Plant lectins: potential antineoplastic drugs from bench to clinic.

Plant lectins, carbohydrate-binding proteins distributed widely in a variety of plant species, have drawn a rising attention for cancer biologists due to their remarkable anti-tumour properties. In this review, we present a brief outline of the up-to-date advances of plant lectins in elucidating their complex anti-cancer mechanisms implicated in apoptosis and autophagy. In addition, we further discuss the pre-clinical and clinical studies of plant lectins for their potential therapeutic applications. In conclusion, these inspiring findings would open a new perspective for plant lectins as potential antineoplastic drugs from bench to clinic.

Induction of apoptosis by Polygonatum odoratum lectin and its molecular mechanisms in murine fibrosarcoma L929 cells.

BACKGROUND: The Galanthus nivalis agglutinin (GNA)-related lectins have been reported to bear antiproliferative and apoptosis-inducing activities in cancer cells; however, the precise mechanisms by which GNA-related lectins induce cell death are still only rudimentarily understood. METHODS: In the present study, Polygonatum odoratum lectin (designated POL), a mannose-binding specific GNA-related lectin, possessed a remarkable antiproliferative activity toward murine fibrosarcoma L929 cells. And, this lectin induced L929 cell apoptosis in a caspase-dependent manner. In addition, POL treatment increased the levels of FasL and Fas-Associated protein with Death Domain (FADD) proteins and resulted in caspase-8 activation. Also, POL treatment caused mitochondrial transmembrane potential collapse and cytochrome c release, leading to activations of caspase-9 and caspase-3. Moreover, POL treatment enhanced tumor necrosis factor alpha (TNFalpha)-induced L929 cell apoptosis. RESULTS: Our data demonstrate for the first time that this lectin induces apoptosis through both death-receptor and mitochondrial pathways, as well as amplifies TNFalpha-induced L929 cell apoptosis. GENERAL SIGNIFICANCE: These inspiring findings would provide new molecular basis for further understanding cell death mechanisms of the Galanthus nivalis agglutinin (GNA)-related lectins in future cancer investigations.

Molecular mechanisms of Polygonatum cyrtonema lectin-induced apoptosis and autophagy in cancer cells.

Polygonatum cyrtonema lectin (PCL), a mannose/sialic acid-binding lectin, has been reported to display remarkable inhibitory and cytotoxic activity toward cancer cells. However, the precise mechanism by which PCL induces tumor cell death is still only rudimentarily understood. In the present study, PCL was shown to markedly inhibit the growth of human melanoma A375 cells with concomitant low toxicity to the normal melanocytes. Subsequently, PCL was found to simultaneously induce A375 cell apoptosis and autophagy. The mechanism of apoptosis following treatment with PCL involved regulation of Bax, Bcl-x(L) and Bcl-2 proteins, which then caused collapse of the mitochondrial membrane potential, leading to cytochrome c release and caspase activation. The treatment with PCL also abrogated the glutathione antioxidant system, and induced mitochondria to generate massive ROS accumulation, which subsequently resulted in p38 and p53 activation. Further experimental data confirmed that the ROS-p38-p53 pathway could be involved in the stimulation of autophagy, suggesting that autophagy may play a death-promoting role via the above-mentioned apoptotic pathway. In conclusion, these findings indicate that PCL induces both apoptosis and autophagy in cancer cells through a mitochondria-mediated ROS-p38-p53 pathway.

Polygonatum cyrtonema lectin induces apoptosis and autophagy in human melanoma A375 cells through a mitochondria-mediated ROS-p38-p53 pathway.

Polygonatum cyrtonema lectin (PCL), a mannose-binding lectin, has been reported to induce cytotoxicity and apoptosis. Herein, we demonstrated that PCL-induced apoptosis and autophagy in A375 cells. The apoptotic mechanism was that PCL treatment regulated Bax, Bcl-xL and Bcl-2 proteins, leading to mitochondrial depolarization, cytochrome c release and caspase activation. Subsequently, we found that PCL treatment abrogated glutathione antioxidant system and induced mitochondria to generate ROS accumulation, resulting in p38-p53 activation. Moreover, we confirmed that the ROS-p38-p53 pathway was involved in PCL-induced autophagy. In conclusion, these results indicate that PCL induces apoptosis and autophagy via a mitochondrial-mediated ROS-p38-p53 pathway.

Antiproliferative activity and apoptosis-inducing mechanism of Concanavalin A on human melanoma A375 cells.

The objective of this study was to investigate the antiproliferative activity and apoptosis-inducing mechanism of Concanavalin A (ConA) on human melanoma A375 cells. We firstly simulated the three-dimensional structure of ConA. Subsequently, we found that ConA possessed remarkable antiproliferative effect on A375 cells. Further experimental data indicated that there was a link between its hemagglutinating activity, mannose-binding activity and antiproliferative activity. In addition, we showed that ConA induced A375 cell apoptosis in a caspase-dependent manner. Then, we demonstrated that the treatment of ConA caused mitochondrial transmembrane potential (MMP) collapse, cytochrome c release and caspase activation. In conclusion, we report for the first time that there may be a close correlation between carbohydrate-binding activity of ConA and its antiproliferative activity. Also, we demonstrate firstly that ConA induces A375 cell death in a caspase-dependent manner as well as through a mitochondrial apoptotic pathway.

A novel sialic acid-specific lectin from Phaseolus coccineus seeds with potent antineoplastic and antifungal activities.

A novel lectin (PCL) with specificity towards sialic acid was purified from Phaseolus coccineus L. (P. multiflorus willd) seeds using ion exchange chromatography on CM and DEAE-Sepharose, and gel filtration on Sephacryl S-200 column. PCL was a homodimer consisting of 29,831.265 Da subunits as determined by gel filtration and MS. Also, PCL was a non-metalloprotein and its N-terminal 23-amino acid sequence, ATETSFSFQRLNLANLVLNKESS, was determined. Subsequently, MTT method, cell morphological analysis and LDH activity-based cytotoxicity assays demonstrated that PCL was highly cytotoxic to L929 cells and induced apoptosis in a dose-dependent manner. Using caspase inhibitors, a typical caspase-dependent pathway was confirmed. PCL also showed remarkable antifungal activity towards some plant pathogenic fungi. Furthermore, when sialic acid-specific activity was fully inhibited, cytotoxicity and antifungal activity were abruptly decreased, respectively, suggesting a significant correlation between sialic acid-specific site and its bi-functional bioactivities.

Nebrodeolysin, a novel hemolytic protein from mushroom Pleurotus nebrodensis with apoptosis-inducing and anti-HIV-1 effects.

A novel hemolysin was isolated from the edible mushroom Pleurotus nebrodensis by ion exchange and gel filtration chromatography on DEAE-Sepharose and Sephacryl S-100. The hemolysin from Pleurotus nebrodensis hemolysin (nebrodeolysin) is a monomeric protein with a molecular weight of approximately 27 kDa as determined by gel filtration and SDS-PAGE. Nebrodeolysin exhibited remarkable hemolytic activity towards rabbit erythrocytes and caused efflux of potassium ions from erythrocytes. Subsequently, this hemolysin showed strong cytotoxicity against Lu-04, Bre-04, HepG2, L929, and HeLa cells. It was also found that this hemolysin induced apoptosis in L929 and HeLa cells as evidenced by microscopic observations and DNA ladder, respectively. Moreover, this hemolysin was shown to possess anti-HIV-1 activity in CEM cell culture.

Apoptosis-inducing effect and structural basis of Polygonatum cyrtonema lectin and chemical modification properties on its mannose-binding sites.

Polygonatum cyrtonema Lectin (PCL), which is classified as a monocot mannose-binding lectin, has received great regards for its uniquely biological activities and potentially medical applications in cancer cells. This paper was initially aimed to study apoptosis of PCL on Hela cells. Thus, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) method was carried out. Through observation of cell morphologic changes and Lactate dehydrogenase (LDH) activity-based cytotoxicity assays, PCL induced HeLa cell apoptosis in a dose-dependent manner. To further gain structural basis, multiple alignments, homology modeling and docking experiments were performed to analyze the correlation between its biological activities and mannose-binding sites. Eventually, considering docking data, chemical modification properties on the three mannose-binding sites were analyzed by a series of biological experiments (e.g., hemagglutinating and mitogenic activity assays, fluorescence and Circular Dichrosim (CD) spectroscopy) to profoundly identify the role of some key amino acids in the structure-function relationship of PCL.

A mannose-binding lectin from Sophora flavescens induces apoptosis in HeLa cells.

The objective of this study was to investigate the anti-tumor activity of a lectin from Sophora flavescens and explore its potential apoptotic induction mechanism. Here, an elegant series of biochemical and cell biology methods were carried out in a sequential procedure (e.g., MTT, cell morphologic changes and LDH assays, DNA ladder as well as flow cytometric assay). As a result, we found that this lectin shows a strong cytotoxicity against HeLa cells and induces apoptosis in a time- and dose-dependent manner. Subsequently, according to caspase inhibition and Western blot analysis, we further demonstrated that it is a typical caspase-dependent apoptotic mechanism. Furthermore, we also exerted some bioinformatics methods to identify the mannose-binding specificity of this lectin. In conclusion, all experimental results demonstrated that this lectin seems to be a potent anti-tumor agent for its cytotoxicity and apoptosis effects on HeLa cells. Also, bioinformatics analyses showed that this lectin is speculated to bind a certain mannose-containing receptor on cancer cell surface thereby initiating downstream caspase cascade.