Successive waves of apoptosis in the rat prostate after repeated withdrawal of testosterone stimulation

Fatty Acid Signaling Impacts Prostate Cancer Lineage Plasticity in an Autocrine and Paracrine Manner

Prostate cancer (PCa) affects an estimated 250,000 men every year and causes 34,000 deaths annually. A high-fat diet and obesity are associated with PCa progression and mortality. This study's premise was the novel observation of crosstalk between PCa epithelia and cancer-associated fibroblasts (CAF) in response to palmitate-mediated lineage plasticity. We found that cholesterol activated canonical Hedgehog (Hh) signaling by increasing cilium Gli activity in PCa cells, while palmitate activated Hh independent of Gli. Exogenous palmitate activated SOX2, a known mediator of lineage plasticity, in PCa cells cocultured with CAF. Stroma-derived Wnt5a was upregulated in CAF while cocultured with PCa cells and treated with palmitate. Wnt5a knockdown in CAF inhibited Hh and SOX2 expression in PCa cells from cocultures. These findings supported our proposed mechanism of a high-fat diet promoting Hh signaling-mediated transformation within the tumor microenvironment. SOX2 and Wnt5a expression were limited by the CD36 neutralizing antibody. Mice xenografted with PCa epithelia and CAF tumors were fed a high-fat diet, leading to elevated SOX2 expression and lineage plasticity reprogramming compared to mice fed an isocaloric rodent diet. CD36 inhibition with enzalutamide elevated apoptosis by TUNEL, but limited proliferation and SOX2 expression compared to enzalutamide alone. This study revealed a mechanism for a high-fat diet to affect prostate cancer progression. We found that saturated fat induced lineage plasticity reprogramming of PCa by interaction with CAF through Wnt5a and Hh signaling.

Signaling Pathways That Control Apoptosis in Prostate Cancer

Prostate cancer is the second most common malignancy and the fifth leading cancer-caused death in men worldwide. Therapies that target the androgen receptor axis induce apoptosis in normal prostates and provide temporary relief for advanced disease, yet prostate cancer that acquired androgen independence (so called castration-resistant prostate cancer, CRPC) invariably progresses to lethal disease. There is accumulating evidence that androgen receptor signaling do not regulate apoptosis and proliferation in prostate epithelial cells in a cell-autonomous fashion. Instead, androgen receptor activation in stroma compartments induces expression of unknown paracrine factors that maintain homeostasis of the prostate epithelium. This paradigm calls for new studies to identify paracrine factors and signaling pathways that control the survival of normal epithelial cells and to determine which apoptosis regulatory molecules are targeted by these pathways. This review summarizes the recent progress in understanding the mechanism of apoptosis induced by androgen ablation in prostate epithelial cells with emphasis on the roles of BCL-2 family proteins and "druggable" signaling pathways that control these proteins. A summary of the clinical trials of inhibitors of anti-apoptotic signaling pathways is also provided. Evidently, better knowledge of the apoptosis regulation in prostate epithelial cells is needed to understand mechanisms of androgen-independence and implement life-extending therapies for CRPC.

The protective effect of Sophora japonica on prostatic hypertrophy and inflammation in rat

The atypical adenomatous hyperplasia (AAH) is invariably an incidental histological change, with no clinical findings specific for its diagnosis, and the mean patient age at diagnosis is 64-70 years. The incidence of AAH varies between 1.5 and 19.6% of transurethral resections and in up to 33% of radical prostatectomies. Herbal medicines are becoming a popular option in the treatment of prostatic-related diseases, such as date palm pollen and saw palmetto in the treatment of prostatic hyperplasia. A testosterone/citral-induced AAH in Wistar rat model was used to evaluate the protective effect of Sophora japonica fruit extract (SFE). The present study suggests that SFE has an ameliorating effect on the prostatic hypertrophy and inflammation through its effect on clusterin, IGF, IL-6, IL-8, TNF-α, and TGF-β1 expression. In addition, the administration of SFE ameliorated the inflammatory score, and histopathological changes in AAH-induced rats in a dose-dependent manner. The treatment with SFE reduced the number of prostatic acini in AAH rat model and decreased the production of pro-inflammatory cytokines. The fruit extract of S. japonica was characterized by determination total phenol content (60.3 mg of gallic acid equivalent/g of dry extract), total flavonoid content (97.9 mg quercetin equivalent/g of dry extract) and the major isoflavonoid sophoricoside (302.9 ± 2.6 µg/g of the extract). In conclusion, SFE has an ameliorating effect on the prostatic hypertrophy and inflammation. This effect may be attributed to the ability of SFE to decrease the production of pro-inflammatory cytokines, TNF-α, IL-1β and IGF-1 as well as an increase in TGF-β1.

TDP2 suppresses genomic instability induced by androgens in the epithelial cells of prostate glands

Androgens stimulate the proliferation of epithelial cells in the prostate by activating topoisomerase 2 (TOP2) and regulating the transcription of target genes. TOP2 resolves the entanglement of genomic DNA by transiently generating double‐strand breaks (DSBs), where TOP2 homodimers covalently bind to 5′ DSB ends, called TOP2‐DNA cleavage complexes (TOP2ccs). When TOP2 fails to rejoin TOP2ccs generating stalled TOP2ccs, tyrosyl DNA phosphodiesterase‐2 (TDP2) removes 5′ TOP2 adducts from stalled TOP2ccs prior to the ligation of the DSBs by nonhomologous end joining (NHEJ), the dominant DSB repair pathway in G₀/G₁ phases. We previously showed that estrogens frequently generate stalled TOP2ccs in G₀/G₁ phases. Here, we show that physiological concentrations of androgens induce several DSBs in individual human prostate cancer cells during G₁ phase, and loss of TDP2 causes a five times higher number of androgen‐induced chromosome breaks in mitotic chromosome spreads. Intraperitoneally injected androgens induce several DSBs in individual epithelial cells of the prostate in TDP2‐deficient mice, even at 20 hr postinjection. In conclusion, physiological concentrations of androgens have very strong genotoxicity, most likely by generating stalled TOP2ccs.

Macrophage roles in the clearance of apoptotic cells and control of inflammation in the prostate gland after castration

BACKGROUND

Androgen deprivation results in massive apoptosis in the prostate gland. Macrophages are actively engaged in phagocytosing epithelial cell corpses. However, it is unknown whether microtubule-associated protein 1 light chain 3 alpha (LC3)-associated phagocytosis (LAP) is involved and contribute to prevent inflammation.

METHODS

Flow cytometry, RT-PCR and immunohistochemistry were used to characterize the macrophage subpopulation residing in the epithelial layer of the rat ventral prostate (VP) after castration. Stereology was employed to determine variations in the number of ED1 and ED2. Mice were treated with either chloroquine or L-asparagine to block autophagy.

RESULTS

M1 (iNOS-positive) and M2 macrophages (MRC1+ and ARG1+) were not found in the epithelium at day 5 after castration. The percentage of CD68⁺ (ED1) and CD163⁺ (ED2) phenotypes increased after castration but only CD68⁺ cells were present in the epithelium. RT-PCR showed increased content of the autophagy markers Bcl1 and LC3 after castration. In addition, immunohistochemistry showed the presence of LC3⁺ and ATG5⁺ cells in the epithelium. Double immunohistochemistry showed these cells to be CD68⁺ /LC3⁺ , compatible with the LAP phenotype. LC3⁺ cells accumulate significantly after castration. Chloroquine and L-asparagine administration caused inflammation of the glands at day 5 after castration.

CONCLUSIONS

CD68⁺ macrophages phagocytose apoptotic cell corpses and activate the LAP pathway, thereby contributing to the preservation of a non-inflammed microenvironment. Marked inflammation was detected when autophagy blockers were administered to castrated animals.

Androgen deprivation and immunotherapy for the treatment of prostate cancer

Prostate cancer is the most common newly diagnosed malignancy in men, and the second most common cause of cancer-related death in the United States. The primary treatment for recurrent prostate cancer is androgen deprivation, and this therapy is typically continued lifelong for patients with metastatic prostate cancer. Androgens and androgen deprivation have profound effects on the immune system, a finding that has become more appreciated in an era where immune-based treatments for cancer are being increasingly explored. Preclinical studies suggest that androgen deprivation could potentially positively or negatively affect the use of approved immunotherapies, or those that are being developed for the treatment of prostate cancer. In this review, we provide a brief overview of the different types of androgen deprivation treatments used in the management of prostate cancer, discuss their effects on prostate tumors and the immune system and how they are being explored in combination with immunotherapy. Finally, we address some of the critical questions in the field that must be answered to identify the best approaches to combine androgen deprivation with immunotherapy for the treatment of prostate cancer.

The prostate response to prolactin modulation in adult castrated rats subjected to testosterone replacement

Despite the androgenic dependence, other hormones, growth factors, and cytokines are necessary to support prostatic growth and maintain the glandular structure; among them, prolactin is a non-steroidal hormone secreted mainly by the pituitary gland. However, extra-pituitary expression of prolactin, such as in the prostate, has also been demonstrated, highlighting the paracrine and autocrine actions of prolactin within the prostate. Here, we investigated whether prolactin modulation alters ventral prostate (VP) morphophysiology in adult castrated rats. Sprague Dawley rats were castrated and after 21 days, divided into ten experimental groups (n = 6/group): castrated control: castrated animals that did not receive treatment; castrated+testosterone: castrated animals that received T (4 mg/kg/day); castrated+PRL (PRL): castrated animals receiving prolactin (0.3 mg/kg/day); castrated+T+PRL: castrated animals that received a combination of testosterone and prolactin; and castrated+bromocriptine (BR): castrated animals that received bromocriptine (0.4 mg/kg/day). The control group included intact animals. The animals were treated for 3 or 10 consecutive days. At the end of experimental period, the animals were euthanized, and the blood and VP lobes were collected and analyzed by different methods. The main findings were that the administration of prolactin to castrated rats did not exert anabolic effects on the VP. Although we observed activation of downstream prolactin signaling after prolactin administration, this was not enough to overcome the prostatic androgen deficiency. Likewise, there was no additional glandular involution in the castrated group treated with bromocriptine. We concluded that despite stimulating the downstream signaling pathway, exogenous prolactin does not act on VP in the absence or presence of high levels of testosterone.

Cynanchum wilfordii Ameliorates Testosterone-Induced Benign Prostatic Hyperplasia by Regulating 5α-Reductase and Androgen Receptor Activities in a Rat Model

Benign prostatic hyperplasia (BPH) is characterized by uncontrolled proliferation of the prostate gland. Cynanchum wilfordii has been reported to improve sexual behavior in male rats. In this study, we investigated the protective effect of an aqueous extract of C. wilfordii (CWW) against BPH development in a testosterone-induced BPH rat model. The rats were divided into the following six groups: sham/vehicle; BPH/vehicle; BPH/finasteride; and three CWW doses (50, 100, and 200 mg/kg). After a 4-week treatment with CWW, the rats were euthanized at scheduled times, and their prostates were weighed, followed by a histopathological examination. Prostate growth inhibition rates in rats administered CWW 50, 100, and 200 mg/kg were 54.5%, 51.8%, and 50.1%, respectively. The BPH/CWW group showed decreased serum testosterone and dihydrotestosterone (DHT) levels compared to the BPH/vehicle group. Furthermore, the BPH/CWW group showed reduced prostate testosterone and DHT levels compared to the BPH/vehicle group. Mechanistically, the reverse transcription-polymerase chain reaction revealed downregulated mRNA expression levels of the androgen receptor, 5α-reductase, and B-cell lymphoma-2 (Bcl-2) in the BPH/CWW200 group compared with those in the testosterone-induced groups. In conclusion, these findings show the effectiveness of CWW in slowing the progression of testosterone-induced BPH in rats.

Apoptosis in the Epididymal Epithelium of Adult Male Golden Hamster Exposed to Diethylstilbestrol

Apoptosis in the testis and prostate exposed to disrupters of endocrine function, including diethylstilbestrol (DES), during neonatal or postnatal periods has repeatedly been demonstrated, but not in the mature epididymis. We investigated the effects of DES, a potent and synthetic estrogen, on apoptosis in the adult. Adult male golden hamsters received an SC injection of DES and were then sacrificed to collect epididymides after 1, 4, or 7 days of treatment. A significant decrease in epididymal weight and an increase in apoptotic cells were shown on the first day after DES injection. Flow cytometry showed that DES treatment (1 mg/kg) for 1, 4, or 7 days induced significant apoptosis both in the caput and the cauda epididymides. Greater numbers of apoptotic cells were detected in the caput than in the cauda at a fixed time after DES treatment. Serum levels of testosterone decreased markedly within 24 hr after DES administration, reaching undetectable levels of 0.1 ng/ml at 4 days and thereafter. These results indicate that DES administration can increase epididymal apoptosis with a decrease in serum testosterone levels. Because DES used to be injected into domestic animals, adult males also have a chance to take this substance through food. Our study indicates that exposure to DES in adults is as toxic as that in the perinatal period.

Expression of β-catenin and mesenchymal markers in canine prostatic hyperplasia and carcinoma

β-catenin is a nuclear signalling molecule that is associated with human prostatic neoplasia and the epithelial-mesenchymal transition (EMT) process. The present study evaluates immunohistochemically the expression of β-catenin and the mesenchymal markers vimentin, desmin, calponin and smooth muscle actin (SMA) in four normal canine prostates and prostate samples from 15 dogs with benign prostatic hyperplasia (BPH) and six with prostatic carcinoma (PC). β-catenin was located on the membrane of normal epithelial cells, while the same marker had both cytoplasmic and membrane expression in hyperplastic cells and a nuclear redistribution in PC. Vimentin-positive luminal cells were observed in two of the 15 cases of BPH and in all PC samples, suggesting the conversion of neoplastic epithelial cells to a mesenchymal type. SMA was consistently negative in PC, but there was mild desmin and calponin immunoreactivity in these lesions. As in men, β-catenin is involved in canine prostatic carcinogenesis, thus further validating the use of this animal model to study human prostatic disease.

Immunomodulatory effect of red onion (Allium cepa Linn) scale extract on experimentally induced atypical prostatic hyperplasia in Wistar rats

Red onion scales (ROS) contain large amounts of flavonoids that are responsible for the reported antioxidant activity, immune enhancement, and anticancer property. Atypical prostatic hyperplasia (APH) was induced in adult castrated Wistar rats by both s.c. injection of testosterone (0.5 mg/rat/day) and by smearing citral on shaved skin once every 3 days for 30 days. Saw palmetto (100 mg/kg) as a positive control and ROS suspension at doses of 75, 150, and 300 mg/kg/day were given orally every day for 30 days. All medications were started 7 days after castration and along with testosterone and citral. The HPLC profile of ROS methanolic extract displayed two major peaks identified as quercetin and quercetin-4′-β-O-D-glucoside. Histopathological examination of APH-induced prostatic rats revealed evidence of hyperplasia and inflammation with cellular proliferation and reduced apoptosis Immunohistochemistry showed increased tissue expressions of IL-6, IL-8, TNF-α, IGF-1, and clusterin, while TGF-β1 was decreased, which correlates with the presence of inflammation. Both saw palmetto and RO scale treatment have ameliorated these changes. These ameliorative effects were more evident in RO scale groups and were dose dependent. In conclusion, methanolic extract of ROS showed a protective effect against APH induced rats that may be attributed to potential anti-inflammatory and immunomodulatory effects.

The effect of anthocyanin on the prostate in an andropause animal model: rapid prostatic cell death by apoptosis is partially prevented by anthocyanin supplementation

Purpose

To evaluate the anti-apoptotic effect of the antioxidant reaction of anthocyanin on the prostate in an andropause animal model.

Materials and Methods

Sprague-Dawley rats were divided into three groups (n=12 in each): control (Group I), andropause (Group II), andropause treated with anthocyanin (Group III). For induction of andropause, Group II and III underwent bilateral orchiectomy. Group III was treated with daily oral anthocyanin (160 mg/kg) for 8 weeks. After 8 weeks, the rats were sacrificed and their blood and prostates were examined pathohistologically and evaluated for oxidative stress and apoptosis. Oxidative stress was assessed by the activity of superoxide dismutase (SOD) and apoptosis in the prostate was identified by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling assay.

Results

Group II showed markedly increased activity of SOD in serum over that observed in Group I, whereas the rats in Group III showed reduced oxidative stress compared to Group II. Despite no significant differences in prostate weight between Group II and III (p=0.078), the apoptotic index was significantly greater in Group II than Group I, and was significantly lesser in Group III than Group II.

Conclusions

We suggest that the oxidative stress caused by low testosterone may be another inducer of apoptosis, and this apoptosis may partly contribute to the overall apoptosis of the prostate in the andropause animal model. Therefore, anthocyanin supplementation may contribute to preventing excessively rapid cell death by apoptosis in the prostate in an animal model of andropause.

Molecular pathogenesis and progression of prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed noncutaneous malignancy and second leading cause of cancer-related deaths in US males. Clinically, locally confined disease is treated surgically and/or with radiation therapy. Invasive disease, however, must be treated with pharmacological inhibitors of androgen receptor (AR) activity, since disease progression is fundamentally reliant on AR activation. However, despite initially effective treatment options, recurrent castration-resistant PCa (CRPC) often occurs due to aberrant reactivation of AR. Additionally, it is appreciated that many other signaling molecules, such as transcription factors, oncogenes, and tumor suppressors, are often perturbed and significantly contribute to PCa initiation and progression to incurable disease. Understanding the interplay between AR signaling and other signaling networks altered in PCa will advance therapeutic approaches. Overall, comprehension of the molecular composition promoting neoplastic growth and formation of CRPC is paramount for developing durable treatment options.

Phase I trial of tremelimumab in combination with short-term androgen deprivation in patients with PSA-recurrent prostate cancer

CTLA-4 blockade has demonstrated antitumor efficacy in human clinical trials. The antitumor mechanism is presumably mediated in part by the expansion of tumor-specific T cells. Androgen deprivation, the cornerstone of treatment for patients with metastatic prostate cancer, has been shown to elicit prostate tissue apoptosis and lymphocytic inflammation. We hypothesized that treatment with androgen deprivation, followed by an anti-CTLA-4 antibody, could augment a tumor-specific immune response elicited by androgen deprivation. We report here the results of a phase I trial evaluating a humanized monoclonal antibody targeting CTLA-4, CP-675,206 (tremelimumab), in combination with androgen deprivation using an antiandrogen. Eligible patients were those with PSA-recurrent prostate cancer after primary surgery and/or radiation therapy, not previously treated with androgen deprivation, and without radiographic evidence of metastatic disease. Subjects were treated in two cycles, 3 months apart, in which they received bicalutamide 150 mg daily days 1-28 and tremelimumab on day 29. The primary endpoint of the trial was safety. Secondary endpoints included measures of PSA kinetics and identification of a maximum tolerated dose. Eleven patients were enrolled and completed at least 1 year of follow-up. Dose-limiting toxicities included grade 3 diarrhea and skin rash. No favorable changes in PSA doubling time were observed in a period shortly after completing treatment; however, three patients experienced a prolongation in PSA doubling time detectable several months after completing treatment. The identification of delayed, prolonged favorable changes in serum PSA suggests that future studies could explore this combination in studies evaluating time to disease progression.

Anti-inflammatory and antiproliferative activities of date palm pollen (Phoenix dactylifera) on experimentally-induced atypical prostatic hyperplasia in rats

BACKGROUND

Atypical prostatic hyperplasia (APH) is a pseudoneoplastic lesion that can mimic prostate adenocarcinoma because of its cytologic and architectural features. Suspension of date palm pollen (DPP) is an herbal mixture that is widely used in folk medicine for male infertility. The aim of the present study was to evaluate the effect of DPP suspension and extract on APH-induced rats.

METHODS

APH was induced in adult castrated Wistar rats by both s.c. injection of testosterone (0.5 mg/rat/day) and smearing citral on shaved skin once every 3 days for 30 days. Saw palmetto (100mg/kg), DPP suspension (250, 500 and 1000 mg/kg), and lyophilized DPP extract (150,300 and 600 mg/kg) were given orally daily for 30 days. All medications were started 7 days after castration and along with testosterone and citral.

RESULTS

The histopathological feature in APH-induced prostate rats showed evidence of hyperplasia and inflammation. Immunohistochemical examination revealed that the expressions of IL-6, IL-8, TNF-α, IGF-1 and clusterin were increased, while the expression of TGF-β1 was decreased that correlates with presence of inflammation. Moreover, histopathological examination revealed increased cellular proliferation and reduced apoptosis in ventral prostate. Both saw palmetto and DPP treatment has ameliorated these histopathological and immunohistochemical changes in APH-induced rats. These improvements were not associated with reduction in the prostatic weight that may be attributed to the persistence of edema.

CONCLUSION

DPP may have a potential protective effect in APH-induced Wistar rats through modulation of cytokine expression and/or upregulation of their autocrine/paracrine receptors.

Magnetic-nanoparticle-modified paclitaxel for targeted therapy for prostate cancer

A nontoxic drug nanocarrier containing carboxyl groups was successfully developed by mixing magnetic nanoparticles (MNPs) of Fe(3)O(4) with the water-soluble polyaniline derivative poly[aniline-co-sodium N-(1-one-butyric acid) aniline] (SPAnNa) and doping with HCl aqueous solution to form SPAnH/MNPs shell/core. SPAnH/MNPs could be used to effectively immobilize the hydrophobic drug paclitaxel (PTX), thus enhancing the drug's thermal stability and water solubility. Up to 302.75 mug of PTX could be immobilized per mg of SPAnH/MNPs. SPAnH/MNPs-bound-PTX (bound-PTX) was more stable than free-PTX at both 25 degrees C and 37 degrees C. Furthermore, bound-PTX was more cytotoxic to human prostate carcinoma cells (PC3 and CWR22R) than free-PTX at 37 degrees C, and the inhibition of cellular growth was even more pronounced when magnetic targeting was applied to the bound-PTX. These data indicate that this magnetically targeted drug delivery system provides more effective treatment of prostate cancer cells using lower therapeutic doses and thus with potentially fewer side-effects.

Matrix metalloproteinase (MMP)-2 and MMP-9 activity and localization during ventral prostate atrophy and regrowth

Matrix metalloproteinses (MMPs) are enzymes involved in prostatic development, growth, disease-induced tissue remodelling and secretory fluid. Although the prostate function depends upon androgen regulation, the relationship between MMPs and androgen has not been well established. Here, we evaluated MMP-2 and MMP-9 gelatinolytic activity in association with tissue localization during ventral prostate atrophy and regrowth induced by testosterone replacement (TR). Adult male Wistar rats were divided into three experimental groups: control, castrated (CS) and TR 21 days after castration. Ventral prostate (VP) was excised at 3, 5, 7 and 21 days after castration in CS group, and at 3, 5, 7 and 10 days after TR (4 mg/kg/day) in TR group. The VP was dissected, weighed and processed for histology, immunohistochemistry, ultrastructure and zymography analyses. Castration elicited the typical parenchymal atrophy and stromal condensation. TR induced intense epithelial growth towards the stromal space to restore the prostate histoarchitecture. MMP-2 and MMP-9 immunostaining presented intense reaction in CS and TR groups, mainly in the epithelial and endothelial cells. After TR, a strong immunoreaction for MMP-2 was observed in the activated stromal fibroblasts. Zymography showed that MMP-2 and MMP-9 activity, mainly the active form, increased after castration. In contrast, TR induced an additional increase in MMP-2 activity, but not in MMP-9. In conclusion, the overall behaviour of MMP-2 and MMP-9 within the prostate under androgen handling is highly complex, as each glandular compartment and cell type is affected differently by the androgenic status. Prostate regrowth appears to involve a more effective participation of MMP-2 in both epithelial and stromal compartments, while MMP-9 plays a major role in the late prostate atrophy and early regrowth.

Changes in gene expression following androgen receptor blockade is not equivalent to androgen ablation by castration in the rat ventral prostate

Involution of the rat ventral prostate and concomitant modulation of gene expression post-castration is a well- documented phenomenon. While the rat castration model has been extensively used to study androgen regulation of gene expression in the ventral prostate,it is not clear whether all the gene expression changes post-castration are due to androgen depletion alone. To obtain insights into this, we performed differential display reverse transcriptase polymerase chain reaction (DD-RT-PCR) which resulted in the identification of castration and/or flutamide-regulated genes in the rat ventral prostate. These include clusterin, methionine adenosyl transferase II alpha, and prostate-specific transcripts such as PBPC1BS, S100RVP and A7. While clusterin, PBPC1BS and methionine adenosyl transferase II alpha are regulated by both castration and flutamide, S100 RVP and A7 are regulated by castration alone. Interestingly, we show that flutamide, unlike castration, does not induce apoptosis in the rat ventral prostate epithelium, which could be an underlying cause for the differential effects of castration and flutamide treatment. We propose that castration leads to enrichment and depletion of stromal and epithelial cell types, respectively, resulting in erroneous conclusions on some of the cell type-specific transcripts as being androgen regulated.

Leuprorelin depot injection: patient considerations in the management of prostatic cancer

Hormone therapy is well established for treating patients with prostate cancer and remains the mainstay of the treatment of metastatic and locally advanced disease, this article reviews the rationale for its use, its different forms, and complications and controversies still surrounding some of its modalities. Availability of long-acting synthetic luteinizing hormone-releasing hormone (LHRH) agonists revolutionized the hormonal treatment of prostate cancer, and helped to avoid the emotional and psychological effects related to surgical castration. The depot formula has gained wide acceptance from both patients and physicians. This review emphasizes the newer, long-acting formula, leuprorelin (leuprolide acetate), especially the 6-month formula, its advantage over over shorter-acting depot products, and its potential to become a standard of care for patients eligible for androgen deprivation therapy.

Regulation of the expression of prostate apoptosis response protein 4 (Par-4) in rat granulosa cells

The par-4 gene, directs the expression of a protein in the rat ventral prostate after apoptotic stimuli but not growth stimulatory, growth arresting or necrotic signals. Since Par-4 expression appears to be ubiquitous we investigated the possibility of Par-4 having a role in the rat ovary granulosa cells apoptotic death. Par-4 mRNA was detected by RT-PCR with oligonucleotides designed to prime Par-4 leucine zipper in the ovaries of 12 day old rats and reached the higher levels in 24 days old rats. In situ hybridization analysis revealed that Par-4 expression is restricted to granulosa cells. PMSG priming of 24 day old rats for 2 days greatly reduced Par-4 expression in granulosa cells as determined by in situ hybridization, RT-PCR of mRNA and protein immunodetection with Western blot. Granulosa cells placed in serum-fee culture, exhibited increased levels of Par-4 mRNA and protein, in good correlation with the degree of apoptosis. The culture-induced increases in Par-4 are significantly prevented by FSH. Transient transfection of granulosa cells with Par-4 leucine zipper domain that functions as a dominant-negative regulator of Par-4 activity resulted in lower rates of apoptosis while overexpression of the full length Par-4 counteracted FSH effects on apoptosis. Par-4 association with PKCzeta which is supposed to inhibit this kinase mediated antiapoptotic way is also prevented by FSH and, FSH antiapoptotic effects are counteracted by a PKCzeta specific inhibitor. These findings indicate that FSH by suppressing Par-4 expression in the ovary activates PKCzeta-dependent antiapoptotic pathway and suggest that Par-4 is part of the mechanism underlying granulosa cells apoptotic demise.

Beyond simple castration: targeting the molecular basis of treatment resistance in advanced prostate cancer

Over the past 20 years, research on hormonal treatments for prostate cancer focused on maximizing androgen ablation through combination therapy. Unfortunately, maximal androgen ablation increases treatment-related side effects and expense and has not significantly prolonged time to androgen-independent (AI) progression. Intermittent androgen suppression (IAS) is based on the hypothesis that if tumor cells surviving androgen withdrawal can be forced along a normal pathway of differentiation by androgen replacement, then apoptotic potential might be restored, androgen dependence may be prolonged and progression to androgen independence may be delayed. Observations from animal model studies suggest that progression to androgen independence is delayed by IAS and this strategy is now being evaluated in phase III trials. Another strategy for improving therapies in advanced prostate cancer involves targeting genes that are activated by either androgen withdrawal or chemotherapy to delay or prevent the emergence of the resistant AI phenotype. Targeted inhibition of stress-associated increases in gene expression precipitated by androgen withdrawal or chemotherapy may enhance treatment-induced apoptosis and delay progression to AI disease. Proteins fulfilling these criteria include antiapoptotic members of the Bcl-2 protein family, clusterin, Hsp27, and IGFBP-2 and IGFBP-5. The purpose of this paper is to review the rationale and progress in using targeted gene therapies to enhance tumor cell death after androgen withdrawal or taxane chemotherapy. Antisense oligonucleotides offer one approach to target genes involved in cancer progression, especially those not amenable to small molecule or antibody inhibition. The current status and future direction of several antisense oligonucleotides that have potential clinical use in cancer are also reviewed.

Intermittent Androgen Castration: A Biological Reality during Intermittent Treatment in Metastatic Prostate Cancer?

INTRODUCTION

To assess the effects of intermittent maximal androgen blockade (IMAB) on testosterone (T) levels during on- and off-treatment periods.

MATERIALS AND METHODS

A total of 51 patients with metastatic prostate cancer underwent a 6-months period of continuous maximal androgen blockade (MAB) consisting of leuprorelin (3.75 mg at monthly intervals) plus flutamide (250 mg t.i.d.) followed by IMAB. During each cycle, the cut-off prostate-specific antigen (PSA) levels to stop and resume treatment were 4 and 10 ng/ml, respectively. IMAB continued until progression under treatment occurred. Monthly PSA and T measurements were performed in central laboratories.

RESULTS

From the 51 patients included (mean age 67.6 years), 27, 16, 12, 8 and 5 underwent a second, third, fourth, fifth and sixth cycle, respectively (mean follow up: 17 months). Before treatment, 4 patients had a T lower than normal laboratory value but these recovered all to a normal T value at the end of the first cycle. During the 6 cycles, only 8 patients did not recover a normal T at least once during the off-treatment periods (OTP). The mean T values at the end of each OTP did not change during these 6 cycles (Anova test, p=0.621) with a mean stable recovery delay of 32-43 days (Anova test, p=0.722).

CONCLUSION

IMAB protocol with an initial 6-month treatment period can result in an intermittent castration with the recovery of normal T levels in most patients during six consecutive cycles of treatment.

Roles and regulation of Wnt signaling and beta-catenin in prostate cancer

The Wnt signaling pathway and its key component beta-catenin play critical roles in embryonic development as well as in human diseases, including various malignancies. Accumulated evidence has demonstrated a significant role for the Wnt pathway in the development and progression of human prostate cancer. The recent discovery of an interaction between beta-catenin and the androgen receptor (AR) suggests a possible mechanism of cross talk between Wnt and androgen signaling pathways. In this review, we summarize the recent progresses in this interesting and growing field. Particularly, we focus on the observation that the activation of the Wnt-mediated signal occurs in a different manner in prostate cancer than in colorectal cancer or other human malignancies. Since mutations in Adenomatous polyposis coli (APC), beta-catenin, and other components of the beta-catenin destruction complex are rare in prostate cancer cells, other regulatory mechanisms appear to play dominant roles in the activation of beta-catenin, such as loss or reduction of E-cadherin, a component of cell adhesion complex, and abnormal expression of Wnt ligands, receptors, inhibitors, and other co-regulators. Understanding the role and regulation of the Wnt signaling pathway in prostate cancer cells may help identify new targets for the prostate cancer therapy.

Gene expression analysis in the ventral prostate of rats exposed to vinclozolin or procymidone

Vinclozolin and procymidone are antiandrogens that are thought to share a common androgen receptor (AR) mediated mechanism of action. This assessment is based primarily on morphological, AR binding, and in vitro transcriptional activation studies. Studies designed to evaluate the gene expression profiles induced by these compounds have the potential to provide further information to test this hypothesis. We have used targeted gene arrays to examine gene expression in the ventral prostate (VP) of 100-day old Sprague Dawley male rats exposed to either vinclozolin or procymidone. Animals were castrated and administered silastic implants with or without testosterone. A subset of testosterone treated animals was then dosed with 200 mg/kg of either fungicide in corn oil. Four treatment groups were used: castrated (C), testosterone (T), testosterone+vinclozolin (V), and testosterone+procymidone (P). Tissue from the VP was collected from six animals per group (3 animals per block x 2 blocks) at 20 h and at 4 days after the start of treatment. Total RNA was then isolated and gene expression analyzed using Clontech Atlas Rat 1.2 Toxicology arrays. When compared to group T, similar changes in gene expression were observed in groups C, P and V at both the 20 h and 4 day time points. After 20 h of treatment, 20 genes were similarly affected across these three treatment groups. Down-regulated genes included various molecular chaperones, the 11-kDa diazepam binding inhibitor, cyclin D1, and mitochondrial aspartate aminotransferase. Genes such as the androgen receptor, PTEN, and ERK2 were up-regulated. Three of the down-regulated genes, GRP78 (BiP), Dad1, and mitochondrial aspartate aminotransferase have been previously shown to be directly androgen regulated. Fifty-four genes were affected at 20 h, whereas, 311 genes were altered 4 days after the start of treatment. These observations, in part, may reflect regression of the VP at the later time point. These results support the hypothesis that procymidone and vinclozolin share a common mechanism or mode of action, a critical step in a cumulative risk assessment.

Gadd45gamma is androgen-responsive and growth-inhibitory in prostate cancer cells

In our previous microarray analysis searching for genes differentially regulated by androgens in the rat ventral prostate, we identified GADD45gamma (growth arrest and DNA damage inducible, gamma) as one of the genes up-regulated by androgens. GADD45gamma was initially identified to be a gene involved in negative growth control and its overexpression induced cycle arrest and apoptosis in vitro. In this study, we showed that GADD45gamma was transiently up-regulated by androgens in the androgen-responsive human prostate cancer cell line LNCaP. The GADD45gamma up-regulation was blocked by an androgen receptor (AR) antagonist, bicalutamide, suggesting the involvement of the androgen receptor. However, this up-regulation was inhibited by cycloheximide, indicating that GADD45gamma induction by androgens requires new protein synthesis. Overexpression of GADD45gamma inhibited cell growth of LNCaP and PC3 cells and resulted in dramatic morphological changes in both cell lines, arguing that GADD45gamma is likely to participate in the differentiation program induced by androgens in the prostate. The above observations provide evidence that GADD45gamma is an androgen-responsive gene with growth-inhibitory activity in human prostate cancer cells.

Cell death in irradiated prostate epithelial cells: role of apoptotic and clonogenic cell kill

Dose-escalated conformal radiotherapy is increasingly being used to radically treat prostate cancer with encouraging results and minimal long-term toxicity, yet little is known regarding the response of normal or malignant prostate cells to ionizing radiation (IR). To clarify the basis for cell killing during prostate cancer radiotherapy, we determined the IR-induced expression of several apoptotic- (bax, bcl-2, survivin and PARP) and G1-cell cycle checkpoint- (p53 and p21(WAF1/Cip1)) related proteins, in both normal (PrEC-epithelial and PrSC-stromal) and malignant (LNCaP, DU-145 and PC-3; all epithelial) prostate cells. For these experiments, we chose doses ranging from 2 to 10 Gy, to be representative of the 1.8-2 Gy daily clinical fractions given during curative radiotherapy and the 8-10 Gy single doses given in palliative radiotherapy. We observed that IR-induced bax and p21(WAF1/Cip1) protein expression were attenuated selectively in normal stromal and epithelial cell cultures, yet maintained their p53-dependency in malignant cell lines. For each cell culture, we also determined total apoptotic and overall radiation cell kill using a short-term nuclear morphologic assay and a long-term clonogenic survival assay, respectively. Clonogenic survival, as measured by the surviving fraction at 2 Gy (SF2), ranged from 0.05 (PrEC) to 0.55 (DU-145), suggesting that malignant prostate cells are more radioresistant than normal prostate cells, for this series. IR-induced apoptotic cell kill was minimal (less than 6% cell after a dose of 10 Gy at times of 24-96 h) and was not dose-dependent. Furthermore, apoptotic kill was not correlated with either molecular apoptotic response or clonogenic cell kill. Using a flow cytometric proliferation assay with the PrSC (stromal) and DU-145 (epithelial) representative cultures, we observed that a senescent-like phenotype (SLP) emerges within a sub-population of cells post-irradiation that is non-clonogenic. Terminal growth arrest was dose-responsive at 96 h following irradiation and associated with long-term expression of both p21(WAF1/Cip1) and p16(INK4a) genes. Future strategies for prostate radiotherapy prediction or novel treatments should additionally focus on terminal growth arrest as an important endpoint in prostate cancer therapy.

The androgen receptor: structure, mutations, and antiandrogens

Androgens play a critical role not only in the physiological development of the prostate but also in the genesis of prostate cancer. The effects of androgen on the prostate gland and on the other tissues of the body are mediated by activation of the androgen receptor. The androgen receptor is a member of the superfamily of hormone receptors with a DNA-binding site, two zinc finger domains, and a hormone-binding site. Mutations in this receptor can be associated with loss of function or chronic endogeneous activation, depending upon the site of change. Androgens effect a conformal change in the structure of the androgen receptor associated with a change in protein phosphorylation. The androgen receptor can be activated by additional ligands affecting the hormone-binding site besides androgens. Activators and repressors of the androgen receptor modify this protein's function and are very delicately balanced such that disruptions of either function are associated with a disease state. Antiandrogens, which bind to the receptor and thus down-regulate the effects of endogeneous circulating androgens, remain the first line treatment for palliation of advanced prostate cancer. Mutations in the receptor are associated with a change in function of such compounds from antagonist to agonist in vitro. Newer evidence suggests there may be a role of intermittent androgen suppression rather than continuous suppression, perhaps by preventing overgrowth of hormone independent tumor cells. Future research focuses on the development of drugs directed at suppressing the androgen drive of the androgen sensitive clone of the tumor and making the nonsensitive subset more susceptible to cytotoxics.

Gene expression profiling of androgen deficiency predicts a pathway of prostate apoptosis that involves genes related to oxidative stress

Androgens are critical for prostate development, growth, and functions. In general, they support proliferation and prevent cell death of prostatic epithelial cells. Here, we studied changes of gene expression after castration and testosterone replacement therapy in the rat ventral prostate using cDNA microarrays analysis. We could identify 230 genes that were regulated in either experimental condition. Using hierarchical clustering analysis, different groups of genes could be detected according to their expression pattern. This enabled us to distinguish the putative androgen-responsive genes from the secondary-responsive ones. Among genes that altered during castration and testosterone replacement, a set of oxidative stress-related genes, including thioredoxin, peroxiredoxin 5, superoxide dismutase 2, glutathione peroxidase 1, selenoprotein 15 kDa, microsomal glutathione-S-transferase, glutathione reductase, and epoxide hydrolase, were changed by castration. We hypothesize that modulation of redox status can be a factor of relevance in androgen withdrawal-induced prostate apoptosis. In selective cases, quantitative RT-PCR was used to confirm changes in gene expression. Immunohistochemistry was performed to detect thioredoxin and ezrin. Both of these were detected in the prostate and seem to be regulated in a similar manner as shown by gene expression analysis. In conclusion, gene expression profiling provides a unique opportunity for understanding the molecular mechanisms of androgen actions in prostate gland.

Flt3 ligand expands dendritic cell numbers in normal and malignant murine prostate

We have developed a murine model that facilitates the structural and functional analysis in vivo of dendritic cell (DC)-mediated phagocytosis of prostate epithelial cells. Recombinant human Flt3 ligand (rhFL) expands the number of dendritic cells in lymphoid and non-lymphoid tissues of mice. We show that rhFL also induced the ingress of dendritic cells into murine prostate, which involutes via epithelial apoptosis after surgical castration. Intact or castrated C57BL/6 and syngeneic transgenic adenocarcinoma of mouse prostate (TRAMP) mice were treated with rhFL or PBS control. Prostate and spleen were then studied by flow cytometry and immunohistochemistry. The number of prostatic CD11c+ and CD11b+ dendritic cells increased significantly in rhFL-treated mice compared with PBS-treated control mice and this effect was greatly augmented by castration of the mice. The immunophenotype of rhFL-mobilized prostatic cells was consistent with that of Langerhans cells (MHC class II+, CD11c+,CD11b+, DEC-205+, CD8 alpha-).MHC class II+ and CD11c+ dendritic cells that were present in the prostate glands of rhFL-treated and castrated C57BL/6 mice were intimately associated with TUNEL+ inclusions, which suggests that Langerhans-type dendritic cells in prostate participated in the clearance of apoptotic cells. Expression of MHC class II, CD54, CD80 and CD86 by prostatic dendritic cells was not up-regulated after castration and freshly isolated rhFL-induced prostate cells were unable to prime allogeneicT cells unless they were activated by culture either on plastic or with recombinant soluble CD40 ligand. Our data suggest that rhFL-mobilized prostatic dendritic cells resemble the functionally immature dendritic cells, which reside in peripheral tissues and contribute to the maintenance of peripheral tolerance.

Controversies surrounding androgen deprivation for prostate cancer

BACKGROUND

Management of metastatic prostate cancer continues to evolve. The widespread use of the prostate-specific antigen (PSA) assay has led to earlier diagnosis and earlier detection of recurrent disease. Debates continue regarding the proper use and timing of endocrine therapy with orchiectomy, estrogen agonists, luteinizing hormone-releasing hormone (LHRH) analogs, LHRH antagonists, and androgen antagonists.

METHODS

The authors reviewed the significant published materials of the last 20 years that have shaped hormonal management of metastatic and progressive prostate cancer. Major areas of controversy were also identified.

RESULTS

The present approach to hormonal management is summarized. Five potential pathways to the development of androgen-independent prostate cancer are described. Controversial topics of hormonal management, including immediate vs delayed hormonal therapy, monotherapy vs maximal androgen blockade (MAB), and intermittent hormonal therapy, are discussed.

CONCLUSIONS

Orchiectomy, estrogen agonists, and LHRH analogs have therapeutic equivalence. Patients who have a rising PSA after definitive treatment for prostate cancer and high risk of recurrent disease may warrant early androgen deprivation. MAB does not appear to be significantly better than single-agent LHRH analog therapy. Intermittent therapy may delay emergence of androgen independence and maintain or improve quality of life.

From castration-induced apoptosis of prostatic epithelium to the use of apoptotic genes in the treatment of prostate cancer

Current knowledge of the mechanisms regulating androgen-ablation-induced apoptosis is reviewed, and our efforts to develop a system in which genes of the apoptotic pathway are used to induce therapeutic apoptosis in experimental models of prostate cancer are described.

In vitro evidence for complex modes of nuclear beta-catenin signaling during prostate growth and tumorigenesis

Understanding the molecular etiology of prostate cancer (CaP) progression is paramount for broadening current diagnostic and therapeutic modalities. Current interest in the role of wnt pathway signaling in prostate tumorigenesis was generated with the finding of beta-catenin mutation and corresponding nuclear localization in primary lesions. The recent finding of beta-catenin-induced enhancement of androgen receptor (AR) function potentially ties beta-catenin to key regulatory steps of prostate cell growth, differentiation, and transformation. By immunohistological analysis of metastatic tumors, we detected nuclear beta-catenin in 20% of lethal CaP cases, suggesting a more common role for beta-catenin in advanced disease than would be predicted by its mutation rate. Interestingly, beta-catenin nuclear localization was found to occur concomitantly with androgen-induced regrowth of normal rat prostate. These in vivo observations likely implicate beta-catenin involvement in both normal and neoplastic prostate physiology, thus prompting our interest in further characterizing modes of beta-catenin signaling in prostate cells. Extending our previous findings, we demonstrate that transient beta-catenin over-expression stimulates T cell factor (TCF) signaling in most CaP cell lines. Further, this activity is not subject to cross-regulation by phosphoinositide-3-kinase (PI3-K)/Akt signaling, a stimulatory pathway often upregulated in CaP upon PTEN inactivation. Consistent with a previous report, we observed that transient beta-catenin over-expression enhances AR-mediated transcription off two natural target gene promoters. However, we were unable to recapitulate beta-catenin-induced stimulation of ectopically expressed AR in AR-negative cells, suggesting that other AR-associated factors are required for this activity. Although LNCaP cells are capable of this mode of AR co-stimulation, stable expression of mutant beta-catenin did not alter their proliferative response to androgen. In total, our characterization of beta-catenin signaling in CaP reveals the complex nature of its activity in prostate tissue, indicating that beta-catenin potentially contributes to multiple stimulatory inputs required for disease progression.

The effect of drugs and toxins on the process of apoptosis

In this review we examine the modifying effect of specific drugs on apoptosis. Apoptosis is a type of cell death prevalent during many physiological and pathological conditions, consisting of several steps, namely, initiating stimuli, transduction pathways, effector mechanisms, nuclear fragmentation, and phagocytosis. Pharmacological substances such as glucocorticoids can either induce or inhibit the process of apoptosis in various cells depending on the type of drug and its concentration. Understanding the mechanisms of interaction of drugs with cells undergoing apoptosis could encourage novel therapeutic approaches to human diseases in which apoptosis has a critical role.

Association between the severity of heart failure and the susceptibility of myocytes to apoptosis in patients with idiopathic dilated cardiomyopathy

BACKGROUND

Bcl-2 proto-oncogene, an inhibitor of apoptosis and Bax proto-oncogene, an inducer of apoptosis play critical roles in the molecular circuit controlling apoptosis in cardiac muscle. The ratio of Bax to Bcl-2 proto-oncogene determines survival or death after an apoptotic stimulus. We speculated that susceptibility of myocytes to apoptosis determined as the Bax/Bcl-2 ratio might vary with the severity of heart failure.

METHODS AND RESULTS

We studied immunohistochemically 108 endomyocardial biopsy specimens from 30 patients with idiopathic dilated cardiomyopathy (mild heart failure, n=14; moderate or severe heart failure, n=16) with the use of Bcl-2 and Bax monoclonal antibodies. The expression of each protein was determined semiquantitatively as the fraction of myocytes labeled with specific monoclonal antibodies using a digital morphometric analysis system. Patients with mild heart failure showed significantly increased Bax/Bcl-2 ratio than the patients with advanced heart failure (1.59+/-1.26 vs. 0.34+/-0.43, P=0.002). The expression of Bcl-2 was found to be independent of the severity of heart failure whereas the expression of Bax was significantly higher in patients with mild heart failure compared to the patients with moderate or severe heart failure (52.1+/-29.3 vs. 21.6+/-22.4%, P=0.005). Additionally, Bax/Bac-2 ratio was inversely correlated with the mitral E-interventricular septum distance, left ventricular end-systolic and end-diastolic diameter.

CONCLUSION

The susceptibility of myocytes to apoptosis is significantly increased in the early phase of heart failure but it decreases with worsening of the disease due to depressed expression of Bax onco-protein. Increased myocyte susceptibility to apoptosis may have a role in the transition from mild heart failure to severe in patients with idiopathic dilated cardiomyopathy.

Apoptosis and Fas-ligand expression correlate to the histopathological grade of gastric smooth muscle tumors

BACKGROUND

Apoptosis is associated with the tumor grade in various types of carcinomas or lymphomas, but less is understood about the association of apoptosis in mesenchymal tumors. In the prior studies, expression of apoptotic regulatory proteins, Bcl-2, Fas and its ligand, Fas-ligand, has been related to apoptotic index (AI) and histopathological grade of tumors. Our study investigated the incidence of apoptosis in gastric smooth muscle tumor and the correlation of the apoptotic index (AI) with the histopathological grade of the tumors. We evaluated the relationship of apoptotic regulatory proteins to the AI and tumor grade.

METHODS AND MATERIALS

Using immunohistochemistry and the terminal deoxynucleotidyl transferase (TdT)-mediated digoxigenin-dUTP nick end-labeling (TUNEL) assay, we analyzed the expression of Bcl-2, Fas, Fas-ligand, and AI in 26 cases of gastric smooth muscle tumors.

RESULTS

The incidence of greater than 10 apoptotic cells per 10 high-power fields (HPFs) was 73% (19/26 cases). The AI was significantly associated with malignant tumors (P = 0.006) and mitotic counts (P = 0.006) but not with tumor size. Bcl-2, Fas, and Fas-ligand were detected in 13 (50%), 14 (53.8%), and 19 (73%) cases, respectively. Interestingly, Fas-ligand was significantly correlated to malignancy (P = 0.006), mitotic counts (P = 0.006), and AI (P = 0.035) but not to tumor size. Fas expression was significantly associated with high levels of AI (P = 0.014). In contrast, Bcl-2 expression was inversely associated with AI (P = 0.004). Expression of Bcl-2 and Fas did not show a statistically significant correlation with tumor grade, mitotic counts, or tumor size.

CONCLUSION

Apoptosis and Fas-ligand expression are statistically correlated to the histopathological grade of gastric smooth muscle tumors. This suggests that detection of apoptotic cells and Fas-ligand expression using the TUNEL assay or immunohistochemistry are useful for the evaluation of the malignant potential of gastric smooth muscle tumors.

John Kerr and apoptosis

On 14 March 2000, John Foxton Ross Kerr, Emeritus Professor of Pathology at the University of Queensland, received the Paul Ehrlich and Ludwig Darmstaedter Prize for his description of apoptosis, a form of cell death. The prize, which he shared with Boston biologist Robert Horvitz, is considered to be one of the most prestigious European awards in science, second only to the Nobel Prize.

Intermittent androgen deprivation

Intermittent androgen deprivation is a controversial approach to management of prostate cancer. Preclinical models have demonstrated delay in time to prostate-specific antigen (PSA) progression in athymic mice bearing LNCaP tumors and a delay in time to androgen independence in androgen-dependent Shionogi carcinoma tumors in castrated animals exposed to intermittent androgen. Phase II clinical trials have demonstrated improved sexual function and quality of life in men discontinuing androgen deprivation. The average percentage of time spent off androgen deprivation ranges from 37% to 58%. Most men respond to retreatment with hormonal therapy. Current ongoing phase III clinical trials of intermittent versus continuous androgen deprivation in men with metastatic disease or recurrent disease after localized therapy will assess the comparative impact on quality of life and survival. Final analyses of these critical trials will define the ultimate role of this approach in prostate cancer. In the interim, intermittent androgen deprivation should be considered an experimental approach.

Hormonal regulation of physiological cell turnover and apoptosis

Physiological cell turnover plays an important role in maintaining normal tissue function and architecture. This is achieved by the dynamic balance of cellular regeneration and elimination, occurring periodically in tissues such as the uterus and mammary gland, or at constant rates in tissues such as the gastrointestinal tract and adipose tissue. Apoptosis has been identified as the prevalent mode of physiological cell loss in most tissues. Cell turnover is precisely regulated by the interplay of various endocrine and paracrine factors, which modulate tissue and cell-specific responses on proliferation and apoptosis, either directly, or by altering expression and function of key cell proliferative and/or death genes. Although recent studies have provided significant information on specific tissue systems, a clearly defined pathway that mediates cell turnover has not yet emerged for any tissue. Several similarities exist among the various tissues with regard to the intermediates that regulate tissue homeostatis, enabling a better understanding of the general mechanisms involved in the process. Here we review the mechanisms by which hormonal and cytokine factors mediate cell turnover in various tissues, emphasizing common themes and tissue-specific differences.

Immunohistochemical localization of interleukin-1beta, interleukin-1 receptor antagonist and interleukin-1beta converting enzyme/caspase-1 in the rat brain after peripheral administration of kainic acid

The temporal and anatomical distribution of members of the interleukin-1 system in the rat brain following intraperitoneal kainic acid administration was studied in relation to neurodegeneration as detected with in situ end labelling. Kainic acid administration (10 mg/kg, i.p.) resulted in the induced expression of interleukin-1beta, interleukin- receptor antagonist and caspase-1p10 immunoreactivity in areas known to display neuronal and tissue damage upon excitotoxic lesions. The induction of these proteins was transient. Interleukin-1 immunoreactivity appeared at 5 h, and the interleukin-1 receptor antagonist-immunoreactive cells were first detected at 12 h, whereas the induction of caspase- 1p10 expression was first detected 24 h after kainic acid injection. Double labelling with the microglial marker Ox42 confirmed that both interleukin-1beta and interleukin-1 receptor antagonist were mainly localized in microglial cells. The regional distribution of in situ end-labelled neurons was similar to the distribution of cells expressing interleukin-1beta and interleukin-1 receptor antagonist, whereas the distribution of caspase-1 was more limited. The in situ end-labelled neurons, were, similarly to the interleukin-1beta-positive cells, first detected at 5 h, which is earlier than the induction of caspase-1. Our results show that the induction of IL-1beta and IL-1 receptor antagonist proteins after kainic acid are closely associated with the temporal as well as the anatomical distribution of in situ end-labelled neurons, whereas the induction of caspase-1 protein exhibited a delayed temporal profile and limited distribution. Since cytokine production occurs in activated microglial cells, the inflammatory component seems to be a strong mediator of this type of excitotoxic damage. The late onset of the caspase-1 expression would seem to indicate that this enzyme has no fundamental role in directly causing neuronal cell death induced by systemic kainic acid.

Fas antigen/CD-95 upregulation and activation during castration-induced regression of the rat ventral prostate gland

BACKGROUND

Fas antigen/CD 95 is a 45-kDa transmembrane protein that can initiate intracellular signaling pathways, leading to apoptosis when it is clustered on the cell surface. A recent report claiming that the ventral prostate glands of lpr -/- mutant mice (lacking functional fas antigen) do not regress following castration prompted our analysis of the regressing rat ventral prostate gland for evidence that fas antigen might participate in the molecular process leading to prostate cell apoptosis after castration.

METHODS

An RNase protection assay and Western blotting analysis were used to quantify fas antigen mRNA and protein expression in the regressing rat ventral prostate gland. Immunoprecipitates of fas antigen from membrane preparations made from control or castrated rat prostates were analyzed for coprecipitation of FADD and RIP proteins to assess the activation state of the fas antigen before and after castration. Finally, prostate tissues obtained from two different strains of lpr -/- mutant mice were analyzed for induced apoptosis after castration by the TUNEL staining method.

RESULTS

Rat ventral prostate gland fas antigen mRNA and protein expression was upregulated approximately 3-5-fold in the 3-day castrated rat as compared to hormonally intact rats. Immunoprecipitates of fas antigen from membranes of ventral prostates from castrated rats contained significantly increased amounts of both FADD and RIP proteins when compared to those of intact or control operated rats. However, counts of TUNEL-labeled cells in the ventral prostate glands of castrated lpr -/- mice were not significantly different from those in castrated, genetically normal controls. Likewise, the morphology of apoptotic bodies formed in the prostates of castrated lpr -/- mice was indistinguishable from that in control animals.

CONCLUSIONS

Fas antigen/CD-95, a protein that is involved in some forms of apoptosis, is upregulated during regression of the rat ventral prostate gland and becomes functionally "activated." However, our inability to distinguish any difference in the apoptosis rate or in the morphology of the apoptotic bodies formed in response to castration between lpr -/- mice and genetically normal controls indicates that, contrary to the prior report, functional fas protein is not required for castration-induced prostate cell apoptosis.

Expression of p190A during apoptosis in the regressing rat ventral prostate

After hormonal ablation, 90% of the secretory epithelial cells of the prostate undergo apoptosis, and the remaining cells are reorganized as the tissue is remodeled. Using differential display RT-PCR of total RNA extracted from the rat ventral prostate before and 4 days after castration, we have cloned and sequenced a number of complementary DNAs whose cognate messenger RNAs (mRNAs) may be either up- or down-regulated during prostatic regression. One sequence of particular interest, 25.2, is up-regulated after castration and is homologous to p190, a protein associated with cytoskeletal reorganization. RT-PCR has confirmed that the steady state level of p190A mRNA is increased in the rat ventral prostate after castration, and Western blot analysis indicates that the protein levels for p190A also increase. The steady state level of p190B mRNA, the second isoform of p190, does not appear to change significantly after hormone ablation. Immunohistochemical analysis demonstrates that p190A is up-regulated primarily in the columnar epithelial cells that actively undergo cell death after hormone ablation. As Rho-GAP signaling had been shown to be influenced by p190 levels, leading to the disassembly of focal adhesion contacts and the loss of cytoskeletal architecture, we also measured the changes in Rho-GAP during prostate regression. Rho-GAP levels do not change significantly, suggesting that changes in stoichiometry of the interaction between p190A and Rho-GAP may be a prerequisite for the initiation of cytoplasmic condensation. These intracellular events coupled with the proteolytic degradation of the extracellular matrix appear to be integral to the apoptotic process in glandular epithelia.

Early effects of castration on the vascular system of the rat ventral prostate gland

Recent studies have found that blood flow to the rat ventral prostate gland is drastically reduced at an early time after castration. These observations caused us to reevaluate the effects of castration on the various cell populations of the ventral prostate, especially those in the prostatic vascular system. Sections of ventral prostate glands obtained at different times after castration were analyzed using the TUNEL (terminal deoxynucleotide transferase-mediated dUTP nick END labeling) staining method to quantify apoptosis in different cell types. The results of this analysis showed a significant increase in TUNEL staining of prostate endothelial and (nonendothelial) stromal cells as early as 12 h postcastration that continued to 24 h after castration. In contrast, TUNEL labeling of prostate epithelial cells was not significantly increased compared with control values until 72 h after castration. The use of dual immunohistochemical staining procedures (anti-CD31 for endothelial cells or antismooth muscle actin for smooth muscle cells combined with TUNEL labeling) allowed us to confirm that the TUNEL-positive vascular cells at these early times after castration were endothelial in nature, whereas smooth muscle cells surrounding the prostate glands or portions of the afferent vascular endothelium were rarely TUNEL labeled. Electron microscopic evaluation of ventral prostate tissues at 48 h after castration provided further morphological evidence for the occurrence of apoptosis in prostate endothelial cells. Finally, the Lendrum-Fraser histochemical procedure used to identify fibrin leakage in tissues with vascular damage was applied to sections of the ventral prostate gland. This stain revealed diffuse fibrin accumulation in periglandular areas outside the capillaries and blood vessels in prostates from 24-h castrated rats, but not in prostates of sham-operated rats. Our results confirm an early effect of castration on the vascular system of the rat ventral prostate identified by increased apoptosis of endothelial cells and vascular leakiness. As these changes temporally precede the loss of epithelial cells, we propose that they may be causal rather than incidental to regression of the rat ventral prostate after castration.