Due to the fact that APN/CD13 can be found on several tumors and immune cells (e.g., T and B cell precursors, monocytes, and dendritic cells) [16, 48], bestatin can directly inhibit tumor growth and angiogenesis by blocking APN/CD13 on the tumorous cell surface; furthermore, bestatin can modulate the antitumoral immune response. This evidence concerns the gene ANPEP and neoplasm.