Ribosome-inactivating proteins(RIPs) belong to a family of enzymes that attack eukaryotic ribosomes and potently inhibit cellular protein synthesis.RIPs possess several biomedical properties,including anti-viral and anti-tumor activities.Multiple RIPs are known to inhibit tumor cell proliferation through inducing apoptosis in a variety of cancers,such as breast cancer,leukemia/lymphoma,and hepatoma.This review focuses on the anti-tumor activities of RIPs and their apoptotic effects through three closely related pathways:mitochondrial,death receptor,and endoplasmic reticulum pathways. Ribosome-inactivating proteins (RIPs) belong to a family of enzymes that attack eukaryotic ribosomes and potently inhibit cellular protein synthesis. RIPs have several biomedical properties, including anti-viral and anti-tumor activities. Multiple RIPs are known to inhibit tumor cell proliferation through inducing apoptosis in a variety of cancers, such as breast cancer, leukemia / lymphoma, and hepatoma. this review focuses on the anti-tumor activities of RIPs and their apoptotic effects through three closely related pathways: mitochondrial, death receptor, and endoplasmic reticulum pathways .