槲寄生凝集素对人结肠癌HT-29细胞增殖及凋亡的影响

目的：研究槲寄生凝集素对人结肠癌HT-29细胞增殖和凋亡的影响。方法：采用MTT法观察槲寄生凝集素对体外培养的人结肠癌HT-29细胞增殖的影响,运用基因组DNA电泳观察凋亡特征性“梯状”条带及原位末端标记法检测槲寄生凝集素诱导HT-29细胞凋亡。结果：槲寄生凝集素对体外培养的人结肠癌HT-29细胞抑制作用表现出时间和剂量依赖性。基因组DNA琼脂糖凝胶电泳显示槲寄生凝集素作用于HT-29细胞后出现凋亡细胞特有的DNA阶梯状条带。原位末端标记法检测显示槲寄生凝集素可明显诱导HT-29细胞的凋亡。结论：槲寄生凝集素可抑制人结肠癌HT-29细胞生长并诱导其凋亡。     

槲寄生凝集素腹腔内给药对腹腔巨噬细胞功能的影响

目的：探讨小鼠腹腔内注射槲寄生凝集素对腹腔巨噬细胞功能的影响。方法：16只小鼠分为腹腔内给药组和空白组,分别取腹腔内巨噬细胞并计数,采用ELISA法测定TNF-α表达情况,Griess法测定NO表达,MTT法检测腹腔内巨噬细胞对肠癌HCT116细胞的杀伤作用。结果：腹腔内给槲寄生凝集素后可明显增加腹腔内巨噬细胞数,并增加TNF—α和NO的表达水平;激活的巨噬细胞对HCT116细胞的杀伤作用增强,其杀伤作用与TNF—α和NO表达时间一致。结论：腹腔内注射槲寄生凝集素可激活腹腔内巨噬细胞,激活的巨噬细胞对HCT116细胞有杀伤作用。     

槲寄生凝集素抑制人大肠癌HCT116细胞环氧化酶-2表达的研究

目的：探讨槲寄生凝集素对人大肠癌HCT116细胞环氧化酶（COX-2）表达的影响。方法：采用RT-PCR、Western blotting和ELISA等方法检测不同浓度（0.1～1mg/L）槲寄生凝集素对细胞COX-2及其产物前列腺素E2（PGE2）表达的影响。结果：槲寄生凝集素可抑制HCT116细胞的COX-2mRNA、蛋白表达及PGE2的水平,其抑制COX-2蛋白的表达与PGE2的水平相一致,只在大剂量（1mg/L）时对COX-1mRNA有抑制作用。结论：槲寄生凝集素具有抑制HCT116细胞的COX-2基因转录、蛋白表达和功能活性等作用,在一定浓度（0.1～1mg/L）和时间范围（3～24h）内,表现出时效与量效关系。     

槲寄生类植物抗肿瘤活性蛋白成分的结构、功能及其作用机制的研究进展

槲寄生毒肽和槲寄生凝集素在选择性摧毁癌细胞、阻断癌症的发生和发展方面有独特的作用。槲寄生凝集素特殊的生物活性及作用方式 ,使其有可能成为基因疗法等未来治疗药物“导入”的载体受到重视。此文就槲寄生提取物的功能、主要抗癌活性蛋白成分的分离纯化、性质、分子结构、生物学功能及其机理的研究进展及应用前景作了简要讨论     

白果槲寄生鲜果提取物中的多糖及其与该植物中凝集素I的相互作用

白果槲寄生Viscum album L.提取物或单用或与常规抗癌药合用治疗癌症。该植物中凝集素Ⅰ(VAAI)及一种多糖rhamnogalac-turonan可增强天然杀伤细胞对肿瘤细胞的细胞毒活性。作者研究了该植物鲜果提取物中多糖的结构特征及它们与VAAI的结合能力。     

槲寄生抗心律失常作用的细胞电生理研究

用玻璃微电极及选择性膜通道阻滞剂观察了槲寄生注射液对离体狗心脏浦氏细胞及豚鼠心室肌细胞快反应动作电位的影响。结果表明槲寄生能加速动作电位复极进程,使ERP/APD比值增加,不应期相对延长,该作用与抑制细胞膜I_(si)及增加I_x有关。     

槲寄生抗心律失常作用的细胞生理研究

用玻璃微电极及选择性膜通道阻滞剂观察了槲寄生注射液对离体狗心脏浦氏细胞及豚鼠心室肌细胞快反应作电位的影响。结果表明槲寄生能加速动作电位复极进程，使ＥＲＰ／ＡＰＤ比值增加，不应期相对延长作用与抑制细胞膜Ｌｓｉ及增加Ｉｘ有关。     

槲寄生抗肿瘤有效成分研究进展

槲寄生类植物具有较好的抗肿瘤活性,其主要抗肿瘤活性成分为凝集素类和生物碱类.对这2类活性成分的分离纯化、结构与活性以及槲寄生制剂的临床试验的研究进展作了综述.     

槲寄生碱影响Ras蛋白表达抑制肺癌H358细胞增殖

目的研究槲寄生碱对非小细胞肺癌H358细胞的抑制作用及其相关作用机制。方法采用MTT法检测槲寄生碱对H358细胞增殖的抑制作用;采用流式细胞仪检测槲寄生碱对H358细胞凋亡的影响;采用Western blot方法检测槲寄生碱对K-Ras、Bcl-2和Bax等蛋白表达的影响;测定caspase 3、caspase 8和caspase 9的活性;检测槲寄生碱在体内的抑瘤活性。结果槲寄生碱以质量浓度依赖的方式抑制H358细胞增殖,并能有效地诱导H358细胞凋亡;caspase 3、caspase 8和caspase 9受到了不同程度的激活;同时,槲寄生碱抑制K-Ras和Bcl-2的表达,而对Bax没有明显抑制作用;槲寄生碱在体内也表现出明显的抑瘤活性。结论槲寄生碱在体外能够抑制H358细胞增殖并诱导H358细胞凋亡,为K-Ras突变型非小细胞肺癌等肿瘤疾病的治疗奠定了实验基础。     

尿素注射液对体内外肿瘤细胞杀伤作用的实验研究

探讨尿素注射液对体内外肿瘤细胞杀伤率和尿素静脉注射对机体代谢的影响。取处于生长期的胃癌823细胞株，加入尿素注射液观察72h，根据细胞形态和LDH的释放量确定杀伤效果。对致瘤小鼠腹腔注射尿素观察抑制肿瘤效果；家兔静脉注射尿素液观察对体内生化代谢指标的影响。适当浓度尿素注射液在一定时间内可大量杀伤肿瘤细胞，体内观察该药对致瘤小鼠能明显杀伤肿瘤细胞，延长动物生存时间，该药对体内生化代谢指标可产生一定影响。尿素注射液对体内外肿瘤细胞均有杀伤作用，杀伤效果与浓度成正相关，该药静脉注射对体内生化代谢指标有一定影响。     

Activation of caspase cascades in Korean mistletoe (Viscum album var. coloratum) lectin-II-induced apoptosis of human myeloleukemic U937 cells

Mistletoe lectins are of high biological activity and exert cytotoxic effects. We have previously shown that Korean mistletoe, Viscum album var. coloratum, lectin-II specifically induces apoptotic cell death in cancer cells, not normal lymphocytes. The destructive mechanism by mistletoe lectins on tumor cells was mediated by activation of c-JUN N-terminal kinase (JNK)/stress-activated protein kinase. Herein, we investigated the involvement of caspase cascade and its proteolytic cleavage effects on biosubstrates of human myeloleukemic U937 cells by D-galactoside and N-acetyl-galactosamine-specific Korean mistletoe lectin-II. Mistletoe lectin-II induced ladder pattern DNA fragmentation and activation of caspase-3, -8, and -9 of U937 cells, but not caspase-1 protease, in a time- and dose-dependent manner. Consistent with catalytic activation of protease, both poly(ADP-ribose) polymerase (PARP) and protein kinase C-delta (PKC-delta) are also cleaved in mistletoe lectin-II-treated U937 cells. An inhibitor of caspase-3-like protease, DEVD-CHO peptide, significantly inhibited mistletoe lectin-II-induced apoptosis, PARP cleavage, and fragmentation of DNA. These results provide the evidence that Korean mistletoe lectin-II induces apoptotic death of U937 cells via activation of caspase cascades.     

Transport of mistletoe lectin by M cells in human intestinal follicle-associated epithelium (FAE) <Emphasis Type="Italic">In vitro</Emphasis>

Purified mistletoe lectins are known to have cytotoxic and stimulating activities in the immune system. Mistletoe extract has been given subcutaneously because of its unstablity and poor absorption in the Gastrointestinal (GI) tract. A hallmark of M cells is their capacity to internalize material from the lumen and to transfer it efficiently to the underlying lymphoid cells. Although lectins are the prime candidates for oral vaccine delivery, the mechanisms whereby lectins are taken up, transported by M cells, and affect underlying immune cells remain poorly understood. In this study, uptake mechanism of Korean mistletoe lectin (Viscum album L. var. coloratum aggulutinin, VCA) across the human FAE (follicle associated epithelium) was investigated. An inverted FAE model of co-culture was obtained by a co-culture system of Caco-2 cells and human Raji B lymphocytes, and VCA transport across the in vitro model of human FAE was investigated. There was a greater transport of VCA across FAE monolayer cells than that of Caco-2 monolayer cells. These observations will be useful to assess the transport of other orally administered material in the GI tract.     

Identity of the N-terminal sequences of the three A chains of mistletoe (Viscum album L.) lectins: homology with ricin-like plant toxins and single-chain ribosome-inhibiting proteins.

Mistletoe lectin (ML) I increases the production of cytokines by mononuclear cells and has been proposed as a useful biological response modifier in the treatment of cancer. Two other lectins, ML II and ML III, have been identified in mistletoe. We report that the N-terminal sequences of the three A chains of ML I, ML II and ML III are identical, and have interesting homology with the N-terminal sequences of the A chain of ricin-like toxins and of single-chain ribosome-inhibiting proteins. In addition, the three mistletoe lectins inhibit the growth of the human tumor cell line Molt 4, ML III being the most potent. followed by ML II and ML I. This inhibition is suppressed by addition of rabbit anti-ML I antibodies to the cultured cells. The data obtained suggest that the three lectins have amino acid sequences which show extensive homology and exert very similar biological effects. They may be derived from the same precursor.     

Detection and quantitative determination of lectins and viscotoxins in mistletoe preparations

Mistletoe lectins and viscotoxins, which up to now have been isolated only from plant material, were detected and quantitatively determined in the mistletoe preparation Iscador and in a fermented mistletoe extract. Lectins were isolated by affinity chromatography and analyzed by isoelectric focussing. Thus, in Iscador and in the fermented mistletoe extract only the mistletoe lectins ML II/III were found whereas typical proteins of the ML I complex were missing. The lectin content of the preparation and the extract was determined by "single radial immunodiffusion" (SRID). For identification and quantitative determination of viscotoxins, a HPLC method was designed.     

Human cancer cells exhibit in vitro individual receptiveness towards different mistletoe extracts

In vitro cytotoxic effects of three aqueous mistletoe extracts on cell physiology against different human tumor cell lines and primary cancer cells were investigated in order to compare the receptiveness of different cancer cells against different mistletoe products. Therefore cell proliferation (BrdU-incorporation assay), mitochondrial activity (MTT-testing) and necrotic cell toxicity (LDH assay) were assayed over serial dilutions of the test products. Data obtained with HELA-S3, MOLT-4, MFM-223, COR-L51, KPL-1 and VM-CUB1 tumor cell lines and Iscador M (20 mg/ml), Iscador Q (20 mg/ml) and Abnobaviscum Fraxini -2 (20 mg/ml) indicated significant growth-inhibition of all cell lines, but also different cell susceptibilities against the different extracts. These variations were not only monitored on established cell lines but also on primary mamma carcinoma cells from surgical resectates. Concerning cell proliferation and mitochondrial activity Abnobaviscum Fraxini exhibits stronger inhibitory effects compared to products from the Iscador series. In case the evaluation was standardized on the active contents of VAA-I within the different products, the Iscador extracts possess higher cytotoxic activity. Pure viscotoxins and mistletoe lectins exhibited less effects than the extracts. The simultaneous presence of pure mistletoe lectins and mistletoe polysaccharides diminished the VAA-mediated cytotoxic effects. The presence of fetal calf serum (FCS) in cultivation media during in vitro testing diminished the cytotoxic effects of mistletoe extracts. It was shown that in vivo application of mistletoe preparations led to the formation of antibodies against unknown compounds of the extracts, diminishing the cytotoxic effect.     

Synergism between lectins and vesicles of Viscum album L.- detection by biochemical and immunological methods

Mistletoe (Viscum album L.) extracts, used in cancer therapy, contain several antitumor and immunologically active ingredients of which the cytotoxic mistletoe lectins and the immunoactive vesicles of chloroplast membranes are particularly important. We have investigated interactions between vesicles and lectins with respect to the question of synergistic or antagonistic effects. First we used biochemical methods. Lectin binding to vesicles was dependent on the pH-value and ionic strength of the buffers used. The strongest interaction was observed at low pH-values and at low ionic strength. Using immunological methods, we found that the combination of lectins and vesicles showed a strong amplifying synergistic effect on the stimulation of lymphocyte proliferation. We found an antagonistic effect in terms of cytotoxicity. In summary, these results demonstrate a significant influence of vesicles on all commonly used methods of determination of mistletoe lectins.     

Influence of carbohydrates on the cytotoxicity of an aqueous mistletoe drug and of purified mistletoe lectins tested on human T-leukemia cells

Partially and highly purified lectins from Viscum album L. (mistletoe) cause a dose-dependent decrease of viability of human leukemia cell cultures, MOLT-4, after 72 h treatment. The LC50 of the partially purified lectin was 27.8 ng/ml, of the highly purified lectin 1.3 ng/ml. Compared to the highly purified lectin a 140-fold higher protein concentration of an aqueous mistletoe drug was required to obtain similar cytotoxic effects on MOLT-4 cells. Cytotoxicity of the highly purified lectin was preferentially inhibited by D-galactose and lactose, cytotoxicity of the mistletoe drug and the partially purified lectin were preferentially inhibited by lactose and N-acetyl-D-galactosamine (GalNAc). Two lectin fractions with almost the same cytotoxic activity on MOLT-4 cells but with different carbohydrate affinities were isolated by affinity chromatography from the mistletoe drug: mistletoe lectin I with an affinity to D-galactose and GalNAc and mistletoe lectin II with an affinity to GalNAc. The lectin fractions and the mistletoe drug inhibited protein synthesis of MOLT-4 cells stronger than DNA synthesis. Furthermore a subpopulation of MOLT-4, resistant to cytotoxic doses of both the mistletoe drug and the mistletoe lectins, was shown to exhibit a reduced amount of GalNAc and N-acetyl-D-glucosamine in their cellular glycoproteins which are probably responsible for the binding of the cytotoxic lectins. These results indicate that lectins are the main toxins in the mistletoe drug.     

自噬对肝癌HepG2细胞增殖及对细胞周期影响的研究

目的研究用诱导肝癌HepG2细胞自噬与抑制肝癌HepG2细胞自噬的方法检测自噬对肝癌HepG2细胞增殖的影响,阐明细胞自噬的发生与细胞周期的关系。方法常规培养肝癌HepG2细胞,应用MTT比色法和流式细胞仪检测肝癌HepG2细胞增殖抑制率及细胞周期各时相的变化。结果自噬诱导剂雷帕霉素组的肝癌HepG2细胞抑制率明显高于对照组（P〈0.05）,对照组的肝癌HepG2细胞抑制率明显高于自噬抑制剂3-MA组（P〈0.05）;流式细胞仪分析示自噬诱导剂雷帕霉素组细胞周期中G1期细胞增多,S期细胞减少,G2/M期细胞相对增多（P〈0.05）。自噬抑制剂3-MA组细胞周期中G1期细胞减少,S期细胞增多,G2/M期细胞相对减少（P〈0.05）。结论自噬对肝癌HepG2细胞增殖有抑制作用,自噬不利于肝癌HepG2细胞成活。肝癌HepG2细胞自噬的发生多停留在细胞周期的G1期。     

Release of cytokines by a fermented lectin-1 (ML-1) free mistletoe extract reflects differences in the reactivity of PBMC in healthy and allergic individuals and tumour patients

Objective: Mistletoe extracts are used in adjuvant cancer treatment, but little is known concerning their mode of action. There is, however, evidence that antigens in these extracts may stimulate cells of the immune system, thereby modifying the altered immunological reactivity in tumour patients. Methods: In order to find out whether the postulated immunomodulatory properties of mistletoe extracts are mediated by cytokines, a spectrum of different cytokines was analysed in the supernatants of peripheral blood mononuclear cells (PBMC) from healthy (n = 23) and allergic (n = 16) individuals after stimulation with the fermented mistletoe lectin-1 (ML-1) free mistletoe extract Iscador Pini (IP) in vitro, and their cytokine patterns were compared to those from tumour patients with either breast cancer (n = 20) or colorectal tumours (n = 22). Results: PBMC from healthy and allergic individuals produced high levels of TNF-α and IL-6 and to a lesser extent Th1- and Th2-related cytokines. This finding was in contrast to data obtained in tumour patients. Thus, the concentration of TNF-α was significantly lower in the cell cultures from breast cancer patients than in controls, and patients with colorectal tumours released IFN-γ/IL-2 (5%) in the supernatants significantly less frequently than PBMC from healthy controls (26%). Similar results were obtained when the Th1- and monocyte/macrophage-related cytokines were analysed in the unstimulated cell cultures. Conclusions: These in vitro studies provide evidence that there is a reduced immunological reactivity to the fermented ML-1 free mistletoe extract in tumour patients and may give some clues as to how mistletoe-derived antigens could act on immune cells involved in the tumour defence. Received: 18 March 1996/Accepted in revised form: 18 July 1996     

Absence of tumor growth stimulation in a panel of 16 human tumor cell lines by mistletoe extracts in vitro

Extracts of Viscum album (mistletoe) are widely used as complementary cancer therapies in Europe. The mistletoe lectins have been identified as the main active principle of mistletoe extracts. They have been shown to exhibit cytotoxic effects as well as immunomodulatory activities. The latter is exemplified by induction of cytokine secretion and increased activity of natural killer cells. Recent reports, however, indicated possible tumor growth stimulation by mistletoe extracts. Therefore, the three aqueous mistletoe extracts (Iscador M special, Iscador Qu special and Iscador P) were evaluated for antiproliferative and/or stimulatory effects in a panel of 16 human tumor cell lines in vitro using a cellular proliferation assay. The results show no evidence of stimulation of tumor growth by any of the three Iscador preparations, comprising central nervous system, gastric, non-small cell lung, mammary, prostate, renal and uterine cancer cell lines, as well as cell lines from hematological malignancies and melanomas. On the contrary, Iscador preparations containing a high lectin concentration (Iscador M special and Iscador Qu special) showed antitumor activity in the mammary cancer cell line MAXF 401NL at the 15 microg/ml dose level with a more than 70% growth inhibition compared to untreated control cells. In addition, a slight antitumor activity (growth inhibition 30-70%) was found in three tumor cell lines for Iscador M special and in seven tumor cell lines for Iscador Qu special, respectively. Iscador P, which contains no mistletoe lectin I, showed no antiproliferative activity.