Short and sweet: evolution of a small glycopeptide from a bladder disorder to an anticancer lead

Glycopeptides are a class of molecules that comprise two distinct families of biologically important scaffolds, peptides and oligosaccharides, each playing important roles in cellular communication and signaling. Rarely are small, endogenous secreted glycopeptides found that have significant impact on the progression of a specific disease state, but such is the case for the antiproliferative factor (APF) found in the urine and tissue of patients with the poorly understood bladder diseases collectively referred to as interstitial cystitis (IC). APF is a 9-mer peptide containing a sialylated O-linked trisaccharide glycan attached to the N-terminal threonine. APF dramatically inhibits normal bladder cell proliferation and is thought to cause some of the characteristic pathological changes in the bladder of IC patients. Importantly, APF also potently inhibits the growth of certain tumor cells. The details of the cellular receptors to which APF interacts, and the structural features that are critical for its potency are now beginning to unfold. This interesting molecule is a powerful model for the design of new treatments and diagnostic tests for IC, as well as an unprecedented lead agent for novel anticancer drug design.