Although CDK4 and CDK6 can potentially bind the same D type cyclins to regulate G1‐S phase progression (Choi & Anders, 2014), it is well established that each CDK and each D cyclin plays unique roles, both in normal development and during cancer progression (Malumbres et al, 2004; Malumbres, 2011; Choi et al, 2012; Kollmann et al, 2013). Here, CDK4 is linked to cancer.