CTLA4 and carcinoma of esophagus: In the TISIDB database, ENTPD1 expression in esophageal carcinoma was shown to be statistically positively correlated with the expression of currently recognized inhibitory immune checkpoint molecules PDCD1 (p < 0.001), CTLA4 (p < 0.001), and HAVCR2 (p < 0.001) (Figure S2a–c).