Molecular markers and determinants of prostate cancer metastasis

DNA methylation markers for risk of metastasis in a cohort of men with localized prostate cancer

Accurately identifying life-threatening prostate cancer (PCa) at time of diagnosis remains an unsolved problem. We evaluated whether DNA methylation status of selected candidate genes can predict the risk of metastasis beyond clinical risk factors in men with untreated PCa. A nested case-control study was conducted among men diagnosed with localized PCa at Kaiser Permanente California between 01/01/1997-12/31/2006 who did not receive curative treatments. Cases were those who developed metastasis within 10 years from diagnosis. Controls were selected using density sampling. Ninety-eight candidate genes were selected from functional categories of cell cycle control, metastasis/tumour suppressors, cell signalling, cell adhesion/motility/invasion, angiogenesis, and immune function, and 41 from pluripotency genes. Cancer DNA from diagnostic biopsy blocks were extracted and analysed. Associations of methylation status were assessed using CpG site level and principal components-based analysis in conditional logistic regressions. In 215 cases and 404 controls, 27 candidate genes were found to be statistically significant in at least one of the two analytical approaches. The agreement between the methods was 25.9% (7 candidate genes, including 2 pluripotency markers). The DNA methylation status of several candidate genes was significantly associated with risk of metastasis in untreated localized PCa patients. These findings may inform future risk prediction models for PCa metastasis beyond clinical characteristics.

Rutaecarpine administration inhibits cancer cell growth in allogenic TRAMP-C1 prostate cancer mice correlating with immune balance in vivo

BACKGROUND

Rutaecarpine (Rut) is a plant alkaloid abundant in Euodia ruticarpa which is a Chinese herbal medicine used for treating various cancers. However, the Rut administration effect on prostate cancer in vivo remains unclear.

AIM

In the present study we established an allogenic TRAMP-C1 prostate cancer mouse model to evaluate the Rut administration effect and mechanism in vivo.

METHODS

To unravel the Rut administration effect on prostate cancer in vivo, C57BL/6J male mice (8 weeks old) were randomly grouped (n = 9), subcutaneously loaded with TRAMP-C1 prostate cancer cells and immediately given daily by gavage with Rut dissolved in soybean oil at 7 mg (low dose), 35 mg (medium dose), and 70 mg/kg b.w./day (high dose) for successive 39 days.

RESULTS

Rut administration significantly and dose-dependently reduced both tumor volume and solid prostate cancer weight in allogenic TRAMP-C1 male mice. Rut administration markedly increased (TNF-α+IFN-γ) (Th1-)/IL-10 (Th2-) cytokine secretion ratios by splenocytes and TNF-α (M1-)/IL-10 (M2-) cytokine secretion ratios by macrophages as compared to those of dietary control group, suggesting that Rut administration in vivo regulates the immune balance toward Th1- and M1-polarized characteristics. Decreased CD19⁺, CD4⁺ and CD8⁺ lymphocytes in the peripheral blood of allogenic TRAMP-C1 mice were significantly elevated by Rut administration. Tumor weights positively correlated with TNF-α secretions by splenocytes, suggesting that there is a tumor cachexia in the tumor-bearing mice. Tumor weights negatively correlated with IgG (Th1-antibody) levels in the sera, suggesting that Th1-polarized immune balance may inhibit prostate cancer cell growth.

CONCLUSIONS

Our results evidenced that Rut administration suppresses prostate cancer cell growth in mice subcutaneously loaded with TRAMP-C1 cells and correlated the anti-cancer effects with Th1-polarized immune balance in vivo.

Moving Beyond Gleason Scoring

Context.—

The combination of grading and staging is the basis of current standard of care for prediction for most cancers. D. F. Gleason created the current prostate cancer (PCa) grading system. This system has been modified several times. Molecular data have been added. Currently, all grading systems are cancer-cell based.

Objective.—

To review the literature available on host response measures as reactive stroma grading and stromogenic carcinoma, and their predictive ability for PCa biochemical recurrence and PCa-specific death.

Data Sources.—

Our own experience has shown that reactive stroma grading and the subsequently binarized system (stromogenic carcinoma) can independently predict biochemical recurrence and/or PCa-specific death, particularly in patients with a Gleason score of 6 or 7. Stromogenic carcinoma has been validated by 4 other independent groups in at least 3 continents.

Conclusions.—

Broders grading and Dukes staging have been combined to form the most powerful prognostic tools in standard of care. The time has come for us to incorporate measures of host response (stromogenic carcinoma) into the arsenal of elements we use to predict cancer survival, without abandoning what we know works. These data also suggest that our current definition of PCa might need some revision.

The oncogenic transcription factor ERG represses the transcription of the tumour suppressor gene PTEN in prostate cancer cells

The oncogene ETS-related gene (ERG) encodes a transcription factor with roles in the regulation of haematopoiesis, angiogenesis, vasculogenesis, inflammation, migration and invasion. The ERG oncogene is activated in >50% of prostate cancer cases, generally through a gene fusion with the androgen-responsive promoter of transmembrane protease serine 2. Phosphatase and tensin homologue (PTEN) is an important tumour suppressor gene that is often inactivated in cancer. ERG overexpression combined with PTEN inactivation or loss is often associated with aggressive prostate cancer. The present study aimed to determine whether or not ERG regulates PTEN transcription directly. ERG was demonstrated to bind to the PTEN promoter and repress its transcription. ERG overexpression reduced endogenous PTEN expression, whereas ERG knockdown increased PTEN expression. The ability of ERG to repress PTEN may contribute to a more cancer-permissive environment.

Enhanced prostate cancer gene transfer and therapy using a novel serotype chimera cancer terminator virus (Ad.5/3-CTV)

Few options are available for treating patients with advanced prostate cancer (PC). As PC is a slow growing disease and accessible by ultrasound, gene therapy could provide a viable option for this neoplasm. Conditionally replication-competent adenoviruses (CRCAs) represent potentially useful reagents for treating PC. We previously constructed a CRCA, cancer terminator virus (CTV), which showed efficacy both in vitro and in vivo for PC. The CTV was generated on a serotype 5-background (Ad.5-CTV) with infectivity depending on Coxsackie-Adenovirus Receptors (CARs). CARs are frequently reduced in many tumor types, including PCs thereby limiting effective Ad-mediated therapy. Using serotype chimerism, a novel CTV (Ad.5/3-CTV) was created by replacing the Ad.5 fiber knob with the Ad.3 fiber knob thereby facilitating infection in a CAR-independent manner. We evaluated Ad.5/3-CTV in comparison with Ad.5-CTV in low CAR human PC cells, demonstrating higher efficiency in inhibiting cell viability in vitro. Moreover, Ad.5/3-CTV potently suppressed in vivo tumor growth in a nude mouse xenograft model and in a spontaneously induced PC that develops in Hi-myc transgenic mice. Considering the significant responses in a Phase I clinical trial of a non-replicating Ad.5-mda-7 in advanced cancers, Ad.5/3-CTV may exert improved therapeutic benefit in a clinical setting.

Suppression of SCARA5 by Snail1 is essential for EMT-associated cell migration of A549 cells

Accumulating evidence indicates that epithelial-to-mesenchymal transition (EMT) might be a key event for cancer progression. The upregulation of Snail1, one of the most extensively studied EMT regulators, has been implicated in cancer metastasis, but the underlying mechanisms remain unclear. This study aims to identify that Snail1 targets regulating EMT-associated cancer cell migration. Human lung carcinoma A549 cells were treated with transforming growth factor beta 1 (TGF-β1), and EMT-associated phenotypic and functional alterations were monitored. TGF-β1 induced typical EMT-like morphological changes, ‘cadherin switching' and cell migration in A549 cells. TGF-β1 stimulation induced rapid and persistent upregulation of Snail1. Moreover, Snail1 upregulation was required for EMT-associated cell migration. Several metastasis suppressors with putative Snail1-binding sites in their promoters were dramatically repressed in A549 cells during TGF-β1-induced EMT. Gain- and loss-of Snail1 function experiments demonstrated that scavenger receptor class A member 5 (SCARA5) was negatively regulated by Snail1. Importantly, SCARA5 downregulation was essential for EMT-induced migration in A549 cells. The chromatin immunoprecipitation assay revealed that Snail1 could bind to the E-box elements in SCARA5 promoter, implying that SCARA5 is a direct Snail1 target modulating cancer cell mobility during EMT. In addition, we showed that DNA methyltransferase 1 was physically associated with Snail1 to silence SCARA5 expression with an unidentified DNA methylation-independent mechanism, suggesting the complexity of Snail1-mediated epigenetic regulation. Collectively, our data demonstrated that EMT-regulator Snail1 suppresses the expression of SCARA5 to promote cancer progression, highlighting the possibility to target Snail1 and SCARA5 for cancer treatment.

Loss of receptor protein tyrosine phosphatase β/ζ (RPTPβ/ζ) promotes prostate cancer metastasis

BACKGROUND

The role of pleiotrophin and its receptors RPTPβ/ζ and Syndecan-3 during tumor metastasis remains unknown.

RESULTS

RPTPβ/ζ knockdown initiates EMT, promotes pleiotrophin-mediated migration and attachment through Syndecan-3 and induces in vivo metastasis.

CONCLUSION

RPTPβ/ζ plays a suppressor-like role in prostate cancer metastasis.

SIGNIFICANCE

Boosting RPTPβ/ζ or attenuating Syndecan-3 signaling pathways may lead to more effective therapeutic strategies in treating prostate cancer metastasis. Pleiotrophin is a growth factor that induces carcinogenesis. Despite the fact that many published reports focused on the role of pleiotrophin and its receptors, receptor protein tyrosine phosphatase (RPTPβ/ζ), and syndecan-3 during tumor development, no information is available regarding their function in tumor metastasis. To investigate the mechanism through which pleiotrophin regulates tumor metastasis, we used two different prostate carcinoma cell lines, DU145 and PC3, in which the expression of RPTPβ/ζ or syndecan-3 was down-regulated by the RNAi technology. The loss of RPTPβ/ζ expression initiated epithelial-to-mesenchymal transition (EMT) and increased the ability of the cells to migrate and invade. Importantly, the loss of RPTPβ/ζ expression increased metastasis in nude mice in an experimental metastasis assay. We also demonstrate that RPTPβ/ζ counterbalanced the pleiotrophin-mediated syndecan-3 pathway. While the inhibition of syndecan-3 expression inhibited the pleiotrophin-mediated cell migration and attachment through the Src and Fak pathway, the inhibition of RPTPβ/ζ expression increased pleiotrophin-mediated migration and attachment through an interaction with Src and the subsequent activation of a signal transduction pathway involving Fak, Pten, and Erk1/2. Taken together, these results suggest that the loss of RPTPβ/ζ may contribute to the metastasis of prostate cancer cells by inducing EMT and promoting pleiotrophin activity through the syndecan-3 pathway.

Cell lineage analysis of the mammalian female germline

Fundamental aspects of embryonic and post-natal development, including maintenance of the mammalian female germline, are largely unknown. Here we employ a retrospective, phylogenetic-based method for reconstructing cell lineage trees utilizing somatic mutations accumulated in microsatellites, to study female germline dynamics in mice. Reconstructed cell lineage trees can be used to estimate lineage relationships between different cell types, as well as cell depth (number of cell divisions since the zygote). We show that, in the reconstructed mouse cell lineage trees, oocytes form clusters that are separate from hematopoietic and mesenchymal stem cells, both in young and old mice, indicating that these populations belong to distinct lineages. Furthermore, while cumulus cells sampled from different ovarian follicles are distinctly clustered on the reconstructed trees, oocytes from the left and right ovaries are not, suggesting a mixing of their progenitor pools. We also observed an increase in oocyte depth with mouse age, which can be explained either by depth-guided selection of oocytes for ovulation or by post-natal renewal. Overall, our study sheds light on substantial novel aspects of female germline preservation and development.

Many aspects of mammalian female germline development during embryogenesis and throughout adulthood are either unknown or under debate. In this study we applied a novel method for the reconstruction of cell lineage trees utilizing microsatellite mutations, accumulated during mouse life, in oocytes and other cells, sampled from young and old mice. Analysis of the reconstructed cell lineage trees shows that oocytes are clustered separately from bone-marrow derived cells, that oocytes from different ovaries share common progenitors, and that oocyte depth (number of cell divisions since the zygote) increases significantly with mouse age.

Resistance to paclitaxel increases the sensitivity to other microenvironmental stresses in prostate cancer cells

The microenvironment is central to many aspects of cancer pathobiology and has been proposed to play a role in the development of cancer cell resistance to therapy. To examine the response to microenvironmental conditions, two paclitaxel resistant prostate cancer (PCa) cell lines (stable and reversible) and one reversible heat resistant cell line were studied. In comparison to their parental cell lines, both paclitaxel resistant cell lines (stable and reversible) were more sensitive to microenvironmental heat, potentially yielding a synergistic therapeutic opportunity. In the two phenotypic cells repopulated after acute heat or paclitaxel treatments, there was an inverse correlation between paclitaxel and heat resistance: resistance to paclitaxel imparted sensitivity to heat; resistance to heat imparted sensitivity to paclitaxel. These studies indicate that as cancer cells evolve resistance to single microenvironmental stress they may be more sensitive to others, perhaps allowing us to design new approaches for PCa therapy.

Survivin is a potential mediator of prostate cancer metastasis

PURPOSE

We examined whether Survivin expression is associated with an increased risk of metastasis in prostate cancer.

METHODS AND MATERIALS

A total of 205 patients with T1 (23%) and T2 (77%) prostate cancer were treated with conventional external beam radiation therapy from 1991 to 1993 at the Massachusetts General Hospital. Of the patients, 62 had adequate and suitable-stained tumor material for Survivin analysis. Median follow-up was 102 months (range, 5-127 months). Distant failure was determined on the basis of clinical criteria. In preclinical studies, replication-deficient adenovirus encoding phosphorylation-defective Survivin Thr34→Ala dominant-negative mutant pAd-S(T34A) or short hairpin RNA (shRNA) was used to inhibit Survivin in prostate cancer models, and the cell motility, morphology, and metastasis were investigated.

RESULTS

Our correlative data on men with early-stage (T1/T2) prostate cancers treated at Massachusetts General Hospital by definitive radiotherapy indicated that overexpression of Survivin (positive staining in ≥10% cells) was associated with a significantly increased risk for the subsequent development of distant metastasis (p = 0.016) in the univariate analysis. In the multivariate analysis, overexpression of Survivin remained an independent predictor of distant metastasis (p = 0.008). The inhibition of Survivin dramatically inhibited invasiveness of prostate cancer cells in the in vitro invasion assay and spontaneous metastasis in the Dunning prostate cancer in vivo model. Furthermore, attenuation of Survivin resulted in changes in the microtubule cytoskeleton, loss of cellular polarity, and loss of motility.

CONCLUSIONS

This study suggests that Survivin may be a potentially important prognostic marker and promising therapeutic target in metastatic prostate cancer.

Enhanced delivery of mda-7/IL-24 using a serotype chimeric adenovirus (Ad.5/3) improves therapeutic efficacy in low CAR prostate cancer cells

Gene therapy is being examined as a potential strategy for treating prostate cancer. Serotype 5 adenovirus (Ad.5) is routinely used as a vector for transgene delivery. However, the infectivity of Ad.5 is dependent on Coxsackie-adenovirus receptors (CARs); many tumor types show a reduction in this receptor in vivo, thereby limiting therapeutic gene transduction. Serotype chimerism is one approach to circumvent CAR deficiency; this strategy is used to generate an Ad.5/3-recombinant Ad that infects cancer cells through Ad.3 receptors in a CAR-independent manner. In this report, the enhanced transgene delivery and efficacy of Ad.5/3-recombinant virus was evaluated using an effective wide-spectrum anticancer therapeutic melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24). Our data show that in low CAR human prostate cancer cells (PC-3), a recombinant Ad.5/3 virus delivering mda-7/IL-24 (Ad.5/3-mda-7) is more efficacious than an Ad.5 virus encoding mda-7/IL-24 (Ad.5-mda-7) in infecting tumor cells, expressing MDA-7/IL-24 protein, inducing cancer-specific apoptosis, inhibiting in vivo tumor growth and exerting an antitumor 'bystander' effect in a nude mouse xenograft model. Considering the fact that Ad.5-mda-7 has shown significant objective responses in a phase I clinical trial for solid tumors, Ad.5/3-mda-7 is predicted to exert enhanced therapeutic benefit in patients with prostate cancer.

CTEN/tensin 4 expression induces sensitivity to paclitaxel in prostate cancer

BACKGROUND

Recently, we established paclitaxel-resistant prostate cancer cell lines (PC-3-TxR and DU145-TxR). To determine the mechanisms of paclitaxel resistance in PC-3-TxR cells, we compared the gene expression profiles between PC-3 and PC-3-TxR cells. Our results indicated that expression of the C-terminal tensin like protein (CTEN, tensin 4) gene was down-regulated by 10-fold in PC-3-TxR cells. We investigated the possibility that CTEN overexpression restores paclitaxel sensitivity.

METHODS

We investigated how knockdown and overexpression of CTEN in androgen-independent cell lines affect paclitaxel sensitivity by colony formation assay and growth inhibition assay. To determine the mechanisms by which CTEN affects paclitaxel sensitivity, we investigated the relationships between CTEN and F-actin or epidermal growth factor receptor (EGFR) in PC-3 cells. We also examined the association between expression of CTEN and grade of prostate cancer by immunohistochemistry using tissue microarray analysis.

RESULTS

Down-regulation of CTEN, which is located in the cytoskeleton, played an important role in paclitaxel resistance in PC-3-TxR cells. Knockdown of CTEN expression in PC-3 cells induced paclitaxel resistance. Overexpression of CTEN in PC-3-TxR and DU145-TxR cells restored paclitaxel sensitivity. CTEN expression was inversely correlated with F-actin and EGFR expression. Then knockdown of actin and EGFR in PC-3-TxR cells recovered paclitaxel sensitivity, indicating that CTEN down-regulation mediates paclitaxel resistance through elevation of EGFR and actin expression. Moreover, CTEN expression was inversely correlated with Gleason score.

CONCLUSIONS

These results strongly suggested that CTEN plays an important role in paclitaxel sensitivity and that CTEN expression level may be a prognostic predictive factor for PCa patients.

A novel role of Shc adaptor proteins in steroid hormone-regulated cancers

Tyrosine phosphorylation plays a critical role in growth regulation, and its aberrant regulation can be involved in carcinogenesis. The association of Shc (Src homolog and collagen homolog) adaptor protein family members in tyrosine phosphorylation signaling pathway is well recognized. Shc adaptor proteins transmit activated tyrosine phosphorylation signaling that suggest their plausible role in growth regulation including carcinogenesis and metastasis. In parallel, by sharing a similar mechanism of carcinogenesis, the steroids are involved in the early stage of carcinogenesis as well as the regulation of cancer progression and metastatic processes. Recent evidence indicates a cross-talk between tyrosine phosphorylation signaling and steroid hormone action in epithelial cells, including prostate and breast cancer cells. Therefore, the members of Shc proteins may function as mediators between tyrosine phosphorylation and steroid signaling in steroid-regulated cell proliferation and carcinogenesis. In this communication, we discuss the novel roles of Shc proteins, specifically p52(Shc) and p66(Shc), in steroid hormone-regulated cancers and a novel molecular mechanism by which redox signaling induced by p66(Shc) mediates steroid action via a non-genomic pathway. The p66(Shc) protein may serve as an effective biomarker for predicting cancer prognosis as well as a useful target for treatment.

Coculture with prostate cancer cells alters endoglin expression and attenuates transforming growth factor-beta signaling in reactive bone marrow stromal cells

A dynamic interplay between prostate cancer cells and reactive bone stroma modulates growth of metastases within bone. We used microarray analysis to screen for changes in gene expression in bone marrow stromal cells cocultured with prostate cancer cells and found reduced expression of endoglin, a transmembrane glycoprotein that functions as an auxiliary coreceptor for members of the transforming growth factor beta (TGF-beta) family of cytokines. The downstream TGF-beta/bone morphogenetic protein signaling pathway including Smad1 and Smad2/3 also was attenuated, as was Smad-dependent gene transcription. Smad1/5/8-dependent inhibitor of DNA binding 1 expression and Smad2/3-dependent plasminogen activator inhibitor I expression both were decreased and were accompanied by decreased cell proliferation. Small interfering RNA-mediated knockdown of endoglin in HS-5 cells verified that the effects on signaling were a direct result of the attenuation of endoglin. These data illustrate that endoglin acts as a positive regulator of both activin receptor-like kinase 1-induced Smad1/5/8 activation and activin receptor-like kinase 5-induced Smad2/3 activation in bone marrow stromal cells. In addition, the data illustrate that one early event of metastasis upon the arrival of prostate cancer cells into the bone stroma is attenuated endoglin expression in the stromal cells, which subsequently alters Smad signaling and cell proliferation. We hypothesize that coculture of bone marrow stromal cells with prostate cancer cells alters TGF-beta signaling in the stromal cells, ultimately facilitating growth of the cancer cells in the bone compartment. Collectively, these studies suggest that prostate cancer cells modulate TGF-beta responsiveness of bone marrow stroma as one means of facilitating their own growth in bone.

Eradication of therapy-resistant human prostate tumors using a cancer terminator virus

Terminal prostate cancer is refractory to conventional anticancer treatments because of frequent overexpression of antiapoptotic proteins Bcl-2 and/or Bcl-x(L). Adenovirus-mediated delivery of melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), a secreted cytokine having cancer-selective apoptosis-inducing properties, profoundly inhibits prostate cancer cell growth. However, forced overexpression of Bcl-2 or Bcl-x(L) renders prostate cancer cells resistant to Ad.mda-7. We constructed a conditionally replication-competent adenovirus in which expression of the adenoviral E1A gene, necessary for replication, is driven by the cancer-specific promoter of progression elevated gene-3 (PEG-3) and which simultaneously expresses mda-7/IL-24 in the E3 region of the adenovirus (Ad.PEG-E1A-mda-7), a cancer terminator virus (CTV). This CTV generates large quantities of MDA-7/IL-24 as a function of adenovirus replication uniquely in cancer cells. Infection of Ad.PEG-E1A-mda-7 (CTV) in normal prostate epithelial cells and parental and Bcl-2- or Bcl-x(L)-overexpressing prostate cancer cells confirmed cancer cell-selective adenoviral replication, mda-7/IL-24 expression, growth inhibition, and apoptosis induction. Injecting Ad.PEG-E1A-mda-7 (CTV) into xenografts derived from DU-145-Bcl-x(L) cells in athymic nude mice completely eradicated not only primary tumors but also distant tumors (established in the opposite flank), thereby implementing a cure. These provocative findings advocate potential therapeutic applications of this novel virus for advanced prostate cancer patients with metastatic disease.

Genistein induces the metastasis suppressor kangai-1 which mediates its anti-invasive effects in TRAMP cancer cells

Previous studies demonstrated a direct correlation with loss of kangai-1 (KAI1), a metastasis suppressor, and poor prognosis in human prostate and other cancers. In this study, we have characterized the age-dependent downregulation of KAI1 in the TRAMP model which was reversed when mice were fed a genistein-enriched diet. We demonstrated here that doses of genistein (5 and 10 microM)--achievable by supplement intake--significantly induced the expression of KAI1, both at the mRNA and protein levels (up to 2.5-fold), and decreased the invasiveness of TRAMP-C2 cells >2.0-fold. We have pinpointed KAI1 as the invasion suppressor, since its knockdown by siRNA restored the invasive potential of genistein-treated TRAMP-C2 cells to control levels. This work provides the first evidence that genistein treatment may counteract KAI1 downregulation, which is observed in many cancer types and therefore, could be used in anti-metastatic therapies.

Surface-epitope masking (SEM): an immunological subtraction approach for developing monoclonal antibodies targeting surface-expressed molecules

An immunological subtraction approach, surface-epitope masking (SEM), is described that permits the efficient and selective production of monoclonal antibodies (MAbs) reacting with both known and unknown molecules expressed on the cell surface. The tenet underlying SEM involves blocking (masking) of shared antigens between two target populations, a "driver" and a "tester," and using appropriately modified surface-masked "tester" cells to generate MAbs reacting with surface antigens unique to the "tester population" that differentiate the two antigen sources. SEM has been employed to develop MAbs that react with the multidrug resistance surface-expressed P-glycoprotein (MDR-1) and the human interferon-gamma receptor and two potentially novel tumor-associated antigens (TAAs) expressed on the surface of prostate carcinoma and breast carcinoma cells. In principle, the SEM approach provides an uncomplicated and effective means of developing MAbs, which can also be used to identify genes, associated with important cellular processes involved in normal physiology, such as growth, aging, differentiation, and development. In addition, this strategy is amenable to produce MAbs and identify genes associated with specific disease states, including cancer, neurodegeneration, autoimmunity, and infection with pathogenic agents.

Cyclin-dependent kinase 5 activity controls cell motility and metastatic potential of prostate cancer cells

We show here that cyclin-dependent kinase 5 (CDK5), a known regulator of migration in neuronal development, plays an important role in prostate cancer motility and metastasis. P35, an activator of CDK5 that is indicative of its activity, is expressed in a panel of human and rat prostate cancer cell lines, and is also expressed in 87.5% of the human metastatic prostate cancers we examined. Blocking of CDK5 activity with a dominant-negative CDK5 construct, small interfering RNA, or roscovitine resulted in changes in the microtubule cytoskeleton, loss of cellular polarity, and loss of motility. Expression of a dominant-negative CDK5 in the highly metastatic Dunning AT6.3 prostate cancer cell line also greatly impaired invasive capacity. CDK5 activity was important for spontaneous metastasis in vivo; xenografts of AT6.3 cells expressing dominant-negative CDK5 had less than one-fourth the number of lung metastases exhibited by AT6.3 cells expressing the empty vector. These results show that CDK5 activity controls cell motility and metastatic potential in prostate cancer.

Tissue inhibitor of metalloproteinase-3 induces apoptosis in prostate cancer cells and confers increased sensitivity to paclitaxel

Prostate cancer is the most common cancer and the second leading cause of cancer-related death in American men. To investigate the possible usefulness of tissue inhibitor of metalloproteinase-3 (TIMP-3) in prostate cancer gene therapy, we used an adenovirus expressing TIMP-3 to assess its role as an apoptosis trigger in highly metastatic prostate cancer cell lines PC-3 and DU-145. We showed that TIMP-3 alone induced apoptotic cell death which was triggered by mitochondrion-mediated caspase-3 activation. In combination treatment, we found that adenovirus-mediated expression of TIMP-3 greatly sensitised prostate cancer cells to chemotherapeutic drug paclitaxel, indicating a superadditive or synergistic effect of TIMP-3 and cytostatic treatment on prostate cancer cell death. The proper combination of adenovirus-mediated expression of TIMP-3 with conventional chemotherapeutic drug(s) could have potential benefits in treating highly metastatic prostate cancer.

Ionizing radiation enhances therapeutic activity of mda-7/IL-24: overcoming radiation- and mda-7/IL-24-resistance in prostate cancer cells overexpressing the antiapoptotic proteins bcl-xL or bcl-2

Subtraction hybridization applied to terminally differentiating human melanoma cells identified mda-7/IL-24, a cytokine belonging to the IL-10 gene superfamily. Adenoviral-mediated delivery of mda-7/IL-24 (Ad.mda-7) provokes apoptosis selectively in a wide spectrum of cancers in vitro in cell culture, in vivo in human tumor xenograft animal models and in patients with advanced carcinomas and melanomas. In human prostate cancer cells, a role for mitochondrial dysfunction and induction of reactive oxygen species in the apoptotic process has been established. Ectopic overexpression of bcl-xL and bcl-2 prevents these changes including apoptosis induction in prostate tumor cells by Ad.mda-7. We now document that this resistance to apoptosis can be reversed by treating bcl-2 family overexpressing prostate tumor cells with ionizing radiation in combination with Ad.mda-7 or purified GST-MDA-7 protein. Additionally, radiation augments apoptosis induction by mda-7/IL-24 in parental and neomycin-resistant prostate tumor cells. Radiosensitization to mda-7/IL-24 is dependent on JNK signaling, as treatment with the JNK 1/2/3 inhibitor SP600125 abolishes this effect. Considering that elevated expression of bcl-xL and bcl-2 are frequent events in prostate cancer development and progression, the present studies support the use of ionizing radiation in combination with mda-7/IL-24 as a means of augmenting the therapeutic benefit of this gene in prostate cancer, particularly in the context of tumors displaying resistance to radiation therapy owing to bcl-2 family member overexpression.

The membrane-anchored serine protease, TMPRSS2, activates PAR-2 in prostate cancer cells

TMPRSS2 is a type II transmembrane-bound serine protease that has gained interest owing to its highly localized expression in the prostate and its overexpression in neoplastic prostate epithelium. Once activated, the serine protease domain of TMPRSS2 is released from the cell surface into the extracellular space. PAR (protease-activated receptor)-2 belongs to a family of G-protein-coupled receptors (PAR-1-4) that are activated by specific serine proteases, which are expressed in many normal and malignant cell types. Previous in vitro studies on prostate cancer cells suggest a role for PAR-2 in prostate cancer metastasis. A polyclonal anti-human TMPRSS2 antibody was generated against the TMPRSS2 serine protease domain. The antibody showed specific reactivity with recombinant expressed TMPRSS2, and so was used to extract and purify the cleaved active TMPRSS2 protease from prostate cancer cells. Reverse transcriptase PCR and Western blot analysis were used to show the expression of both TMPRSS2 and PAR-2 in the androgen-dependent LNCaP prostate cancer cell line. Treatment of LNCaP cells with the cellular immunopurified TMPRSS2 protease induced a transient increase in intracellular calcium, which is indicative of G-protein-coupled-receptor activation. This calcium mobilization was inhibited by cellular pre-treatment with a specific PAR-2 antagonist, but not with a PAR-1 antagonist; inhibition of the protease activity also failed to mobilize calcium, suggesting that TMPRSS2 is capable of cleaving and thereby activating the PAR-2 receptor. The calcium mobilization was also inhibited by cellular pre-treatment with suramin or 2-APB (2-aminoethoxydiphenyl borate), indicating that a G-protein pathway is involved and that subsequent calcium release is mainly from intracellular stores. The present study describes how TMPRSS2 may contribute to prostate tumour metastasis via the activation of PAR-2.

Regulation of gene expression and inhibition of experimental prostate cancer bone metastasis by dietary genistein

Prostate cancer frequently metastasizes to the bone, and the treatment outcome for metastatic prostate cancer has been disappointing so far. Dietary genistein, derived primarily from soy product, has been proposed to be partly responsible for the low rate of prostate cancer in Asians. Our previous studies have shown that genistein elicits pleiotropic effects on prostate cancer cells, but there are no studies documenting comprehensive gene expression profiles and antitumor effects of dietary genistein on human prostate cancer grown in human bone environment. In this study, we investigated the effects of genistein on PC3 prostate cancer cells and experimental PC3 bone tumors created by injecting PC3 cells into human bone fragments previously implanted in severe combined immunodeficient (SCID) mice (SCID human model). We found that genistein significantly inhibited PC3 bone tumor growth using both prevention and intervention strategies. By using microarray and real-time polymerase chain reaction technology, we found that genistein regulated the expression of multiple genes involved in the control of cell growth, apoptosis, and metastasis both in vitro and in vivo. For example, the expression of various metalloproteinases (MMPs) in PC3 bone tumors was inhibited by genistein treatment, whereas osteoprotegerin was upregulated. MMP immunostaining and transfection experiments also demonstrated that MMP-9 expression was inhibited in PC3 cells in vitro and PC3 bone tumors in vivo after genistein treatment. These results, particularly the in vivo results, demonstrate that dietary genistein may inhibit prostate cancer bone metastasis by regulating metastasis-related genes. Genistein may thus be a promising agent for the prevention and/or treatment of prostate cancer.

Gene expression profiling revealed novel mechanism of action of Taxotere and Furtulon in prostate cancer cells

Background

Both Taxotere and Capecitabine have shown anti-cancer activity against various cancers including prostate cancer. In combination, Taxotere plus Capecitabine has demonstrated higher anti-cancer activity in advanced breast cancers. However, the molecular mechanisms of action of Taxotere and Capecitabine have not been fully elucidated in prostate cancer.

Methods

The total RNA from PC3 and LNCaP prostate cells untreated and treated with 2 nM Taxotere, 110 μM Furtulon (active metabolite of Capecitabine), or 1 nM Taxotere plus 50 μM Furtulon for 6, 36, and 72 hours, was subjected to Affymetrix Human Genome U133A Array analysis. Real-time PCR and Western Blot analysis were conducted to confirm microarray data.

Results

Taxotere and Furtulon down-regulated some genes critical for cell proliferation, cell cycle progression, transcription factor, cell signaling, and oncogenesis, and up-regulated some genes related to the induction of apoptosis, cell cycle arrest, and differentiation in both cell lines. Taxotere and Furtulon also up-regulated some genes responsible for chemotherapeutic resistance, suggesting the induction of cancer cell resistance to these agents.

Conclusions

Taxotere and Furtulon caused the alternation of a large number of genes, many of which may contribute to the molecular mechanisms by which Taxotere and Furtulon inhibit the growth of prostate cancer cells. This information could be utilized for further mechanistic research and for devising optimized therapeutic strategies against prostate cancer.

Regulation of microtubule, apoptosis, and cell cycle-related genes by taxotere in prostate cancer cells analyzed by microarray

Taxotere showed antitumor activity against solid tumors including prostate cancer. However, the molecular mechanism(s) of action of Taxotere has not been fully elucidated. In order to establish such molecular mechanism(s) in both hormone-insensitive (PC3) and hormone-sensitive (LNCaP) prostate cancer cells, comprehensive gene expression profiles were obtained by Affymetrix Human Genome U133A Array. The RNA from the cells treated with 2 nM Taxotere was subjected to microarray analysis. We found that a total of 166, 365, and 1785 genes showed greater than two-fold change in PC3 cells after 6, 36, and 72 hours of treatment, respectively compared to 57, 823, and 964 genes in LNCaP cells. The expression of tubulin was decreased, whereas the expression of microtubule-associated proteins was increased in Taxotere-treated prostate cancer cells, confirming the microtubule-targeting effect of Taxotere. Clustering analysis showed downregulation of some genes for cell proliferation and cell cycle. In contrast, Taxotere upregulated some genes that are related to induction of apoptosis and cell cycle arrest. From these results, we conclude that Taxotere caused alterations of a large number of genes, many of which may contribute to the molecular mechanism(s) by which Taxotere affects prostate cancer cells. Further molecular studies are needed in order to determine the cause and effect relationships between these genes altered by Taxotere. Nevertheless, our results could be further exploited for devising strategies to optimize therapeutic effects of Taxotere for the treatment of prostate cancer.

Antimetastatic drugs in prostate cancer

Despite the benefits of local therapy with radical prostatectomy and radiation, many patients with prostate cancer require hormonal ablation. While chemotherapy has proven efficacy when the disease progresses to androgen-independent prostate cancer, patients ultimately succumb to the disease, thus the identification of other active therapies is needed. Future treatment modalities include molecular targeted therapies. Prostate cancer has been an ideal model to study the multiple steps required in the metastatic cascade. These steps have been utilized in the development of metastasis inhibitors. This review will present promising agents that have been tested preclinically or are undergoing clinical investigation for their abilities in preventing prostate cancer metastasis. Because prostate cancer metastasizes preferentially to the bone, special attention will be given to agents that interfere with this pattern of metastasis. Specifically, the efficacy of angiogenesis inhibitors, metalloproteinase inhibitors, inhibitors of prostate cancer cell- endothelial cell interactions, and bisphosphonates will be reported. In addition, the introduction of these novel agents has raised many questions as to the relevance and optimal utilization of current clinical trial designs. Issues regarding combination therapy with chemotherapy, optimal timing of treatment with metastatic inhibitors, and the need for surrogate endpoints for molecular targeted therapies will be discussed.

LynIs a Target Gene for Prostate Cancer

The Src-related protein kinase Lyn plays an important role in B-cell activation. However, several lines of evidence suggest that it is also involved in the control of cellular proliferation and the inhibition of apoptosis. We have discovered that Lyn is expressed in normal prostate epithelia, in 95% of primary human prostate cancer (PC) specimens examined, and in all of the PC cell lines that we assayed. Moreover, Lyn knockout mice display abnormal prostate gland morphogenesis, which suggests that Lyn plays an important role in prostate epithelium development and implies that Lyn is a candidate target for specific therapy for PC. Using a drug-design strategy to construct sequence-based peptide inhibitors, a Lyn-specific inhibitor, KRX-123, targeting a unique interaction site within Lyn, was synthesized. KRX-123 was found to inhibit cellular proliferation in three hormone-refractory PC cell lines, DU145, PC3, and TSU-Pr1 with IC(50) values of 2-4 micro M. In vivo, tumor volume of DU145 explants in nude mice was significantly reduced after once-a-week injections of KRX-123, at a dose of 10 mg/kg, for a period of 5 weeks. Histological analyses of the treated tumors indicated extensive apoptosis. Thus, we suggest that Lyn inhibition may serve as a prime target for the treatment of hormone-refractory PC.

Changes in extracellular matrix (ECM) and ECM-associated proteins in the metastatic progression of prostate cancer

Prostate cancer (PCa) is no exception to the multi-step process of metastasis. As PCa progresses, changes occur within the microenvironments of both the malignant cells and their targeted site of metastasis, enabling the necessary responses that result in successful translocation. The majority of patients with progressing prostate cancers develop skeletal metastases. Despite advancing efforts in early detection and management, there remains no effective, long-term cure for metastatic PCa. Therefore, the elucidation of the mechanism of PCa metastasis and preferential establishment of lesions in bone is an intensive area of investigation that promises to generate new targets for therapeutic intervention. This review will survey what is currently know concerning PCa interaction with the extracellular matrix (ECM) and the roles of factors within the tumor and ECM microenvironments that contribute to metastasis. These will be discussed within the context of changes in expression and functional heterodimerization patterns of integrins, changes in ECM expression and reorganization by proteases facilitating invasion. In this context we also provide a brief summary of how growth factors (GFs), cytokines and regulatory signaling pathways favor PCa metastasis to bone.

Bcl-2 and Bcl-x(L) differentially protect human prostate cancer cells from induction of apoptosis by melanoma differentiation associated gene-7, mda-7/IL-24

Subtraction hybridization identified melanoma differentiation associated gene-7, mda-7, in the context of terminally differentiated human melanoma cells. Based on its structure, cytokine-like properties and proposed mode of action, mda-7 has now been classified as IL-24. When expressed by means of a replication-incompetent adenovirus, Ad.mda-7 induces apoptosis in a broad range of cancer cells, without inducing harmful effects in normal fibroblast or epithelial cells. These unique properties of mda-7/IL-24 suggest that this gene will prove beneficial for cancer gene therapy. We now demonstrate that Ad.mda-7 decreases viability by induction of apoptosis in hormone-responsive (LNCaP) and hormone-independent (DU-145 and PC-3) human prostate carcinomas, without altering growth or survival in early-passage normal human prostate epithelial cells (HuPEC). Ad.mda-7 causes G(2)/M arrest and apoptosis in LNCaP (p53-wildtype), DU-145 (p53 mutant, Bax-negative) and PC-3 (p53-negative) prostate carcinomas, but not in HuPEC. Apoptosis induction correlated with changes in the ratio of pro- to antiapoptotic Bcl-2 protein family members. A potential functional role for changes in bcl-2 family gene expression in Ad.mda-7-induced apoptosis was suggested by the finding that forced overexpression of bcl-x(L) or bcl-2 differentially diminished the apoptotic effect of Ad.mda-7 in prostate carcinomas. These results confirm that induction of apoptosis by the mda-7/IL-24 gene in prostate cancer cells is Bax- and p53-independent and is mediated by mitochondrial pathways involving bcl-2 family gene members. The mda-7/IL-24 gene represents a new class of cancer-specific apoptosis-inducing genes with obvious potential for the targeted gene-based therapy of human prostate cancer.

Inhibition of prostate cancer metastatic colonization by approximately 4.2 Mb of human chromosome 12

Our previous studies demonstrate that introduction of a approximately 70 cM region (now estimated at 63.75 Mb by the Human Genome Project) of human chromosome 12 into the highly metastatic Dunning rat prostate cancer cell line AT6.1 results in >30-fold (>/=90%) reduction in the number of overt metastases in spontaneous metastasis assays. We report the further localization and biological characterization of the metastasis-suppressor activity encoded by a reduced region of chromosome 12. To localize this metastasis-suppressor activity, a panel of AT6.1 microcell hybrids that retain varying portions of human chromosome 12 was constructed and subjected to sequence-tagged site (STS)-based PCR analysis and assessment of in vivo metastatic ability. Data from these complementary approaches localized the metastasis-suppressor activity to a approximately 4.2 Mb portion of human chromosome 12q24.3 comprised of 3 separate regions. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were used for differential expression analyses to identify which characterized genes, predicted gene sequences and expressed sequence tags (ESTs) within this region could be responsible for the observed metastasis suppression. Comprehensive in vivo studies showed that suppressed AT6.1-12 hybrids that retain the metastasis-suppressor region on 12q24.3 are capable of arriving at the secondary site, but are not able to persist there. Thus, unlike other metastasis-suppressor genes characterized to date, the metastasis-suppressor gene encoded by this region appears to utilize a different biologic mechanism to suppress the growth of overt metastases at the secondary site.

Molecular and genetic prognostic factors of prostate cancer

Prostate cancer is the most commonly diagnosed cancer in Western males, responsible for 3% of all deaths in men over 55 years of age and second only to lung cancer as a cause of cancer death. Biomarkers have become an important diagnostic tool in prostate cancer. The discovery of the serum marker prostate-specific antigen (PSA) significantly facilitated the detection and management of prostate cancer. As we enter into the post-genomics era, novel biomarkers of prostate cancer of therapeutic significance will invariably emerge. Here we review a series of existing and emerging molecular-based prognostic markers particularly with radiotherapy.

Metastasis suppressor pathways--an evolving paradigm

A greater understanding of the processes of tumor invasion and metastasis, the principal cause of death in cancer patients, is essential to determine newer therapeutic targets. Metastasis suppressor genes, by definition, suppress metastasis without affecting tumorigenicity and, hence, present attractive targets as prognostic or therapeutic markers. This short review focuses on those twelve metastasis suppressor genes for which functional data exist. We also outline newly identified genes that bear promising traits of having metastasis suppressor activity, but for which functional data have not been completed. We also summarize the biochemical mechanism(s) of action (where known), and present a working model assembling potential metastasis suppression pathways.

[Molecular diagnostics of prostate cancer]

Although a number of studies have identified molecular markers for prostate cancer, their clinical utility remains mainly unclear. Markers, which allow improved determination of the biological aggressiveness of individual prostate cancers, may help to optimize therapeutic management of this heterogeneous tumor type. Here, a subset of molecular markers, which are intensively discussed in the literature or which are supposed to gain clinical utility in the future, are described in more detail. For a better survey, the markers are divided into (a) susceptibility markers, (b) malignancy markers, and (c) aggressiveness markers. The number of markers described as well as the inconsistency across studies in assessing their clinical utility reflect the heterogeneity of prostate cancer also on a genetic level so that it is unlikely that a single marker will gain clinical relevance. Future research must include systematic analysis of the clinical utility of not only single markers but rather of marker profiles in appropriate studies.

The use of gene-specific IgY antibodies for drug target discovery

Genomics and gene expression data require interpretation at the protein level to validate the biological or pathological findings. To match with the efficiency and capacity of DNA microarray application, methods and approaches of protein analysis in multiplex and high-throughput manner are required for effectively discovering disease-related proteins. Two-dimensional gel and MS-based technologies provide researchers with such approaches, but neither of them can directly and selectively detect target proteins in situ. Antibodies are one of the most crucial tools for meeting this need. Efficient generation of antibodies based on genomics and gene-expression information is an important strategy for producing gene-specific antibodies to link genome to proteome. Avian immunoglobulins isolated from egg yolk (so-called IgY) have several attractive advantages over conventional IgG antibodies.

Gene expression profiles of I3C- and DIM-treated PC3 human prostate cancer cells determined by cDNA microarray analysis

Studies from our laboratory and others have shown that indole-3-carbinol (I3C) and its in vivo dimeric product, 3,3'-diindolylmethane (DIM), inhibit the growth of PC3 prostate cancer cells and induce apoptosis by inhibiting nuclear factor (NF)-kappaB and Akt pathways. To obtain comprehensive gene expression profiles altered by I3C- and DIM-treated PC3 cells, we utilized cDNA microarray to interrogate the expression of 22,215 known genes using the Affymetrix Human Genome U133A Array. We found a total of 738 genes that showed a greater than twofold change after 24 h of DIM treatment. Among these genes, 677 genes were down-regulated and 61 were up-regulated. Similarly, 727 genes showed a greater than twofold change in expression, with down-regulation of 685 genes and up-regulation of 42 genes in I3C-treated cells. The altered expressions of genes were observed as early as 6 h and were more evident with longer treatment. Upon cluster analysis, we found that both I3C and DIM up-regulated the expression of genes that are related to the Phase I and Phase II enzymes, suggesting their increased capacity for detoxification of carcinogens or chemicals. We also found that I3C and DIM down-regulated the expression of genes that are critically involved in the regulation of cell growth, cell cycle, apoptosis, signal transduction, Pol II transcription factor and oncogenesis. Real-time reverse transcription-polymerase chain reaction analysis was conducted to confirm the cDNA microarray data, and the results were consistent. We conclude that I3C and DIM affected the expression of a large number of genes that are related to the control of carcinogenesis, cell survival and physiologic behaviors. This may help determine the molecular mechanism(s) by which I3C and DIM exert their pleiotropic effects on PC3 prostate cancer cells; in addition, this information could be further exploited for devising chemopreventive and/or therapeutic strategies for prostate cancer.

Stromal factors involved in prostate carcinoma metastasis to bone

BACKGROUND

Prostate carcinoma (PC) frequently metastasizes to bone, where it causes significant morbidity and mortality. Stromal elements in the primary and metastatic target organs are important mediators of tumor cell intravasation, chemoattraction, adhesion to target organ microvascular endothelium, extravasation, and growth at the metastatic site.

METHODS

The role of stromal factors in bone metastasis was determined with a cyclic DNA microarray comparison of a bone-derived cell PC cell line with a soft tissue-derived cell PC cell line and by evaluating the effects of selected stromal components on PC cell chemotaxis, cell adhesion to human bone marrow endothelium (HBME), and PC cell growth.

RESULTS

The authors demonstrate that PC cells express protease-activated receptor 1 (PAR1; thrombin receptor), and its expression is up-regulated in PC compared with normal prostate tissue. In addition, this overexpression was very pronounced in bone-derived PC cell lines (VCaP and PC-3) compared with soft tissue PC cell lines (DUCaP, DU145, and LNCaP). The authors report that bone stromal factors, including stromal cell-derived factor 1 (SDF-1) and collagen Type I peptides, are chemoattractants for PC cells, and they demonstrate that some of these factors (e.g., extracellular matrix components, transforming growth factor beta, bone morphogenic proteins [BMPs], and SDF-1) significantly alter PC-HBME interaction in vitro. Finally, stromal factors, such as BMPs, can regulate the proliferation of PC cells in vitro.

CONCLUSIONS

Soluble and insoluble elements of the stroma are involved in multiple steps of PC metastasis to bone. The authors hypothesize that PAR1 may play a central role in prostate tumorigenesis.

Down-regulation of invasion and angiogenesis-related genes identified by cDNA microarray analysis of PC3 prostate cancer cells treated with genistein

Prostate cancer is the second leading cause of cancer related deaths in men in the United States and for many years the treatment results for metastatic prostate cancer have been disappointing. Our previous studies have shown that genistein elicits pleiotropic effects on prostate cancer cells; however, its role in invasion and metastasis has not been fully elucidated. In order to better understand the precise molecular mechanism(s) by which genistein exerts its effects on PC3 cells, we have utilized cDNA microarray to interrogate 12558 known genes to determine the gene expression profile altered by genistein treatment. We found a total of 832 genes which showed >2-fold change after genistein treatment. Among these genes, we found down-regulation of 11 genes (MMP-9, protease M, uPAR, VEGF, neuropilin, TSP, BPGF, LPA, TGF-beta2, TSP-1, PAR-2) and up-regulation of two genes (connective tissue growth factor, connective tissue activation peptide), which are related to angiogenesis, tumor cell invasion and metastasis. Reverse transcription-polymerase chain reaction, Western blot, and zymographic analysis were conducted to confirm the data of microarray at the level of mRNA, protein, and biological function. The results were in direct agreement with the microarray data. From these results, we conclude that genistein down-regulates the transcription and translation of genes critically involved in the control of angiogenesis, tumor cell invasion and metastasis, suggesting the possible therapeutic role of genistein for metastatic prostate cancer. Thus, genistein-induced alternations of gene expressions may be exploited for devising chemopreventive or therapeutic strategies, particularly for chemosensitization of metastatic prostate cancer to existing chemotherapeutic agents.

Cytogenetics and molecular genetics of cancer of the prostate

Prostate cancer remains the most common male malignancy in Western countries and the second-leading cause of death from cancer in males. Progress in the understanding of molecular and genetic mechanisms leading to this disease has only recently begun to offer a glimpse of the genes, chromosomal sites, and proteins implicated in the development and progression of prostate tumors. This brief review addresses some of the key issues in prostate cancer research, including a discussion of both hereditary and sporadic cancers as well as specific genes and chromosomal loci that likely play a part in the etiology of this disease.

Prostatic intraepithelial neoplasia in genetically engineered mice

Several mouse models of human prostate cancer were studied to identify and characterize potential precursor lesions containing foci of atypical epithelial cells. These lesions exhibit a sequence of changes suggesting progressive evolution toward malignancy. Based on these observations, a grading system is proposed to classify prostatic intraepithelial neoplasia (PIN) in genetically engineered mice (GEM). Four grades of GEM PIN are proposed based on their architecture, differentiation pattern, and degree of cytological atypia. PIN I lesions have one or two layers of atypical cells. PIN II has two or more layers of atypical cells. PIN III has large, pleomorphic nuclei with prominent nucleoli and the cells tend to involve the entire lumen with expansion of the duct outlines. PIN IV lesions contain atypical cells that fill the lumen and bulge focally into, and frequently compromise, the fibromuscular sheath. Within the same cohorts, the lower grade PINs first appear earlier than the higher grades. Morphometric and immunohistochemical analyses confirm progressive change. Although the malignant potential of PIN IV in mice has not been proven, GEM PIN is similar to human PIN. This PIN classification system is a first step toward a systematic evaluation of the biological potential of these lesions in GEM.