Overexpression of cyclin E in the HC11 mouse mammary epithelial cell line is associated with growth inhibition and increased expression of p27(Kip1).
To elucidate the role of cyclin E in cell growth and tumorigenesis in mammary epithelial cells, we have used retrovirus-mediated transduction to generate derivatives of the nontransformed HC11 mouse mammary epithelial cell line that stably express a human cyclin E cDNA (HU4). These derivatives expressed two distinct forms of the exogenous cyclin E protein, which were about M(r) 50,000 and M(r) 42,000, thus corresponding to endogenous cyclin E proteins found in human cells. In contrast to results obtained previously in fibroblasts, overexpression of the HU4 cyclin E cDNA in HC11 cells was associated with an increase in cell size, lengthening of G(1), and inhibition of both anchorage-dependent and independent growth. Furthermore, when quiescent serum-starved cells were restimulated with serum, entry into the S-phase was delayed in the overexpressor cells. Under these conditions, there was also delayed induction in the expression of the endogenous cyclin E protein and in other events involved in the G(1) transition. Despite the high level of expression of the exogenous cyclin E, the derivatives did not display increased cyclin E-associated in vitro kinase activity. The HC11 cells that overexpressed the exogenous cyclin E displayed an increase in the cyclin/cyclin-dependent kinase inhibitor p27(Kip1) in both asynchronous exponentially dividing and synchronous cell populations. These findings indicate that increased expression of this cyclin E cDNA in HC11 cells inhibits rather than stimulates growth and that this may be due to increased expression of the inhibitor p27(Kip1).
Sgambato
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Columbia-Presbyterian Cancer Center, Columbia University, New York 10032, USA.
Han
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EK
Zhou
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Schieren
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I
Weinstein
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IB
D000818:Animals; D001940:Breast / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018076:DNA, Complementary / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D016193:G1 Phase; D016195:G2 Phase; D015870:Gene Expression; D006801:Humans; D008321:Mammary Glands, Animal / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008970:Molecular Weight; D012333:RNA, Messenger / Q000378:metabolism*; D016192:Resting Phase, Cell Cycle; D016196:S Phase; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins
D002364:Caseins; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D016213:Cyclins; D018076:DNA, Complementary; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases