Purified mulberry leaf lectin (MLL) induces apoptosis and cell cycle arrest in human breast cancer and colon cancer cells.

Medicinal values of mulberry are known to humans from ancient ages. The white mulberry, Morus alba L. is a rich source of many bioactive phytochemicals. Earlier investigations in our laboratory lead to the purification and characterization of an anti-proliferative lectin (MLL) from the leaves of this plant. Further to that, here we have investigated the mechanism of cell death induction by MLL on human breast cancer (MCF-7) and colon cancer (HCT-15) cells. Cells were treated with GI(50) concentration (concentration of lectin required for 50% inhibition of cell growth) of MLL (8.5 μg/ml for MCF-7 and 16 μg/ml for HCT-15) for 24 h to induce cell death. The induction of apoptosis was studied by morphological analysis, DNA fragmentation, apoptotic cell staining and caspase 3 activity assay. Apoptotic cells in sub G0-G1 phase were monitored using flow cytometry. MLL induced significant morphological changes and DNA fragmentation associated with apoptosis in MCF-7 and HCT-15 cells. Positive annexin V and acridine orange/ethidium bromide stained cells indicated apoptosis induction by MLL. Up-regulation of caspase 3 activity was also found in cells treated with MLL. Flow cytometry analysis showed an increase in the percentage of cells in sub G0-G1 phase confirming the MLL induced apoptosis. In conclusion, MLL induced apoptosis in MCF-7 and HCT-15 cells in a caspase dependent manner.