This process involves breaking immune tolerance by impairing the levels of T-regulatory lymphocytes (Treg) in the tumor microenvironment via LPS and the Braun lipoprotein (Lpp) of Salmonella enterica [115]; and by decreasing the levels of the enzyme indoleamine 2,3-dioxygenase-1 (IDO1) [90], an enzyme that acts on tryptophan metabolism and is associated with the development of immune tolerance in T lymphocytes [116,117], thus preventing the formation of kynurenine and promoting the proliferation of T lymphocytes capable of recognizing and eliminating the tumor. This evidence concerns the gene IDO1 and neoplasm.