Annexin A2 is a pleiotropic calcium- and anionic phospholipid-binding protein that exists as a monomer and as a heterotetrameric complex with the plasminogen receptor protein, S100A10. Annexin A2 has been proposed to play a key role in many processes including exocytosis, endocytosis, membrane organization, ion channel conductance, and also to link F-actin cytoskeleton to the plasma membrane. Despite an impressive list of potential binding partners and regulatory activities, it was somewhat unexpected that the annexin A2-null mouse should show a relatively benign phenotype. Studies with the annexin A2-null mouse have suggested important functions for annexin A2 and the heterotetramer in fibrinolysis, in the regulation of the LDL receptor and in cellular redox regulation. However, the demonstration that depletion of annexin A2 causes the depletion of several other proteins including S100A10, fascin and affects the expression of at least sixty-one genes has confounded the reports of its function. In this review we will discuss the annexin A2 structure and function and its proposed physiological and pathological roles.

Accumulation of extracellular hyaluronan (HA) and its processing enzyme, the hyaluronidase Hyal1, predicts invasive, metastatic progression of human prostate cancer. To dissect the roles of hyaluronan synthases (HAS) and Hyal1 in tumorigenesis and metastasis, we selected nonmetastatic 22Rv1 prostate tumor cells that overexpress HAS2, HAS3, or Hyal1 individually, and compared these cells with co-transfectants expressing Hyal1 ؉ HAS2 or Hyal1 ؉ HAS3. Cells expressing only HAS were less tumorigenic than vector control transfectants on orthotopic injection into mice. In contrast, cells co-expressing Hyal1 ؉ HAS2 or Hyal1 ؉ HAS3 showed greater than sixfold and twofold increases in tumorigenesis, respectively. Fluorescence and histological quantification revealed spontaneous lymph node metastasis in all Hyal1 transfectant-implanted mice, and node burden increased an additional twofold when Hyal1 and HAS were co-expressed. Cells only expressing HAS were not metastatic. Thus, excess HA synthesis and processing in concert accelerate the acquisition of a metastatic phenotype by prostate tumor cells. Intratumoral vascularity did not correlate with either tumor size or metastatic potential. Analysis of cell cycle progression revealed shortened doubling times of Hyal1-expressing cells. Both adhesion and motility on extracellular matrix were diminished in HA-overproducing cells; however , motility was increased twofold by Hyal1 expression and fourfold to sixfold by Hyal1/HAS co-expression , in close agreement with observed metastatic potential. This is the first comprehensive examination of these enzymes in a relevant prostate cancer microenvironment. (Am J

The tumor microenvironment (TME) is now being widely accepted as the key contributor to a range of processes involved in cancer progression from tumor growth to metastasis and chemoresistance. The extracellular matrix (ECM) and the proteases that mediate the remodeling of the ECM form an integral part of the TME. Plasmin is a broad-spectrum, highly potent, serine protease whose activation from its precursor plasminogen is tightly regulated by the activators (uPA, uPAR, and tPA), the inhibitors (PAI-1, PAI-2), and plasminogen receptors. Collectively, this system is called the plasminogen activation system. The expression of the components of the plasminogen activation system by malignant cells and the surrounding stromal cells modulates the TME resulting in sustained cancer progression signals. In this review, we provide a detailed discussion of the roles of plasminogen activation system in tumor growth, invasion, metastasis, and chemoresistance with specific emphasis on their role in the TME. We particularly review the recent highlights of the plasminogen receptor S100A10 (p11), which is a pivotal component of the plasminogen activation system.

Hyaluronidases are a family of endolytic glycoside hydrolases that cleave the ␤1-4 linkage between N-acetylglucosamine and glucuronic acid in hyaluronan polymers via a substrate-assisted mechanism. In humans, turnover of hyaluronan by this enzyme family is critical for normal extracellular matrix remodeling. However, elevated expression of the Hyal1 isozyme accelerates tumor growth and metastatic progression. In this study, we used structural information, site-directed mutagenesis, and steady state enzyme kinetics to probe molecular determinants of human Hyal1 function. Mutagenesis of active site residues Glu 131 and Tyr 247 to Gln and Phe, respectively, eliminated activity at all hyaluronan concentrations (to 125 M or 2.5 mg/ml). Collectively, these studies define key components of Hyal1 active site catalysis, and structural factors critical for stability. Such detailed understanding will allow rational design of enzyme modulators. Conservative mutagenesis of Asp

Prostate cancer progression can be predicted in human tumor biopsies by abundant hyaluronan (HA) and its processing enzyme, the hyaluronidase HYAL1. Accumulation of HA is dictated by the balance between expression levels of HA synthases, the enzymes that produce HA polymers, and hyaluronidases, which process polymers to oligosaccharides. Aggressive prostate tumor cells express 20-fold higher levels of the hyaluronan synthase HAS3, but the mechanistic relevance of this correlation has not been determined. We stably overexpressed HAS3 in prostate tumor cells. Adhesion to extracellular matrix and cellular growth kinetics in vitro were significantly reduced. Slow growth in culture was restored either by exogenous addition of hyaluronidase or by stable HYAL1 coexpression. Coexpression did not improve comparably slow growth in mice, however, suggesting that excess hyaluronan production by HAS3 may alter the balance required for induced tumor growth. To address this, we used a tetracycline-inducible HAS3 expression system in which hyaluronan production could be experimentally controlled. Adjusting temporal parameters of hyaluronan production directly affected growth rate of the cells. Relief from growth suppression in vitro but not in vivo by enzymatic removal of HA effectively uncoupled the respective roles of hyaluronan in growth and angiogenesis, suggesting that growth mediation is less critical to establishment of the tumor than early vascular development. Collectively results also imply that HA processing by elevated HYAL1 expression in invasive prostate cancer is a requirement for progression.Despite improved detection and diagnosis of prostate cancer, this disease remains the second leading cause of malignant mortality in United States males (1, 2). Metastasis may occur with no prior indication of an invasive tumor (3), so prostate cancer progression is difficult to predict. Changes in levels of extracellular matrix molecules such as hyaluronan (HA), 2 a high molecular weight polysaccharide, and its processing enzyme, the hyaluronidase HYAL1, within the prostate extracellular matrix have been correlated to invasive prostate cancer progression (4 -11). The molecular mechanisms underlying this correlation could provide important insights for therapeutic development or improved diagnosis of prostate cancer.HA production is a tightly regulated process that impacts cellular transformation and motility during development (12)(13)(14). Dynamic HA turnover within tissues controls many acute processes such as wound healing or immune function. HA accumulation is the outcome of a balance between the activity of HA synthases (HAS), enzymes that synthesize the linear polymers (15), and hyaluronidases, which process the polymers to biologically potent oligosaccharides (16). Excess quantities of large HA polymers have been reported to suppress cellular growth (17, 18) and angiogenesis (19,20), whereas processed oligosaccharides dramatically stimulate angiogenesis (21-23), and fully degraded oligosaccharides induce apoptosis (1...