FOXP3 and neoplasm: It is, therefore, tempting to speculate that the reduced number of OT-II CD4+FoxP3.gfp+ T cells observed in the EG.7 tumor in the present study may be due to the ability of SA-4-1BBL to stimulate conventional CD4+ and CD8+ T cells for the production of IFN-γ, which in turn blocks the conversion of CD4+ T cells into iTreg cells.