Mechanisms of cancer chemoprevention by hop bitter acids (beer aroma) through induction of apoptosis mediated by Fas and caspase cascades

The bitter acids of hops (Humulus lupulus L.) mainly consist of alpha-acids, beta-acids, and their oxidation products that contribute the unique aroma of the beer beverage. Hop bitter acids displayed a strong growth inhibitory effect against human leukemia HL-60 cells, with an estimated IC(50) value of 8.67 microg/mL, but were less effective against human histolytic lymphoma U937 cells. Induction of apoptosis was confirmed in HL-60 cells by DNA fragmentation and the appearance of a sub-G1 DNA peak, which were preceded by dissipation of mitochondrial membrane potential, cytochrome c release, and subsequent induction of pro-caspase-9 and -3 processing. Cleavages of PARP and DFF-45 were accompanied with activation of caspase-9 and -3 triggered by hop bitter acids in HL-60 cells. The change in the expression of Bcl-2, Bcl-X(L), and Bax in response to hop bitter acids was studied, and the Bcl-2 protein level slightly decreased; however, the Bcl-X(L) protein level was obviously decreased, whereas the Bax protein level was dramatically increased, indicating that the control of Bcl-2 family proteins by hop bitter acids might participate in the disruption of mitochondrial integrity. In addition, the results showed that hop bitter acids promoted the up-regulation of Fas and FasL prior to the processing and activation of pro-caspase-8 and cleavage of Bid, suggesting the involvement of a Fas-mediated pathway in hop bitter acids-induced cells. Taken together, these findings suggest that a certain intimate link might exist between receptor- and mitochondria-mediated death signalings that committed to cell death induced by hop bitter acids. The induction of apoptosis by hop bitter acids may offer a pivotal mechanism for their chemopreventive action.     

Antcin B and its ester derivative from Antrodia camphorata induce apoptosis in hepatocellular carcinoma cells involves enhancing oxidative stress coincident with activation of intrinsic and extrinsic apoptotic pathway

The triterpenoids methylantcinate B (MAB) and antcin B (AB), isolated from the medicinal mushroom Antrodia camphorata , have been identified as strong cytotoxic agents against various type of cancer cells; however, the mechanisms of MAB- and AB-induced cytotoxicity have not been adequately explored. This study investigated the roles of caspase cascades, reactive oxygen species (ROS), DNA damage, mitochondrial disruption, and Bax and Bcl-2 proteins in MAB- and AB-induced apoptosis of hepatocellular carcinoma (HCC) HepG2 cells. Here, we showed that MAB and AB induced apoptosis in HepG2 cells, as characterized by increased DNA fragmentation, cleavage of PARP, sub-G1 population, chromatin condensation, loss of mitochondrial membrane potential, and release of cytochrome c. Increasing the levels of caspase-2, -3, -8, and -9 activities was involved in MAB- and AB-induced apoptosis, and they could be attenuated by inhibitors of specific caspases, indicating that MAB and AB triggered the caspase-dependent apoptotic pathway. Additionally, the enhanced apoptotic effect correlates with high expression of Fas, Fas ligand, as well as Bax and decreased protein levels of Bcl-(XL) and Bcl-2, suggesting that both the extrinsic and intrinsic apoptosis pathways were involved in the apoptotic processes. Incubation of HepG2 cells with antioxidant enzymes superoxide dismutase and catalase and antioxidants N-acetylcysteine and ascorbic acid attenuated the ROS generation and apoptosis induced by MAB and AB, which indicate that ROS plays a pivotal role in cell death. NADPH oxidase activation was observed in MAB- and AB-stimulated HepG2 cells; however, inhibition of such activation by diphenylamine significantly blocked MAB- and AB-induced ROS production and increased cell viability. Taken together, our results provide the first evidence that triterpenoids MAB and AB induced a NADPH oxidase-provoked oxidative stress and extrinsic and intrinsic apoptosis as a critical mechanism of cause cell death in HCC cells.     

Acacetin induces apoptosis in human gastric carcinoma cells accompanied by activation of caspase cascades and production of reactive oxygen species

Acacetin (5,7-dihydrocy-4'-methoxy flavone), which is a flavonoid compound, possesses anti-peroxidative and anti-inflammatory effects. The effects of acacetin on cell viability in human gastric carcinoma AGS cells were investigated. This study demonstrated that acacetin was able to inhibit cell proliferation and induce apoptosis in a concentration- and time-dependent manner. Acacetin-induced cell death was characterized with changes in nuclear morphology, DNA fragmentation, and cell morphology. The molecular mechanism of acacetin-induced apoptosis was also investigated. Treatment with acacetin caused induction of caspase-3 activity in a time-dependent manner, but not caspase-1 activity, and induced the degradation of DNA fragmentation factor (DFF-45) and poly(ADP-riobse) polymerase. Cell death was completely prevented by a pancaspase inhibitor, Z-Val-Ala-Asp-fluoromethyl ketone. Furthermore, treatment with acacetin caused a rapid loss of mitochondrial transmembrane potential, stimulation of reactive oxygen species (ROS), release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 processing. Antioxidants such as N-acetylcysteine and catalase, but not superoxide dismutase, allopurinol, or pyrrolidine dithiocarbamate, significantly inhibited acacetin-induced cell death. In addition, it was found that acacetin promoted the up-regulation of Fas and FasL prior to the processing and activation of pro-caspase-8 and cleavage of Bid, suggesting the involvement of a Fas-mediated pathway in acacetin-induced apoptosis. On the other hand, the results showed that acacetin-induced apoptosis was accompanied by up-regulation of Bax and p53, down-regulation of Bcl-2, and cleavage of Bad. Taken together, these results suggest that ROS production and a certain intimate link might exist between receptor- and mitochondria-mediated death signalings that committed to acacetin-induced apoptosis in AGS cells. The induction of apoptosis by acacetin may provide a pivotal mechanism for its cancer chemopreventive action.     

Induction of apoptosis by vitamin D2, ergocalciferol, via reactive oxygen species generation, glutathione depletion, and caspase activation in human leukemia Cells

This study demonstrated that ergocalciferol was able to inhibit leukemia cell growth in a concentration-dependent manner. Exploration of the acting mechanisms involved this event revealed that ergocalciferol induced DNA fragmentation and increased sub-G1 DNA contents in HL-60 cells, both of which are hallmarks of apoptosis. Analysis of the integrity of mitochondria demonstrated that ergocalciferol caused loss of mitochondrial membrane potential with release cytochrome c to cytosol, generation of reactive oxygen species (ROS), and depletion of glutathione (GSH), suggesting that ergocalciferol may induce apoptosis in HL-60 cells through a ROS-dependent pathway. Further results show that caspases-2, -3, -6, and -9 were all activated by ergocalciferol, together with cleavage of the downstream caspase-3 targets, DNA fragmentation factor (DFF-45), and poly(ADP-ribose) polymerase. In addition, ergocalciferol led to the increase in pro-apoptotic factor Bax accompanied with the decrease in anti-apoptotic member Mcl-1, and the reduced Mcl-1 to Bax ratio may be a critical event concerning mitochondrial decay by ergocalciferol. Furthermore, ergocalciferol also led to induction of Fas death receptor closely linked to caspase-2 activation, suggesting the involvement of a Fas-mediated pathway in ergocalciferol-induced apoptosis. Totally, these findings suggest that ergocalciferol causes HL-60 apoptosis via a modulation of mitochondria involving ROS production, GSH depletion, caspase activation, and Fas induction. On the basis of anticancer activity of ergocalciferol, it may be feasible to develop chemopreventive agents from edible mushrooms or hop.     

Oleifolioside A mediates caspase-independent human cervical carcinoma HeLa cell apoptosis involving nuclear relocation of mitochondrial apoptogenic factors AIF and EndoG

Apoptosis, the main type of programmed cell death, plays an essential role in a variety of biological events. Whereas "classical" apoptosis is dependent on caspase activation, caspase-independent death is increasingly recognized as an alternative pathway. To develop new anticancer agents, oleifolioside A was isolated from Dendropanax morbifera Leveille and the biochemical mechanisms of oleifolioside A-induced apoptosis in HeLa cells were investigated. Exposure to oleifolioside A resulted in caspase activation and typical features of apoptosis, although cell death was not prevented by caspase inhibition. Oleifolioside A treatment induced up-regulation of Bad, loss of mitochondrial membrane potential, nuclear relocation of mitochondrial factors, apoptosis-inducing factor (AIF), endonuclease G (EndoG), and apoptosis induction. This is the first report of anticancer activity of oleifolioside A, and nuclear translocation of AIF and EndoG in oleifolioside A-treated HeLa cells might represent an alternative death signaling pathway in the absence of caspase activity.     

Mycelia from Antrodia camphorata in Submerged culture induce apoptosis of human hepatoma HepG2 cells possibly through regulation of Fas pathway

The objective of this study was to investigate the antiproliferative effect and the mechanism of the methanol extracts of mycelia (MEM) form Antrodia camphorata in submerged culture toward HepG2 cells. The results showed that MEM-induced cell apoptosis involved up-regulation of Fas and down-regulation of Bcl-2, DR3, DR4, TNFRI, and TNFRII in HepG2 cells, while no changes on the levels of Bax, Bid, Bad, and Bak protein were observed. On the basis of these results, the involvement of the Fas/Fas ligand (FasL) death-receptor pathway, in MEM-induced apoptosis in HepG2 cells, was investigated. The apoptosis inducing activity was significantly enhanced by a Fas activator and inhibited by a Fas antagonist. To know about the effect of MEM on the activation of the apoptotic pathway, the adenovirus transfected with Bcl-2 was infected on HepG2 cells. The data showed that the percentage of apoptotic cells induced by MEM in Bcl-2-infected HepG2 (Bcl-2 overexpression) was not significantly different from that of uninfected HepG2. These results demonstrate that MEM induces HepG2 apoptosis through inhibition of cell growth and up-regulation of Fas/FasL to activate the pathway of caspase-3 and -8 cascades.     

Protective effects of Chinese propolis and its component, chrysin, against neuronal cell death via inhibition of mitochondrial apoptosis pathway in SH-SY5Y cells

Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of neurodegenerative and ischemic disorders. The purpose of this study was to evaluate the effects of Chinese propolis and its constituents [chrysin, galangin, pinocembrin, caffeic acid, and caffeic acid phenethyl ester (CAPE)] against tunicamycin-induced neuronal cell death in SH-SY5Y cells. Both Chinese propolis and chrysin concentration-dependently inhibited such cell death, the tunicamycin-induced activation of caspase-3, and the effects of tunicamycin on mitochondria [release of cytochrome c into the cytosol and disruption of the mitochondrial membrane potential (DeltaPsim)]. Furthermore, Chinese propolis and chrysin each inhibited staurosporine-induced cell death. These findings indicate that the inhibitory effects of Chinese propolis against neuronal cell death induced by ER stress or staurosporine may be exerted primarily by chrysin. Moreover, the mechanism underlying the protective effects may, at least partly, involve inhibitions of caspase-3 activity and the mitochondrial apoptotic pathway.     

Growth suppression of HER2-overexpressing breast cancer cells by berberine via modulation of the HER2/PI3K/Akt signaling pathway

Berberine (BBR) is a natural alkaloid with significant antitumor activities against many types of cancer cells. This study investigated the molecular mechanisms by which BBR suppresses the growth of HER2-overexpressing breast cancer cells. The results show that BBR induces G1-phase cell cycle arrest by interfering with the expression of cyclins D1 and E and that it induces cellular apoptosis through the induction of a mitochondria/caspase pathway. The data also indicate that BBR inhibits cellular growth and promotes apoptosis by down-regulating the HER2/PI3K/Akt signaling pathway. Furthermore, it is also shown that a combination of taxol and BBR significantly slows the growth rate of HER2-overexpressing breast cancer cells. In conclusion, this study suggests that BBR could be a useful adjuvant therapeutic agent in the treatment of HER2-overexpressing breast cancer.     

Pterostilbene induces apoptosis and cell cycle arrest in human gastric carcinoma cells

Pterostilbene, an active constituent of blueberries, is known to possess anti-inflammatory activity and also induces apoptosis in various types of cancer cells. Here, the effects of pterostilbene on cell viability in human gastric carcinoma AGS cells were investigated. This study demonstrated that pterostilbene was able to inhibit cell proliferation and induce apoptosis in a concentration- and time-dependent manner. Pterostilbene-induced cell death was characterized with changes in nuclear morphology, DNA fragmentation, and cell morphology. The molecular mechanism of pterostilbene-induced apoptosis was also investigated. The results show the caspase-2, -3, -8, and -9 are all activated by pterostilbene, together with cleavage of the downstream caspase-3 target DNA fragmentation factor (DFF-45) and poly(ADP-riobse) polymerase. Moreover, the results indicate that the Bcl-family of proteins, the mitochondrial pathway, and activation of the caspase cascade are responsible for pterostilbene-induced apoptosis. Pterostilbene markedly enhanced the expression of growth arrest DNA damage-inducible gene 45 and 153 (GADD45 and GADD153) in a time-dependent manner. Flow cytometric analysis indicated that pterostilbene blocked cell cycle progression at G1 phase in a dose- and time-dependent manner. Pterostilbene increased the p53, p21, p27, and p16 proteins and decreased levels of cyclin A, cyclin E, cyclin-dependent kinase 2 (Cdk2), Cdk4, and Cdk6, but the expression of cyclin D1 was not affected. Over a 24 h exposure to pterostilbene, the degree of phosphorylation of Rb was decreased after 6 h. In summary, pterostilbene induced apoptosis in AGS cells through activating the caspase cascade via the mitochondrial and Fas/FasL pathway, GADD expression, and by modifying cell cycle progress and changes in several cycle-regulating proteins. The induction of apoptosis by pterostilbene may provide a pivotal mechanism of the antitumor effects and for treatment of human gastric cancer.     

Induction of apoptosis by 1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione through reactive oxygen species production, GADD153 expression, and caspases activation in human epidermoid carcinoma cells

This study examined the growth inhibitory effects of the structurally related beta-diketones compounds in human cancer cells. Here, we report that 1-(2-hydroxy-5-methylphenyl)-3-phenyl-1,3-propanedione (HMDB) induces growth inhibition of human cancer cells and induction of apoptosis in A431 cells through modulation of mitochondrial functions regulated by reactive oxygen species (ROS). ROS generation occurs in the early stages of HMDB-induced apoptosis, preceding cytochrome c release, caspase activation, and DNA fragmentation. The changes occurred after single breaks in DNA were detected, suggesting that HMDB induced irreparable DNA damage, which in turn triggered the process of apoptosis. Up-regulation of Bad and p21; down-regulation of Bcl-2, Bcl-XL, Bid, p53, and fatty acid synthase; and cleavage of Bax were found in HMDB-treated A431 cells. Glutathione and N-acetylcysteine (NAC) suppress HMDB-induced apoptosis. HMDB markedly enhanced growth arrest DNA damage inducible gene 153 (GADD153) mRNA and protein in a time- and concentration-dependent manner. NAC prevented up-regulation of GADD153 mRNA expression caused by HMDB. These findings suggest that HMDB creates an oxidative cellular environment that induces DNA damage and GADD153 gene activation, which in turn helps trigger apoptosis in A431 cells.     

Induction of apoptosis by garcinol and curcumin through cytochrome c release and activation of caspases in human leukemia HL-60 cells

Garcinol, a polyisoprenylated benzophenone, was purified from Garcinia indica fruit rind. The effects of garcinol and curcumin on cell viability in human leukemia HL-60 cells were investigated. Garcinol and curcumin displayed strong growth inhibitory effects against human leukemia HL-60 cells, with estimated IC(50) values of 9.42 and 19.5 microM, respectively. Garcinol was able to induce apoptosis in a concentration- and time-dependent manner; however, curcumin was less effective. Treatment with garcinol caused induction of caspase-3/CPP32 activity in a dose- and time-dependent manner, but not caspase-1 activity, and induced the degradation of poly(ADP-ribose) polymerase (PARP). Pretreatment with caspase-3 inhibitor inhibited garcinol-induced DNA fragmentation. Treatment with garcinol (20 microM) caused a rapid loss of mitochondrial transmembrane potential, release of mitochondrial cytochrome c into cytosol, and subsequent induction of procaspase-9 processing. The cleavage of D4-GDI, an abundant hematopoietic cell GDP dissociation inhibitor for the Ras-related Rho family GTPases, occurred simultaneously with the activation of caspase-3 but preceded DNA fragmentation and the morphological changes associated with apoptotic cell death. Of these, Bcl-2, Bad, and Bax were studied. The level of expression of Bcl-2 slightly decreased, while the levels of Bad and Bax were dramatically increased in cells treated with garcinol. These results indicate that garcinol allows caspase-activated deoxyribonuclease to enter the nucleus and degrade chromosomal DNA and induces DFF-45 (DNA fragmentation factor) degradation. It is suggested that garcinol-induced apoptosis is triggered by the release of cytochrome c into the cytosol, procaspase-9 processing, activation of caspase-3 and caspase-2, degradation of PARP, and DNA fragmentation caused by the caspase-activated deoxyribonuclease through the digestion of DFF-45. The induction of apoptosis by garcinol may provide a pivotal mechanism for its cancer chemopreventive action.     

Growth inhibition and induction of apoptosis in NB4 promyelocytic leukemia cells by trypsin inhibitor from sweet potato storage roots

The objective of this study was to investigate the antiproliferative effect and the mechanism of trypsin inhibitor (TI) from sweet potato [Ipomoea batatas (L.) Lam. 'Tainong 57'] storage roots on NB4 promyelocytic leukemia cells. The results showed that TI inhibited cellular growth of NB4 promyelocytic leukemia cells in a time-dependent and dose-dependent manner, and treatment for 72 h induced a marked inhibition of cellular growth, showing an IC50 of 57.1 +/- 8.26 microg/mL. TI caused cell cycle arrest at the G1 phase as determined by flow cytometric analysis and apoptosis as shown by DNA laddering. TI-induced cell apoptosis involved p53, Bcl-2, Bax, and cytochrome c protein in NB4 cells. P53 and Bax proteins were accumulated, and antiapoptotic molecule Bcl-2 was decreased in the tested cells in a time-dependent manner during TI treatment. TI also induced a substantial release of cytochrome c from the mitochondria into the cytosol. Hence, TI induced apoptosis in NB4 cells through a mitochondria-dependent pathway, which was associated with the activation of caspase-3 and -8. These results demonstrated that TI induces NB4 cell apoptosis through the inhibition of cell growth and the activation of the pathway of caspase-3 and -8 cascades.     

α-Mangostin induces apoptosis in human chondrosarcoma cells through downregulation of ERK/JNK and Akt signaling pathway

Chondrosarcoma is a malignant primary bone tumor that is resistant to chemotherapy and radiation therapy. α-Mangostin, a component of Garcinia mangostana Linn, is a xanthone derivative shown to have antioxidant and antitumor properties. This study is the first to investigate anticancer effects of α-mangostin in the human chondrosarcoma cell line SW1353. We showed that α-mangostin inhibited cell proliferation of SW1353 cells in a time- and dose-dependent manner by using the trypan blue exclusion method. Hoechst 33342 nuclear staining and nucleosomal DNA-gel electrophoresis revealed that α-mangostin could induce nuclear condensation and fragmentation, typically seen in apoptosis. Flow cytometry using Annexin V/PI double staining assessed apoptosis, necrosis and viability. α-Mangostin activated caspase-3, -8, -9 expression, decreased Bcl-2 and increased Bax. This promotes mitochondrial dysfunction, leading to the release of cytochrome c from the mitochondria to the cytoplasm. In addition, total and phosphorylated ERK and JNK were downregulated in α-mangostin-treated SW1353 cells but no changes in p38. α-Mangostin also decreased phosphorylated Akt without altering total Akt. These results suggest that α-mangostin inhinbited cell proliferation and induced apoptosis through downregulation of ERK, JNK and Akt signaling pathway in human chondrosarcoma SW1353 cells.     

种衣剂对低温处理下棉花胚根及幼苗外部形态和超微结构的影响

以棉种‘新陆中54号’为材料,用3种种衣剂(棉1、棉2、棉3)包衣棉种后播种于塑料营养盒内,25℃恒温培养,分别在第4天(棉种长出胚根)和第7天(棉株幼苗)均进行5、10、15、20℃共4个低温处理,与各低温下未包衣种子(对照,CK)进行比较,低温处理24h后,观察各处理棉花胚根、幼苗外部形态和超微结构的变化,以期通过模拟新疆早春"倒春寒"发生特点,考察种衣剂对提高棉花耐寒性的功效。结果表明:20℃下种衣剂处理与CK无差异,种子萌发正常,发芽率在92.24%~95.51%,3种种衣剂包衣处理胚根生长量为3.66~3.81cm,幼苗叶色浓绿,茎杆直立,胚根细胞中线粒体结构完整,叶肉细胞中线粒体、叶绿体结构规则;15℃低温下种衣剂处理棉种发芽率较CK提高4.45~6.98个百分点,胚根生长速度下降,但包衣处理生长量较CK提高25.27%~36.05%,幼苗叶色浓绿,棉苗直立,胚根细胞中线粒体内脊清晰,叶肉细胞中叶绿体、线粒体结构清晰,细胞器结构和数量明显优于CK;10℃低温下棉种发芽受到抑制,但包衣处理较CK发芽率提高0.73~4.25个百分点,19.15%~42.55%的幼苗叶片下垂萎蔫,保持正常温度后种衣剂处理棉苗很快恢复到正常形态,胚根细胞中线粒体、内质网数目多于CK,叶肉细胞中叶绿体轮廓清晰,内含物较少;5℃低温下各处理棉种发芽率均低于50.00%,CK幼苗叶色脱水失绿,萎蔫下垂,萎蔫率达74.47%,叶绿体膨胀成圆球形、轮廓模糊,包衣处理幼苗萎蔫率在60.42%~67.45%,叶肉细胞中叶绿体结构完整,呈椭球型,线粒体结构较规则、内含物浑浊。研究表明种衣剂能促进低温处理下种子萌发、提高发芽率和胚根生长速度、保护棉苗外部形态和细胞超微结构稳定,维持正常生长,增强幼苗抵御低温的危害能力。     

Lucidenic acid B induces apoptosis in human leukemia cells via a mitochondria-mediated pathway

Ganoderma lucidum is known as a medicinal mushroom used in traditional Chinese medicine. In the present study, the effect of lucidenic acids (A, B, C, and N) isolated from a new G. lucidum (YK-02) on induction of cell apoptosis and the apoptotic pathway in HL-60 cells were investigated. The results demonstrated that lucidenic acids decreased cell population growth of HL-60 cells, assessed with the MTT assay. The cell cycle assay indicated that treatment of HL-60 cells with lucidenic acid A, C, and N caused cell cycle arrest in the G 1 phase. Lucidenic acid B (LAB) did not affect the cell cycle profile; however, it increased the number of early and late apoptotic cells but not necrotic cells. Treatment of HL-60 cells with LAB caused loss of mitochondria membrane potential. Moreover, the ratio of expression levels of pro- and antiapoptotic Bcl-2 family members was changed by LAB treatment. LAB-induced apoptosis involved release of mitochondria cytochrome c and subsequently induced the activation of caspase-9 and caspase-3, which were followed by cleavage of poly(ADP-ribose) polymerase (PARP). Pretreatment with a general caspase-9 inhibitor (Z-LEHD-FMK) and caspase-3 inhibitor (Z-DEVD-FMK) prevented LAB from inhibiting cell viability in HL-60 cells. Our finding may be critical to the chemopreventive potential of lucidenic acid B.     

Antitumor activity of capsaicin on human colon cancer cells in vitro and colo 205 tumor xenografts in vivo

Capsaicin was reported to inhibit cancer cell growth. The aim of this study was to evaluate the antitumor potential of capsaicin by studying antitumor activity in vitro as well as in vivo. The in vitro studies are to examine the effects of capsaicin on human colon cancer colo 205 cells after exposure to capsaicin. The results showed that capsaicin induced cytotoxic effects in a time- and dose-dependent manner and increased reactive oxygen species (ROS) and Ca(2+) but decreased the level of mitochondrial membrane potential (ΔΨ(m)) in colo 205 cells. Data from Western blotting analysis indicated that the levels of Fas, cytochrome c, and caspases were increased, leading to cell apoptosis. Capsaicin decreased the levels of anti-apoptotic proteins such as Bcl-2 and increased the levels of pro-apoptotic proteins such as Bax. Capsaicin-induced apoptosis in colo 205 cells was also done through the activations of caspase-8, -9 and -3. In vivo studies in immunodeficient nu/nu mice bearing colo 205 tumor xenografts showed that capsaicin effectively inhibited tumor growth. The potent in vitro and in vivo antitumor activities of capsaicin suggest that capsaicin might be developed for the treatment of human colon cancer.     

Aluminum toxicity in plant cells: Mechanisms of cell death and inhibition of cell elongation

Aluminum (Al) ions are a major constraint for crop productivity in acidic soils. The root apex is the most sensitive plant part to Al, which inhibits root elongation and causes cell death. To elucidate the mechanisms of these toxic events, Al responses have been investigated in cultured cell lines of tobacco (Nicotiana tabacum), SL and BY-2. These cells at the logarithmic growth phase serve as a model system of meristematic cells at the root apex. Our research group has revealed three types of cell death mechanisms triggered by Al: (i) Enhancement of iron (Fe)-mediated lipid peroxidation leading to a loss of plasma membrane integrity (plasma membrane pathway); (ii) dysfunction of mitochondria accompanied by ROS production (mitochondria pathway); and (iii) upregulation of NtVPE1 encoding a vacuolar processing enzyme (VPE), which leads to vacuolar collapse and the loss of plasma membrane integrity (vacuole pathway). Mechanisms (ii) and (iii) have been confirmed in root systems of pea and tobacco seedlings, respectively. The inhibition of elongation (expansion) in SL cells was detected as a decrease in water content, together with decreased osmolality and soluble sugar content, which was partly due to the inhibition of sucrose uptake by Al. The inhibition of root elongation by Al due to the inhibition of the sucrose transporter (SUT) NtSUT1 localized at the plasma membrane was confirmed in tobacco seedlings, in which overexpression of NtSUT1 mitigated both the inhibition of elongation and cell death at the root apex under Al stress.     

Monascuspiloin induces apoptosis and autophagic cell death in human prostate cancer cells via the Akt and AMPK signaling pathways

Monascus pigments have been reported to possess anticancer effects in various cancer cells; however, the molecular mechanisms of their anticancer properties remain largely unknown. Monascuspiloin is an analogue of the Monascus pigment monascin, and its anticancer growth activity against human prostate cancer cells was evaluated using in vitro and in vivo models. Monascuspiloin effectively inhibits the growth of both androgen-dependent LNCaP and androgen-independent PC-3 human prostate cancer cells. Monascuspiloin preferentially induces apoptosis in LNCaP cells by attenuating the PI3K/Akt/mTOR pathway. In androgen-independent PC-3 cells, monascuspiloin induces G2/M arrest and autophagic cell death by an AMPK-dependent pathway. Induction of autophagy in PC-3 cells further sensitizes cells to apoptosis induced by monascuspiloin. Monascuspiloin inhibits tumor growth in nude mice bearing PC-3 xenografts through induction of apoptosis and autophagy. This study is the first to demonstrate that monascuspiloin has therapeutic potential for the treatment of both androgen-dependent and -independent human prostate cancers.     

Benzyl isothiocyanate (BITC) induces G2/M phase arrest and apoptosis in human melanoma A375.S2 cells through reactive oxygen species (ROS) and both mitochondria-dependent and death receptor-mediated multiple signaling pathways

Benzyl isothiocyanates (BITC), a member of the isothiocyanate (ITC) family, inhibits cell growth and induces apoptosis in many types of human cancer cell lines. The present study investigated mechanisms underlying BITC-induced apoptosis in A375.S2 human melanoma cancer cells. To observe cell morphological changes and viability, flow cytometric assays, cell counting, and a contrast-phase microscopic examination were carried out in A375.S2 cells after BITC treatment. Cell cycle distribution and apoptosis were assessed with the analysis of cell cycle by flow cytometric assays, DAPI staining, propidium iodide (PI), and annexin V staining. Apoptosis-associated factors such as reactive oxygen species (ROS) formation, loss of mitochondrial membrane potential (ΔΨ(m)), intracellular Ca(2+) release, and caspase-3 activity were evaluated by flow cytometric assays. Abundance of cell cycle and apoptosis associated proteins was determined by Western blotting. AIF and Endo G expression was examined by confocal laser microscope. Results indicated that (1) BITC significantly reduced cell number and induced cell morphological changes in a dose-dependent manner in A375.S2 cells; (2) BITC induced arrest in cell cycle progression at G(2)/M phase through cyclin A, CDK1, CDC25C/Wee1-mediated pathways; (3) BITC induced apoptosis and increased sub-G(1) population; and (4) BITC promoted the production of ROS and Ca(2+) and loss of ΔΨ(m) and caspase-3 activity. Furthermore, BITC induced the down-regulation of Bcl-2 expression and induced up-regulation of Bax in A375.S2 cells. Moreover, BITC-induced cell death was decreased after pretreatment with N-acetyl-l-cysteine (NAC, a ROS scavenger) in A375.S2 cells. In conclusion, the results showed that BITC promoted the induction of G(2)/M phase arrest and apoptosis in A375.S2 human melanoma cells through ER stress- and mitochondria-dependent and death receptor-mediated multiple signaling pathways. These data suggest that BITC has potential as an agent for the treatment of melanoma.