A well-accepted notion is that ADK-S (generally named as ADK in previous publications) regulates intracellular adenosine processing and extracellular availability of adenosine for its activation of adenosine receptors (e.g., adenosine A1, A2A, A2B, and A3 subtype receptors); as related to cancer, these actions affect the angiogenesis, cell proliferation, apoptosis, and tumor immune response. This evidence concerns the gene ADK and cancer.