In ovarian cancer, high levels of adenosine are due to tumor-specific expression of the ectonucleotidases CD39/ENTPD1 and CD73/ecto-5′-nucleotidase [7] which synergistically catalyze the degradation of extracellular immune-stimulatory ATP to immune-inhibitory adenosine. Here, ENTPD1 is linked to ovarian carcinoma.