New directions in cancer therapy based on aberrant expression of glycosphingolipids: anti-adhesion and ortho-signaling therapy.

Essentially all tumors express aberrantly glycosylated glycosphingolipids and glycoproteins, more commonly known as "tumor-associated carbohydrate antigens." In this article I propose two new forms of cancer therapy, anti-adhesion therapy and ortho-signaling therapy, which exploit these tumor-associated carbohydrates in distinct ways. The aim of anti-adhesion therapy is to disrupt the requisite carbohydrate-initiated interactions that occur between tumor cells and other cell types (e.g., endothelial cells, platelets) as tumors progress and metastasize. Candidate anti-adhesion agents include purified carbohydrates or glycosphingolipids representing H, Ley, sialosyl-Lex (or -Lea) GM3, or LacCer antigens, and monoclonal antibodies directed to these structures. The aim of ortho-signaling therapy is to disrupt mitogenic signaling pathways in tumor cells that are regulated by glycosphingolipids and/or their derivatives, including pathways involving receptor protein-kinases and protein kinase C. Candidate ortho-signaling agents are the glycosphingolipid regulator PDMP (1-phenyl-2-[decanoylamino]-3-morpholino-1-propanol) and the protein kinase C inhibitor DMS (N,N-dimethylsphingosine), both of which show antitumor activity in vitro and in animal studies.