CD4 and glioma: In glioma patients, HO-1 mRNA expression has been linked to Foxp3 induction in infiltrating CD4+CD25+ Treg cells and correlated with glioma progression and grading (48), while in the preclinical model of malignant glioma the expression of HO-1 improved the survival of Tregs in the hypoxic regions of the TME (75).