Metformin Induces Apoptosis and Downregulates Pyruvate Kinase M2 in Breast Cancer Cells Only When Grown in Nutrient-Poor Conditions

INTRODUCTION

Metformin is proposed as adjuvant therapy in cancer treatment because of its ability to limit cancer incidence by negatively modulating the PI3K/AKT/mTOR pathway. In vitro, in addition to inhibiting cancer cell proliferation, metformin can also induce apoptosis. The molecular mechanism underlying this second effect is still poorly characterized and published data are often contrasting. We investigated how nutrient availability can modulate metformin-induced apoptosis in three breast cancer cell lines.

MATERIAL AND METHODS

MCF7, SKBR3 and MDA-MB-231 cells were plated in MEM medium supplemented with increasing glucose concentrations or in DMEM medium and treated with 10 mM metformin. Cell viability was monitored by Trypan Blue assay and treatment effects on Akt/mTOR pathway and on apoptosis were analysed by Western Blot. Moreover, we determined the level of expression of pyruvate kinase M2 (PKM2), a well-known glycolytic enzyme expressed in cancer cells.

RESULTS

Our results showed that metformin can induce apoptosis in breast cancer cells when cultured at physiological glucose concentrations and that the pro-apoptotic effect was completely abolished when cells were grown in high glucose/high amino acid medium. Induction of apoptosis was found to be dependent on AMPK activation but, at least partially, independent of TORC1 inactivation. Finally, we showed that, in nutrient-poor conditions, metformin was able to modulate the intracellular glycolytic equilibrium by downregulating PKM2 expression and that this mechanism was mediated by AMPK activation.

CONCLUSION

We demonstrated that metformin induces breast cancer cell apoptosis and PKM2 downregulation only in nutrient-poor conditions. Not only glucose levels but also amino acid concentration can influence the observed metformin inhibitory effect on the mTOR pathway as well as its pro-apoptotic effect. These data demonstrate that the reduction of nutrient supply in tumors can increase metformin efficacy and that modulation of PKM2 expression/activity could be a promising strategy to boost metformin anti-cancer effect.

Generation and characterization of a JAK2V617F-containing erythroleukemia cell line

The JAK2V617F mutation is found in the majority of patients with myeloproliferative neoplasms (MPNs). Transgenic expression of the mutant gene causes MPN-like phenotypes in mice. We have produced JAK2V617F mice with p53 null background. Some of these mice developed acute erythroleukemia. From one of these mice, we derived a cell line designated J53Z1. J53Z1 cells were stained positive for surface markers CD71 and CD117 but negative for Sca-1, TER-119, CD11b, Gr-1, F4/80, CD11c, CD317, CD4, CD8a, CD3e, B220, CD19, CD41, CD42d, NK-1.1, and FceR1. Real time PCR analyses demonstrated expressions of erythropoietin receptor EpoR, GATA1, and GATA2 in these cells. J53Z1 cells grew rapidly in suspension culture containing fetal bovine serum with a doubling time of ∼18 hours. When transplanted into C57Bl/6 mice, J53Z1 cells induced acute erythroleukemia with massive infiltration of tumor cells in the spleen and liver. J53Z1 cells were responsive to stimulation with erythropoietin and stem cell factor and were selectively inhibited by JAK2 inhibitors which induced apoptosis of the cells. Together, J53Z1 cells belong to the erythroid lineage, and they may be useful for studying the role of JAK2V617F in proliferation and differentiation of erythroid cells and for identifying potential therapeutic drugs targeting JAK2.

Inverse correlation between Thr-669 and constitutive tyrosine phosphorylation in the asymmetric epidermal growth factor receptor dimer conformation

We have recently identified tumor necrosis factor (TNF)-α-induced phosphorylation of epidermal growth factor receptor (EGFR) at Thr-669 and Ser-1046/1047 via ERK and p38 pathways, respectively. In the present study, we investigated the roles of ligand-induced phosphorylation of serine and threonine residues in EGFR-overexpressing MDA-MB-468 breast cancer cells. Epidermal growth factor and heregulin, an ErbB3 ligand, induced the phosphorylation of Thr-669 and Ser-1046/1047. Inversely, constitutive tyrosine phosphorylation of the C-terminal domain, including Tyr-1068, was significantly downregulated on ligand stimulation. Inhibition of the ERK pathway by U0126 blocked ligand-induced Thr-669 phosphorylation as well as Tyr-1068 dephosphorylation. Downregulation of constitutive tyrosine phosphorylation of EGFR in HEK293 cells stably expressing the wild type was abolished by substitution of Thr-669 for Ala. In an asymmetric EGFR homodimer structure, one Thr-669 in the receiver kinase of the dimer was involved in downregulation. Similarly, Thr-669 in an EGFR-ErbB3 heterodimer also participated in tyrosine dephosphorylation. These results indicate that ERK-mediated Thr-669 phosphorylation suppresses constitutive tyrosine phosphosphorylation in the homo- and heterodimer asymmetric conformations of the EGFR.

[Effect of Mn(II) on the error-prone DNA polymerase iota activity in extracts from human normal and tumor cells]

The DNA polymerase iota (Pol iota), which has some peculiar features and is characterized by an extremely error-prone DNA synthesis, belongs to the group of enzymes preferentially activated by Mn2+ instead of Mg2+. In this work, the effect of Mn2+ on DNA synthesis in cell extracts from a) normal human and murine tissues, b) human tumor (uveal melanoma), and c) cultured human tumor cell lines SKOV-3 and HL-60 was tested. Each group displayed characteristic features of Mn-dependent DNA synthesis. The changes in the Mn-dependent DNA synthesis caused by malignant transformation of normal tissues are described. It was also shown that the error-prone DNA synthesis catalyzed by Pol iota in extracts of all cell types was efficiently suppressed by an RNA aptamer (IKL5) against Pol iota obtained in our work earlier. The obtained results suggest that IKL5 might be used to suppress the enhanced activity of Pol iota in tumor cells.

Glutathione peroxidase isoenzymes in human tumor cell lines

A set of human tumor cell lines was characterized in terms of the GPx isoenzymes GPx1, -2, -3 and -4. Semiquantitative PCR was used to investigate the GPx mRNA transcripts and the GPx activity was determined photometrically. As a result of culturing under standard conditions, diverse distribution of GPx mRNA and basic GPx activity was found in the investigated cell lines. PCR results showed nearly ubiquitous existence of the isoenzymes GPx1 and GPx4. GPx2 mRNA transcript was only detected in the colonic cell line CaCo-2. After detection of the GPx3 mRNA transcripts in most of the tested cell lines, an ELISA was performed to investigate if the GPx3 protein is present as well. However, the GPx3 protein could not be detected. Glutathione peroxidases contain the amino acid selenocysteine in their active centre. Selenocysteine contains selenium instead of sulfur in cysteine. Therefore, the influence of selenium on GPx activity and GPx isoenzyme distribution was investigated. Cell culturing with additional selenium showed a clear elevation of GPx activity in Mono Mac 6 cells but no gain of mRNA transcripts or any change in the isoenzyme's distribution.

IL-1β down-regulates ADAMTS-13 mRNA expression in cells of the central nervous system

ADAMTS-13 is the Von Willebrand factor (vWF) cleaving protease, responsible for the cleavage and down-regulation of the pro-thrombotic properties of ultra large VWF multimers. It is expressed predominantly by the hepatic stellate cells of the liver, but is also found to be expressed in other tissues, including brain. Reduced ADAMTS-13 is associated with a variety of thrombotic microangiopathies. Since the cellular origin and regulation of ADAMTS-13 expression in the brain is unknown, we aimed to investigate this in four different central nervous system (CNS)-derived cell lines, SHSY-5Y (human neuroblastoma), U373 (human astroglioma), CHME-3 (human foetal microglia) and hCMEC/D3 (adult human brain endothelial cells). All cell lines expressed ADAMTS-13 mRNA constitutively with neuroblastoma cells showing the highest expression. Interleukin (IL)-1β down-regulated ADAMTS-13 mRNA expression in astroglioma cells and microglial cells whereas TNF and IL-6 treatment showed no significant differences in ADAMTS-13 mRNA expression in any cell line tested. ADAMTS-13 protein expression was reduced in a dose-dependent manner only in astroglioma cells following stimulation by IL-1β. The ability of IL-1β to significantly reduce ADAMTS-13 mRNA expression in human microglia and astroglioma cells suggests a role in the haemostasis of the local microenvironment under inflammatory conditions. This is the first report of ADAMTS-13 expression in cells of the CNS; however, its function remains to be determined.

Effect of a chloride channel inhibitor, 5-nitro-2-(3-phenylpropylamino)-benzoate, on ovarian cancer cell migration

BACKGROUND

Chloride channels (ClC) are involved in normal physiological processes and pathology of various diseases. Although it is recognized that suppression of ClC inhibits cell proliferation in different types of cells, the potential function of ClC in cell migration in ovarian cancer is still unclear. In this study, we investigated the effect of the ClC inhibitor, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), on cell migration in the human ovarian cancer cell line SKOV-3 as well as the related signaling pathway involved in this action.

METHODS

In this study, cell viability was measured using the MTT assay. Transwell migration method was used to study the effect of NPPB on serum-induced SKOV-3 cell migration. Also, Western blot was performed to detect the phosphorylation levels of ERK1/2 and AKT1 after treatment with NPPB.

RESULTS

Both NPPB and LY249002 significantly inhibited serum-induced SKOV-3 cell migration without alteration of cell viability. NPPB's inhibition of phosphorylation of AKT1 was time-dependent (p < 0.05). There was no significant effect on the phosphorylation of ERK1/2 after treatment with NPPB.

CONCLUSIONS

ClC plays an important role in ovarian cancer cell migration. NPPB inhibited-SKOV-3 cell migration could be via inactivation of AKT1.

Fluorescent oligonucleotides can serve as suitable alternatives to radiolabeled oligonucleotides

Prolonged exposure to radiation from radionuclei used in medical research can cause DNA damage and mutation, which lead to several diseases including cancer. Radioactivity-based experiments are expensive and associated with specialized training, dedication of instruments, approvals, and cleanup with potential hazardous waste. The objective of this study was to find an alternative to the use of radioactivity in medical research using nucleic acid chemistry. FITC-labeled oligonucleotides that contain wild-type (wt) and modified base (8-oxo-G) at the same position and their complementary unlabeled strand were synthesized. Purified DNA repair enzyme, OGG1, and nuclear lysates from MCF-7 breast cancer cells were incubated with double-stranded FITC-labeled wt and 8-oxo-G oligonucleotide to demonstrate the OGG1 incision assay. We found that FITC-coupled oligonucleotides do not impose a steric hindrance during duplex formation, and the fluorescence intensity of the oligonucleotide is comparable with the intensity of the radioactive oligonucleotide. Moreover, we have seen that the OGG1 incision assay can be performed using these fluorescence oligonucleotides, replacing conventional use of radiolabeled oligonucleotides in the assay. Although the use of fluorescent-labeled oligonucleotides was described in detail for incision assays, the technique can be applied to replace a broad range of experiments, where radioactive oligonucleotides are used, eliminating the hazardous consequences of radiation.

Role of p53 mutations, protein function and DNA damage for the radiosensitivity of human tumour cells

PURPOSE

The tumour suppressor protein p53 is considered to have an impact on the radiosensitivity of tumour cells. However, this concept does not easily translate to the tumour sensitivity in the clinics. The aim of the present study was to determine whether a functional or dysfunctional p53 is associated with a sensitive or resistant phenotype. It was further studied whether DNA damage might be an additive factor by which p53 has impact on cell survival.

MATERIALS AND METHODS

Nine human tumour cell lines were studied for p53 mutation by direct sequencing of exons 4-9. Regulation of p53 and p21(cip1/waf1) protein was assessed by immunoblotting and cell cycle effects by combining 5-bromodeoxyuridine incorporation and flow cytometry.

RESULTS AND CONCLUSION

Three strains (RT112, Du145, SCC4451) were found to have a missense-mutation in the core domain and one did not express p53 at all (HeLa), presumably due to HPV18 infection. Immunoblots of these cells showed neither a regulated p53 nor p21 expression. The cells did not arrest in G1 phase after X-irradiation but did arrest in G2/M. All cells expressing wild-type protein (LNCaP, T47D-B8, MCF-7 and sublines BB and Bus) showed an intact p53 and p21 regulation and a modest arrest in both G1 and G2/M. Thus, in contrast to other studies, all tumour cells investigated showed either a typical p53wt or mutant (mut) pattern. Protein function was compared with cell survival and DNA damage, as assessed previously. p53 wild-type cells were on average 1.3-times (n.s.) more radiosensitive than mutant cells, but there was a considerable overlap between both groups. Further, the 1.3-fold enhanced resistance of cells lacking wild-type p53 was paralleled by a 1.3-fold lower number of induced double-strand breaks. The results suggest that p53 could have impact on chromatin compaction and thus effect DNA damage induction and radiosensitivity of tumour cells.

Influence of the degree of acetylation on the enzymatic degradation and in vitro biological properties of trimethylated chitosans

Chitosan derivatives such as N,N,N-trimethylated chitosan (TMC) are currently being investigated for the delivery of drugs, vaccines and genes. However, the influence of the extent of N-acetylation of these polymers on their enzymatic degradability and biological properties is unknown. In this study, TMCs with a degree of acetylation (DA) ranging from 11 to 55% were synthesized by using a three-step method. First, chitosan was partially re-acetylated using acetic anhydride followed by quantitative dimethylation using formaldehyde and sodium borohydrate. Then, in presence of an excess amount of iodomethane, TMC was synthesized. The TMCs obtained by this method showed neither detectable O-methylation nor loss in acetyl groups ((1)H NMR) and a slight increase in molecular weight (GPC) with increasing degree of substitution, implying that no chain scission occurred during synthesis. The extent of lysozyme-catalyzed degradation of TMC, and that of its precursors chitosan and dimethyl chitosan, was highly dependent on the DA and polymers with the highest DA showed the largest decrease in molecular weight. On Caco-2 cells, TMCs with a high DA ( approximately 50%), a DQ of around 44% and with or without O-methylated groups, were not able to open tight junctions in the trans-epithelial electrical resistance (TEER) assay, in contrast with TMCs (both O-methylated and O-methyl free; concentration 2.5mg/ml) with a similar DQ but a lower DA which were able to reduce the TEER with 30 and 70%, respectively. Additionally, TMCs with a high DA ( approximately 50%) demonstrated no cell toxicity (MTT, LDH release) up to a concentration of 10mg/ml.

Lipid-conjugated telomerase template antagonists sensitize resistant HER2-positive breast cancer cells to trastuzumab

HER2 amplification in breast cancer is associated with a more aggressive disease, greater likelihood of recurrence, and decreased survival compared to women with HER2-negative breast cancer. Trastuzumab is a monoclonal antibody that inhibits HER2 activity, making this compound an important therapeutic option for patients with HER2-positive breast cancer. However, resistance to trastuzumab develops rapidly in a large number of breast cancer patients. The objective of this study was to determine whether GRN163L, a telomerase template antagonist currently in clinical trials for cancer treatment, can augment the effects of trastuzumab in breast cancer cells with HER2 amplification. GRN163L was effective in inhibiting telomerase activity and shortening telomeres in HER2-positive breast cancer cells. We show that GRN163L acts synergistically with trastuzumab in inhibiting HER2-positive breast cancer cell growth. More importantly, we show that GRN163L can restore the sensitivity of therapeutic-resistant breast cancer cells to trastuzumab. These findings implicate that telomerase template antagonists have potential use in the treatment of cancers that have developed resistance to traditional cancer therapy.

Artemether: A New Therapeutic Strategy in Experimental Rheumatoid Arthritis

The current research was designed to determine the effect of artemether in treatment of experimental rheumatoid arthritis. Collagen-induced arthritis was induced in Lewis rats. The intramusculary administration of artemether (ART) and intraperitoneally injection of methotrexate (MTX) were started on day 25 postimmunization and continued until final assessment on day 35. During this period, clinical examination was taken intermittently. The anticollagen type II antibody (CII Ab) and nitric oxide synthesis were measured. The paws and kness were then removed for histopathology and radiography assay. The biocompatibility of ART and MTX were assessed using fibrosarcoma cell line. Data showed that i.m. injection of ART to arthritic rats induced a significant reduction in paw edema. This beneficial effect was associated with a significant decrease in anti-CII antibody response compared with untreated rats. Histopathological assessment showed a reduced inflammatory cell infiltrate in joints of treated rats; tissue edema, and bone erosion in the paws were markedly reduced following ART therapy. Furthermore, our radiography results paralleled our histological findings. Cytotoxicity analysis of ART showed greater tolerability compared with MTX. Treatment with ART significantly diminished NO formation in treated rats compared with nontreated controls. Our data shed light on the therapeutic efficacy of artemether in experimental rheumatoid arthritis compared with a choice drug (methotrexate), and it may be offered as a second-line drug in treatment of rheumatoid arthritis.

Phase I and II enzyme characterization of two sources of HepG2 cell lines

1: The metabolism by HepG2 cell from two sources (M1, M2) of 12 substrates is reported: ethoxyresorufin, ethoxycoumarin, testosterone, tolbutamide, chlorzoxazone, dextromethorphan, phenacetin, midazolam, acetaminophen, hydroxycoumarin, p-nitrophenol and 1-chloro-2,4-dinitrobenzene (CDNB), and a pharmaceutical compound, EMD68843. 2: Activities varied markedly. Some were present in M1 (CYP1A, CYP2C9, CYP2E1) but absent in M2. M1 had a more complete set of Phase I enzymes than M2. CYP1A2, CYP2C9, CYP2D6, CYP2E1 and CYP3A activities were present at levels similar to human hepatocytes. Phase II metabolism differed between M1 and M2. M1 conjugated hydroxycoumarin and p-nitrophenol to glucuronides only, whereas M2 produced sulfates. Glutathione conjugation of CDNB metabolism was 10-fold higher in M1 than in M2, but was still much lower than in human hepatocytes. CYP2E, CYP2C, CYP2B6 and CYP3A (but not CYP1A, glucuronyl S-transferase or S-transferase) were inducible in M1. Metabolites of EMD68843, produced by induced (but not uninduced) M1 were the same as those produced in human hepatocytes. 3: In conclusion, HepG2 cells have both Phase I and II enzymes, which activities and at what levels depend on the source and culture conditions. Therefore, HepG2 cells routinely used in in vitro assays should be characterized for their drug-metabolizing capabilities before any results can be fully interpreted.

[Establishment of a cellular model with human NADH-cytochrome b5 reductase deficiency via RNA interference]

OBJECTIVE

To establish a cell line with human NADH-cytochrome b5 reductase (b5R) deficiency via RNA interference (RNAi).

METHODS

Two siRNA expressing vectors targeting the b5R mRNA were designed and constructed. Hepatocellular carcinoma BEL-7402 cells were transiently transfected with the two recombinants by lipofectamine (TM) 2000, and semi-quantitative RT-PCR was carried out to analyze the suppression of b5R mRNA; BEL-7402 cells stably transfected with the two siRNA expressing vectors were selected in the media with G418. By analyses of the mRNA, enzymatic activity and protein level of b5R, several cell clones with deficiency of b5R were established. The cell growth curve of BEL-7402 cells with b5R deficiency was detected by MTT assay.

RESULTS

Two siRNA expressing vectors targeting b5R mRNA were obtained, namely pSib5R-1 and pSib5R-2. When BEL-7402 cells were transfected transiently with pSib5R-2, the expression of b5R mRNA was significantly suppressed with a suppression ratio of 68.3%, indicating that pSib5R-2 could trigger the degradation of b5R mRNA effectively. Eighteen clones stably integrated exogenous plasmids were obtained. In two clones from pSib5R-2 transfection, the expression of b5R mRNA was suppressed by up to 48.2% and 56.2%, and the enzymatic activity was inhibited by up to 54.6% and 63.5%, respectively. The protein levels also decreased significantly. The defect of b5R did not change the cell growth rate.

CONCLUSION

The expression of b5R in BEL-7402 could be suppressed by vector-based RNA interference effectively. We established a cellular model with defect of b5R successfully, which can be used as a tool in investigation of the biological function of b5R and molecular mechanism of type II recessive congenital methemoglobinemia.

Epigenetic and genetic mechanisms contribute to telomerase inhibition by EGCG

The ends of human chromosomes are protected from the degradation associated with cell division by 15-20 kb long segments of hexameric repeats of 5'-TTAGGG-3' termed telomeres. In normal cells telomeres lose up to 300 bp of DNA per cell division that ultimately leads to senescence; however, most cancer cells bypass this lifespan restriction through the expression of telomerase. hTERT, the catalytic subunit essential for the proper function of telomerase, has been shown to be expressed in approximately 90% of all cancers. In this study we investigated the hTERT inhibiting effects of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea catechins, in MCF-7 breast cancers cells and HL60 promyelocytic leukemia cells. Exposure to EGCG reduced cellular proliferation and induced apoptosis in both MCF-7 and HL60 cells in vitro, although hTERT mRNA expression was decreased only in MCF-7 cells when treated with EGCG. Furthermore, down-regulation of hTERT gene expression in MCF-7 cells appeared to be largely due to epigenetic alterations. Treatment of MCF-7 cells with EGCG resulted in a time-dependent decrease in hTERT promoter methylation and ablated histone H3 Lys9 acetylation. In conjunction with demethylation, further analysis showed an increase in hTERT repressor E2F-1 binding at the promoter. From these findings, we propose that EGCG is effective in causing cell death in both MCF-7 and HL60 cancer cell lines and may work through different pathways involving both anti-oxidant effects and epigenetic modulation.

Activation of aminoflavone (NSC 686288) by a sulfotransferase is required for the antiproliferative effect of the drug and for induction of histone gamma-H2AX

Aminoflavone (AF) is entering clinical trials. We recently reported that AF induces DNA-protein cross-links (DPC) and gamma-H2AX in MCF-7 human breast cancer cells. To elucidate the mechanism of action of AF and provide biomarkers indicative of AF activity, we correlated AF activity profile (GI(50)) with gene expression patterns in the NCI-60 cell lines. Sulfotransferases (SULT) showed the highest positive correlation coefficients among approximately 14,000 probe sets analyzed (r = 0.537, P < 0.001). Stable transfection of SULT1A1 into AF-resistant MDA-MB-231 cells sensitized these cells to AF. AF produced DPCs, gamma-H2AX foci, and S-phase arrest in the SULT1A1-transfected but not in the parent MDA-MB-231 cells. Conversely, cells in which SULT1A1 was knocked down by small interfering RNA failed to induce gamma-H2AX. Inhibition of SULTs and cytochrome P450 (CYP) enzymes by natural flavonoids blocked the antiproliferative activity of AF and the formation of AF-DNA adducts. AF also induces SULT1A1 and CYP expression in MCF-7 cells, suggesting the existence of an aryl hydrocarbon receptor-mediated positive feedback for AF activation by CYP and SULT1A1. Metabolism studies showed that AF can be oxidized by CYP at two amino groups to form N-hydroxyl metabolites that are substrates for bioactivation by SULTs. We propose that both N-sulfoxy-groups can be further converted to nitrenium ions that form adducts with DNA and proteins. The results reported here show the importance of SULT1A1 and CYP for AF activation and anticancer activity. They also suggest using SULT1A1 and gamma-H2AX as biomarkers for prediction of AF activity during patient selection and monitoring of clinical trials.

Increased wild-type p53-induced phosphatase 1 (Wip1 or PPM1D) expression correlated with downregulation of checkpoint kinase 2 in human gastric carcinoma

Phosphorylation of checkpoint kinase 2 (Chk2) at Thr68 (pChk2) induced by DNA double-strand breaks is required for inhibition of cell cycle progression in the G(2) phase. The purpose of the present paper was to investigate the expression of wild-type p53-induced phosphatase 1 (Wip1 or PPM1D), a negative regulator of Chk2, to better understand its role in human gastric cancer. In non-neoplastic gastric mucosa, most epithelial cells exhibited Wip1-positive and pChk2-negative immunoreactivity, whereas an inverse pattern of protein expression was detected at the surface of the foveolar epithelium. In tumor tissues, 74% of 53 gastric cancers had intense Wip1 immunoreactivity and close correlation with both tumor size (P = 0.0497) and Chk2 dephosphorylation (P = 0.0213). In MKN-74 gastric cancer cells, ionizing radiation (IR)-induced Wip1 upregulation was detected at protein levels, but the Chk2-mediated cell cycle regulatory mechanism was disrupted. In addition, protease inhibitor Z-Leu-Leu-Leu (ZLLL) effectively upregulated Wip1 levels in the presence or absence of IR, suggesting that Wip1 expression can be modulated post-transcriptionally. Understanding the Wip1-mediated signaling pathway in gastric cancer may provide useful information for the development of new chemo- and radiotherapies.

Characterization of 3 oral squamous cell carcinoma cell lines with different invasion and/or metastatic potentials

PURPOSE

Proteolytic enzymes may confer specific types of invasion and metastasis in patients with oral squamous cell carcinoma (OSCC). The purpose of this study was to determine if OSCC that invades adjacent bone has different proteolytic enzyme expression profiles than OSCC that metastasizes to lymph nodes or distant organs. Three OSCC cell lines, BHY, HSC-3, and HN, with known behavior regarding bone invasion and lymph node and distant metastatic profiles, were evaluated. The characteristics of a control, human normal nasal epithelial cell line (HNEC), and BHY, HSC-3 and HN were evaluated with regard to their expression of the matrix metalloproteinases and cathepsins.

MATERIALS AND METHODS

Expressions of proteolytic enzymes including matrix metalloproteinase, MMP-1, MMP-2, MMP-3, MMP-9, extracellular matrix metalloproteinase inducer (EMMPRIN), cathepsin B, and cathepsin L were compared using immunocytochemistry and flow cytometry in 3 OSCC cell lines and HNEC. The cell morphologies of these 4 cell lines were compared using transmission electron microscopy (TEM).

RESULTS

All OSCC cell lines showed higher expression of all the proteolytic proteins when compared with HNEC, except the HSC-3 cell line showed no difference in the expression of MMP-9. There was no detectable difference at the expression level of MMP-1, MMP-2, MMP-3, cathepsin B, and cathepsin L in any of the OSCC cell lines. However, MMP-9 and EMMPRIN levels were higher in the BHY cell line. According to electron microscopy, the cells of the HSC-3 cell line were the smallest and least differentiated among the 3 OSCC cell lines. The BHY cell line was the most highly differentiated showing interdigitation and numerous cell junctions.

CONCLUSIONS

MMPs play an important role in the invasion and metastasis of oral cancer. MMP-9 might play a more important role than MMP-2 during invasion. Increased expression of MMP-1, MMP-9, and EMMPRIN proteins might be involved in invasion of OSCC to adjacent bone, as they are necessary for the collagen matrix degradation. Increased expression of MMP-3, cathepsin B and L in OSCC might be associated with both invasion and a high incidence of metastasis.

Lipid peroxidation, cyclooxygenase enzyme and tumor cell proliferation inhibitory compounds in Cornus kousa fruits

The genus Cornus is well known for its medicinal properties. Bioassay-guided isolation and characterization of C. kousa fruits afforded kaempferol 3-O-rhamnoside (1), myricetin 3-O-rhamnoside (2), kaempferol 3-O-glucoside (3), cornin (4) and stenophyllin (5) in addition to ursolic acid and beta-sitosterol. These compounds are isolated for the first time from C. kousa. Compounds 1-5 inhibited Fe(2+) catalyzed lipid peroxidation by 63%, 57%, 61%, 53%, and 51%, at 23, 22, 23, 129, and 108 microM, respectively. Similarly, they inhibited COX-1 and -2 enzymes activities by 24% and 47%, 40% and 37%, 20% and 37%, 52% and 63%, and 48% and 55% respectively, at 231, 215, 226, 258, and 217 microM, respectively. At 129 microM, compound 4 displayed growth inhibition of HCT-116 (colon), MCF-7 (breast), NCI-H460 (lung), SF-268 (central nervous system CNS), and AGS (stomach) human tumor cell lines by 31%, 29%, 40%, 9%, and 28%, respectively. Similarly, compound 5 inhibited the growth of colon, breast, lung, CNS, and stomach tumor cell lines by 0%, 27%, 35%, 16%, and 27%, respectively, at 108 microM.

Dissociation of gemcitabine sensitivity and protein kinase B signaling in pancreatic ductal adenocarcinoma models

OBJECTIVE

To understand the impact of protein kinase B (PKB; Akt) signaling on growth and protection from apoptosis in pancreatic ductal adenocarcinoma models demonstrating differences in PKB activity.

METHODS

Gemcitabine sensitivity was investigated in a panel of cell lines, characterized by differences in levels of activated PKB. Suppression of PKB activity was achieved with an inhibitor of phosphatidylinositol 3-kinase (wortmannin) and silencing RNA.

RESULTS

Enhanced gemcitabine (2',2'-difluoro-2'-deoxycytidine)-induced cytotoxicity in vitro was achieved with suppression of high PKB activity with wortmannin in BxPC-3, PK-1, and PK-8 cells and silencing RNA targeted to total PKB, rather than PKBbeta, in PANC-1 cells. Opposite to gemcitabine sensitivity levels in vitro, the growth of PANC-1 xenografts was inhibited with gemcitabine treatment, whereas BxPC-3 became drug resistant. Monolayer cell cultures reestablished from solid tumors behaved similarly to original cultures, suggesting that the tumor microenvironment has a critical role in determining drug sensitivity. A comparison of transcript profiles of the models indicated that PKB signaling might be modulated by a number of pathways responsive to the tumor hypoxia microenvironment.

CONCLUSIONS

These results suggested that gemcitabine efficacy involving the PKB pathway depends on PKB activity, its mechanisms of enhanced activity, as well as its function in a signaling network.

DNA-dependent protein kinase activity and radiosensitivity of nasopharyngeal carcinoma cell lines CNE1/CNE2

The present study investigated the relationship between DNA-dependent protein kinase (DNA-PK) and radiosensitivity of nasopharyngeal carcinoma (NPC) cell lines. The dose-survival relationship for NPC cell lines, CNE1 and CNE2, was analyzed using clonogenic formation assay, the activity of DNA-PK of the two cell lines was measured using the Signa TECT DNA-PK assay kit, and the localization and expression of Kus (a heterodimer) and DNA-PKcs protein in CNE1 and CNE2 before irradiation and 15 min, 1 h, 6 h, 12 h, 24 h after 4 Gy irradiation were analyzed by immunofluorescence, laser scanning confocal microscope (LSCM) and Western blot. The results showed that the surviving fraction of CNE1 was higher than that of CNE2 at each dose. The DNA-PK activity of CNE1 was also significantly higher than that of CNE2 before and after irradiation (P<0.05), while the expression of total Ku70/Ku80 in CNE1 and CNE2 had no significant difference. Increasing translocation of Ku70 and Ku80 from the cytoplasm to the nuclei in the two cell lines was observed with increase of irradiation time as detected by Western blot, and the immunofluorescence of the DNA-PK complex subunits showed greater nuclear translocation in CNE1 than CNE2 after irradiation. The results suggest that the relatively higher radio-resistance of CNE1 correlates with the higher activity of DNA-PK as compared to that of more radiosensitive CNE2 (or lower radio-resistance) before and after irradiation. Thus, DNA-PK activity may be a useful predictor of radiosensitivity of NPC.

Cloning and characterization of a human BCR/ABL-positive cell line, K562/RR, resistant to the farnesyltransferase inhibition by tipifarnib

OBJECTIVE

Results of previous studies have suggested that tipifarnib (Zarnestra), a farnesyltransferase inhibitor, is useful for treating various hematological disorders, including chronic myeloid leukemia. However, acquisition of resistance may be a problem for patients being treated with tipifarnib.

METHODS

We generated a tipifarnib-resistant BCR/ABL-positive cell line, K562/RR, and examined its characteristics.

RESULTS

While levels of cleaved caspase-3, cleaved caspase-7, cleaved caspase-9, and cleaved poly (ADP-ribose) polymerase were significantly increased in K562 cells, the levels were not changed in K562/RR cells with tipifarnib treatment, indicating that induction of apoptosis signaling mediated by tipifarnib is much less in K562/RR cells than in K562 cells. In addition, tipifarnib-mediated induction of cell-cycle blockage was abrogated in K562/RR cells. No mutation of farnesyltransferase alpha and beta genes was found and the level of unprocessed HDJ-2, which is a substrate of farnesyltransferase, was increased by tipifarnib treatment in K562/RR cells, suggesting that tipifarnib inhibits protein farnesylation in K562/RR cells in the same manner as in K562 cells and that mechanisms independent of farnesyltransferase activity are involved in the acquisition of resistance to tipifarnib in these cells. By DNA microarray analyses using a cDNA microarray comprising 25,000 genes, we identified 5 genes with higher expression levels in K562/RR cells than in K562 cells. These genes include beta-globin, calcium channel Caveolin 2, and FEN1, which is involved in DNA replication and repair, and CUGBP2, which may affect expression of cyclooxygenase 2.

CONCLUSION

The results of this study provide useful information for clarification of the mechanisms of resistance to tipifarnib.

The potential for phospholipase D as a new therapeutic target

Mammalian phospholipase D (PLD), a signal transduction-activated enzyme, hydrolyzes phosphatidylcholine to generate the lipid second messenger phosphatidic acid (PA) and choline. Genetic and pharmacological methods have implicated PLD and its product PA in a wide variety of cellular processes including vesicle trafficking, receptor signaling, cell proliferation and survival. Dysregulation of these cell biologic processes occurs in a diverse range of illnesses including cancer. This review summarizes PLD regulation and function and highlights its potential as a therapeutic target in disease settings.

Potential misidentification of cyclooxygenase-2 by Western blot analysis and prevention through the inclusion of appropriate controls

Cyclooxygenase (COX)-2 plays an important role in the development of cancer and has been recognized as a potential therapeutic target. Because nonsteroidal anti-inflammatory drugs (NSAIDs) are able to inhibit the activity of this enzyme, the potential efficacy of such drugs for purposes of cancer prevention or therapy is an area of intense research. Therefore, it is of critical importance to unequivocally determine the expression levels of COX-2 protein in tumor cells. In this regard, there are several conflicting reports in the literature where the same type of tumor cell lines were reported as COX-2 positive and as COX-2 negative. We found that during Western blot analysis of COX-2 positive and COX-2 negative cells, different antibodies to COX-2 protein are able to generate strong signals, which are false-positives and can be confused with COX-2. Thus, we believe that some of the conflicting reports on COX-2 expression in tumor cell lines could be the result of improper interpretation of the Western blot signals. Here, we present some of these pitfalls and suggest the inclusion of appropriate controls to unequivocally identify COX-2 protein levels.

Effects of herbal medicinal products and food supplements on induction of CYP1A2, CYP3A4 and MDR1 in the human colon carcinoma cell line LS180

A selection of popular herbal medicinal products and food supplements were analysed for their potential to modulate the expression of the cytochrome P450 enzymes CYP1A2 and CYP3A4 and the transporter protein MDR1. A total of 31 products were analysed. Nine of the products have been approved by the Medical Products Agency (MPA) in Sweden and are marketed as herbal medicinal products. Twenty-two of the products have not been assessed by the MPA and are marketed as food supplements. LS180 cells were exposed to extracts from the different herbal products and real-time quantitative polymerase chain reaction, RT-QPCR, was subsequently used to analyse the relative mRNA levels of CYP1A2, CYP3A4 or MDR1 in treated and non-treated cells. Our results show that 17 of 31 products tested induced a two-fold expression or more for at least one of the genes analysed. Four products, of which a ginger-supplement was the most potent, induced all three genes.

Establishment of an in vivo meningioma model with human telomerase reverse transcriptase

OBJECTIVE

The lack of meningioma models has hindered research on the pathogenesis and treatment of this commonly diagnosed primary brain tumor. Animal models of meningioma have been difficult to develop, especially those derived from Grade I tumors, which display very slow growth rates, senesce at early passages, and infrequently survive as explants in vivo. In this study, the authors report the establishment of two benign immortalized meningioma cell lines, Me10T and Me3TSC, that can serve as useful models of human meningioma.

METHODS

Tissue specimens obtained at the time of surgery were cultured in vitro and transduced with human telomerase reverse transcriptase/SV40 large T antigen to establish long-term cell lines. The telomeric activity, growth kinetics, immunophenotype, and karyotyping of the cell lines were investigated. The growth inhibitory effects of the antitumor therapies, hydroxyurea and sodium butyrate, on these cell lines were determined. In addition, immortalized cell lines were implanted subdurally into mice to confirm their ability to form tumors.

RESULTS

Two immortalized benign meningioma cell lines, Me10T and Me3TSC, transduced with catalytic subunit human telomerase reverse transcriptase alone or human telomerase reverse transcriptase and SV40 large T antigen, were established. The meningeal phenotype of the established cell cultures and orthotopic xenografts was confirmed by immunostaining. After subdural injection into athymic nude mice, both cell lines formed identifiable tumors with histological features and immunostaining patterns of human meningioma.

CONCLUSION

The Me3TSC and Me10T cell lines can serve as useful model systems for biological studies and the evaluation of novel therapies on meningioma.

Nonreceptor tyrosine kinases in prostate cancer

BACKGROUND

Carcinoma of the prostate (CaP) is the most commonly diagnosed cancer in men in the United States. Signal transduction molecules such as tyrosine kinases play important roles in CaP. Src, a nonreceptor tyrosine kinase (NRTK) and the first proto-oncogene discovered is shown to participate in processes such as cell proliferation and migration in CaP. Underscoring NRTK's and, specifically, Src's importance in cancer is the recent approval by the US Food and Drug Administration of dasatinib, the first commercial Src inhibitor for clinical use in chronic myelogenous leukemia (CML). In this review we will focus on NRTKs and their roles in the biology of CaP.

MATERIALS AND METHODS

Publicly available literature from PubMed regarding the topic of members of NRTKs in CaP was searched and reviewed.

RESULTS

Src, FAK, JaK1/2, and ETK are involved in processes indispensable to the biology of CaP: cell growth, migration, invasion, angiogenesis, and apoptosis.

CONCLUSIONS

Src emerges as a common signaling and regulatory molecule in multiple biological processes in CaP. Src's relative importance in particular stages of CaP, however, required further definition. Continued investigation of NRTKs will increase our understanding of their biological function and potential role as new therapeutic targets.

Ethanolic extracts of black cohosh (Actaea racemosa) inhibit growth and oestradiol synthesis from oestrone sulphate in breast cancer cells

Extracts of black cohosh (Actaea racemosa) and soy are used as 'natural' alternatives to conventional hormone replacement therapy (HRT) and there is some evidence that soy may protect against breast cancer by inhibiting the production of active oestrogens. This study compares the action of ethanolic extracts of black cohosh (BCE) and genistein on growth and enzyme activity in MCF-7 and MDA-MB-123 breast cancer cells. BCE inhibited growth at the two highest doses tested, i.e. 50 and 100 microg/ml, whilst genistein stimulated growth in the oestrogen receptor positive (ER(+)) MCF-7 cells, but at high doses it inhibited growth in both cell lines. BCE did not affect the conversion of androstenedione to oestradiol and only the highest doses (50 and 100 microg/ml) significantly inhibited the conversion of oestrone to oestradiol in MDA cells. In contrast, BCE induced a dose-dependent inhibition of the conversion of oestrone sulphate to oestradiol in both cell lines, whilst in human granulosa lutein (GL) cells enzyme activity was only inhibited at the highest dose of BCE. Genistein had no significant effect on enzyme activity in breast cancer cells and like BCE only the highest doses (10 and 50 microM) inhibited enzyme activity in human GL cells. In vivo genistein may have growth stimulatory effects on breast tissue but BCE not only inhibits growth but inhibits the conversion of oestrone sulphate to active oestradiol, considered by some, to be the preferred pathway of oestradiol synthesis in breast tissue.

Different target range and cytotoxic specificity of adaphostin and 17-allylamino-17-demethoxygeldanamycin in imatinib-resistant and sensitive cell lines

Imatinib mesylate is a selective inhibitor of the oncogenic tyrosine kinase, Bcr-Abl, and is widely used as a first-line treatment for chronic myeloid leukaemia (CML). Prolonged monotherapy is frequently associated with patients becoming refractory to imatinib. Therefore, there is considerable interest in small molecule inhibitors which may be used either as replacements or as adjuncts to existing imatinib therapy. For this purpose, it is most likely that drugs which do not share imatinib's mechanism of action will be most valuable. We compared two such compounds with different modes of action, adaphostin and 17-allylamino-17-demethoxygeldanamycin (17-AAG), for their cytotoxic effect and ability to induce the downregulation of cellular proteins in a murine haemopoietic cell line transformed with human p210(Bcr-Abl), and two subclones resistant to imatinib owing to an Abl-kinase domain mutation (E255K) or amplification of the BCR-ABL gene, respectively. We found that, whereas 17-AAG selectively killed Bcr-Abl-positive cells and inhibited proteins dependent on heat-shock protein 90 for their stability (p210(Bcr-Abl) and Akt), adaphostin induced the downregulation of multiple cell-signalling proteins (p210(Bcr-Abl), Akt, Bcr, Abl and STAT5a) and was cytotoxic to both Bcr-Abl-positive and -negative cells. We suggest that both compounds may prove useful in the treatment of CML but caution that undesirable side-effects may result from the inhibition of multiple cell signalling proteins.

Comparative evaluation of the treatment efficacy of suberoylanilide hydroxamic acid (SAHA) and paclitaxel in ovarian cancer cell lines and primary ovarian cancer cells from patients

Background

In most patients with ovarian cancer, diagnosis occurs after the tumour has disseminated beyond the ovaries. In these cases, post-surgical taxane/platinum combination chemotherapy is the "gold standard". However, most of the patients experience disease relapse and eventually die due to the emergence of chemotherapy resistance. Histone deacetylase inhibitors are novel anticancer agents that hold promise to improve patient outcome.

Methods

We compared a prototypic histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), and paclitaxel for their treatment efficacy in ovarian cancer cell lines and in primary patient-derived ovarian cancer cells. The primary cancer cells were isolated from malignant ascites collected from five patients with stage III ovarian carcinomas. Cytotoxic activities were evaluated by Alamar Blue assay and by caspase-3 activation. The ability of SAHA to kill drug-resistant 2780AD cells was also assessed.

Results

By employing the cell lines OVCAR-3, SK-OV-3, and A2780, we established SAHA at concentrations of 1 to 20 μM to be as efficient in inducing cell death as paclitaxel at concentrations of 3 to 300 nM. Consequently, we treated the patient-derived cancer cells with these doses of the drugs. All five isolates were sensitive to SAHA, with cell killing ranging from 21% to 63% after a 72-h exposure to 20 μM SAHA, while four of them were resistant to paclitaxel (i.e., <10% cell death at 300 nM paclitaxel for 72 hours). Likewise, treatment with SAHA led to an increase in caspase-3 activity in all five isolates, whereas treatment with paclitaxel had no effect on caspase-3 activity in three of them. 2780AD cells were responsive to SAHA but resistant to paclitaxel.

Conclusion

These ex vivo findings raise the possibility that SAHA may prove effective in the treatment of paclitaxel-resistant ovarian cancer in vivo.

Implications of increased tissue transglutaminase (TG2) expression in drug-resistant breast cancer (MCF-7) cells

The development of resistance to chemotherapeutic drugs is a major obstacle to the successful treatment of breast cancer. Ways to block or overcome this resistance are objects of intense research. We have previously shown that cancer cells selected for resistance against chemotherapeutic drugs or isolated from metastatic tumor sites have high levels of a calcium-dependent protein crosslinking enzyme, tissue transglutaminase (TG2) but no direct link between TG2 and resistance was established. As TG2 can associate with the beta members of the integrin family of proteins, we hypothesized that TG2 promotes cell survival signaling pathways by activating integrins on the surface of these cells. To test this hypothesis, we studied the expression of TG2 and its interaction with various integrins in drug-resistant MCF-7 breast cancer cells. TG2 closely associated with beta1 and beta5 integrins on the surface of drug-resistant MCF-7 (MCF-7/Dox and MCF-7/RT) cells. The incubation of TG2-expressing drug-resistant MCF-7 cells on fibronectin (Fn)-coated surfaces strongly activated focal adhesion kinase, an event that leads to the activation of several downstream signaling pathways and, in turn, can confer apoptosis-resistant phenotype to cancer cells. The role of TG2 in Fn-mediated cell attachment, cell growth, and cell survival functions was further analysed by small interfering RNA (siRNA) approach. Inhibition of TG2 by siRNA-inhibited Fn-mediated cell attachment and cell survival functions in drug-resistant MCF-7 cells. We conclude that the expression of TG2 in breast cancer cells contributes to the development of the drug-resistance phenotype by promoting interaction between integrins and Fn.

MAPKAPK2 and HSP27 are downstream effectors of p38 MAP kinase-mediated matrix metalloproteinase type 2 activation and cell invasion in human prostate cancer

Although cell invasion is a necessary early step in cancer metastasis, its regulation is not well understood. We have previously shown, in human prostate cancer, that transforming growth factor beta (TGFbeta)-mediated increases in cell invasion are dependent upon activation of the serine/threonine kinase, p38 MAP kinase. In the current study, downstream effectors of p38 MAP kinase were sought by first screening for proteins phosphorylated after TGFbeta treatment, only in the absence of chemical inhibitors of p38 MAP kinase. This led us to investigate mitogen-activated protein kinase-activated protein kinase 2 (MAPKAPK2), a known substrate of p38 MAP kinase, as well as heat-shock protein 27 (HSP27), a known substrate of MAPKAPK2, in both PC3 and PC3-M human prostate cells. After transient transfection, wild-type MAPKAPK2 and HSP27 both increased TGFbeta-mediated matrix metalloproteinase type 2 (MMP-2) activity, as well as cell invasion, which in turn was inhibited by SB203580, an inhibitor of p38 MAP kinase. Conversely, dominant-negative MAPKAPK2 blocked phosphorylation of HSP27, whereas dominant-negative MAPKAPK2 or mutant, non-phosphorylateable, HSP27 each blocked TGFbeta-mediated increases in MMP-2, as well as cell invasion. Similarly, knock down of MAPKAPK2, HSP27 or both together, by siRNA, also blocked TGFbeta-mediated cell invasion. This study demonstrates that both MAPKAPK2 and HSP27 are necessary for TGFbeta-mediated increases in MMP-2 and cell invasion in human prostate cancer.

Spatial and temporal heparanase expression in colon mucosa throughout the adenoma-carcinoma sequence

Heparanase is a mammalian endo-beta-D-glucuronidase that cleaves heparan sulfate side chains at a limited number of sites. Such enzymatic activity is thought to participate in degradation and remodeling of the extracellular matrix and to facilitate cell invasion associated with tumor metastasis, angiogenesis and inflammation. Traditionally, heparanase activity was well correlated with the metastatic potential of a large number of tumor-derived cell types. More recently, heparanase upregulation has been documented in an increasing number of primary human tumors, correlating with poor postoperative survival and increased tumor vascularity. Here, we employed anti-heparanase 733 polyclonal antibody that preferentially recognizes the 50 kDa active heparanase subunit over the 65 kDa proenzyme, as well as anti-heparanase 92.4 monoclonal antibody that recognizes both the latent and the active enzyme, to follow heparanase expression, processing and localization throughout the adenoma-carcinoma transition of the colon epithelium. Normal (nondysplastic) mucosa of the large bowel near epithelial neoplasms, as well as areas of mild dysplasia in adenomas, exhibited a strong reactivity with antibody 733 that became even stronger in foci of moderate dysplasia. Interestingly, although reactivity with antibody 733 was markedly reduced in severe dysplasia and in colorectal carcinoma, response to antibody 92.4 exhibited the opposite trend and staining intensities increased in parallel with tumor stage, the highest being in carcinoma cells. Involvement of latent heparanase (detected by 92.4, but not by 733 antibody) in tumor progression was suggested by activation of the Akt/PKB signal transduction pathway upon heparanase overexpression or exogenous addition to HT29 human colon carcinoma cells. These results suggest that heparanase expression is induced during colon carcinogenesis, and that its processing, conformation and localization are tightly regulated during the course of colon adenoma-carcinoma progression.

Critical roles of AMP-activated protein kinase in the carcinogenic metal-induced expression of VEGF and HIF-1 proteins in DU145 prostate carcinoma

Epidemiological and experimental animal data indicate that exposure to both metals and metalloid species exacerbates the risk of human diseases, particularly cancers. Vascular endothelial growth factor (VEGF), which performs a primary function in both tumor progression and angiogenesis, is up-regulated due to exposure to an array of carcinogenic metals, but the mechanisms responsible for the metal activation remain somewhat poorly understood. Recently, we demonstrated that AMP-activated protein kinase (AMPK), which acts as an energy sensor, providing metabolic adaptation effects under ATP-deprived conditions, is critical for the expression of VEGF under oxygen- and glucose-deprived conditions. As carcinogenic metals are potent VEGF expression inducers, we hypothesized that AMPK would also play a crucial role in metal-induced VEGF expression. Here, we present evidence that carcinogenic metals such as arsenite, vanadate, and cobalt, induce AMPK activation and VEGF expression via several different mechanisms, and that AMPK is able to regulate the expression of VEGF mRNA in a hypoxia-inducible factor-1-dependent or -independent manner, depending on the metal applied. We also attempted to characterize the relevant signal transduction pathways in metal-induced VEGF expression and AMPK activation, as well as the role of reactive oxygen species within this context. Overall, our data suggest that AMPK is a critical regulatory component in metal-induced VEGF expression, which further implies its intrinsic involvement in metal-induced carcinogenesis.

SULF1 inhibits tumor growth and potentiates the effects of histone deacetylase inhibitors in hepatocellular carcinoma

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is the third most common cause of cancer death worldwide. Improved treatments for advanced HCC are urgently needed. The recently identified human sulfatase 1 enzyme (SULF1) desulfates cell surface heparan sulfate glycosaminoglycans and down-regulates cell growth signaling in HCC cells in vitro. While investigating the epigenetic regulation of SULF1, we discovered that histone H4 acetylation is up-regulated by SULF1 in HCC cells. Histone deacetylase (HDAC) inhibitors reprogram cellular gene expression through the acetylation of nucleosomal histones and promote cell growth arrest and apoptosis. Hence, they are a promising modality for cancer treatment.

METHODS

To explore the interaction between SULF1 expression and HDAC inhibitor action, we examined the effects of SULF1 expression on HCC cells and xenografts treated with HDAC inhibitors.

RESULTS

(1) Forced expression of SULF1 significantly delayed the growth of Huh7 and Hep3B xenografts in nude mice in vivo. (2) SULF1 increased histone H4 acetylation by modulation of cellular HDAC and histone acetyltransferase activities. (3) SULF1 enhanced the induction of apoptosis by the HDAC inhibitors apicidin and scriptaid. (4) SULF1 enhanced the inhibition of tumor growth, migration, and angiogenesis by HDAC inhibitors. We also demonstrate that knockdown of SULF1 with shRNA constructs up-regulates phosphorylation of AKT and Erk and attenuates apicidin-induced apoptosis. The interaction between SULF1 and apicidin was confirmed in vivo in Huh7 and Hep3B xenografts.

CONCLUSIONS

These results show that SULF1 promotes histone H4 acetylation, potentiates the effects of HDAC inhibitors, and inhibits HCC tumorigenesis.

Mediterranean diet, olive oil and cancer

Olive oil is an integral ingredient of the "Mediterranean diet" and accumulating evidence suggests that it may have a potential role in lowering the risk of several types of cancers. The mechanisms by which the cancer-preventing effects of olive oil can be performed, however, are not known. We recently hypothesized that a novel molecular explanation concerning the anti-cancer actions of olive oil may relate to the ability of its monounsaturated fatty acid (MUFA) oleic acid (OA; 18:1n-9) to specifically regulate cancer-related oncogenes. Supporting our hypothesis, exogenous supplementation of cultured breast cancer cells with physiological concentrations of OA was found to suppress the overexpression of HER2 (Her-2/neu, erbB-2), a well-characterized oncogene playing a key role in the etiology, progression and response to chemotherapy and endocrine therapy in approximately 20% of breast carcinomas. OA treatment was also found to synergistically enhance the efficacy of trastuzumab, a humanized monoclonal antibody binding with high affinity to the ectodomain (ECD) of the Her2-coded p185(HER2) oncoprotein. Moreover, OA exposure significantly diminished the proteolytic cleavage of the ECD of HER2 and, consequently, its activation status, a crucial molecular event that determines both the aggressive behavior and the response to trastuzumab of Her2-overexpressing breast carcinomas. Our most recent findings further reveal that OA exposure may suppresses HER2 at the transcriptional level by up-regulating the expression of the Ets protein PEA3 -a DNA-binding protein that specifically blocks HER2 promoter activity- in breast, ovarian and stomach cancer cell lines. This anti-HER2 property of OA offers a previously unrecognized molecular mechanism by which olive oil may regulate the malignant behavior of cancer cells. From a clinical perspective, it could provide an effective means of influencing the outcome of Her-2/neu-overexpressing human carcinomas with poor prognosis. Indeed, OA-induced transcriptional repression of HER2 oncogene may represent a novel genomic explanation linking "Mediterranean diet", olive oil and cancer as it seems to equally operate in various types of Her-2/neu-related carcinomas.

7-Bromoindirubin-3'-oxime induces caspase-independent cell death

Indirubin, an isomer of indigo, is a reported inhibitor of cyclin-dependent kinases (CDKs) and glycogen synthase kinase-3 (GSK-3) as well as an agonist of the aryl hydrocarbon receptor (AhR). Indirubin is the active ingredient of a traditional Chinese medicinal recipe used against chronic myelocytic leukemia. Numerous indirubin analogs have been synthesized to optimize this promising kinase inhibitor scaffold. We report here on the cellular effects of 7-bromoindirubin-3'-oxime (7BIO). In contrast to its 5-bromo- and 6-bromo- isomers, and to indirubin-3'-oxime, 7BIO has only a marginal inhibitory activity towards CDKs and GSK-3. Unexpectedly, 7BIO triggers a rapid cell death process distinct from apoptosis. 7-Bromoindirubin-3'-oxime induces the appearance of large pycnotic nuclei, without classical features of apoptosis such as chromatin condensation and nuclear fragmentation. 7-Bromoindirubin-3'-oxime-induced cell death is not accompanied by cytochrome c release neither by any measurable effector caspase activation. Furthermore, the death process is not altered either by the presence of Q-VD-OPh, a broad-spectrum caspase inhibitor, or the overexpression of Bcl-2 and Bcl-XL proteins. Neither AhR nor p53 is required during 7BIO-induced cell death. Thus, in contrast to previously described indirubins, 7BIO triggers the activation of non-apoptotic cell death, possibly through necroptosis or autophagy. Although their molecular targets remain to be identified, 7-substituted indirubins may constitute a new class of potential antitumor compounds that would retain their activity in cells refractory to apoptosis.

DEP-1 protein tyrosine phosphatase inhibits proliferation and migration of colon carcinoma cells and is upregulated by protective nutrients

The transmembrane protein-tyrosine phosphatase (PTP) DEP-1 (density-enhanced phosphatase) is a candidate tumor suppressor in the colon epithelium. We have explored the function of DEP-1 in colon epithelial cells by inducible re-expression in a DEP-1-deficient human colon cancer cell line. Density-enhanced phosphatase-1 re-expression led to profound inhibition of cell proliferation and cell migration, and was associated with cytoskeletal rearrangements. These effects were dependent on the PTP activity of DEP-1 as they were not observed with cells expressing the catalytically inactive DEP-1 C1239S variant. shRNA-mediated suppression of DEP-1 in a colon epithelial cell line with high endogenous DEP-1 levels enhanced proliferation, further supporting the antiproliferative function of DEP-1. Nutrients, which are considered to be chemoprotective with respect to colon cancer development, including butyrate, green tea and apple polyphenols, had the capacity to elevate transcription of endogenous DEP-1 mRNA and expression of DEP-1 protein. Upregulation of DEP-1 expression, and in turn inhibition of cell growth and migration may present a previously unrecognized mechanism of chemoprevention by nutrients.

The effects of saquinavir on imatinib-resistant chronic myelogenous leukemia cell lines

We evaluated the effect of the human immunodeficiency virus (HIV) protease inhibitor saquinavir on the imatinib-sensitive and imatinib-resistant chronic myelogenous leukemia cell lines. Saquinavir, which is also a proteasome blocker, showed dose- and time-related anti-proliferative activity, particularly on the imatinib-resistant lines and a pro-apoptotic effect. Association with imatinib caused a significant increase of activity.

Prostatic acid phosphatase as a target molecule in specific immunotherapy for patients with nonprostate adenocarcinoma

Prostatic acid phosphatase (PAP) is one of the prostate-related antigens that are applicable to specific immunotherapy for patients with prostate cancer. In this study, we determined whether or not PAP could be a target molecule in specific immunotherapy for patients with nonprostate cancer. A variety of adenocarcinoma cell lines were examined for their PAP expression at the mRNA and protein levels by reverse transcription polymerase chain reaction and western blot analysis, respectively. Considerable percentages of colon, gastric, and breast cancer cell lines were found to be positive for PAP at both the mRNA and the protein levels. The PAP expression in cancer tissues was also confirmed by immunohistochemical staining. In addition, we examined whether cancer-reactive cytotoxic T lymphocytes (CTLs) could be induced from peripheral blood mononuclear cells (PBMCs) of human leukocyte antigen (HLA) A24+ nonprostate cancer patients by in vitro stimulation with a PAP peptide. As a result, tumor-specific CTLs could be induced from the PBMCs of HLA-A24+ colon and gastric cancer patients. Their cytotoxicity against HLA-A24+ cancer cells was dependent on PAP peptide-specific and CD8+ T cells. These findings indicate that PAP could be a target molecule in specific immunotherapy for patients with nonprostate adenocarcinomas including colon and gastric cancers.

Role of the phosphatase PP4 in the activation of JNK-1 in prostate carcinoma cell lines PC-3 and LNCaP resulting in increased AP-1 and EGR-1 activity

The specific signaling connections between the mitogen-activated protein kinases (MAPK) such as c-Jun N-terminal kinase (JNK-1) and phosphatases PP4 and M3/6, affecting the family of early nuclear factors, is complex and remains poorly understood. JNK-1 regulates cellular differentiation, apoptosis and stress responsiveness by up-regulating early nuclear factors such as c-Jun, a member of the activating protein (AP-1) family, and the Early Growth Factor (EGR-1). C-Jun, when phosphorylated by c-Jun N-terminal kinase (JNK-1) associates with c-Fos to form the AP-1 transcription factor that activates gene expression. We have investigated the regulation of the JNK-1 kinase by co-transfecting phosphatases PP4 and M3/6 in prostate cancer cell lines PC-3 and LNCaP, which have been previously stimulated with human EGF or cisplatin. Co-transfections of plasmids expressing the JNK-1 and the serine/threonine phosphatases PP4 resulted in a significant increase in JNK-1 activity in both PC3 and LNCaP cells. In contrast, co-transfection of JNK-1 with the dual specific phosphatase serine/threonine M3/6 showed only a marginal effect in JNK-1 activity. The phosphatase M3/6 also failed in blocking the induction of JNK-1 activity observed in presence of PP4. The higher activity of JNK-1 was associated with increased activities of the factors c-Jun/AP-1 and EGR-1. This suggests that JNK-1 activity in PC-3 and LNCaP cells requires not only active PP4 for stable maintenance but also suggests that the relative degree of phosphorylation of multiple cellular components is the determinant of JNK-1 stability.

Role of caspase 8 as a determinant in chemosensitivity of p53-mutated head and neck squamous cell carcinoma cell lines

We studied factors that control chemoresistance to 6 head and neck squamous cell carcinoma cell lines carrying p53 mutations. Cell lines were chosen, based on the presence of EGFR amplifications, the presence of H-ras mutations, and the absence of either. WST-1 viability assays showed that, in response to etoposide, Ca922 was most sensitive, HOC313 most resistant, and HSC6 and the others moderately sensitive. A similar tendency was shown by further analyses with cisplatin, 5-fluorouracil, LY294002, and combined treatment with LY294002 and TNF-related apoptosis-inducing ligand (TRAIL). Although both Ca922 and HOC313 had activating mutations upstream of Akt signaling, the constitutive phosphorylation of Akt at S473 was observed in chemosensitive Ca922, but not in chemoresistant HOC313, suggesting that constitutive Akt phosphorylation was not the primary determinant for chemoresistance in these cell lines. Further, by the combined treatment with LY294002 and TRAIL, apoptosis was induced in Ca922 and HSC6 but not in HOC313. Interestingly, caspase 8 was not detected in HOC313, while it was cleaved in the other 2 cell lines. Further, in Ca922 and HSC6 but not in HOC313, caspase 8 inhibitor restored loss of viability induced either with LY294002 and TRAIL or even with etoposide alone. These findings suggest that caspase 8 played an important role in chemoresistance against genotoxic drugs.

HSulf-2, an extracellular endoglucosamine-6-sulfatase, selectively mobilizes heparin-bound growth factors and chemokines: effects on VEGF, FGF-1, and SDF-1

BACKGROUND

Heparin/heparan sulfate (HS) proteoglycans are found in the extracellular matrix (ECM) and on the cell surface. A considerable body of evidence has established that heparin and heparan sulfate proteoglycans (HSPGs) interact with numerous protein ligands including fibroblast growth factors, vascular endothelial growth factor (VEGF), cytokines, and chemokines. These interactions are highly dependent upon the pattern of sulfation modifications within the glycosaminoglycan chains. We previously cloned a cDNA encoding a novel human endosulfatase, HSulf-2, which removes 6-O-sulfate groups on glucosamine from subregions of intact heparin. Here, we have employed both recombinant HSulf-2 and the native enzyme from conditioned medium of the MCF-7-breast carcinoma cell line. To determine whether HSulf-2 modulates the interactions between heparin-binding factors and heparin, we developed an ELISA, in which soluble factors were allowed to bind to immobilized heparin.

RESULTS

Our results show that the binding of VEGF, FGF-1, and certain chemokines (SDF-1 and SLC) to immobilized heparin was abolished or greatly diminished by pre-treating the heparin with HSulf-2. Furthermore, HSulf-2 released these soluble proteins from their association with heparin. Native Sulf-2 from MCF-7 cells reproduced all of these activities.

CONCLUSION

Our results validate Sulf-2 as a new tool for deciphering the sulfation requirements in the interaction of protein ligands with heparin/HSPGs and expand the range of potential biological activities of this enzyme.

Expression of Aurora kinases in human thyroid carcinoma cell lines and tissues

The Aurora kinases are involved in the regulation of cell cycle progression, and alterations in their expression have been shown to associate with cell malignant transformation. In the present study, we demonstrated that human thyrocytes express all 3 Aurora kinases (A, B and C) at both protein and mRNA level and this expression is cell cycle-regulated. An increase in the protein level of the 3 kinases was found, with respect to normal human thyrocytes (HTU5), in the human cell lines derived from follicular (FTC-133), papillary (B-CPAP) and anaplastic (8305C) thyroid carcinomas, but not in cells derived from a follicular adenoma (HTU42). These observations were mirrored in RT-PCR experiments for Aurora-A and B. In contrast, Aurora-C mRNA levels were not significantly different among the different cell types analyzed, suggesting that posttranscriptional mechanism(s) modulate its expression. The expression at the protein level of all 3 Aurora kinases was significantly higher in 3 thyroid papillary carcinomas with respect to normal matched tissues obtained from the same patients. Similar modifications, at the mRNA level, could be observed in 7 papillary carcinoma tissues for Aurora-A and B, but not for Aurora-C. In conclusion, we demonstrated that normal human thyrocytes express all 3 members of the Aurora kinase family, and their expression is amplified in malignant thyroid cell lines and tissues. These results suggest that the Aurora kinases may play a relevant role in malignant thyroid cancers, and may represent a putative therapeutic target for thyroid neoplasms.

The toxicity of extracts of plant parts of Moringa stenopetala in HEPG2 cells in vitro

The cytotoxicity of extracts from a widely used species of plant, Moringa stenopetala, was assessed in HEPG2 cells, by measuring the leakage of lactate dehydrogenase (LDH) and cell viability. The functional integrity of extract-exposed cells was determined by measuring intracellular levels of ATP and glutathione (GSH). The ethanol extracts of leaves and seeds increased significantly (p < 0.01) LDH leakage in a dose- and time-dependent manner. The water extract of leaves and the ethanol extract of the root did not increase LDH leakage. A highly significant (p < 0.001) decrease in HEPG2 viability was found after incubating the cells with the highest concentration (500 microg/mL) of the ethanol leaf and seed extracts. At a concentration of 500 microg/mL, the water extract of leaves increased (p < 0.01), while the ethanol extract of the same plant part decreased (p < 0.01), ATP levels. The root and seed extracts had no significant effect on ATP levels. The ethanol leaf extract decreased GSH levels at a concentration of 500 microg/mL (p < 0.01), as did the ethanol extract of the seeds at 250 microg/mL and 500 microg/mL (p < 0.05). The water extract of the leaves did not alter GSH or LDH levels or affect cell viability, suggesting that it may be non-toxic, and is consistent with its use as a vegetable. The data obtained from the studies with the ethanol extract of the leaves and seeds from Moringa stenopetala show that they contain toxic substances that are extractable with organic solvents or are formed during the process of extraction with these solvents. The significant depletion of ATP and GSH only occurred at concentrations of extract that caused leakage of LDH. Further investigation with this plant in order to identify the constituents extracted and their individual toxic effects both in vivo and in vitro is warranted. This study also illustrates the utility of cell culture for screening plant extracts for potential toxicity.

Functional activity of human hepatoma cells transfected with adenovirus-mediated hepatocyte nuclear factor (HNF)-4 gene

Fulminant hepatic failure (FHF) is still associated with high mortality despite recent advances in medical management. There is need of an effective and safe bioartificial liver (BAL) support to help keep patients with FHF alive until an organ becomes available for transplantation or the native liver recovers. The aim of this study was to establish highly functional liver cells by means of transfecting hepatocyte nuclear factor (HNF)-4 gene for the development of BAL. We constructed adenovirus vector carrying rat HNF-4 cDNA, and transfected to hepatoma-derived cell lines, HepG2 and HuH-7, to enforce expression of the exogenous HNF-4 gene. We analyzed expression of HNF-4, HNF-1, and liver-specific genes in cells infected by the adenovirus vector expressing HNF-4. Adenovirus-mediated HNF-4 gene transfer resulted in increases in expressions of HNF-4, HNF-1, and liver-specific genes such as apolipoproteins, alpha1-antitrypsin (alpha1-AT), phosphoenolpyruvate carboxy-kinase, cytochrome P450 families, and glutamine synthetase in transfected hepatoma cells. Cells overexpressing HNF-4 removed ammonia from medium supplemented with NH4Cl to a greater extent than control cells. These findings demonstrated that transfected cell lines restored differentiated gene expressions and liver-specific function by the overproduction of HNF-4. HNF-4-overexpressing hepatocyte cell lines are useful for bioreactor of BAL systems.

Optimization of the TRAP assay to evaluate specificity of telomerase inhibitors

Telomerase inhibition represents a promising approach to anticancer treatment. In order to clarify the therapeutic potential of telomerase inhibitors we examined different substances (small molecule compounds BIBR1532 and BRACO19, as well as hTR antisense oligonucleotides 2'-O-methyl RNA and PNA) in A-549, MCF-7, and Calu-3 cell lines in a cell-free TRAP assay. We demonstrated that each of the tested agents inhibited telomerase in all used cell lines and that the antisense oligonucleotides represent the most potent inhibitors. Interestingly, upon evaluating the specificity of telomerase inhibitors we found out that not all agents acted specifically against telomerase. We observed that BRACO19 and PNA had an inhibitory effect also on PCR amplification of the TSR8 oligonucleotide which is provided in the TRAP(EZE) kit as a PCR control. By modifying the experimental protocol and using a different reverse primer we were able to enhance PNA selectivity, although the PCR inhibition of the TSR8 control template by BRACO19 could not be prevented. We propose an explanation for the lack of target specificity and suggest caution when testing putative telomerase inhibitors, as it appears that some of those substances may not affect specifically telomerase or telomeric G-rich sequences and thus can lead to the misinterpretation of experimental results.

Possible participation of advanced glycation end products in the pathogenesis of colorectal cancer in diabetic patients

Colorectal cancer is a major public health problem, being the second most common cause of cancer in developed countries. Several epidemiological studies have reported moderately increased risks of colorectal cancer in diabetic patients compared with general population. However, the underlying molecular link between diabetes and colorectal cancer remains to be elucidated. In diabetes mellitus, the formation and accumulation of advanced glycation end products (AGEs) progress. There is a growing body of evidence to show that AGEs-their receptor (RAGE) interactions are involved in the development of atherosclerosis and diabetic microangiopathy. AGEs-RAGE interactions stimulated the growth of human pancreatic cancer cells through the autocrine induction of platelet-derived growth factor-B. Furthermore, we have recently found that AGEs stimulated the growth and migration of cultured human melanoma cells and that anti-RAGE antibodies inhibited tumor formation and lung metastasis of melanoma cell xenografts and subsequently improved survival in athymic mice. These observations let us to hypothesize that AGEs could explain the molecular link between diabetes and colorectal cancer. In this paper, we would like to propose the possible ways of testing our hypotheses. Is elevation of serum AGE levels a risk factor for colorectal cancer in patients with diabetes? Does treatment with metformin, which has a potential effect on the inhibition of glycation reactions in vivo, decrease the risk for colorecetal cancer in diabetic patients? If the answer is yes, is this beneficial effect of metformin superior to that of other anti-diabetic agents with equihypoglycemic properties? Does treatment with pyridoxamine, a post-Amadori inhibitor (so-called Amadorins) of AGE formation, reduce the risk for colorectal cancer as well? Furthermore, are increased levels of AGEs and RAGE in colorectal cancer associated with poor prognosis in patients with diabetes? These clinical studies could clarify whether the AGEs-RAGE interactions serve as a causal link between diabetes and colorectal cancer.

The expression of the human neuronal alpha3 Na+,K+-ATPase subunit gene is regulated by the activity of the Sp1 and NF-Y transcription factors

The Na+,K+-ATPase is a ubiquitous protein found in virtually all animal cells which is involved in maintaining the electrochemical gradient across the plasma membrane. It is a multimeric enzyme consisting of alpha, beta and gamma subunits that may be present as different isoforms, each of which has a tissue-specific expression profile. The expression of the Na+,K+-ATPase alpha3 subunit in humans is confined to developing and adult brain and heart, thus suggesting that its catalytic activity is strictly required in excitable tissues. In the present study, we used structural, biochemical and functional criteria to analyse the transcriptional mechanisms controlling the expression of the human gene in neurons, and identified a minimal promoter region of approx. 100 bp upstream of the major transcription start site which is capable of preferentially driving the expression of a reporter gene in human neuronal cell lines. This region contains the cognate DNA sites for the transcription factors Sp1/3/4 (transcription factors 1/3/4 purified from Sephacryl and phosphocellulose columns), NF-Y (nuclear factor-Y) and a half CRE (cAMP-response element)-like element that binds a still unknown protein. Although the expression of these factors is not tissue-specific, co-operative functional interactions among them are required to direct the activity of the promoter predominantly in neuronal cells.