We, therefore, sought to investigate whether LEE011 (ribociclib), a CDK4/6 inhibitor approved by FDA for breast cancer treatment and under clinical investigation in various type of tumors, including melanoma (www.clinicaltrial.gov), was able to impair PTTG1 expression in A375R cells and whether this molecular event was associated with inhibition of proliferation and invasion and/or modulation of response to dabrafenib. This evidence concerns the gene CDK4 and breast cancer.