TRANSFORMED MURINE LEYDIG-CELLS IN SERUM-FREE CULTURE - USEFUL MODEL FOR ANALYSES OF STEROID HORMONE-INDUCED CELL-GROWTH AND CELL MORPHOLOGY (REVIEW)

A clonal cell line has been established from estrogen-induced testicular Leydig cell tumor of BALB/c mouse. This cell line termed as B-1F can be maintained in a serum-free culture condition without any authentic growth factor. The growth of B-1F cells is significantly enhanced by estrogen, androgen or retinoic acid. Biochemical and Northern blot analyses reveal that B-1F cells contain respective receptors for these stimulants, although estrogen receptor has an interesting mutation. The simultaneous addition of these stimulants in combination fails to elevate the maximum levels of B-1F cell growth, suggesting that these stimulants would share some common pathway to stimulate B-1F cell growth. One possible step affected by these stimulants is mapped to 5-lipoxygenase since inhibitors of this enzyme can stimulate B-1F cell growth and estrogen stimuli can lower its activity. B-1F cells grow in a serum-free medium as a cell clump irrespective of the presence of growth stimulants. Interestingly, the addition of low concentrations of elastase or trypsin in the medium changes the cell morphology from a round to well spreaded shape. Furthermore, treatment of conditioned medium from B-1F cell culture with trypsin or elastase results in an appearance of cell-spreading activity. In addition, a relatively high concentration of elastase abolishes estrogen-induced enhancemant of B-1F cell growth. In conclusion, a serum-free culture of B-1F cells can provide us with a model system quite useful for studying the effects of physiologically active molecules on cancer cells.