and endonuclease G from mitochondria. The stability of the mRNAs encoding caspase-8 and -10-associated RING proteins (CARPs) 1 and 2 was affected by AE, whereas CARP1 or 2 overexpression inhibited caspase-8 activation and apoptosis induced by AE. Collectively, our data indicate AE induces caspase-8-mediated activation of mitochondrial death pathways by decreasing the stability of CARP mRNAs in a p53-independent manner.
Journal of Cellular Biochemistry 02/2011; 112(4):1176-91. · 2.87 Impact Factor
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ABSTRACT: Aloe-emodin (AE), extracted from the rhizome of Rheum palmatum, has an anti-proliferative effect on different human cancer cell lines. Nonetheless, the underlying mechanism by which AE inhibits nasopharyngeal carcinoma (NPC) cell invasion is still unclear. The results of this study show that treatment of NPC cells with growth suppressive concentrations of AE caused cell cycle arrest at the S-G(2)/M phase. Coimmunoprecipitation and small interfering RNA (siRNA) studies demonstrated that AE-induced cell cycle arrest in NPC cells was associated with increasing levels of cyclin B1 bound to cyclin-dependent kinase 1. The inhibition of NPC cell invasion by AE was evidenced through the suppression of matrix metalloproteinases-2 (MMP-2) expression. MMP-2 promoter activity and cell invasion were inhibited by p38 mitogen-activated protein kinase (MAPK) siRNA, inhibitor 4-(4-Fluorophenyl)-2-[4-(methylsulfinyl)phenyl]-5-(4-pyridyl)-1H-imidazole (SB203580), and AE, but not by JNK siRNA and inhibitor 1,9-pyrazoloanthrone. Treatment with AE, SB203580, NF-kappaB inhibitors N-p-tosyl-(L)-phenylalanine chloromethyl ketone (TPCK) and pyrrolidine dithiocarbamate (PDTC) or transfection with p38 MAPK siRNA significantly inhibited NF-kappaB transcriptional activity. In addition, TPCK and PDTC treatment inhibited the expression and promoter activity of MMP-2 and thereby significantly inhibited cell invasion activity. The involvement of p38 MAPK activity in NF-kappaB-mediated MMP-2 function was further confirmed through the attenuation of p38 MAPK by SB203580 and NF-kappaB ectopic expression. Collectively, our results indicate that AE inhibits invasion of NPC cells by suppressing the expression of MMP-2 via the p38 MAPK-NF-kappaB signaling pathway.
Molecular Carcinogenesis 09/2010; 49(9):783-97. · 3.16 Impact Factor
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ABSTRACT: Aloe-emodin (AE), a natural, biologically active compound from the rhizome of Rheum palmatum, has been shown to induce apoptosis in several cancer cell lines in vitro. However, its molecular mechanism of action in the apoptosis induction of human nasopharyngeal carcinoma (NPC) cells has not been explored. This study shows that AE induced G(2)/M phase arrest by increasing levels of cyclin B1 bound to Cdc2, and also caused an increase in apoptosis of NPC cells, which was characterized by morphological changes, nuclear condensation, DNA fragmentation, caspase-3 activation, cleavage of poly (ADP-ribose) polymerase (PARP) and increased sub-G(1) population. Treatment of NPC cells with AE also resulted in a decrease in Bcl-X(L) and an increase in Bax expression. Ectopic expression of Bcl-X(L) but not Bcl-2 or small interfering RNA (siRNA)-mediated attenuation of Bax suppressed AE-induced apoptotic cell death. AE-induced loss of mitochondrial membrane potential (MMP) and increase in cellular Ca(++) content, reactive oxygen species (ROS) and apoptotic cell death were suppressed by the treatment of cyclosporin A (CsA) or caspase-8 inhibitor Z-IETD-FMK. Co-treatment with caspase-9 inhibitor Z-LEHD-FMK could inhibit AE-induced cell death and the activation of caspase-3 and -9. In addition, suppression of caspase-8 with the specific inhibitor Z-IETD-FMK inhibited AE-induced the activation of Bax, the cleavage of Bid, the translocation of tBid to the mitochondria and the release of cytochrome c, apoptosis-inducing factor (AIF) and Endo G from the mitochondria and subsequent apoptosis. Taken together, these results indicate that the caspase-8-mediated activation of the mitochondrial death pathway plays a critical role in AE-induced apoptosis of NPC cells.
Cancer letters 11/2009; 291(1):46-58. · 4.86 Impact Factor
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ABSTRACT: Progression of cancer invasion is believed to be dependent on the remodeling of extracellular matrix induced by tumor cells. Rhein has been shown to inhibit the growth and proliferation of human nasopharyngeal carcinoma (NPC) cells. However, the molecular mechanism underlying rhein-induced inhibition of cancer invasion has not been explored. Herein, we show that rhein could inhibit the invasion and migration of NPC cells in vitro. Rhein inhibits invasion by reducing the expression of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF). Moreover, we demonstrate that the pathway involved in rhein-inhibited invasion is presumably through the growth factor receptor bound protein 2/son of sevenless-Ras-mitogen-activated protein kinase (GRB2/SOS-Ras-MAPK) pathway, as shown by an decrease in the expression levels of GRB2, SOS-1 and Ras as well as led to suppression of the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK. Further study has shown that rhein also inhibited activation of transcription factor nuclear factor kappaB (NF-kappaB), which is known to implicate the regulation of MMP-9 and VEGF gene expression in cancer invasion. Our findings suggest that rhein inhibits the invasion of NPC cells may be mediated in part through the suppression of MMP-9 and VEGF expression via the modulation of NF-kappaB signaling pathway.
Oral Oncology 10/2008; 45(6):531-7. · 2.86 Impact Factor
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ABSTRACT: In the present study, we report the development of a sensitive and selective assay based on LC (liquid chromatography)-MS/MS (tandem MS) to simultaneously measure N7-MeG (N7-methylguanine) and N7-EtG (N7-ethylguanine) in DNA hydrolysates. With the use of isotope internal standards (15N5-N7-MeG and 15N5-N7-EtG) and on-line SPE (solid-phase extraction), the detection limit of this method was estimated as 0.42 fmol and 0.17 fmol for N7-MeG and N7-EtG respectively. The high sensitivity achieved here makes this method applicable to small experimental animals. This method was applied to measure N7-alkylguanines in liver DNA from mosquito fish (Gambusia affinis) that were exposed to NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) alone or their combination over a wide range of concentrations (1-100 mg/l). Results showed that the background level of N7-MeG in liver of control fish was 7.89+/-1.38 mmol/mol of guanine, while N7-EtG was detectable in most of the control fish with a range of 0.05-0.19 mmol/mol of guanine. N7-MeG and N7-EtG were significantly induced by NDMA and NDEA respectively, at a concentration as low as 1 mg/l and increased in a dose-dependent manner. Taken together, this LC-MS/MS assay provides the sensitivity and high throughput required to evaluate the extent of alkylated DNA lesions in small animal models of cancer induced by alkylating agents.
Biochemical Journal 04/2007; 402(3):483-90. · 4.90 Impact Factor
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ABSTRACT: Apoptosis is a physiological mechanism for eliminating malignant cells, including cancer cells, without eliciting damage to normal cells or surrounding tissues. Here, we report that rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid), a major constituent in the rhizome of rhubarb, induced apoptosis of human nasopharyngeal carcinoma (NPC) cells. Rhein induced apoptosis in NPC cells as demonstrated by increased nuclear condensation and DNA fragmentation. Moreover, for the first time in NPC cells it was demonstrated that the pathway involved in rhein-induced apoptosis is caspase-dependent, presumably through the endoplasmic reticulum (ER) stress pathway, as shown by an increase in the levels of glucose-regulated protein 78 (GRP 78), PKR-like ER kinase (PERK), activating transcription factor 6 (A TF6) and CCAA TIenhancer-binding protein homologous protein (CHOP) as well as the activation of caspase-3, -8, -9 and -12. This increased susceptibility to ER stress-induced apoptosis may be due to an increased accumulation of reactive oxygen species (ROS). Rapid accumulation of calcium (Ca2+) and a decrease in the mitochondrial membrane potential (MMP) were also observed. Cytochrome c and apoptosis-inducing factor (AIF) were released upon treatment with rhein. Taken together, these results suggest that ER stress and Ca2+-dependent mitochondrial death pathway may be involved in rhein-induced apoptosis in NPC cells.
Anticancer research 27(5A):3313-22. · 1.73 Impact Factor
