Common events in cancer include the overexpression of cyclin D types cyclins and the loss of CDK inhibitors (especially p16INK4a, p15INK4b, p21 and p27), leading to CDK4 and CDK6 hyperactivation.293,317 Being the use of CDK4/6 inhibitors now approved for clinical use in some type of cancer, an enormous amount of data, also already reported in excellent specific reviews, have been produced in the last years and we refer to them for more comprehensive and detailed information (see for example318–320). Here, PCNA is linked to cancer.