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Mol Cell Biol. 2011 Sep;31(18):3885-95. doi: 10.1128/MCB.05089-11. Epub 2011 Jul 11.

Hypoxia-inducible factor 1 is activated by dysregulated cyclin E during mammary epithelial morphogenesis.

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  • 1Department of Medicine, Division of Hematology/Oncology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.


Increased cyclin E expression has been identified in human tumors of diverse histologies, and in studies of primary breast cancers, high cyclin E is associated with poor prognosis. We have studied dysregulated cyclin E in epithelial tissues using organotypic cultures of human mammary epithelial cells and a murine model. We unexpectedly discovered that dysregulated cyclin E impairs normal acinar morphogenesis in vitro, and this is associated with the induction of p21(Cip1), p27(Kip1), and cellular senescence. Cyclin E-induced morphogenesis arrest is dependent upon hypoxia-inducible factor 1α (HIF-1α), which itself is induced by high cyclin E both in cultured mammary acini and in mammary epithelial tissues in a mouse model of deregulated cyclin E expression. We next determined that E2F activity directly regulates and is required for induction of HIF1A by cyclin E. Additionally, we found that cyclin E deregulation in mammary acini decreases, in an E2F-independent manner, expression of the EGLN1 prolyl hydroxylase that regulates HIF-1α degradation within the VHL ubiquitin ligase pathway. Together, our findings reveal a direct link between cyclin E and HIF-1 activities in mammary epithelial cells and implicate HIF-1 as a mediator of proliferation-independent phenotypes associated with high cyclin E expression in some human breast cancers.

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