The specific targeting of differentially expressed glycans in malignant cells has emerged as an attractive anticancer strategy. One such target is the oncodevelopmental antigen polysialic acid (polySia), a polymer of alpha 2,8-linked sialic acid residues that is largely absent during postnatal development but is re-expressed during progression of several malignant human tumors, including small-cell and nonsmall cell lung carcinomas, glioma, neuroblastoma, and pancreatic carcinoma. In these cancers, expression of polySia correlates with tumor progression and poor prognosis and appears to modulate cancer cell adhesion, invasiveness, and metastasis.