CDK4 and breast carcinoma: To date, in clinical or preclinical studies of melanoma [32], ovarian cancer [33], pancreatic cancer [34] and glioblastoma [35], low p16 expression has been associated with CDK4/6 inhibitor sensitivity, whereas in breast cancer, p16 levels were not predictive, leaving its overall value as a response biomarker unclear at present [24, 36].