Phenotypic reversion or death of cancer cells by altering signaling pathways in three-dimensional contexts.
BACKGROUND
We previously used a three-dimensional (3D) reconstituted basement membrane (rBM) assay to demonstrate that tumorigenic HMT-3522 T4-2 human breast cells can be induced to form morphologically normal structures ("reversion") by treatment with inhibitors of beta1 integrin, the epidermal growth factor receptor (EGFR), or mitogen-activated protein kinase (MAPK). We have now used this assay to identify reversion and/or death requirements of several more aggressive human breast cancer cell lines.


METHODS
Breast tumor cell lines MCF7, Hs578T, and MDA-MB-231 were cultured in 3D rBM and treated with inhibitors of beta1 integrin, MAPK, or phosphatidylinositol 3-kinase (PI3K). MDA-MB-231 cells, which lack E-cadherin, were transfected with an E-cadherin cDNA. The extent of reversion was assessed by changes in morphology and polarity, growth in 3D rBM or soft agar, level of invasiveness, and tumor formation in nude mice.


RESULTS
All three cell lines showed partial reversion (MCF7 the greatest and Hs578T the least) of tumorigenic properties treated with a single beta1 integrin, MAPK, or PI3K inhibitor. Combined inhibition of beta1 integrin and either PI3K or MAPK resulted in nearly complete phenotypic reversion (MDA-MB-231, MCF7) or in cell death (Hs578T). E-cadherin-transfected MDA-MB-231 cells showed partial reversion, but exposure of the transfectants to an inhibitor of beta1 integrin, PI3K, or MAPK led to nearly complete reversion.


CONCLUSIONS
The 3D rBM assay can be used to identify signaling pathways that, when manipulated in concert, can lead to the restoration of morphologically normal breast structures or to death of the tumor cells, even highly metastatic cells. This approach may be useful to design therapeutic intervention strategies for aggressive breast cancers.
D000818:Animals; D001485:Basement Membrane / Q000378:metabolism* / Q000648:ultrastructure; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D001973:Bromodeoxyuridine; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion; D016923:Cell Death / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D003114:Colony-Forming Units Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009374:Neoplasms, Experimental / Q000378:metabolism* / Q000473:pathology / Q000628:therapy*; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism
D015820:Cadherins; D004791:Enzyme Inhibitors; D019012:Integrin beta1; D014746:Vimentin; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; D020559:Monomeric GTP-Binding Proteins; D001973:Bromodeoxyuridine
Non-programmatic