PDE5A and glioblastoma: The decreased invasiveness of PDE5-overexpressing GBM cells was associated with lower MMP-2 levels, while cGMP elevating agents such as GSNO, CNP or sildenafil up-regulated MMP-2 secretion in T98G cells, as previously shown in synovial cells, colon cancer cells and NO-stimulated murine mammary adenocarcinoma cells [49, 50].