Figure 1.

The cyclin D–cyclin-dependent kinase 4/6–retinoblastoma protein–E2F transcription-factor axis.

AKT, protein kinase B (also known as PKB); Cdc25, cell-division cycle 25 phosphatase family; CDK, cyclin-dependent kinase; CIP/KIP, CDK-interacting protein/kinase inhibitory protein family (including p21^Cip1, p27^Kip1, and p57^Kip2); E2F, E2F transcription factor; ERK, extracellular-signal-regulated kinases; E, estrogen; ER, estrogen receptor; INK4, inhibitor of CDK4 family (including p16^INK4A, p15^INK4B, p18^INK4C, and p19^INK4D); MEK, mitogen-activated protein kinase kinase; mTORC1, mammalian target of rapamycin complex 1; P, phosphate; p70S6K, ribosomal protein S6 kinases; PDK1, 3-phosphoinositide-dependent protein kinase 1; PI3K, phosphoinositide 3-kinase (p85 regulatory subunit and p110 catalytic subunit); PIP2, phosphatidylinositol 4,5-bisphosphate; PIP3, phosphatidylinositol 3,4,5 trisphosphate; PTEN, phosphatase and tensin homolog; Raf, family of serine-threonine kinases; Ras, GTP-binding proteins encoded by ras genes; Rb, retinoblastoma protein; TSC, tuberous sclerosis complex protein.