Cytoskeletal and Cytocontractile Protein Composition of Stromal Tissue in Normal, Hyperplastic, and Neoplastic Human Prostate

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Abstract
Monoclonal antibodies specific for protein markers of smooth muscle and nonmuscle cell differentiation were applied to cryosections of normal, hyperplastic, and neoplastic human prostate specimens in order to determine whether differences in the distribution of target antigens could be detected among the various tissues. Immunofluorescence assays showed that vimentin, desmin, smooth-muscle-type alpha-actin, and both smooth muscle and nonmuscle myosin heavy chains do not change their patterns of labeling in the stromas of normal, BPH, and carcinomatous prostates. By contrast, cytokeratin 18, a differentiation marker of simple epithelia, and to a lesser extent cytokeratin 8, was consistently found in stromal tissue of the "transition zone", but only scarcely in the stroma of the "peripheral zone" from normal prostate, and was completely unexpressed in benign hyperplasia. Prostatic carcinoma from the "peripheral zone" expressed this cytoskeletal component only in trace amounts. Moreover, in prostate showing coexistence of hyperplasia and neoplasia (in the "peripheral zone"), the stroma of BPH closely resembled the stroma surrounding the carcinoma; that is, it was completely unreactive with the anti-cytokeratin 18 antibody. Expression of cytokeratins in extraepithelial tissues has been previously correlated with the achievement of a proliferative state, notably in embryogenesis, in tissue regeneration, and in various pathological forms of proliferation and growth, including some tumors of mesenchymal origin. Our results indicate the following: (1) cells in the stromal tissue of normal prostate are of smooth muscle type and are heterogeneous as concerns cytokeratin distribution; (2) we show, for the first time, the existence of a marker that is differentially distributed in the "transition" versus "peripheral" zone; (3) the expression of cytokeratins in the stroma is lost with the development of hyperplasia and only partially recovers with neoplasia; (4) the pattern of stromal tissue, concerning cytokeratin 18 expression, does not change with different BPH locations ("transition" versus "peripheral" zone); and (5) contrary to expectations, cytokeratin 18 expression disappears in conditions presumably involving stromal cell proliferation.