The effect of immune cells on the growth and development of human prostatic cancer cells was investigated. Cell proliferation of androgen-independent human prostatic cancer cells JCA-1 was reduced 30-40% with the supplementation of a growth modulating activity present in lymphocyte conditioned medium. The slower growing cells had a longer doubling time revealing a blocking for G(1) cells entering into S phase. The clonogenicity of the cells was also reduced. Displayed in parallel was altered phenotypes including the development of dendrite-like processes with less intercellular contact. Immunocytochemical staining showed significantly increased: expression of actin, vimentin and cytokeratin 8, suggesting a differentiated cell type. Activated lymphocytes were shown to require RNA synthesis for providing the modulating activity which was estimated to be 18,500-27,500 Da. The role of immune cells in growth regulation of prostatic cells is discussed.

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