Lectins as modulators of autophagy in cancer immunotherapy

Lectins are carbohydrate-binding proteins that are widely expressed in nature. As the majority of proteins and lipids in the human body are glycosylated, lectins are potent modulators of cell signaling. Since cancer cells often have deregulated glycosylation patterns, they can be identified and specifically targeted by lectins. Indeed, plant lectins have strong anticancer activity as have been shown for concanavalin A (ConA). More recently the tumoricidal effect of animal lectins, especially galectins, has also been recognized. Both ConA and galectins induce cancer cell death that depends on autophagy, an important pathway that regulates the controlled breakdown of damaged and superfluous substrates in the cell. In addition, ConA and galectins are well-known for their effects on immune cells. Therapeutic strategies that trigger anticancer immune responses have the potential to completely eradicate cancers. Therefore, lectins may be suitable for cancer immunotherapy as they induce both cancer cell death as well as they elicit anticancer immune responses. This chapter will discuss the potential of ConA and galectins for cancer immunotherapy, focusing on the induction of autophagy-dependent cancer cell death and triggering anticancer immune responses.