Recent studies have provided compelling evidence that tumor cells either build a microenvironment locally or reach other organs systemically by changing their immunogenic phenotypes [3], [4], particularly the expression levels of the major histocompatibility complex I (MHC-I), B7-1, indoleamine 2, 3-dioxygenase (IDO) and B7-H1. The gene discussed is IDO1; the disease is neoplasm.