A Polylactosamine Specific Lectin from Adenia hondala Induces Apoptosis and Necrosis in Human Epithelial Colon Cancer HT-29 Cells.

Abstract

Altered expression of N-glycans such as polylactosamine is observed in colon cancer. AHL, a polylactosamine specific lectin from Adenia hondala from a medicinal plant from the Passifloraceae family has been reported earlier. The aim of the present study is to study the interaction of AHL with human colon cancer epithelial HT-29 cells and colon cancer tissues. Cell viability was determined by MTT [3-[4, 5- dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide] assay, while cell surface binding, apoptosis by Annexin-V-PI assay and ROS production using DCFDA [2',7' - dichlorofluorescindiacetate] kit method were analysed by flowcytometry, immunohistochemistry was performed using biotinylated AHL, protein purification by affinity chromatography using asialofetuin-coupled Sepharose -4B column. AHL strongly binds to HT-29 cells with a Mean Fluorescence Intensity of 12.4, which could be blocked by competing glycoprotein asialofetuin. AHL inhibits HT-29 cell growth in a dose and time-dependent manner with IC50 of 2.5 μg/mL and differentially binds to human normal and cancerous tissues. AHL induces apoptosis and slight necrosis in HT-29 cells with an increase in the early apoptotic population of 25.1 and 36% for 24 h and 48 h respectively and necrotic population of 1.5 and 4.6% at 24 h and 48 h respectively as revealed by Annexin-V-PI assay. AHL induces the release of Reactive Oxygen Species in HT-29 cells in a dose-dependent manner. To the best of knowledge, this is the first report on lectin from Adenia hondala which is not a RIP with apoptotic and necrotic effects. These findings support the promising potential of AHL in cancer research.