CDK4 and neuroblastoma: These observations are noteworthy considering that CCND1, CDK4 and CDK6 are G1 phase-regulating genes, part of the Cyclin D/CDK4/CDK6/RB pathway found hyperactive in NB, and considering the efficacy of new small molecule inhibitor targeting CDK4/CDK6 leading to G1 arrest and cellular senescence [42].