GZMB and neoplasm: Recent studies have shown that polyamine blocking therapy (PBT) reduced not only CD206+F4/80+ M2 macrophages but also tumor infiltrating cells including Gr-1+CD11b+ myeloid-derived suppressor cells (MDSCs) and CD4+CD25+ Tregs and concomitantly increased granzyme B+ and IFN-γ+ CD8+ T cells in TME [31, 34].