Rhizoctonia bataticola lectin induces apoptosis and inhibits metastasis in ovarian cancer cells by interacting with CA 125 antigen differentially expressed on ovarian cells.

A N-glycan specific lectin from Rhizoctonia bataticola [RBL] was shown to induce growth inhibitory and apoptotic effect in human ovarian, colon and leukemic cells but mitogenic effect on normal PBMCs as reported earlier, revealing its clinical potential. RBL has unique specificity for high mannose tri and tetra antennary N-glycans, expressed in ovarian cancer and also recognizes glycans which are part of CA 125 antigen, a well known ovarian cancer marker. Hence, in the present study diagnostic and therapeutic potential of RBL was investigated using human ovarian epithelial cancer SKOV3 and OVCAR3 cells known for differentially expressing CA 125. RBL binds differentially to human ovarian normal, cyst and cancer tissues. Flow cytometry, western blot analysis of membrane proteins showed the competitive binding of RBL and CA 125 antibody for the same binding sites on SKOV3 and OVCAR3 cells. RBL has strong binding to both SKOV3 and OVCAR3 cells with MFI of 173 and 155 respectively. RBL shows dose and time dependent growth inhibitory effect with IC50 of 2.5 and 8 µg/mL respectively for SKOV3 and OVCAR3 cells. RBL induces reproductive cell death, morphological changes, nuclear degradation and increased release of ROS in SKOV3 and OVCAR3 cells leading to cell death. This is also supported by increase in hypodiploid population, altered MMP leading to apoptosis possibly involving intrinsic pathway. Adhesion, wound healing, invasion and migration assays demonstrated anti-metastasis effect of RBL apart from its growth inhibitory effect. These results show the promising potential of RBL both as a diagnostic and therapeutic agent.

Purification, characterization and biological significance of mannose binding lectin from Dioscorea bulbifera bulbils.

Dioscorea bulbifera or air potato has been used as a folk remedy to treat cancer. A mannose binding lectin from bulbils of D. bulbifera was purified in a single step by affinity chromatography on mucin coupled Sepharose 4B column, determined by its fine sugar specificity by glycan array analysis and studied for its clinical potential in cancer and HIV research. SDS-PAGE showed that lectin is a monomer of Mr 24kDa. DBL agglutinated only rabbit erythrocytes and was inhibited by mucin, asialomucin, fetuin, asialofetuin and transferrin but not by any monosaccharides. Glycan array analysis of DBL revealed its affinity toward high mannose N-linked glycans with enhanced affinity for terminal mannose including N-linked glycans of HIV envelope glycoprotein gp120 and has strong anti-reverse transcriptase activity. DBL showed strong binding to non-metastatic human colon epithelial cancer HT 29, metastatic SW 620 and hepatocellular HepG2 cell lines. DBL showed dose and time dependent growth inhibitory effects on all the three cell lines HT 29, SW 620 and HepG2 with IC50 of 110µg, 9.8µg, 40µg respectively at 72h. Inhibitory effect of DBL was effectively blocked in presence of competing glycans like mucin. DBL has promising clinical potential both in cancer and HIV research.