Because polyamine blocking therapy (PBT) was shown to significantly inhibit tumor growth and reduce the immunosuppressive tumor microenvironment [16,29], we used GCN2−/− mice to investigate if polyamine-dependent signaling through the GCN2 receptor via arginine depletion plays a role in the development of the immunosuppressive tumor microenvironment. This evidence concerns the gene EIF2AK4 and neoplasm.