A role in favoring cancer growth and dissemination has been described for each of the extracellular enzymes involved in nucleotide/nucleoside and NAD+ metabolism (i.e., CD39, CD38, CD203a and CD73) and for the complexing ADO deaminase (ADA)/CD26 molecules, a controller of ADO in the extracellular space. This evidence concerns the gene DPP4 and cancer.