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J Steroid Biochem Mol Biol. 1998 Apr;65(1-6):169-74.

Estrogen regulation of cell cycle progression in breast cancer cells.

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Cancer Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, NSW, Australia.


Estrogens are potent mitogens in a number of target tissues including the mammary gland where they play a pivotal role in the development and progression of mammary carcinoma. The demonstration that estrogen-induced mitogenesis is associated with the recruitment of non-cycling, G0, cells into the cell cycle and an increased rate of progression through G1 phase, has focused attention on the estrogenic regulation of molecules with a known role in the control of G1-S phase progression. These experiments provide compelling evidence that estrogens regulate the expression and function of c-Myc and cyclin D1 and activate cyclin E-Cdk2 complexes, all of which are rate limiting for progression from G1 to S phase. Furthermore, these studies reveal a novel mechanism of activation of cyclin E-Cdk2 complexes whereby estrogens promote the formation of high molecular weight complexes lacking the CDK inhibitor p21. Inducible expression of either c-Myc or cyclin D1 can mimic the effects of estrogen in activating the cyclin E-Cdk2 complexes and promoting S phase entry, providing evidence for distinct c-Myc and cyclin D1 pathways in estrogen-induced mitogenesis which converge on the activation of cyclin E-Cdk2. These data provide new mechanistic insights into the known mitogenic effects of estrogens and identify potential downstream targets that contribute to their role in oncogenesis.

[Indexed for MEDLINE]

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