Revealing the Functions of Tenascin-C in 3-D Breast Cancer Models Using Cell Biological and in Silico Approaches
Annual rept. 15 Feb 2007-14 Feb 2008
PENNSYLVANIA UNIV PHILADELPHIA
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The extracellular matrix ECM glycoprotein tenascin-C TN-C is induced in the breast stroma, where it is associated with both breast cancer development and progression, yet its role in this disease remains obscure. To investigate the effects of stromal TN-C on normal human mammary epithelium, we cultured MCF-10A cells in a three-dimensional 3-D reconstituted basement membrane Matrigel, either with or without exogenous TN-C. Whereas control cells formed polarized acinar structures, complete with a continuous basement membrane and a central lumen resulting from site-specific apoptosis, exposure to TN-C provoked selective loss of basement membrane and increased epithelial cell proliferation, without affecting apoptosis. To determine how these changes alter mammary epithelial tissue structure and function, an image analysis algorithm was developed to generate 3-D renditions of mammary acini, which were then used to assess and quantify acinar topography and volume. Although TN-C increased acinar surface roughness, it had no effect on volume. Based on these results, we hypothesized that TN-C promotes epithelial cell proliferation within the lumens of the acini, and that this process might involve c-met, a receptor tyrosine kinase which is over-expressed in breast tumors, where it is believed to affect both lumen formation and cell proliferation. Indeed, TN-C-treated acini contained filled lumens and expressed higher levels of c-met than controls. Furthermore, blockade of c-met resulted in reversion of the TN-C acinar phenotype, complete with restoration of acinar architecture, lumen formation and a decrease in proliferation that approached levels similar to those observed in controls. Importantly, human breast cancers enveloped by a TN-C-rich stroma expressed high levels of epithelial c-met when compared to normal tissue.
- Medicine and Medical Research