Overexpression of the Nek2 kinase in colorectal cancer correlates with beta-catenin relocalization and shortened cancer-specific survival.

The serine/threonine kinase Nek2 (NIMA-related kinase 2) regulates centrosome separation and mitotic progression, with overexpression causing induction of aneuploidy in vitro. Overexpression may also enable tumour progression through effects upon Akt signalling, cell adhesion markers and the Wnt pathway. The objective of this study was to examine Nek2 protein expression in colorectal cancer (CRC). Nek2 protein expression was examined in a panel of CRC cell lines using Western blotting and immunofluorescence microscopy. Nek2 and beta-catenin expression were examined by immunohistochemistry in a series of resected CRC, as well as their matched lymph node and liver metastases, and correlated with clinicopathological characteristics. Nek2 protein expression in all CRC lines examined was higher than in the immortalised colonocyte line HCEC. Nek2 overexpression was present in 86.4% of resected CRC and was significantly associated with advancing AJCC tumour stage and shortened cancer-specific survival. Elevated Nek2 expression was maintained within all matched metastases from overexpressing primary tumours. Nek2 overexpression was significantly associated with lower tumour membranous beta-catenin expression and higher cytoplasmic and nuclear beta-catenin accumulation. These data support a role for Nek2 in CRC progression and confirm potential for Nek2 inhibition as a therapeutic avenue in CRC.

Curcumin-induced mitotic arrest is characterized by spindle abnormalities, defects in chromosomal congression and DNA damage.

The chemopreventive agent curcumin has anti-proliferative effects in many tumour types, but characterization of cell cycle arrest, particularly with physiologically relevant concentrations, is still incomplete. Following oral ingestion, the highest concentrations of curcumin are achievable in the gut. Although it has been established that curcumin induces arrest at the G(2)/M stage of the cell cycle in colorectal cancer lines, it is not clear whether arrest occurs at the G(2)/M transition or in mitosis. To elucidate the precise stage of arrest, we performed a direct comparison of the levels of curcumin-induced G(2)/M boundary and mitotic arrest in eight colorectal cancer lines (Caco-2, DLD-1, HCA-7, HCT116p53+/+, HCT116p53(-)/(-), HCT116p21(-)/(-), HT-29 and SW480). Flow cytometry confirmed that these lines underwent G(2)/M arrest following treatment for 12h with clinically relevant concentrations of curcumin (5-10 µM). In all eight lines, the majority of this arrest occurred at the G(2)/M transition, with a proportion of cells arresting in mitosis. Examination of the mitotic index using fluorescence microscopy showed that the HCT116 and Caco-2 lines exhibited the highest levels of curcumin-induced mitotic arrest. Image analysis revealed impaired mitotic progression in all lines, exemplified by mitotic spindle abnormalities and defects in chromosomal congression. Pre-treatment with inhibitors of the DNA damage signalling pathway abrogated curcumin-induced mitotic arrest, but had little effect at the G(2)/M boundary. Moreover, pH2A.X staining seen in mitotic, but not interphase, cells suggests that this aberrant mitosis results in DNA damage.

Curcumin ameliorates oxaliplatin-induced chemoresistance in HCT116 colorectal cancer cells in vitro and in vivo.

The aims of this study were to determine potency of oxaliplatin in combination with curcumin in oxaliplatin-resistant cell lines in vitro and to evaluate the efficacy of a novel curcumin formulation (Meriva®) alone and in combination with oxaliplatin in colorectal tumor-bearing mice, exploring relevant pharmacodynamic markers in vivo. Oxaliplatin-resistant HCT116 p53wt and p53(-/-) cell lines were generated, and the effects of oxaliplatin in combination with curcumin on resistance- and proliferation-associated proteins investigated. Eighty nude mice were implanted with HCT116 p53wt colorectal cancer cells before randomization into the following treatment groups: control; Meriva only; oxaliplatin only; Meriva + oxaliplatin. Tumor volume was assessed, as was the expression of Ki-67, cleaved caspase-3 and Notch-1. Curcumin in combination with oxaliplatin was able to decrease proliferative capacity of oxaliplatin-resistant p53 wildtype and p53(-/-) cell lines more effectively than oxaliplatin alone. It also decreased markers associated with proliferation. After 21 days of treatment in the xenograft model, the order of efficacy was combination > Meriva > oxaliplatin > control. The decrease in tumor volume when compared to vehicle-treated animals was 53, 35 and 16%, respectively. Ki-67 and Notch-1 immunoreactivity was decreased by the combination when compared to vehicle-treated animals, with cleaved caspase-3 rising by 4.4-fold. Meriva did not adversely affect the DNA-platinating ability of oxaliplatin. Curcumin enhanced the cytotoxicity of oxaliplatin in models of oxaliplatin resistance in vitro. In vivo, Meriva greatly enhanced oxaliplatin efficacy, without affecting the mode of action of oxaliplatin. Addition of formulated curcumin to oxaliplatin-based chemotherapy regimens has the potential for clinical benefit.

Development of a targeted adductomic method for the determination of polycyclic aromatic hydrocarbon DNA adducts using online column-switching liquid chromatography/tandem mass spectrometry.

Human exposure to polycyclic aromatic hydrocarbons (PAHs) from sources such as industrial or urban air pollution, tobacco smoke and cooked food is not confined to a single compound, but instead to mixtures of different PAHs. The interaction of different PAHs may lead to additive, synergistic or antagonistic effects in terms of DNA adduct formation and carcinogenic activity resulting from changes in metabolic activation to reactive intermediates and DNA repair. The development of a targeted DNA adductomic approach using liquid chromatography/tandem mass spectrometry (LC/MS/MS) incorporating software-based peak picking and integration for the assessment of exposure to mixtures of PAHs is described. For method development PAH-modified DNA samples were obtained by reaction of the anti-dihydrodiol epoxide metabolites of benzo[a]pyrene, benzo[b]fluoranthene, dibenzo[a,l]pyrene (DB[a,l]P) and dibenz[a,h]anthracene with calf thymus DNA in vitro and enzymatically hydrolysed to 2'-deoxynucleosides. Positive LC/electrospray ionisation (ESI)-MS/MS collision-induced dissociation product ion spectra data showed that the majority of adducts displayed a common fragmentation for the neutral loss of 116 u (2'-deoxyribose) resulting in a major product ion derived from the adducted base. The exception was the DB[a,l]P dihydrodiol epoxide adduct of 2'-deoxyadenosine which resulted in major product ions derived from the PAH moiety being detected. Specific detection of mixtures of PAH-adducted 2'-deoxynucleosides was achieved using online column-switching LC/MS/MS in conjunction with selected reaction monitoring (SRM) of the [M+H](+) to [M+H-116](+) transition plus product ions derived from the PAH moiety for improved sensitivity of detection and a comparison was made to detection by constant neutral loss scanning. In conclusion, different PAH DNA adducts were detected by employing SRM [M+H-116](+) transitions or constant neutral loss scanning. However, for improved sensitivity of detection optimised SRM transitions relating to the PAH moiety product ions are required for certain PAH DNA adducts for the development of targeted DNA adductomic methods.

Lapatinib, a dual inhibitor of ErbB-1/-2 receptors, enhances effects of combination chemotherapy in bladder cancer cells.

Survival rate of patients diagnosed with the invasive form of bladder cancer is low suggesting an urgent need to implement novel treatments. GTC (gemcitabine, paclitaxel and cisplatin) is a new chemotherapeutic regimen, which has shown promise in clinical trials. Given that receptor tyrosine kinases of the ErbB family are overexpressed in a high proportion of metastatic bladder tumours, approaches involving small-molecule inhibitors of ErbB receptors in combination with conventional cytostatic drugs are of potential interest. Here, we show that the dual inhibitor of ErbB receptors, lapatinib, enhances cytostatic and induces cytotoxic effects of GTC in two bladder cancer cell lines which differ with regard to expression levels of proteins taking part in the ErbB pathway. Lapatinib inhibited phosphorylation of ErbB receptors and also reduced the level of phosphorylated AKT. Flow cytometry analysis demonstrated that GTC treatment affects cell cycle distribution differently in the presence or absence of lapatinib. In RT112 cells, which express high levels of ErbB receptors and harbour wild-type p53, combined GTC/lapatinib treatment resulted in the phosphorylation of p53 at Ser46 and accumulation of sub-G1 cell populations. Our data indicate that a combinatorial approach involving GTC and lapatinib may have therapeutic potential in a subset of bladder tumours depending on the genetic context.

Extended treatment with physiologic concentrations of dietary phytochemicals results in altered gene expression, reduced growth, and apoptosis of cancer cells.

Dietary phytochemicals exhibit chemopreventive potential in vivo through persistent low-dose exposures, whereas mechanistic in vitro studies with these agents generally use a high-dose single treatment. Because the latter approach is not representative of an in vivo steady state, we investigated antitumor activity of curcumin, 3,3'-diindolylmethane (DIM), epigallocatechin gallate (EGCG), genistein, or indole-3-carbinol (I3C) in breast cancer MDA-MB-231 cells, exposed in long-term culture to low concentrations, achievable in vivo. Curcumin and EGCG increased cell doubling time. Curcumin, EGCG, and I3C inhibited clonogenic growth by 55% to 60% and induced 1.5- to 2-fold higher levels of the basal caspase-3/7 activity. No changes in expression of cell cycle-related proteins or survivin were found; however, I3C reduced epidermal growth factor receptor expression, contributing to apoptosis. Because some phytochemicals are shown to inhibit DNA and histone modification, modulation of expression by the agents in a set of genes (cadherin-11, p21Cip1, urokinase-type plasminogen activator, and interleukin-6) was compared with changes induced by inhibitors of DNA methylation or histone deacetylation. The phytochemicals modified protein and/or RNA expression of these genes, with EGCG eliciting the least and DIM the most changes in gene expression. DIM and curcumin decreased cadherin-11 and increased urokinase-type plasminogen activator levels correlated with increased cell motility. Curcumin, DIM, EGCG, and genistein reduced cell sensitivity to radiation-induced DNA damage without affecting DNA repair. This model has revealed that apoptosis and not arrest is likely to be responsible for growth inhibition. It also implicated new molecular targets and activities of the agents under conditions relevant to human exposure.

Prognostic molecular markers in hepatocellular carcinoma: a systematic review.

Hepatocellular carcinoma (HCC) is the fifth commonest malignancy worldwide and its incidence is rising. Surgery, including transplantation, remains the only potentially curative modality for HCC, yet recurrence rates are high and long-term survival poor. The ability to predict individual recurrence risk and subsequently prognosis would help guide surgical and chemotherapeutic treatment. As understanding of hepatocarcinogenesis has increased, the myriad of genetic and molecular events that drive the hepatocarcinogenic disease process, including angiogenesis, invasion and metastasis, have been identified. This systematic review examines the evidence from published manuscripts reporting the prognostic potential of molecular biomarkers in hepatocellular carcinoma. In summary, a number of molecular biomarkers with prognostic significance have been identified in hepatocellular carcinoma. Not only might these molecules allow more accurate prediction of prognosis for patients with HCC, but they may also provide targets for potential therapeutic agents.

Profiling tumour heterogeneity through circulating tumour DNA in patients with pancreatic cancer.

The majority of pancreatic ductal adenocarcinomas (PDAC) are diagnosed late so that surgery is rarely curative. Earlier detection could significantly increase the likelihood of successful treatment and improve survival. The aim of the study was to provide proof of principle that point mutations in key cancer genes can be identified by sequencing circulating free DNA (cfDNA) and that this could be used to detect early PDACs and potentially, premalignant lesions, to help target early effective treatment. Targeted next generation sequencing (tNGS) analysis of mutation hotspots in 50 cancer genes was conducted in 26 patients with PDAC, 14 patients with chronic pancreatitis (CP) and 12 healthy controls with KRAS status validated by digital droplet PCR. A higher median level of total cfDNA was observed in patients with PDAC (585 ng/ml) compared to either patients with CP (300 ng/ml) or healthy controls (175 ng/ml). PDAC tissue showed wide mutational heterogeneity, whereas KRAS was the most commonly mutated gene in cfDNA of patients with PDAC and was significantly associated with a poor disease specific survival (p=0.018). This study demonstrates that tNGS of cfDNA is feasible to characterise the circulating genomic profile in PDAC and that driver mutations in KRAS have prognostic value but cannot currently be used to detect early emergence of disease. Importantly, monitoring total cfDNA levels may have utility in individuals "at risk" and warrants further investigation.

Inhibition of phosphatidylinositol 3-kinase/protein kinase B signaling is not sufficient to account for indole-3-carbinol-induced apoptosis in some breast and prostate tumor cells.

PURPOSE AND EXPERIMENTAL DESIGN: Indole-3-carbinol has been proposed to induce apoptosis via a mechanism involving inhibition of protein kinase B (PKB) signaling in breast and prostate tumor cell lines. However, no functional data exist, and the effect of indole-3-carbinol on viability is known to be highly cell type specific. Here, we examine any requirement for PKB inhibition in induction of apoptosis by indole-3-carbinol in the MDA MB468 cell line using in vitro kinase assays, transfection, Western blotting, and flow cytometry. Comparison is also made with MCF10CA1 breast and PC3 prostate tumor cells. RESULTS: Indole-3-carbinol directly inhibited activity of phosphatidylinositol 3-kinase (PI3K) immunoprecipitated from HBL100 or MDA MB468 cells in vitro. Nonetheless, we present three lines of evidence that inhibition of PI3K/PKB signaling is not required for induction of apoptosis by indole-3-carbinol. First, 50% inhibition of PKB phosphorylation by LY294002 resulted in only 15% apoptosis after 72 hours, whereas similar PKB inhibition by indole-3-carbinol coincided with 30% apoptosis after only 24 hours. Second, induction of phospho-PKB (p-PKB) levels following stimulation with epidermal growth factor did not prevent indole-3-carbinol-induced apoptosis. Third, overexpression of active PKBalpha did not prevent induction of apoptosis by indole-3-carbinol. Inhibition of PKB phosphorylation by LY294002 in the PC3 and MCF10CA1 tumor cell lines similarly failed to result in a significant increase in apoptosis. CONCLUSIONS: Our results show that inhibition of PI3K/PKB signaling by indole-3-carbinol or LY294002 is not directly correlated with induction of apoptosis in several breast or prostate cell lines.

Ex vivo cancer chemoprevention research possibilities.

The concept of cancer prevention with naturally occurring or synthetic compounds is rapidly gaining momentum as a key field in cancer research. The availability of good models for the determination of the molecular mechanisms of these agents, which frequently have multiple sites of action within a cell, is key to the progression of the field. In this review, we concentrate on the emergence of several in vitro techniques that have significant advantages over more traditional monolayer cell culture, and/or in vivo models. In particular, we focus on the potential of 3D multicellular spheroid models as versatile intermediates between monolayer culture and tumours in situ. In these models, cell-cell interactions and cell-extracellular matrix interactions can closely mimic the environment to which tumour cells would be exposed in vivo, while maintaining the advantages of ease of manipulation of an in vitro system. The in vitro tube formation assay for the study of angiogenesis, the availability of human tissues for research, and the sophisticated technology surrounding DNA microarray and proteomics are also briefly discussed.

Inhibition of the respiratory burst by resveratrol in human monocytes: correlation with inhibition of PI3K signaling.

trans-Resveratrol (t-RVT) has been shown to have a wide range of anti-inflammatory properties, some of which have been suggested to contribute to the molecular explanation of the French Paradox, a possible reason for the low incidence of heart disease in France. The ability of t-RVT to inhibit the production of reactive oxygen species (ROS) from monocytes (differentiated U937) was investigated using isoluminol, luminol, lucigenin, and 2',7'-dichlorofluorescein (DCF). t-RVT (0.1-50 microM) was found to significantly inhibit cellular ROS production stimulated by f-Met-Leu-Phe (fMLP), 12-phorbol 13-myristate, and arachidonic acid after a 1-h preincubation. The efficacy of t-RVT could be increased if it was added directly into the assay. NADPH-dependent superoxide production was measured in cell homogenates and t-RVT (10-50 microM) was found to have no effect on this activity. The majority of these redox probes require a peroxidase to be oxidized; therefore, the inhibitory effect of t-RVT on ROS measured by these probes is complicated by its ability to be oxidized by peroxidase enzymes and thus compete with the probe. t-RVT, known to be oxidized by the horseradish peroxidase (HRP)/H(2)O(2) system, was found to inhibit the HRP-dependent oxidation of the fluorescent probe DCF and the chemiluminescent probe isoluminol. However, using a redox probe that did not require oxidation by a peroxidase (lucigenin), significant inhibition was still observed. Moreover, the inhibitory effects of t-RVT on fMLP-induced ROS production correlated with significant inhibitory effects on fMLP-induced phosphatidylinositol 3-kinase (PI3K) activity at 50 microM and Akt phosphorylation (10-50 microM). Other known inhibitors of both PI3K and Akt were also found to inhibit this response. Therefore, inhibition of signaling through the PI3K to NADPH oxidase by t-RVT might represent an important anti-inflammatory mechanism.

Inhibition of survival signalling by dietary polyphenols and indole-3-carbinol.

Epidemiological studies have long hinted at the possibility that what we eat greatly influences our state of health, in particular our relative risk of developing cancer. In recent years there has been an exponential increase in the number of studies investigating how individual components of the diet interact at the molecular level to determine the fate of a cell. It is now apparent that many such molecules can preferentially inhibit the growth of tumour cells, by inducing cell cycle arrest or apoptosis. The number of signalling pathways and molecular targets involved is continually expanding. Consequently, the picture is becoming ever more complicated, not least because results often appear to be cell-type specific, dose-response relationships are critical, and any one agent appears to have multiple mechanisms of action. In addition most studies have been conducted in cell culture, often with physiologically unachievable concentrations of single agents, making extrapolation to the clinical situation difficult. In this review the mechanisms of action of a few well-studied dietary polyphenols (curcumin, epigallocatechin gallate and resveratrol) and indole-3 carbinol are considered in the light of these issues.

Cancer prevention -- the potential for diet to modulate molecular signalling.

As our understanding of the development of cancer and the complex signalling mechanisms involved improves, we are beginning to appreciate the enormous potential for intervention strategies that prevent or slow down the disease process. Although much research is currently aimed at developing drugs to target key molecules in tumour cells that are responsible for their proliferation and survival, dietary constituents also have potential as anti-cancer agents. Our goal should be not only to identify carcinogenic changes as early as possible and to intervene effectively long before life-threatening tumours develop, but also to understand how a balanced, healthy diet can contribute to reduced incidence, as epidemiology so tantalizingly suggests.

Innovative agents in cancer prevention.

There are many facets to cancer prevention: a good diet, weight control and physical activity, a healthy environment, avoidance of carcinogens such as those in tobacco smoke, and screening of populations at risk to allow early detection. But there is also the possibility of using drugs or naturally occurring compounds to prevent initiation of, or to suppress, tumour growth. Only a few such agents have been used to date in the clinic with any success, and these include non-steroidal anti-inflammatory drugs for colon, finasteride for prostate and tamoxifen or raloxifene for breast tumours. An ideal chemopreventive agent would restore normal growth control to a preneoplastic or cancerous cell population by modifying aberrant signalling pathways or inducing apoptosis (or both) in cells beyond repair. Characteristics for such an agent include selectivity for damaged or transformed cells, good bioavailability and more than one mechanism of action to foil redundancy or crosstalk in signalling pathways. As more research effort is being targeted towards this area, the distinction between chemotherapeutic and chemopreventive agents is blurring. Chemotherapeutic drugs are now being designed to target over- or under-active signalling molecules within cancer cells, a philosophy which is just as relevant in chemoprevention. Development of dietary agents is particularly attractive because of our long-standing exposure to them, their relative lack of toxicity, and encouraging indications from epidemiology. The carcinogenic process relies on the cell's ability to proliferate abnormally, evade apoptosis, induce angiogenesis and metastasise to distant sites. In vitro studies with a number of different diet-derived compounds suggest that there are molecules capable of modulating each of these aspects of tumour growth. However, on the negative side many of them have rather poor bioavailability. The challenge is to uncover their multiple mechanisms of action in order to predict their efficacy, to learn how to use them effectively in combination, and in some cases to redesign them to improve potency or bioavailability. These ideas are illustrated by dietary agents such as indole-3-carbinol (I3C), epigallocatechin gallate (EGCG), curcumin and resveratrol, all of which appear to have a number of different molecular targets, impinging on several signalling pathways. Ultimately it may be possible not only to suppress tumours and to extend quality of life by administering appropriate diet-derived molecules, but also to refine the definition of a cancer chemopreventive diet.

Pharmacokinetics and tissue disposition of indole-3-carbinol and its acid condensation products after oral administration to mice.

Indole-3-carbinol (I3C) and 3,3'-diindolylmethane (DIM) are promising cancer chemopreventive agents in rodent models, but there is a paucity of data on their pharmacokinetics and tissue disposition. The disposition of I3C and its acid condensation products, DIM, [2-(indol-3-ylmethyl)-indol-3-yl]indol-3-ylmethane (LTr(1)), indolo[3,2b]carbazole (ICZ) and 1-(3-hydroxymethyl)-indolyl-3-indolylmethane (HI-IM) was studied, after oral administration of I3C (250 mg/kg) to female CD-1 mice. Blood, liver, kidney, lung, heart, and brain were collected between 0.25 and 24 h after administration and the plasma and tissue concentrations of I3C and its derivatives determined by high-performance liquid chromotography. I3C was rapidly absorbed, distributed, and eliminated from plasma and tissues, falling below the limit of detection by 1 h. Highest concentrations of I3C were detected in the liver where levels were approximately 6-fold higher than those in the plasma. Levels of DIM, LTr(1), and HI-IM were much lower, although they persisted in plasma and tissues for considerably longer. DIM and HI-IM were still present in the liver 24 h after I3C administration. Tissue levels of DIM and LTr(1) were found to be in equilibrium with plasma at almost every time point measured. In addition to acid condensation products of I3C, a major oxidative metabolite (indole-3-carboxylic acid) and a minor oxidative metabolite (indole-3-carboxaldehyde) were detected in plasma of mice after oral administration of I3C. ICZ was also tentatively identified in the liver of these mice. This study shows for the first time that, after oral administration to mice, I3C, in addition to its acid condensation products, is absorbed from the gut and distributed systemically into a number of well-perfused tissues, thus allowing the possibility for some pharmacological activity of the parent compound in vivo.

Indole-3-carbinol inhibits protein kinase B/Akt and induces apoptosis in the human breast tumor cell line MDA MB468 but not in the nontumorigenic HBL100 line.

We have identified a new target for the chemopreventive dietary agent indole-3-carbinol (13C) in the antiapoptotic signaling pathway involving phosphatidylinositol 3'-kinase and protein kinase B (PKB)/Akt. 13C inhibited phosphorylation and activation of PKB in the tumor-derived breast cell line MDA MB468, but not in the immortalized breast line HBL100. We propose that this cell type-specific response to 13C contributes to the differential induction of apoptosis and sensitivity to growth inhibition of the two cell lines (approximate IC50 = 30 microM for the MDA MB468 line, compared with 120 microM for the HBL100 line). 13C only induced apoptosis in the MDA MB468 cell line, but at higher doses, it increased necrosis in the HBL100 line. The tumor cell line was also markedly less able to recover when 13C was removed from the culture medium. Downstream of PKB, 13C decreased nuclear factor kappaB DNA binding, independently of an effect on IkappaB kinase, in the MDA MB468 cell line only. The tumor suppressor PTEN, which prevents phosphorylation and activation of PKB, was expressed in HBL100 cells but was not detected in MDA MB468 cells. In corroboration of the results obtained with the breast cell lines, 13C decreased phospho-PKB levels and induced apoptosis in the prostate cell line LNCaP, which expresses very low levels of PTEN, but did not do so in PTEN-positive DU145 cells. 13C did not affect PTEN levels in any cell line. This is the first study to report a differential mechanistic response of tumor-derived and nontumorigenic cell lines and of PTEN high- and low-expressing cells to 13C and indicates a promising chemopreventive role for 13C against estrogen receptor-alpha-negative, aggressive-phenotype breast tumors.

Relevance of mitogen activated protein kinase (MAPK) and phosphotidylinositol-3-kinase/protein kinase B (PI3K/PKB) pathways to induction of apoptosis by curcumin in breast cells.

Following observations that curcumin inhibited proliferation (IC(50)=1-5 microM), invasiveness and progression through S/G2/M phases of the cell cycle in the non-tumourigenic HBL100 and tumourigenic MDA-MB-468 human breast cell lines, it was noted that apoptosis was much more pronounced in the tumour line. Therefore, the ability of curcumin to modulate signalling pathways which might contribute to cell survival was investigated. After pre-treatment of cells for 20 min, curcumin (40 microM) inhibited EGF-stimulated phosphorylation of the EGFR in MDA-MB-468 cells and phosphorylation of extracellular signal regulated kinases (ERKs) 1 and 2, as well as ERK activity and levels of nuclear c-fos in both cell lines. At a lower dose (10 microM), it also inhibited the ability of anisomycin to activate JNK, resulting in decreased c-jun phosphorylation, although it did not inhibit JNK activity directly. In contrast, the activation of p38 mitogen activated protein kinase (MAPK) by anisomycin was not inhibited. Curcumin inhibited basal phosphorylation of Akt/protein kinase B (PKB) in both cell lines, but more consistently and to a greater extent in the MDA-MB-468 cells. The MAPK kinase (MKK) inhibitor U0126 (10 microM), while preventing ERK phosphorylation in MDA-MB-468 cells, did not induce apoptosis. The PI3K inhibitor LY294002 (50 microM) inhibited PKB phosphorylation in both cells lines, but only induced apoptosis in the MDA-MB-468 line. These results suggest that while curcumin has several different molecular targets within the MAPK and PI3K/PKB signalling pathways that could contribute to inhibition of proliferation and induction of apoptosis, inhibition of basal activity of Akt/PKB, but not ERK, may facilitate apoptosis in the tumour cell line.

Growth-inhibitory effects of the chemopreventive agent indole-3-carbinol are increased in combination with the polyamine putrescine in the SW480 colon tumour cell line.

BACKGROUND: Many tumours undergo disregulation of polyamine homeostasis and upregulation of ornithine decarboxylase (ODC) activity, which can promote carcinogenesis. In animal models of colon carcinogenesis, inhibition of ODC activity by difluoromethylornithine (DFMO) has been shown to reduce the number and size of colon adenomas and carcinomas. Indole-3-carbinol (I3C) has shown promising chemopreventive activity against a range of human tumour cell types, but little is known about the effect of this agent on colon cell lines. Here, we investigated whether inhibition of ODC by I3C could contribute to a chemopreventive effect in colon cell lines. METHODS: Cell cycle progression and induction of apoptosis were assessed by flow cytometry. Ornithine decarboxylase activity was determined by liberation of CO2 from 14C-labelled substrate, and polyamine levels were measured by HPLC. RESULTS: I3C inhibited proliferation of the human colon tumour cell lines HT29 and SW480, and of the normal tissue-derived HCEC line, and at higher concentrations induced apoptosis in SW480 cells. The agent also caused a decrease in ODC activity in a dose-dependent manner. While administration of exogenous putrescine reversed the growth-inhibitory effect of DFMO, it did not reverse the growth-inhibition following an I3C treatment, and in the case of the SW480 cell line, the effect was actually enhanced. In this cell line, combination treatment caused a slight increase in the proportion of cells in the G2/M phase of the cell cycle, and increased the proportion of cells undergoing necrosis, but did not predispose cells to apoptosis. Indole-3-carbinol also caused an increase in intracellular spermine levels, which was not modulated by putrescine co-administration. CONCLUSION: While indole-3-carbinol decreased ornithine decarboxylase activity in the colon cell lines, it appears unlikely that this constitutes a major mechanism by which the agent exerts its antiproliferative effect, although accumulation of spermine may cause cytotoxicity and contribute to cell death. The precise mechanism by which putrescine enhances the growth inhibitory effect of the agent remains to be elucidated, but does result in cells undergoing necrosis, possibly following accumulation in the G2/M phase of the cell cycle.

Liquid chromatographic assay for the simultaneous determination of indole-3-carbinol and its acid condensation products in plasma.

A high-performance liquid chromatographic method was developed for the simultaneous determination of indole-3-carbinol (I3C), 3,3'-diindolylmethane (DIM), [2-(indol-3-ylmethyl)-indol-3-yl]indol-3-ylmethane (LTr(1)), and indolo[3,2b]carbazole (ICZ). Compounds were extracted from mouse plasma using tert.-butyl methyl ether, incorporating 4-methoxy-indole as internal standard. Chromatographic separation utilized a Waters Symmetry RP18 in tandem with a Thermoquest BDS C(18) column, an acetonitrile-water gradient and UV (280 nm) in series with fluorescence (ex. 335 nm; em. 415 nm) detection. Calibration curves were linear (r(2)>0.99) between 50 and 15,000 ng/ml for I3C; 150 and 15,000 ng/ml for LTr(1); and 0.15 and 37.5 ng/ml for ICZ and the method was reproducible and precise (within-day and between-day coefficients of variation below 9.7 and 13%, respectively). The method described is suitable for comprehensive pharmacokinetic studies with indole-3-carbinol.

Induction of apoptosis and cell cycle arrest in human colon carcinoma cells by Corema album leaves.

The leaves of Corema album (Ericaceae), an endemic shrub which grows in Atlantic coastal areas of the Iberian Peninsula, are rich in flavonoids and other secondary metabolites. Silica gel column chromatography of the ethyl acetate extract from dried leaves was performed and a flavonic active fraction was obtained. The cytotoxic activity of this fraction was assessed using the colon cancer cell lines HCT116 and HT29. After 48 hours of treatment, cell viability was determined with luminescence-based ATPLite assay, showing IC50 values of 7.2 +/- 0.7 and 6.8 +/- 1.2 microg/mL, respectively. The study by flow cytometry revealed that the cytotoxicity of this fraction was mediated, at least in part, by induction of apoptosis and G2/M cell cycle arrest. The active fraction was then subjected to Sephadex LH-20 chromatography and two flavonoids were separated and identified as the flavanone pinocembrin and 2',4'-dihydroxychalcone after UV, MS and NMR analysis.