Lectins: from basic science to clinical application in cancer prevention

Sequence-based predictive modeling to identify cancerlectins

Lectins are a diverse type of glycoproteins or carbohydrate-binding proteins that have a wide distribution to various species. They can specially identify and exclusively bind to a certain kind of saccharide groups. Cancerlectins are a group of lectins that are closely related to cancer and play a major role in the initiation, survival, growth, metastasis and spread of tumor. Several computational methods have emerged to discriminate cancerlectins from non-cancerlectins, which promote the study on pathogenic mechanisms and clinical treatment of cancer. However, the predictive accuracies of most of these techniques are very limited. In this work, by constructing a benchmark dataset based on the CancerLectinDB database, a new amino acid sequence-based strategy for feature description was developed, and then the binomial distribution was applied to screen the optimal feature set. Ultimately, an SVM-based predictor was performed to distinguish cancerlectins from non-cancerlectins, and achieved an accuracy of 77.48% with AUC of 85.52% in jackknife cross-validation. The results revealed that our prediction model could perform better comparing with published predictive tools.

Synthesis and cytotoxicity of bidesmosidic betulin and betulinic acid saponins

The naturally occurring cytotoxic saponin 28-O-beta-d-glucopyranosylbetulinic acid 3beta-O-alpha-l-arabinopyranoside (3) was easily synthesized along with seven bidesmosidic saponins starting from the lupane-type triterpenoids betulin (1) and betulinic acid (2). As highlighted by the preliminary cytotoxicity evaluation against A549, DLD-1, MCF7, and PC-3 human cancer cell lines, the bidesmosidic betulin saponin 22a, bearing alpha-l-rhamnopyranoside moieties at both C-3 and C-28 positions, was determined to be a potent cytotoxic agent (IC(50) 1.8-1.9 microM).

Probiotic Lactobacillus plantarum 299v does not counteract unfavorable phytohemagglutinin-induced changes in the rat intestinal microbiota

Application of phytohemagglutinin (PHA) in weaning feed has been suggested to stimulate intestinal epithelium maturation. In this study, PHA strongly affected the fecal bacterial population structure of rats. Escherichia coli overgrowth was not prevented by probiotic mannose-adhering Lactobacillus plantarum 299v. Therefore, use of PHA in weaning feed deserves careful evaluation.

Beyond carbohydrate binding: new directions in plant lectin research

Although for a long time carbohydrate binding property has been used as the defining feature of lectins, studies carried out mostly during the last two decades or so demonstrate that many plant lectins exhibit specific interactions with small molecules that are predominantly hydrophobic in nature. Such interactions, in most cases, appear to be at specific sites that do not interfere with the ability of the lectins to recognise and bind carbohydrates. Further, several of these ligands have binding affinities comparable to those for the binding of specific carbohydrates to the lectins. Given the ability of lectins to specifically recognise the glycocode (carbohydrate code) on different cell surfaces and distinguish between diseased and normal tissues, these additional sites may be viewed as potential drug carrying sites that could be exploited for targeted delivery to sites of choice. Porphyrin-lectin complexes are especially suited for such targeting since porphyrins are already under investigation in photodynamic therapy for cancer. This review will provide an update on the interactions of plant lectins with non-carbohydrate ligands, with particular emphasis on porphyrin ligands. The implications and potential applications of such studies will also be discussed.