Collagenase stimulation in cocultures of human fibroblasts and human tumor cells.

Cocultures of human fibroblasts with 3 different human tumor cell lines exhibited high levels of collagenase activity against type I collagen compared to individual cultures of each cell type. For LX-1 lung carcinoma cells maximum stimulation occurred at a ratio of tumor cells to fibroblasts of 0.5:1. These cocultures contained 15-50 times more collagenase activity than the sum of the individual cultures. Conditioned medium from the LX-1 cells stimulated the fibroblasts to an extent similar to that obtained in the cocultures. Conditioned medium from the fibroblasts did not stimulate the tumor cells. Thus human tumor cells secrete a factor(s) which stimulates collagenase production by human fibroblasts.