CYP1-Activation and Anticancer Properties of Synthetic Methoxylated Resveratrol Analogues

Naturally occurring stilbenoids, such as the (E)-stilbenoid resveratrol and the (Z)-stilbenoid combretastatin A4, have been considered as promising lead compounds for the development of anticancer drugs. The antitumour properties of stilbenoids are known to be modulated by cytochrome P450 enzymes CYP1A1 and CYP1B1, which contribute to extrahepatic phase I xenobiotic and drug metabolism. Thirty-four methyl ether analogues of resveratrol were synthesised, and their anticancer properties were assessed, using the MTT cell proliferation assay on a panel of human breast cell lines. Breast tumour cell lines that express CYP1 were significantly more strongly affected by the resveratrol analogues than the cell lines that did not have CYP1 activity. Metabolism studies using isolated CYP1 enzymes provided further evidence that (E)-stilbenoids can be substrates for these enzymes. Structures of metabolic products were confirmed by comparison with synthetic standards and LC-MS co-elution studies. The most promising stilbenoid was (E)-4,3',4',5'-tetramethoxystilbene (DMU212). The compound itself showed low to moderate cytotoxicity, but upon CYP1-catalysed dealkylation, some highly cytotoxic metabolites were formed. Thus, DMU212 selectively affects proliferation of cells that express CYP1 enzymes.

Intestinal microbiota and colorectal cancer: a new aspect of research

Colon holds a complex microbial community, which is crucial for maintaining homeostasis and regulating metabolic functions, supporting the intestinal barrier and controlling immune responses. Previous studies have supported a link between intestinal microbiota and colorectal cancer (CRC). Based on these fndings, the present review analyzed the numerous interactions that occur between microbiota and CRC, starting from the role of intestinal microbiota in colonic homoeostasis. Intestinal microbiota is a cause of CRC and involves various mechanisms such as chronic inflammation, the production of genotoxins causing DNA impairment and/or the biosynthesis of toxic compounds. Moreover, basic metabolic factors such as short-chain fatty acids (SCFAs) and bile acids are included in CRC pathogenesis. Different pathogenic pathways have been reported among different CRC regions (proximal or distal). Variations in the microbial populations are reported between the CRC from these colonic sites, possibly reflecting the bacterial dysbiosis and bioflm distribution. Bowel preparation is essential prior to colonoscopy and surgery; there is, however, minor consensus on the effects of this procedure on intestinal microbiota, notably with regard to the long-term outcomes. With regard to the therapeutic strategy in CRC, the intestinal microbiota is further involved in the modulation of the host response to chemotherapeutic agents (5-fluorouracil and irinotecan) by the interference with drug efcacy and by adverse effects and associated toxicity. In addition, the newly emerged research on CRC immunotherapy reveals an important interplay between intestinal microbiota and the immune system, which includes the possibility of targeting microbiota for the enhancement of anticancer treatment. Additional studies will further clarify the interaction between microbiota and CRC, resulting in the development of alternative therapeutic strategies by manipulating microbiota composition.

Physiological and anthocyanin biosynthesis genes response induced by vanadium stress in mustard genotypes with distinct photosynthetic activity

The present study aimed to elucidate the photosynthetic performance, antioxidant enzyme activities, anthocyanin contents, anthocyanin biosynthetic gene expression, and vanadium uptake in mustard genotypes (purple and green) that differ in photosynthetic capacity under vanadium stress. The results indicated that vanadium significantly reduced photosynthetic activity in both genotypes. The activities of the antioxidant enzymes were increased significantly in response to vanadium in both genotypes, although the purple exhibited higher. The anthocyanin contents were also reduced under vanadium stress. The anthocyanin biosynthetic genes were highly expressed in the purple genotype, notably the genes TT8, F3H, and MYBL2 under vanadium stress. The results indicate that induction of TT8, F3H, and MYBL2 genes was associated with upregulation of the biosynthetic genes required for higher anthocyanin biosynthesis in purple compared with the green mustard. The roots accumulated higher vanadium than shoots in both mustard genotypes. The results indicate that the purple mustard had higher vanadium tolerance.

Placental expression of PAPPA, PAPPA-2 and PLAC-1 in pregnacies is associated with FGR

Fetal growth restriction (FGR) is a gynecological disorder of varying etiology. In the present study, an expression analysis of pregnancy-associated plasma protein A (PAPPA), pregnancy-associated plasma protein A2 (PAPPA2) and placenta-specific-1 (PLAC-1) was conducted in pregnancies with FGR and control pregnancies. Placental tissues were collected from pregnancies with FGR (n=16) and control pregnancies (n=16) and the expression of the genes of interest was examined by qPCR. The mean expression levels of PAPPA and PAPPA2 were significantly lower (P<0.001) in placental tissues from FGR pregnancies compared with tissues from healthy subjects, whereas the opposite pattern was observed for PLAC-1 (P<0.001). PAPPA and PLAC-1 expression in FGR and control subjects correlated with birth weight (P<0.001). The findings suggest a possible pathophysiological link between the development of FGR and the expression of PAPPA, PAPPA2 and PLAC-1.

Anti-inflammatory effects of soyasapogenol I-αa via downregulation of the MAPK signaling pathway in LPS-induced RAW 264.7 macrophages

The crude extract of soyasaponins was reported to possess anti-inflammatory activity. We determined the new purity group I saponin, I-αa and I-γa that was isolated from wild soybean (Glycine soja) in terms of its efficacy in protecting RAW 264.7 macrophages from lipopolysaccharide (LPS)-stimuli. Cells were treated with soyasaponin I-αa/I-γa (30-300 μΜ) and LPS (0.1 μg/mL) for 24 h. Soyasaponin I-αa inhibited nitric oxide (NO) production at 100 μg/mL, while soyasaponin I-γa demonstrated this effect at a higher concentration (200 μg/mL). The expression levels of iNOS and COX-2 enzymes were downregulated by both soyasaponins. Soyasaponin I-αa exerted its effect via the TNF-α and IL-1β cytokines. However, soyasaponin I-γa only inhibited the expression of TNF-α. The inflammatory effect of group I soyasaponin was mainly mediated via the phosphorylation of the p38 and JNK proteins. Collectively, these results suggested the potential anti-inflammatory effects of soyasaponins.

Quercetin attenuates the hyperoxic lung injury in neonatal mice: Implications for Bronchopulmonary dysplasia (BPD)

Quercetin (QU) is one of the most common flavonoids that are present in a wide variety of fruits, vegetables, and beverages. This compound possesses potent anti-inflammatory and anti-oxidant properties. Supplemental oxygen is routinely administered to premature infants with pulmonary insufficiency. However, hyperoxia is one of the major risk factors for the development of bronchopulmonary dysplasia (BPD), which is also termed chronic lung disease in premature infants. Currently, no preventive approaches have been reported against BPD. The treatment of BPD is notably limited to oxygen administration, ventilatory support, and steroids. Since QU has been shown to be effective in reducing inflammation and oxidative stress in various disease models, we hypothesized that the postnatal QU treatment of newborn mice will protect against hyperoxic lung injury by the upregulation of the phase I (CYP1A/B) and/or phase II, NADPH quinone reductase enzymes. Newborn C57BL/6J mice within 24 h of birth with the nursing dams were exposed to either 21% O₂ (air) and/or 85% O₂ (hyperoxia) for 7 days. The mice were treated, intraperitoneally (i.p.) once every other day with quercetin, at a concentration of 20 mg/kg, or saline alone from postnatal day (PND) 2-6. The mice were sacrificed on day 7, and lung and liver tissues were collected. The expression levels of CYP1A1, CYP1B1, NQO1 proteins and mRNA as well as the levels of MDA-protein adducts were analyzed in lung and liver tissues. The findings indicated that QU attenuated hyperoxia-mediated lung injury by reducing inflammation and improving alveolarization with decreased number of neutrophil and macrophage infiltration. The attenuation of this lung injury correlated with the upregulation of CYP1A1/CYP1B1/NQO1 mRNA, proteins and the down regulation of NF-kB levels and MDA-protein adducts in lung and liver tissues. The present study demonstrated the potential therapeutic value of quercetin in the prevention and/or treatment of BPD.

Nobiletin bioactivation in MDA-MB-468 breast cancer cells by cytochrome P450 CYP1 enzymes

Nobiletin is a fully methoxylated flavone that has demonstrated anticancer activity via multiple modes of action. In the present study, the metabolism and further antiproliferative activity of nobiletin was evaluated in the CYP1 expressing human breast cancer cell line MDA-MB-468 and the normal breast cell line MCF10A. Nobiletin was metabolized in MDA-MB-468 cells to a single-demethylated derivative assigned NP1. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Nobiletin exhibited submicromolar IC50 (0.1 ± 0.04 μM) in MDA-MB-468 cells, whereas it was considerably less active in MCF10A cells (40 μM). In MDA-MB-468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 300-fold increase was noted in the IC50 (30 ± 2.4 μM) of nobiletin. In the presence of the CYP1 inhibitor acacetin, the conversion of nobiletin to NP1 was significantly reduced in MDA-MB-468 cells. Furthermore, a significant increase was noted in the population of the cells at the G1 phase, following treatment with nobiletin (10 μM) for 24 h compared with the control cells treated with DMSO (0.1%) alone (55.9 ± 0.14 vs. 45.6 ± 1.96), whereas the cell cycle of MCF10A cells was not significantly altered under the same treatment conditions. Taken collectively, the results suggest that nobiletin is selectively bioactivated in MDA-MB-468 breast cancer cells via metabolism by the cytochrome P450 CYP1 family of enzymes.

Anticancer pyridines induce G2/M arrest and apoptosis via p53 and JNK upregulation in liver and breast cancer cells

In the present study, the synthesis and biological evaluation of one novel pyridine and one novel pyridone anticancer compound is reported. The compounds 6-(2,4-dimethoxyphenyl)-4-(3,4-methylenedioxyphenyl)-1H-pyridin-2-one (1) and 2-(2,4-dimethoxyphenyl)-4-(3,4-methylenedioxyphenyl)pyridine (2) were synthesized from a chalchone precursor. 1 was more active than 2 in inhibiting the proliferation of MCF-7 and HepG2 cells, whereas HepG2 cells were more sensitive to the antiproliferative activity of these compounds compared with MCF-7 cells. The lowest IC₅₀ value was noted for compound 1 in HepG2 cells (IC₅₀=4.5±0.3 µM). The mechanism of action involved induction of G2/M arrest and apoptosis. Both 1 and 2 further induced downregulation of the cell cycle-associated protein cyclin D1 and upregulation of the cell cycle inhibitors p53 and p21 and the apoptosis-associated protein JNK in HepG2 cells. Compound 1 was further shown to induce phosphorylation of JNK in HepG2 cells. These results demonstrate promising cytostatic effects for the two novel anticancer compounds in human cancer cells.

Antiproliferative effects of TSA, PXD‑101 and MS‑275 in A2780 and MCF7 cells: Acetylated histone H4 and acetylated tubulin as markers for HDACi potency and selectivity

Inhibition of histone deacetylase enzymes (HDACs) has been well documented as an attractive target for the development of chemotherapeutic drugs. The present study investigated the effects of two prototype hydroxamic acid HDAC inhibitors, namely Trichostatin A (TSA) and Belinostat (PXD-101) and the benzamide Entinostat (MS-275) in A2780 ovarian carcinoma and MCF7 breast adenocarcinoma cells. The three HDACi inhibited the proliferation of A2780 and MCF7 cells at comparable levels, below the µM range. Enzyme inhibition assays in a cell-free system showed that TSA was the most potent inhibitor of total HDAC enzyme activity followed by PXD-101 and MS-275. Incubation of A2780 and MCF7 cells with the hydroxamates TSA and PXD-101 for 24 h resulted in a dramatic increase of acetylated tubulin induction (up to 30-fold for TSA). In contrast to acetylated tubulin, western blot analysis and flow cytometry indicated that the induction of acetylated histone H4 was considerably smaller. The benzamide MS-275 exhibited nearly a 2-fold induction of acetylated histone H4 and an even smaller induction of acetylated tubulin in A2780 and MCF7 cells. Taken together, these data suggest that although the three HDACi were equipotent in inhibiting proliferation of MCF7 and A2780 cells, only the benzamide MS-275 did not induce acetylated tubulin expression, a marker of class IIb HDACs.

Human exposure to endocrine disrupting chemicals: effects on the male and female reproductive systems

Endocrine disrupting chemicals (EDCs) comprise a group of chemical compounds that have been examined extensively due to the potential harmful effects in the health of human populations. During the past decades, particular focus has been given to the harmful effects of EDCs to the reproductive system. The estimation of human exposure to EDCs can be broadly categorized into occupational and environmental exposure, and has been a major challenge due to the structural diversity of the chemicals that are derived by many different sources at doses below the limit of detection used by conventional methodologies. Animal and in vitro studies have supported the conclusion that endocrine disrupting chemicals affect the hormone dependent pathways responsible for male and female gonadal development, either through direct interaction with hormone receptors or via epigenetic and cell-cycle regulatory modes of action. In human populations, the majority of the studies point towards an association between exposure to EDCs and male and/or female reproduction system disorders, such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality and/or function. Despite promising discoveries, a causal relationship between the reproductive disorders and exposure to specific toxicants is yet to be established, due to the complexity of the clinical protocols used, the degree of occupational or environmental exposure, the determination of the variables measured and the sample size of the subjects examined. Future studies should focus on a uniform system of examining human populations with regard to the exposure to specific EDCs and the direct effect on the reproductive system.

The resveratrol analogue, 3,4,5,4'‑trans-tetramethoxystilbene, inhibits the growth of A375 melanoma cells through multiple anticancer modes of action

Resveratrol is a natural dietary product that has demonstrated multifaceted anticancer activity. Several analogues of resveratrol have been synthesized in an effort to enhance the pharmacological potency and improve the pharmacokinetic properties of the compound. 3,4,5,4'‑trans‑tetramethoxystilbene (3,4,5,4'‑TMS) is a methoxylated analogue of resveratrol that has demonstrated anti-proliferative activity in vitro (in cancer cell lines) and in vivo (in xenograft models). In the present study, the anticancer effects of 3,4,5,4'‑TMS in A375 human melanoma cells were examined. 3,4,5,4'‑TMS markedly inhibited the proliferation of A375 cells (IC50=0.7 µM), via a mechanism involving mitotic arrest at the prometaphase stage of cell division. This effect was accompanied by the upregulation of the expression of the mitogen activated protein kinases, JNK and p38, and the concomitant activation of p38, that was verified by the nuclear translocation of the phoshorylated form of the protein. The pharmacological inhibition of p38 by SB203580 (4 µM) attenuated the effects of 3,4,5,4'‑TMS, as demonstrated by decreased cell cycle progression at the mitotic phase. Furthermore, 3,4,5,4'‑TMS increased the total levels of Aurora A, while it inhibited the localization of the protein to the spindle poles. Finally, 3,4,5,4'‑TMS exhibited anti-metastatic activity, inhibiting A375 cell migration and the attachment of the cells to a collagen type IV-coated surface. Collectively, the data suggest that 3,4,5,4'‑TMS is an effective chemotherapeutic drug for the treatment of human melanoma and that it exerts its effects through multiple anticancer modes of action.

Natural products-friends or foes?

A trend in the general population has been observed in recent years regarding the orientation toward preventive measures in health; in this context the increased interest from the users and researchers concerning the active effect of food supplements on the health state and on longevity, is noticeable. All over the world, the consumption of natural foods and of vegetal supplements has increased spectacularly over the last 5-10 years. The decreased prevalence of cardio-vascular diseases associated with Mediterranean diet, as well as the French paradox convinced researchers to scientifically document the beneficial outcomes pointed out by traditional use of plants, and to try to develop supplements that would have the same positive effects as these noticed for diet components. The intense research dedicated to this topic revealed the fact that food supplements are linked to some problematic aspects, such as toxicological side effects when associated with classical synthetic drugs. The food supplement-drug interactions are submitted to complex issues regarding pharmacokinetic interactions leading to changes in absorption, distribution, metabolism and excretion processes with direct impact on effect and toxicological potential. The present review based on recent literature aims at discussing the food-drug interactions with direct impact on efficacy and toxicity of drugs.

Genetic diversity of the KCNE1 gene and susceptibility to postoperative atrial fibrillation

BACKGROUND

The human KCNE1 protein forms the β-subunit of the IKs potassium channel and is important in the regulation of the atrial action potential duration. The purpose of this study was to investigate the association between the nonsynonymous 112G>A mutation of the KCNE1 gene and postcardiac surgery atrial fibrillation (AF).

METHODS AND RESULTS

A cohort of patients scheduled for cardiac surgery was prospectively recruited. The genotype of 112G>A polymorphism was determined using polymerase chain reaction/restriction fragment analysis and confirmed with direct sequencing of the polymerase chain reaction product. In total, 509 patients were recruited in the study, of whom 203 (39.9%) had at least 1 qualifying episode of postoperative AF. An increased frequency of the G allele was observed in the postoperative AF group compared with the group without postoperative AF (0.628 vs 0.552, respectively, P = .016). The individual's relative risk of postoperative AF increased as the number of G alleles increased from 1.36 (95% CI 0.89-2.08) for G allele heterozygotes to 1.62 (95% CI 1.08-2.43) for G allele homozygotes (P = .04 for trend). The multivariate analysis revealed the abnormal ejection fraction (odds ratio [OR] 1.585, 95% CI 1.076-2.331, P = .020), age (OR 1.043, 95% CI 1.022-1.064, P < .001), type of surgery (aortic valve replacement) (OR 1.869, 95% CI 1.094-3.194, P = .022), and the 112G>A genotype (OR 1.401 [in additive model], 95% CI 1.052-1.865, P = .021) to be independent predictors of postoperative AF.

CONCLUSION

This study confirmed the association of the 112G>A polymorphism and postoperative AF in a cohort of patients undergoing cardiac surgery.

Expression profile of CYP1A1 and CYP1B1 enzymes in colon and bladder tumors

Background

The cytochrome P450 CYP1A1 and CYP1B1 enzymes are involved in carcinogenesis via activation of pro-carcinogenic compounds to carcinogenic metabolites. CYP1A1 and CYP1B1 have shown elevated levels in human tumors as determined by qRT-PCR and immunohistochemical studies. However studies that have examined CYP1 expression by enzyme activity assays are limited.

Results

In the current study the expression of CYP1A1 and CYP1B1 was investigated in a panel of human tumors of bladder and colorectal origin by qRT-PCR and enzyme activity assays. The results demonstrated that 35% (7/20) of bladder tumors and 35% (7/20) of colon tumors overexpressed active CYP1 enzymes. CYP1B1 mRNA was overexpressed in 65% and 60% of bladder and colon tumors respectively, whereas CYP1A1 was overexpressed in 65% and 80% of bladder and colon tumors. Mean mRNA levels of CYP1B1 and CYP1A1 along with mean CYP1 activity were higher in bladder and colon tumors compared to normal tissues (p<0.05). Statistical analysis revealed CYP1 expression levels to be independent of TNM status. Moreover, incubation of tumor microsomal protein in 4 bladder and 3 colon samples with a CYP1B1 specific antibody revealed a large reduction (72.5 ± 5.5 % for bladder and 71.8 ± 7.2% for colon) in catalytic activity, indicating that the activity was mainly attributed to CYP1B1 expression.

Conclusions

The study reveals active CYP1 overexpression in human tumors and uncovers the potential use of CYP1 enzymes and mainly CYP1B1 as targets for cancer therapy.

A mechanistic overview of health associated effects of low levels of organochlorine and organophosphorous pesticides

Organochlorine and organophosphate pesticides are compounds that can be detected in human populations as a result of occupational or residential exposure. Despite their occurrence in considerably low levels in humans, their biological effects are hazardous since they interact with a plethora of enzymes, proteins, receptors and transcription factors. In this review we summarize the cell and molecular effects of organochlorine and organophosphate pesticides with respect to their toxicity, with particular emphasis on glucose and lipid metabolism, their interaction with some members of the nuclear receptor family of ligand-activated transcription factors, including the steroid and peroxisome proliferator activated receptors that changes the expression of genes involved in lipid metabolism and xenobiotic detoxification. More importantly, evidence regarding the metabolic degradation of pesticides and their accumulation in tissues is presented. Potential non-cholinergic mechanisms after long-term low-dose organophosphate exposure resulting in neurodevelopmental outcomes and neurodegeneration are also addressed. We conclude that the mechanism of pesticide-mediated toxicity is a combination of various enzyme-inhibitory, metabolic and transcriptional events acting at the cellular and molecular level.

Bioactivation of the citrus flavonoid nobiletin by CYP1 enzymes in MCF7 breast adenocarcinoma cells

Recent studies have demonstrated cytochrome P450 CYP1-mediated metabolism and CYP1-enzyme induction by naturally occurring flavonoids in cancer cell line models. The arising metabolites often exhibit higher activity than the parent compound. In the present study we investigated the CYP1-mediated metabolism of the citrus polymethoxyflavone nobiletin by recombinant CYP1 enzymes and MCF7 breast adenocarcinoma cells. Incubation of nobiletin in MCF7 cells produced one main metabolite (NM1) resulting from O-demethylation in either A or B rings of the flavone moiety. Among the three CYP1 isoforms, CYP1A1 exhibited the highest rate of metabolism of nobiletin in recombinant CYP microsomal enzymes. The intracellular CYP1-mediated bioconversion of the flavone was reduced in the presence of the CYP1A1 and CYP1B1-selective inhibitors α-napthoflavone and acacetin. In addition nobiletin induced CYP1 enzyme activity, CYP1A1 protein and CYP1B1 mRNA levels in MCF7 cells at a concentration dependent manner. MTT assays in MCF7 cells further revealed that nobiletin exhibited significantly lower IC50 (44 μM) compared to cells treated with nobiletin and CYP1A1 inhibitor (69 μM). FACS analysis demonstrated cell a cycle block at G1 phase that was attenuated in the presence of CYP1A1 inhibitor. Taken together the data suggests that the dietary flavonoid nobiletin induces its own metabolism and in turn enhances its cytostatic effect in MCF7 breast adenocarcinoma cells, via CYP1A1 and CYP1B1 upregulation.

Role of paraoxonase 1 (PON1) in organophosphate metabolism: implications in neurodegenerative diseases

Organophosphate pesticides are a class of compounds that are widely used in agricultural and rural areas. Paraoxonase 1 (PON1) is a phase-I enzyme that is involved in the hydrolysis of organophosphate esters. Environmental poisoning by organophosphate compounds has been the main driving force of previous research on PON1 enzymes. Recent discoveries in animal models have revealed the important role of the enzyme in lipid metabolism. However although PON1 function is well established in experimental models, the contribution of PON1 in neurodegenerative diseases remains unclear. In this minireview we summarize the involvement of PON1 genotypes in the occurrence of Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. A brief overview of latest epidemiological studies, regarding the two most important PON1 coding region polymorphisms PON1-L55M and PON1-Q192R is presented. Positive and negative associations of PON1 with disease occurrence are reported. Notably the MM and RR alleles contribute a risk enhancing effect for the development of some neurodegenerative diseases, which may be explained by the reduced lipoprotein free radical scavenging activity that may give rise to neuronal damage, through distinct mechanism. Conflicting findings that fail to support this postulate may represent the human population ethnic heterogeneity, different sample size and environmental parameters affecting PON1 status. We conclude that further epidemiological studies are required in order to address the exact contribution of PON1 genome in combination with organophosphate exposure in populations with neurodegenerative diseases.

Anticancer effects of the metabolic products of the resveratrol analogue, DMU-212: structural requirements for potency

The methoxylated trans-stilbene resveratrol analogue, (E)-3,4,5,4'-tetramethoxystilbene (1), has shown promising antiproliferative activity in in vitro cell line and in vivo models. In vivo 1 gives rise to several metabolic products through demethylation or hydroxylation reactions at the stilbene moiety. In the present study we examined the anticancer activity of 1 and the metabolites (E)-3'-hydroxy-3,4,5,4'-tetramethoxystilbene (2), (E)-4'-hydroxy-3,4,5-trimethoxystilbene (3), (E)-4-hydroxy-3,5,4'-trimethoxystilbene (4) and (E)-3-hydroxy-4,5,4'-trimethoxystilbene (5) by means of cell viability testing, cell cycle analysis, immunostaining and Western blotting. Compounds 1 and 2 exhibited submicromolar toxicity in MCF-7 breast adenocarcinoma and HepG2 hepatoma cells, whereas 3, 4 and 5 were inactive in terms of inhibition of cellular proliferation. Incubation with 1 or 2 at 10 μM for 24h induced apoptosis and G2/M cell cycle arrest in MCF-7 and HepG2 cells. Immunostaining of MCF-7 cells for β-tubulin in the presence of either 1 or 2 revealed shorter localization of the protein around the nucleus, as compared to control cells. Western blot analyses further demonstrated that treatment with either 1 or 2 at concentrations between 30 and 50 μM for 24 h caused a downregulation in the levels of β-tubulin and cyclin D1 expression and an upregulation in the levels of p53 expression in MCF-7 and HepG2 cells. 2 further increased the ratio of mRNA levels of the apoptosis-related genes Bax/Bcl-xL in both MCF-7 and HepG2 cells in a dose-dependent manner. We conclude that 2 inhibits HepG2 and MCF-7 cellular proliferation by inducing apoptosis and G2/M arrest through p53 and Bax/Bcl-xL upregulation. Our findings further demonstrate that trimethoxy substitutions along with the presence of a methoxy group at position 4' are necessary for retaining the activity of 1.

The methoxylated flavones eupatorin and cirsiliol induce CYP1 enzyme expression in MCF7 cells

Flavonoids have often been associated with cancer prevention and activity of the human cytochrome P450 enzymes CYP1A1 and CYP1B1 with the occurrence of cancer. The flavones eupatorin (1) and cirsiliol (2) enhanced CYP1 enzyme activity in a concentration-dependent manner in MCF7 human breast adenocarcinoma cells. In the range of 0-2.5 microM, 2 caused a dose-dependent increase in CYP1B1 mRNA levels and an increase in CYP1A1 mRNA. Compound 1 caused an increase in CYP1A1 and CYP1B1 mRNA at higher doses (approximately 5 microM). Both CYP1B1 and CYP1A1 catalyzed the conversion of 2 into an as yet unidentified compound. Application of the CYP1 family inhibitor, acacetin, significantly increased the IC(50) value of 2 in MCF7 cells, but did not significantly affect the action of 1. The data suggest that 2 induces CYP1 enzyme expression in cancer cells and is subsequently converted by CYP1B1 or CYP1A1 into an antiproliferative agent.

Anticancer effects of the flavonoid diosmetin on cell cycle progression and proliferation of MDA-MB 468 breast cancer cells due to CYP1 activation

Flavonoids constitute a large class of polyphenolic compounds with cancer preventative properties. We have examined the ability of the natural flavone diosmetin to inhibit proliferation of breast adenocarcinoma MDA-MB 468 and normal breast MCF-10A cells and found that this compound is selective for the cancer cells with slight toxicity in the normal breast cells. Diosmetin was metabolised to the structurally similar flavone luteolin in MDA-MB 468 cells, whereas no metabolism was seen in MCF-10A cells. Diosmetin caused G1 arrest at 10 microM in MDA-MB 468 cells after 48-h treatment whereas this effect was not observed in MCF-10A cells. We suggest that diosmetin exerts cytostatic effects in MDA-MB 468 cells, due to CYP1A1 and CYP1B1 catalyzed conversion to the flavone luteolin.

Cytochrome P450 CYP1A1: wider roles in cancer progression and prevention

CYP1A1 is one of the main cytochrome P450 enzymes, examined extensively for its capacity to activate compounds with carcinogenic properties. Continuous exposure to inhalation chemicals and environmental carcinogens is thought to increase the level of CYP1A1 expression in extrahepatic tissues, through the aryl hydrocarbon receptor (AhR). Although the latter has long been recognized as a ligand-induced transcription factor, which is responsible for the xenobiotic activating pathway of several phase I and phase II metabolizing enzymes, recent evidence suggests that the AhR is involved in various cell signaling pathways critical to cell cycle regulation and normal homeostasis. Disregulation of these pathways is implicated in tumor progression. In addition, it is becoming increasingly evident that CYP1A1 plays an important role in the detoxication of environmental carcinogens, as well as in the metabolic activation of dietary compounds with cancer preventative activity. Ultimately the contribution of CYP1A1 to cancer progression or prevention may depend on the balance of procarcinogen activation/detoxication and dietary natural product extrahepatic metabolism.