Chemical constituents from Hovenia dulcis Thunb. And their chemotaxonomic significance

Phytochemical investigations on the fruit stalks and seeds of the plant Hovenia dulcis Thunb. led to the isolation of twenty-one compounds, including three triterpenes (1–3), two sterols (4–5), five flavonoids (6–10), two sesquiterpenes (11–12), one lignan (13), two phenylpropanoids (14–15), four benzoic acid derivatives (16–19), one acid amide (20) and one cerebroside (21). The structures of these compounds were elucidated on the basis of spectroscopic analysis and comparison with previous literatures. Among them, ten compounds (4, 11–12, 14–20) were isolated from familiy Rhamnaceae, two (13, 21) from the genus Hovenia, and three (5, 8, 10) from the species Hovenia dulcis Thunb. for the first time, respectively. The chemotaxonomic significance of these isolates was also discussed.     

Biodegradation of tetrabromobisphenol A by oxidases in basidiomycetous fungi and estrogenic activity of the biotransformation products

Tetrabromobisphenol A (TBBPA) degradation was investigated using white rot fungi and their oxidative enzymes. Strains of the Trametes, Pleurotus, Bjerkandera and Dichomitus genera eliminated almost 1 mM TBBPA within 4 days. Laccase, whose role in TBBPA degradation was demonstrated in fungal cultures, was applied to TBBPA degradation alone and in combination with cellobiose dehydrogenase from Sclerotium rolfsii. Purified laccase from Trametes versicolor degraded approximately 2 mM TBBPA within 5 h, while the addition of cellobiose dehydrogenase increased the degradation rate to almost 2.5 mM within 3 h. Laccase was used to prepare TBBPA metabolites 2,6-dibromo-4-(2-hydroxypropane-2-yl) phenol (1), 2,6-dibromo-4-(2-methoxypropane-2-yl) phenol (2) and 1-(3,5-dibromo-4-hydroxyphen-1-yl)-2,2',6,6'-tetrabromo-4,4'-isopropylidene diphenol (3). As compounds 1 and 3 were identical to the TBBPA metabolites prepared by using rat and human liver fractions (Zalko et al., 2006), laccase can provide a simple means of preparing these metabolites for toxicity studies. Products 1 and 2 exhibited estrogenic effects, unlike TBBPA, but lower cell toxicity.     

Dominant negative alpha-subunit of FTase inhibits effects of insulin and IGF-I in MCF-7 cells

We recently designed a dominant negative (DN) farnesyltransferase (FTase)/geranyl-gerahyltransferase I (GGTase I) alpha-subunit that when expressed in vascular smooth muscle cells decreased insulin-stimulated phosphorylation of FTase, FTase activity, amounts of farnesylated p21Ras, DNA synthesis, and cell migration. Currently, we explored the inhibitory effects of DN FTase/GGTase I alpha-subunit in MCF-7 cells on IGF-1- and insulin-stimulated DNA synthesis and cell proliferation. Expression of the DN FTase/GGTase I alpha-subunit completely blocked IGF-1- and insulin-stimulated BrdU incorporation and cell count. DN FTase/GGTase I alpha-subunit inhibited insulin-stimulated phosphorylation of FTase/GGTase I alpha-subunit, FTase and GGTase I activity, and prenylation of p21Ras and RhoA. Expression of DN FTase/GGTase I alpha-subunit diminished IGF-1- and insulin-stimulated phosphorylation of ERK (extracellular signal-regulated kinase), but had no effect on IGF-1- and insulin-stimulated phosphorylation of Akt. Taken together, these data suggest that DN FTase/GGTase I alpha-subunit can assuage the mitogenic effects of IGF-1 and insulin on MCF-7 breast cancer cells.     

Dual effects of isoflavonoids from Pueraria lobata roots on estrogenic activity and anti-proliferation of MCF-7 human breast carcinoma cells

Pueraria lobata root (PLR), well known as Kudzu root, has recently become commercially available in Western dietary supplements for menopausal symptoms. The scientific basis for its action has been attributed to the action of phytoestrogens. This study aimed to investigate the estrogen-like activity of isoflavonoids isolated from P. lobata root and their safety with respect to their effect on breast cancer cell proliferation. In an E-screen assay, crude MeOH extract of PLR significantly increased the proliferation of MCF-7 cells in a concentration-dependent manner. Among the four fractions obtained by solvent fractionation of MeOH extract, the n-BuOH fraction had significant estrogen-like activities at all concentrations tested. Phytochemical analysis of the n-BuOH fraction led to the isolation of 10 isoflavones (1–10), among which genistein (10) had significant estrogen-like activities at all concentrations tested. These activities were significantly enhanced by treatment with genistein and 17β-estradiol compared with 17β-estradiol alone, and this effect was mediated by decreased expression of estrogen receptor (ER)α and phospho-ERα in MCF-7 cells. In a cell cytotoxicity assay, genistein (10) exhibited significant cytotoxicity in both ER-positive MCF-7 and ER-negative MDA-MB-231 breast cancer cells. This cytotoxicity was characterized by the induction of apoptotic cells stained with annexin V conjugated with Alexa Fluor 488 and involved activation of mitochondria-independent and -dependent apoptosis pathways in MCF-7 cells. Our results demonstrated that genistein (10) has estrogen-like effects dependent on ER pathway activation and anti-proliferative effects mediated by the apoptosis pathway rather than the ER pathway in MCF-7 breast cancer cells.     

Phenol red in the culture medium strongly affects the susceptibility of human MCF-7 cells to roscovitine

Estrogens play an important role in the growth and terminal differentiation of the mammary gland. Prolonged exposure to estrogens seems to predispose women to breast cancer. It recently became evident that not only the intrinsic hormonal status but also external factors such as the occurrence of pharmaceuticals and chemicals with hormone activity in the environment may put women at greater risk of developing breast cancer. We focused on the interference of endocrine disruptors in breast cancer therapy. We observed that phenol red added to the culture medium strongly promoted the cell proliferation and cell cycle progression of human cells expressing the estrogen receptor, and affected their susceptibility to chemotherapy.     

From ligand structure to biological activity: modified estratrienes and their estrogenic and antiestrogenic effects in MCF-7 cells

A variety of compounds, including the selective estrogen receptor (ER) modulators tamoxifen and raloxifene, phytoestrogens such as genistein, and xenoestrogens such as bisphenol, bind to the estrogen receptor and elicit biological responses. Structural studies have linked the altered activity of compounds such as 4-hydroxytamoxifen, raloxifene, genistein, and tetrahydrochrysene, which have substantially different structures from estradiol (E2), to differences in the positioning of the critical "helix 12" within the ligand-binding domain (LBD) of the ER-ligand complex. However, subtle permutations of the E2 molecule would also be expected to modulate the pattern of responses within a cell. Forty-two ligands were constructed by the addition or relocation of double bonds, hydroxyl, keto, amino, and nitro substituents throughout the estra-l,3,5(10)-triene (estratriene) ring system. In this review, we summarize the effects of subtle changes in the estratriene molecule on the ability of the receptor complex to stimulate the growth of MCF-7 cells, or affect the expression of four estrogen-regulated genes (progesterone receptor, pS2 protein, cathepsin D, and tissue plasminogen activator), as well as undergo nuclear processing and downregulate ERalpha mRNA. The affinity of these ligands for, and mechanism of their binding with, the ERalpha have been measured, along with their effect on the conformation of the ER-ERE complex. In particular, two A-ring isomers of E2, 2- and 4-hydroxyestratriene-17beta-ol, display gene selective activity within MCF-7 cells which is dependent on complex endogenous promoters, an intact AF-2 and is sensitive to the level of SRC-1. Both of these A-ring isomers function as antiestrogens. Molecular modeling of these two A-ring isomers complexed with the ER ligand-binding domain supports the idea that the conformation of the LBD is affected by subtle changes in the estratriene structure.     

Novel and potent inhibitors of fatty acid synthase derived from catechins and their inhibition on MCF-7 cells

Fatty acid synthase (FAS) is a potential target for cancer, but potent inhibitors against FAS are scarce. In this study, we found that activities of catechins on inhibiting FAS increased greatly by heating them in acid. The enhancement was positively correlated to H⁺ concentration. The inhibitory activities of the final products from different catechins were similar, all of which were less than 1 μg/mL. The product from ( ? )-epigallocatechin gallate (EGCG) was stable at room temperature, and its inhibitory kinetics and reacting sites on FAS were obviously different from the known FAS inhibitors. It also affected the viability of MCF-7 cells more obviously than EGCG. A putative route of the reaction progress was proposed and the effective inhibitors were deduced to be oligomers of 2-hydroxy-3-(3′, 4′, 5′-trihydroxyphenyl) propenoic acid by analysis of their spectra. The work affords new and potent FAS inhibitors that would be promising candidates for the treatment of cancer.     

Chemical constituents from Nelumbo nucifera leaves and their anti-obesity effects

Nelumbo nucifera Gaertn. (Nymphaeaceae), commonly called lotus, is widely distributed throughout Eastern Asia. It has been used for food and medicine for a long time. A phytochemical investigation of N. nucifera leaves led to the isolation of 13 megastigmanes (1–13), including a new megastigmane, nelumnucifoside A (1), and a new eudesmane sesquiterpene, nelumnucifoside B (14), eight alkaloids (15–22), and 11 flavonoids (23–33). Their chemical structures were determined based on spectroscopic methods including 1D, 2D NMR and MS spectrometry. The relative and absolute stereochemistry of the compounds was determined by NOESY and CD spectrometry, respectively. Compounds 19 and 22 significantly inhibited pancreatic lipase, whereas compounds 15 and 16 showed a strong inhibitory effect on adipocyte differentiation. Therefore, the leaves of N. nucifera have potential as an anti-obesity agent by inhibiting pancreatic lipase and adipocyte differentiation.     

Chemical constituents from Abrus cantoniensis and their cytotoxic effects on cancer cells

Two new compounds named 4-(4-hydroxybenzyl)-isofraxidin (1) and 1''-methoxyl-bavacoumestan B (2), along with five known compounds (3–7) were isolated from the EtOAc-soluble extract of Abrus cantoniensis. Their structures were elucidated with spectroscopic and physico-chemical analyses. All isolates were evaluated for their cytotoxic activities against four cancer cell lines including HepG2, SMMC-7721, A549 and MCF-7. Among them, compounds 1 and 5 exhibited significant cytotoxic activity on the above four cell lines. In particular, 1 showed the potent cytotoxic activity on HepG2 and SMMC-7721 cells with IC₅₀ values of 4.31 ± 0.5 and 3.24 ± 0.9 μM, respectively.     

Phosphorylation of a 27-kDa protein correlates with survival of protein-synthesis-inhibited MCF-7 cells

Summary Previously, we have shown that IGF-1, the phorbol ester 12-0-tetradecanoylphorbol-13-acetate (TPA) and aurintricarboxylic acid (ATA) protected MCF-7 cells against death induced by the protein synthesis inhibitor cycloheximide (CHX). We proposed that phosphorylation of a putative cellular protein(s) may be involved in this survival mechanism. In the present study we investigated the ability of several agents to induce phosphorylation of cellular proteins and correlated this ability to their survival effect. We found that TPA, ATA, and IGF-1 increased the degree of phosphorylation of a 27-kDa protein in a dose- and time-dependent manner in CHX-treated MCF-7 cells. The ED₅₀ values observed were 25 ng/ml, 40 μg/ml and 15 ng/ml for TPA, ATA, and IGF-1, respectively. The effect was measured upon 10 min of cell treatment with each agent; it reached maximum at 60 min and thereafter decreased continuously to control levels. The 27-kDa protein was found in the cytosolic fraction as a phosphorylated serine residue. Further characterization with two-dimensional electrophoresis indicated that the 27-kDa phosphoprotein was resolved into two isoforms with pI 5.7 and 5.9. Such characteristics were observed for the small molecular weight heat shock protein HSP27. Indeed, a single band of 27 kDa was detected immunologically with rabbit polyclonal anti-human HSP27. The inactive phorbol ester αTPA, epidermal growth factor (EGF), and 8-bromoadenosine 3′5′-cyclic monophosphate (Br-cAMP) did not increase phosphorylation of the 27-kDa protein. Cell survival was measured by exposure of the CHX-pretreated cells to increasing concentrations of the various agents for 60 min, followed by a further incubation for 48 h in the presence of CHX only. TPA, ATA, and IGF-1 were found to enhance cell survival, whereas αTPA, EGF, and Br-cAMP did not. Our results indicate a correlation between phosphorylation of a 27-kDa protein, probably HSP27, and enhanced cell survival, suggesting a role for this phosphoprotein in the survival mechanism.     

Artemisinin-indole and artemisinin-imidazole hybrids: Synthesis,cytotoxic evaluation and reversal effects on multidrug resistance in MCF-7/ADR cells

A series of artemisinin derivatives with MDR reversal activity were designed and synthesized. All hybrids were screened to anticancer activities against four human cancer cell lines (A549, MCF-7, HepG-2, MDA-MB-231) and normal human hepatic cell (L02) in vitro. Most of the new compounds showed higher anticancer activities than artemisinin, among which compounds 11a and 11c displayed superior potency with IC₅₀ 6.78?μM and 5.25?μM against MCF-7, respectively. The further research indicated that the most potent 11c induced cell cycle arrest at G2 phase in MCF-7. Additionally, compound 11c showed remarkable MDR reversal activity which reversed adriamycin against MCF-7/ADR cells with IC₅₀ 0.76?μM.     

Recombinant Human erythropoietin reduces viability of MCF-7 breast cancer cells from 3D culture without caspase activation

Recombinant human erythropoietin (rHuEPO) is the erythropoiesis-stimulating hormone that is being used concurrently with chemotherapeutic drugs in the treatment of anemia of cancer. The effect of rHuEPO on cancer cells in 3-dimensional (3D) cultures is not known. The objective of the study was to determine the effect of rHuEPO on the viability of MCF-7 breast cancer cells from 2-dimensional (2D) and 3D cell cultures. The monolayer MCF-7 cells from 2D culture and MCF-7 cell from 3D culture generated by ultra-low adhesive microplate technique, were treated with 0, 0.1, 10, 100 or 200 IU/mL rHuEPO for 24, 48 or 72 h. The effects of rHuEPO on MCF-7 cell viability and proliferation were determined using the (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay (MTT), neutral red retention time (NRRT), trypan blue exclusion assay (TBE), DNA fragmentation, acridine orange/propidium iodide staining (AO/PI) assays. The MCF-7 cells for 3D culture were also subjected to caspase assays and cell cycle analysis using flow cytometry. rHuEPO appeared to have greater effect at lowering the viability of MCF-7 cells from 3D than 2D cultures.rHuEPO significantly (p < 0.05) decreased viability and down-regulated the caspase activities of 3D MCF-7 cells in dose- and time-dependent manner. The cell cycle analysis showed that rHuEPO caused MCF-7 cells to enter the subG0/G1 phase. Thus, the study suggests that rHuEPO has a cytostatic effect on the MCF-7 breast cancer cells from 3D culture.     

Estrogen-like properties of brominated analogs of bisphenol A in the MCF-7 human breast cancer cell line

Tetrabromobisphenol A (TeBBPA) is a four-meta-brominated variant of bisphenol A (BPA) and is one of the most commonly used brominated flame retardants worldwide. We compared the estrogenic potency of TeBBPA, BPA and the brominated analogs mono- (MBBPA), di- (DBBPA), and tribromobisphenol A (TrBBPA) in the estrogen-dependent human breast cancer cell line MCF-7. All of the compounds competed with 17β-estradiol for binding to the estrogen receptor, although the affinity of the test chemicals to the estrogen receptor was much lower than that of 17β-estradiol. TrBBPA and TeBBPA showed a considerably lower access to the estrogen receptors within intact MCF-7 cells incubated in 100% serum compared to incubation in serum-free medium, indicating a strong binding to serum proteins. BPA, MBBPA, and DBBPA showed only a slightly reduced access to the receptors. All of the test compounds induced proliferation in MCF-7 cells, the potential decreasing with increasing number of bromo-substitutions. TeBBPA did not induce maximal cell growth, indicating cytotoxic effects at high concentrations. BPA and the brominated analogs, except TeBBPA, induced progesterone receptor and pS2 to the same extent as 17β-estradiol, although at much higher concentrations. Our studies demonstrate that compared to 17β-estradiol, BPA and the brominated analogs have much lower estrogenic potencies for all of the endpoints tested, TeBBPA being the least estrogenic compound. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synergic prooxidant,apoptotic and TRPV1 channel activator effects of alpha-lipoic acid and cisplatin in MCF-7 breast cancer cells

Background: Resistance to cisplatin (Cisp) in the treatment of breast cancer is a major obstacle. Alpha-lipoic acid (ALA) has both antioxidant and oxidant properties. ALA has been used on stimulation mechanisms of apoptosis and oxidative stress in the treatment of cancer with a combination of chemotherapeutic agents, although its role on molecular mechanisms in the cancer cells has not been clarified yet. The aim of this study was to evaluate if a combination therapy of ALA with Cisp can alter the effect of this chemotherapy drug in the MCF-7 breast cancer cells.

Materials: The MCF-7 cells were divided into four treatment groups as control, Cisp (0.025?mM), ALA (0.05?mM), and Cisp?+?ALA.

Results: Apoptosis, mitochondrial membrane depolarization, reactive oxygen species (ROS) production, lipid peroxidation, PARP1, caspase 3 and 9 expression levels are increased through activating TRPV1 in the cells by the Cisp and ALA treatments, although cell viability, reduced glutathione and glutathione peroxidase (GPx) values were decreased by the treatments. The Cisp and ALA-induced increase of intracellular free Ca²⁺ concentration was decreased with the TRPV1 blocker, capsazepine.

Conclusions: Apoptosis and oxidant effects of Cisp were increased by activation of TRPV1 channels, but its action on the values was further increased by the ALA treatment. Combination therapy of ALA and Cisp could be used as an effective strategy in the treatment of breast cancer.     

Myc stabilization in response to estrogen and phospholipase D in MCF-7 breast cancer cells

Estrogen, which has been strongly implicated in breast cancer, suppresses apoptosis in estrogen receptor (ER) positive MCF-7 breast cancer cells. Phospholipase D (PLD), which is commonly elevated in ER negative breast cancer cells, also suppresses apoptosis. Survival signals generated by both estrogen and PLD are dependent upon elevated Myc expression. We report here that estrogen- and PLD-induced increases in Myc expression are due to reduced turnover of Myc protein. Estrogen and PLD suppressed phosphorylation of Myc at Thr58 - a site that targets Myc for degradation by the proteasome. The data provide a mechanism for elevated Myc expression in hormone-dependent and hormone-independent breast cancer.     

广西小叶红叶藤挥发油化学成分及抗氧化性研究

采用气相色谱-质谱联用技术对小叶红叶藤挥发油的化学成分进行分析,并用DPPH·法、ABTS,+法和铁氰化钾还原法对其抗氧化能力进行研究.结果表明:从小叶红叶藤挥发油分离出221个色谱峰,共鉴定64个化合物,占挥发油总量的95.72％,主要成分为dl-薄荷酮(53.43％)、(E)-薄荷酮(14.20％)、5-甲基-2-...     

ROS-Ca is associated with mitochondria permeability transition pore involved in surfactin-induced MCF-7 cells apoptosis

The surfactin can inhibit proliferation and induce apoptosis in cancer cells. Moreover, surfactin can induce cell death in human breast cancer MCF-7 cells through mitochondrial pathway. However, the molecular mechanism involved in this pathway remains to be elucidated. Here, the reactive oxygen species (ROS) and Ca²⁺ on mitochondria permeability transition pore (MPTP) activity, and MCF-7 cell apoptosis which induced by surfactin were investigated. It is found that surfactin evoked mitochondrial ROS generation, and the surfactin-induced cell death was prevented by N-acetylcysteine (NAC, an inhibitor of ROS). An increasing cytoplasmic Ca²⁺ concentration was detected in surfactin-induced MCF-7 apoptosis, which was inhibited by 1,2-bis (2-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid (BAPTA-AM, a chelator of calcium). In addition, the relationship between ROS generation and the increase of cytoplasm Ca²⁺ was determined. The results showed that surfactin initially induced the ROS formation, leading to the MPTP opening accompanied with the collapse of mitochondrial membrane potential (ΔΨ_m). Then the cytoplasmic Ca²⁺ concentration increased in virtue of the changes of mitochondrial permeability, which was prevented by BAPTA-AM. Besides, cytochrome c (cyt c) was released from mitochondria to cytoplasm through the MPTP and activated caspase-9, eventually induced apoptosis. In summary, surfactin has notable anti-tumor effect on MCF-7 cells, however, there was no obvious cytotoxicity on normal cells.     

Hormonal regulation of lactate dehydrogenase-A through activation of protein kinase C pathways in MCF-7 breast cancer cells

Lactate dehydrogenase A (LDH-A) is hormonally regulated in rodents, and increased expression of LDH-A is observed during mammary gland tumorigenesis. The mechanisms of hormonal regulation of LDH-A were investigated using a series of deletion and mutant constructs derived from the rat LDH-A gene promoter. Results of these studies show that constructs containing the -92 to -37 region of the LDH-A promoter are important for basal and E2-induced transactivation, and mutation of the consensus CRE motif within this region results in significant loss of basal activity and hormone-responsiveness. Gel mobility shift assays using nuclear extracts from MCF-7 cells show that both CREB and ATF-1 interact with the CRE. Studies with kinase inhibitors show that E2-induced activation of this CRE is dependent on protein kinase C, and these data indicate that LDH-A is induced through a non-genomic pathway of estrogen action.     

Removal of sialic acid from the surface of human MCF-7 mammary cancer cells abolishes E-cadherin-dependent cell-cell adhesion in an aggregation assay

Summary MCF-7 human breast cancer cells express E-cadherin and show, at least in some circumstances, E-cadherin-dependent cell-cell adhesion (Bracke et al., 1993). The MCF-7/AZ variant spontaneously displays E-cadherin-dependent fast aggregation; in the MCF-7/6 variant, E-cadherin appeared not to be spontaneously functional in the conditions of the fast aggregation assay, but function could be induced by incubation of the suspended cells in the presence of insulinlike growth factor I (IGF-I) (Bracke et al., 1993). E-cadherin from MCF-7 cells was shown to contain sialic acid. Treatment with neuraminidase was shown to remove this sialic acid, as well as most of the sialic acid present at the cell surface. Applied to MCF-7/AZ, and MCF-7/6 cells, pretreatment with neuraminidase abolished spontaneous as well as IGF-I induced, E-cadherin-dependent fast cell-cell adhesion of cells in suspension, as measured in the fast aggregation assay. Treatment with neuraminidase did not, however, inhibit the possibly different, but equally E-cadherin-mediated, process of cell-cell adhesion of MCF-7 cells on a flat plastic substrate as assessed by determining the percentage of cells remaining isolated (without contact with other cells) 24 h after plating.