Aralin, a new cytotoxic protein from Aralia elata, inducing apoptosis in human cancer cells

In this study, we purified a novel cytotoxic protein, aralin, from the shoots of Aralia elata. Aralin is composed of two subunits, A and B chains whose molecular weights are 29,100 and 32,200, respectively. In the assay using a normal human lung fibroblast cells (WI-38) and its SV40-transformed cells (VA-13), aralin demonstrated selective cytotoxicity against the virus-transformed cell line; the IC50 values of WI-38 and VA-13 were 10 and 0.8 ng/ml, respectively. Aralin showed positive response to DNA fragmentation in human lymphocyte HL-60 cells, and caspase specific inhibitors suppressed aralin-induced DNA fragmentation. These results indicate that the cytotoxicity of aralin is brought about primarily through the induction of apoptosis. Aralin also exhibited potent cytotoxic activity against various types of human cancer cell lines; cervical carcinoma cells (HeLa) proved the most sensitive, with an IC50 value of 0.08 ng/ml.