CDK6 and osteosarcoma: However, a recent clinical trial on chemotherapy-refractory pediatric solid tumors, including osteosarcomas and rhabdomyosarcomas selected for harboring genomic alterations in the cyclinD-CDK4/6 and CCND3 pathway, concluded that pathway alteration alone was insufficient to generate a response to palbociclib (selective inhibitor of CDK4 and CDK6) monotherapy; therefore, underlining the need to further evaluate combined therapies [49].