We recently observed that sulfopolysaccharides isolated from sea algae can inhibit the ATP-hydrolyzing ectonucleotidases NPP1 (CD203a; CD, cluster of differentiation) and NTPDase1 (CD39) (11), enzymes whose important role in cancer proliferation, angiogenesis, metastasis, and immune escape is increasingly recognized (12, 13). The gene discussed is ENTPD1; the disease is cancer.