Interestingly, CD39 expression is genetically controlled by the SNP rs10748643 A/G within the promoter region of the CD39 gene [93], as demonstrated in Treg cells [94], peripheral activated CD4+ T cells [95], tumor-infiltrating CD8+ T cells [96], and SS cells, as we recently established. The gene discussed is ENTPD1; the disease is synovial sarcoma.