Effect of castration, DES, flutamide, and the 5 alpha-reductase inhibitor, MK-906, on the growth of the Dunning rat prostatic carcinoma, R-3327

Relative binding affinity of novel steroids to androgen receptors in hamster prostate

The in vivo and in vitro antiandrogenic activity of four aromatic esters 10a-10d, one aliphatic ester 10e based on the pregna-4,16-diene-6, 20-dione structure and two aromatic 17c, 17d and two aliphatic valeroyloxy esters 17a, 17b based on the more saturated 4-pregnene-6,20-dione skeleton was examined. The biological activity of steroids 9, 10a-10e and 17a-17d, was determined using prostate glands from gonadectomized adult male golden hamsters. In the in vitro studies, the relative binding affinity of these steroids to cytoplasmic androgen receptor (AR) of hamster prostate was determined from, the corresponding IC50 values obtained from the competitive binding plots. The standards dihydrotestosterone (DHT) and cyproterone (CA) acetate used have displaced [3H]DHT from the AR with an IC50 value of 3.2 and 4.4 nM respectively. All steroidal compounds synthesized in this study showed a binding affinity for the androgen receptor, present in the cytosol from prostate hamster; compounds 10a-10c showed the highest affinities for this receptor. The in vivo experiments showed that all steroidal derivatives were subcutaneously active, since they decreased the weight of the prostate gland in gonadectomized hamsters treated with DHT, and are antagonists for the androgen receptor since they block the DHT-induced prostate weight gain. The derivatives having the more conjugated 4,16-pregnadiene-6, 20-dione system (10a-10c) exhibited a higher antiandrogenic activity than the corresponding steroids (17a-17d) based on the more saturated 4-pregnene-6,20-dione system.

New Aromatic Esters of Progesterone as Antiandrogens

The in vivo and in vitro antiandrogenic activity of four new progesterone derivatives: 4-bromo-17alpha-(p-fluorobenzoyloxy)-4-pregnene-3,20-dione 1,4-bromo-17alpha-(pchlorobenzoyloxy)-4-pregnene-3,20-dione 2, 4-bromo-17alpha-(p-bromobenzoyloxy)-4-pregnene-3,20-dione 3 and 4-bromo-17alpha-(p-toluoyloxy)-4-pregnene-3, 20-dione 4 was determined. These compounds were evaluated as antiandrogens on gonadectomized hamster prostate and reduced the weight of the prostate glands in gonadectomized hamsters treated with testosterone 5 (T) or dihydrotestosterone 6 (DHT) in a similar manner to that of commercially available finasteride, thus indicating a potent in vivo effect. The in vitro studies showed that steroids 1-4 have a weak inhibitory activity on 5alpha-reductase with IC50 values of: 280 (1), 2.6 (2), 1.6 (3) and 114 microM (4). The presence of Cl and Br atoms in the C-17 benzoyloxy group tends to increase the inhibitory potency of the compounds. The binding efficiency of the synthesized steroids 1-4 to the androgen receptor of the prostate gland is also evaluated. All compounds form a complex with the receptor and this explains the weight reduction of the seminal vesicles in the animals treated with DHT plus steroids 1-4.

The effects of 5alpha-reductase inhibitors on the natural history, detection and grading of prostate cancer: current state of knowledge

PURPOSE

The Prostate Cancer Prevention Trial (PCPT) showed that the 5alpha-reductase inhibitor (5ARI) finasteride significantly decreased the 7-year period prevalence of prostate cancer vs placebo. However, Gleason score 7-10 tumors were significantly more common in the finasteride vs the placebo group. We considered data on the effects of 5ARIs on prostate cancer natural history and detection.

MATERIALS AND METHODS

A detailed review was performed of the literature identified from the MEDLINE database examining the effects of 5ARIs on prostate cancer prevalence and tumor histopathology.

RESULTS

In PCPT there were fewer biopsies performed for cause in the finasteride vs the placebo group and the proportion of high grade tumors in the treatment groups did not diverge with time. Given that finasteride has an effect on prostate specific antigen and prostate volume, which are key factors in triggering prostate biopsies, they may be significant confounders of Gleason score results. Prostate shrinkage in the finasteride treated group may minimize biopsy sampling error. Furthermore, histological studies have shown that 5ARIs have a significant effect on prostate architecture, which can make the interpretation of prostate specimens in men treated with 5ARIs difficult. Further evaluation of PCPT findings will help determine the true nature of these observations.

CONCLUSIONS

5ARIs decrease the risk of prostate cancer but also alter the detection of disease through effects on prostate specific antigen, and prostate volume and histology. The weight of evidence suggests an artifactual effect of finasteride on Gleason grading in the PCPT. The role of 5ARIs for prostate cancer chemoprevention needs further examination before it can be considered for wide recommendation.

Pharmacologic Basis for the Enhanced Efficacy of Dutasteride against Prostatic Cancers

PURPOSE

Prostatic dihydrotestosterone (DHT) concentration is regulated by precursors from systemic circulation and prostatic enzymes of androgen metabolism, particularly 5alpha-reductases (i.e., SRD5A1 and SRD5A2). Therefore, the levels of expression SRD5A1 and SRD5A2 and the antiprostatic cancer growth response to finasteride, a selective SRD5A2 inhibitor, versus the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, were compared.

EXPERIMENTAL DESIGN

Real-time PCR and enzymatic assays were used to determine the levels of SRD5A1 and SRD5A2 in normal versus malignant rat and human prostatic tissues. Rats bearing the Dunning R-3327H rat prostate cancer and nude mice bearing LNCaP or PC-3 human prostate cancer xenografts were used as model systems. Tissue levels of testosterone and DHT were determined using liquid chromatography-mass spectrometry.

RESULTS

Prostate cancer cells express undetectable to low levels of SRD5A2 but elevated levels of SRD5A1 activity compared with nonmalignant prostatic tissue. Daily oral treatment of rats with the SRD5A2 selective inhibitor, finasteride, reduces prostate weight and DHT content but did not inhibit R-3327H rat prostate cancer growth or DHT content in intact (i.e., noncastrated) male rats. In contrast, daily oral treatment with even a low 1 mg/kg/d dose of the dual SRD5A1 and SRD5A2 inhibitor, dutasteride, reduces both normal prostate and H tumor DHT content and weight in intact rats while elevating tissue testosterone. Daily oral treatment with finasteride significantly (P < 0.05) inhibits growth of LNCaP human prostate cancer xenografts in intact male nude mice, but this inhibition is not as great as that by equimolar oral dosing with dutasteride. This anticancer efficacy is not equivalent, however, to that produced by castration. Only combination of dutasteride and castration produces a greater tumor inhibition (P < 0.05) than castration monotherapy against androgen-responsive LNCaP cancers. In contrast, no response was induced by dutasteride in nude mice bearing androgen-independent PC-3 human prostatic cancer xenografts.

CONCLUSIONS

These results document that testosterone is not as potent as DHT but does stimulate prostate cancer growth, thus combining castration with dutasteride enhances therapeutic efficacy.

Differential alterations in 5alpha-reductase type 1 and type 2 levels during development and progression of prostate cancer

BACKGROUND

In the prostate, conversion of testosterone to dihydrotestosterone (DHT), by the enzymes 5alpha-reductase types 1 and 2 (5alphaR1, 5alphaR2) is required for normal growth and probably also for development of prostate cancer (PCa). Finasteride, a 5alphaR2 inhibitor, was shown to reduce the prevalence of PCa in the Prostate Cancer Prevention Trial. However, inhibition of both 5alphaR isoenzymes causes a greater decrease in serum DHT. The aim of this study was to assess differential expression of these enzymes at various stages of PCa development.

METHODS

Immunostaining for 5alphaR1 and 5alphaR2, using specific, well-validated antibodies, was evaluated in 26 benign prostatic hyperplasia (BPH) (16 for 5alphaR2), 53 primary PCa (21 for 5alphaR2), 18 prostatic intraepithelial neoplasia (PIN), 12 primary PCa treated with neoadjuvant androgen ablation, 15 locally recurrent PCa specimens, and 18 PCa metastases.

RESULTS

The mean area of moderate plus high intensity staining for 5alphaR1 increased from 4.8 +/- 2.8% of total epithelial area in BPH, to 18.9 +/- 5.7% in PIN, 17.0 +/- 3.2% in primary cancer, 38.0 +/- 7.3% in recurrent cancer, and 55.8 +/- 8.5% in PCa metastases. The mean staining area for 5alphaR2 decreased from 58.8 +/- 7.2% in BPH, to 21.1 +/- 5.5% in PIN and 34.8 +/- 6.7% in primary PCa. Staining for 5alphaR2 was increased in recurrent cancer and PCa metastases compared to primary PCa, at 58.7 +/- 5.2% and 69.2 +/- 8.7%, respectively.

CONCLUSIONS

5alphaR1 immunostaining is increased and 5alphaR2 immunostaining is decreased during development of PCa. In addition, there is increased expression of both 5alphaR isozymes in recurrent and metastatic cancers, suggesting that both isozymes may be important in the development and progression of PCa.

Biochemical recurrence after definitive prostate cancer therapy. Part II: Treatment strategies for biochemical recurrence of prostate cancer*

PURPOSE OF REVIEW

Through the prostate-specific antigen era, the proportion of men less than 55 years old with newly diagnosed prostate cancer more than doubled to almost 15%. As increasing numbers of men are living longer with prostate cancer, larger proportions will eventually present to our collective practices with rising prostate-specific antigen levels. Such prostate-specific antigen relapses, conservatively estimated to affect approximately 50 000 men each year, have become the most common form of advanced prostate cancer in the current period.

RECENT FINDINGS

Increasing evidence suggests that early hormonal therapy improves progression-free survival and may alter the cancer-specific survival. However, there is a cost to pay in side-effects when androgen deprivation is administered over prolonged periods. The non-steroidal anti-androgen bicalutamide may offer an equivalent progression-free survival to castration without the complications of androgen deprivation. Observational data seem to indicate that high-risk individuals (i.e. those with high-grade, high-stage disease or a prostate-specific antigen doubling time less than 12 months) may also receive benefit from early therapy.

SUMMARY

The definition of advanced prostate cancer has changed. Multimodal therapy improves cancer-specific outcomes especially in men with high-risk disease. The potential opportunities for novel therapeutic agents with low associated morbidity are great.

Gleason grade remains an important prognostic predictor in men diagnosed with prostate cancer while on finasteride therapy

OBJECTIVE

To evaluate men treated with finasteride for lower urinary tract symptoms, who subsequently were diagnosed with prostate cancer and had a radical prostatectomy (RP) at our institution, to determine if finasteride therapy prevented accurate Gleason grade assignment and prediction of biochemical recurrence.

PATIENTS AND METHODS

Between May 1996 and July 2003, 45 men were identified who had RP and had previously been treated with finasteride for > or = 6 months before the diagnosis of prostate cancer. Clinical and pathological information was gathered from a RP database. Serum prostate-specific antigen (PSA) level, duration of finasteride therapy, biopsy Gleason grade, clinical stage, RP Gleason grade and pathological stage were reviewed. Freedom from recurrence was predicted using validated nomograms before and after RP, and compared against actuarial 5-year freedom from recurrence using the Kaplan-Meier method. RESULTS The mean duration of finasteride therapy before diagnosis was 23.6 months, the mean serum PSA (doubled to account for finasteride use) 11.02 ng/mL and mean biopsy Gleason score 6. When comparing the biopsy and RP specimen Gleason score, it was downgraded by 1 point in six men, upgraded by 1 point in eight, and upgraded by 2 points in one. The Gleason score was constant in 30 patients. The nomograms predicted freedom from recurrence in 83% and 85%, respectively; the 5-year actuarial freedom from recurrence was 86%.

CONCLUSION

Finasteride does not appear to compromise the assignment of Gleason grade for use in prediction tools before or after RP in men undergoing prostate biopsy or RP. The actuarial 5-year freedom from recurrence was similar to that predicted by the validated nomograms. Gleason grade remains an important prognostic predictor in men treated with finasteride and undergoing RP for clinically localized prostate cancer.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Decreased gene expression of steroid 5 alpha-reductase 2 in human prostate cancer: implications for finasteride therapy of prostate carcinoma

BACKGROUND

Steroid 5alpha-reductase 2 (SRD5A2) catalyzes the conversion of testosterone to the more potent androgen, DHT, in the prostate. The therapeutic influence of SRD5A2 inhibitor finasteride on prostate cancer is currently unknown. The direction and extent of changes in SRD5A2 expression in disease tissues is a relevant issue in this regard.

METHODS

The expression differences of SRD5A2 in tissues representative of normal, benign, and malignant growth in the human prostate were examined in parallel by comparative analysis of relevant microarray gene expression data. Semiquantitative RT-PCR was used to further verify the gene expression differences of SRD5A2.

RESULTS

Consistently decreased expression of SRD5A2 was observed in 25 prostate cancer samples when compared to 25 matched normal samples and nine BPH samples. Expression differences among these samples for six other genes were presented in parallel as indicators of the direction and extent of expression changes. These additional genes include SRD5A1, Hepsin (overexpressed in prostate cancer), AMACR (overexpressed in prostate cancer), Keratin 8 (epithelial marker), smooth muscle actin (stromal marker), Nell2 (overexpressed in BPH). Semiquantitative RT-PCR verified the expression differences for SRD5A2 in six normal, six BPH, and six prostate cancer samples.

CONCLUSIONS

Results from this study, combined with those from previous studies, indicate an association of prostate cancer with reduced 5alpha-reductase enzymatic activity as a result of remarkably decreased expression of the SRD5A2 gene. The implications of this study for finasteride therapy of prostate cancer are discussed.

Variables in predicting survival based on treating "PSA-only" relapse

Prostate cancer recurrence (after prior local treatment) that is detectable only by a rise in serum prostate specific antigen (PSA) level is a very common problem facing clinicians. Given that the majority of contemporary era men with PSA-only or biochemical recurrence are relatively young and otherwise healthy, treatment requires approaches that both improve clinical outcomes and preserve quality of life. Treatment is in one of two broad categories, additional local therapies, termed "salvage" local therapy and systemic therapies. For radical prostatectomy patients, salvage external beam radiotherapy to the prostate bed is commonly employed, being reserved for early biochemical recurrence in men with low risk at distant metastases. For primary radiation patients, salvage radical prostatectomy or cryotherapy can similarly be used for those men felt not to harbor distant metastases. Systemic therapy generally involves hormonal therapy. Traditional hormonal therapy (orchiectomy, luteinizing hormone-releasing hormone agonists, or maximum androgen blockade) is the current mainstay of systemic treatment for biochemical recurrence, although nontraditional approaches, such as antiandrogen monotherapy, are increasingly being used. Variables in predicting survival based on treating PSA relapse is problematic. The condition of biochemical failure has only been recognized in the last decade and few "PSA-era" patients with biochemical recurrence have actually died of disease. Hence, the validation of prediction variables in this setting is just emerging. Early work would suggest that timing of recurrence, Gleason grade, and PSA velocity or doubling time during relapse are important prognostic factors. New data on PSA doubling time will be presented.

Estradiol alleviates acinar cell apoptosis and chronic pancreatitis in male Wistar Bonn/Kobori rats

AIMS

To quantitatively determine the influence of estradiol on acinar cell apoptosis and chronic pancreatitis; assess its effects on infiltration of CD4 and CD8 T cells in the pancreas; investigate the role of testosterone on chronic pancreatitis in 20-week-old male WBN/Kob rats; and determine the impact of estradiol on proliferation of splenocytes derived from these animals in vitro.

METHODOLOGY AND FINDINGS

Treatment with high (0.4 mg x kg x week) but not low (0.1 mg x kg x week) doses of estradiol for 10 weeks significantly decreased the number of apoptotic acinar cells stained with an anti-single strand DNA antibody, histologic scores, and pancreatic myeloperoxidase activity in 20-week-old WBN/Kob rats, in comparison with control values. The high doses also significantly attenuated the increase in pancreatic hydroxyproline content, an indicator of collagen deposition, at 20 weeks. They caused significant decreases in the numbers of CD4 and CD8 T cells infiltrating the pancreas. Both doses suppressed levels of testosterone but without any influence on the serum corticosterone concentrations. Androgen receptors could not be immunohistochemically identified in the pancreas at 20 weeks, and dietary treatment with flutamide, an androgen receptor antagonist, did not influence the chronic pancreatitis. Estradiol significantly reduced 1% phytohemagglutinin-induced incorporation of bromodeoxyuridine into the splenocytes in vitro.

CONCLUSIONS

We conclude that estradiol dose-dependently attenuates acinar cell apoptosis and development of chronic pancreatitis, independent of any change in endogenous corticosterone and testosterone, by suppressing infiltration and function of T cells.

PSA progression following radical prostatectomy and radiation therapy: new standards in the new Millennium

Prostate-specific antigen (PSA) progression following radical treatments of clinically localized prostate cancer is a common problem facing both the patient and the urologist. Not all patients with relapsing disease have an equal risk of death due to prostate cancer. After surgery, biochemical failure can be defined as persisting detectable levels of PSA after radical prostatectomy or a PSA rise after a period of normalization. On the other hand, definitions of PSA progression after radiation therapy vary and no clear consensus can be found. This review of the recent international literature updates the knowledge about the diagnostic procedures used in relapsing patients. Predictors of progression are precised leading to a better patient selection, based on currently available tables and nomograms. Indeed, identification of high risk patients may allow a more appropriate treatment decision. After radical treatment, the analysis of time to recurrence, PSA doubling time, PSA kinetics combined to modern imaging techniques such as 111In capromab penditide scan may allow a better identification of the recurrence site. Thus, an optimal treatment strategy may be envisaged such as local irradiation, salvage surgery, hormone therapy or combinations for which indications and results are provided. Alternative options such as cryotherapy still need further investigation. At last, the use of artificial neural networks will certainly enhance the selection of patients submitted to radical treatments as well as the selection of relapsing patients to allow a more appropriate adjuvant therapy.

New progesterone esters as 5alpha-reductase inhibitors

The pharmacological activity of four new progesterone derivatives: 4-bromo-17alpha-(p-fluorobenzoyloxy)-4-pregnene-3,20-dione (7), 4-bromo-17alpha-(p-bromobenzoyloxy)-4-pregnene-3,20-dione (8), 4-bromo-17alpha-(p-chlorobenzoyloxy)-pregnene-3,20-dione (9) and 4-bromo-17alpha-(p-toluoyloxy)-4-pregnene-3,20-dione (10) was determined. These compounds were evaluated as 5alpha-reductase inhibitors on gonadectomized hamster seminal vesicles and flank organs. The pharmacological data of this study indicate that compounds 7 and 9 having at C-17 p-fluorobenzoyloxy and p-chlorobenzoyloxy ester functions respectively showed the highest antiandrogenic effect as measured by the reduction of the weight of the seminal vesicles. In the flank organ model, the same compounds 7 and 9 exhibited a smaller diameter, 1.8 and 1.0 mm, respectively, than the commercially available finasteride 3 (2.3 mm), thus indicating a higher inhibitory effect on 5alpha-reductase enzyme. Steroid 7 showed a higher inhibitory activity on the conversion of T to DHT (Fig. 3) than the presently used finasteride, thus indicating a higher antiandrogenic effect. The nonsubstituted benzoyloxy ester (compound 15) showed a lower antiandrogenic activity as measured in the seminal vesicles model than the p-substituted benzoyloxy compounds.

Does long-term finasteride therapy affect the histologic features of benign prostatic tissue and prostate cancer on needle biopsy? PLESS Study Group. Proscar Long-Term Efficacy and Safety Study

OBJECTIVES

Finasteride, a common agent used to treat benign prostatic hyperplasia (BPH), inhibits 5-alpha-reductase. Testosterone is converted by 5-alpha-reductase to the more potent dihydrotestosterone, which is the primary androgen in the prostate. Leuprolide is a stronger antiandrogen that is used to downstage prostate cancer before radical prostatectomy. Leuprolide induces marked atrophy of prostate carcinoma cells, which sometimes makes pathologic diagnosis of cancer difficult, although evaluation at radical prostatectomy is easier than at biopsy. It is unknown whether finasteride produces similar changes, which would result in greater diagnostic difficulty because such changes would be seen on biopsy to rule out cancer in men with suspicious clinical findings treated for BPH. The current study investigated the histologic effects of finasteride therapy on human prostate cancer and benign prostatic tissue on needle biopsy.

METHODS

In blinded manner, we reviewed 53 needle biopsy specimens showing prostate carcinoma (35 treated with finasteride, 18 with placebo). Also reviewed in blinded manner were 50 benign needle biopsy specimens (25 treated with finasteride, 25 with placebo). The Gleason score, number of cores involved, percentage cancer involvement in a core, percentage of atrophic changes in cancer cells, presence of mitoses, blue-tinged mucinous secretions, prominent nucleoli, and high-grade prostatic intraepithelial neoplasia were documented for each case in the cancer group. The percentage of atrophy, basal cell hyperplasia, transitional metaplasia, chronic inflammation, and stromal proliferation was documented for each case in the benign group.

RESULTS

No significant histologic differences were present in either the benign or cancer group between cases treated with finasteride and placebo.

CONCLUSIONS

We conclude that finasteride treatment for BPH does not cause difficulty in the diagnosis of cancer in prostate needle specimens. It is possible that there are severely atrophic areas resulting from finasteride treatment that are undersampled. However, the conclusion that cancer seen on needle biopsy in men treated with finasteride is unaltered and readily identified as cancer remains valid.

The effect of finasteride on the prostate gland in men with elevated serum prostate-specific antigen levels

Prostate cancer is a disease associated with androgens. It has been hypothesized that reducing the conversion of testosterone (T) to dihydrotestosterone (DHT) in the prostate by the use of the drug finasteride, a 5alpha-reductase inhibitor, will reduce the incidence of prostate cancer. We investigated the chemopreventive potential of finasteride by evaluating its effect on the prostate gland of men with elevated serum prostate-specific antigen (PSA). Fifty-two men with elevated PSA and prostate sextant biopsies negative for cancer were randomized to receive finasteride 5 mg day(-1) (27 patients) or no medication (25 patients) for 12 months and were rebiopsied at 12 months. The biopsies were evaluated for the presence of cancer, the proportion of glandular and hyperplastic tissue, and the presence of high-grade prostatic intraepithelial neoplasia (PIN). Epithelial proliferation was assessed in the prestudy and 12-month biopsies by immunohistochemistry using antibody to proliferating cell nuclear antigen (PCNA). Serum blood samples were drawn at baseline and after 1, 3, 6 and 12 months of study. In the control group, serum levels of PSA and T were unchanged throughout the 12 months. In the finasteride group, PSA decreased 48% (P < 0.001), DHT decreased 67% (P < 0.001) and T increased 21% (P < 0.001). Histological evaluation of prestudy and 12-month biopsy specimens revealed that the finasteride group had a 30% reduction in the percentage of hyperplastic epithelial tissue (P = 0.002), although this decrease was not statistically significantly different between the finasteride and control groups (P = 0.11). In patients with PIN on prestudy biopsy, no change occurred in the PIN lesions with finasteride treatment. Finasteride also had no effect on the proliferation index of prostatic epithelial cells. Of the 27 patients treated with finasteride, eight (30%) had adenocarcinoma of the prostate detected on the 12-month biopsy, compared with one (4%) of the control patients (P = 0.025). In the treatment group, six cancers occurred in the eight patients with PIN on the prestudy biopsy; in the observation group no cancers were detected in the five patients with PIN on the prestudy biopsy (P = 0.021). Two cancers occurred in the 19 men in the treatment group with no evidence of PIN on the prestudy biopsy, compared with one cancer in the 20 men in the observation group with no evidence of PIN on the prestudy biopsy (P = 0.60). This study, using a novel model for evaluating short-term efficacy of chemopreventive or therapeutic agents in men at high risk of prostate cancer, provides little evidence that finasteride is an effective chemopreventive agent for prostate cancer in men with elevated PSA.

Effect of early treatment of prostate cancer with the 5alpha-reductase inhibitor turosteride in Dunning R3327 prostatic carcinoma in rats

BACKGROUND

Turosteride, a selective 5alpha-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. We evaluated the preventive effect of turosteride when administered during the latency period in this prostatic tumor model.

METHODS

Turosteride was given orally, 6 days a week for 10-15 weeks, starting at different times: 1) 5 weeks after tumor implantation, when tumors were not yet palpable, or 2) 1 day after tumor implantation. In each experiment, one group of animals was castrated on the first treatment day.

RESULTS

When treatment started 5 weeks after tumor implantation, neither turosteride (at 50 and 200 mg/kg/day) nor castration reduced tumor incidence (91-100%). Tumor growth was reduced in groups treated with the highest dose of turosteride and in castrated rats. When treatment started 1 day after tumor implantation, castration resulted in a 62% tumor incidence compared to 100% in controls, while turosteride at 200 mg/kg/day was not effective in reducing tumor incidence. However, as in the previous experiment, the compound was highly effective in reducing tumor growth.

CONCLUSIONS

The antitumor activity profile of turosteride seems not to be related to the timing of treatment. Given either 5 weeks or 1 day after tumor implantation, the compound did not reduce tumor take, while it maintained effective tumor growth-inhibiting activity in both cases.

Effect of the dual 5alpha-reductase inhibitor PNU 157706 on the growth of dunning R3327 prostatic carcinoma in the rat

PNU 157706 [N-(1,1,1,3,3,3-hexafluorophenylpropyl)-3-oxo-4-aza-5alpha-androst-1-ene-17beta-carboxamide] is a novel, potent and selective dual 5alpha-reductase inhibitor. We have investigated its effect on tumor growth, endocrine organ weights and prostatic dihydrotestosterone (DHT) content in rats bearing the androgen dependent Dunning R3327 prostatic carcinoma. Animals with tumor diameters of about 1 cm were treated orally for 9 weeks with PNU 157706 (2 and 10 mg/kg/day, 6 days a week) or they were castrated, to check the hormone responsiveness of the tumor. PNU 157706 was effective at both doses tested in reducing tumor growth (53 and 51% inhibition at 2 and 10 mg/kg/day, respectively), while castration caused higher inhibition (82%) of tumor growth. A marked reduction of ventral prostate weight occurred in rats treated with both doses of PNU 157706 (75 and 78%) or castrated (91%). Seminal vesicle weight was also reduced by PNU 157706 administration (56 and 61% inhibition), whereas testes, adrenal, thymus and pituitary weights were not affected. Prostatic DHT content was markedly suppressed (85 and 91%) in PNU 157706 treated rats, compared to 95% suppression caused by castration. These data support a possible role of dual 5alpha-reductase inhibitors in the hormonal therapy of prostatic cancer.

A five-alpha reductase inhibitor or an antiandrogen prevents the progression of microscopic prostate carcinoma to macroscopic carcinoma in rats

BACKGROUND

The objective of this study was to elucidate the prophylactic effects of 5-alpha reductase inhibitor (e.g., finasteride) and a pure antiandrogen (e.g., casodex) on rat prostate carcinogenesis and to determine whether latent prostate carcinoma can be prevented to develop to clinically significant cancer by use of these drugs.

METHODS

F344 rats were subcutaneously administered 3,2'-dimethyl-4-aminobiphenyl (DMAB) for the first 20 weeks and testosterone propionate throughout the 60-week study. Finasteride (5 mg/kg and 15 mg/kg, 2 times per week) and casodex (15 mg/kg, 30 mg/kg, and 60 mg/kg, 3 times per week) were administered orally during the last 40 weeks of the study. Tumors were classified as visible prostate carcinoma when they could be recognized with the naked eye and as microscopic prostate carcinoma when detectable only with a microscope.

RESULTS

The incidence of visible prostate carcinoma was 51% (18 of 35 rats) in the positive control group, whereas it was 40% (4 of 10 rats) in the finasteride 5 mg/kg group, 16.7% (2 of 12 rats, P = 0.0091) in the finasteride 15 mg/kg group, 20% (4 of 20 rats, P = 0.05) in the casodex 15 mg/kg group, 14.3% (3 of 21 rats, P = 0.0008) in the casodex 30 mg/kg group, and 0% (0 of 11 rats, P = 0.0002) in the casodex 60 mg/kg group. On the other hand, when visible carcinomas and microscopic carcinomas were handled together, only casodex 60 mg/kg significantly inhibited the carcinogenesis rate.

CONCLUSIONS

Finasteride achieved dose-dependent inhibition of macroscopic rat prostate carcinogenesis, and casodex also inhibited macroscopic prostate carcinogenesis. However, both drugs showed insufficient prevention of carcinogenesis at the microscopic level. These findings indicate that, in clinical medicine as well, such drugs may also be able to prevent the progression of latent prostate carcinoma to life-threatening disease.

Effect of turosteride, a 5 alpha-reductase inhibitor, on the Dunning R3327 rat prostatic carcinoma

BACKGROUND

Turosteride (FCE 26073) is a new, potent, and selective 5 alpha-reductase inhibitor. We have investigated its effect on tumor growth, organ weight, and serum hormone levels in rats bearing the androgen sensitive Dunning R3327 prostatic carcinoma.

METHODS

Animals with tumor diameters of 0.5-1.5 cm were treated for 9 weeks with turosteride (50 and 200 mg/kg/day, 6 days a week, orally), flutamide (25 mg/kg/day, 6 days a week, orally), and leuprolide (300 micrograms/rat, every 3 weeks, subcutaneously) or they were castrated.

RESULTS

Turosteride was ineffective at the dose of 50 mg/kg/day, whereas at 200 mg/kg/ day it significantly decreased tumor growth by 45%. Flutamide and leuprolide were highly effective in reducing tumor growth (70 and 77%), although their effect was slightly lower than that of castration (85%). A significant reduction of ventral prostate weight occurred in rats treated with turosteride at 50 and 200 mg/kg/day (53% and 60%). In contrast to leuprolide and castration, the inhibitory effect of turosteride on tumor growth and prostate weight was not associated to any decrease in serum testosterone.

CONCLUSIONS

Turosteride has antitumor activity on Dunning prostatic tumor growth and its role in prostatic cancer treatment is worthy of further investigation.

The future of antihormone therapy: innovations based on an established principle

Endocrine therapy of mammary and prostate cancer has been established for decades. The therapies available to block sex-hormone-receptor-mediated tumor growth are based on two principles: (i) ligand depletion, which can be achieved surgically, by use of luteinizing-hormone-releasing hormone analogues or inhibitors of enzymes involved in steroid biosynthesis or by interfering with the feedback mechanisms of sex hormone synthesis at the pituitary/hypothalamic level; (ii) blockade of sex hormone receptor function by use of antihormones. The antiestrogen tamoxifen, which is the compound of choice for the treatment of mammary carcinoma, has the drawback of being a partial agonist. A complete blockade of estrogen receptor (ER) function can be achieved by a new class of compounds, pure antiestrogens. In contrast to aromatase inhibitors, pure antiestrogens are able to block ER activation by ligands other than estradiol and can also interfere with ligand-independent ER activation. In addition to estradiol, progesterone has a strong proliferative effect in mammary carcinomas. Antiprogestins are promising new tools for clinical breast cancer therapy. These compounds clearly need a functionally expressed progesterone receptor to block tumor growth, but there is strong experimental evidence that their tumor inhibition is based on more than just progesterone antagonism. The ability of these compounds to induce tumor cell differentiation that leads to apoptosis is unique among all other endocrine therapeutics. In prostate tumors that have relapsed from current androgen-ablation therapies the androgen receptor (AR) is still expressed and, compared to the primary tumors, its level is often even enhanced. Mutated AR that can be activated by other compounds such as adrenal steroids, estrogens, progestins and even antiandrogens have been detected in recurrent tumors. Thus, relapse of tumors under the selective pressure of common androgen-ablation therapies can be caused by acquired androgen hypersensitivity and AR activation by ligands other than (dihydro-)testosterone. There is a clinical need for future compounds that produce a complete blockade of AR activity even in recurrent tumors. Preclinical experiments indicate that combination therapy as well as the extension of endocrine treatments to several other tumor entities are promising approaches for further developments. Examples are the combination of antiestrogens and antiprogestins for breast cancer treatment, or the treatment of prostate carcinomas with antiprogestins.

The enzyme and inhibitors of 4-ene-3-oxosteroid 5 alpha-oxidoreductase

Since evidence of 5 alpha-reductase activity in rabbit liver homogenate was discovered in 1954, the presence of this enzyme has been demonstrated in many other organs and tissues of mammalian species. 5 alpha-Reductase selectively transforms a 4-ene-3-oxosteroid (e.g., testosterone) irreversibly to the corresponding 5 alpha-3-oxosteroid (e.g., 5 alpha-dihydrotestosterone) in the presence of NADPH as an essential coenzyme at an optimal pH. However, excessive production of 5 alpha-dihydrotestosterone is the major cause of many androgen-related disorders, such as prostate cancer, benign prostatic hyperplasia, acne, female hirsutism, and male pattern baldness; therefore, inhibition of androgenic action by 5 alpha-reductase inhibitors is a logical treatment. During the past two decades, research has focused on understanding the biological functions and effects of 5 alpha-reductase and its 5 alpha-reduced metabolites: purification of the enzyme, substrates, and metabolites; characterization of their physical, chemical, and biochemical properties; analysis of the amino acid sequence of the enzyme; synthesis of various classes of molecules as potential inhibitors; and examination of the biological activity of the inhibitors in vitro and/or in vivo. This review summarizes the biochemical studies on this enzyme, suggests the mechanisms of action of the enzyme or inhibitors, and discusses the chemistry necessary for the preparation, structure-activity relationships, and in vitro and/or in vivo data obtained from the evaluation of nonsteroidal and steroidal compounds that have been tested as inhibitors of 5 alpha-reductase. In particular, IC50 and Ki values for relevant compounds will be compared according to molecular class. This review could function as a comprehensive working reference of what research has been accomplished so far and what problems remain to be solved in the future for those engaged in this interesting field.

The potential for hormonal prevention trials

Breast and prostate cancer are significant causes of morbidity and mortality and are very similar in etiology, epidemiology, and modalities of treatment. Investigational strategies in the prevention of these malignancies also have strong parallels. The National Cancer Institute is sponsoring several large scale clinical trials involving hormonal manipulation and cancer prevention. In the Breast Cancer Prevention Trial, 16,000 women at high risk for breast cancer are being randomized to receive the antiestrogen agent tamoxifen or placebo for 5 years in an effort to determine if breast cancer development can be inhibited. In a similar trial, the Prostate Cancer Prevention Trial, 18,000 men older than 55 years of age will be randomized to receive finasteride, a 5-alpha-reductase inhibitor, or placebo to determine if inhibition of dihydrotestosterone synthesis in the prostate over a prolonged period will lead to a decreased incidence of prostate cancer. Both clinical trials offer the possibility of demonstrating that a hormonal intervention can decrease an individual's risk of developing breast or prostate cancer. They also have the potential of providing critical information about cancer risk, etiology, screening, and genetics, as well as quantifying the risks and benefits of specific preventive interventions.

5 alpha-reductase inhibitors and prostatic disease

5 alpha-Reductase inhibitors are a new class of substances with very specific effects on type I and type II 5 alpha R which may be of use in the treatment of skin disease, such as male pattern baldness, male acne and hirsutism, as well as prostatic hyperplasia and prostate cancer. At least two types of 5 alpha R inhibitors with a different pH optimum have been described. cDNA encoding for both the type I and the type II enzyme has been cloned. Most of the orally effective 5 alpha R inhibitors belong to the class of 4-azasteroids. The radical substituted in the 17 position of the steroid ring seems to be related to species specific variations and to the types of 5 alpha R enzymes in different species and organ systems. 5 alpha R inhibitors lead to a decrease of plasma DHT by about 65% while there is a slight rise in plasma testosterone. The decrease of tissue DHT in the ventral prostate of the intact rat, the dog and in humans is more pronounced and amounts to about 85%. There is a reciprocal rise of tissue T in these systems. The application of an inhibitor of 5 alpha R type II leads to a shrinkage of BPH in men by about 30%. In the rat a similar shrinkage accompanied by a significant decrease of total organ DNA occurs. This decrease, however, is not as pronounced as can be achieved with castration.(ABSTRACT TRUNCATED AT 250 WORDS)

Qualitative and quantitative evaluation of prostatic histomorphology in rats following chronic treatment with finasteride, a 5-alpha reductase inhibitor

OBJECTIVE

To determine any potential direct and/or indirect effects of elevated intraprostatic T levels on the prostates of rats chronically (1-2 years) exposed to high doses (160 mg/kg/day) of finasteride, a selective inhibitor of 5-alpha reductase.

METHODS

Sprague-Dawley male rats were administered daily finasteride by oral gavage. Prostates from all rats were weighed, fixed in 10% neutral buffered formalin, and processed for light microscopic examination. The volume fractions of the prostatic glandular and stromal compartments were quantitated by morphometric analysis.

RESULTS

Administration of finasteride at doses of 20, 40, and 80 mg/kg/day for one year resulted in a significant (P < or = 0.05) decrease in prostatic weight; prostatic atrophy was evident by light microscopy. Morphometric analysis of the prostate showed that chronic finasteride administration resulted in a significant (P < or = 0.001) decrease in the absolute volume of both glandular (-65.2%) and stromal (-57.1%) compartments of the prostate. Furthermore, the total number of epithelial and stromal cells per gland were significantly (P < or = 0.002) decreased in finasteride-treated rats compared with vehicle controls; the magnitude of mean decrease was 69.8 percent and 50.6 percent of controls in epithelial and stromal cells, respectively. In addition, prostates from all two hundred fifty rats in a two-year study were qualitatively evaluated by light microscopy. Administration of finasteride at doses ranging from 2.5 mg/kg/day to 160 mg/kg/day for two years did not result in an increase over the background incidence of prostatic focal hyperplasia or adenoma. No malignant tumors of the prostate were seen in any of the groups.

CONCLUSIONS

These studies have demonstrated that the expected pharmacologic effects of finasteride on the prostate are maintained following chronic treatment and that there was no evidence of a direct and/or an indirect effect of elevated intraprostatic T on prostatic morphology in rats.

Antitumoral effects of liarozole in androgen-dependent and independent R3327-Dunning prostate adenocarcinomas

We examined the in vivo antitumoral effects of liarozole against androgen-dependent and independent Dunning rat prostatic tumors. Liarozole, applied as a dietary admixture, at a dose of 120 mg./100 gm. food, equivalent to 100 mg./kg. per day, inhibited the growth of the slow growing, well-differentiated, androgen-dependent Dunning-H tumor (median tumor volume decrease of 60%). At the same dose it also significantly reduced the growth of the androgen-independent, moderately differentiated PIF-1 (-60%) and androgen-independent, anaplastic AT-6 tumors (-73%). The growth of AT-6 sq tumor showing squamous metaplasia was unaffected by liarozole. When administered by oral gavage, liarozole at 40 (-82%) mg./kg. twice a day was as effective as castration (-92%) in reducing the androgen-dependent, poorly differentiated Dunning R3327-G tumor. Liarozole, administered by gavage, twice a day, also significantly reduced median tumor volume in the androgen-independent, AT-6 sq (-90% at 60 mg./kg., twice a day). This difference between liarozole administration by gavage and food admixture will have to be taken into account in further experimental studies. Inhibition of the growth of several androgen-dependent and, chiefly, androgen-independent Dunning prostate carcinoma sublines that differ widely in their histological degree of differentiation and growth rate suggests that liarozole may be a suitable agent for evaluation in second line treatment of hormone refractory prostate carcinoma in patients who relapse after androgen ablation.

Blockade of androstenedione-induced stimulation of androgen-sensitive parameters in the rat prostate by combination of Flutamide and 4-MA

In order to mimic the human situation in which adrenal steroid precursors are converted to the active androgen dihydrotestosterone (DHT) in prostatic tissue, we have used castrated rats supplemented with the precursor steroid androstenedione (delta 4-dione) released from Silastic implants. While it is well known that the action of DHT can be partially neutralized by antiandrogens which compete for binding to the androgen receptor, we have used 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (4-MA), an inhibitor of 5 alpha-reductase, the enzyme which converts testosterone into DHT, in order to decrease intraprostatic DHT levels and thus facilitate the action of the antiandrogen. Animals were treated for 7 days with Flutamide (FLU, 2 mg) or 4-MA (4 mg) injected subcutaneously, twice daily, alone or in combination. 4-MA administered alone caused a 54% inhibition of delta 4-dione-stimulated ventral prostate weight while FLU exerted a 74% inhibitory effect and 4-MA+FLU further improved inhibition to 81%. We then measured, by in situ hybridization, the levels of prostatic mRNAs encoding the C1 and C3 components of the prostatic binding protein (PBP) which are highly specific and sensitive markers of androgen action. PBP-C3 mRNA levels fell by 95% following castration while treatment with delta 4-dione completely reversed the effect of castration. Administration of FLU or 4-MA independently caused 33% and 10% decreases, respectively, of PBP-C3 mRNA levels stimulated by delta 4-dione while the combination of both compounds further inhibited PBP-C3 mRNA levels to reach a 55% inhibition. Similar effects were observed on PBP-C1 mRNA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemoprevention strategies for prostate cancer: the role of 5 alpha-reductase inhibitors

Prostate cancer is a major health problem for the aging male population. Despite hormonal dependence, the inevitable emergence of androgen insensitive tumors, which have a dismal prognosis, highlights the need to develop prevention strategies such as chemoprevention. An acceptable agent must interfere with either the process of carcinogenesis or tumor growth, and have minimal toxicity. In clinical studies, 5 alpha-reductase inhibitors have been shown to suppress serum and intraprostatic levels of dihydrotestosterone, an important promoter of prostate cancer, leading to reduction in prostate size and suppression of glandular cell activity as measured by prostate specific antigen secretion. In addition, 5 alpha-reductase inhibitors have demonstrated an excellent safety profile and tolerability in 12 month controlled clinical trials. No significant metabolic effects have been observed in gonadotropin secretion, spermatogenesis, serum lipids or glucose tolerance. The efficacy and safety of 5 alpha-reductase inhibitors in studies to date, combined with the androgen dependence of tumor production, strongly supports investigating their use for chemoprevention of prostate cancer.

Response of rat and human prostatic cancers to the novel 5 alpha-reductase inhibitor, SK&F 105657

The response of two androgen-responsive rat prostatic cancers (i.e., Dunning R-3327 H and G sublines) and one androgen-responsive human prostatic cancer (i.e., PC-82) to the 5 alpha-reductase inhibitor, SK&F 105657, was tested in vivo. SK&F 105657 was administered orally twice a day at a dose of 25 or 50 mg/kg/dose. The rat R-3327 G tumor and the human PC-82 tumor have a low to undetectable level of tissue 5 alpha-reductase activity and both responded to SK&F 105657 treatment with a reproducible inhibition of tumor growth. Associated with this antitumor effect was a major decrease (i.e., greater than 70%) in tissue dihydrotestosterone (DHT) content in both tumors. By contrast, the rat R-3327 H prostatic cancer has a much higher level of tissue 5 alpha-reductase activity, and neither tumor DHT content nor growth of the tumor was inhibited by treatment with SK&F 105657. Drug treatment of rats bearing R-3227 H tumors resulted in a similar reduction in the DHT content, wet weight, and DNA content of the ventral prostate as that produced in R-3327 G tumor-bearing rats which experienced an antitumor response. These results suggest that SK&F 105657 can produce antitumor effects if a substantial reduction in tissue DHT is achieved. Such reduction in tissue DHT, secondary to inhibition of the tissue 5 alpha-reductase enzyme, appears to be more difficult to achieve in tumors than in the normal prostate. In order to achieve such a DHT reduction in tumor tissue, prostatic cancers with low 5 alpha-reductase activity could be treated with SK&F 105657 on a dose regimen that lowers serum DHT to surgical castration levels, while concomitantly inhibiting the already low tumor tissue 5 alpha-reductase activity.