Collagenase activity in rabbit carcinoma: Cell source and cell interactions

Fibroblast‐like cells (F‐cells) and epithelial‐like (E‐cells) derived from cultures of rabbit VX‐2 carcinoma released collagenase in both active and latent forms in serum‐free medium at a level higher than that of normal rabbit fibroblast cultures. The enhanced capacity of the F‐cells to release the enzyme, however, continued only for a few passages and then decreased significantly to a low level similar to that of the normal fibroblasts. The enzyme‐release by the E‐cells continued for a few more passages at a relatively moderate level, higher than that of normal fibroblasts. The release of collagenase in cultures of F‐cells was enhanced by the presence of E‐cells in mixed cultures as well as by medium conditioned by the E‐cells type. Addition of cytochalasin B at 2 μg/ml did not significantly effect the enzyme activity released in the cultures. Serum from tumor‐bearing rabbits appeared to stimulate the release of enzyme activity in cultures of either cell type.