Alterations to the local nutritional status [47] by indoleamine 2,3 dioxygenase 1 (IDO) expression [48] or Tregs [49], CD39/CD73/A2AR [50], protein arginine methyltransferase 5 (PRMT5) [51], and HIF1α expression associated with hypoxia during tumor progression [52] also contribute to an immunosuppressive microenvironment surrounding tumor cells. This evidence concerns the gene IDO1 and neoplasm.