ENTPD1 and colonic neoplasm: Previous studies have shown that CD39 and CD73 are ectonucleotidases that hydrolyse extracellular ATP to adenosine, a classic and very strong immunosuppressive agent.14 Similar to our previous results in colon cancer,12 the level of adenosine in breast tumour tissues was much higher than that in normal tissues (p < 0.01, Fig. 3e).