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We have previously documented that adoptively transferred IL-2-activated NK (A-NK) cells can accumulate within cancer metastases. Electron microscopic studies of pulmonary metastases have revealed that adoptively transferred A-NK cells that accumulate within metastases bind to endothelial cells and are able to traverse basement membranes. We have now extended these morphologic studies. We report that rat A-NK cells produce two matrix metalloproteinases: MMP-2 and MMP-9, as determined by SDS-PAGE gelatin zymography. These activities are inhibited following incubation with BB-94 (batimastat), a specific inhibitor of matrix metalloproteinases but not with 3,4-dichloroisocoumarin, an inhibitor of neutral serine proteases. The identity of MMP-2 was confirmed by Western blots using a polyclonal Ab against human MMP-2, whereas reverse transcriptase-PCR analysis of mRNA extracts of A-NK cells has confirmed the presence of MMP-9. In addition, we report for the first time that A-NK cells can migrate through a model basement membrane-like extracellular matrix. Moreover, the ability of A-NK cells to migrate through this model basement membrane was partially inhibited by BB-94; however, BB-94 has no effect on A-NK cell-mediated cytotoxicity, suggesting that matrix metalloproteinases do not contribute to cytolytic function of A-NK cells. In sum, our studies show that A-NK cells employ BB-94-inhibitable matrix metalloproteinases to degrade extracellular matrices. This suggests that matrix metalloproteinases may play a role in the accumulation of A-NK cells within cancer metastases.

Hepatocyte growth factor (HGF), also known as scatter factor, is believed to play a primary role in liver regeneration. HGF is produced in an inactive single-chain form that can be cleaved in vitro to the active two-chain form by tissue-type and urokinase-type plasminogen (PLG) activators (tPA and uPA). We have now documented the de novo appearance of active uPA in livers from male Fischer F344 rats that underwent 70% partial hepatectomy (PHx) as early as 1 minute after surgery. Western blot analyses of protein extracts from liver remnants that were obtained immediately after surgery and periodically until 24 hours after PHx indicate that the quantity of uPA remains fairly constant in PHx samples. In contrast, the uPA receptor (uPAR) dramatically increases, beginning within 1 minute after PHx. This results in enhanced activity of uPA, as seen by direct zymography on cryostat sections. The uPA present in remnant liver homogenates from rats that underwent PHx is the primary agent that cleaves single-chain HGF to its two-chain form, because cleavage can be prevented when antibody against uPA is included in the liver homogenates. Furthermore, heterodimeric HGF, which is not present in normal liver, increases in the liver remnants from rats that underwent PHx, correlative to uPAR. The presence of active uPA is one of the earliest responses yet documented after PHx. These findings imply that both uPA and uPAR are involved in activating endogenous HGF in the regenerating livers of animals that underwent PHx.

We have recently described nongranular, cytosolic, high-molecular-weight trypsin-like (A-NKP 1) and chymotrypsin-like (A-NKP 2) proteases of interleukin-2-activated rat natural killer (A-NK) cells. A functional correlation between the inactivation of A-NKP 2 and the inhibition of rat A-NK cell-mediated cytotoxicity was found. Herein we describe the 6,000-fold purification of A-NKP 2 to apparent homogeneity following: isopycnic sucrose gradient fractionation of postnuclear supernatants, molecular sieve chromatography, and heparin-Sepharose chromatography. We also report the novel finding that A-NKP 2 as well as A-NKP 1, derived from either rat A-NK cells or the rat NK leukemic cell line CRNK-16, are constituents of the multicatalytic proteinase (MCP/proteasome) complexes of these cells. Characteristic biochemical, biophysical, and electron microscopic/ultrastructural similarity to the rat liver proteasome was observed. However, Western blot analysis using polyclonal antibodies to the rat liver proteasome clearly indicated differences in the rat hepatic proteasome and the CRNK-16-derived proteasomal subunits. The identification, characterization, and purification of A-NKP 1 and A-NKP 2, described herein, now allow for further investigation of the potential role of these proteasome components in NK cell function. Moreover, the proteasome of NK and A-NK cells can now be compared and contrasted to the granzymes of lytic granules with respect to their role in cell-mediated cytotoxicity.

The biochemical properties of heretofore uncharacterized extracellular proteases of rat interleukin-2-activated natural killer (A-NK) cells were investigated. Following p-aminobenzamidine- and D-phenylalanine-agarose affinity chromatography both trypsin- and chymotrypsin-like protease activities were found. Zymography revealed "trypsin-like" activities, with apparent molecular weights of approximately 42 kDa to 20.5 kDa, and "chymotrypsin-like" activities of approximately 27 kDa, to 22 kDa. These proteases might contribute to diverse NK cell functions, and the characteristics of these proteolytic activities are compared with those of granzymes of lytic granules and the proteasome of A-NK cells.