CDK4 and lung cancer: More than that, we suspected that CDK4, a component necessitated for cell-cycle progression by activating E2F and CyclinE [64–66], was of significance to elaborate lncRNA AFAP1-AS1/miR-545-3p-involved TNBC development and chemo-resistance (Figures 4, 5), and the miR-545/CDK4 axis has been underlined in explaining etiologies of colorectal cancer [67] and lung cancer [59].