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Fig. 2. Signaling mechanisms studied in monotypic 3D cultures of human mammary
epithelial cell lines. The phenotypes of human mammary epithelial cells can be
readily distinguished in the context of 3D lrBM assays. After 10 days in
culture, non-malignant cells form growth-arrested, polarized acini with
central lumens, whereas malignant cells form apolar colonies of continually
growing cells that vary in size and shape depending on the degree of
tumorigenicity. A number of studies, some of which are depicted here, have
utilized this assay to explore the molecular regulation of normal breast
(e.g., lumen formation) as well as aberrant signaling during tumor progression
and/or reversion. Individual studies are referenced in the text.