TGF-beta induces formation of F-actin cores and matrix degradation in human breast cancer cells via distinct signaling pathways

Transforming growth factor beta regulates many biological processes including cell motility and invasion. Podosomes are specialized F-actin rich structures found in normal cells, such as osteoclasts and macrophages. Tumor cells often form related structures called invadopodia that are thought to promote invasion and metastasis. Here we show that human breast cancer cells organize F-actin rich structures in response to transforming growth factor beta that colocalize with areas of extracellular matrix degradation. We further show that organizing the complex of proteins needed to form these structures requires signaling through phosphatidylinositide 3-kinase and Src kinase, while activating the proteases involved in degradation of extracellular matrix requires extracellular signal-regulated kinase signaling, and that each of these pathways is activated by transforming growth factor beta in CA1D human breast cancer cells.     

Dynamic control of TGF-beta signaling and its links to the cytoskeleton

Transforming growth factor beta (TGF-beta) regulates cellular behavior in embryonic and adult tissues. TGF-beta binding to serine/threonine kinase receptors on the plasma membrane activates Smad molecules and additional signaling proteins that coordinately regulate gene expression or cytoplasmic processes such as cytoskeletal dynamics. In turn, the activity and duration of the Smad pathway seems to be regulated by cytoskeletal components, which facilitate the shuttling process that segregates Smad proteins in the cytoplasm and nucleus. We discuss mechanisms and models that aim at explaining the coordination between several components of the signaling network downstream of the TGF-beta signal.     

Proteomics of breast cancer: principles and potential clinical applications

Progresses in screening, early diagnosis, prediction of aggressiveness and of therapeutic response or toxicity, and identification of new targets for therapeutic will improve survival of breast cancer. These progresses will likely be accelerated by the new proteomic techniques. In this review, we describe the different techniques currently applied to clinical samples of breast cancer and the most important results obtained with the two most popular proteomic approaches in translational research (tissue microarrays and SELDI-TOF).     

Proteomics of membrane receptors and signaling

Receptors represent an abundant class of integral membrane proteins that transmit information on various types of signals within the cell. Assemblages of receptors and their interacting proteins (receptor complexes) have emerged as important units of signal transduction for various types of receptors including G protein coupled, ligand-gated ion channel, and receptor tyrosine kinase. This review aims to summarize the major approaches and findings of receptor proteomics. Isolation and characterization of receptor complexes from cells has become common using the methods of immunoaffinity-, ligand-, and tag-based chromatography followed by MS for the analysis of enriched receptor preparations. In addition, tools such as stable isotope labeling have contributed to understanding quantitative properties and PTMs to receptors and their interacting proteins. As data from studies on receptor-protein interactions considerably expands, complementary approaches such as bioinformatics and computational biology will undoubtedly play a significant role in defining cellular and network functions for various types of receptor complexes. Findings from receptor proteomics may also shed light on the mechanism of action for pharmacological drugs and can be of value in understanding molecular pathologies of disease states.     

The ROCK signaling and breast cancer metastasis

Metastasis is the predominant cause of death in most breast cancer patients. The molecular mechanisms underlying metastasis from primary tumors to distant organs are not clearly characterized. In this review, we depict the role of ROCK signaling in regulating cell motility and growth, and discuss the contribution of this signaling to breast cancer metastasis.     

Ski/Sno and TGF-beta signaling

Transforming growth factor-beta is a potent inhibitor of epithelial cell proliferation. Proteins involved in TGF-beta signaling are bona fide tumor suppressors and many tumor cells acquire the ability to escape TGF-beta growth inhibition through the loss of key signaling transducers in the pathway or through the activation of oncogenes. Recent studies indicate that there is a specific connection between the TGF-beta signaling pathway and the Ski/SnoN family of oncoproteins. We summarize evidence that Ski and SnoN directly associate with Smad proteins and block the ability of the Smads to activate expression of many if not all TGF-beta-responsive genes. This appears to cause abrogation of TGF-beta growth inhibition in epithelial cells.     

Proteomics of breast cancer: From differential to functional analysis

From differential analysis to identify biomarkers, to functional analysis for finding new therapeutic targets, proteomics bring new comprehensive information for a better understanding of the molecular basis of oncology and new perspectives for the clinic. However the major limitation of proteomic investigations, more generally of post-genomic approaches, remains the molecular and cellular complexity of the mammary gland that is still a major challenge.     

TGF-beta and cancer

The relationships between transforming growth factor-beta (TGF-beta) and cancer are varied and complex. The paradigm that is emerging from the experimental evidence accumulated over the past decade or so is that TGF-beta can play two different and opposite roles with respect to the process of malignant progression. During early stages of carcinogenesis, TGF-beta acts predominantly as a potent tumor suppressor and may mediate the actions of chemopreventive agents such as retinoids and nonsteroidal anti-estrogens. However, at some point during the development and progression of malignant neoplasms, bioactive TGF-betas make their appearance in the tumor microenvironment and the tumor cells escape from TGF-beta-dependent growth arrest. In many cases, this resistance to TGF-beta is the consequence of loss or mutational inactivation of the genes that encode signaling intermediates. These include the types I and II TGF-beta receptors, as well as receptor-associated and common-mediator Smads. The stage of tumor development or progression at which TGF-beta-resistant clones come to dominate the tumor cell population in different types of neoplasm remains to be defined. The phenotypic switch from TGF-beta-sensitivity to TGF-beta-resistance that occurs during carcinogenesis has several important implications for cancer prevention and treatment.     

TGF-beta and cancer

TGF-beta signaling regulates tumorigenesis and in human cancer its signaling pathways are often modified during tumor progression. Prior to initiation and early during progression TGF-beta acts upon the epithelium as a tumor suppressor, however at later stages it is often a tumor promoter. Over the years, many studies have focused on the epithelial cell autonomous role for TGF-beta, however, TGF-beta is not strictly limited to this compartment in vivo. Recent studies addressing TGF-beta mediated stromal-epithelial interactions have significantly improved our understanding related to the regulation of cancer. In addition, stromal fibroblast cell autonomous effects have been observed in response to TGF-beta stimulation. According to the current literature and experimental evidence, TGF-beta is a potent ligand that regulates carcinoma initiation, progression and metastasis through a broad and complex spectrum of interdependent interactions.     

c-Met在人乳腺癌组织中的表达及其与明胶酶的关系

目的研究c—Met蛋白在人乳腺癌组织中的表达及其临床意义,探讨其与乳腺癌明胶酶（MMP-2和MMP-9）关系。方法应用免疫组织化学方法检测86例乳腺癌组织c—Met蛋白的表达情况,分析它们与患者临床病理特征和预后的关系;使用siRNA技术特异性下调乳腺癌细胞内源性c—Met后,westernblot方法检测乳腺癌细胞MMP-2和MMP-9表达水平。结果人乳腺癌c—Met蛋白表达阳性率为58．1％,其表达与肿瘤淋巴结转移和临床分期均呈显著正相关（P〈O．01）,与患者总生存期和无复发生存期均呈负相关（P〈O．01）;相关性分析显示：乳腺癌c—Met和MMP-2及MMP-9表达均呈显著正相关（r=0．314和0．322,P〈O．01）;使用siRNA特异性下调乳腺癌MDA—M13-231细胞c—Met表达后,MMP-2和MMP-9表达也显著降低。结论乳腺癌c—Met表达状况与侵袭转移密切相关,其功能可能是通过调控MMP-2和MMP-9表达而发挥作用。     

Proteomics of breast carcinoma

Beast cancer is the most diagnosed cancer in women, accounting for approximately 40,000 deaths annually in the USA. Significant advances have been made in the areas of detection and treatment, but a significant number of breast cancers are detected late. The advent of proteomics provides the hope of discovering novel biological markers that can be used for early detection, disease diagnosis, prognostication and prediction of response to therapy. Several proteomics technologies including 2D-PAGE, 2D-DIGE, ICAT, SELDI-TOF, MudPIT and protein arrays have been used to uncover molecular mechanisms associated with breast carcinoma at the global level, and a number of these technologies, particularly the SELDI-TOF hold promise as a proteomic approach that can be applied at the bedside for discovering protein patterns that distinguish disease and disease-free states with high sensitivity and specificity. Laser microdissection, a method for selection of homogenous cell populations, coupled to 2D-DIGE or MudPIT constitute a new proteomics-based paradigm for detecting disease in pathology specimens and monitoring disease response to therapy. This review describes proteomics technologies, and their application in the proteomic analysis of breast carcinoma.     

Alterations in components of the TGF-beta superfamily signaling pathways in human cancer

Signaling by transforming growth factor-beta (TGF-beta) superfamily ligands to the nucleus is mediated by type I and type II receptors and the intracellular signal transducers, the Smads. Alteration of some of the components of these pathways has been observed in human tumors. These alterations can be deletions or mutations, or downregulation of components that act positively in the pathway, or alternatively, amplification or overexpression of inhibitors of the pathways. The selection of these alterations during tumor progression and their correlation with clinical outcomes, such as survival, risk of recurrence after tumor resection or tendency for metastatic spread, suggest that many are involved in tumor progression. Here, we review the genetic alterations and epigenetic modifications that occur in different components of the TGF-beta superfamily signaling pathways in human tumors and we discuss their correlation with clinical outcome. The evidence suggests that not all alterations of the TGF-beta superfamily signaling pathway components in human cancer have an equivalent effect on tumor progression and we discuss what implications this has for our understanding of the role of TGF-beta signaling in human cancer.     

Proteomics of breast cancer: the quest for markers and therapeutic targets

Proteomics of breast cancer has already delivered significant data in terms of proteome profiling in addition to the identification of a few proteins of potential interest for diagnosis and treatment. With more pathological and experimental situations being studied, it now enters into a new phase dominated by the concepts of deep proteome analysis and the definition of protein-protein interaction networks leading to mammary cell deregulation and cancer progression. Together, what could be called "Systems Proteomics", integrating with information from the genomics and the physiopathology, is clearly emerging to become the frame for future investigations. However, difficulties ahead should not be underestimated. First, the proteome is complex, and current tools are still far from providing a definitive solution for its exploration. Second, breast cancer is a multifactorial disease which is so diverse that a great deal of time and efforts will be necessary to define its associated proteome modifications and translate it into practical applications for the clinic.