Expression of Fibroblast Growth Factors (FGFs) and FGF Receptors in Human Prostate

Alternative splicing of fibroblast growth factor receptors in human prostate cancer

BACKGROUND

Fibroblast growth factors (FGFs) are known to play an important role in the growth of normal prostatic epithelial cells and may promote proliferation of neoplastic prostatic epithelial cells via autocrine or paracrine mechanisms. The affinity of FGFs for FGF receptors 1-3 is critically dependent on an alternative splicing event involving the coding region for the carboxy terminal portion of the third extracellular immunoglobulin-like domain that leads to two different isoforms of each receptor (IIIb and IIIc). We therefore sought to determine whether changes in alternative splicing of FGF receptors occur in human prostate cancer.

METHODS

RNAs from normal prostate and clinically localized or metastatic prostate cancers were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR) followed by digestion of products with restriction enzymes specific for each FGF receptor isoform and quantitation of the relative amounts of each isoform after electrophoresis. For FGFR-2, this was correlated with immunohistochemistry to determine the localization of the protein product.

RESULTS

FGFR-1 is expressed exclusively as the IIIc isoform in prostate cancer while FGFR-3 is expressed predominantly as the IIIb isoform, similar to the expression pattern in normal prostatic epithelial cells. In contrast, there was variable expression of the FGFR-2 IIIb and IIIc isoforms. In the majority of cases the FGFR-2 IIIb isoform was the predominant or exclusive isoform expressed, similar to normal epithelial cells, but in a subset of cases the IIIc isoform was increased, indicating a change in alternative splicing of FGFR-2 in some cases.

CONCLUSIONS

In most cases of prostate cancer there are no changes in alternative splicing of FGF receptors, but in a subgroup there is increased expression of the FGFR-2 IIIc isoform. Given that the affinity of FGFs is highly dependent on the isoform of FGF receptor expressed, this information is critical in understanding the effects of FGFs on prostate cancer cells in vivo.

Fibroblast growth factor 2 activation of stromal cell vascular endothelial growth factor expression and angiogenesis

Angiogenesis is a key component of human cancer progression and metastasis. In an effort to recapitulate early events in tumor-induced angiogenesis, we have employed a subcutaneous Matrigel implant model using immunodeficient mice as hosts. Matrigel-containing fibroblast growth factor 2 (FGF-2; 1.2 microg/ml) induced stromal cell infiltration into the Matrigel/skin interface within 4 days and maximal neovascularization at 7 days. Cells staining positive for the endothelial cell marker, platelet-endothelial cell adhesion molecule 1 (PECAM-1), were present in neovessels and in isolated cells within the Matrigel matrix. Immunohistochemical analysis revealed high levels of vascular endothelial growth factor (VEGF) deposited in the stromal interface present only in the FGF-2-containing but not in control Matrigel implants. VEGF expression was confirmed with in situ hybridization. High VEGF mRNA levels were observed in the infiltrating stromal cells but not in endothelial or endothelial precursors as defined by PECAM-1 staining. In vitro analysis of FGF-2-treated embryonic fibroblasts, Balb/c 3T3 cells, showed an induction of VEGF transcription, mRNA synthesis, and protein secretion as defined by transcriptional reporter, Northern blot, and ELISA assays. The FGF-2-induced VEGF expression was not dependent on select matrix adherence or signaling components because VEGF mRNA expression induced by FGF-2 was equally activated on serum, basement membrane, and fibronectin matrix substrates. Systemic application of anti-VEGF antibodies significantly repressed FGF-2-induced angiogenesis over control antibody by 88% (p < 0.001). These data support an FGF-2 angiogenic model that is dependent on endothelial cell activation, stromal cell infiltration, and VEGF expression by the infiltrating stromal cell population.

Aging of the male reproductive system

Reproductive and sexual physiology, changes in body composition and mental performance in the aging male cannot simply be reduced to presumptive hypogonadism defined by low androgen serum levels or by decreasing levels of growth hormone (GH) and melatonin. Morphological changes in organs at different regulatory levels of hormonal networks governing, for example reproduction, such as diminished hypothalamic pulse generator mass, focal degeneration and loss of Leydig cells in testicular tissue, lead to diminished reserve capacities in production and to loss of coordinated pulsatile release of hypothalamic neuropeptides (e.g. gonadotropin releasing hormone, GnRH) and consequently diminished release of pituitary protein and glycoprotein hormones and testicular steroid hormones. Owing to presumptive alterations in feedback sensitivity, decreased testosterone levels do not necessarily upregulate pituitary LH secretion. Alternatively, increased serum levels of LH and FSH can be observed in old men either because of primary hypogonadism or to decreased hypothalamic opioid tone. In general, endocrine functions are sufficient to maintain fertility in elderly men because, except for sperm motility, quantitative and qualitative functional semen parameters are apparently not affected by age. Nevertheless, reduced endocrine and organic functions might become critical at different levels, with high inter-individual variability, of the hypothalamo/pituitary/gonadal-axis. One of the most intriguing organic manifestations of male aging is benign prostatic hyperplasia (BPH), the pathologic prevalence of which closely matches age. Age-associated changes in the endocrine system and in local networks of epithelial, stromal and luminal factors may play important roles in BPH development.

Expression of fibroblast growth factor (FGF)-8 isoforms and FGF receptors in human ovarian tumors

FGF-8 is a mitogenic growth factor, which is widely expressed during embryonic development but only at a very low level in adult tissues. Alternative splicing of the human FGF-8 gene potentially allows coding for 4 protein isoforms (a, b, e, f), which differ in their transforming capacity. The FGF-8 isoforms preferentially activate the receptors FGFR1IIIc, FGFR2IIIc, FGFR3IIIc and FGFR4. FGF-8 is over-expressed in human breast and prostate cancers. Expression has also been found in RT-PCR studies of human ovarian and testicular cancers. The present study was undertaken to examine which FGF-8 isoforms are expressed in ovarian cancer and whether FGF-8 receptors are also expressed. Specimens from 5 normal human ovaries and 51 ovarian tumors (1 benign tumor, 8 borderline malignancies, 42 malignant tumors of different histopathological types) were studied by RT-PCR and immunohistochemistry. FGF-8 isoform b was expressed in all ovarian tumors and in all 7 ovarian-cancer cell lines studied. Isoform a was co-expressed in 9 malignant ovarian tumors. FGF-8 mRNA was not detected by RT-PCR of 3 normal ovary samples. Immunohistochemical staining localized FGF-8 protein to cancer cells. In general, the increased intensity of FGF-8 staining was associated with loss of differentiation within the tumors (Bowker's test, p = 0.37). FGF-8 staining of surface epithelium observed on 2 normal ovaries was very faint. RT-PCR showed that FGFR1IIIc, FGFR2IIIc and FGFR4 were the FGF-8 receptors expressed in normal ovaries and in ovarian tumors. FGF-8 receptor immunoreactivity was preferentially found in normal ovary surface epithelium and tumor cells but also in some stromal cells. Collectively, our results show that ovarian cancers of a wide variety of histological types expressing receptors for FGF-8 have acquired the capacity of expressing FGF-8. This suggests that FGF-8 has an important role in ovarian tumorigenesis.

Cultured stromal cells: an in vitro model of prostatic mesenchymal biology

BACKGROUND

Initial efforts to develop in vitro models to study prostatic biology focused on the culture and characterization of epithelial cells. Recently, attention has turned towards inclusion of stromal cells in experimental systems.

METHODS

Improved methods to isolate and culture stromal cells have been developed. An array of markers are employed to characterize subtypes of stromal cells, with particular interest in smooth muscle differentiation.

RESULTS

Defined, serum-free media are available for certain experimental applications. Conditions that promote smooth muscle differentiation have been identified. Investigators have characterized hormonal and peptide factors that regulate the growth of prostatic stromal cells, and have also described paracrine factors produced by stromal cells that influence epithelial biology.

CONCLUSIONS

Prostatic stromal-cell cultures are now widely employed by a large number of investigators for a diverse array of experimental purposes. While further refinement is required to obtain model systems that fully mimic in vivo processes, the availability of stromal- and epithelial-cell cultures provides a valuable resource for studying normal prostatic biology as well as benign prostatic hyperplasia (BPH) and cancer.

Fibroblast growth factor receptor-2 mutation analysis in human prostate cancer

OBJECTIVE

To assess whether mutations in the hot-spots of the fibroblast growth factor (FGF) receptor-2 gene (FGFR2, exons encoding the IIIa, IIIb, IIIc and transmembrane domain, TMD) are associated with the development of prostate cancer, as the IIIb variant is the specific receptor for FGF7/KGF, an androgen-inducible paracrine factor regulating prostatic growth. Materials and methods Single-strand conformational polymorphism-polymerase chain reaction (SSCP-PCR) and cycle-sequencing analysis were used to screen FGFR2 mutations in 30 patients with prostate cancer; corresponding blood samples were analysed from 11 of the patients. The human prostate cell lines, LNCaP, PC3, DU145, PNT1A and PNT1B were also examined. In addition, 10 foci of invasive cancer from three patients who underwent radical prostatectomy were also assessed.

RESULTS

Positive controls containing FGFR2 mutations (Crouzon disease and Pfieffer syndrome) were confirmed by SSCP-PCR and sequencing. Analysis of all prostate tumour samples and prostate-derived cell lines revealed no polymorphisms or mutations in the IIIa, IIIb, IIIc and TMD regions of FGFR2.

CONCLUSION

FGFR2 mutations in the-FGF binding domain and the TMD are not frequent events in human prostate cancer.

FGF-10 is expressed at low levels in the human prostate

BACKGROUND

Fibroblast growth factors (FGFs) are known to play an important role in the growth of normal prostatic epithelial cells. FGF-10 is a secreted growth factor that binds to FGF receptor-2 IIIb, which is expressed in prostatic epithelial cells and thus can potentially act as a growth factor for these cells. Prior work has indicated that FGF10 may play an important role in the development of the rat prostate, but its role in the adult human prostate is unclear.

METHODS

Expression of FGF10 in human prostate tissue and primary cultures of prostatic epithelial and stromal cells was assessed by reverse-transcriptase PCR (RT-PCR) and Northern blotting. Growth response to FGF10 was assessed by the addition of recombinant FGF-10 to primary cultures of prostatic epithelial and stromal cells.

RESULTS

FGF10 is expressed at levels detectable by RT-PCR and can act as a growth factor for prostatic epithelial cells, but is not active as a growth factor for stromal cells. However, FGF10 is expressed at extremely low levels relative to FGF7, which has a similar biological activity.

CONCLUSIONS

While FGF10 may play a role in prostatic development, it is unlikely to play a major role in prostate growth in normal or hyperplastic adult human prostate, due to its extremely low expression compared to FGF7.

Effect of a vitamin D3 analogue on keratinocyte growth factor-induced cell proliferation in benign prostate hyperplasia

Prostate enlargement and function is under the dual control of androgens and intraprostatic growth factors. They regulate, in concert, prostate cell proliferation and apoptosis. An increased signaling of both growth factors and androgens are supposed to underlie benign prostate hyperplasia (BPH), one of the more common disorders of the aging male. Since, in clinical practice, androgen ablation resulted in a rather limited decrease in prostate volume, therapeutic strategies targeting intraprostatic growth factors are emerging. The activated form of vitamin D, vitamin D3, and some of its analogues have been described as potent regulators of cell growth and differentiation. In this study, we report the effects of one of these vitamin D3 analogues, 1,25-dihydroxy-16ene-23yne D3, or analogue (V), on the fate of isolated epithelial cells derived from patients with BPH. We essentially found that analogue (V), as well as vitamin D3, inhibited BPH cell proliferation and counteracted the mitogenic activity of a potent growth factor for BPH cells, such as keratinocyte growth factor (KGF). Moreover, analogue (V) induced bcl-2 protein expression, intracellular calcium mobilization, and apoptosis in both unstimulated and KGF-stimulated BPH cells. Since a short-term (5-min) incubation with analogue (V) reduced the KGF-induced tyrosine phosphorylation of a 120-kDA protein, corresponding to the KGF receptor, a rapid and direct cross-talk between these two molecules is suggested. Such a rapid effect of analogue (V), together with the transient induction of intracellular calcium waves, seems to indicate the partial involvement of a membrane, nongenomic receptor for vitamin D3. In conclusion, we demonstrated the antiproliferative and proapoptotic effect of analogue (V) in BPH cells and speculated on its possible use in the therapy of BPH.

Interleukin-1alpha is a paracrine inducer of FGF7, a key epithelial growth factor in benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is an extremely common disease of older men in which there is benign overgrowth of the prostatic transition zone, leading to obstruction of urine outflow. FGF7, a potent growth factor for prostatic epithelial cells, is increased by threefold in BPH and is correlated with increased epithelial proliferation in this condition. Immunohistochemistry of normal and hyperplastic prostate revealed that FGF7-expressing fibroblastic cells were present in higher numbers near the epithelial acini, implying that epithelial cells may express a factor that induces FGF7 expression by stromal cells. Conditioned medium (CM) from primary cultures of prostatic epithelial cells was capable of inducing a two- to sixfold increase in the expression of FGF7 by primary stromal cultures. Blocking experiments with neutralizing anti-interleukin-1alpha (Il-1alpha) antibodies and IL-1Ra, an Il-1alpha receptor antagonist, show that this inducing activity was due to the presence of Il-1alpha in the epithelial CM. Analysis of normal prostatic peripheral zone and BPH tissue by enzyme-linked immunoabsorption assay reveal that Il-1alpha is present at increased levels in hyperplastic prostate and that levels of Il-1alpha correlate strongly with tissue FGF7 concentration in BPH. Therefore Il-1alpha is produced by prostatic epithelial cells and can induce FGF7, a potent epithelial growth factor, which can in turn lead to further epithelial growth and increased Il-1alpha secretion, thus establishing a double paracrine loop that is functionally equivalent to an autocrine growth loop. This double paracrine loop may play a key role in the abnormal proliferation of the transition zone, which is critical to the pathogenesis of BPH.

Endothelium-derived factors as paracrine mediators of prostate cancer progression

BACKGROUND

Vascular endothelium represents a complex network of cells producing a large number of active substrates affecting physiologic, metabolic, and immunologic properties of the whole organism, as well as particular organs or tissues. The potential influence of endothelium-derived paracrine factors on prostate cancer progression has only begun to be examined.

METHODS

This review summarizes recent literature on endothelium-derived factors, including vasoactive agents, peptide growth factors, cytokines, and colony-stimulating factors, involved in the development and progression of prostate cancer.

RESULTS

Endothelial cells produce an array of active substrates, many of which have been shown to influence prostate cancer growth. Available data demonstrate the positive impact of such molecules as endothelin-1, basic FGF, TGF-beta, IL-6, and IL-8 on prostate cancer progression. Many other endothelium-derived factors NO, IGF, PDGF, IL-1, G-CSF, and GM-CSF (Nitric Oxide, Insulin-Like Growth Factor, Platelet-Derived Growth Factor, Interleukin-1, Granulocyte Colony Stimulating Factor, and Granulocyte-Macrophage Colony Stimulating Factor) are, at best, implicated in prostate cancer growth, and in most cases support cancer progression.

CONCLUSIONS

A better understanding of endothelium-derived factors, as paracrine mediators of prostate carcinogenesis and progression, should aid in the development of novel therapeutic strategies.

Expression and localization of basic fibroblast growth factor in diabetic rat prostate

OBJECTIVE

To assess fibroblast growth factor-2 (FGF2/bFGF), which is important in the development and maintenance of the normal prostate and in the development of human benign prostatic hyperplasia (BPH) and prostatic carcinoma, in an animal model of experimentally induced diabetes. Materials and methods Using Western blotting and immunohistochemical analyses, the expression of FGF2 in prostates from several groups of rats was investigated. Rats had diabetes for 8 or 16 weeks (induced by intravenous injection with 65 mg/kg streptozotocin); rats were also treated with insulin (starting 8 weeks after the induction of diabetes, for 8 weeks), and two further groups acted as age-matched control rats. Immunohistochemical markers for smooth muscle (alpha-actin) and epithelium (cytokeratin) were used to distinguish different cell types in adjacent prostatic sections.

RESULTS

Diabetic rats had smaller prostates and lower serum testosterone levels than their controls; insulin treatment of diabetic rats increased prostatic size and testosterone levels. As shown by Western blotting, diabetes caused greater FGF2 expression than in controls, whereas reverse-transcriptase polymerase chain reaction studies showed similar levels of prostatic FGF-2 mRNA in all groups. Immuno-histochemical studies showed that FGF-2 was expressed in both stromal and epithelial components of the rat prostate. Furthermore, although the expression of FGF2 was higher in epithelial than stromal cells in control prostates, it was distributed uniformly in the diabetic prostate.

CONCLUSION

The differences in the level of expression and pattern of distribution of FGF2 suggests a potential role for FGF2 in the changes observed in prostatic growth in diabetic rats.

Promatrilysin expression is induced by fibroblast growth factors in the prostatic carcinoma cell line LNCaP but not in normal primary prostate epithelial cells

BACKGROUND

It has been determined that prostate cancer cells overexpress the matrix metalloprotease matrilysin (MMP-7), but the factors regulating this expression have not been identified. Fibroblast growth factors (FGF), which are expressed in the prostate, might participate in paracrine regulation of matrilysin expression by prostate cancer cells.

METHODS

We tested the ability of recombinant FGF proteins and prostate fibroblast-conditioned media (PFCM) to induce promatrilysin expression in the prostate carcinoma cell line, LNCaP, and in normal prostate epithelial (PrEC) cells. We also characterized prostate fibroblast FGF expression by reverse transcriptase-polymerase chain reaction (RT-PCR). An inhibitor of FGF receptor activation (SU5402) was used to determine the role of FGF proteins in the induction of promatrilysin expression by PFCM.

RESULTS

Recombinant FGF-1, FGF-2, FGF-9, FGF-10, and PFCM significantly induced promatrilysin expression in LNCaP cells but not in PrEC cells. Prostate fibroblasts express mRNAs for these FGF proteins, and inhibition of LNCaP cell FGF receptors with SU5402 substantially reduced the induction of promatrilysin expression by PFCM.

CONCLUSIONS

Stromally expressed FGF proteins induce promatrilysin expression in a prostate carcinoma cell, and may provide a mechanism for the overexpression of promatrilysin observed in prostate cancer.

aFGF immunoreactivity in prostate cancer and its co-localization with bFGF and FGF8

Fibroblast growth factors (FGFs) have been implicated in the development of numerous malignancies including prostate cancer. In a pilot study it has been shown that FGF8 mRNA is up-regulated in prostate cancer. The aim of the present study was to determine whether aFGF and bFGF were co-expressed with FGF8 in human prostate cancer. Twenty-nine cases of prostate cancer of different histological grades were examined. Immunohistochemical analysis was employed to study aFGF and bFGF expression. In the light of the results, aFGF immunoreactivity was studied in a further 43 cases. aFGF and bFGF immunoreactivity was identified in the cytoplasm of the malignant prostatic epithelium. aFGF was overexpressed in 62/72 (86.1 per cent) cases and bFGF in 19/29 (65.5 per cent). High levels of aFGF immunoreactivity were noted in areas of high-grade prostatic intraepithelial neoplasia (PIN). In this series, aFGF immunoreactivity was most commonly observed and correlated closely with Gleason score and tumour stage ( p=0.007 and 0.007, respectively). Co-localization of aFGF, bFGF, and FGF8 was detected in 9/29 (31.0 per cent) cases. There was a significant correlation between aFGF and FGF8 expression. In conclusion, aFGF, bFGF, and FGF8 are co-localized in human prostate cancer; they may have a synergistic effect in prostate cancer growth and progression.

Immunolocalization of the keratinocyte growth factor in benign and neoplastic human prostate and its relation to androgen receptor

BACKGROUND

Growth and development of the prostate are androgen-dependent. Keratinocyte growth factor (KGF), widely expressed by mesenchymal cells, is thought to act like an andromedin between stroma and epithelium of the prostate. Since KGF has recently emerged as an autocrine mediator in prostate cancer, we investigated the role KGF plays in the human prostate and its relationship to androgen receptor (AR).

METHODS

Normal (n = 13), benign hyperplastic (n = 5), and neoplastic (n = 14) human prostate tissues as well as cultured epithelial and stromal cells were analyzed using polymerase chain reaction (PCR), Western blot analysis, and immunohistochemistry.

RESULTS

Reverse transcriptase polymerase chain reaction and Western blotting showed KGF expression in stromal cultured cells of the normal prostate but not in epithelial cells. Using immunohistochemistry, KGF was found to be localized in fibroblasts and smooth muscle cells, independent of prostate disease. There was KGF expression in epithelial cells of BPH and prostate cancer. Human androgen receptor was uniformly expressed in the same secretory glandular cells that were positive for KGF in BPH and prostate cancer.

CONCLUSIONS

Our results provide evidence that KGF is a stromal-derived mediator, recently shown to act in a paracrine manner in normal prostate but now detected in epithelial cells in prostate cancer and BPH. These findings support the hypothesis that KGF might act as an autocrine factor in prostate cancer and BPH.

Expression of basic fibroblast growth factor and its receptors FGFR1 and FGFR2 in human benign prostatic hyperplasia treated with finasteride

BACKGROUND

The development of benign prostatic hyperplasia (BPH) is an androgen-dependent process which may be mediated by a number of locally produced growth factors. One of these, the basic fibroblast growth factor (bFGF or FGF2), has a mitogenic effect on prostatic stroma. High expression levels of bFGF have been reported in BPH. FGFR1 and FGFR2 receptors, that exhibit affinity for bFGF, have been identified in normal and hyperplastic prostate. Finasteride, a 5alpha-reductase inhibitor, is an effective drug in the treatment of BPH, inducing regressive changes in the prostate of treated patients, even though its mechanisms of action are not yet completely elucidated. This study was designed to assess the effects of finasteride on the expression levels of bFGF, FGFR1, and FGFR2 in patients with BPH.

METHODS

The expression levels of bFGF, FGFR1, and FGFR2 in 9 patients with prostatic hyperplasia treated with finasteride were assessed by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR) analysis of mRNA expression and were compared with those of 9 control patients with untreated BPH.

RESULTS

Immunohistochemistry showed strong bFGF immunoreactivity in the prostatic stroma of untreated patients, this being somewhat weaker in the epithelium. In treated patients, epithelial immunoreactivity was practically negative, and a considerable reduction in stromal immunoreactivity was seen. These findings were also confirmed by RT-PCR. FGFR1 showed a weak immunoreactivity in the stroma and in basal epithelial cells. FGFR1 showed a weak immunoreactivity in the stroma and in basal epithelial cells. FGFR2 exhibited strong stromal immunoreactivity, becoming weaker in the basal epithelium. No differences were seen in the expression of both receptors between the groups of treated and untreated patients.

CONCLUSIONS

A marked reduction in bFGF levels is seen in BPH treated with finasteride in comparison to untreated BPH. In our opinion, finasteride may act as a negative regulator of bFGF expression, counteracting the role of bFGF in the development of BPH.

FGF9 is an autocrine and paracrine prostatic growth factor expressed by prostatic stromal cells

Polypeptide growth factors, including members of the fibroblast growth factor (FGF) family, play an important role in the growth and maintenance of the normal prostate. We have found that FGF9 is expressed at high levels in the normal peripheral and transition zone of the human prostate. Analysis of FGF9 production by primary cultures of prostatic epithelial and stromal cells has shown that FGF9 is produced and secreted by the prostatic stromal cells. Neither of these processes appears to be modulated by androgens. Production of FGF9 by stromal cells in vivo was confirmed by immunohistochemistry. FGF9 is a potent mitogen for both prostatic epithelial and stromal cells in culture and is a more potent mitogen for these cells than either FGF2 or FGF7, two other FGFs expressed in the human prostate. FGF9 is an abundant secreted growth factor that can act as both a paracrine mitogen for epithelial cells and an autocrine mitogen for stromal cells. Western blot analysis of tissue extracts from the normal and hyperplastic transition zone shows that FGF9 is present at two to threefold higher levels in the hyperplastic transition zone. Overexpression of this paracrine and autocrine growth factor may play an important role in the epithelial and stromal proliferation in benign prostatic hyperplasia.

FGF8 over-expression in prostate cancer is associated with decreased patient survival and persists in androgen independent disease

Identification of prostate cancers at high risk of progression is difficult and a better understanding of how peptide growth factors influence cellular function might be useful. Fibroblast growth factors (FGFs) have been implicated in prostate cancer development. FGF8 was identified in the Shionogi mouse mammary carcinoma SC-3 cell line as an androgen-induced mitogen. We tested if FGF8 was over-expressed in human prostate cancer and if its expression correlated with clinical data and outcome. One hundred and six cases of prostate cancer and ten cases of BPH were examined. In situ hybridization was employed to detect FGF8 mRNA expression, which was identified within the malignant prostatic epithelium in 85/106 (80.2%) cases. Increased expression of FGF8 correlated significantly with higher Gleason scores (P=0.0004) and advanced tumour stage (P=0.0016). Using immunohistochemistry, we confirmed over-expression of the FGF8b isoform. Men with tumours which expressed high levels of FGF8 had worse survival (P=0.034), although FGF8 mRNA was not able to provide additional prognostic information in a multivariate analysis. Additionally, FGF8 expression was shown to persist in androgen independent prostate cancer. Using a range of normal adult tissues, FGF8 expression was restricted to neurones and the germinal epithelium in addition to the prostate. In vitro studies demonstrated that in the presence of neutralizing antibody to FGF8b there was significant inhibition of prostate cancer cell growth, confirming the biological significance of FGF8 in prostate carcinogenesis.

Involvement of heparin affin regulatory peptide in human prostate cancer

BACKGROUND

Heparin affin regulatory peptide (HARP) composes, together with midkine (MK), a new family of heparin-binding growth/differentiation factors. Recently, HARP was incriminated in cancer progression, as an angiogenic factor and as a tumor growth factor. In this study, we analyzed the possible involvement of HARP in human prostate cancer (Pca).

METHODS

The localization of HARP protein and its mRNAs in normal prostate (n = 5), benign prostate hyperplasia (BPH) (n = 7), and prostate cancer (Pca) (n = 9) was analyzed by immunohistochemistry and in situ hybridization. The mitogenic activity of this growth factor for prostate epithelial cells was determined with a thymidine incorporation assay. HARP cDNA was transfected into normal prostate epithelial (PNT-1A) cells, and their growth was evaluated by soft-agar growth assay.

RESULTS

We found HARP protein associated with epithelial cells in PCa but not in normal prostate or BPH, while the corresponding mRNAs were located in the stromal compartment. Furthermore, HARP is mitogenic for PNT-1A, LNCaP, and DU-145 cells. Overexpression of the human HARP in PNT-1A transfected cells induced both anchorage-independent growth and growth at low serum concentrations.

CONCLUSIONS

Our results suggest that HARP may act in a paracrine manner from mesenchymal to tumoral epithelial cells, and may play a role in the molecular mechanisms that regulate prostate tumor cell growth.

Prostate stroma: physiology

BACKGROUND

The separate structural and functional activities of the prostatic stroma were only recently discovered and are still poorly understood.

METHODS

This review summarizes recent literature on the structure, and on the angiogenic, contractile, proliferative, and secretory activities mediated by the prostatic stroma and its agents.

RESULTS

The stroma undergirds the acinar epithelium through its fibromuscular substance. Neovascularization of its hypoxic cells, a process driven by cytokines, especially vascular endothelial growth factor, provides fuel for glycolytic empowerment of smooth muscle contraction, growth, and secretion. Signals from the stromal complement of cholinergic and adrenergic fibers, modulated by also-elaborated nitric oxide, provide tight regulation of uroflow. Apparently, autonomic control is independent of that of the powerful endothelin, secreted by the epithelium. Superimposed on these intrinsic elements of prostatic stromal control are the effects of steroid hormones and their effectors.

CONCLUSIONS

The illumination of the stroma's role in prostatic physiology, coupled with advances in knowledge of its pharmacology, should aid in our understanding, management, and prevention of prostatic disease.

Androgen responsiveness of stromal cells of the human prostate: regulation of cell proliferation and keratinocyte growth factor by androgen

PURPOSE

Growth and development of the prostate are androgen dependent and mainly influenced by stromal-epithelial interaction. It is believed that indirect androgenic activation of paracrine factors like keratinocyte growth factor (KGF) in the prostatic stroma influences the growth of epithelial cells. In this study we investigated the role androgen plays in stromal cell growth and stimulation of KGF in the human prostate.

MATERIALS AND METHODS

Stromal cells were derived from explant primary culture of human normal or benign prostatic tissue. The effect of different dihydrotestosterone (DHT) concentrations on cell proliferation was measured using 3[H]thymidine incorporation assay. The effect of DHT on levels of KGF protein was determined by Western blotting. The effect of DHT on levels of KGF gene expression was measured by various cycles of polymerase-chain-reaction (PCR) and multiplex PCR.

RESULTS

Characterization of stromal cells showed epithelial cells less than 9.5% in all passages. DHT stimulated human prostate stromal cells in a dose dependent fashion over a concentration range of 0.001-10 nM. Immunocytochemical evaluation of KGF after DHT exposure showed a higher staining intensity. Relative quantitation of Western blotting showed a 1.93-fold increase in KGF protein in the androgen treated stromal cells. At 1 nM DHT conventional and multiplex PCR revealed a significant stimulation of the KGF mRNA expression.

CONCLUSIONS

These data show for the first time that androgen stimulates cell proliferation as well as KGF protein and gene expression in human prostate stromal cells. This supports the hypothesis that androgen-induced stromal-derived KGF stimulates prostate epithelial cell growth.