Transforming growth factor beta 1 and its receptor types I and II. Comparison in human normal prostate, benign prostatic hyperplasia, and prostatic carcinoma

An immunohistochemical and semiquantitative comparative study of transformi ng growth factor beta 1 (TGF-beta 1) and its receptor types I (TGF-beta RI) and II (TGF-beta RII) was carried out in normal prostates and in the prost ates from men with benign prostatic hyperplasia (BPH), and men with prostat ic adenocarcinoma. Immunoreaction to TGF-beta 1 was limited to the basal ep ithelial cells in the normal prostates. Some cells in the connective tissue stroma were also stained. In BPH immunolabelling was also observed in colu mnar (secretory) cells of the epithelium. In prostatic adenocarcinoma, all epithelial cell types were intensely immunostained. Some stromal cells were also stained. Immunostaining to TGF-beta RI was only present in the basal cells in normal prostates. In BPH, this immunoreaction was found in the who le epithelium and in some stromal cells. In prostatic cancer, the immunosta ining pattern for this receptor was similar to that of BPH but more intense in the epithelial cells. Immunoreactivity to TGF-beta RII appeared in some basal cells and some scattered columnar cells of the normal prostate epith elium. In the BPH sections, this pattern was maintained, and a weak immunol abelling was also observed in the stroma. In prostate cancer, all epithelia l cells appeared intensely labelled. In the stroma, immunolabelling was sim ilar to that of the BPH specimens. The results of the present study suggest that, in normal prostates, only the basal cells of the epithelium posses b oth receptor types, and hence can transduce TGF-beta 1 signal intracellular ly. The basal cells can also secrete this growth factor which would act as an autocrine inhibitory growth factor for them. In addition, TGF-beta 1 is secreted in some zones by stromal cells, acting then as a paracrine growth factor for basal cells in those areas. In BPH, in addition to the basal cel ls, some secretory columnar cells also secrete TGF-beta 1 and possess both types of TGF-beta 1 receptors, and thus, both epithelial cell types are sus ceptible to TGF-beta 1 action. Since both receptor types are also present i n some stromal cells, these cells also perform an autocrine secretion, in a ddition to their paracrine secretion to the epithelial cells. TGF-beta RIIs seem to be more numerous than TGF-beta RIs and this lead us to hypothesize that these incomplete receptors might be a protection against the inhibiti on caused by TGF-beta 1 action. In prostatic carcinoma all cell types displ ay the same characteristics as in BPH, although both receptor types are fou nd in similar numbers, and thus, the above mentioned protection would not o ccur.