Mesenchymal-epithelial interactions and transforming growth factor-beta 1 expression during normal and abnormal prostatic growth

Association between gut microbiota and benign prostatic hyperplasia: a two-sample mendelian randomization study

Background

Recent researches have shown a correlation between the gut microbiota (GM) and various diseases. However, it remains uncertain whether the relationship between GM and benign prostatic hyperplasia (BPH) is causal.

Methods

We carried out a two-sample Mendelian randomization (MR) analysis, utilizing data from the most extensive GM-focused genome-wide association study by the MiBioGen consortium, with a sample size of 13,266. Data for BPH, encompassing 26,358 cases and 110,070 controls, were obtained from the R8 release of the FinnGen consortium. We employed multiple techniques, such as inverse variance weighted (IVW), constrained maximum likelihood and model averaging methods, maximum likelihood, MR-Pleiotropy RESidual Sum and Outlier (MRPRESSO),MR-Egger, and weighted median methods, to investigate the causal relationship between GM and BPH. To evaluate the heterogeneity among the instrumental variables, Cochran's Q statistics were employed. Additionally, the presence of horizontal pleiotropy was assessed through the application of both MR-Egger and MR-PRESSO tests. The direction of causality was scrutinized for robustness using the MR-Steiger directionality test. A reverse MR analysis examined the GM previously linked to BPH through a causal relationship in the forward MR assessment.

Results

According to the analysis conducted using IVW,Eisenbergiella (odds ratio [OR]=0.92, 95% confidence interval [CI]: 0.85-0.99,P=0.022) and Ruminococcaceae (UCG009) (OR=0.88, 95% CI: 0.79-0.99, P=0.027) were found to reduce the risk of BPH, while Escherichia shigella (OR=1.19, 95% CI: 1.05-1.36, P=0.0082) appeared to increase it. The subsequent reverse MR analysis revealed that the three GM were not significantly influenced by BPH, and there was no noticeable heterogeneity or horizontal pleiotropy among the instrumental variables.Conclusion: These results indicated a causal relationship between Eisenbergiella, Ruminococcaceae (UCG009), and Escherichia shigella and BPH. Further randomized controlled trials are needed to explore more comprehensively the roles and operational mechanisms of these GM in relation to BPH.

Is transforming growth factor-β signaling activated in human hypertrophied prostate treated by 5-alpha reductase inhibitor?

Background and Aim. It is well known that androgen deprivation relates to penile fibrosis, so we hypothesize that long-term treatment with 5-alphareductase inhibitors (5ARIs) may increase the risk of fibrosis of prostate. Patients and Methods. Thirty-two BPH patients who underwent transurethral resection of the prostate were enrolled. The patients were divided into two groups: group one, 16 patients underwent TURP who had been treated with tamsulosin for 2 years; group two, 16 patients underwent TURP who had been treated with combination of tamsulosin and dutasteride for at least 1 year. We evaluated the expressions of nNOS, iNOS, eNOS, TGF-β1, TGF-β2, phosphorylated-Smad2/3 (p-Smad2/3), E-cadherin, N-cadherin, and α-smooth muscle actin in the resected prostate tissues by western blotting, and the TGF-β concentration was determined by ELISA kit. Results. The expressions of 3 isoforms of NOS were significantly increased in group 2 except of eNOS in lateral prostate, and the expressions of TGF-β1, TGF-β2, and p-Smad2/3 increased about 2-fold compared with group 1. In group 2, the E-cadherin expression decreased while N-cadherin expression increased significantly. Conclusions. The overexpression of nNOS may contribute to prostate smooth muscle relaxation; however, long-time treatment with 5 ARI increases the risk of fibrosis of prostate.

Action, localization and structure-function relationship of growth factors and their receptors in the prostate

Whereas the direct action of sex steroids, namely of androgens, on prostate cell division was questioned as early as in the 1970s, and remains so, the interest in prostatic growth factors (GFs) is rather recent but has expanded tremendously in the last five years. This lag period can be partly explained by the fact that, at the time, androgen receptors had just been discovered, and newly developed hormonal regimens or strategies to treat patients with prostate carcinoma (PCa) or epithelioma had generated great enthusiasm and hopes in the medical and scientific community. Another point to consider was the difficulty in maintaining prostate tissues in organ cultures and the relative novelty of culturing prostate epithelial cells in monolayers. Failures of sex steroids to elicit a direct positive response on prostate cell divisionin vitro, as seenin vivo, were interpreted as resulting from inappropriate models or culture conditions. However, the increasing number of reports confirming the lack of mitogenic activity of sex steroidsin vitro, coupled with the powerful mitogenic activity of GFs displayed in other systems, the discovery of GF receptors (GF-Rs), and the elucidation of their signalling pathways showing sex steroid receptors as potential substrates of GF-activated protein kinases gradually led to an increased interest in the putative role of GFs in prostate physiopathology. Of utmost importance was the recognition that hormone refractiveness was responsible for PCa progression, and for the poor outcome of patients with advanced disease under endocrine therapies. This problem remains a major issue and it raises several key questions that need to be solved at the fundamental and clinical levels.

Opposing actions of TGFbeta1 and FGF2 on growth, differentiation and extracellular matrix accumulation in prostatic stromal cells

TGFbeta 1 and FGF2 are autocrine growth factors in prostatic stroma and are elevated in benign prostatic hyperplasia (BPH), a disease characterized by enlargement of the stromal compartment of the prostate. TGFbeta1 has a biphasic effect on proliferation of prostatic stromal cells, inducing proliferation at low doses (< 1 ng/ml), but inhibiting growth above 1 ng/ml. This study investigated the role of TGFP 1 and FGF2 on growth factor bioavailability and extracellular matrix (ECM) accumulation synthesis in cultured prostatic stromal cells. Real-Time-PCR showed that TGFbeta1 expression is auto-inductive, whereas FGF2 is auto-repressive. FGF2 also induced TGFbeta1 secretion in the absence of increased TGFbeta1 mRNA expression. TGFbeta1 and FGF2 have opposing actions on Type 1 collagen expression, a finding confirmed by Western blotting. The bioavailability of TGFbeta1 regulated by FGF2 may represent part of a negative feedback mechanism controlling stromal growth, differentiation and ECM. Dysregulation of this pathway in favour of TGFbeta1 bioactivity may exacerbate BPH.

Serum response factor, its cofactors, and epithelial-mesenchymal signaling in urinary bladder smooth muscle formation

Little is known about the mechanism of bladder smooth muscle differentiation. We hypothesize that epithelial-mesenchymal signaling induces the expression of smooth muscle proteins in bladder mesenchyme resulting in smooth muscle differentiation. We confirmed that smooth muscle differentiation in the mouse urinary bladder occurs first at gestational day 14 (E14) based upon immunohistochemical localization of smooth muscle alpha-actin (SMAA). To investigate murine bladder smooth muscle differentiation and epithlelial-mesenchymal signaling in the developing bladder, we analyzed gene expression profiles of intact embryonic murine bladders and separated epithelial and mesenchymal components at embryonic days E13, E14, E15, E16, and postnatal day 1 (P1). Using cDNA microarray, we identified regulators of vascular smooth muscle differentiation in bladder mesenchyme, including serum response factor (SRF) and its cofactors, ELK1 and SRF accessory protein (SAP)1, as well as two SRF-associated pathways, angiotension receptor II and transforming growth factor- beta2. Immunohistochemistry showed diffuse expression of SRF in the bladder at E12 with localization of expression to the peripheral mesenchyme at E13 and E14. Our results suggest that bladder smooth muscle differentiation may share a similar gene expression program as occurs during vascular smooth muscle differentiation. The unique structure of the urinary bladder makes it an ideal model for studies of smooth muscle differentiation and epithelial-mesenchymal signaling.

Antiandrogen-like actions of an antioxidant on survivin, Bcl-2 and PSA in human prostate cancer cells

BACKGROUND

Androgens, while essential for prostate gland development, have been postulated to contribute to carcinogenesis, and antioxidants have been postulated to suppress prostate cancer development. We theorized that antioxidants might suppress prostate cancer cell growth by blocking androgen effects on cell survival. This hypothesis was tested by in vitro studies conducted in ALVA-101, an androgen responsive human prostate cancer cell line.

METHODS

ALVA-101 was cultured with or without testosterone (T, 10(-12) M) and pyrrolidinedithiocarbamate (PDTC, 10 microg/mL). Cell Titer 96 AQ, electrophoretic mobility shift assay (EMSA), reverse transcription-polymerase chain reaction (RT-PCR), Northern and Western blot were used to quantify the cell growth, nuclear factor-kappa B (NF-kappaB) activity, mRNAs of survivin, Bcl-2, androgen receptor (AR) and prostate specific antigen (PSA), and proteins of AR and survivin.

RESULTS

PDTC suppressed EMSA of NF-kappaB and significantly decreased (p < 0.05) T's stimulatory effects on cell growth, mRNAs of survivin, Bcl-2, AR and PSA and synthesis of proteins of AR and survivin. Antisense to both survivin and Bcl-2 suppressed cell growth.

CONCLUSIONS

PDTC, a potent inducer of apoptosis, exerts antiandrogen-like action by reducing AR protein and reversing the stimulatory effects of androgen on potent inhibitors of apoptosis.

Prostate Development and Carcinogenesis

The process involved in the development and carcinogenesis of the prostate gland is complex. During early prostate development, the androgenic hormone from embryonic testicles is required for ductal formation, growth, and branching morphogenesis of the prostate gland. From this early stage, interactions between the epithelium and mesenchyme become firmly established through paracrine influence (i.e., growth factors) from mesenchyme (stroma), in response to testosterone, acting on epithelium to stimulate its proliferation, morphogenetic differentiation, and function. In return, the epithelium also exerts its paracrine effects on mesenchyme by regulating the differentiation and specific organizational pattern of its stromal smooth muscle. In a normal adult prostate, the maintenance of normal glandular structure and function is dependent not only on the constant presence of testosterone, but also on a normal intact and stable stroma. This chapter will concentrate first on factors involved in the normal development of the prostate gland and then on the aberrant changes in the homeostatic balance arising either from within (i.e., mutations) or outside (i.e., changes in hormonal balance) that result in derangements of the prostate gland. Finally, environmental and genetic factors that lead to prostate carcinogenesis including activation of oncogenes and mutations of tumor suppressor genes are also discussed.

Testosterone is a potential augmentor of antioxidant-induced apoptosis in human prostate cancer cells

We have investigated the effect of antioxidant-induced apoptosis in human prostate cancer cell lines that is augmented by testosterone (T). In this study, DU-145 (androgen unresponsive), ALVA-101 (partially androgen responsive), and LNCaP (androgen responsive) were grown in tissue culture with RPMI 1640 medium, 5-10% fetal bovine serum (FBS), antibiotics and 5% CO2. Treatment with 2.5-20 microg/ml of PDTC significantly (P < 0.05, n = 6) lowered cell growth in all three cells 2-60% following treatment for 1-7 days. T (10(-12) M) alone enhances cell growth in androgen responsive cells. In contrast, the combination of PDTC and T significantly (P < 0.05, n = 6) augmented the PDTC induction of apoptosis in the androgen responsive cells, (ALVA-101 and LNCaP), but not in the androgen unresponsive cells (DU-145). PDTC reduced the nuclear NF-KB, as determined with an electrophoretic mobility shift assay (EMSA), to 50% of the control in LNCaP cells, 65% in ALVA-101 cells and 45% in DU-145 cells, but the combination of PDTC and T was not more potent than PDTC alone in any of the cell lines. PDTC suppressed both the AR mRNA and protein expression and reversed the stimulatory effect of T on androgen receptor (AR) protein synthesis in LNCaP and AVLA-101 cells. In conclusion, PDTC is a potent growth inhibitor and an inducer of apoptosis in human prostate cancer cells by reducing nuclear NF-kappaB and AR protein expression. PDTCs suppression of AR synthesis and nuclear NF-kappaB in response to T may contribute to its enhancement of apoptosis observed with T and PDTC compared to PDTC alone.

Prostate tumor-stroma interaction: molecular mechanisms and opportunities for therapeutic targeting

Maintenance of cell and tissue homeostasis is dependent upon the dynamic balance of cell proliferation, differentiation, and apoptosis through interactions between cells and their microenvironment. The unique prostatic cellular phenotypes are induced and maintained by interaction between epithelium and adjacent stroma through intimate intercellular signaling pathways. In this article, we summarize current advances in the tumor-stroma interaction and its biologic and therapeutic implications. We specifically emphasize current studies of the possible factors driving the "vicious cycle" between stroma and emerging prostate tumor epithelial cells that may be responsible for carcinogenesis and metastasis to bone. Stroma responds both genotypically and phenotypically to tumor epithelium upon co-culture under 3-D conditions. Likewise, the emerging carcinoma responds to stromal signals that drive progression to malignancy. A vicious cycle mediated by soluble and insoluble molecules secreted by tumor cells and stroma appear be the critical factors supporting and sustaining tumor colonization in bone. Co-targeting tumor and stroma with therapeutic agents has yielded promising results both in pre-clinical models of prostate cancer and bony metastasis and in clinical trials of patients treated with a dual tumor and stroma targeting strategies. In conclusion, understanding and targeting the interaction of the tumor and its stromal microenvironmant may improve the prognosis, reduce the suffering and increase the survival of patients with advanced cancer metastasis.

Inhibition of nuclear factor κB induces apoptosis following treatment with tumor necrosis factor α and an antioxidant in human prostate cancer cells

Transforming growth factor beta-1 (TGFbeta-1) and tumor necrosis factor alpha (TNF-alpha), an activator of nuclear factor kappa B (NF-kappaB), modulate apoptosis and/or cell growth. This study was designed to investigate the activity of NF-kappaB and its regulation of inhibitor of apoptosis gene (c-IAP2) in two human prostate cancer cell lines, DU-145 (which is androgen unresponsive) and ALVA-101 (which is moderately androgen responsive). These cells were treated with and without various concentrations of a strong antioxidant, pyrrolidinedithiocarbamate (PDTC), and TNF-alpha at various time intervals. Following treatments, cell growth and apoptosis were determined by ELISA techniques. NF-kappaB activity was determined by electrophoretic mobility shift assay (EMSA), and c-IAP2 mRNA production was determined with Northern blot analysis. PDTC treatment significantly reduced cell growth up to 80% in both DU-145 and ALVA-101 cells. TNF-alpha and lower but not higher doses of PDTC combined demonstrated an additive inhibition of cell growth in both cell lines. Active NF-kappaB and c-IAP2 was blocked significantly following PDTC treatments, whereas treatments with TNF-alpha alone showed increased NF-kappaB activity and c-IAP2. However, when both PDTC and TNF-alpha were combined, nuclear presence of NF-kappaB and c-IAP2 were reduced significantly (P < 0.05) to levels observed with PDTC alone. In conclusion, the antioxidant, PDTC, appears to initiate apoptosis by blocking cytoplasmic NF-kappaB translocation to the nucleus where it normally activates the production of apoptosis-inhibitory proteins like c-IAP2. Both TNF-alpha and PDTC alone cause apoptosis and reduce cell growth, but their combined effects are additive in reducing cell growth of DU-145 and ALVA-101 human prostate cancer cells.

Transforming growth factor-beta 2 heterozygous mutant mice exhibit Cowper's gland hyperplasia and cystic dilations of the gland ducts (Cowper's syringoceles)

Analyses of mutant mice with a deletion for the transforming growth factor beta 2 (Tgfbeta2) gene revealed cysts in the perineal/scrotal region of male mice. We present evidence from in situ, light and electron microscopy that the cysts observed in Tgfbeta2+/- heterozygous mice males derive from Cowper's gland tissue. The Cowper's glands of Tgfbeta2+/- heterozygous mutant mice display all steps of glandular hyperplasia and cystic dilation. TGF-beta isoforms and TGF-beta receptor (TbetaR-II) were localized immunocytochemically in sections of Cowper's glands. TGF-beta2 and TGF-beta3 were located predominantly in myoepithelial cells of the Cowper's gland whereas the TbetaRII was found in the plasma membrane of the acinar cells. TUNEL-assays revealed that apoptotic cell death is significantly reduced in Cowper's glands of TgfbetaB2+/- heterozygous mutant mice. The fact that Tgfbeta2+/- heterozygous mutant mice exhibit hyperplasia of Cowper's gland epithelium and Cowper's gland cysts suggests a disturbance of epithelial-stromal interaction most likely due to reduced TGF-beta2 level, accompanied by a significant decrease in apoptosis.

Growth factors: roles in andrology

Mesenchymal-epithelial interactions are extremely important during growth and development and in the functional cytodifferentiation of male sex accessory organs. Interactions between mesenchyme and epithelium occur mainly through a paracrine action that is mediated by various growth factors. The role of androgens is very important for these organs and the androgenic effect is mediated by paracrine interactions. A number of growth factors have been studied in prostate and seminal vesicles from mice, rats, and humans because they are potent mediators of cellular proliferation, differentiation, and death. This review provides an overview of current knowledge about growth factors involved in the development of male sex accessory organs, with particular emphasis on the prostate.

Effects of transforming growth factor beta-1 and all-trans-retinoic acid on androgen-induced development of neonatal mouse bulbourethral glands in vitro

Effects of transforming growth factor beta-1 (TGF-beta1) and all-trans-retinoic acid (All-trans-RA) on development of bulbourethral glands (BUGs) of neonatal mice were investigated in vitro. BUGs from 0-day-old male mice were cultured for 6 days in serum-free, chemically defined medium containing transferrin and bovine serum albumin, supplemented with 5alpha-dihydrotestosterone (DHT; 10-8 M) and insulin (10 microg/mL) alone or in combination. Prior to culture, BUGs from 0-day-old mice consisted of a simple epithelial rudiment encapsulated by mesenchyme. Epithelial growth and ductal branching occurred in BUGs cultured in medium containing DHT and insulin or DHT alone, but epithelial branching did not occur in BUGs cultured in the presence of insulin alone. Addition of TGF-beta1 at concentrations of > 5 ng/mL (0.2 x 10-9 M) to medium containing both insulin and DHT, inhibited the expected increase in overall size of BUGs, epithelial area and ductal branching in a dose-dependent manner. TGF-beta1 also decreased [3H]-thymidine labelling indices of both epithelium and mesenchyme. TGF-beta1 at 10 ng/mL elicited these inhibitory effects on BUGs cultured in medium containing DHT alone. Addition of All-trans-RA (10-8 to 10-6 M) to the medium containing DHT plus insulin, or DHT alone did not exert significant effects on either overall size of BUGs or epithelial growth and ductal branching. All-trans-RA at 10-6 M decreased the [3H]-thymidine labelling index of mesenchyme of BUGs cultured in medium with DHT plus insulin or DHT alone, but did not decrease the [3H]-thymidine labelling index of epithelium. The present results indicate that TGF-beta1 inhibits androgen-induced epithelial and mesenchymal growth as well as epithelial morphogenesis of BUGs from neonatal mice. Such an inhibitory effect of TGF-beta1 is not mimicked by All-trans-RA at physiological concentrations.

Amphiregulin is coordinately expressed with heparin-binding epidermal growth factor-like growth factor in the interstitial smooth muscle of the human prostate

Peptide growth factors have been proposed as mediators of smooth muscle-epithelial cell interactions in the human prostate; however, the identity of these molecules has not been established. In this study, we compared expression levels of messenger RNAs (mRNAs) encoding the epidermal growth factor (EGF) receptor-related receptor tyrosine kinases (ErbB1 through 4), the six EGF receptor ligands, EGF, transforming growth factor (TGF)-alpha, amphiregulin (ARG), HB-EGF, betacellulin, and epiregulin, and the related molecule heregulin-alpha, in a series of 10 prostate tissue specimens. Only EGF showed a disease-specific association, with increased mRNA levels in four of five PCa specimens in comparison to matched normal tissue from the same subject. In contrast, ARG and HB-EGF mRNAs showed a coordinate pattern of expression in 7/10 specimens that was distinct from all other growth factor or receptor genes examined and from mRNAs for prostate specific antigen, the androgen receptor and GAPDH, a house-keeping enzyme. Analysis of an additional series of benign prostatic hyperplasia and prostate cancer specimens from 60 individuals confirmed that ARG and HB-EGF mRNA levels varied in a highly coordinate manner (r = 0.93; P < 0.0001) but showed no association with disease. ARG was immunolocalized largely to interstitial smooth muscle cells (SMC), previously identified as the site of synthesis of HB-EGF in the prostate, while the cognate ARG and HB-EGF receptor, ErbB1, was localized exclusively to ductal epithelial cells and carcinoma cells. Although ARG was a relatively poor mitogen for Balb/c3T3 cells in comparison to HB-EGF, it was similar in potency to HB-EGF in stimulating human prostate epithelial cell growth, suggesting that prostate epithelia may be a physiologic target for ARG in vivo. Expression of both ARG and HB-EGF mRNAs was induced in cultured prostate SMC by fibroblast growth factor-2, a human prostate SMC mitogen linked to prostate disease. These findings indicate that ARG and HB-EGF are likely to be key mediators of directional signaling between SMC and epithelial cells in the human prostate and appear to be coordinately regulated.

Transforming growth factor beta-1 and beta-2 and type II receptor functional regulation of ALVA-101 human prostate cancer cells

Transforming growth factor beta-1 (TGFbeta-1) causes apoptosis of many epithelial cells, including the prostate, but other secondary effects of TGFbeta-1 may be important in carcinogenesis. In a human prostate cancer cell line (ALVA-101), we determined the effects of TGFbeta-1 and TGFbeta type I and II receptor antibody on cell proliferation and TGFbeta-1 receptor binding. TGFbeta-1 and -2 and TGFbeta type II receptor mRNA expression levels were determined by polymerase chain reaction (PCR) and Northern blot analysis. A dose-responsive suppression (0.03 to 10 ng/mL) was observed for cells treated with TGFbeta-1 from 3 to 7 days (P < .01). Untreated cells had 1.1 x 10(3) (n = 3) TGFbeta receptors per cell, with a Kd of 0.20 nmol/L (n = 3) as determined by Scatchard analysis; treatment for 3 days with TGFbeta-1 (1 ng/mL) reduced the receptor number (0.9 x 10(3)) and the Kd (0.12 nmol/L). Antibodies to TGFbeta type I and II receptor stimulated proliferation with or without added TGFbeta-1 (50% +/- 5% above control, P < .01, n = 6). TGFbeta-1 and -2 and TGFbeta type II receptor mRNA expression was observed in untreated cells. In cells treated with TGFbeta-1, TGFbeta-1 mRNA was not affected by treatment, but expression levels of the TGFbeta type II receptor and TGFbeta-2 mRNA were moderately suppressed after 72 hours of treatment. Control cells actively produced TGFbeta-1 as measured by radioimmunoassay. The active and inactive forms of TGFbeta-1 were approximately equal, but TGFbeta-2 was secreted in smaller quantities than TGFbeta-1 and the inactive form of TGFbeta-2 predominated, with very small amounts of the active form. Our results suggest that the human prostate cancer cell line ALVA-101 retains negative control of proliferation in response to TGFbeta-1. Inhibition of endogenous TGFbeta action by antibodies to its receptor enhances the growth of ALVA-101 human prostate cancer cells, suggesting that endogenous TGFbeta exerts an inhibitory control on their growth and cellular function.

Later onset of apoptosis in the bulbourethral glands after castration compared to that in the seminal vesicles

Androgens affect many different target organs within the male reproductive tract to stimulate their development and secretory cytodifferentiation, and to maintain structure and function in adulthood. Castration causes regression of these organs via apoptosis. However, not all organs of the reproductive tract are equally sensitive to androgen withdrawal. The effects of castration on the mouse seminal vesicles (SVs) and bulbourethral glands (BUGs) were compared in terms of protein and DNA contents, epithelial apoptosis, and proliferative response of epithelial cells to androgen. Castration induced similar, marked decreases in protein contents in the SV and BUG by 2 days after castration which reached a minimum at 16 days post castration. Both organs underwent a decrease in DNA content, but the kinetics of this decline differed. In the SV, DNA content was significantly decreased by 4 days whereas in the BUG this did not occur until 16 days post castration. By day 16 both organs had regressed to roughly the same degree. The apoptotic index in the epithelium reflected this difference in timing as well. Apoptotic index of the SV epithelium was highest on day 3 after castration and declined thereafter. On the other hand, the apoptotic index in the BUG didn't begin to increase until 7 days after castration and became maximal on day 12. Daily injections of testosterone propionate (TP) from day 8, 16, or 30 after castration all increased epithelial labelling index in the SVs to a similar degree. However, the TP-induced increase in the epithelial labelling index in the BUG beginning on day 8 after castration was considerably less than that in BUGs receiving TP treatment from day 16 or 30 after castration. Thus, the proliferative response of the epithelium depended upon prior apoptosis in the gland, with the timing being delayed in the BUG as compared with the SV. The present results indicate that castration induces epithelial apoptosis and reduction in glandular DNA content considerably later in the BUG than in the SV though reduction in protein content in the BUG fell simultaneously with that in the SV.

Transforming growth factor beta1 is associated with angiogenesis, metastasis, and poor clinical outcome in prostate cancer

BACKGROUND

Prostate tumors express high levels of transforming growth factor-beta1 (TGF-beta1) and seem to acquire resistance to its antiproliferative effects with tumor progression. Moreover, TGF-beta1 could be involved in tumor-promoting processes such as angiogenesis, cell migration, and immunosuppression.

METHODS

Immunoreactivity for TGF-beta1 and its receptors type I and type II (TGFbeta-RI and TGFbeta-RII), tumor vascular count, and cell proliferation were studied in 73 cases of prostate cancer, diagnosed between 1975-1983 and followed with surveillance.

RESULTS

Patients with tumor overproduction of TGF-beta1 had shorter median cancer-specific survival than patients with normal TGF-beta1 immunoreactivity (5.0 vs. 10 years, P = 0.006). Furthermore, increased TGF-beta1 staining was associated with tumor grade, high vascular counts, and metastasis (P = 0.02, 0.02, and 0.01, respectively). Patients with loss of tumor TGFbeta-RII expression in combination with TGF-beta1 overproduction showed particularly short survival (2.6 vs. 10 years, P = 0.0000), when compared to patients with normal immunoreactivity.

CONCLUSIONS

Overproduction of TGF-beta1 and loss of TGFbeta-RII expression are associated with poor clinical outcome in prostate cancer, and TGF-beta1 may promote tumor progression by stimulating angiogenesis and metastasis.

Interactions between adult human prostatic epithelium and rat urogenital sinus mesenchyme in a tissue recombination model

Tissue recombinants composed of adult human prostatic epithelium (hPrE) and rat urogenital sinus mesenchyme (rUGM) were grafted beneath the renal capsule of athymic rodent hosts. The pseudostratified human epithelium initially became multilayered, solid epithelial cords emerged, grew into the surrounding mesenchyme and canalized to regenerate a pseudostratified epithelium. Basal cells expressed cytokeratins 5 and 14, while luminal cells expressed cytokeratins 8 and 18, prostate specific antigen and prostatic acid phosphatase. The rat mesenchymal component differentiated into thick sheets of smooth muscle, characteristic of the human but not the rat prostate. These findings indicate that epithelial-mesenchymal interactions were reciprocal. Rat UGM induced adult hPrE to form new ductal-acinar tissue, involving epithelial proliferation, ductal branching morphogenesis and functional cytodifferentiation. Concurrently the epithelium dictated smooth muscle differentiation and patterning. Species-specific reverse transcriptase polymerase chain reaction SC (RT-PCR) analysis of the tissue recombinants was performed to separately examine the expression of epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), TGF-beta 1, and TGF-beta 3 in the epithelium, stroma and host components of the graft. All of these genes, except TGF-beta 1, were expressed in all three tissues. Human TGF-beta 1 was not detected, indicating that this gene was not expressed in human prostatic epithelium but was present in stroma.

In utero and lactational exposure of the male rat to 2,3,7,8-tetrachlorodibenzo-p-dioxin impairs prostate development. 2. Effects on growth and cytodifferentiation

In the male Holtzman rat, in utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure decreases prostate weight without inhibiting testicular androgen production or decreasing circulating androgen concentrations. Therefore, the present study sought to characterize effects of TCDD exposure on prostate development, from very early outgrowth from the urogenital sinus (Gestation Day [GD] 20) until rapid growth and differentiation are essentially complete (Postnatal Day [PND] 32). Pregnant Holtzman rats were administered a single dose of TCDD (1.0 microgram/kg po) or vehicle on GD 15 and offspring were exposed via placental transfer (GD 20 euthanasia) or placental and subsequent lactational transfer until euthanasia (if before PND 21) or weaning. Results show that the prostatic epithelial budding process was impaired by in utero TCDD exposure, as evidence by significant decreases in the number of buds emerging from dorsal, lateral, and ventral aspects of the GD 20 urogenital sinus. Ventral prostate cell proliferation index was significantly decreased on PND 1 but was similar to or higher than control at later times, whereas apoptosis was an extremely rare event in ventral prostates from both control and TCDD-exposed animals. Delays were noted in the differentiation of pericordal smooth muscle cells and luminal epithelial cells. In addition, ventral prostates from approximately 40% of TCDD-exposed animals examined on PNDs 21 and 32 exhibited alterations in the histological arrangement of cell types that could not be explained by a developmental delay. Compared to controls, these ventral prostates exhibited a disorganized, hyperplastic epithelium containing fewer luminal epithelial cells and an increased density or continuous layer of basal epithelial cells, as well as thicker periductal smooth muscle sheaths. In addition, in ventral prostates from TCDD-exposed animals, the intensity of androgen receptor staining was relatively low in the central and distal epithelium, and the number of androgen receptor-positive cells was relatively high in the periductal stroma. These data suggest that in utero and lactational TCDD exposure interferes with prostate development by decreasing very early epithelial growth, delaying cytodifferentiation, and, in the most severely affected animals, producing alterations in epithelial and stromal cell histological arrangement and the spatial distribution of androgen receptor expression that may be of permanent consequence.

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor α, retinoic acid, vitamin D3, and the transforming growth factor β families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

Transforming growth factor beta 1 transduced mouse prostate reconstitutions: I. Induction of neuronal phenotypes

BACKGROUND

We previously showed that retroviral transduction of transforming growth factor beta 1 (TGF-beta 1) induces focally hyperplastic lesions resembling benign prostatic hyperplasia (BPH) and an increase in the number of ganglion-like cells in the mouse prostate reconstitution (MPR) model in vivo. In the present study we further characterize the neuronal phenotypes induced by TGF-beta 1 retroviral transduction in MPRs.

METHODS

Computer-assisted morphometric analysis was used to evaluate neuronal density. Neuronal cell markers, including neurofilament, neuron-specific enolase, tyrosine hydroxylase, choline acetyltransferase, L-met enkaphaline, and serotonin, were detected by immunostaining.

RESULTS

A fourfold increase in neuronal density was observed in TGF-beta 1 retrovirus-transduced MPRs. The relative frequencies of neuronal subtypes remained similar, with catecholaminergic and cholinergic neurons presenting as the most abundant. We found no evidence of infection of neurons; therefore, increased neuronal density was likely due to paracrine activities.

CONCLUSIONS

Our results suggest that enforced TGF-beta 1 expression leads to growth and/or survival of both catecholaminergic and cholinergic neuronal cells in mouse prostate reconstitutions.

Stimulative effect of transforming growth factor-beta on collagen synthesis by human prostatic stromal cells in vitro

BACKGROUND

Expression of transforming growth factor-beta (TGF-beta) in the prostate has been reported. The purpose of this study was to evaluate the effect of TGF-beta on collagen synthesis by stromal cells isolated from a patient with benign prostatic hyperplasia (BPH).

METHODS

Human prostatic stromal cells (HPSC) derived from BPH tissue were cultured in serum-free medium. After incubation with TGF-beta1, the concentration of procollagen type I C-peptide (PIP) in the HPSC-conditioned medium was measured by enzyme immunoassay while the concentration of procollagen type III N-peptide (PIIIP) was measured by radioimmunoassay. Per-cell production of each type of collagen was calculated by multiplying the measured concentration by the volume of medium and dividing by the number of harvested cells.

RESULTS

One ng/mL of TGF-beta1 significantly (P < 0.05) increased collagen production by HPSC, to 220% and 120% of control for types I and III, respectively. Increasing the amount of TGF-beta1 to 10 ng/mL had no further effect. TGF-beta1 did not significantly affect HPSC number at concentrations of either 1 or 10 ng/mL. There was a strong correlation between PIP and PIIIP production (r = 0.929, P < 0.001).

CONCLUSION

These findings suggest that TGF-beta1 stimulates accumulation of extracellular matrix in stromal BPH tissue without affecting proliferation of stromal cells.

Insulin-like growth factor binding protein-3 and -5 are regulated by transforming growth factor-beta and retinoic acid in the human prostate adenocarcinoma cell line PC-3

The family of insulin-like growth factor binding proteins (IGFBPs) can affect cell proliferation by modulating the availability and bioactivity of insulin-like growth factors (IGFs), or by mechanisms independent of IGFs. To understand better the role(s) of IGFBPs in prostate growth and malignancy, we examined the regulation of IGFBPs in PC-3 cells, a human prostatic adenocarcinoma epithelial cell line that is androgen-insensitive. Both transforming growth factor-beta (TGF-beta) and retinoic acid (RA), known inhibitors of cellular proliferation, significantly changed the IGFBP profile in PC-3 cells. In cells that were treated with transforming growth factor beta-2 (TGF-beta 2) (0.5-10 ng/mL), IGFBP-3, and IGFBP-5 protein and mRNA increased in a time- and dose-dependent manner. At 10 ng/mL TGF-beta, IGFBP-3, and IGFBP-5 protein concentrations were 14- and 9-fold, respectively, over that of controls. Cells treated with RA (0-1 microM) also showed a time- and dose-dependent increase in IGFBP-3 protein and mRNA levels. However, in contrast to TGF-beta 2, high concentrations of RA (1 microM) negatively regulated IGFBP-5 expression, with IGFBP-5 mRNA levels downregulated to 20% of that of the control, and protein levels were decreased by 50%. Since both TGF-beta and RA increased IGFBP-3 expression and both are known to inhibit prostate cell growth, we speculate that the inhibition of growth is mediated, at least in part, by IGFBP-3.