Figure 2.

Overexpression of cyclin D genes influence cell cycle progression at the G ₁ /S transition point in myeloma. Increased cyclin D gene expression through hyperdiploid or nonhyperdiploid events in myeloma facilitates activation of a cyclin-dependent kinase (CDK 4 or 6). The respective CDK then phosphorylates Rb (retinoblastoma protein), which subsequently resides from its role inhibiting E2F transcription factors allowing these to facilitate cell cycle progression at the G₁/S transition. G₁: Gap-1 phase; S: synthesis phase; G2: Gap-2 phase; M: mitosis; P: phosphate group.