Elsevier

Journal of Dairy Science

Volume 74, Issue 8, August 1991, Pages 2778-2787
Journal of Dairy Science

Article
Fundamentals of Cell Proliferation: Control of the Cell Cycle

https://doi.org/10.3168/jds.S0022-0302(91)78458-0Get rights and content
Under a Creative Commons license
open archive

Abstract

Cell proliferation in higher eukaryotes is controlled by the extracellular environment and the state of differentiation. Many cells exist in a nondividing growth state termed quiescence. Some quiescent cells cannot proliferate and are said to be terminally differentiated. Others can be stimulated to divide in response to environmental signals or when cell replacement is needed. Finally, some cells undergo continual proliferation and differentiation.

Growth regulatory factors generally act at specific stages of the cell cycle, most commonly during the first gap phase of the cell cycle. Once cells initiate DNA synthesis, they are generally committed to complete DNA replication. After DNA synthesis, additional signals determine whether cells in the last gap phase proceed through mitosis.

In recent years, genes that appear to be critical for progression through the first two gap phases have been identified. Many are proto-oncogenes and therefore can neoplastically transform certain cells when mutated or inappropriately expressed. Growth factors that stimulate proliferation induce the expression of several proto-oncogenes; growth inhibitory factors often suppress proto-oncogene expression.

As cells differentiate, the response to extracellular factors changes. In many cases, this may be due to intracellular controls that alter the response of certain proto-oncogenes to external signals.

Key words

cell proliferation
cell cycle proto-oncogenes

Abbreviation key

EGF
epidermal growth factor
G
gap phase of the cell cycle
IGF-I
insulin-like growth factor-I
M
mitosis
ODC
ornithine decarboxylase
PDGF
platelet-derived growth factor
S
DNA synthetic phase of the cell cycle

Cited by (0)

1

Present address: Division of Cell and Molecular Biology, Lawrence Berkeley Laboratory, University of California, Berkeley, CA 94720.