Molecular mechanisms involved in chemoprevention of black raspberry extracts: from transcription factors to their target genes

Berries have attracted attention for their chemopreventive activities in last a few years. Dietary freeze-dried blackberries have been shown to reduce esophagus and colon cancer development induced by chemical carcinogen in rodents. To elucidate molecular mechanisms involved in chemoprevention by berry extracts, we employed mouse epidermal Cl 41 cell line, a well-characterized in vitro model in tumor promotion studies. Pretreatment of Cl 41 cells with methanol-extracted blackberry fraction RO-ME resulted in a dramatical inhibition of B(a)PDE-induced activation of AP-1 and NFkB, and expression of VEGF and COX-2. The inhibitory effects of RO-ME on B(a)PDE-induced activation of AP-1 and NFkappaB appear to be mediated via inhibition of MAPKs and IkappaBalpha phosphorylation, respectively. In view of the important roles of AP-1, NFkappaB, VEGF and COX-2 in tumor promotion/progression, and VEGF and COX-2 are target of AP-1 and NFkappaB, we anticipate that the ability of black raspberries to inhibit tumor development may be mediated by impairing signal transduction pathways leading to activation of AP-1 and NFkappaB, subsequently resulting in down-regulation of VEGF and COX-2 expression. The RO-ME fraction appears to be the major fraction responsible for the inhibitory activity of black raspberries.     

Development of in vitro systems for chemoprevention research

The C3H/10T1/2 mouse fibroblast cell line has been developed as a predictive model for cancer chemopreventive agents. The retinoids, which are currently being evaluated as chemopreventive agents in the clinic, are potent inhibitors or chemically induced neoplastic transformation in this cell line. Mechanistic studies suggest that retinoids stabilize chemically initiated cells and prevent their transformation by enhancing gap junctional communication between these cells and adjacent growth-inhibited normal 10T1/2 cells. Carotenoids also prevent chemically and physically induced neoplastic transformation of 10T1/2 cells. beta-Carotene is active without evidence of bioconversion to retinoids, implying that this dietary constituent has intrinsic chemopreventive activity. This cell culture system mimics many aspects of carcinogenesis in animals and man and appears well suited to mechanistic studies at the cellular and molecular level.     

米氏凯伦藻甲醇氯仿提取物的细胞毒性分析

目的研究米氏凯伦藻提取物对3株肿瘤细胞的增殖抑制作用,分析米氏凯伦藻对人类健康的可能威胁。方法以体外培养的人宫颈癌细胞HeLa、人肝癌细胞HepG2和人肺癌细胞A549为研究对象,采用MTT比色法检测米氏凯伦藻中提取物对3株细胞增殖的影响;观察毒素在不同时间(12、24、36和48h)下对肿瘤细胞增殖的抑制情况;采用免疫荧光染色法分析比较3株细胞膜上GM1的相对含量。结果米氏凯伦藻提取物对3种肿瘤细胞的增殖均具有显著的抑制作用。与肝癌细胞HepG2相比,宫颈癌细胞HeLa和肺癌细胞A549对其更为敏感(P<0.01)。肝癌细胞HepG2、宫颈癌细胞HeLa和肺癌细胞A549细胞膜上GM1的相对含量差异不大(P>0.05)。结论米氏凯伦藻提取物具有明显的细胞毒性,对人类健康存在潜在威胁。米氏凯伦藻提取物在细胞膜上作用靶点比较复杂。     

Ethanolic Extract of Bark from Salix aegyptiaca Ameliorates 1,2-dimethylhydrazine-induced Colon Carcinogenesis in Mice by Reducing Oxidative Stress

We have previously shown that ethanolic extract from bark (EEB) of Salix aegyptiaca (Musk Willow) can inhibit proliferation and motility and induce apoptosis in colon cancer cells. Tandem mass spectrometry revealed EEB to be rich in catechin, catechol, and salicin. The present study investigated the chemopreventive effect of HPLC-fingerprinted EEB on 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) formation in mice. DMH (20 mg/kg body weight) was weekly injected subcutaneously to mice for the first 2 weeks. EEB (100 and 400 mg/kg body weight) was provided orally from the 7th to 14th week, after which colon tissues were evaluated histologically and biochemically. DMH treatment induced high number of ACF; EEB significantly reduced the number and multiplicity of ACF, along with a restoration in goblet cells and mucin accumulation. EEB supplementation improved the markers of inflammation (myeloperoxidase and neutrophil infiltration) and oxidative stress. More importantly, EEB amplified apoptosis of neoplastic cells in the colon mucosa of DMH-treated mice. It also lowered levels of markers for early transformation events such as EGFR, nuclear β-catenin, and COX-2 in colon cancer cell lines HT-29 and HCT-116. The innocuity of EEB (up to 1600 mg/kg) to mice reinforces its potential as a chemopreventive agent.     

Differential Inhibition of UV-Induced Activation of NFκ B and AP-1 by Extracts From Black Raspberries,Strawberries, and Blueberries

Recent studies from our laboratory have shown that the transactivation of nuclear factor κ B (NFκ B) and activator protein-1 (AP-1) plays an important mechanistic role in ultraviolet (UV)-induced skin carcinogenesis in mice. We also demonstrated that a methanol extract (ME) fraction from black raspberries (Rubus occidentalis) (RO; RO-ME) inhibits benzo[a]pyrene-7,8-diol-9,10-epoxide [B(a)PDE]–induced activation of NFκ B and AP-1 in cultured mouse epidermal cells. In the present study, we determined if RO-ME might also inhibit the induction of NFκ B and AP-1 in mouse epidermal cells exposed to mid UV radiation (UVB) and short UV radiation (UVC) and whether methanol fractions from strawberries and blueberries would also be effective. Our results showed that RO-ME inhibited UVB-induced activation of NFκ B in mouse epidermal cells in a time- and dose-dependent manner; however, the methanol fractions from strawberries and blueberries were ineffective. Interestingly, none of the fractions from all 3 berry types inhibited UVB- or UVC-induced activation of AP-1, suggesting that inhibition of UV-induced signaling pathways is specific for black raspberries and NFκ B. Cyanidin-3-rutinoside, an anthocyanin found in abundance in black raspberries and not in strawberries or high-bush blueberries, was found to contribute to the inhibition of UVB-induced activation of NFκ B. These results suggest that berries differ in their ability to influence signaling pathways leading to activation of NFκ B and AP-1 when using UV light as the inducer.     

血清对DHA抑制肺癌A549细胞生长的影响及DHA的抗癌机制

目的研究血清对体外培养条件下二十二碳六稀酸(DHA)抑癌作用的影响及DHA的抗癌机制。方法采用MTT法观察血清刺激和无血清情况下DHA对体外培养的肺癌A549细胞的生长抑制作用,同时采用免疫印迹方法检测DHA对血清诱导的蛋白激酶B(Akt)磷酸化的影响。结果在无血清和低浓度血清(<2%)下,DHA明显抑制A549细胞的生长;在高浓度血清下,DHA则呈现促进A549生长的作用。无血清下,DHA对血清诱导的Akt的活化具有抑制作用。结论体外培养条件下,培养基中无血清时DHA可能通过脂质过氧化降低Akt的活化、抑制A549细胞的生长;高血清含量则明显干扰DHA的抗癌活性。     

Differential inhibition of UV-induced activation of NF kappa B and AP-1 by extracts from black raspberries, strawberries, and blueberries

Recent studies from our laboratory have shown that the transactivation of nuclear factor kappa B (NF kappa B) and activator protein-1 (AP-1) plays an important mechanistic role in ultraviolet (UV)-induced skin carcinogenesis in mice. We also demonstrated that a methanol extract (ME) fraction from black raspberries (Rubus occidentalis) (RO; RO-ME) inhibits benzo[a]pyrene-7,8-diol-9,10-epoxide [B(a)PDE]-induced activation of NF kappa B and AP-1 in cultured mouse epidermal cells. In the present study, we determined if RO-ME might also inhibit the induction of NF kappa B and AP-1 in mouse epidermal cells exposed to mid UV radiation (UVB) and short UV radiation (UVC) and whether methanol fractions from strawberries and blueberries would also be effective. Our results showed that RO-ME inhibited UVB-induced activation of NF kappa B in mouse epidermal cells in a time- and dose-dependent manner; however, the methanol fractions from strawberries and blueberries were ineffective. Interestingly, none of the fractions from all 3 berry types inhibited UVB- or UVC-induced activation of AP-1, suggesting that inhibition of UV-induced signaling pathways is specific for black raspberries and NF kappa B. Cyanidin-3-rutinoside, an anthocyanin found in abundance in black raspberries and not in strawberries or high-bush blueberries, was found to contribute to the inhibition of UVB-induced activation of NF kappa B. These results suggest that berries differ in their ability to influence signaling pathways leading to activation of NF kappa B and AP-1 when using UV light as the inducer.     

ERK及AP-1对二氧化硅上调人肺上皮细胞纤溶酶原激活物抑制因子-1表达的作用

目的 探讨细胞外信号调控激酶(ERK)/激活蛋白(AP-1)信号通路在二氧化硅诱导人肺上皮细胞(A549)纤溶酶原激活物抑制因子-1(PAI-1)表达中的作用.方法 以人肺上皮细胞A549为研究对象,200 μg/ml二氧化硅刺激0-24h.干预实验采用姜黄素预处理以及c-Jun显性负性突变体(TAM67)瞬时转染阻断AP-1活性;PD98059预处理阻断ERK活性.以Western印迹检测ERK激酶活力、PAI-1蛋白表达,EMSA检测AP-I DNA结合活性.结果 (1)SiO2作用A549细胞4、8、16 h,AP-1DNA结合活性分别为对照的1.3、1.3、2.1倍,差异有统计学意义(P＜0.05);10、25、50μmol/L浓度姜黄素对二氧化硅诱导的PAI.1蛋白表达抑制率分别为20%、63%、65%,差异有统计学意义(P＜0.05);TAM-67对二氧化硅诱导的PAI.1蛋白表达的抑制率为59%,与二氧化硅刺激组比,差异有统计学意义(P＜0.05).(2)二氧化硅作用A549细胞诱导ERK激酶活化;PD98059对二氧化硅诱导的PAI-1蛋白表达的抑制率为51%,与二氧化硅刺激组比较,差异有统计学意义(P＜0.05).(3)PD98059对二氧化硅诱导的AP-1 DNA结合活性的抑制率为73%,与二氧化硅刺激组比较,差异有统计学意义(P＜0.05).结论 ERK/AP-1信号通路参与调控SiO2诱导的人肺上皮细胞PAl-1蛋白表达.     

Plant-Derived Protease Inhibitors LC-pi (Lavatera cashmeriana) Inhibit Human Lung Cancer Cell Proliferation In Vitro

The objective of this study was to check the anticancer activity of purified protease inhibitors of Lavatera cashmeriana viz LC-pi I, II, III, and IV (Lavatera cashmeriana protease inhibitors) on A549 (lung) cell. It was found that LC-pi I and II significantly inhibited the proliferation of A549 cells with IC₅₀ value of 54 μg/ml and 38μg/ml, respectively, whereas inhibition by LC-pi III and IV was negligible. LC-pi I and II were further found to inhibit formation of colonies in a dose-dependent manner. Also, both inhibitors were found to induce apoptosis causing chromatin condensation and DNA fragmentation, without loss of mitochondrial membrane potential. Cell cycle revealed a significant increase of subG₀/G₁ phase cells that are apoptotic cells. We also demonstrated a dose-dependent decrease in migration of A549 cells on cell migration assay by both inhibitors. Taken together, we demonstrate that LC-pi I and II inhibited proliferation through arresting cells before apoptosis, inducing apoptosis and inhibiting cell migration in human lung cancer cells, but the study warrants further investigation. Our results support the notion that plant protease inhibitors may have the potential to advance as chemopreventive agents.     

莱菔硫烷对膀胱癌细胞增殖抑制作用

目的 研究丝裂原活化蛋白激酶(MAPKs)和磷脂酰肌醇激酶(PI3K)信号途径在莱菔硫烷(sulforaphane,SFN)抑制膀胱癌细胞增殖中的作用。方法噻唑蓝(MTT)法测定膀胱癌细胞的增殖作用,用实时定量PCR方法(re-al time-PCR)测定对环氧化酶(COX-2)mRNA的影响。结果 5～20μmol/L莱菔硫烷能明显抑制膀胱癌细胞的体外增殖、COX-2 mRNA表达;SB202190或LY294002预处理T24细胞,能明显降低莱菔硫烷对T24细胞增殖的抑制作用,提高细胞存活率;SB202190预处理T24细胞1h能完全阻断莱菔硫烷对COX-2 mRNA的抑制作用,而LY294002不影响莱菔硫烷对COX-2 mRNA的抑制作用。结论 莱菔硫烷可能是通过活化p38激酶途径和PI3K激酶途径抑制膀胱癌细胞生长,p38激酶信号途径在SFN抑制COX-2 mRNA中起关键作用。     

Antiproliferative and proapoptotic activity of Turkish propolis on human lung cancer cell line

Cancer is a heterogeneous disease, two of whose characteristic features are uncontrollable cell proliferation and insufficient apoptosis. Various studies have investigated the antiproliferative effects of propolis, a natural bee product, from different countries, and its cytotoxic effects have been attributed to its polyphenol contents. The purpose of this study was to show the cytotoxic effects, and possible mechanisms involved, of ethanolic extract of Turkish propolis (EEP) on the human lung cancer (A549) cell line. Cytotoxic activity of EEP on A549 cells was revealed using the MTT assay. Mechanisms involved in the cytotoxic action of EEP on A549 cells were then investigated in terms of apoptosis, mitochondrial membrane potential and cell cycle using flow cytometry, endoplasmic reticulum stress using RT-PCR, and caspase activity using luminometric analysis. EEP exhibited selective toxicity against A549 cells compared to normal fibroblast cells. We determined that EEP arrested the cell cycle of A549 cells at the G₁ phase, induced endoplasmic reticulum stress, caspase activity, and apoptosis and reduced mitochondrial membrane potential. These results indicate that Turkish propolis is capable of reducing cancer cell proliferation and may have a promising role to play in the development of new anticancer drugs in the future.     

Neoplastic transformation of BALB/3T3 cells and cell cycle of HL-60 cells are inhibited by mango (Mangifera indica L.) juice and mango juice extracts

The mango, Mangifera indica L., is a fruit with high levels of phytochemicals, suggesting that it might have chemopreventative properties. In this study, whole mango juice and juice extracts were screened for antioxidant and anticancer activity. Antioxidant activity of the mango juice and juice extracts was measured by 3 standard in vitro methods. The results of the 3 methods were in general agreement, although different radicals were measured in each. Anticancer activity was measured by examining the effect on cell cycle kinetics and the ability to inhibit chemically induced neoplastic transformation of mammalian cell lines. Incubation of HL-60 cells with whole mango juice and mango juice fractions resulted in an inhibition of the cell cycle in the G(0)/G(1) phase. A fraction of the eluted mango juice with low peroxyl radical scavenging ability was most effective in arresting cells in the G(0)/G(1) phase. Whole mango juice was effective in reducing the number of transformed foci in the neoplastic transformation assay in a dose-dependent manner. These techniques provide valuable screening tools for health benefits derived from mango phytochemicals.     

Suppression by Geraniol of the Growth of A549 Human Lung Adenocarcinoma Cells and Inhibition of the Mevalonate Pathway in Culture and In Vivo: Potential Use in Cancer Chemotherapy

Geraniol (G)—a natural compound present in the essential oils of many aromatic plants—has attracted interest for its potential antitumor effects. The molecular mechanisms of the growth inhibition and apoptosis induced by G in cancer cells, however, remain unclear. In this study, we investigated the effects of G on cell proliferation in culture in A549 cells and in vivo in those same tumor cells implanted in nude mice fed diets supplemented with 25, 50, and 75 mmol G/kg. We demonstrated that G caused a dose- and time-dependent growth inhibition of A549 cells and tumor growth in vivo along with an induction of apoptosis. Moreover, further in vivo assays indicated that G decreased the levels of 3-hydroxymethylglutarylcoenzyme-A reductase—the rate-limiting enzyme in cholesterogenesis—in a dose-dependent manner along with cholesterogenesis and cholesterolemia in addition to reducing the amount of membrane-bound Ras protein. These results showed that the doses of G used in this work, though nontoxic to animals, clearly inhibited the mevalonate pathway, which is closely linked to cell proliferation and increased apoptosis in A549 tumors, but not in normal mouse-liver cells. Accordingly, we suggest that G displays significant antitumor activity and should be a promising candidate for cancer chemotherapy.     

ω-3多不饱和脂肪酸廿烷五烯酸单剂以及联合卡铂对人肺腺癌A-549细胞系增殖和凋亡的影响

目的观察廿烷五烯酸（EPA）单剂以及与卡铂联合应用对人肺腺癌A-549细胞系增殖和凋亡的影响。方法分别用100μg／ml卡铂、80μg／mlEPA以及100μg／ml卡铂联合80μg／mlEPA孵育A-549细胞48h后,采用MTr法检测药物对h-549细胞增殖的抑制率,HE染色观察细胞形态学,流式细胞术定量分析细胞凋亡率。结果100μg／ml卡铂联合80μg／mlEPA对A-549细胞系的增殖抑制率为85．20％±5．00％,显著高于80μg／mlEPA（32．85％±3．00％,P=0．0001）或100μg／ml卡铂（53．25％±3．00％,P=0．0013）单独的作用。HE染色显示：药物干预后部分A-549细胞出现凋亡形态学改变。卡铂联合EPA组A-549细胞凋亡率为17．05％4-4．00％,显著高于单用卡铂组（9．49％±1．00％,P20．0252）。结论EPA可能具有增强卡铂抑制人肺腺癌A-549细胞系增殖、促进A-549细胞系凋亡的作用。     

Inhibitory Effect of Liquiritigenin on Migration Via Downregulation ProMMP-2 and PI3K/Akt Signaling Pathway in Human Lung Adenocarcinoma A549 cells

Liquiritigenin (LQ) is a flavanone extracted from Glycyrrhizae, which has multiple biological effects, such as antiinflammation and anticancer. This study is the first to investigate the effect of LQ on the migration of human lung adenocarcinoma A549 cells in vitro. First, LQ exhibited inhibitory effects on the adhesion and migration of A549 cells in the absence of cytotoxicity. Gelatin zymography and Western blot analysis showed that LQ significantly reduced the expression of promatrix metalloproteinase-2 (proMMP-2) in A549 cells in terms of both activity and protein level. Second, LQ inhibited the phosphorylation of Akt and activated the phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). Furthermore, the treatment of inhibitors specific for Akt (LY294002) and ERK1/2 (U0126) to A549 cells resulted in reduced activity of proMMP-2. These results suggested that the inhibition on proMMP-2 expression by LQ may be through suppression on PI3K/Akt signaling pathway, which in turn led to the inhibition of lung adenocarcinoma A549 cells migration. However, activation of ERK might not be involved in the regulation of proMMP-2. Taken together, LQ may be considered as a potential interfering agent of cancer progression.     

Antioxidant,Anti-inflammatory,and Genomic Stability Enhancement Effects of Zinc l-carnosine: A Potential Cancer Chemopreventive Agent?

Cancer is one of the major causes of death worldwide, and the incidence and mortality rates of cancer are expected to rise tremendously in the near future. Despite a better understanding of cancer biology and advancement in cancer management, current strategies in cancer treatment remain costly and ineffective. Hence, instead of putting more efforts to search for new cancer cures, attention has now been shifted to the development of cancer chemopreventive agents as a preventive measure for cancer formation. It is well known that neoplastic transformation of cells is multifactorial, and the occurrence of oxidative stress, chronic inflammation, and genomic instability events has been implicated in the carcinogenesis of cells. Zinc l-carnosine (ZnC), which is clinically used as gastric ulcer treatment in Japan, has been suggested to have the potential in preventing cancer development. Multiple studies have revealed that ZnC possesses potent antioxidant, anti-inflammatory, and genomic stability enhancement effects. Thus, this review provides some mechanistic insight into the antioxidant, anti-inflammatory, and genomic stability enhancement effects of ZnC in relevance to its chemopreventive potential.