Negative control of epithelial cell proliferation by prostatic stroma.

The influence of prostatic fibroblasts on the growth of the prostatic carcinoma cell lines PC-3 and LNCaP was examined. In a double layer soft agar system, clonal growth of both cell lines was inhibited by all prostatic fibroblasts tested, irrespective of whether they were derived from malignant or non malignant prostate tissue. Irradiated fibroblasts and quiescent fibroblasts showed similar effects. The finding that growth was also inhibited in the presence of fibroblasts conditioned medium suggests that the observed effects were mediated by a diffusable growth inhibiting factor. Organ-specific production was suggested by the observation that skin fibroblasts stimulated rather than inhibited PC-3 cell growth. These findings indicate a negative control of epithelial cell proliferation by prostatic stroma.