Reactive Stroma in Human Prostate Cancer: Induction of Myofibroblast Phenotype and Extracellular Matrix Remodeling 1 Jennifer A. Tuxhorn, Gustavo E. Ayala, Megan J. Smith, Vincent C. Smith, Truong D. Dang, and David R. Rowley 2 Departments of Molecular and Cellular Biology [J. A. T., T. D. D., D. R. R.] and Pathology [G. E. A., M. J. S., V. C. S.] Baylor College of Medicine, Houston, Texas 77030 ABSTRACT Purpose: Generation of a reactive stroma environment occurs in many human cancers and is likely to promote tumorigenesis. However, reactive stroma in human prostate cancer has not been defined. We examined stromal cell phenotype and expression of extracellular matrix compo- nents in an effort to define the reactive stroma environ- ment and to determine its ontogeny during prostate cancer progression. Experimental Design: Normal prostate, prostatic intra- epithelial neoplasia (PIN), and prostate cancer were exam- ined by immunohistochemistry. Tissue samples included radical prostatectomy specimens, frozen biopsy specimens, and a prostate cancer tissue microarray. A human prostate stromal cell line was used to determine whether transform- ing growth factor 1 (TGF-1) regulates reactive stroma. Results: Compared with normal prostate tissue, reac- tive stroma in Gleason 3 prostate cancer showed increased vimentin staining and decreased calponin staining (P < 0.001). Double-label immunohistochemistry revealed that reactive stromal cells were vimentin and smooth muscle -actin positive, indicating the myofibroblast phenotype. In addition, reactive stroma cells exhibited elevated collagen I synthesis and expression of tenascin and fibroblast activa- tion protein. Increased vimentin expression and collagen I synthesis were first observed in activated periacinar fibro- blasts adjacent to PIN. Similar to previous observations in prostate cancer, TGF-1-staining intensity was elevated in PIN. In vitro, TGF-1 stimulated human prostatic fibro- blasts to switch to the myofibroblast phenotype and to ex- press tenascin. Conclusions: The stromal microenvironment in human prostate cancer is altered compared with normal stroma and exhibits features of a wound repair stroma. Reactive stroma is composed of myofibroblasts and fibroblasts stimulated to express extracellular matrix components. Reactive stroma appears to be initiated during PIN and evolve with cancer progression to effectively displace the normal fibromuscular stroma. These studies and others suggest that TGF-1 is a candidate regulator of reactive stroma during prostate can- cer progression. INTRODUCTION Activation of the host stromal microenvironment is pre- dicted to be a critical step in adenocarcinoma growth and progression (1–5). Several human cancers have been shown to induce a stromal reaction or desmoplasia as a component of carcinoma progression. However, the specific mechanisms of stromal cell activation are not known, and the extent to which stroma regulates the biology of tumorigenesis is not fully un- derstood. In cancers where a stromal reaction has been ob- served, it seems that the response is similar, if not identical, to a generic wound repair response (6). In wound repair, stromal cells exhibit elevated production of ECM 3 components, growth factors, and matrix remodeling enzymes to create a growth- promoting microenvironment (7). Similarly, reactive stroma in cancer would be predicted to enhance tumor progression by stimulating angiogenesis and by promoting cancer cell survival, proliferation, and invasion (5, 8 –12). Indeed, two recent studies have shown that prostate stromal cells stimulate the develop- ment and rate of human prostate tumorigenesis in mouse xe- nograft models (13, 14). Accordingly, it is important to identify and characterize reactive stroma in cancer to establish key regulators of reactive stroma and to delineate the specific mech- anisms through which reactive stroma affects carcinoma progression. An initial step in understanding mechanisms of the stromal reaction in tumor progression is to fully define the reactive stroma phenotype and its formation. Although poorly under- stood in most cancers, reactive stroma has been described in breast and colon carcinoma (9 –12). In these cancers, reactive stroma is a mix of fibroblasts, myofibroblasts, endothelial cells, and immune cells. Although all of these cells potentially affect tumorigenesis, myofibroblasts are of particular interest. Myofi- Received 11/1/01; revised 5/13/02; accepted 6/3/02. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 This work was supported by NIH Grants RO1-CA58093, RO1- DK45909, SPORE CA58204, and UO1-CA84296. 2 To whom requests for reprints should be addressed, at Department of Molecular and Cellular Biology, Baylor College of Medicine Houston, TX 77030. Phone: (713) 798-6220; Fax: (713) 790-1275; E-mail: drowley@bcm.tmc.edu. 3 The abbreviations used are: ECM, extracellular matrix; FAP, fibroblast activation protein; MMP, matrix metalloproteinase; TGF, transforming growth factor; PIN, prostatic intraepithelial neoplasia; SPORE, special- ized program of research excellence; sm -actin, smooth muscle - actin; DAPI, 4',6 diamidino-2-phenylindole; CAF, carcinoma-associ- ated fibroblast. 2912 Vol. 8, 2912–2923, September 2002 Clinical Cancer Research Research. on November 28, 2021. © 2002 American Association for Cancer clincancerres.aacrjournals.org Downloaded from