Carbohydrate-binding proteins, called lectins, have shown promise as anti-cancer therapeutics. Concanavalin A (ConA), a lectin found in jack beans, is one such lectin. This lectin binds to several receptors on cancerous and normal cells and thereby triggers signaling cascades that can induce the controlled death of the tumor cells via autophagy or apoptosis or activate the immune system. ConA has also been shown to modulate the formation of the new blood vessels that would feed tumors. MT1-MMP is the host cell receptor responsible for most of this lectin’s impact, particularly autophagy and immune cell activation, and the proteins P73 and JAK/STAT3 are key to ConA’s autophagic and apoptotic effects. However, ConA is toxic to living cells and as such has serious side effects that include liver damage, and repeated administration of ConA can cause the body to generate antibodies against it, limiting its effectiveness. Modifying ConA or generating artificial peptides could lead to safer, more effective ConA-based treatments, but more basic research and clinical trials are needed before ConA can be used as a cancer therapy.