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Published online 20 October 2003. doi:10.1083/jcb.200304159
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© The Rockefeller University Press, 0021-9525/2003/10/315 $8.00
The Journal of Cell Biology, Volume 163, Number 2, 315-326

Article

 Akt activation disrupts mammary acinar architecture and enhances proliferation in an mTOR-dependent manner

Jayanta Debnath1,2, Stephanie J. Walker1 and Joan S. Brugge1

1 Department of Cell Biology, Harvard Medical School, Boston, MA 02115
2 Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115

Address correspondence to Joan S. Brugge, Dept. of Cell Biology, Harvard Medical School, 240 Longwood Ave., Boston, MA 02115. Tel.: (617) 432-3974. Fax: (617) 432-3969. email: joan_brugge{at}hms.harvard.edu

Activation of the serine/threonine kinase Akt/PKB positively impacts on three cellular processes relevant to tumor progression: proliferation, survival, and cell size/growth. Using a three-dimensional culture model of MCF-10A mammary cells, we have examined how Akt influences the morphogenesis of polarized epithelial structures. Activation of a conditionally active variant of Akt elicits large, misshapen structures, which primarily arise from the combined effects of Akt on proliferation and cell size. Importantly, Akt activation amplifies proliferation during the early stages of morphogenesis, but cannot overcome signals suppressing proliferation in late-stage cultures. Akt also cooperates with oncoproteins such as cyclin D1 or HPV E7 to promote proliferation and morphogenesis in the absence of growth factors. Pharmacological inhibition of the Akt effector, mammalian target of rapamycin (mTOR), with rapamycin prevents the morphological disruption elicited by Akt activation, including its effect on cell size and number, and the cooperative effect of Akt on oncogene-driven proliferation, indicating that mTOR function is required for the multiple biological effects of Akt activation during morphogenesis.

Key Words: Akt/PKB; mTOR; mammary acini; cell size; proliferation

The online version of this article includes supplemental material.

Abbreviations used in this paper: 3D, three-dimensional; EHS, Engelbreth-Holm-Swarm; ER, estrogen receptor; ERM, ezrin/radixin/moesin; FKHR-L1, Forkhead ligand 1; mTOR, mammalian target of rapamycin; OHT, 4-hydroxytamoxifen; TSC2, tuberous sclerosis complex 2.


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