ENTPD1 and neoplasm: In line with this hypothesis, in different studies, CD137 expression on EOC TILs identified functional and tumor-specific lymphocytes among either CD39+, CD103+ or PD-1+ TILs (19, 26), and agonistic CD137-specific antibodies enhanced the effect of anti-PD-1 inhibition on cytokines production by CD39+ EOC TILs (79).