The authors found that the cell cycle kinase CDK6 forms an active complex with the atypical cyclin I (CCNI) and that this complex promotes retinoblastoma phosphorylation, E2F‐mediated gene expression, and tumor proliferation in vitro and in vivo, similarly to the cyclin D1 (CCND1)/CDK6 complex. This evidence concerns the gene CCND1 and neoplasm.