Another combination immunotherapy method is the use of immune checkpoint inhibitors in combination with agents that modify the tumour microenvironment in a non-specific manner (e.g., pro-inflammatory cytokines, immunosuppressive cytokine inhibitors, and indoleamine 2,3-dioxygenase and adenosine inhibitors) [11,12,13,14,15]. The gene discussed is IDO2; the disease is neoplasm.