YY1 and osteosarcoma: Filomena de Nigris a suggests that Cyclin-dependent kinase 2 and 5 (Cdk2, Cdk5) are important mediators of neoangiogenesis in osteosarcoma, and a specific Yin Yang 1 (YY1) protein-dependent signal from tumor cells determines proliferation of human ECs, with Roscovitine inhibiting Cdk2 and Cdk5 activity, decreasing ECs proliferation and angiogenesis, and potentially serving as a pharmacologically accessible target for both antiangiogenic and antitumor therapy (31).