Mutant K-ras Regulates Cathepsin B Localization on the Surface of Human Colorectal Carcinoma Cells

Cathepsin B protein and activity are known to localize to the basal plasma membrane of colon carcinoma cells following the appearance of K-ras mutations. Using immunofluorescence and subcellular fractionation techniques and two human colon carcinoma cell lines—one with a mutated K-ras allele (HCT 116) and a daughter line in which the mutated allele has been disrupted (HKh-2)—we demonstrate that the localization of cathepsin B to caveolae on the surface of these carcinoma cells is regulated by mutant K-ras. In HCT 116 cells, a greater percentage of cathepsin B was distributed to the caveolae, and the secretion of cathepsin B and pericellular (membrane-associated and secreted) cathepsin B activity were greater than observed in HKh-2 cells. Previous studies established the light chain of annexin II tetramer, p11, as a binding site for cathepsin B on the surface of tumor cells. The deletion of active K-ras in HKh-2 cells reduced the steady-state levels of p11 and caveolin-1 and the distribution of p11 to caveolae. Based upon these results, we speculate that cathepsin B, a protease implicated in tumor progression, plays a functional role in initiating proteolytic cascades in caveolae as downstream components of this cascade (e.g., urokinase plasminogen activator and urokinase plasminogen activator receptor) are also present in HCT 116 caveolae

Bone Microenvironment Modulates Expression and Activity of Cathepsin B in Prostate Cancer

Prostate cancers metastasize to bone leading to osteolysis. Here we assessed proteolysis of DQ-collagen I (a bone matrix protein) and, for comparison, DQ-collagen IV, by living human prostate carcinoma cells in vitro. Both collagens were degraded, and this degradation was reduced by inhibitors of matrix metallo, serine, and cysteine proteases. Because secretion of the cysteine protease cathepsin B is increased in human breast fibroblasts grown on collagen I gels, we analyzed cathepsin B levels and secretion in prostate cells grown on collagen I gels. Levels and secretion were increased only in DU145 cells—cells that expressed the highest baseline levels of cathepsin B. Secretion of cathepsin B was also elevated in DU145 cells grown in vitro on human bone fragments. We further investigated the effect of the bone microenvironment on cathepsin B expression and activity in vivo in a SCID-human model of prostate bone metastasis. High levels of cathepsin B protein and activity were found in DU145, PC3, and LNCaP bone tumors, although the PC3 and LNCaP cells had exhibited low cathepsin B expression in vitro. Our results suggest that tumor-stromal interactions in the context of the bone microenvironment can modulate the expression of the cysteine protease cathepsin B

Cathepsin B and tumor proteolysis: contribution of the tumor microenvironment

Tumor-stromal interactions induce expression of matrix metalloproteinases and serine proteases and, as shown recently, the cysteine protease cathepsin B. We speculate that such interactions upregulate the transcription factor Ets1, resulting in increased cathepsin B expression. This would be consistent with the observed concomitant upregulation of matrix metalloproteinases and serine proteases as well as with the ability of extracellular matrices and their binding partners to alter cathepsin B expression and secretion. Using a confocal assay to analyze the contribution of tumor-stromal interactions to proteolysis, we have been able to confirm enhanced degradation of extracellular matrices by all three classes of proteases

Pirates, merchants and anarchists : representations of international business

This article considers the relationship between historical and fictional accounts of piracy, and relates them to contemporary issues about the legitimacy of states and global business. I begin by showing how privateers were gradually distinguished into pirates and navies. At the same time, the pirate becomes a character in the popular imagination, a `trickster' figure on the side of the people, and against authority.The second main section of the paper moves from `histor y' to `representation' and shows how the image of the pirate moved from a wild character on the edge of the world, to a stock cliché for Hollywood swashbucklers. I then investigate the legacy of radical histories and representations of piracy, focusing particularly on the idea of alternative organization on the ship and the pirate utopias on the land. The final section pulls together the historical figure, the stock character and the radical rogue in order to suggest that the pirate can mean what we want him (or to her) to mean. Nonetheless, the biggest historical irony is that the golden age pirate emerges at the beginnings of international business, and is only wiped out when the state and the businessman strike an alliance that lasts to the present day