Disclosed herein are polypeptides and fusion polypeptides that have anti-angiogenic activity that can be used to inhibit tumor growth and tumor metastasis. The polypeptide consists of 9 or less consecutive amino acid residues (e.g., 8, 7, 6, 5, or 4) comprising the active core amino acid sequence DWLP, or an amino acid substitution variant thereof. Specific amino acid substitutions are disclosed herein. In some embodiments, the peptide consists essentially of 4-6 mers identified as exhibiting the activity of prosaposin A. Also disclosed herein are therapeutic compositions comprising the polypeptides and fusion polypeptides, and their use in the treatment, prevention, and inhibition of angiogenesis-related diseases and disorders such as cancer and cancer metastasis.
