The second commonest cause of cancer death in the Western world is attributed to prostate cancer (Jensen et al, 1990). It is well documented that prostatic carcinoma shows a predilection to metastasize to the bone marrow (Jacobs, 1983). Metastatic prostate cancer remains an incurable disease and as such, is a massive clinical problem. There is clearly a need to elucidate the factors underlying the spread of prostate cancer, particularly to the skeleton.It has been suggested that the bone marrow microenvironment is conducive to the growth of prostate cancer cells, which nonselectively enter the bone marrow from the circulation (Galasko, 1981;Jacobs, 1983;Paget, 1989;Body, 1992). However, the strikingly consistent pattern of prostate metastasis within the red marrow suggests that this process may in fact be regulated (Fidler et al, 1978). The mechanism of metastasis is a complex multi-step process that is not fully understood. One critical step in this mechanism may be the attachment to and extravasation through endothelial barriers by malignant cells possibly leading to selective metastatic sites. Tumour cell binding to endothelium involves two distinct steps, an initial docking step mediated via lectin-carbohydrate interactions followed by an integrin-mediated locking step (Honn and Tang, 1992). Several endothelial and tumour adhesion molecules have been associated with metastasis. In particular the integrins β1, α2 and α5 have been shown to be expressed by prostate epithelial cells and bone marrow cells (Soligo et al, 1990;Nagle et al, 1994;Rokhlin and Cohen, 1995). The carbohydrate sialyl Lewis X has also been associated with breast and lung cancer metastasis and its ligand P selectin is found on endothelial cells (Soligo et al, 1990). Some lung, brain, liver and ovary metastatic tumour cells have been demonstrated to bind selectively to endothelial cells isolated from lung, brain, liver and ovary respectively (Nicolson and Winkelhake, 1975;Auerbach et al, 1987). These studies suggest an active regulatory role for the endothelium in metastasis (Zetter, 1990).We have shown previously that primary prostatic epithelia from both benign and malignant tissue show an accelerated growth rate within bone marrow stroma compared to control stroma (Lang et al, 1998) and also that integrin α2β1 is a major contributor to the binding of primary prostatic epithelial cells to bone marrow stroma (Lang et al, 1997). This pattern of primary prostatic epithelial cell adhesion (α2β1) is mimicked by the prostate cell line, PC3 (Kostenuik et al, 1996) and our experiments were therefore conducted with this cell line. These studies have now been extended to develop a model to investigate the interactions of prostatic epithelial cells (primary and cell lines) with the bone marrow endothelium. MATERIALS AND METHODS MaterialsGeneral chemicals were purchased from Sigma (Poole, UK). Tissue culture media and supplements were obtained from Gibco Summary Prostate cancer shows a propensity to form secondary tumours within the bone marrow. Such ...

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Prostate cancers ability to invade and grow in bone marrow stroma is thought to be due in part to degradative enzymes. The formation of prostate skeletal metastases have been reproduced in vitro by growing co-cultures of prostatic epithelial cells in bone marrow stroma. Expression of urokinase plasminogen activator, matrix metalloproteinase 1 and 7 by prostatic epithelial cells were identified using immunocytochemistry. Also, in vivo tissue sections from human prostatic bone marrow metastases were stained. To establish the role of these enzymes on colony formation, inhibitory antibodies directed against urokinase plasminogen activator, matrix metalloproteinase 1 and matrix metalloproteinase 7 were added into primary prostatic epithelial cells and bone marrow stroma co-cultures. All prostatic epithelial cell cultures stained positively for matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator. Generally prostatic epithelial cells derived from malignant tissues showed increased staining in comparison to epithelia derived from non-malignant tissue. In agreement with in vitro co-cultures, the in vivo tissue sections of prostate bone marrow metastases showed positive staining for all three enzymes. Inhibition studies demonstrated that blocking matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator function reduced the median epithelial colony area significantly in bone marrow stroma co-cultures in vitro. Using a human ex-vivo model we have shown that matrix metalloproteinase 1, matrix metalloproteinase 7 and urokinase plasminogen activator play an important role in the establishment of prostatic epithelial cells within bone marrow.