In colon cancer cells fascin1 regulates adherens junction remodeling.

Adherens junctions (AJs) are a defining feature of all epithelial cells. They regulate epithelial tissue architecture and integrity, and their dysregulation is a key step in tumor metastasis. AJ remodeling is crucial for cancer progression, and it plays a key role in tumor cell survival, growth, and dissemination. Few studies have examined AJ remodeling in cancer cells consequently, it remains poorly understood and unleveraged in the treatment of metastatic carcinomas. Fascin1 is an actin-bundling protein that is absent from the normal epithelium but its expression in colon cancer is linked to metastasis and increased mortality. Here, we provide the molecular mechanism of AJ remodeling in colon cancer cells and identify for the first time, fascin1's function in AJ remodeling. We show that in colon cancer cells fascin1 remodels junctional actin and actomyosin contractility which makes AJs less stable but more dynamic. By remodeling AJs fascin1 drives mechanoactivation of WNT/ß-catenin signaling and generates "collective plasticity" which influences the behavior of cells during cell migration. The impact of mechanical inputs on WNT/ß-catenin activation in cancer cells remains poorly understood. Our findings highlight the role of AJ remodeling and mechanosensitive WNT/ß-catenin signaling in the growth and dissemination of colorectal carcinomas.

Transcriptional profiling identifies upregulated genes following induction of epithelial-mesenchymal transition in squamous carcinoma cells.

During the progression of head and neck squamous cell carcinoma (HNSCC), the induction of an epithelial-mesenchymal transition (EMT) program may play a critical role in the dissemination of cells from the primary tumor to distant metastatic foci. The process of EMT involves the activation of several important genes and pathways to help maintain survival and growth and evolve into highly invasive and metastatic variants. In this study, expression microarray analysis identified a set of 145 upregulated genes in EMT-like HNSCC cells. Some of the strongly upregulated transcripts include genes that are reportedly involved in invasion and metastasis, such as DOCK10, LOX, ROBO1 and SRGN. Importantly, the Tbx3 gene, a member of the T-box transcription factor, was strongly upregulated in SCC cells displaying an EMT-like phenotype compared to cells with an epitheloid, non-EMT behavior. Tbx3 was also found to be strongly upregulated at the protein and gene expression level in an experimental model of snail-induced EMT cells. In addition, siRNA-induced Tbx3 depletion modestly suppressed cell invasion while enhancing Tbx3-mediated resistance to anoikis. Our findings provide evidence that Tbx3 overexpression promotes SCC cell survival displaying an EMT phenotype. This set of newly identified genes that are modulated during EMT-like conversion may be important diagnostic biomarkers during the process of HNSCC progression.

ERß alters the chemosensitivity of luminal breast cancer cells by regulating p53 function.

Estrogen receptor α (ERα)-positive breast cancers tend to develop resistance to both endocrine therapy and chemotherapy. Despite recent progress in defining molecular pathways that confer endocrine resistance, the mechanisms that regulate chemotherapy response in luminal tumors remain largely elusive. Luminal tumors often express wild-type p53 that is a major determinant of the cellular DNA damage response. Similar to p53, the second ER subtype, ERß, has been reported to inhibit breast tumorigenesis by acting alone or in collaboration with p53. However, a synergistic mechanism of action has not been described. Here, we suggest that ERß relies on p53 to elicit its tumor repressive actions in ERα-positive breast cancer cells. Upregulation of ERß and treatment with ERß agonists potentiates the tumor suppressor function of p53 resulting in decreased survival. This effect requires molecular interaction between the two proteins that disrupts the inhibitory action of ERα on p53 leading to increased transcriptional activity of p53. In addition, we show that the same interaction alters the chemosensitivity of endocrine-resistant cells including their response to tamoxifen therapy. Our results suggest a collaboration of ERß and p53 tumor suppressor activity in breast cancer cells that indicates the importance of ligand-regulated ERß as a tool to target p53 activity and improve the clinical management of resistant disease.

By moonlighting in the nucleus, villin regulates epithelial plasticity.

Villin is a tissue-specific, actin-binding protein involved in the assembly and maintenance of microvilli in polarized epithelial cells. Conversely, villin is also linked with the loss of epithelial polarity and gain of the mesenchymal phenotype in migrating, invasive cells. In this study, we describe for the first time how villin can switch between these disparate functions to change tissue architecture by moonlighting in the nucleus. Our study reveals that the moonlighting function of villin in the nucleus may play an important role in tissue homeostasis and disease. Villin accumulates in the nucleus during wound repair, and altering the cellular microenvironment by inducing hypoxia increases the nuclear accumulation of villin. Nuclear villin is also associated with mouse models of tumorigenesis, and a systematic analysis of a large cohort of colorectal cancer specimens confirmed the nuclear distribution of villin in a subset of tumors. Our study demonstrates that nuclear villin regulates epithelial-mesenchymal transition (EMT). Altering the nuclear localization of villin affects the expression and activity of Slug, a key transcriptional regulator of EMT. In addition, we find that villin directly interacts with a transcriptional corepressor and ligand of the Slug promoter, ZBRK1. The outcome of this study underscores the role of nuclear villin and its binding partner ZBRK1 in the regulation of EMT and as potential new therapeutic targets to inhibit tumorigenesis.

Both the anti- and pro-apoptotic functions of villin regulate cell turnover and intestinal homeostasis.

In the small intestine, epithelial cells are derived from stem cells in the crypts, migrate up the villus as they differentiate and are ultimately shed from the villus tips. This process of proliferation and shedding is tightly regulated to maintain the intestinal architecture and tissue homeostasis. Apoptosis regulates both the number of stem cells in the crypts as well as the sloughing of cells from the villus tips. Previously, we have shown that villin, an epithelial cell-specific actin-binding protein functions as an anti-apoptotic protein in the gastrointestinal epithelium. The expression of villin is highest in the apoptosis-resistant villus cells and lowest in the apoptosis-sensitive crypts. In this study we report that villin is cleaved in the intestinal mucosa to generate a pro-apoptotic fragment that is spatially restricted to the villus tips. This cleaved villin fragment severs actin in an unregulated fashion to initiate the extrusion and subsequent apoptosis of effete cells from the villus tips. Using villin knockout mice, we validate the physiological role of villin in apoptosis and cell extrusion from the gastrointestinal epithelium. Our study also highlights the potential role of villin's pro-apoptotic function in the pathogenesis of inflammatory bowel disease, ischemia-reperfusion injury, enteroinvasive bacterial and parasitic infections.

Revisiting epithelial-to-mesenchymal transition through adenoid cystic carcinoma.

Adenoid cystic carcinoma (ACC) has a 5-year survival rate of 90%. The 15-year survival rate drops to 10% due to recurrence and invasion. ACC has three subtypes: cribriform, tubular, and solid. The cribriform subtype has the best prognosis and the solid subtype has the worst prognosis. By immunohistochemistry of tissue sections, we showed that the solid form expresses αvß6 integrin and tenascin-C, which are known promoters of epithelial-to-mesenchymal transition (EMT). We also defined two ACC cell lines with the characteristics of the cribriform and solid subtype. The SACC83 cells grow in basaloid-like clusters and express high levels of E-cadherin. In contrast, the ACCh cells are more myoepithelial-like and express high levels of vimentin and of αvß6 integrin. The ACCh cells are highly invasive and this behavior is dependent upon the αvß6 integrin function. Our results suggest that the transition from the cribriform to solid form may occur through EMT.

The rational design of inhibitors of nitric oxide formation by inducible nitric oxide synthase.

A series of compounds was rationally designed as inhibitors of dimer formation of the inducible isoform of nitric oxide synthase, and subsequent nitric oxide production. The conformation of two fragments obtained from a crystal structure was utilized to design a tether connecting those same two fragments. The resulting compounds were potent dimerization inhibitors that bound to the enzyme in a similar conformation as the fragments.