The origins of the mesenchymal cells participating in tissue repair and pathological processes, notably tissue fibrosis, tumor invasiveness, and metastasis, are poorly understood. However, emerging evidence suggests that epithelial-mesenchymal transitions (EMTs) represent one important source of these cells. As we discuss here, processes similar to the EMTs associated with embryo implantation, embryogenesis, and organ development are appropriated and subverted by chronically inflamed tissues and neoplasias. The identification of the signaling pathways that lead to activation of EMT programs during these disease processes is providing new insights into the plasticity of cellular phenotypes and possible therapeutic interventions.

/pdf/the-basics-of-epithelial-mesenchymal-transition-xe9crzoewf.pdf

The basics of epithelial-mesenchymal transition

Purpose ABI-007, the first biologically interactive albumin-bound paclitaxel in a nanameter particle, free of solvents, was compared with polyethylated castor oil–based standard paclitaxel in patients with metastatic breast cancer (MBC). This phase III study was performed to confirm preclinical studies demonstrating superior efficacy and reduced toxicity of ABI-007 compared with standard paclitaxel. Patients and Methods Patients were randomly assigned to 3-week cycles of either ABI-007 260 mg/m2 intravenously without premedication (n = 229) or standard paclitaxel 175 mg/m2 intravenously with premedication (n = 225). Results ABI-007 demonstrated significantly higher response rates compared with standard paclitaxel (33% v 19%, respectively; P = .001) and significantly longer time to tumor progression (23.0 v 16.9 weeks, respectively; hazard ratio = 0.75; P = .006). The incidence of grade 4 neutropenia was significantly lower for ABI-007 compared with standard paclitaxel (9% v 22%, respectively; P < .001) de...

https://ascopubs.org/doi/pdf/10.1200/JCO.2005.04.937

Phase III Trial of Nanoparticle Albumin-Bound Paclitaxel Compared With Polyethylated Castor Oil–Based Paclitaxel in Women With Breast Cancer

Extracellular matrix structure.

The epithelial to mesenchymal transition (EMT) converts epithelial cells into migratory and invasive cells and is a fundamental event in morphogenesis. Although its relevance in the progression of cancer and organ fibrosis had been debated until recently, the EMT is now established as an important step in the metastatic cascade of epithelial tumors. The similarities between pathological and developmental EMTs validate the embryo as the best model to understand the molecular and cellular mechanisms involved in this process, identifying those that are hijacked during the progression of cancer and organ degeneration. Our ever-increasing understanding of how transcription factors regulate the EMT has revealed complex regulatory loops coupled to posttranscriptional and epigenetic regulatory programs. The EMT is now integrated into the systemic activities of whole organisms, establishing links with cell survival, stemness, inflammation, and immunity. In addition, the EMT now constitutes a promising target for the treatment of cancer and organ-degenerative diseases.

/pdf/the-ins-and-outs-of-the-epithelial-to-mesenchymal-transition-1ywsd15l3u.pdf

The Ins and Outs of the Epithelial to Mesenchymal Transition in Health and Disease

http://histologia.ugr.es/pdf/EM%20Voulgari.pdf

Epithelial-mesenchymal transition in cancer metastasis: Mechanisms, markers and strategies to overcome drug resistance in the clinic

Secreted protein, acidic and rich in cysteine (SPARC) is a multifunctional secreted protein that regulates cell-cell and cell-matrix interactions, leading to alterations in cell adhesion, motility, and proliferation. Although SPARC is expressed in epithelial cells, its ability to regulate epithelial cell growth remains largely unknown. We show herein that SPARC strongly inhibited DNA synthesis in transforming growth factor (TGF)-beta-sensitive Mv1Lu cells, whereas moderately inhibiting that in TGF-beta-insensitive Mv1Lu cells (i.e., R1B cells). Overexpression of dominant-negative Smad3 in Mv1Lu cells, which abrogated growth arrest by TGF-beta, also attenuated growth arrest stimulated by SPARC. Moreover, the extracellular calcium-binding domain of SPARC (i.e., SPARC-EC) was sufficient to inhibit Mv1Lu cell proliferation but not that of R1B cells. Similar to TGF-beta and thrombospondin-1, treatment of Mv1Lu cells with SPARC or SPARC-EC stimulated Smad2 phosphorylation and Smad2/3 nuclear translocation: the latter response to all agonists was abrogated in R1B cells or by pretreatment of Mv1Lu cells with neutralizing TGF-beta antibodies. SPARC also stimulated Smad2 phosphorylation in MB114 endothelial cells but had no effect on bone morphogenetic protein-regulated Smad1 phosphorylation in either Mv1Lu or MB114 cells. Finally, SPARC and SPARC-EC stimulated TGF-beta-responsive reporter gene expression through a TGF-beta receptor- and Smad2/3-dependent pathway in Mv1Lu cells. Collectively, our findings identify a novel mechanism whereby SPARC inhibits epithelial cell proliferation by selectively commandeering the TGF-beta signaling system, doing so through coupling of SPARC-EC to a TGF-beta receptor- and Smad2/3-dependent pathway.

SPARC Inhibits Epithelial Cell Proliferation in Part through Stimulation of the Transforming Growth Factor-β–Signaling System

Epithelial–mesenchymal transition (EMT) is a normal physiological process that regulates tissue development, remodeling and repair; however, aberrant EMT also elicits disease development in humans, including lung fibrosis, rheumatoid arthritis and cancer cell metastasis. Transforming growth factor-β (TGF-β) is a master regulator of EMT in normal mammary epithelial cells (MECs), wherein this pleiotropic cytokine also functions as a potent suppressor of mammary tumorigenesis. In contrast, malignant MECs typically evolve resistance to TGF-β-mediated cytostasis and develop the ability to proliferate, invade and metastasize when stimulated by TGF-β. It therefore stands to reason that establishing how TGF-β promotes EMT may offer new insights into targeting the oncogenic activities of TGF-β in human breast cancers. By monitoring alterations in the actin cytoskeleton and various markers of EMT, we show here that the TGF-β gene target, fibulin-5 (FBLN5), initiates EMT and enhances that induced by TGF-β. Whereas normal MECs contain few FBLN5 transcripts, those induced to undergo EMT by TGF-β show significant upregulation of FBLN5 messenger RNA, suggesting that EMT and the dedifferentiation of MECs override the repression of FBLN5 expression in polarized MECs. We also show that FBLN5 stimulated matrix metalloproteinase expression and activity, leading to MEC invasion and EMT, to elevated Twist expression and to reduced E-cadherin expression. Finally, FBLN5 promoted anchorage-independent growth in normal and malignant MECs, as well as enhanced the growth of 4T1 tumors in mice. Taken together, these findings identify a novel EMT and tumor-promoting function for FBLN5 in developing and progressing breast cancers.

/pdf/fibulin-5-initiates-epithelial-mesenchymal-transition-emt-1kb1a9x6wc.pdf

Fibulin-5 initiates epithelial–mesenchymal transition (EMT) and enhances EMT induced by TGF-β in mammary epithelial cells via a MMP-dependent mechanism

Transforming growth factor-β (TGF-β) is a potent suppressor of mammary epithelial cell (MEC) proliferation and is thus an inhibitor of mammary tumor formation. Malignant MECs typically evolve resistance to TGF-β-mediated growth arrest, enhancing their proliferation, invasion, and metastasis when stimulated by TGF-β. Recent findings suggest that therapeutics designed to antagonize TGF-β signaling may alleviate breast cancer progression, thereby improving the prognosis and treatment of breast cancer patients. We identified the cysteine protease inhibitor cystatin C (CystC) as a novel TGF-β type II receptor antagonist that inhibits TGF-β binding and signaling in normal and cancer cells. We hypothesized that the oncogenic activities of TGF-β, particularly its stimulation of mammary epithelial–mesenchymal transition (EMT), can be prevented by CystC. Retroviral infection was used to constitutively express CystC or a CystC mutant impaired in its ability to inhibit cathepsin protease activity (namely Δ14CystC) in murine NMuMG MECs and in normal rat kidney (NRK) fibroblasts. The effect of recombinant CystC administration or CystC expression on TGF-β stimulation of NMuMG cell EMT in vitro was determined with immunofluorescence to monitor rearrangements of actin cytoskeletal architecture and E-cadherin expression. Soft-agar growth assays were performed to determine the effectiveness of CystC in preventing TGF-β stimulation of morphological transformation and anchorage-independent growth in NRK fibroblasts. Matrigel invasion assays were performed to determine the ability of CystC to inhibit NMuMG and NRK motility stimulated by TGF-β. CystC and Δ14CystC both inhibited NMuMG cell EMT and invasion stimulated by TGF-β by preventing actin cytoskeletal rearrangements and E-cadherin downregulation. Moreover, both CystC molecules completely antagonized TGF-β-mediated morphological transformation and anchorage-independent growth of NRK cells, and inhibited their invasion through synthetic basement membranes. Both CystC and Δ14CystC also inhibited TGF-β signaling in two tumorigenic human breast cancer cell lines. Our findings show that TGF-β stimulation of initiating metastatic events, including decreased cell polarization, reduced cell–cell contact, and elevated cell invasion and migration, are prevented by CystC treatment. Our findings also suggest that the future development of CystC or its peptide mimetics hold the potential to improve the therapeutic response of human breast cancers regulated by TGF-β.

/pdf/the-use-of-cystatin-c-to-inhibit-epithelial-mesenchymal-4eknirkm2c.pdf

Barbara J. Schiemann

Papers

SPARC Inhibits Epithelial Cell Proliferation in Part through Stimulation of the Transforming Growth Factor-β–Signaling System

Fibulin-5 initiates epithelial–mesenchymal transition (EMT) and enhances EMT induced by TGF-β in mammary epithelial cells via a MMP-dependent mechanism

The use of cystatin C to inhibit epithelial–mesenchymal transition and morphological transformation stimulated by transforming growth factor-β