Prostate cancer is one of the most common cancers in men and it is the second leading cause of cancer related death in men in the United States. Recent dietary and epidemiological studies have suggested the bene®t of dietary intake of fruits and vegetables in lowering the incidence of prostate cancer. A diet rich in fruits and vegetables provides phytochemicals, particularly indole-3-carbinol (I3C), which may be responsible for the prevention of many types of cancer, including hormonerelated cancers such as prostate. Studies to elucidate the role and the molecular mechanism(s) of action of I3C in prostate cancer, however, have not been conducted. In the current study, we investigated whether I3C had any e ect against prostate cancer cells and, if so, attempts were made to identify the potential molecular mechanism(s) by which I3C elicits its biological e ects on prostate cancer cells. Here we report for the ®rst time that I3C inhibits the growth of PC-3 prostate cancer cells. Induction of G1 cell cycle arrest was also observed in PC-3 cells treated with I3C, which may be due to the observed e ects of I3C in the up-regulation of p21 WAF1 and p27 Kip1 CDK inhibitors, followed by their association with cyclin D1 and E and down-regulation of CDK6 protein kinase levels and activity. The induction of p21 WAF1 appears to be transcriptionally upregulated and independent of the p53 responsive element. In addition, I3C inhibited the hyperpohosphorylation of the Retinoblastoma (Rb) protein in PC-3 cells. Induction of apoptosis was also observed in this cell line when treated with I3C, as measured by DNA laddering and poly (ADP-ribose) polymersae (PARP) cleavage. We also found an up-regulation of Bax, and down-regulation of Bcl-2 in I3C-treated cells. These e ects may also be mediated by the down-regulation of NF-kB observed in I3C treated PC-3 cells. From these results, we conclude that I3C inhibits the growth of PC-3 prostate cancer cells by inducing G1 cell cycle arrest leading to apoptosis, and regulates the expression of apoptosisrelated genes. These ®ndings suggest that I3C may be an e ective chemopreventive or therapeutic agent against prostate cancer. Oncogene (2001) 20, 2927 ± 2936.

These data suggest that chemoattractive mechanisms involve migration of cancer cells towards bone tissue, and that cell signaling induced by binding of the chemokine to its receptor leads to the activation of multiple signaling pathways and subsequent secretion of MMP-9 into the local environment. These findings provide a link between chemoattractive mechanisms, growth of tumor cells in bone, and tumor-enhanced bone matrix turnover.

Previously, we and others showed that broad spectrum pharmaceutical inhibition of matrix metalloproteinase (MMP) activity reduces intraosseous tumor burden and bone degradation in animal models of bone metastasis. Herein, we used specific assays to measure net enzymatic activities of individual MMPs during colonization of bone by prostate cancer cells. PC3 cells were injected into the marrow of human fetal femurs previously implanted in SCID mice. Net MMP-9 activity in bone tissues peaked 2 weeks after injection, coinciding with a wave of osteoclast recruitment. In contrast, MMP-2 and MT1-MMP activity did not change. In vitro, co-culture of PC3 cells with bone tissue led to activation of pro-MMP-9 and increases in secreted net MMP-9 activity. Activation of pro-MMP-9 was prevented by metalloprotease inhibitors but not by inhibitors of other classes of proteases. Ribozyme suppression of MMP-9 expression in PC3 cells did not affect pro-MMP-9 activation or net MMP-9 activity and did not affect the phenotype of bone tumors. siRNA targeting of MMP-9 expression in preosteoclasts in vitro demonstrated that tumorinduced preosteoclast motility was dependent on MMP-9 expression. These data suggest that osteoclastderived MMP-9 may represent a potential therapeutic target in bone metastasis and provide a rationale for the development of MMP-9-specific inhibitors. Prostate cancer is the most common cancer and second leading cause of cancer death in American males.1 The overwhelming majority of prostate cancer deaths occurs in patients with metastases, and up to 90% of prostate cancer metastases occurs at skeletal sites. 2 Patients with bone metastasis frequently suffer from pain, pathological fractures, spinal cord compression, hypercalcemia, and bone marrow suppression.3,4 Although prostate cancer metastases typically appear osteosclerotic on radiographical imaging studies, multiple lines of evidence demonstrate clearly that both bone degradation and bone formation are present within the metastatic deposits. Importantly, there is now evidence that therapies that specifically target skeletal metastases, as opposed to general metastases, may extend survival in patients with prostate cancer.

Chemokines and their receptors function in migration and homing of cells to target tissues. Recent evidence suggests that cancer cells use a chemokine receptor axis for metastasis formation at secondary sites. Previously, we showed that binding of the chemokine CXCL12 to its receptor CXCR4 mediated signaling events resulting in matrix metalloproteinase-9 expression in prostate cancer bone metastasis. A variety of methods, including lipid raft isolation, stable overexpression of CXCR4, cellular adhesion, invasion assays, and the severe combined immunodeficient -human bone tumor growth model were used. We found that (a) CXCR4 and HER2 coexist in lipid rafts of prostate cancer cells; (b) the CXCL12/CXCR4 axis results in transactivation of the HER2 receptor in lipid rafts of prostate cancer cells; (c) Src kinase mediates CXCL12/CXCR4 transactivation of HER2 in prostate cancer cells; (d) a pan-HER inhibitor desensitizes CXCR4-induced transactivation and subsequent matrix metalloproteinase-9 secretion and invasion; (e) lipid raft -disrupting agents inhibited raft-associated CXCL12/CXCR4 transactivation of the HER2 and cellular invasion; (f) overexpression of CXCR4 in prostate cancer cells leads to increased HER2 phosphorylation and migratory properties of prostate cancer cells; and (g) CXCR4 overexpression enhances bone tumor growth and osteolysis. These data suggest that lipid rafts on the cell membrane are the key site for CXCL12/CXCR4 -induced HER2 receptor transactivation. This transactivation contributes to enhanced invasive signals and metastatic growth in the bone microenvironment.

Epidemiological studies suggest an inverse association between soy intake and prostate cancer (Pca) risk. We have previously observed that soy isoflavone genistein induces apoptosis and inhibits growth of both androgen-sensitive and androgen-independent Pca cells in vitro. To determine the clinical effects of soy isoflavones on Pca we conducted a pilot study in patients with Pca who had rising serum prostate-specific antigen (PSA) levels. Patients with Pca were enrolled in the study if they had either newly diagnosed and untreated disease under watchful waiting with rising PSA (group I) or had increasing serum PSA following local therapy (group II) or while receiving hormone therapy (group III). The study intervention consisted of 100 mg of soy isoflavone (Novasoy) taken by mouth twice daily for a minimum of 3 or maximum of 6 mo. Forty-one patients were enrolled (4 in group I, 18 in group II, and 19 in group III) and had a median PSA level of 13.3 ng/ml. Thirty-nine patients could be assessed for response. Soy isoflavone supplementation was given for a median of 5.5 (range 0.8-6) mo per patient. Although there were no sustained decreases in PSA qualifying for a complete or partial response, stabilization of the PSA occurred in 83% of patients in hormone-sensitive (group II) and 35% of hormone-refractory (group III) patients. There was a decrease in the rate of the rise of serum PSA in the whole group (P = 0.01) with rates of rise decreasing from 14 to 6% in group II (P = 0.21) and from 31 to 9% in group III (P = 0.05) following the soy isoflavone intervention. Serum genistein and daidzein levels increased during supplementation from 0.11 to 0.65 microM (P = 0.00002) and from 0.11 to 0.51 microM (P = 0.00001), respectively. No significant changes were observed in serum levels of testosterone, IGF-1, IGFBP-3, or 5-OHmdU. These data suggest that soy isoflavones may benefit some patients with Pca.

Metastasis to the bone is a major clinical complication in patients with prostate cancer (PC). However, therapeutic options for treatment of PC bone metastasis are limited. Gelatinases are members of the matrix metalloproteinase (MMP) family and have been shown to play a key role in PC metastasis. Herein, we investigated the effect of SB-3CT, a covalent mechanism-based MMP inhibitor with high selectivity for gelatinases, in an experimental model of PC bone metastases. Intraperitoneal (i.p.) treatment with SB-3CT (50 mg/kg) inhibited intraosseous growth of human PC3 cells within the marrow of human fetal femur fragments previously implanted in SCID mice, as demonstrated by histomorphometry and Ki-67 immunohistochemistry. The anti-osteolytic effect of SB-3CT was confirmed by radiographic images. Treatment with SB-3CT also reduced intratumoral vascular density and bone degradation in the PC3 bone tumors. A direct inhibition of bone marrow endothelial cell invasion and tubule formation in Matrigel by SB-3CT in vitro was also demonstrated. The use of the highly selective gelatinase inhibitors holds the promise of effective intervention of metastases of PC to the bone. ' 2005 Wiley-Liss, Inc.Key words: matrix metalloproteinases; endothelium; MMP-2; MMP-9; gelatinase inhibitor PC is the second leading cause of cancer death in males in the United States. 1 Bone metastasis represents a major clinical complication of PC and is usually associated with pain, fractures and other life-impairing conditions. 2 In spite of the extent of this complication, the therapeutic options for the treatment of PC bone metastasis are very limited and are mostly palliative in nature. Therefore, new approaches to treat PC bone metastasis are urgently needed.Members of the matrix metalloproteinase (MMP) family of zincdependent endopeptidases, in particular gelatinases A and B, also known as MMP-2 and MMP-9, have been associated with the development of bone metastasis by PC cells. 3-8 Therefore, MMPs constitute an attractive target for intervention in PC bone metastasis. A limited number of preclinical studies reported the ability of synthetic MMP inhibitors to inhibit primary and metastatic PC growth in animal models. 9-11 We previously reported that administration of the broad-spectrum MMP inhibitor batimastat (BB-94) reduced tumor burden and bone degradation by human PC3 cells growing within human bone in severe combined immunodeficiency (SCID) mice. 8 These studies demonstrated the potential benefit of targeting MMP activity in PC bone metastasis. In spite of the success of broad-spectrum MMP inhibitors in preclinical studies, these inhibitors failed to demonstrate therapeutic efficacy in clinical trials in patients with advanced cancer, and also produced undesired side effects. [12][13][14] Lack of selectivity has been considered one of the main reasons for the disappointing performance of broad-spectrum MMP inhibitors in clinical trials. 12,14 Thus, targeting of specific and relevant MMPs in cancer progression remains an important goal.A...

IntroductionThe chemokine CXCL12, also known as SDF-1, and its receptor, CXCR4, are overexpressed in prostate cancers and in animal models of prostate-specific PTEN deletion, but their regulation is poorly understood. Loss of the tumor suppressor PTEN (phosphatase and tensin homolog) is frequently observed in cancer, resulting in the deregulation of cell survival, growth, and proliferation. We hypothesize that loss of PTEN and subsequent activation of Akt, frequent occurrences in prostate cancer, regulate the CXCL12/CXCR4 signaling axis in tumor growth and bone metastasis.MethodsMurine prostate epithelial cells from PTEN+/+, PTEN+/−, and PTEN−/− (prostate specific knockdown) mice as well as human prostate cancer cell lines C4-2B, PC3, and DU145 were used in gene expression and invasion studies with Akt inhibition. Additionally, HA-tagged Akt1 was overexpressed in DU145, and tumor growth in subcutaneous and intra-tibia bone metastasis models were analyzed.ResultsLoss of PTEN resulted in increased expression of CXCR4 and CXCL12 and Akt inhibition reversed expression and cellular invasion. These results suggest that loss of PTEN may play a key role in the regulation of this chemokine activity in prostate cancer. Overexpression of Akt1 in DU145 resulted in increased CXCR4 expression, as well as increased proliferation and cell cycle progression. Subcutaneous injection of these cells also resulted in increased tumor growth as compared to neo controls. Akt1 overexpression reversed the osteosclerotic phenotype associated with DU145 cells to an osteolytic phenotype and enhanced intra-osseous tumor growth.ConclusionsThese results suggest the basis for activation of CXCL12 signaling through CXCR4 in prostate cancer driven by the loss of PTEN and subsequent activation of Akt. Akt1-associated CXCL12/CXCR4 signaling promotes tumor growth, suggesting that Akt inhibitors may potentially be employed as anticancer agents to target expansion of PC bone metastases.

TMPRSS2-ERG fusion transcripts have been shown to be expressed in a majority of prostate cancer (PC) patients because of chromosomal translocations or deletions involving the TMPRSS2 gene promoter and the ERG gene coding sequence. These alterations cause androgen-dependent ERG transcription factor expression in PC patients. We and others have shown that chemokine receptor CXCR4 expression is upregulated in PC tumor cells, and its ligand, CXCL12, is expressed in bone stromal cells. The CXCL12/CXCR4 axis functions in PC progression to enhance invasion and metastasis. To address the regulation of CXCR4 expression, we identified several putative ERG consensus-binding sites in the promoter region of CXCR4. We hypothesized that androgen-dependent regulation of the ERG transcription factor could induce CXCR4 expression in PC cells. Results of the current study show that 1) prostate tumor cells coexpress higher ERG and CXCR4 compared with benign tissue, 2) CXCR4 expression is increased in the TMPRSS2-ERG fusion-positive cell line, 3) ERG transcription factor binds to the CXCR4 gene promoter, 4) synthetic androgen (R1881) upregulates both ERG and CXCR4 in TMPRSS2-ERG fusion-positive VCaP cells, 5) small interfering RNA-mediated down-regulation of ERG resulted in the loss of androgen-dependent regulation of CXCR4 expression in VCaP cells, and 6) R1881-activated TMPRSS2-ERG expression functionally activates CXCR4 in VCaP cells. These findings provide a link between TMPRSS2-ERG translocations and enhanced metastasis of tumor cells through CXCR4 function in PC cells.