miR-25 Modulates Invasiveness and Dissemination of Human Prostate Cancer Cells via Regulation of αv- and α6-Integrin Expression

Altered microRNA (miRNA; miR) expression is associated with tumor formation and progression of various solid cancers. A major challenge in miRNA expression profiling of bulk tumors is represented by the heterogeneity of the subpopulations of cells that constitute the organ, as well as the tumor tissue. Here, we analyzed the expression of miRNAs in a subpopulation of epithelial stem/progenitor-like cells in human prostate cancer [prostate cancer stem cell (PCSC)] and compared their expression profile to more differentiated cancer cells. In both cell lines and clinical prostate cancer specimens, we identified that miR-25 expression in PCSCs was low/absent and steadily increased during their differentiation into cells with a luminal epithelial phenotype. Functional studies revealed that overexpression of miR-25 in prostate cancer cell lines and selected subpopulation of highly metastatic and tumorigenic cells (ALDH(high)) strongly affected the invasive cytoskeleton, causing reduced migration in vitro and metastasis via attenuation of extravasation in vivo. Here, we show, for the first time, that miR-25 can act as a tumor suppressor in highly metastatic PCSCs by direct functional interaction with the 3'-untranslated regions of proinvasive αv- and α6-integrins. Taken together, our observations suggest that miR-25 is a key regulator of invasiveness in human prostate cancer through its direct interactions with αv- and α6-integrin expression.

DNA hypermethylation in prostate cancer is a consequence of aberrant epithelial differentiation and hyperproliferation

Prostate cancer (CaP) is mostly composed of luminal-like differentiated cells, but contains a small subpopulation of basal cells (including stem-like cells), which can proliferate and differentiate into luminal-like cells. In cancers, CpG island hypermethylation has been associated with gene downregulation, but the causal relationship between the two phenomena is still debated. Here we clarify the origin and function of CpG island hypermethylation in CaP, in the context of a cancer cell hierarchy and epithelial differentiation, by analysis of separated basal and luminal cells from cancers. For a set of genes (including GSTP1) that are hypermethylated in CaP, gene downregulation is the result of cell differentiation and is not cancer specific. Hypermethylation is however seen in more differentiated cancer cells and is promoted by hyperproliferation. These genes are maintained as actively expressed and methylation-free in undifferentiated CaP cells, and their hypermethylation is not essential for either tumour development or expansion. We present evidence for the causes and the dynamics of CpG island hypermethylation in CaP, showing that, for a specific set of genes, promoter methylation is downstream of gene downregulation and is not a driver of gene repression, while gene repression is a result of tissue-specific differentiation.

Retinoic acid represses invasion and stem cell phenotype by induction of the metastasis suppressors RARRES1 and LXN

The mouse haematopoietic stem cell (SC) regulator Latexin (LXN) is the only known homologue of the retinoic acid receptor responder 1 (RARRES1) gene. Both genes lie adjacent on chromosome 3 and differ mostly by the presence of a transmembrane domain in RARRES1. Despite their homology, it is not known whether they possess similar regulatory mechanisms, cellular localization and function. Here, we identified RARRES1 and LXN as highly significantly downregulated genes in human prostate SCs, whose expression was induced by the pro-differentiation agent all-trans retinoic acid (atRA). AtRA induced expression in the most differentiated cells compared with the SC fraction, suggesting that this subpopulation was less responsive to atRA. Small interfering RNA suppression of RARRES1 and LXN enhanced the SC properties of primary prostate cultures, as shown by a significant increase in their colony-forming ability. Expression of both RARRES1 and LXN was co-ordinately repressed by DNA methylation in prostate cancer cell lines and inhibition of RARRES1 and LXN increased the invasive capacity of primary prostate cultures, which also fully rescued an inhibitory effect induced by atRA. Moreover, we showed that RARRES1 and LXN reside within different sub-cellular compartments, providing evidence that RARRES1 is not a plasma membrane protein as previously supposed but is located primarily in the endoplasmic reticulum; whereas LXN was detected in the nucleus of prostate epithelial cells. Thus, LXN and RARRES1 are potential tumour suppressor genes, which are co-ordinately regulated, SC-silenced genes functioning to suppress invasion and colony-forming ability of prostate cancer cells; yet the proteins reside within different sub-cellular compartments.

A transductionally retargeted adenoviral vector for virotherapy of Her2/neu-expressing prostate cancer

The efficacy of adenovirus (Ad)-based gene therapy of solid tumors, such as prostate cancer, is limited. One of the many problems is that the virus infects many different cell types in the body, resulting in high toxicity, whereas the target cancer cells are often less prone to wild-type Ad infection. Our aim was to develop genetically de- and retargeted Ad vectors to reduce off-target effects and increase target infection for prostate cancer. We have previously reported an Ad5 vector specific for the cancer-associated receptor Her2/neu, created by inserting Her2/neu-reactive Affibody(®) molecules (ZH) into the HI loop of a coxsackievirus and adenovirus receptor binding-ablated fiber (Ad[ZH/1]). In addition to virus retargeting to Her2/neu, this virus was further modified from wild-type Ad by changing the RGD motif in the penton base to EGD and by substitution of the KKTK motif in the third shaft repeat to RKSK, resulting in the vector Ad[ZH/3]. The ZH-containing vectors could be produced to high titers and were specific for their target, resulting in efficient infection and killing of Her2/neu-positive androgen-dependent PC346C prostate cancer cells in vitro. Here we show that the oncolytic Ad[ZH/3] vector significantly prolonged survival time and reduced serum prostate-specific antigen levels in an orthotopic prostate tumor model in nude mice to the same extent as wild-type Ad5. Our results show that Her2/neu targeting using Ad-based vectors for prostate cancer is feasible and may serve as a basis for the development of gene therapy of human prostate cancer as well as other Her2/neu-expressing cancers.

In vitro primary cell culture as a physiologically relevant method for preclinical testing of human oncolytic adenovirus

Ad[I/PPT-E1A] is an oncolytic adenovirus that specifically kills prostate cells via restricted replication by a prostate-specific regulatory element. Off-target replication of oncolytic adenoviruses would have serious clinical consequences. As a proposed ex vivo test, we describe the assessment of the specificity of Ad[I/PPT-E1A] viral cytotoxicity and replication in human nonprostate primary cells. Four primary nonprostate cell types were selected to mimic the effects of potential in vivo exposure to Ad[I/PPT-E1A] virus: bronchial epithelial cells, urothelial cells, vascular endothelial cells, and hepatocytes. Primary cells were analyzed for Ad[I/PPT-E1A] viral cytotoxicity in MTS assays, and viral replication was determined by hexon titer immunostaining assays to quantify viral hexon protein. The results revealed that at an extreme multiplicity of infection of 500, unlikely to be achieved in vivo, Ad[I/PPT-E1A] virus showed no significant cytotoxic effects in the nonprostate primary cell types apart from the hepatocytes. Transmission electron microscopy studies revealed high levels of Ad[I/PPT-E1A] sequestered in the cytoplasm of these cells. Adenoviral green fluorescent protein reporter studies showed no evidence for nuclear localization, suggesting that the cytotoxic effects of Ad[I/PPT-E1A] in human primary hepatocytes are related to viral sequestration. Also, hepatocytes had increased amounts of coxsackie adenovirus receptor surface protein. Active viral replication was only observed in the permissive primary prostate cells and LNCaP prostate cell line, and was not evident in any of the other nonprostate cells types tested, confirming the specificity of Ad[I/PPT-E1A]. Thus, using a relevant panel of primary human cells provides a convenient and alternative preclinical assay for examining the specificity of conditionally replicating oncolytic adenoviruses in vivo.

Herpes simplex virus type 1 DNA sequences are present in aged normal and Alzheimer's disease brain but absent in lymphocytes

The etiology of Alzheimer's disease (AD) is unknown. Viruses have been suggested as a possible factor but the issue is still unresolved. We have detected herpes simplex virus type 1 DNA sequences in AD and normal brain, using polymerase chain reaction (PCR), and have now searched for the DNA in lymphocytes from AD patients and age-matched normal individuals; PCR shows that the virus is absent in the lymphocytes.

Prostate cancer stem cells: a target for new therapies

Prostate cancer is now a common disease in men over 50 years of age. Medical therapies for prostate cancer are based on discoveries from the mid-twentieth century, and in the long term are rarely curative. Most treatments are directed towards an androgen receptor-expressing, highly proliferative target cell, which does indeed form the vast majority of cells in a prostate tumour. However, by invoking the existence of a cancer stem cell which, like normal epithelial stem cells in the prostate, does not express androgen receptor and is relatively quiescent, the observed resistance to most medical therapies can be explained. The phenotype of the prostate cancer stem cells is that of a basal cell and cultures derived from cancers, but not benign tissues, express a range of prostate cancer-associated RNAs. Furthermore, stem cells purified on the basis of alpha2beta1 high integrin and CD133 cell surface antigen expression, from an established culture of Gleason 4 (2+2) prostate cancer (P4E6), were able to form multiple intraprostatic tumours in nude mice when grafted orthotopically in a matrigel plug containing human prostatic stroma. The final tumours reexpressed androgen receptor and displayed a histology similar to that of a Gleason 4 cancer.

Identification of degradome components associated with prostate cancer progression by expression analysis of human prostatic tissues

Extracellular proteases of the matrix metalloproteinase (MMP) and serine protease families participate in many aspects of tumour growth and metastasis. Using quantitative real-time RT–PCR analysis, we have undertaken a comprehensive survey of the expression of these enzymes and of their natural inhibitors in 44 cases of human prostate cancer and 23 benign prostate specimens. We found increased expression of MMP10, 15, 24, 25 and 26, urokinase plasminogen activator-receptor (uPAR) and plasminogen activator inhibitor-1 (PAI1), and the newly characterised serine proteases hepsin and matriptase-1 (MTSP1) in malignant tissue compared to benign prostate tissue. In contrast, there was significantly decreased expression of MMP2 and MMP23, maspin, and the protease inhibitors tissue inhibitor of metalloproteinase 3 (TIMP3), TIMP4 and RECK (reversion-inducing cysteine-rich protein with Kazal motifs) in the cancer specimens. The expression of MMP15 and MMP26 correlated positively with Gleason score, whereas TIMP3, TIMP4 and RECK expression correlated negatively with Gleason score. The cellular localisation of the expression of the deregulated genes was evaluated using primary malignant epithelial and stromal cell cultures derived from radical prostatectomy specimens. MMP10 and 25, hepsin, MTSP1 and maspin showed predominantly epithelial expression, whereas TIMP 3 and 4, RECK, MMP2 and 23, uPAR and PAI1 were produced primarily by stromal cells. These data provide the first comprehensive and quantitative analysis of the expression and localisation of MMPs and their inhibitors in human prostate cancer, leading to the identification of several genes involved in proteolysis as potential prognostic indicators, in particular hepsin, MTSP1, MMP26, PAI1, uPAR, MMP15, TIMP3, TIMP4, maspin and RECK.

Clusterin overexpression in both malignant and nonmalignant prostate epithelial cells induces cell cycle arrest and apoptosis

Expression of the castration-induced clusterin protein is incompatible with the survival of human prostate cancer cells in tissues and in cell culture. To investigate the fate of human prostate epithelial cells, when engineered to maintain expression of clusterin protein, we have used an IRES-hyg vector and hygromycin selection. PC-3 prostate tumour cells were substantially more sensitive to clusterin expression than nonmalignant PNT1a cells, showing multiple phenotypic changes including cell cycle arrest and increased apoptosis. The results strengthen the hypothesis that clusterin expression is proapoptotic. Expression of exogenous clusterin in both cell types resulted in its relocation from the cytoplasm and a nuclear accumulation of the protein, as was also seen in the same cells when apoptosis was induced by etoposide treatment. To survive clusterin expression, the PC-3 tumour cells developed apoptosis-inhibitory properties. This could have significance for the resistance of prostate cancers to chemo/radiotherapy, where clusterin overexpression is observed.

Targeting gene therapy for prostate cancer

Gene therapy is rapidly emerging as a viable clinical strategy to treat prostate cancer. New developments, such as targeted expression of therapeutic genes, and viruses that are designed to selectively replicate in prostate cancer cells have led to vectors with improved safety, even in elderly male patients. This review describes the various different viral and non-viral strategies employed to date, with a summary of current clinical trials. The main focus of the review is a discussion of the need, and the potential methods that can be used for targeted expression of the therapeutic gene specifically to prostate tumours and metastases. This includes methods of abrogating vector transduction of non-specific tissues, enhancement of transduction into prostate tumour tissue, transcriptional control of the therapeutic gene and some examples of prostate cancer-specific therapeutic genes. We also consider the future of prostate cancer gene therapy and the factors that should be taken into account when designing clinical trials, in a field that is expected to impact on clinical management of a common tumour type.

Stromal-epithelial interactions influence prostate cancer cell invasion by altering the balance of metallopeptidase expression

Perturbations of stromal–epithelial interactions in the developing tumour can contribute to cancer invasion and metastasis. The structurally related metallopeptidases endothelin-converting enzyme (ECE) and neutral endopeptidase (NEP) contribute sequentially to the synthesis and inactivation of ET-1, a mitogenic peptide that has been shown to affect tumour behaviour. This study has investigated the interaction between metastatic tumour epithelial cells, which lack NEP, and stromal cells, which we have shown to express ECE-1 (stromal–epithelial interactions), using Matrigel invasion chambers. The epithelial cell lines utilised in this study include androgen-sensitive LNCaP, androgen-independent PC-3, Du145 and recently established PNT-1a, PNT2-C2 and P4E6 prostate cell lines. Specific inhibition of endogenous ECE-1 activity in stromal cells reduced PC-3 and Du145 invasion by 70 and 50%, respectively. Addition of recombinant NEP to inactivate endogenous mitogenic peptides resulted in 50 and 20% reductions in invasion in PC-3 and Du145 cells, respectively. Neutral endopeptidase effects were reversed in the presence of thiorphan, a specific NEP inhibitor. Supplementation of defined media with bradykinin and ET-1 significantly increased PC-3 invasion by 40 and 50%, respectively. Du145 cell invasion increased by approximately 100% on adding ET-1. These studies implicate the metallopeptidases NEP and ECE-1 as mediators of prostate cancer invasion via a stromal/epithelial interaction.

Structure of the human S100A12-copper complex: implications for host-parasite defence

S100A12 is a member of the S100 family of EF-hand calcium-modulated proteins. Together with S100A8 and S100A9, it belongs to the calgranulin subfamily, i.e. it is mainly expressed in granulocytes, although there is an increasing body of evidence of expression in keratinocytes and psoriatic lesions. As well as being linked to inflammation, allergy and neuritogenesis, S100A12 is involved in host-parasite response, as are the other two calgranulins. Recent data suggest that the function of the S100-family proteins is modulated not only by calcium, but also by other metals such as zinc and copper. Previously, the structure of human S100A12 in low-calcium and high-calcium structural forms, crystallized in space groups R3 and P2(1), respectively, has been reported. Here, the structure of S100A12 in complex with copper (space group P2(1)2(1)2; unit-cell parameters a = 70.6, b = 119.0, c = 90.2 A) refined at 2.19 A resolution is reported. Comparison of anomalous difference electron-density maps calculated with data collected with radiation of wavelengths 1.37 and 1.65 A shows that each monomer binds a single copper ion. The copper binds at an equivalent site to that at which another S100 protein, S100A7, binds zinc. The results suggest that copper binding may be essential for the functional role of S100A12 and probably the other calgranulins in the early immune response.

The structure of S100A12 in a hexameric form and its proposed role in receptor signalling

S100A12 is a member of the S100 subfamily of EF-hand calcium-binding proteins; it has been shown to be one of the ligands of the 'receptor for advanced glycation end products' (RAGE) that belongs to the immunoglobulin superfamily and is involved in diabetes, Alzheimer's disease, inflammation and tumour invasion. The structure of the dimeric form of native S100A12 from human granulocytes in the presence of calcium in space group R3 has previously been reported. Here, the structure of a second crystal form in space group P2(1) (unit-cell parameters a = 53.9, b = 100.5, c = 112.7A, beta = 94.6 degrees) solved at 2.7A resolution by molecular replacement using the R3 structure as a search model is reported. Like most S100 proteins, S100A12 is a dimer. However, in the P2(1) crystal form dimers of S100A12 are arranged in a spherical hexameric assembly with an external diameter of about 55 A stabilized by calcium ions bound between adjacent dimers. The putative target-binding sites of S100A12 are located at the outer surface of the hexamer, making it possible for the hexamer to bind several targets. It is proposed that the S100A12 hexameric assembly might interact with three extracellular domains of the receptor, bringing them together into large trimeric assemblies.

Experimental prostate epithelial morphogenesis in response to stroma and three-dimensional matrigel culture

To reproduce the structural and functional differentiation of human prostatic acini in vivo, prostatic epithelial and stromal cells derived from human primary cultures were cocultured in Matrigel. In the absence of stroma and serum, epithelial spheroids composed of solid masses of stratified and cuboidal cells formed. Outer cells of the spheroid expressed cytokeratins 1, 5, 10, and 14, whereas the inner cells expressed cytokeratin 18. The addition of 2% serum induced formation of a lumen surrounded by a layer of one or two cuboidal and columnar epithelial cells. The further addition of stromal cultures, dihydrotestosterone, and estrogen induced polarization of the epithelium and increased spheroid-forming efficiency. Epithelium expressed either cytokeratin 18 alone or additionally cytokeratins 1, 5, 14, and 10. All spheroid epithelium expressed prostate-specific antigen and prostate-specific membrane antigen. Androgen receptor was only detected in the presence of stroma, serum, and hormones. Thus, development of a functional and morphologically correct prostate gland in vitro is dependent on extracellular matrix, steroid hormones, and factors from stromal cells and serum.

Identification and isolation of human prostate epithelial stem cells based on α2β1-integrin expression

A major impediment to our understanding of the biology of stem cells is the inability to distinguish them from their differentiating progeny. We made use of the known association of stem cells with basement membranes to isolate prostate epithelial stem cells. We show that, in vivo, putative stem cells express higher levels of the α2-integrin subunit than other cells within the basal layer. Approximately 1% of basal cells examined by confocal microscopy were integrin ‘bright’, and these cells can be selected directly from the tissue on the basis of rapid adhesion to type I collagen. This selected population has a basal phenotype, as determined by expression of CK5 and CK14 and lack of expression of the differentiation-specific markers prostate specific antigen (PSA) and prostatic acid phosphatase (PAP), and has a fourfold greater ability to form colonies in vitro than the total basal population. These putative stem cells are distinguished from other basal cells by their ability to generate prostate-like glands in vivo with morphologic and immuno-histochemical evidence of prostate-specific differentiation. These properties are consistent with a stem cell origin. Furthermore, the presence of surface integrins on prostate stem cells suggests that these cells share common pathways with stem cells in other tissues.

Prostate epithelial cell lines form spheroids with evidence of glandular differentiation in three-dimensional Matrigel cultures

Normal (PNT2-C2) and metastatic (PC-3) prostate cell lines were grown in Matrigel to observe the effects on morphology and phenotype in comparison to monolayer culture. In monolayer cultures, PNT2-C2 showed typical round/cuboidal epithelial morphology, with tight cell associations, whereas in Matrigel they formed smooth spheroids, tightly packed with cells. In both monolayer and Matrigel, PNT2-C2 had a differentiated luminal epithelial phenotype with high expression of cytokeratin 8, prostate specific antigen (PSA), prostate specific membrane antigen (PSMA), E-cadherin and desmoglein. In contrast, PC-3 cells possessed an epithelial/mesenchyme morphology in monolayer with loose cell to cell contact and pseudopodial extensions. Immunohistochemical phenotyping indicated the cells were undifferentiated, expressing high levels of vimentin, beta1 integrin, CD44 and low expression of cytokeratin 8. In Matrigel they formed smooth and irregular spheroids, which had a lumen surrounded by a single cell layer. Matrigel also influenced the expression of PSA, PSMA and CD44. These results indicate that Matrigel culture can induce morphological differentiation of prostate cancer cells which initially had a basal phenotype.

The dimerization interface of the metastasis-associated protein S100A4 (Mts1): in vivo and in vitro studies

The S100 calcium-binding proteins are implicated in signal transduction, motility, and cytoskeletal dynamics. The three-dimensional structure of several S100 proteins revealed that the proteins form non-covalent dimers. However, the mechanism of the S100 dimerization is still obscure. In this study we characterized the dimerization of S100A4 (also named Mts1) in vitro and in vivo. Analytical ultracentrifugation revealed that apoS100A4 was present in solution as a mixture of monomers and dimers in a rapidly reversible equilibrium (K(d) = 4 +/- 2 microm). The binding of calcium promoted dimerization. Replacement of Tyr-75 by Phe resulted in the stabilization of the dimer. Helix IV is known to form the major part of the dimerization interface in homologous S100 proteins. By using the yeast two-hybrid system we showed that only a few residues of helix IV, namely Phe-72, Tyr-75, Phe-78, and Leu-79, are essential for dimerization in vivo. A homology model demonstrated that these residues form a hydrophobic cluster on helix IV. Their role is to stabilize the structure of individual subunits rather than provide specific interactions across the dimerization surface. Our mutation data showed that the specificity at the dimerization surface is not particularly stringent, which is consistent with recent data indicating that S100 proteins can form heterodimers.

In vitro models to study cellular differentiation and function in human prostate cancers

In Vitro Models to Study Cellular Differentiation and Function in Human Prostate Cancers. To augment the currently available models of human prostate cancer in vitro, we have established extended life-span epithelial cultures from biopsies of well-differentiated prostate cancers. The genetic identity of the target cells was assessed by allelotyping, using microsatellites located on chromosome 8p, and microdissection of tissues and primary cell cultures. Cells with an extended life span (PxE6) were derived by recombinant retrovirus infection to introduce the human papilloma virus E6 gene (epithelial cells). Immunophenotyping of the resultant cell strains confirmed retention of differentiated cell functions, and the genotype of the E6-expressing epithelial cells was stable, while SV40-immortalized cultures were more unstable, leading to tetraploidy. All PxE6 cells eventually senesced, but an immortalized epithelial culture, P4E6, was derived from one of the epithelial cultures. The properties of this cell line, which remains close to diploid, are similar to those of early prostate cancer cells, and it retains expression of many prostate-associated antigens, such as prostate-specific antigen (PSA).

The three-dimensional structure of human S100A12

The crystal structure of human EF-hand calcium-binding protein S100A12 in its calcium-bound form has been determined to 1.95 A resolution by molecular replacement using the structure of the S100B protein. The S100 family members are homologous to calmodulin and other related EF-hand calcium-binding proteins. Like the majority of S100 proteins, S100A12 is a dimer, with the interface between the two subunits being composed mostly of hydrophobic residues. The fold of S100A12 is similar to the other known crystal and solution structures of S100 proteins, except for the linker region between the two EF-hand motifs. Sequence and structure comparison between members of the S100 family suggests that the target-binding region in S100A12 is formed by the linker region and C-terminal residues of one subunit and the N-terminal residues of another subunit of the dimer. The N-terminal region of the target-binding site includes two glutamates that are conserved in most of the S100 sequences. The comparison also provided a better understanding of the role of the residues important for intra- and inter-subunit hydrophobic interactions. The precise role of S100A12 in cell behaviour is yet undefined, as is the case for the whole family, although it has been shown that the interaction of S100A12 with the RAGE receptor is implicated in inflammatory response.

Alternative splicing of the human PTEN/MMAC1/TEP1 gene

The human tumour suppressor gene PTEN/MMAC1/TEP1 encodes a lipid and protein phosphatase. Using RT-PCR, alternatively spliced forms of PTEN mRNA, encoding full-length PTEN and two forms of the protein truncated at the C-terminal end, were detected in normal human tissue. Cultured tumour and non-tumour cell lines show similar splicing patterns.

Phenotypic effects of overexpression of the MMAC1 gene in prostate epithelial cells

The prostate cancer cell lines PC3 and LNCaP have been shown to lack expression of the tumour suppressor gene MMAC1/PTEN, in contrast to the immortalized non-tumorigenic epithelial lines PNT1a and PNT2. We have measured the effects of reintroduction of wild type (wt) and mutant MMAC1 genes on to these genetic backgrounds, using gene constructs expressing either wt MMAC1 or various mutants deficient in the dual specificity phosphatase domain of the protein. Over-expression of wild type PTEN protein induced cell shrinkage and rounding, but did not result in increased levels of classical apoptosis. Permanently transfected lines containing the MMAC1 gene could only be obtained from the PNT cells, as PTEN expression resulted in rapid loss of both tumour lines. In contrast, mutation of the phosphatase domain resulted in partial attenuation of the phenotypic effects of MMAC1 after transient transfection, and also allowed the derivation of permanent tumour cell lines containing the mutated MMAC1 gene. The results suggest that re-expression of wt PTEN is incompatible with survival of human prostate cancer cells in vitro, and that the full biological activity of this common tumour suppressor requires functions additional to the established protein and lipid phosphatase activities in epithelial systems.

Targeting therapeutic gene expression to human prostate cancers

Most current therapies against human carcinoma of the prostate are palliative rather than curative. Thus, there is a pressing need for new therapies directed against this common tumor, based on knowledge of the basic biology of the prostate, rather than by extrapolation of treatments from other tumor types. This review presents the various levels of prostate targeting which could be and have been applied, at the attachment, expression and therapeutic gene levels to eliminate prostate carcinoma cells in extraprostatic sites. To achieve optimal and safe targeting, a combination approach will be necessary, as there are few genes whose expression can provide absolute prostate specificity.

Inverse relationship between the expression of the human papillomavirus type 16 transcription factor E2 and virus DNA copy number during the progression of cervical intraepithelial neoplasia

The human papillomavirus type 16 (HPV-16) status of 43 cervical biopsies, which had been characterized histologically as normal, various grades of cervical intraepithelial neoplasia (CIN) and invasive squamous cell carcinoma, was examined by using (i) a novel antibody against the HPV-16 E2 protein, (ii) sensitive HPV-16 DNA in situ hybridization and (iii) microdissection/PCR for the E2 ORF. The data indicate that E2 protein expression is highest in koilocytes in lower-grade CIN (I), but decreases with increasing grade, whereas the detection of HPV DNA is delayed until CIN I/II, rising to the highest levels in carcinoma cells. Co-localization of E2 with HPV-16 DNA-positive cells was most commonly observed in koilocytes in CIN II lesions. PCR analyses of microdissected epithelium from the same or serial sections indicated that E2 ORFs were retained in an intact form in a number of higher-grade CIN lesions and invasive carcinomas.

Androgen receptor localisation and turnover in human prostate epithelium treated with the antiandrogen, casodex

In vitro models of normal and malignant human prostate are currently limited to a few well established cell lines that, with a single exception (LNCaP), fail to express the androgen receptor (AR) - a common characteristic of prostatic epithelium grown in culture. To investigate the molecular mechanism of action of the non-steroidal antiandrogen Casodex (bicalutamide) against wild-type AR, we have established a transient AR expression model in non-tumorigenic prostate cells of both epithelial and mesenchymal origin. In this model, both dihydrotestosterone and Casodex can effectively transport the AR protein into the nucleus of prostate cells. Whereas the natural ligand, dihydrotestosterone, stabilises the receptor, the AR is rapidly degraded at a nuclear location when the transfected cells are treated with Casodex. In contrast, whereas the mutant AR in the LNCaP line is also degraded on Casodex treatment over the same time period, its intracellular targeting is defective.

Structure of the intact transactivation domain of the human papillomavirus E2 protein

Papillomaviruses cause warts and proliferative lesions in skin and other epithelia. In a minority of papillomavirus types ('high risk, including human papillomaviruses 16, 18, 31, 33, 45 and 56), further transformation of the wart lesions can produce tumours. The papillomavirus E2 protein controls primary transcription and replication of the viral genome. Both activities are governed by a approximately 200 amino-acid amino-terminal module (E2NT) which is connected to a DNA-binding carboxy-terminal module by a flexible linker. Here we describe the crystal structure of the complete E2NT module from human papillomavirus 16. The E2NT module forms a dimer both in the crystal and in solution. Amino acids that are necessary for transactivation are located at the dimer interface, indicating that the dimer structure may be important in the interactions of E2NT with viral and cellular transcription factors. We propose that dimer formation may contribute to the stabilization of DNA loops which may serve to relocate distal DNA-binding transcription factors to the site of human papillomavirus transcription initiation.

In vitro modelling of epithelial and stromal interactions in non-malignant and malignant prostates

To study the effects of stromal epithelial cell interactions on prostate cancer metastasis, we have used primary human prostatic stromal cells derived from malignant and non-malignant tissues and established epithelial cell lines from normal (PNT1a and PNT2-C2) and tumour (PC-3, DU145 and LNCaP) origins. The effects of stromal cells on epithelial cell growth were studied in direct and indirect (using culture inserts) co-culture and by exposure to stromal cell-conditioned medium (assessed by MTT assay). The influence of stromal cells on epithelial cell invasion was measured using matrigel invasion chambers and on epithelial cell motility using time lapse microscopy. Results indicated that epithelial cell line growth was similarly unaffected or inhibited by stromal cells derived from malignant (n = 8) or non-malignant tissue (n = 8). In contrast, PNT2-C2 and PC-3 cells were found to be the least and the most invasive and motile epithelia respectively. Stromal cultures enhanced the invasion of both epithelial cells, but no differences were observed between the use of malignant and non-malignant tissues. All stromal cultures modestly stimulated PNT2-C2 motility but displayed a greater stimulation of PC-3 cell motility, while stromal cells derived from malignant tissue stimulated PNT2-C2 and PC-3 cell motility more than stromal cultures from non-malignant tissues.

Allelic imbalance within the E-cadherin gene is an infrequent event in prostate carcinogenesis

By exploiting two single nucleotide polymorphisms (SNPs) located within the E-cadherin gene, at 16q22, we have determined the frequency of allelic imbalance at this proposed tumor suppressor locus in a series of human prostatic carcinoma DNA samples. Whereas results with seven highly polymorphic microsatellite markers flanking the E-cadherin locus confirmed the existence of three separate loci on chromosome 16, at which allelic imbalance increased with increasing loss of tumor cell differentiation, no allelic imbalance within the E-cadherin gene was detected either by single-strand conformational polymorphism analysis or by direct sequencing. We conclude that the loss of E-cadherin function observed in prostate cancer is not a result of allelic deletion. Genes Chromosomes Cancer 27:104-109, 2000.

FGF7/KGF triggers cell transformation and invasion on immortalised human prostatic epithelial PNT1A cells

Fibroblast growth factor 7 (FGF7/KGF) is synthesized exclusively by fibroblasts in normal tissues; it acts as a potent mitogen on epithelial cells, through interaction with the FGF7-specific receptor FGFR2/IIIb. To examine the importance of this growth factor both to prostate physiology and to prostate-cancer progression, we have tested the exogenous effect of FGF7. Thus, by mimicking the paracrine pathway (on proliferation, growth in soft agar and invasion) on the human prostatic epithelial cell line PNT1A positively checked for FGFR2/IIIb expression, FGF7 significantly enhanced cell proliferation at an optimal concentration of 7.5 x 10(-11) M, but no significant invasion or growth in soft agar were observed. To confirm FGF7 properties on human prostatic epithelial cells, we constitutively expressed FGF7 by transfecting PNT1A cells with FGF7-cDNA. The FGF7-transfected clones, PNT1A/ FGF7-T5 and PNT1A/FGF7-T6, were stable and expressed FGF7. Analysis of the FGF7-autocrine loop on the non-tumorigenic epithelial cells PNT1A showed acquired invasive potential in in vitro extracellular-matrix migration assays, specifically inhibited by an FGF7-neutralizing antibody, and over-expressed factors implicated in the migration process: the metalloproteinase MMP-1 and the plasminogen activator uPA. Taken together, these results demonstrate a role for FGF7 in triggering invasion of human prostatic epithelial cells. Furthermore, these FGF7-transfected clones exhibited functional and physiological differences from the original PNT1A cell line: anchorage-independent growth, growth in serum-free media and increased proliferation. These data confirm the oncogenic function of FGF7 in prostate progression potentially acting through paracrine and/or autocrine regulatory pathways.

FGF7/KGF triggers cell transformation and invasion on immortalised human prostatic epithelial PNT1A cells

Fibroblast growth factor 7 (FGF7/KGF) is synthesized exclusively by fibroblasts in normal tissues; it acts as a potent mitogen on epithelial cells, through interaction with the FGF7-specific receptor FGFR2/IIIb. To examine the importance of this growth factor both to prostate physiology and to prostate-cancer progression, we have tested the exogenous effect of FGF7. Thus, by mimicking the paracrine pathway (on proliferation, growth in soft agar and invasion) on the human prostatic epithelial cell line PNT1A positively checked for FGFR2/IIIb expression, FGF7 significantly enhanced cell proliferation at an optimal concentration of 7.5 x 10(-11) M, but no significant invasion or growth in soft agar were observed. To confirm FGF7 properties on human prostatic epithelial cells, we constitutively expressed FGF7 by transfecting PNT1A cells with FGF7-cDNA. The FGF7-transfected clones, PNT1A/ FGF7-T5 and PNT1A/FGF7-T6, were stable and expressed FGF7. Analysis of the FGF7-autocrine loop on the non-tumorigenic epithelial cells PNT1A showed acquired invasive potential in in vitro extracellular-matrix migration assays, specifically inhibited by an FGF7-neutralizing antibody, and over-expressed factors implicated in the migration process: the metalloproteinase MMP-1 and the plasminogen activator uPA. Taken together, these results demonstrate a role for FGF7 in triggering invasion of human prostatic epithelial cells. Furthermore, these FGF7-transfected clones exhibited functional and physiological differences from the original PNT1A cell line: anchorage-independent growth, growth in serum-free media and increased proliferation. These data confirm the oncogenic function of FGF7 in prostate progression potentially acting through paracrine and/or autocrine regulatory pathways.

BCL10 is rarely mutated in human prostate carcinoma, small-cell lung cancer, head and neck tumours, renal carcinoma and sarcomas. MPT Collaborators, St George's Hospital Collaborators

We have used single-strand conformation polymorphism (SSCP) analysis to screen for mutations in the BCL10 gene in 81 primary prostate carcinomas, 20 squamous cell cancers of the head and neck, 15 small-cell lung cancer cell lines, 24 renal carcinoma cell lines and 13 sarcoma cell lines. We failed to find evidence of somatically acquired mutations of the BCL10 gene suggesting that BCL10 does not play a major role in the development of these malignancies.

Expression, crystallization and preliminary X-ray analysis of the E2 transactivation domain from papillomavirus type 16

The N-terminal transactivation domain of the E2 protein from human papillomavirus type 16 has been crystallized by vapour diffusion. Crystals belong to the space group P3121 (or P3221) with unit-cell dimensions a = b = 54.3, c = 155.5 A. There is one molecule per asymmetric unit with a solvent content of 55%. Crystals diffract to at least 2.5 A resolution and complete X-ray data to 3.4 A have been collected on a conventional laboratory source. This 201 amino-acid domain of the E2 protein has been shown to interact functionally with both the HPV E1 protein and at least three cellular transcription factors, to fulfil its role in the control of viral transcription and replication. A knowledge of the structural basis of these multiple interactions should lead to a fuller understanding of the mechanism of action of this key regulator of the HPV life cycle.

Expression patterns of the human papillomavirus type 16 transcription factor E2 in low- and high-grade cervical intraepithelial neoplasia

Specific antibodies against the C-terminus of E2, produced by affinity purification of polyclonal antisera, have been used to identify the cellular populations which express the HPV 16 E2 transcription factor, in a series of formalin-fixed, paraffin-embedded cervical tissues. Cases were selected for both the presence of HPV 16 DNA (confirmed by multiple gene-specific PCR detections) and the presence of multiple grades of cervical intraepithelial neoplasia (CIN). The data indicate that E2 expression is highest in CIN I and in koilocytic lesions. Lower expression was observed in CIN II and little in CIN III lesions. In contrast, there was some restoration of E2 expression in invasive carcinomas, although the intracellular distribution was much more diffuse. The location of E2 expression to the superficial layers of the cervical epithelium, as well as the occurrence of some basal expression in CIN I, suggests that antibodies against HPV 16 E2 could be a useful adjunct to standard histological techniques for the detection of 'at-risk' patients as part of a cervical screening programme.

Predisposing gene for early-onset prostate cancer, localized on chromosome 1q42.2-43

There is genetic predisposition associated with >=10% of all cancer of the prostate (CaP). By means of a genomewide search on a selection of 47 French and German families, parametric and nonparametric linkage (NPL) analysis allowed identification of a locus, on chromosome 1q42.2-43, carrying a putative predisposing gene for CaP (PCaP). The primary localization was confirmed with several markers, by use of three different genetic models. We obtained a maximum two-point LOD score of 2.7 with marker D1S2785. Multipoint parametric and NPL analysis yielded maximum HLOD and NPL scores of 2.2 and 3.1, respectively, with an associated P value of . 001. Homogeneity analysis with multipoint LOD scores gave an estimate of the proportion of families with linkage to this locus of 50%, with a likelihood ratio of 157/1 in favor of heterogeneity. Furthermore, the 9/47 families with early-onset CaP at age <60 years gave multipoint LOD and NPL scores of 3.31 and 3.32, respectively, with P = .001.

Characterization of the interactions of human papillomavirus type 16 E6 with p53 and E6-associated protein in insect and human cells

Human papillomavirus (HPV) 16 E6 induces the degradation of the tumour suppressor protein p53 by the ubiquitin-dependent proteolysis pathway. In vitro, this process involves the formation of a trimolecular complex between E6, p53 and a cellular protein E6-associated protein (E6-AP). However, an analysis of their potential interactions in vivo has not been carried out. We have established a model for the expression and analysis of the interactions of these three proteins in insect cells, a eukaryotic system where potentially crucial modifications of the proteins will occur. In baculovirus-infected cells the degradation of p53 can occur. However, p53 is only degraded early in the infectious cycle due to a lack of ATP at later times. Consequently, substantial quantities of material can be produced in this system for further analysis. Evidence is also provided that, in vivo, E6 can interact with p53 in the absence of E6-AP and that E6-AP can interact with p53 in the absence of E6. Furthermore, analysis of the subcellular localization of the proteins using both biochemical fractionation and indirect immunofluorescence suggests that the degradation of p53 occurs in the perinuclear region of the cell.

Precise microdissection of human prostate cancers reveals genotypic heterogeneity

To determine the incidence of genetic heterogeneity in primary prostate cancer, we have microdissected 125 tumor and mesenchymal foci from 18 patient biopsies and analyzed the DNA for loss of heterozygosity using PCR microsatellite markers. In 100% of patients with genetic lesions on chromosome 8p, there was evidence for intratumoral genetic heterogeneity. There was also a low but significant incidence of loss of heterozygosity in mesenchymal tissue. Our results show that phenotypically similar tumor foci can have different genotypes and provide evidence for the multifocality of tumor development in the prostate.

Androgens are not a direct requirement for the proliferation of human prostatic epithelium in vitro

The androgen receptor pathway is known to be a key regulator of growth in the normal and pathological prostate. However, the precise mechanisms of this signaling pathway with respect to the different cellular compartments of the prostate remain largely unknown. We have used a primary culture system to grow human prostatic epithelial cells of normal, benign, tumor and metastatic origin, as well as immortalized human prostatic epithelial cell lines, to demonstrate the absence of a direct or indirect effect of androgens on cellular proliferation in vitro. In parallel to this observed androgen independence for growth, all cell systems lost significant expression of androgen receptor, prostate-specific antigen and prostatic acid phosphatase. Since the androgen receptor is expressed in the epithelium in situ, our results suggest that the androgen effect on epithelial cells may be one of prostatic differentiation rather than proliferation, and that the androgen receptor/growth factor pathway acts through mesenchymal-epithelial interactions.

Molecular analysis of the interaction between HPV type 16 E6 and human E6-associated protein

The complex formed between the human papillomavirus type 16 E6 protein and human E6-associated protein, which combine to ubiquitylate and degrade p53, has been studied by chemical crosslinking. Analysis of the interactions of proteins purified from Escherichia coli as well as proteins expressed in insect cells indicates that, while E6 has the capacity to form dimers, E6 and E6-associated protein interact as two monomers to form a heterologous dimer.

Constitutive expression of FGF2/bFGF in non-tumorigenic human prostatic epithelial cells results in the acquisition of a partial neoplastic phenotype

Fibroblast growth factor 2 (FGF2), also known as basic fibroblast growth factor (bFGF), belongs to the FGF family, which consists of at least 9 closely related members. FGF2 is a potent mitogen for fibroblasts derived from normal prostate and, to a lesser extent, for prostatic epithelial cells. Its role in the physiology of the normal prostate seems to be limited to stromal cells, whereas in prostate cancer FGF2 may also have an autocrine/paracrine effect on epithelial cells. In order to better understand the effects of FGF2 on the prostatic epithelium, especially its role in the progression of prostate cancer by establishing an autocrine-stimulation loop, we transfected FGF2 cDNA into a human prostatic epithelial cell line, PNT1A, immortalized with SV40 large-T antigen. This cell line is non-tumorigenic and expresses a high-affinity FGF2 receptor, FGFR1/flg. We characterized 3 independent FGF2-transfected clones and found that the establishment of an FGF2 autocrine loop on these cells led to (i) serum-independent growth, (ii) increased proliferation and (iii) anchorage-independent growth. Such results argue in favor of the possible action of FGF2 on progression of prostate cancer via an FGF2 autocrine loop on epithelial cells.

Analysis of prostate tissue DNA for the presence of human papillomavirus by polymerase chain reaction, cloning, and automated sequencing

We have analysed the DNA from 24 prostate tissue biopsies, spanning a range of Gleason grading from benign to grade 5 and mixed randomly with cervical cancer samples of known human papillomavirus (HPV) status, for the prevalence of HPV DNA, in a double-blind study to ensure complete objectivity. Polymerase chain reactions (PCR) were performed using general E1 open reading frame primers for HPV under low stringency conditions, in addition to reactions containing primers specific for HPV16, E2, and E6 open reading frames under higher, more stringent PCR conditions. The presence of cellular DNA was verified by the use of primers for hypoxanthine guanine phosphoribosyl transferase. DNA bands were not detected in the prostate biopsies using the HPV16-specific primers under high-stringency PCR conditions, however a predominant band in the 400 bp region was observed in 15 of the prostate biopsies using the general primers and the low annealing temperature of 40 degrees C. This fragment was excised and cloned into the pT7 blue vector and the sequence of the insert determined. Although the cloned sequences initiated and terminated with the two authentic PCR primers, they did not contain a significant HPV-related open reading frame. Our results indicate that HPV type 16 and closely related types, as detected by the general primer pair, are unlikely initiators of prostate carcinogenesis within our population.

Co-ordinated changes in expression of cell adhesion molecules in prostate cancer

The expressions of E-cadherin, the integrin subunits beta 1, beta 2, beta 3, CD44 and alpha-catenin were studied in parallel by immunohistochemistry in a series of 40 prostate biopsies comprising one normal, 11 benign prostatic hyperplasia (BPH), and 28 prostatic adenocarcinomas. As reported by others, there was a consistent loss of E-cadherin expression with increasing tumour grade and de-differentiation. However, a significant proportion of losses occurred at earlier grades than previously reported. The parallel nature of this study showed, for the first time in human prostate carcinoma, a reciprocal expression pattern of E-cadherin and beta 1 integrin in the higher grades of prostate cancer. A reciprocal expression pattern was also found for E-cadherin and CD44 between moderately and poorly differentiated tumours. alpha-Catenin expression was downregulated only in those cells which had previously lost E-cadherin expression, and beta 2 and beta 3 integrin were rarely expressed in prostate tumours. A loss of expression of the luminal epithelial specific keratins CK8 and CK18 was also observed in advanced stage, poorly differentiated carcinomas.

Differences in serological IgA responses to recombinant baculovirus-derived human papillomavirus E2 protein in the natural history of cervical neoplasia

Infection with certain types of human papillomavirus (HPV) presents a high risk for the subsequent development of cervical intraepithelial neoplasia (CIN) and cervical carcinoma. Immunological mechanisms are likely to play a role in control of cervical HPV lesions. The HPV E2 protein has roles in virus replication and transcription, and loss of E2 functions may be associated with progression of cervical neoplasia. Accordingly, it is of interest to monitor immune responses to the E2 protein, and previous studies have reported associations between serological reactivity to E2 peptide antigens and cervical neoplasia. In order to investigate serological responses to native, full-length E2 protein, we expressed HPV-16 E2 proteins with and without an N-terminal polyhistidine tag using the baculovirus system. Purified HPV-16 E2 protein was used to develop enzyme-linked immunosorbent assays to detect serological IgG and IgA responses in cervical neoplasia patients and controls. We found that serum IgA levels against the E2 protein were elevated in CIN patients relative to normal control subjects but were not elevated in cervical cancer patients. Moreover, there appeared to be a gradient of response within cervical neoplasia such that the highest antibody levels were seen in lower grades of neoplasia up to CIN 2, whereas lower levels were observed in CIN 3 and still lower levels in cervical carcinoma. These findings suggest that the IgA antibody response to E2 may associate with stage and progression in cervical neoplasia.

A microdissection approach to detect molecular markers during progression of prostate cancer

To investigate the underlying mechanisms of carcinogenesis, we have developed a technique to determine the frequency of genetic changes in prostatic carcinoma tissue. We have demonstrated that at a ratio of between 1:4 and 1:9 mutant-normal alleles, the signal from a mutant TP53 allele is not apparent after polymerase chain reaction (PCR) amplification and further direct sequencing or single-strand conformation polymorphism (SSCP) analysis. To bypass this problem, which is inherent in the heterogeneity of the prostate tissue and of the tumour, we selected areas of graded prostate tumours (Gleason score) from cryosectioned preparations and microdissected these cells (20-100 cells). After anionic resin removal of proteins, PCR amplification of TP53 gene exons 5/6 and SSCP analysis, an abnormal SSCP band shift was observed in suspected tumour cells, compared with microdissected stromal cells used as an internal control, while (1) a crude preparation of tissue DNA carrying the tumour did not show any abnormality and (2) immunostaining by a set of monoclonal antibodies against TP53 protein remained negative. Nucleotide sequence analysis of the different bands confirmed the presence of a mutation in the TP53 gene exon 6 position 13,336 in an abnormal band for one specimen, while no mutation was detected in the normal SSCP band. By targeting recognised tumour cells we can find DNA mutations which are undetectable using the standard technique of whole-tissue DNA extraction, particularly in a heterogeneous tumour such as carcinoma of the prostate.

Characterization of human papillomavirus type 16 E2 protein and subdomains expressed in insect cells

The E2 open reading frame of human papillomavirus type 16 (HPV-16) encodes a DNA-binding protein which modulates papillomavirus transcription and replication. To investigate the biological and biochemical properties of the HPV-16 E2 protein, we have constructed recombinant baculoviruses which express the full-length molecule and individual N- and C-terminal domains in Sf21 insect cells. In this system the full-length E2 protein was phosphorylated and targeted to the insect cell nucleus. A 93 amino acid C-terminal fragment encompassing the DNA binding and dimerization functions of E2 was also translocated to the nucleus but was not modified by phosphorylation. The E2 N-terminal protein accumulated in the insect cell cytoplasm but was not efficiently phosphorylated. The formation of heterodimers between full-length and N-terminally truncated E2 species was observed when Sf21 cells were co-infected with recombinant viruses and when homodimers were mixed in vitro, suggesting that the dimer interface is not sufficiently stable to prevent subunit exchange in vivo. Both homo- and heterodimeric E2 species were able to bind specifically and in any combination to tandem E2 binding sites from the HPV-16 regulatory region. Furthermore, the HPV-16 E2 protein bound to DNA exhibited a distinct susceptibility profile to pronase digestion, potentially contrasting with that reported for BPV-1 E2. These observations suggest that significant structural and functional differences may exist between the BPV/HPV E2 proteins and have implications for understanding E2-dependent regulation of transcription and replication.

A polymerase chain reaction (PCR) investigation of oral verrucae which contain HPV types 2 and 57 by in situ hybridization

The polymerase chain reaction (PCR) and direct DNA sequencing have been used to identify strain variants of HPV types 2a/57 in formalin-fixed sections of human oral verrucae, where the virus had previously been detected by both immunofluorescence and in situ hybridization. By employing type-specific and type-common PCR primers we show that these lesions contain a mixture of viral DNAs which vary by up to 27% in DNA sequence, in a region where the variation between HPV types 2a and 57 is only 4%. The extra discriminatory power of fluorescent sequencing indicates that the lesions may also contain wild-type HPV2a/57 DNA which could provide a helper function for defective viral DNA molecules or indicate a mosaic origin for the lesions.

Human papillomavirus DNA and TP53 mutations in lung cancers from butchers

To investigate whether the high frequency of human papillomavirus infection in butchers may be linked to their higher than average incidence of lung cancer, we have examined lung cancers from 40 butchers and 26 controls for the presence of DNA from both HPV type 7, which is found almost uniquely in hand warts from butchers and fishermen, and for those HPV types associated with laryngeal and genital cancers. No HPV 7, and only a low frequency of HPV DNA was found, suggesting that HPV infection does not make an important contribution to the elevated levels of lung cancer in meat handlers. In addition, the frequency of p53 mutation was shown to be slightly lower than previously reported in lung cancers.

Kinetic and equilibrium binding studies of the human papillomavirus type-16 transcription regulatory protein E2 interacting with core enhancer elements

The human papillomaviruses (HPVs) are a family of DNA viruses which cause benign tumours of the skin and mucosa that infrequently progress to malignant carcinoma. The E2 open reading frame of HPV is thought to encode a papillomavirus-specific transcription factor which also has a role in viral replication. The E2 proteins of all papillomaviruses studied to date have been shown to bind specifically to the common conserved sequence ACC(N)6GGT found at multiple locations in their genomes. In the case of HPV-16, a 'high risk' genital papillomavirus, the E2 protein is thought to negatively regulate expression of the major viral transforming genes E6 and E7, which have been directly implicated in the oncogenic process. However, little information exists concerning the relative or absolute affinities of the native HPV-16 protein for its palindromic recognition sequences; moreover, interpretation of any transcription or replication phenomena attributed to this protein is more complicated in the absence of such data. Here we describe the overexpression, purification and characterisation of the C-terminal 89 amino acids of the protein encompassing the DNA binding/dimerisation domain. We show that the recombinant protein purified from E.coli by a combination of non-group-specific chromatography steps retains high biological activity and is able to bind to all sites in the HPV-16 genome with high affinity (approximately 8 x 10(-11) M). In addition, kinetic studies show that the E2-DNA complexes are very stable, with half-lives ranging from 2.15 to greater than 240 min, and that nucleotides internal and external to the conserved palindrome appear to influence stability.

Immunocytochemical comparison of cultured normal epithelial prostatic cells with prostatic tissue sections

By analyzing a culture system of human prostatic epithelial cells (HPEC) and human prostatic fibroblasts (HPF) for expression of several determinants by immunocytochemistry, we have shown that long-term cultures are able to preserve the phenotypic characteristics of the normal tissue from which they are derived. The cytoskeletal elements, prostate-specific proteins, and steroid receptor profiles were compared to those of prostatic epithelium and stroma in situ. When cultured in low serum and low calcium medium, the adult HPEC grew as two layers of cells, the upper one of which retained the differentiation characteristics observed in the luminal fraction of normal prostatic epithelium. This cell type is the likely origin of prostatic neoplasia, with expression of CK8, 18, and 19 but not CK14. Androgen receptors, prostatic-specific antigen, and prostatic acid phosphatase are also expressed in vitro but at lower level than in situ. The lower cell layer expressed most of the same determinants but at a much lower level, suggestive of a stem-cell type. The HPF cultured in RPMI serum supplemented media retained the stromal pattern of the cells observed in situ. Culture systems which conserve the characteristics of their normal counterparts in vivo should provide useful models for studying in vitro genetic and epigenetic factors associated with differentiation and proliferation, but also with tumorigenic progression in the prostatic gland.

Butchers' warts: no evidence for person to person transmission of HPV7

The distribution of warts due to HPV7 in workers in six abattoirs and 103 retail and wholesale butcheries has been studied to determine whether the high prevalence of HPV7 in the meat trade is the result of enhanced person to person transmission, or whether it is a ubiquitous virus which is activated by an unknown factor in meat. Warts were detected in 164 of 486 men. Scrapings were taken from 156 men, and HPV DNA was found in 112 samples, 74 of which contained HPV7. HPV7 was found in 36 workplaces, and there was no evidence of clustering of cases, as would be expected if person to person transmission was occurring in the workplace. This suggests that HPV7 is widely distributed in the community, but only causes clinical disease under specific conditions. We suggest that some unknown factor in meat enhances viral replication.