CCND1 and cancer: The results of preclinical studies in other cancer types, such as hepatocellular carcinoma [22], ovarian cancer [23], rhabdoid tumor [24], and glioblastoma [25], also indicated that palbociclib effectively targets cancer cells with the following characteristics: (a) cyclin D1 overexpression, (b) functional RB, and (c) p16 inactivation.