Inostamycin, an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase, suppresses invasion ability by reducing productions of matrix metalloproteinase-2 and -9 and cell motility in HSC-4 tongue carcinoma cell line

Aglycone Polyether Nanchangmycin and Its Homologues Exhibit Apoptotic and Antiproliferative Activities against Cancer Stem Cells

The potential of the polyether salinomycin as an inhibitory agent against cancer stem cells has attracted interest in this family of compounds. In this study, we found that the aglycone polyether nanchangmycin and its homologues show promising activities against breast cancer stem cells as well as 38 other different types of cancer cells by in vitro assays. We found that aglycone polyethers caused elevations in calcium levels, an accumulation of reactive oxygen species and mitochondrial inner membrane permeability to H⁺ and K⁺, resulting in the release of cytochrome c and apoptosis-inducing factor and the triggering of caspase-dependent apoptosis. Our analyses also indicate that aglycone polyethers are potent Wnt/β-catenin signaling inhibitors, blocking the Wnt pathway and resulting in reduced cell survival. Notably, the key autophagy-related proteins LC3A/B were also activated by aglycone polyether treatment. Furthermore, nanchangmycin showed inhibitory effects toward somatic tumors developed from MCF-7 paclitaxel-resistant breast cancer cells injected into BALB/c mice. Our study not only provides promising candidates for therapy against cancer stem cells but also provides the groundwork for identifying stronger therapeutic agents among the natural polyether compounds.

Discovery of potential biomarkers in human melanoma cells with different metastatic potential by metabolic and lipidomic profiling

Malignant melanoma, characterized by its ability to metastasize to other organs, is responsible for 90% of skin cancer mortality. To investigate alterations in the cellular metabolome and lipidome related to melanoma metastasis, gas chromatography-mass spectrometry (GC-MS) and direct infusion-mass spectrometry (DI-MS)-based metabolic and lipidomic profiling were performed on extracts of normal human melanocyte (HEMn-LP), low metastatic melanoma (A375, G361), and highly metastatic melanoma (A2058, SK-MEL-28) cell lines. In this study, metabolomic analysis identified aminomalonic acid as a novel potential biomarker to discriminate between different stages of melanoma metastasis. Uptake and release of major metabolites as hallmarks of cancer were also measured between high and low metastatic melanoma cells. Lipid analysis showed a progressive increase in phosphatidylinositol (PI) species with saturated and monounsaturated fatty acyl chains, including 16:0/18:0, 16:0/18:1, 18:0/18:0, and 18:0/18:1, with increasing metastatic potential of melanoma cells, defining these lipids as possible biomarkers. In addition, a partial-least-squares projection to latent structure regression (PLSR) model for the prediction of metastatic properties of melanoma was established, and central metabolic and lipidomic pathways involved in the increased motility and metastatic potential of melanoma cells were identified as therapeutic targets. These results could be used to diagnose and control of melanoma metastasis.

Acidic extracellular pH promotes epithelial mesenchymal transition in Lewis lung carcinoma model

Background

Epithelial mesenchymal transition (EMT) is thought to be an essential feature of malignant tumor cells when they spread into the stroma. Despite the extracellular acidity of tumor tissues, the effect of acidic extracellular pH (pH_e) on EMT in carcinoma models, including the Lewis lung carcinoma (LLC) model, remains unclear.

Methods

High and low metastatic LLC variants were generated by repeated tail vein injection of metastatic cells. DMEM/F12 medium, which has been supplemented with 15 mM HEPES, 4 mM phosphoric acid, and 1 g/L NaHCO₃ and adjusted to the desire pH with HCl or NaOH, was used for cell culture. EMT marker gene expression was determined by quantitative reverse transcription-polymerase chain reaction. Migration and invasion activities were analyzed by wound healing assay and the Boyden chamber assay through Matrigel®, respectively.

Results

Low metastatic variant LLCm1 cells showed a cobble-stone like morphology at pH_e 7.4. At pH_e 6.8, however, their morphology became fibroblastic, similar in shape to high metastatic variant LLCm4 cells. Steady state levels of matrix metalloproteinase-9 (Mmp9) mRNA were induced by acidic pH_e, maximizing at pH 6.8, with the levels of Mmp9 mRNA higher in LLCm4 than in LLCm1 cells. Both variants showed decreased levels of E-cadherin and increased levels of vimentin at pH_e 6.8. Acidic pH_e also induced expression of mRNAs encoding the E-cadherin repressors, Zeb2, Twist1 and Twist2, as well as enhancing cell motility and in vitro invasion through Matrigel®.

Conclusions

Acidic pH_e can induce EMT in some types of carcinoma.

Present and Future of EGFR Inhibitors for Head and Neck Squamous Cell Cancer

Although EGFR is expressed at high levels in head and neck squamous cell carcinomas (HNSCCs) and mutations are extremely rare, monotherapy with EGFR inhibitors has shown limited success. The PI3kinase/Akt pathway is responsible for cellular survival, and inhibition of phosphatidylinositol (PI) synthesis has antiproliferative, anti-invasive, and antiangiogenesis effects on HNSCC. Molecular crosstalk has been observed between EGFR and IGF1R signaling through the PI3kinase/Akt pathway in HNSCC, as has molecular crosstalk between the NFκB and STAT3 signaling pathways. Therefore, the combination of an EGFR antagonist with an agent that inhibits the activation of both Akt and NFκB may overcome resistance to EGFR antagonists in HNSCC.

Clinical significance of phosphatidyl inositol synthase overexpression in oral cancer

BACKGROUND

We reported increased levels of phosphatidyl inositol synthase (PI synthase), (enzyme that catalyses phosphatidyl inositol (PI) synthesis-implicated in intracellular signaling and regulation of cell growth) in smokeless tobacco (ST) exposed oral cell cultures by differential display. This study determined the clinical significance of PI synthase overexpression in oral squamous cell carcinoma (OSCC) and premalignant lesions (leukoplakia), and identified the downstream signaling proteins in PI synthase pathway that are perturbed by smokeless tobacco (ST) exposure.

METHODS

Tissue microarray (TMA) Immunohistochemistry, Western blotting, Confocal laser scan microscopy, RT-PCR were performed to define the expression of PI synthase in clinical samples and in oral cell culture systems.

RESULTS

Significant increase in PI synthase immunoreactivity was observed in premalignant lesions and OSCCs as compared to oral normal tissues (p = 0.000). Further, PI synthase expression was significantly associated with de-differentiation of OSCCs, (p = 0.005) and tobacco consumption (p = 0.03, OR = 9.0). Exposure of oral cell systems to smokeless tobacco (ST) in vitro confirmed increase in PI synthase, Phosphatidylinositol 3-kinase (PI3K) and cyclin D1 levels.

CONCLUSION

Collectively, increased PI synthase expression was found to be an early event in oral cancer and a target for smokeless tobacco.

Inhibition of MMP-3 activity and invasion of the MDA-MB-231 human invasive breast carcinoma cell line by bioflavonoids

AIM

Stromelysin 1 (matrix metalloproteinase 3; MMP-3) is an enzyme known to be involved in tumor invasion and metastasis. In this study, flavonoids from vegetables and fruits, such as quercetin, kaempferol, genistein, genistin, and daidzein, were tested for their ability to modulate the secretion and activity of MMP-3 in the MDA-MB-231 breast cancer cell line. In addition, we investigated the in vitro effects of flavonoids on MDA-MB-231 cell invasion.

METHODS

The toxic concentration range of flavonoids was evaluated using the MTT assay. The ability of MDA-MB-231 cells to invade was evaluated using a modified Boyden chamber system. The activity of MMP-3 was determined by casein zymography. The secretion of MMP-3 was evaluated using Western blotting, casein zymography and confirmed by ELISA.

RESULTS

Some putative flavonoids, ie, quercetin and kaempferol (flavonols), significantly inhibited the in vitro invasion of MDA-MB-231 cells in a concentration-dependent manner, with IC(50) values of 27 and 30 micromol/L, respectively. Quercetin and kaempferol also reduced MMP-3 activity in a dose-dependent manner, with IC(50) values in the range of 30 micromol/L and 45 micromol/L, respectively. None of the flavonoids had a significant effect on the secretion of MMP-3.

CONCLUSION

These data show that the flavonols quercetin and kaempferol have higher anti-invasion potency and higher MMP-3 inhibitory activity than isoflavones genistein, genistin and daidzein. In contrast, neither flavonols nor isoflavones have any effect on MMP-3 secretion.

Transcription regulation of the Saccharomyces cerevisiae PIS1 gene by inositol and the pleiotropic regulator, Ume6p

In Saccharomyces cerevisiae, transcription of most of the phospholipid biosynthetic genes (e.g. INO1, CHO1, CHO2 and OPI3) is repressed by growth in the presence of inositol and choline and derepressed in their absence. This regulation requires the Ino2p and Ino4p activators and the Opi1p repressor. The PIS1 structural gene is required for the synthesis of the essential lipid phosphatidylinositol. Previous reports show that PIS1 expression is uncoupled from inositol/choline regulation, but is regulated by carbon source, hypoxia and zinc. However, in this study we found that the expression of PIS1 is induced twofold by inositol. This regulation did not require Ino2p and Ino4p, although Ino4p was required for full expression. Ino4p is a basic helix-loop-helix protein that requires a binding partner. Curiously, none of the other basic helix-loop-helix proteins affected PIS1 expression. Inositol induction did require another general regulator of phospholipid biosynthesis, Ume6p. Ume6p was found to be a positive regulator of PIS1 gene expression. Ume6p, and several associated factors, were required for inositol-mediated induction and chromatin immunoprecipitation analysis showed that Ume6p directly regulates PIS1 expression. Thus, we demonstrate novel regulation of the PIS1 gene by Ume6p.

Acidic extracellular pH increases calcium influx-triggered phospholipase D activity along with acidic sphingomyelinase activation to induce matrix metalloproteinase-9 expression in mouse metastatic melanoma

Acidic extracellular pH is a common feature of tumor tissues. We have reported that culturing cells at acidic pH (5.4-6.5) induced matrix metalloproteinase-9 expression through phospholipase D, extracellular signal regulated kinase 1/2 and p38 mitogen-activated protein kinases and nuclear factor-kappaB. Here, we show that acidic extracellular pH signaling involves both pathways of phospholipase D triggered by Ca2+ influx and acidic sphingomyelinase in mouse B16 melanoma cells. We found that BAPTA-AM [1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl) ester], a chelator of intracellular free calcium, and the voltage dependent Ca2+ channel blockers, mibefradil (for T-type) and nimodipine (for L-type), dose-dependently inhibited acidic extracellular pH-induced matrix metalloproteinase-9 expression. Intracellular free calcium concentration ([Ca2+]i) was transiently elevated by acidic extracellular pH, and this [Ca2+]i elevation was repressed by EGTA and the voltage dependent Ca2+ channel blockers but not by phospholipase C inhibitor, suggesting that acidic extracellular pH increased [Ca2+]i through voltage dependent Ca2+ channel. In contrast, SR33557, an L-type voltage dependent Ca2+ channel blocker and acidic sphingomyelinase inhibitor, attenuated matrix metalloproteinase-9 induction but did not affect calcium influx. We found that acidic sphingomyelinase activity was induced by acidic extracellular pH and that the specific acidic sphingomyelinase inhibitors (perhexiline and desipramine) and siRNA targeting aSMase/smpd1 could inhibit acidic extracellular pH-induced matrix metalloproteinase-9 expression. BAPTA-AM reduced acidic extracellular pH-induced phospholipase D but not acidic sphingomyelinase acitivity. The acidic sphingomyelinase inhibitors did not affect the phosphorylation of extracellular signal regulated kinase 1/2 and p38, but they suppressed nuclear factor-kappaB activity. These data suggest that the calcium influx-triggered phospholipase D and acidic sphingomyelinase pathways of acidic extracellular pH induced matrix metalloproteinase-9 expression, at least in part, through nuclear factor-kappaB activation.

Signal transduction pathways involved in epithelial-mesenchymal transition in oral cancer compared with other cancers

Epithelial-mesenchymal transition (EMT) is a central mechanism governing destined cell movement in embryonic development. Emerging evidence reveals that EMT characterizing the progression of many carcinomas is linked to the acquisition of an invasive and metastatic phenotype. While it is established that EMT is controlled by well-conserved mechanisms, additional research is required for various tissue- or tumor-specific transitions. We review the literature related to the major components of EMT including adhesion molecules, cytoskeleton reorganization and signaling pathways in oral cancer.

Studies on the synthesis of the inostamycin natural products: a reductive aldol/reductive Claisen approach to the C10-C24 ketone fragment

[reaction: see text] An approach to the C10-C24 ketone fragment of the inostamycin family of polyether antibiotics is described. The synthetic strategy utilizes an asymmetric Rh-catalyzed reductive aldol reaction and a stereoselective Rh-catalyzed reductive Claisen rearrangement as the key steps in formation of alkene and vinyl iodide synthons, respectively.

Human tongue carcinoma growth is inhibited by selective antigelatinolytic peptides

Matrix metalloproteinases (MMP-2 and MMP-9, or gelatinases) are involved in tongue SCC invasion, metastasis and angiogenesis. We have recently shown that a novel and selective hydrophobic cyclic CTTHWGFTLC (CTT1) peptide is inhibitor for MMP-2 and MMP-9 (Koivunen et al., Nat Biotechnol 1999; 17:768-74). In this study, we demonstrate that both the new hydrophilic derivate GRENYHGCTTHWGFTLC (CTT2) peptide and the CTT1 peptide inhibited specifically the human tongue squamous cell carcinoma (HSC-3) cell-derived gelatinolytic activity and in vitro invasion and migration of these cells (p < or = 0.049). In situ zymography revealed that both peptides also inhibited clearly almost all of the gelatinolytic activity present in the human tongue SCC tissue sections, indicating that MMP-2 and MMP-9 are the major gelatinases detected in the tongue carcinomas. However, CTT2 did not inhibit the type I collagen degradation by human collagenases (MMP-1, MMP-8 and MMP-13). Furthermore, CTT2 reduced the blood vessel density (p < or = 0.043) and clearly improved the survival of the mice bearing human tongue carcinoma xenografts (p < or = 0.012). Overall, we suggest that CTT1 and CTT2 peptides being selective gelatinase inhibitors with significant anti-tumor properties could be useful to diminish the invasion and angiogenesis of human tongue carcinomas characterized by enhanced gelatinolytic activity in tumors.

Broccoli and watercress suppress matrix metalloproteinase-9 activity and invasiveness of human MDA-MB-231 breast cancer cells

A high dietary intake of cruciferous vegetables has been associated with a reduction in numerous human pathologies particularly cancer. In the current study, we examined the inhibitory effects of broccoli (Brassica oleracea var. italica) and watercress (Rorripa nasturtium aquaticum) extracts on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cancer cell invasion and matrix metalloproteinase-9 activity using human MDA-MB-231 breast cancer cells. Aberrant overexpression of matrix metalloproteinases, including metalloproteinase-9, is associated with increased invasive potential in cancer cell lines. Our results demonstrate that extracts of broccoli and Rorripa suppressed TPA-induced MMP-9 activity and invasiveness in a concentration dependent manner as determined by zymographic analysis. Furthermore, fractionation of individual extracts followed by liquid chromatography mass spectroscopy analysis (LC-MS) revealed that the inhibitory effects of each vegetable were associated with the presence of 4-methysulfinylbutyl (sulforaphane) and 7-methylsulphinylheptyl isothiocyanates. Taken together, our data indicate that isothiocyanates derived form broccoli and Rorripa inhibit metalloproteinase 9 activities and also suppress the invasive potential of human MDA-MB-231 breast cancer cells in vitro. The inhibitory effects observed in the current study may contribute to the suppression of carcinogenesis by diets high in cruciferous vegetables.

Inostamycin suppresses vascular endothelial growth factor-stimulated growth and migration of human umbilical vein endothelial cells

Angiogenesis involves multiple steps including proliferation and migration of endothelial cells. In the present study, we determined the effect of inostamycin (an inhibitor of phosphatidylinositol synthesis) on vascular endothelial growth factor (VEGF)-induced proliferation and migration of human umbilical vein endothelial cells (HUVECs). Inostamycin significantly attenuated both VEGF-induced proliferation and migration of HUVECs. Inostamycin inhibited activation of mitogen-activated kinases (ERK and p38) and elevation of cyclin D1 induced by VEGF. These data suggest that inostamycin reduced both proliferation and migration of HUVECs by targeting ERK-cyclin D1 and p38, respectively.

Acidic extracellular pH induces matrix metalloproteinase-9 expression in mouse metastatic melanoma cells through the phospholipase D-mitogen-activated protein kinase signaling

The extracellular pH (pHe) of tumor tissues is often acidic, which can induce the expression of several proteins. We previously showed that production of matrix metalloproteinase-9 (MMP-9) was induced by culturing cells at acidic pHe (5.4-6.5). Here we have investigated the signal transduction pathway by which acidic pHe induces MMP-9 expression. We found that acidic pHe (5.9) activated phospholipase D (PLD), and inhibition of PLD activity by 1-butanol and Myr-ARF6 suppressed the acidic pHe-induced MMP-9 expression. Exogenous PLD, but not phosphatidylinositol-specific PLC or PLA2, mimicked MMP-9 induction by acidic pHe. Western blot analysis revealed that acidic pHe increased the steady-state levels of phosphorylated extracellular signal-regulated kinases 1/2 and p38 and that the PLD inhibitors suppressed these increases. Using 5'-deletion mutant constructs of the MMP-9 promoter, we found that the acidic pHe-responsive region was located at nucleotide -670 to -531, a region containing the NF kappa B binding site. A mutation into the NF kappa B binding site reduced, but not completely, the acidic pHe-induced MMP-9 promoter activity, and NF kappa B activity was induced by acidic pHe. Pharmacological inhibitors specific for mitogen-activated protein kinase kinase 1/2 (PD098059) and p38 (SB203580) attenuated the acidic pHe-induced NF kappa B activity and MMP-9 expression. These data suggest that PLD, mitogen-activated protein kinases (extracellular signal-regulated kinases 1/2 and p38), and NF kappa B mediate the acidic pHe signaling to induce MMP-9 expression. A transcription factor(s) other than NF kappa B may also be involved in the MMP-9 expression.

Inhibitory effect of emodin on tumor invasion through suppression of activator protein-1 and nuclear factor-kappaB

3-Methyl-1,6,8-trihydroxyanthraquinone (emodin) is an active component from the rhizome of Rheum palmatum, a widely used traditional Chinese herb. In this study, we found that emodin significantly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced in vitro invasion of human cancer cells including HSC5 and MDA-MB-231 cells. Matrix metalloproteinases (MMPs) are known to be associated with cancer invasion. Zymographic analysis showed that emodin suppressed TPA-induced MMP-9 activity in a concentration-dependent manner. We further demonstrated that emodin reduced the transcriptional activity of activator protein-1 (AP-1) and nuclear factor kappaB (NF-kappaB), two important nuclear transcription factors involved in MMP-9 expression. Emodin suppressed the phosphorylation of two mitogen-activated protein kinases, extracellular signal-regulated protein kinase and c-Jun N-terminal kinase, but not p38 kinase, leading to reduced c-Jun phosphorylation and AP-1 DNA-binding. Moreover, emodin inhibited TPA-induced degradation of inhibitor of kappaBalpha, nuclear translocation of p65, and NF-kappaB DNA-binding activity. Taken together, these results suggest that emodin inhibits the invasiveness of human cancer cells by suppressing MMP-9 expression through inhibiting AP-1 and NF-kappaB signaling pathways.

Quercetin inhibits the invasion of murine melanoma B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway

PURPOSE

On the basis of the inhibitory effect of quercetin on the invasion of melanoma B16-BL6 cells previously reported by us, the mechanisms of quercetin-mediated inhibition of invasion were further investigated in the present study.

METHODS

The ability of B16-BL6 cells to invade and migrate was evaluated in terms of the numbers of cells penetrating a reconstituted basement membrane in the Transwell coculture system. The relative levels and activities of matrix metalloproteinase-9 (MMP-9) and MMP-2 were determined by gelatin zymography and quantified using LabWorks 4.0 software.

RESULTS

The quercetin-mediated inhibition of invasion was partially blocked by phorbol-12,13-dibutyrate (PDB), a PKC (protein kinase C) activator, and by doxorubicin, a PKC inhibitor. Only the proforms of MMP-9 (92 kDa) and MMP-2 (72 kDa) were detected by gelatin zymography. Quercetin dose-dependently decreased the gelatinolytic activity of pro-MMP-9. Doxorubicin also markedly reversed the quercetin-induced decrease. Quercetin showed a dose-dependent antagonism of increases in gelatinolytic activity of pro-MMP-9 induced by PDB and free fatty acid (another PKC activator).

CONCLUSIONS

Together with the report that quercetin directly reduces PKC activity, the results reported here suggest that quercetin may inhibit the invasion of B16-BL6 cells by decreasing pro-MMP-9 via the PKC pathway.

Reduction of in vivo tumor growth by MMI-166, a selective matrix metalloproteinase inhibitor, through inhibition of tumor angiogenesis in squamous cell carcinoma cell lines of head and neck

Matrix metalloproteinases (MMPs) have been implicated in tumor invasion, metastasis, and angiogenesis. We have recently shown that MMI-166, a new orally active MMP inhibitor specific for MMP-2 and -9, suppressed experimental metastasis of Lewis lung cancer, C-H1 human colon cancer, and pancreatic cancer without affecting tumor growth in vitro. In the present study, we determined whether oral administration of MMI-166 reduces tumor growth not only in such tumors but also in squamous cell carcinoma of head and neck (SCCHN). MMI-166 inhibited both activity of MMP-2 and -9 without affecting steady state levels of their mRNAs in SCCHN. Interestingly, protein levels of MMP-2 and -9 from the cultures were drastically diminished by culturing with MMI-166. This was also observed in xenografts of MMI-166-administered mice. In addition, daily oral administration of MMI-166 (100mg/kg) inhibited local tumor growth accompanied by the reduction of blood vessel density and Ki-67-positivity and increase in terminal deoxynucleotidyl transferase-mediated cUDP nick-end labeling (TUNEL)-positivity. These results suggested that orally administered MMI-166 reduced in vivo tumor growth of SCCHN through inhibition of angiogenesis and induction of apoptosis accompanied by the reduction of MMP productions and activities. Therefore, MMI-166 seems to be useful for tumor dormancy therapy of SCCHN.

Induction of SPARC by VEGF in human vascular endothelial cells

SPARC/osteonectin/BM-40 is a matricellular protein that is thought to be involved in angiogenesis and endothelial barrier function. Previously, we have detected high levels of SPARC expression in endothelial cells (ECs) adjacent to carcinomas of kidney and tongue. Although SPARC-derived peptide showed an angiogenic effect, intact SPARC itself inhibited the mitogenic activity of vascular endothelial growth factor (VEGF) for ECs by the inhibiting phosphorylation of flt-1 (VEGF receptor 1) and subsequent ERK activation. Thus, the role of SPARC in tumor angiogenesis, stimulation or inhibition, is still unclear. To clarify the role of SPARC in tumor growth and progression, we determined the effect of VEGF on the expression of SPARC in human microvascular EC line, HMEC-1, and human umbilical vein ECs. VEGF increased the levels of SPARC protein and steady-state levels of SPARC mRNA in serum-starved HMEC-1 cells. Inhibitors (SB202190 and SB203580) of p38, a mitogen-activated protein (MAP) kinase, attenuated VEGF-stimulated SPARC production in ECs. Since intact SPARC inhibits phosphorylation ERK MAP kinase in VEGF signaling, it was suggested that SPARC plays a dual role in the VEGF functions, tumor angiogenesis, and extravasation of tumors mediated by the increased permeability of endothelial barrier function.