6‐Dehydrogingerdione,an active constituent of dietary ginger,induces cell cycle arrest and apoptosis through reactive oxygen species/c‐Jun N‐terminal kinase pathways in human breast cancer cells

This study is the first to investigate the anticancer effect of 6‐dehydrogingerdione (DGE), an active constituent of dietary ginger, in human breast cancer MDA‐MB‐231 and MCF‐7 cells. DGE exhibited effective cell growth inhibition by inducing cancer cells to undergo G2/M phase arrest and apoptosis. Blockade of cell cycle was associated with increased levels of p21, and reduced amounts of cyclin B1, cyclin A, Cdc2 and Cdc25C. DGE also enhanced the levels of inactivated phosphorylated Cdc2 and Cdc25C. DGE triggered the mitochondrial apoptotic pathway indicated by a change in Bax/Bcl‐2 ratios, resulting in caspase‐9 activation. We also found the generation of reactive oxygen species is a critical mediator in DGE‐induced cell growth inhibition. DGE clearly increased the activation of apoptosis signal‐regulating kinase 1 and c‐Jun N‐terminal kinase (JNK), but not extracellular signal‐regulated kinase 1/2 (ERK1/2) and p38. In addition, antioxidants vitamin C and catalase significantly decreased DGE‐mediated JNK activation and apoptosis. Moreover, blocking JNK by specific inhibitors suppressed DGE‐triggered mitochondrial apoptotic pathway. Taken together, these findings suggest that a critical role for reactive oxygen species and JNK in DGE‐mediated apoptosis of human breast cancer.     

Gallic acid induces G2/M phase cell cycle arrest via regulating 14‐3‐3β release from Cdc25C and Chk2 activation in human bladder transitional carcinoma cells

Scope: Cell cycle regulation is a critical issue in cancer treatment. Previously, gallic acid (GA) has been reported to possess anticancer ability. Here, we have evaluated the molecular mechanism of GA on cell cycle modulation in a human bladder transitional carcinoma cell line (TSGH‐8301 cell). Methods and results: Using flow cytometer analysis, exposure of the cells to 40 μM GA resulted in a statistically significant increase in G2/M phase cells, which was accompanied by a decrease in G0/G1 phase cells. GA‐treated cells resulted in significant growth inhibition in a dose‐dependent manner accompanied by a decrease in cyclin‐dependent kinases (Cdk1), Cyclin B1, and Cdc25C, but significant increases in p‐cdc2 (Tyr‐15) and Cip1/p21 by western blotting. Additional mechanistic studies showed that GA induces phosphorylation of Cdc25C at Ser‐216. This mechanism leads to its translocation from the nucleus to the cytoplasm resulting in an increased binding with 14‐3‐3β. When treated with GA, phosphorylated Cdc25C can be activated by ataxia telangiectasia‐mutated checkpoint kinase 2 (Chk2). This might be a DNA damage response as indicated by Ser‐139 phosphorylation of histine H2A.X. Furthermore, treatment of the cells with a Chk2 inhibitor significantly attenuated GA‐induced G2/M phase arrest. Conclusion: These results indicate that GA can induce cell cycle arrest at G2/M phase via Chk2‐mediated phosphorylation of Cdc25C in a bladder transitional carcinoma cell line.     

Induction of the cell cycle arrest and apoptosis by flavonoids isolated from Korean Citrus aurantium L. in non-small-cell lung cancer cells

This study investigated the anti-proliferative and apoptotic effect of flavonoids isolated from Korean Citrus aurantium L. using A549 lung cancer cells. Flavonoids potently inhibited of A549 cells in a dose-dependent manner, whereas flavonoids had a weak inhibitory effect on proliferation of WI-38 cells. Flow cytometry and Western blot analysis showed that flavonoids induced cell cycle arrest at the G2/M checkpoint by controlling the proteins expression level of cyclin B1, cdc2, cdc25c and p21^WAF1/CIP1. Also, flavonoids induced apoptosis through the regulation of the expression of caspases, cleaved PARP and Bax/Bcl-xL ratio. The activity of caspase-3 on A549 cells increased in a dose-dependent manner. These results clearly indicated that the anti-cancer effect of flavonoids on A549 cells follows multiple cellular pathways through G2/M arrest and the induction of apoptosis.     

Lunasin induces apoptosis and modifies the expression of genes associated with extracellular matrix and cell adhesion in human metastatic colon cancer cells

Scope: Lunasin is an arginine‐glycine‐aspartic acid (RGD) cancer preventive peptide. The objective was to evaluate the potential of lunasin to induce apoptosis in human colon cancer cells and their oxaliplatin‐resistant (OxR) variants, and its effect on the expression of human extracellular matrix and adhesion genes. Methods and results: Various human colon cancer cell lines which underwent metastasis were evaluated in vitro using cell flow cytometry and fluorescence microscopy. Lunasin cytotoxicity to different colon cancer cells correlated with the expression of α₅b₁ integrin, being most potent to KM12L4 cells (IC₅₀ = 13 μM). Lunasin arrested cell cycle at G2/M phase with concomitant increase in the expression of cyclin‐dependent kinase inhibitors p21 and p27. Lunasin (5–25 μM) activated the apoptotic mitochondrial pathway as evidenced by changes in the expressions of Bcl‐2, Bax, nuclear clusterin, cytochrome c and caspase‐3 in KM12L4 and KM12L4‐OxR. Lunasin increased the activity of initiator caspase‐9 leading to the activation of caspase‐3 and also modified the expression of human extracellular matrix and adhesion genes, downregulating integrin α₅, SELE, MMP10, integrin β₂ and COL6A1 by 5.01‐, 6.53‐, 7.71‐, 8.19‐ and 10.10‐fold, respectively, while upregulating COL12A1 by 11.61‐fold. Conclusion: Lunasin can be used in cases where resistance to chemotherapy developed.     

Eupafolin,a flavonoid isolated from Artemisia princeps,induced apoptosis in human cervical adenocarcinoma HeLa cells

Although eupafolin, a flavone found in Artemisia princeps Pampanini, has been shown to inhibit the growth of several human cancer cells, its mode of action is poorly understood. In this study, we investigated the pro‐apoptotic activities of eupafolin in human cervical carcinoma HeLa cells. It was found that eupafolin induced apoptosis in a dose‐dependent manner, as evidenced by DNA fragmentation and the accumulation of positive cells for annexin V. In addition, eupafolin triggered the activations of caspases‐3, ‐6, ‐7, ‐8, and ‐9 and the cleavages of their substrates, such as, poly (ADP‐ribose) polymerase and lamin A/C. Furthermore, treatment with eupafolin resulted in a loss of mitochondrial membrane potential (ΔΨ_m), increased the release of cytochrome c to the cytosol, and altered the expression levels of B‐cell lymphoma 2 (Bcl‐2) family proteins. Interestingly, caspase‐8, an initiator caspase, was activated after the loss of ΔΨ_m and the activations of caspases‐3 and ‐9. Moreover, treatment with z‐DEVD‐fmk (a specific caspase‐3 inhibitor) and the overexpression of Bcl‐2 prevented eupafolin‐stimulated caspase‐8 activation. Altogether, these results suggest that the eupafolin‐induced apoptosis in HeLa cells is mediated by caspase‐dependent pathways, involving caspases‐3, ‐9, and ‐8, which are initiated by the Bcl‐2‐dependent loss of ΔΨ_m.     

The p53-, Bax- and p21-dependent inhibition of colon cancer cell growth by 5-hydroxy polymethoxyflavones

Scope: Previously, we reported that 5‐hydroxy polymethoxyflavones (5OH‐PMFs) isolated from orange, namely 5‐hydroxy‐6,7,8,3′,4′‐pentamethoxyflavone, 5‐hydroxy‐3,6,7,8,3′,4′‐hexamethoxyflavone (5HHMF) and 5‐hydroxy‐6,7,8,4′‐tetramethoxyflavone (5HTMF), potently induced apoptosis and cell‐cycle arrest in multiple human colon cancer cells. Herein, using isogenic variants of HCT116 human colon cancer cells, we investigated the effects of p53, Bax and p21 on the apoptosis and cell‐cycle arrest induced by different 5OH‐PMFs. Methods and results: Annexin V/PI co‐staining assay demonstrated that 5HHMF and 5HTMF significantly induced apoptosis in HCT116 (p53^+/+) cells but not in HCT116 (p53^?/?) cells. Furthermore, 5HHMF and 5HTMF significantly induced apoptosis in HCT116 (Bax^+/?) cells, whereas their pro‐apoptotic effects on HCT116 (Bax^?/?) cells were marginal. All three 5OH‐PMFs increased G0/G1 cell population of HCT116 (p53^+/+) cells, and these effects were abolished in HCT116 (p53^?/?) and HCT116 (p21^?/?) cells. Immunoblotting analysis showed that 5HHMF and 5HTMF increased the levels of cleaved caspase‐3, cleaved PARP in both HCT116 (p53^+/+) and HCT116 (Bax^+/?) cells and these effects were much weaker in HCT116 (p53^?/?) and HCT116 (Bax^?/?) cells. Conclusion: Our results demonstrated that 5OH‐PMFs, especially 5HHMF and 5HTMF, induce apoptosis and cell‐cycle arrest by p53‐, Bax‐ and p21‐dependent mechanism.     

Red mold dioscorea‐induced G2/M arrest and apoptosis in human oral cancer cells

BACKGROUND: Monascus‐fermented products are among the most commonly used traditional food supplements. Dioscorea is known to exhibit anticancer properties. In this study the effects of the ethanol extract of red mold dioscorea (RMDE) on cell proliferation, cell cycle and apoptosis in human oral cancer cells were investigated. RESULTS: RMDE exercised growth inhibition on squamous cell carcinoma‐25 (SCC‐25) cells. RMDE‐mediated G2/M phase arrest was associated with the down‐regulation of NF‐κB, resulting in the inhibition of cyclin B1 and CDK1 expression; this may be the mechanism by which RMDE inhibits cancer cells. Furthermore, the proapoptotic activity of RMDE was revealed by the Annexin V‐FITC/PI double‐staining assay. In addition, the proapoptotic effect of RMDE was evident by the inhibition of Bax expression in the mitochondria, resulting in the activation of caspase‐9 and caspase‐3 and subsequent triggering of the mitochondrial apoptotic pathway. RMDE also enhanced caspase‐8 activity, indicating the involvement of the death receptor pathway in RMDE‐mediated SCC‐25 cell apoptosis. CONCLUSION: RMDE treatment inhibited the growth of SCC‐25 cells by arresting cell cycle at the G2/M phase and induced apoptosis in a time‐ and dose‐dependent manner. Therefore RMDE may be a good candidate for development as a dietary supplement against oral cancer. Copyright © 2010 Society of Chemical Industry     

The flavonoid tangeretin activates the unfolded protein response and synergizes with imatinib in the erythroleukemia cell line K562

We explored the mechanism of cell death of the polymethoxyflavone tangeretin (TAN) in K562 breakpoint cluster region‐abelson murine leukemia (Bcr‐Abl+) cells. Flow cytometric analysis showed that TAN arrested the cells in the G₂/M phase and stimulated an accumulation of the cells in the sub‐G₀ phase. TAN‐induced cell death was evidenced by poly(ADP)‐ribose polymerase cleavage, DNA laddering fragmentation, activation of the caspase cascade and downregulation of the antiapoptotic proteins Mcl‐1 and Bcl‐x_L. Pretreatment with the pancaspase inhibitor Z‐VAD‐FMK_blocked caspase activation and cell cycle arrest but did not inhibit apoptosis which suggest that other cell killing mechanisms like endoplasmic reticulum (ER)‐associated cell death pathways could be involved. We demonstrated that TAN‐induced apoptosis was preceded by a rapid activation of the proapoptotic arm of the unfolded protein response, namely PKR‐like ER kinase. This was accompanied by enhanced levels of glucose‐regulated protein of 78 kDa and of spliced X‐box binding protein 1. Furthermore, TAN sensitized K562 cells to the cell killing effects of imatinib via an apoptotic mechanism. In conclusion, our results suggest that TAN is able to induce apoptosis in Bcr‐Abl+ cells via cell cycle arrest and the induction of the unfolded protein response, and has synergistic cytotoxicity with imatinib.     

Antioxidative mechanisms of sea buckthorn fruit extract in mouse embryonic fibroblast cells

This study was conducted to define the antioxidant properties and cytoprotective mechanisms of sea buckthorn fruit extract (SFE) against cellular oxidative stress in mouse embryonic fibroblast (MEF) cells. Cell viability of MEF cells damaged by H₂O₂ was significantly increased by addition of SFE in a concentration dependent manner. Cytoprotective effect of SFE against oxidative damage was observed to be co-related with regulation of cell cycle progression. Induction of cell cycle arrest in G₂/ M checkpoint was mediated by oxidative stress, but significantly reduced by treatment of MEF cells with SFE. Analysis of key regulatory proteins involved in G₂/M arrest showed that SFE treatment leads to down-regulation of both phosphorylated Chk1 and cyclin B, which play important roles in cell cycle arrest of oxidatively damaged cells. Effect of SFE on apoptosis was evaluated by morphological and flow cytometric analysis. Apoptotic cell accumulation occurred by H₂O₂ treatment was decreased by co-treatment of MEF cells with SFE. Early apoptotic process involved in DNA fragmentation and condensation was also inhibited by additional treatment with SFE. Overall results suggest that cytoprotective effect of SFE is mediated by effective radical scavenging activity as well as altered cell cycle regulation which prevent apoptotic cell death induced by cellular oxidative stress.

     

阿魏菇乙酸乙酯相三萜类化合物对食管癌Eca109细胞的增殖抑制及机制

目的：探讨阿魏菇乙酸乙酯相三萜类化合物（ethyl acetate fraction of Pleurotus ferulatus triterpenoid,PFTP-E）对食管癌Eca109细胞的生长抑制作用及可能机制。方法：采用3-(4,5-二甲基噻-2)-2,5-二苯基四氮唑溴盐法检测PFTP-E体外抑制Eca109细胞的增殖活性;Hoechst 33258染色观察细胞凋亡;流式细胞术检测PFTP-E对Eca109细胞的增殖、周期、凋亡、线粒体膜电位以及胞内活性氧水平变化的影响;免疫印迹法检测PFTP-E对细胞凋亡相关蛋白Bcl2、Bax、聚腺苷二磷酸-核糖聚合酶（poly ADP-ribose polymerase,PARP）、含半胱氨酸的天冬氨酸蛋白水解酶（cysteinyl aspartate specific proteinase,Caspase）3、Caspase9、细胞周期相关蛋白Cyclin B1、内质网应激相关蛋白真核起始因子2α（eukaryotic initiation factor 2α,eIF2α）、CHOP以及丝裂原活化蛋白激酶（mitogen-activated protein kinase,MAPK）信号通路相关蛋白表达的影响。结果：PFTP-E以时间和剂量依赖性抑制Eca109细胞的增殖,并将细胞周期阻滞在G2/M期,进而诱导Eca109细胞凋亡。PFTP-E可引起Eca109细胞线粒体膜电位崩溃并导致胞内活性氧水平升高。PFTP-E可上调细胞色素c、Bax、p-eIF2α、CHOP表达,下调Bcl2、Cyclin B1表达,显著增强剪切型PARP、Caspase3及Caspase9表达,同时诱导内质网应激,激活MAPK/JNK信号通路。结论：PFTP-E能有效诱导Eca109细胞凋亡,其抗肿瘤机制与线粒体损伤途径、周期阻滞、内质网应激等有关。     

Neferine induces reactive oxygen species mediated intrinsic pathway of apoptosis in HepG2 cells

Evidence has accumulated concerning the medicinal application of Nelumbo nucifera in the treatment of various diseases. Neferine, an alkaloid from N. nucifera was found to exert cytotoxicity on liver cancer cells HepG2 in a dose-dependent manner. We evaluated its anticancer potential by studying its effect on mitochondrial membrane potential, intracellular calcium levels [Ca²⁺]_i, cell membrane integrity, apoptotic body formation and DNA fragmentation in cultured HepG2 cells. The reactive oxygen species level has been increased upon neferine treatment with concomitant decrease in reduced glutathione. Our data further indicate reduction of ΔψM and increased [Ca²⁺]_i during apoptosis induction by neferine with increased expression of apoptotic proteins such as Bax, Bad, cleaved forms of caspase 3, caspase 9 and PARP, with the downregulation of anti-apoptotic protein Bcl2 in HepG2 cells. Moreover, the expressions of tumour suppressor proteins p53 and PTEN were upregulated along with the downregulation of P-Akt. In addition, expression levels of TNF-α, p38 and ERK1/2 MAP kinases were increased upon neferine treatment. These results imply that mitochondrial-mediated ROS generation induced by neferine leads to caspase-dependent apoptosis in HepG2 cells.     

Contribution of different molecular weight fractions to anticancer effect of sweet potato protein hydrolysates by six proteases on HT‐29 colon cancer cells

The contribution of different molecular weight fractions to anticancer effect of sweet potato protein hydrolysates (SPPH) by six proteases on HT‐29 colon cancer cells was investigated. SPPH prepared by six proteases showed certain antiproliferation effect on HT‐29 cells. Compared with other five proteases, SPPH by Alcalase exhibited the highest antiproliferation effect with the lowest IC₅₀ value of 119.72 μg mL^?1. SPPH by Alcalase was further separated into four fractions (>10, 5–10, 3–5 and <3 kDa), and <3 kDa fractions showed the strongest antiproliferation effect, which was 43.87% at 100 μg mL^?1 (P < 0.05). The <3 kDa fractions could cause G2/M cell cycle arrest with increased p21 expression and induce apoptosis via decreasing Bcl‐2 expression, increasing Bax expression and inducing caspase‐3 activation in HT‐29 cells. In addition, <3 kDa fractions could significantly inhibit cell migration of HT‐29 cells. Thus, SPPH might be potentially used as a natural supplement in functional foods.     

Dicaffeoylquinic acids in Yerba mate (Ilex paraguariensis St. Hilaire) inhibit NF-κB nucleus translocation in macrophages and induce apoptosis by activating caspases-8 and -3 in human colon cancer cells

Scope : The biological functions of caffeoylquinic acid (CQA) derivatives from various plant sources have been partially elucidated. The objectives were to isolate and purify diCQAs from Yerba mate tea leaves and assess their anti‐inflammatory and anti‐cancer capabilities in vitro and explore their mechanism of action. Methods and results : Methanol extracts of dried mate leaves were resolved by flash chromatography and further purified resulting in two fractions one containing 3,4‐ and 3,5‐diCQAs and the other 4,5‐diCQA with NMR‐confirmed structures. Both fractions inhibited LPS‐induced RAW 264.7 macrophage inflammation by suppressing nitric oxide/inducible nitric oxide and prostaglandin E₂/cyclooxygenase‐2 pathways through inhibiting nucleus translocation of Nuclear factor κB subunits, p50 and p65. The diCQA fractions inhibited Human colon cancer cells CRL‐2577 (RKO) and HT‐29 cell proliferation by inducing apoptosis in a time‐ and concentration‐dependent manner, but did not affect the protein levels of p21, p27, p53, and Bax:Bcl‐2 ratio in RKO cells. In HT‐29 cells, however, the diCQA fractions increased Bax:Bcl‐2 ratio. The diCQA fractions increased the activation of caspase‐8 leading to cleavage of caspase‐3 in both RKO and HT‐29 colon cancer cells. Conclusion : The results suggest that diCQAs in Yerba mate could be potential anti‐cancer agents and could mitigate other diseases also associated with inflammation.     

Role of acidic sphingomyelinase in thymol‐mediated dendritic cell death

Scope : Thymol is a component of several plants with antimicrobial activity. Little is known about the effects of thymol on immune cells of the host. This study addressed the effects of thymol on dendritic cells (DCs), regulators of innate and adaptive immunity. Methods and results : Immunohistochemistry, Western blotting and fluorescence‐activated cell sorting analysis were performed in bone marrow‐derived DCs either from wild‐type mice or from mice lacking acid sphingomyelinase (ASM^?/?) treated and untreated for 24 h with thymol (2–100 μg/mL). Thymol treatment resulted in activation of ASM, stimulation of ceramide formation, downregulation of anti‐apoptotic Bcl‐2 and Bcl‐xL proteins, activation of caspase 3 and caspase 8, DNA fragmentation as well as cell membrane scrambling. The effects were dependent on the presence of ASM and were lacking in ASM^?/? mice or in wild‐type DCs treated with sphingomyelinase inhibitor amitriptyline. Conclusion : Thymol triggers suicidal DC death, an effect mediated by and requiring activation of ASM.     

EGCG inhibits protein synthesis,lipogenesis, and cell cycle progression through activation of AMPK in p53 positive and negative human hepatoma cells

In the previous studies, (–)‐epigallocatechin‐3‐gallate (EGCG) has been shown to have anticarcinogenic effects via modulation in protein expression of p53. Using p53 positive Hep G2 and p53 negative Hep 3B cells, we found that treatment of EGCG resulted in dose‐dependent inhibition of cellular proliferation, which suggests that the interaction of EGCG with p53 may not fully explain its inhibitory effect on proliferation. Caloric restriction (CR) reduces the incidence and progression of spontaneous and induced tumors in laboratory rodents. EGCG has multiple beneficial activities similar to those associated with CR. One key enzyme thought to be activated during CR is AMP‐activated kinase (AMPK), a sensor of cellular energy levels. Here, we showed that EGCG activated AMPK in both p53 positive and negative human hepatoma cells. The activation of AMPK suppressed downstream substrates, such as mammalian target of rapamycin (mTOR) and eukaryotic initiation factor 4E‐binding protein‐1 (4E‐BP1) and a general decrease in mRNA translation. Moreover, EGCG activated AMPK decreases the activity and/or expression of lipogenic enzymes, such as fatty acid synthase (FASN) and acetyl‐CoA carboxylase (ACC). Interestingly, the decision between apoptosis and growth arrest following AMPK activation is greatly influenced by p53 status. In p53 positive Hep G2 cells, EGCG blocked the progression of cell cycle at G1 phase by inducing p53 expression and further up‐regulating p21 expression. However, EGCG inducted apoptosis in p53 negative Hep 3B cells. Based on these results, we have demonstrated that EGCG has a potential to be a chemoprevention and anti‐lipogenesis agent for human hepatoma cells.     

Differential effects of resveratrol and its naturally occurring methylether analogs on cell cycle and apoptosis in human androgen‐responsive LNCaP cancer cells

Stilbenes are phytoalexins that become activated when plants are stressed. These compounds exist in foods and are widely consumed. Resveratrol is a grape‐derived stilbene, which possesses a wide range of health‐promoting activities, including anticancer properties. Several other stilbenes structurally similar to resveratrol are also available in food, but their biological activities remain largely unknown. In this study, we compared the effects of resveratrol and its natural derivatives pterostilbene, trans‐resveratrol trimethylether, trans‐pinostilbene and trans‐desoxyrhapontigenin on androgen‐responsive human prostate cancer LNCaP cells. We found that these compounds exert differential effects on LNCaP cell growth, cell cycle and apoptosis. Trans‐resveratrol trimethylether appeared to be the most potent compound among the stilbenes tested. Treatment of LNCaP cells with trans‐resveratrol trimethylether resulted in G2/M blockage while other compounds, including resveratrol, induced G1/S arrest. Moreover, different from other compounds, trans‐resveratrol trimethylether induced apoptosis. At the molecular level, the effects of these compounds on cell cycle correlated with induction of the cyclin‐dependent kinase inhibitor 1A and B mRNA levels. Additionally, these compounds also inhibited both androgen‐ as well as estrogen‐mediated pathways. These results provide mechanistic information on how resveratrol and its methylether analogs may act to contribute to potential antiprostate cancer activity.     

Quercetin‐induced apoptotic cascade in cancer cells: Antioxidant versus estrogen receptor α‐dependent mechanisms

The flavonol quercetin, especially abundant in apple, wine, and onions, is reported to have anti‐proliferative effects in many cancer cell lines. Antioxidant or pro‐oxidant activities and kinase inhibition have been proposed as molecular mechanisms for these effects. In addition, an estrogenic activity has been observed but, at the present, it is poorly understood whether this latter activity plays a role in the quercetin‐induced anti‐proliferative effects. Here, we studied the molecular mechanisms of quercetin committed to the generation of an apoptotic cascade in cancer cells devoid or containing transfected estrogen receptor α (ERα; i.e., human cervix epitheloid carcinoma HeLa cells). Although none of tested quercetin concentrations increase reactive oxygen species (ROS) generation in HeLa cells, quercetin stimulation prevents the H₂O₂‐induced ROS production both in the presence and in the absence of ERα. However, this flavonoid induces the activation of p38/MAPK, leading to the pro‐apoptotic caspase‐3 activation and to the poly(ADP‐ribose) polymerase cleavage only in the presence of ERα. Notably, no down‐regulation of survival kinases (i.e., AKT and ERK) was reported. Taken together, these findings suggest that quercetin results in HeLa cell death through an ERα‐dependent mechanism involving caspase‐ and p38 kinase activation. These findings indicate new potential chemopreventive actions of flavonoids on cancer growth.     

Chemopreventive properties of the bran extracted from a newly-developed Thai rice: The Riceberry

The potential anti-cancer activity of compounds extracted from Riceberry bran was evaluated in human cancer cell lines (Caco-2, MCF-7 and HL-60). Anti-proliferation and BrdU incorporation assays indicated a time–dose dependent effect of dichloromethane (DCM) and methanol (MeOH) extracts, and that HL-60 was the most sensitive cell. DNA fragmentation assay revealed that both extracts could induce different degrees of apoptosis. The apoptotic induction pathway of each extract determined by flow cytometry and immunoblotting assays revealed various phases of cell cycle arrest with alteration of pro-apoptotic p53, caspase-3, and cyclin proteins. The bioactive compounds in each extract were chemically analysed by GC–MS and LC–ESI–MS/MS. Results revealed the presence of two major anthocyanins, cyanidin-3-glucoside and peonidin-3-glucoside, in the MeOH extract, while the DCM extract contained higher content of plant sterols. The latter constituents are considered the major contributors to apoptotic mechanism in the sensitive cell. These bran products are worth developing into medicinal supplements.     

Mitotic catastrophe induced by overexpression of budding yeast Rad2p

Mitotic catastrophe provokes endopolyploidy, giant cell formation and, eventually, delayed cell death. Mitotic catastrophe is induced by defective cell cycle checkpoints and by some anticancer drugs, ionizing radiation and microtubule‐destabilizing agents. RAD2 is a yeast homologue of XPG, which is a human endonuclease involved in nucleotide excision repair. Here we show that Rad2p overexpression alone, in the absence of extrinsic DNA damage, causes cell growth arrest and mitotic catastrophe. Interestingly, Rad2p‐induced cell growth arrest is not caused by the catalytic activity of Rad2p but rather by its C‐terminal region. Cells growth‐arrested by Rad2p induction do not show apoptotic phenotypes and deletion of YCA1, a yeast caspase homologue, does not affect cell growth arrest by Rad2p induction. However, Rad2p‐induced cell growth arrest is released by rad9 deletion but is not affected by downstream DNA damage checkpoint genes. These observations suggest that RAD2 has a function in coordinating cell cycle regulation and damaged DNA repair. Copyright © 2010 John Wiley & Sons, Ltd.