Bim regulation of lumen formation in cultured mammary epithelial acini is targeted by oncogenes.
Epithelial cells organize into cyst-like structures that contain a spherical monolayer of cells that enclose a central lumen. Using a three-dimensional basement membrane culture model in which mammary epithelial cells form hollow, acinus-like structures, we previously demonstrated that lumen formation is achieved, in part, through apoptosis of centrally localized cells. We demonstrate that the proapoptotic protein Bim may selectively trigger apoptosis of the centrally localized acinar cells, leading to temporally controlled lumen formation. Bim is not detectable during early stages of three-dimensional mammary acinar morphogenesis and is then highly upregulated in all cells of acini, coincident with detection of apoptosis in the centrally localized acinar cells. Inhibition of Bim expression by RNA interference transiently blocks luminal apoptosis and delays lumen formation. Oncogenes that induce acinar luminal filling, such as ErbB2 and v-Src, suppress expression of Bim through a pathway dependent on Erk-mitogen-activated protein kinase; however, HPV 16 E7, an oncogene that stimulates cell proliferation but not luminal filling, is unable to reduce Bim expression. Thus, Bim is a critical regulator of luminal apoptosis during mammary acinar morphogenesis in vitro and may be an important target of oncogenes that disrupt glandular epithelial architecture.
Reginato
Mauricio J
MJ
Harvard Medical School, Department of Cell Biology, 240 Longwood Ave., Boston, MA 02115, USA.
Mills
Kenna R
KR
Becker
Esther B E
EB
Lynch
Danielle K
DK
Bonni
Azad
A
Muthuswamy
Senthil K
SK
Brugge
Joan S
JS
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins; D018929:Cell Culture Techniques; D002454:Cell Differentiation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D018734:Genes, erbB-2 / Q000502:physiology*; D016391:Genes, src / Q000502:physiology*; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology / Q000254:growth & development*; D008565:Membrane Proteins; D009024:Morphogenesis; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D051020:bcl-X Protein
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D002352:Carrier Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D008565:Membrane Proteins; D015688:Oncogene Protein pp60(v-src); D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D018719:Erb-b2 Receptor Tyrosine Kinases; D051020:bcl-X Protein; C494811:BCL2L1 protein, human; C000606775:BCL2L11 protein, human