Lack of the latent transforming growth factor beta binding protein in malignant, but not benign prostatic tissue.

Transforming growth factor beta (TGF-beta) is a family of proteins which act as a potent growth inhibitor for most cell types including epithelial cells. TGF-beta is synthesized as latent high molecular weight complexes, composed of TGF-beta, the NH2-terminal part of the TGF-beta precursor and the third molecule, the latent TGF-beta binding protein (LTBP). We here ascertain that TGF-beta is expressed in human prostatic cancer tissue as well as in cystectomized prostatic tissue and in materials from transurethral resections with benign prostatic hyperplasia, analyzed by immunohistochemistry. TGF-beta is observed in both epithelial cells and stromal cells. No significant correlation was obtained between TGF-beta expression in tumor cells and their degree of differentiation. However, analysis by immunohistochemistry using antibodies against LTBP revealed that specimens from histopathologically verified human prostatic cancer are mostly negative for this molecule, although it is expressed in cystectomized prostatic and benign prostatic hyperplasia tissues. These results indicate that in cystectomized prostatic and benign prostatic hyperplasia tissues, TGF-beta may be produced in a complex associated with LTBP; whereas in prostatic carcinoma, TGF-beta is produced without associating with LTBP. The biological significance of the production of TGF-beta in relation to LTBP and the possible association with prognosis are discussed.