Expression of collagenase IV (basement membrane collagenase) activity in murine tumor cell hybrids that differ in metastatic potential

Expression of a basement membrane collagen-degrading metalloprotease activity (collagenase IV) was studied in a series of murine cell hybrids derived from fusions between highly metastatic cells (B16-F10RR) or moderately metastatic cells (UV-2237RR) and tumorigenic cells (K-1735 clone 16) or normal cells [peritoneal macrophages (PEC) or C3H mouse embryo fibroblasts (C3H-F)]. The collagenase IV activity of the parent cells and the hybrids was assayed in vitro and compared to the metastatic propensity of the same cells evaluated in both syngeneic (C57BL/6 X C3H/HeN)F1 mice and BALB/c nude mice. The level of collagenase IV activity secreted by the parent lines correlated with their metastatic capacity. The highly metastatic B16-F10RR line secreted the highest enzyme activity, whereas the tumorigenic but nonmetastatic K-1735 clone 16 and the normal parents PEC and C3H-F secreted the lowest enzyme activity. The enzyme activity was completely inhibited with EDTA. The hybrid derived from fusion of cells from two metastatic cell lines as well as hybrids derived from a metastatic and a nonmetastatic tumor cell line expressed higher levels of collagenase IV activity than either parent, and this expression was associated with a high ability to produce metastases in both nude and syngeneic mice. Fusion of metastatic cells with normal cells produced hybrid cells that exhibited suppression of both collagenase IV activity and metastatic capacity. Collagenase IV activity and metastatic propensity can, therefore, be altered by somatic cell hybridization; in the series of hybrids examined in these experiments the expression of type IV collagen-degrading metalloprotease activity and the metastatic ability were closely correlated, which suggests that collagenase IV activity and other properties required for metastasis are genetically linked.