RB1 and neoplasm: Cyclin D1 could promote cell transition through G1 phase via activating CDK4, which leads to increased phosphorylation of Rb (p-Rb).23, 24 Thus, a decreased level of CDK4-cyclin D complex can inhibit the phosphorylation of Rb and ultimately induce cell cycle arrest at the G1 phase.25 The cell cycle arrest was attributed, at least in part, to the anticancer effect of linc-UFC1 knockdown on tumor growth.