Curcin is a ribosome-inactivating protein expressed in the endosperm of Jatropha curcas. Curcin can inhibit growth of mouse sarcoma-180 cells. At a curcin concentration of 100 μg/ml, mouse sarcoma-180 cell growth was inhibited by over 40% after seven days of incubation. Acridine orange staining and flow cytometry analysis also showed that the curcin could induce apoptosis of mouse sarcoma-180 cells. These observations provide a possible explanation for the anti-tumor properties of curcin.