Suppression of Apoptosis by Basement Membrane Requires Three-Dimensional Tissue Organization and Withdrawal from The Cell Cycle

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 93; no. 8; pp. 3509 - 3513
• Main Authors: Boudreau, Nancy, Werb, Zena, Bissell, Mina J.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 16.04.1996; National Acad Sciences; National Academy of Sciences
• Subjects: Animals; Apoptosis; Apoptosis - genetics; Apoptosis - physiology; Basement Membrane - physiology; Biochemistry; Caspase 1; Cell culture techniques; Cell cycle; Cell Cycle - genetics; Cell Cycle - physiology; Cell Differentiation - genetics; Cell Differentiation - physiology; Cell growth; Cell Line; Cells; Cellular biology; Cultured cells; Cyclins; Cysteine Endopeptidases - genetics; Epithelial Cells; Epithelium - physiology; Extracellular Matrix - physiology; Female; Gels; Genes, myc; Homeostasis - genetics; Homeostasis - physiology; Mammary Glands, Animal - cytology; Mammary Glands, Animal - physiology; Messenger RNA; Mice; Phenotype; RNA, Messenger - genetics; RNA, Messenger - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.8.3509

The basement membrane (BM) extracellular matrix induces differentiation and suppresses apoptosis in mammary epithelial cells, whereas cells lacking BM lose their differentiated phenotype and undergo apoptosis. Addition of purified BM components, which are known to induce β -casein expression, did not prevent apoptosis, indicating that a more complex BM was necessary. A comparison of culture conditions where apoptosis would or would not occur allowed us to relate inhibition of apoptosis to a complete withdrawal from the cell cycle, which was observed only when cells acquired a three-dimensional alveolar structure in response to BM. In the absence of this morphology, both the G1 cyclin kinase inhibitor p21/WAF-1 and positive proliferative signals including c-myc and cyclin D1 were expressed and the retinoblastoma protein (Rb) continued to be hyperphosphorylated. When we overexpressed either c-myc in quiescent cells or p21 when cells were still cycling, apoptosis was induced. In the absence of three-dimensional alveolar structures, mammary epithelial cells secrete a number of factors including transforming growth factor α and tenascin, which when added exogenously to quiescent cells induced expression of c-myc and interleukin-β 1-converting enzyme (ICE) mRNA and led to apoptosis. These experiments demonstrate that a correct tissue architecture is crucial for long-range homeostasis, suppression of apoptosis, and maintenance of differentiated phenotype.