Paracrine growth stimulation of androgen-responsive Shionogi Carcinoma 115 by its autonomous subline (Chiba Subline 2).

Shionogi Carcinoma 115 cells (SC 115 cells) and Chiba Subline 2 cells (CS 2 cells) are clones of an androgen-responsive mouse tumor cell line and its autonomous subline, respectively. Since it was reported that the growth of cells from SC 115 was regulated by an androgen-induced fibroblast growth factor (FGF)-like peptide (1), the present study was aimed at examining whether a similar growth factor was secreted by CS 2 cells in the absence of testosterone. Although SC 115 cells did not grow in the serum-free medium without androgens, SC 115 cells could proliferate in mixed culture with CS 2 cells, suggesting stimulation of SC 115 cells by CS 2 cells. It was shown that CS 2 cells secreted a growth factor without the influence of testosterone, and this factor promoted the growth of SC 115 and CS 2 cells, as well as that of BALB/3T3 cells. The factor was partially purified from serum-free conditioned medium obtained from cultures of CS 2 cells. It showed an affinity for heparin, stability to heat and acid treatments, a decrease in activity when anti-basic FGF antibody was added to cultures, and an estimated molecular weight of approximately 50,000. Therefore, the factor seemed to have the nature of an FGF-like peptide. It was concluded that, in the absence of testosterone, CS 2 cells produced an FGF-like growth factor which controlled the growth of both CS 2 cells and parent SC 115 cells, in autocrine and paracrine manners, respectively.