Another example is the use of PDE5 inhibitors (sildenafil, tadalafil, and vardenafil) in mouse models of colon carcinoma, mammary adenocarcinoma, and fibrosarcoma, where the accumulation of cGMP inhibited myeloid-derived suppressor cells (MDSCs)-elicited immunosuppression, enhanced intratumoral T cell infiltration, and favored tumor regression but not eradication [84]. Here, PDE5A is linked to breast adenocarcinoma.