Many RB1‐deficient breast cancer cells display reduced DNA replication in response to palbociclib (Dean et al, 2010), and reduced levels of phosphorylated RB1 alone do not explain the oncosuppressive effects of palbociclib, at least in liposarcoma patients where such data are available (Kovatcheva et al, 2015). The gene discussed is RB1; the disease is breast carcinoma.