Matrix metalloproteinases (MMPs) in fresh human prostate tumour tissue and organ-cultured prostate tissue: Levels of collagenolytic and gelatinolytic MMPs are low, variable and different in fresh tissue versus organ-cultured tissue

Abstract

Summary Prostate tissue was obtained from 22 radical prostatectomies (performed for clinical management of prostate carcinoma) immediately after surgery. A small piece of tissue was fixed immediately in formalin and used for routine histology while a second piece was frozen in OCT and used for immuno-histochemistry. Another small piece was used for isolation of epithelial and stromal cells. The remainder of the tissue was cut into 2 × 2 mm pieces and incubated in organ culture for 8 days. In organ culture, non-malignant, basal epithelial cells underwent a proliferative response. This was accompanied by de-differentiation of glandular structures and by migration of epithelial cells across the surface of the tissue. Erosion of the basement membrane could also be seen in places, but was not widespread. Invasion of epithelial cells into the adjacent stroma was not evident. Production of matrix metalloproteinases (MMPs) with gelatinolytic activity or collagenolytic activity was assessed in organ culture and compared to expression patterns in fresh tissue. MMP-1 (interstitial collagenase) and MMP-9 (92-kDa gelatinase B) were undetectable or low in fresh tissue specimens. Both enzymes were detected in organ culture and both increased over time. Even after 6 days, however, there was only a low level of gelatin-hydrolytic activity and no measurable collagenhydrolytic activity. In past studies we used organ cultures of normal skin and malignant skin tumours (basal cell carcinomas) to help elucidate the role of collagenolytic and gelatinolytic MMPs in epithelial cell invasion (Varani et al, 2000). Compared to MMP levels observed in skin, levels of these enzymes in prostate are low. The low level of collagenolytic and gelatinolytic MMPs in fresh prostate tissue and in organcultured prostate tissue may help explain why there is little tissue destruction in many primary prostate tumours and why the majority of such tumours remain confined to the prostate for extended periods. Although these past studies clearly indicate that several MMPs are elaborated in prostate tumours and suggest differences between malignant and non-malignant tissue, the heterogeneity in prostate tumour presentation and the variability in the analytical methods used make elucidating the relationship between enzyme elaboration and disease-state difficult to ascertain. Furthermore, the presence of active forms of the enzymes has not been established in these studies, and the biological significance of the reported differences is unclear. In the present study, a combination of approaches has been employed to assess expression of collagenolytic and gelatinolytic MMPs in prostate tissue removed for treatment of prostate carcinoma. We report here that gelatinolytic and collagenolytic MMPs can be detected in freshly isolated prostate tissue or in short-term (2-3 day) organ culture. Expression is heterogeneous from tissue to tissue, consistent with the variation in disease presentation. Expression patterns in fresh tissue and organ-cultured tissue also differ. E...

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