Keratinocyte growth factor (KGF) has paracrine properties in the human prostate which stimulate epithelial cell growth. Activins have profound effects on cell growth and function in the human prostate, and are expressed in LNCaP, DU 145 and PC3 cells. LNCaP cells were characterized by immuncytochemistry, an immunoassay and polymerase chain reaction. A 3[H]thymidine assay was used with 0.01-10 nM dihydrotestosterone, 10 micro M flutamide, 1-100 ng/ml KGF and 3 nM activin. LNCaP cells expressed Ki67, PSA, cytokeratins (8, 18, 19, 14, 15) androgenreceptor but no KGF protein. LNCaP cells showed telomerase activity. Furthermore, ARmRNA (365 bp), but no KGF or KGFRmRNA were expressed. KGF ELISA detected no intracellular or secreted KGF. DHT (1, 10 and 100 nM) and KGF (10 and 100 ng/ml) significantly stimulated LNCaP cell proliferation. However, flutamide and 3 nM activin A significantly decreased cell proliferation in the presence and absence of KGF. The results of our experiments support the hypothesis that cell growth and proliferative characteristics of LNCaP cells are modulated by KGF and activin A.