[Macrophage cell cycle control by M-CSF/CSF-1]

Temporally orderly activation of the cyclin-dependent kinases (cdks) governs the progression and the transitions of the cell cycle in mammalian cells. Macrophages require a specific growth factor, M-CSF/CSF-1, for their proliferation throughout the G1 phase of the cell cycle. Once cells enter S phase, macrophages complete mitosis in the absence of M-CSF/CSF-1. During the G1 phase, cyclin D1 is induced by M-CSF/CSF-1 stimulation and forms enzymatically active complex with cdk 4. The enzymatic activity of the cyclin D1 and cdk 4 complex could be negatively regulated by recently reported inhibitory proteins to determine the timing for entry into S phase in macrophages.