Collagenolytic activities of squamous cell carcinoma of the skin.

Abstract

Summary Electron microscopic and physicochemical studies on collagenolytic activities of squamous cell carcinomas of the skin were performed. Collagen and basal lamina degeneration was evident in the stroma immediately surrounding the squamous cell carcinomas. With the exception of fine filament aggregations with periodical crossbands at 1000-A intervals, amorphous debris, and intact elastic fibers, the peri-squamous cell carcinoma stroma was empty. A large number of villous projections from the advancing border of the squamous cell carcinomas perforated the basal lamina. An amorphous coat of the elastic fibers produced hemidesmosomes with tumor cells. Electron microscopic examination of segment-long-spacing tropocollagen prepared from squamous cell carcinoma homogenate-treated calf skin collagen revealed molecules cleaved at the β 2 2 region. Squamous cell carcinoma homogenates released significantly higher radioactivity from proline- 14 C-labeled guinea pig collagen than did the normal skin control. Caseinolytic activity of squamous cell carcinoma homogenate was higher than that of the normal skin, but soybean trypsin inhibitor inhibited collagenolysis only 12.7%. Known collagenase inhibitors such as normal human serum (10%) ethylenediaminetetraacetic acid (0.01 m), and cysteine (0.01 m), on the other hand, inhibited collagenolysis 75, 70, and 57.2%, respectively. Disc electrophoresis of the reaction mixture showed degradation bands of α and β chains. Specific viscosity of tropocollagen decreased by 42% after 24 hr of incubation with squamous cell carcinoma homogenate. The melting temperature midpoint of tropocollagen dropped about 10° as a result of incubation with squamous cell carcinoma homogenate. The crude enzyme activities, as measured by the radioactivity released from proline- 14 C-labeled salt-extracted guinea pig collagen, increased linearly with respect to the time and the enzyme concentration. The optimal pH for the crude enzyme was determined to be pH 6.5. Elastase activity in the tumor homogenates was not increased above the normal skin level. Numerous aggregates of fine filaments with periodical cross-bands were observed in the stroma. These results strongly suggest that squamous cell carcinomas of the skin contain specific collagenase that is active in vivo .