We investigated mRNA expression levels of Cyclin D1, RPTOR, Myc, SMAD3, MARCKS, RICTOR, p16, and FOXM1, which are related to CDK4/6 as, e.g., cellular inhibitor, binding partner, or central proteins of downstream pathways in our 10 cell lines including healthy fibroblasts, breast cancer, and skin cancer cells. Here, SMAD3 is linked to breast carcinoma.