ENTPD2 and carcinoma of esophagus: Since ATP is hydrolyzed by ubiquitously expressed ecto-ATPases and ectonucleotidases, this could explain, why the hydrolysis resistant ATP derivative ATPγS, which is additionally known to be an effective ecto-ATPase-inhibitor (Chen and Lin, 1997), failed to induce apoptosis specific caspase-3 activation in oesophageal cancer cells.