Requirement of basement membrane for the suppression of programmed cell death in mammary epithelium

Abstract

Apoptosis is an active mechanism of cell death required for normal tissue homeostasis. Cells require survival signals to avoid the engagement of apoptosis. In the mammary gland, secretory epithelial cells are removed by apoptosis during involution. This cell loss coincides with matrix metalloproteinase activation and basement membrane degradation. In this paper we describe studies that confer a new role for basement membrane in the regulation of cell phenotype. We demonstrate that the first passage epithelial cells isolated from pregnant mouse mammary gland die by apoptosis in culture, but that cell death is suppressed by basement membrane. The correct type of extracellular matrix was required, since only a basement membrane, not plastic or a collagen I matrix, lowered the rate of apoptosis. Attachment to a matrix per se was not sufficient for survival, since apoptotic cells were observed when still attached to a collagen I substratum. Experiments with individually isolated cells confirmed the requirement of basement membrane for survival, and demonstrated that survival is enhanced by cell-cell contact. A function-blocking anti-beta1 integrin antibody doubled the rate of apoptosis in single cells cultured with basement membrane, indicating that integrin-mediated signals contributed to survival. We examined the cell death-associated genes bcl-2 and bax in mammary epithelia, and found that although the expression of Bcl-2 did not correlate with cell survival, increased levels of Bax were associated with apoptosis. We propose that basement membrane provides a survival stimulus for epithelial cells in vivo, and that loss of interaction with this type of matrix acts as a control point for cell deletions that occur at specific times during development, such as in mammary gland involution.

CircRNA screening and ceRNA network construction for milk fat metabolism in dairy cows

“…The PI3K-Akt signaling pathway regulates multiple cellular activities, including cell growth, proliferation, survival, and metabolism ( 42 ). The interaction between the extracellular matrix (ECM) and mammary epithelial cells is essential for regulating cell proliferation, polarity, and apoptosis ( 43 – 45 ). Endocytosis is critical for regulating plasma membrane protein and lipid homeostasis, and endocytosis defects may lead to an irregular accumulation of proteins on the cytoplasmic membrane and lipids ( 46 ).…”

Mapping lung tumor cell drug responses as a function of matrix context and genotype using cell microarrays

“…It is also possible that activation of the JAK/STAT pathway by ECM presentation plays a role in this context given prior studies showing b1-integrin mediated reduction in apoptosis in mammary epithelium in particular. [56][57][58][59] Future efforts utilizing this platform could include primary tumor cells from animal or patient-derived xenograft models as well as clinical transcriptomic and proteomic data. For example, additional mechanistic studies could be aimed at examining the processes underlying differential caspase-3 cleavage, or potential regulation of other apoptotic machinery, within the distinct ECM domains.…”

Rac1 controls cell turnover and mammary gland reversibility in post-partum involution

“…Primary MECs were harvested from either 15.5-17.5 day pregnant mice for alveolar cultures or 12 week old virgin mice for ductal cultures and cultured as described in (31).…”