No abstract

Radiolabeled substrate degradation assays and gelatin zymography are routinely employed to assay 72 kDa gelatinase A (MMP-2) and 92 kDa gelatinase B (MMP-9) in biological fluids. Enzyme-linked immunosorbent assays (ELISA) have recently been developed for the quantitation of these matrix metalloproteinases (MMP). In this study, we have compared ELISA to standard substrate degradation assays for measurement of MMP-2 and MMP-9 in human plasma and tumor-conditioned media. Gelatin Sepharose chromatography and gel filtration chromatography were employed as partial purification procedures for MMP-2 and MMP-9. The ELISA data for MMP-2 and MMP-9 are linear on a log:log regression curve over a wide range of MMP concentrations and are specific for the designated gelatinase, with no overlap detected with related metalloproteinases. The minimum detectable concentrations of MMP-2 and MMP-9 were approximately 0.5 ng/ml and 0.2 ng/ml, respectively, in the ELISA as compared to 4 ng/ml and 3 ng/ml, respectively, in gelatin zymography. The [3H]gelatin degradation assay required a combination of > 50 ng/ml of MMP-2 and MMP-9 for detection. Although gelatin zymography was less sensitive than ELISA (primarily due to the smaller sample volume employed) and was more difficult to quantitate, this procedure offers the important advantage of being able to distinguish between latent and activated gelatinases.

Cancer cells have the capacity to lyse erythrocytes by a cell-contact-requiring phenomenon. Subcellular fractionation procedures have revealed that the hemolytic principle resides in the cancer cell plasma membrane. In this study we report the detergent extraction of a potent hemolytic factor from the plasma membranes of ras-oncogene-transformed fibroblasts. Ammonium-sulfate partitioning (60-100%) of detergent-extracted proteins was used to enrich hemolytic activity. Tumor membrane Hemolytic Factor (mTHF) was inactivated by treatment with papain, suggesting that it is a protein. mTHF was inhibited by serum, but was unaffected by extremes of temperature and pH, also by metal chelation with EDTA. Surface radio-iodination of tumor cells and isolation of cell organelles was used to characterize the outer plasma membrane localization of mTHF. mTHF retained hemolytic activity when reconstituted into stable phospholipid vesicles. Pre-incubation of mTHF with red cell ghosts led to an abrogation of hemolytic activity. mTHF-induced hemolysis consists of a 2-stage phenomenon: an early binding step, followed by hemolysis after 4 hr.