Effects of 12-Hydroxyeicosatetraenoic Acid on Release of Cathepsin B and Cysteine Proteinase Inhibitors from Malignant Melanoma Cells
The cysteine proteinase cathepsin B as well as the endogenous inhibitors of this enzyme have been implicated in the progression of tumors from a premalignant to a malignant state (for review see 1,2). Activity of cathepsin B has been shown to be elevated in parallel with malignancy or metastatic potential of both human and rodent tumors. These increases in cathepsin B activity correspond in part to increases in mRNA for cathepsin B and in part to reduced regulation by the endogenous low Mr cysteine proteinase inhibitors (CPIs). The inhibition constants for the interaction between stefin A purified from human tumors and cysteine proteinases are an order of magnitude greater than those for stefin A purified from human liver. Most properties of tumor cathepsin B appear to be similar to those of cathepsin B from normal tissues. However, the subcellular distribution of cathepsin B and CPIs is altered in tumors, resulting in association of cathepsin B and CPIs with plasma membrane fractions or in release of CPIs and of high Mr forms of cathepsin B (native and latent) into the extracellular mileau.
KeywordsCysteine Proteinase Cysteine Proteinase Inhibitor Plasma Membrane Fraction B16a Cell Amelanotic Melanoma
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