Human breast carcinoma cells cultured in the presence of serum shed membrane vesicles rich in gelatinolytic activities.

Human breast carcinoma cell lines, 8701-BC and MCF-7, in culture shed membrane vesicles with similar morphology. Vesicles shed in the presence of serum were rich in gelatinolytic activities, but not those obtained in the absence of serum. Zymographic analyses of the vesicles from 8701-BC and MCF-7, using gelatin as substrate, showed three predominant activities at 68-kDa, 97-kDa, and above 200-kDa. The ratio of the three activities was similar in the vesicles recovered from the two cell lines, but the vesicles from 8701-BC cells contained greater amounts of activities than those from MCF-7 cells. Optimal pH and sensitivity to protease inhibitors suggest that all gelatinolytic activities detected in vesicles are metalloproteinases. Treatment of the vesicles extracts with 4-aminophenylmercuric acetate and comparison with the purified enzyme indicate that 97-kDa gelatinase is the precursor of matrix metalloproteinase-9 (gelatinase B). These results support the early hypothesis that vesicle shedding from the plasma membrane may participate in metastatic cascade of cancer cells.