Abstract
The paracrine influence of prostatic stroma on the proliferation of prostatic epithelial cells was investigated. Stromal cells from the human prostate have previously been shown to inhibit anchorage-dependent as well as anchorage-independent growth of the prostatic tumour epithelial cell lines PC-3 and LNCaP. Antiproliferative activity, mediated by a diffusible factor in the stromal cell conditioned medium, was found to be produced specifically by prostatic stromal cells. In the present study the characteristics of this factor were examined. It is demonstrated that prostate stroma-derived inhibiting factor is an acid- and heat-labile, dithiothreitol-sensitive protein. Although some similarities with type beta transforming growth factor (TGF-beta)-like inhibitors are apparent, evidence is presented that the factor is not identical to TGF-beta or to the TGF-beta-like factors activin and inhibin. Absence of TGF-beta activity was shown by the lack of inhibitory response of the TGF-beta-sensitive mink lung cell line CCL-64 to prostate stromal cell conditioned medium and to concentrated, partially purified preparations of the inhibitor. Furthermore, neutralising antibodies against TGF-beta 1 or TGF-beta 2 did not cause a decline in the level of PC-3 growth inhibition caused by partially purified inhibitor. Using Northern blot analyses, we excluded the involvement of inhibin or activin. It is concluded that the prostate stroma-derived factor may be a novel growth inhibitor different from any of the currently described inhibiting factors.
Highlights
Using the monoclonal antibody NCLSD3 (Organon, Oss, The Netherlands) reacting with keratin 8, 18 and 19, we found that the number of positive cells in these cultures (BPH as well as prostatic carcinoma (PC)) never exceeded 5%, indicating that most cells were of nonepithelial origin (Kooistra et al, 1995b)
Effect ofprostatic stromal cell CM and partially purified inhibitor on the growth ofprostatic tumour epithelial cells We previously reported the inhibition of anchorageindependent growth of the hormone-insensitive prostatic carcinoma cell line PC-3, as well as the hormone-responsive prostatic carcinoma cell line LNCaP, by co-cultured prostatic stromal cells (Kooistra et al, 1991)
Following the observation that epithelium loses its growth capacity when separated from the stroma (Franks et al, 1970), it has become increasingly clear that both autocrine and paracrine factors produced by epithelial and stromal cells play an important role in the local control of prostatic growth
Summary
Stromal cell culturesSurgically obtained tissue specimens from histologically proven benign prostatic hyperplasia (BPH) and prostatic carcinoma (PC) were cut into pieces (approximately 1 mm x 2 mm), and placed in 35 mm Petri dishes (Nunc) containing 1.5 ml of basal medium: Earle's minimum essential medium (Gibco Europe, Breda, The Netherlands) supplemented with 10% FCS (Biological Industries, Beth Haemak, Israel), 2 mM glutamine, penicillin and streptomycin (all from Gibco Europe). Cultures were maintained in a humidified incubator at 37°C in 5% carbon dioxide/air. The initial halo of epithelial cells grown from these explant cultures became overgrown with fibroblast-like cells within several weeks. In order to minimise the number of epithelial cells in our cultures we used only prostatic stromal cells of passage number 4-9 in this study. Using the monoclonal antibody NCLSD3 (Organon, Oss, The Netherlands) reacting with keratin 8, 18 and 19, we found that the number of positive cells in these cultures (BPH as well as PC) never exceeded 5%, indicating that most cells were of nonepithelial origin (Kooistra et al, 1995b)
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