A Calcium Ion-Dependent Dimeric Bean Lectin with Antiproliferative Activity Toward Human Breast Cancer MCF-7 Cells

In this study, a 60.8-kDa dimeric lectin was isolated from the Phaseolus vulgaris cv. jade bean and characterized. The lectin was bound on Blue Sepharose 6 and Q Sepharose and was finally purified by size exclusion chromatography on Superdex 200. Its hemagglutinating activity toward rabbit erythrocytes was dependent on divalent cations, especially calcium ions. Various carbohydrates tested were devoid of any effect on the hemagglutinating activity. The lectin was stable at pH between 4.5 and 9.4 and temperatures between 30 and 70 degrees C. It did not exert antifungal activity toward Valsa mali, Setosphaeria turcica, Mycosphaerella arachidicola, Fusarium oxysporum and Bipolaris maydis. The IC50 of the antiproliferative activity of the lectin toward MCF-7 human breast cancer cells was 174 mu M. It did not inhibit proliferation of WRL-68 human normal embryonic hepatocytes. The lectin was dependent on calcium ions for hemagglutinating activity and possessed a blocked N-terminus. These two characteristics make the lectin unique among Phaseolus lectins.