Monomethylated selenium inhibits growth of LNCaP human prostate cancer xenograft accompanied by a decrease in the expression of androgen receptor and prostate-specific antigen (PSA)

OBJECTIVES: Epidemiological studies and prevention trials suggest selenium is a promising preventive agent for prostate cancer. Selenium-containing compounds inhibited the growth of prostate cancer cell lines including androgen sensitive LNCaP and androgen insensitive DU145 and PC3 cells in vitro. Previous study revealed a novel mechanism of selenium action in which selenium (methylseleninic acid (MSA)) markedly reduced androgen receptor (AR) signaling in prostate cancer cells, suggesting that selenium might act as an antiandrogen, which could serve as a therapeutic agent for prostate cancer. In this study, we tested whether selenium (methylselenocysteine (MSC)) affects tumor growth of human prostate cancer cells by targeting AR signaling in vivo. METHODS: Prostate tumor xenografts were established in nude mice by co-inoculating LNCaP cells with Matrigel. The mice-bearing tumors were treated with or without MSC (100 microg/mouse/day) via intraperitoneal injection for 2 weeks. The effect of MSC on tumor growth, AR, and prostate-specific antigen (PSA) expression was examined. RESULTS: Methylselenocysteine (MSC) significantly inhibited LNCaP tumor growth (P < 0.05). AR expression in tumor tissues and serum PSA levels were considerably decreased in MSC-treated mice compared to the vehicle controls. CONCLUSIONS: Pharmacological dose of MSC inhibits the growth of LNCaP human prostate cancer in vivo accompanied by a decrease in the expression of AR and PSA. These findings suggest that selenium (MSC) can serve as a therapeutic agent aimed at disruption of AR signaling for prostate cancer.     

Caveolin expression is decreased following androgen deprivation in human prostate cancer cell lines.

BACKGROUND: Increased expression of caveolin has been associated with prostate cancer progression. In a mouse reconstitution model of prostate cancer, expression of caveolin was inversely related to androgen sensitivity: androgen independent clones had high caveolin expression; low caveolin expression was associated with sensitivity to androgen withdrawal. In contrast, several independent observations support the hypothesis that caveolin functions as a tumor suppressor. METHODS: Caveolin expression was studied by Western blot analysis and/or immunohistochemistry in three androgen-sensitive human prostate cancer cell lines LNCaP, LAPC-4 and LAPC-9, and following acute and chronic androgen deprivation, and in benign prostate epithelial cells. Expression of caveolin, androgen receptor (AR) and prostate specific antigen (PSA) was also examined after reintroduction of androgen. RESULTS: LNCaP grown continuously under androgen-depleted conditions for 6 to 42 months produced several androgen-independent and tumorigenic clones: tumors formed in 13/15 castrate and 7/15 intact male athymic nu/nu mice, but no tumors formed in wildtype LNCaP-bearing animals. Caveolin expression was decreased in every androgen-deprived LNCaP clone and following 150 days of androgen deprivation in LAPC-4. Caveolin expression by LAPC-9 was very low. Following exposure to dihydrotestosterone in vitro, caveolin and PSA expression increased within three days in the androgen-deprived clones of LNCaP. Benign prostate epithelial cells have high caveolin expression. CONCLUSIONS: Unlike the mouse reconstitution model of prostate cancer, the pattern of caveolin expression in benign prostatic epithelium and androgen-sensitive human prostate cancer is consistent with tumor suppressive activity.     

Effect of the neuropeptides bombesin and calcitonin on the growth of prostate cell lines, PC-3, DU 145, and LNCaP

Neuroendocrine cells are present in normal and tumoral prostate tissue, the neuropeptides secreted by this cells have a biological functions that have not been fully elucidated. The presence of neuroendocrine cells in prostatic carcinoma have been shown to increase tumor progression. We characterized the in vitro proliferative influence of bombesin and calcitonin in androgen-insensitive, PC-3 and DU-145, and androgen-sensitive, LNCaP, cell lines of human prostate cancers. The influence of these neuropeptides on proliferation were assessed using the colorimetric XTT assay and by cells counts with a hemocytometer. The growth of PC-3 and DU-145 cell lines is stimulated by bombesin and calcitonin but exerted any stimulatory effect on the proliferation of the LNCaP cell line. This indicate that bombesin and calcitonin can modulate proliferation of androgen-insensitive human prostate cell lines "in vitro" and may be potential paracrine growth promoters in stablished androgen irresponsive human prostatic carcinoma cells.     

Secretion of prostate-specific antigen-suppressing activity by two human prostate carcinoma cell lines

The well-differentiated human prostatic carcinoma cell line LNCaP has often been used as a model to study the modulation of prostate-specific antigen (PSA) expression. In this study, we examined the effect of conditioned medium from two androgen-unresponsive, PSA-negative human prostatic carcinoma cell lines, PC-3 and DU-145, on PSA expression by the LNCaP cells. Our results show, for the first time, that the undifferentiated PC-3 and DU-145 cells secrete a factor that lowers PSA mRNA and protein levels in LNCaP cells. Further characterization of the PSA-suppressing activity indicated that it was trypsin as well as acid sensitive, heat-stable, and ammonium sulfate precipitable. The activity was present in the 30-100-kd fraction of PC-3 and DU-145 conditioned media. This PSA-suppression factor could act in an autocrine manner to render undifferentiated prostatic carcinoma cells PSA negative. It may also be responsible for the lack of increase in serum PSA levels observed in a subset of patients with hormone-resistant prostatic carcinoma.     

Inhibition of androgen-sensitive LNCaP prostate cancer growth in vivo by melatonin: association of antiproliferative action of the pineal hormone with mt1 receptor protein expression

BACKGROUND: Potential involvement of the mt1 receptor in the antiproliferative action of melatonin on androgen-sensitive LNCaP cells, and melatonin-induced modulation of androgen-insensitive PC-3 cell growth, have been reported in vitro. The effects of melatonin on prostate cancer cell proliferation and their association with mt1 receptor expression were investigated in athymic nude mice xenograft models of LNCaP and PC-3 cells. METHODS: Daily saline or melatonin (4 microg/g body weight) was given to nude mice before or after tumor cell inoculation. Tumor volume was measured periodically, and expression of PCNA, cyclin A, PSA, and mt1 receptor was assessed by immunohisto(cyto)chemistry and/or Western blotting. RESULTS: Melatonin inhibited the growth of LNCaP tumors, without affecting the growth of PC-3 xenografts, in nude mice. It induced significant decreases in the expression of PCNA, cyclin A, and PSA in LNCaP tumors. Expression of mt1 receptor protein was demonstrated in LNCaP cells, but not in PC-3 cells, both in vivo and in vitro. CONCLUSIONS: The antiproliferative action of melatonin on LNCaP tumor growth was demonstrated in vivo, and its association with mt1 receptor protein expression suggests the potential involvement of the receptor in the antitumor activity of the pineal gland hormone.     

Melatonin and prostate cancer cell proliferation: interplay with castration,epidermal growth factor,and androgen sensitivity

BACKGROUND: Potential modulatory effects of melatonin on the proliferation of androgen-sensitive LNCaP and androgen-insensitive PC-3 and DU 145 prostate cancer cells were reported recently. In this study, we investigated the effects of combined melatonin and castration on LNCaP tumor growth in vivo, the interactions between melatonin and epidermal growth factor (EGF) on LNCaP cell proliferation, and melatonin actions on the proliferation of PC-3 and DU 145 cells. METHODS: Tumor development and growth in castrated nude mice inoculated with LNCaP cells or in intact animals inoculated with DU 145 cells, with or without daily melatonin treatment, were monitored by observation and caliper measurement. MT(1) receptor expression in native or transfected prostate cancer cell lines was examined by immunocytochemistry or 2-[(125)I]iodomelatonin binding. Cyclin D1 expression in LNCaP cells was assessed by Western blotting, and cell proliferation was measured by thymidine incorporation and/or cell count. RESULTS: Melatonin treatment was associated with further decreases in LNCaP tumor incidence and growth rate in castrated nude mice. Melatonin and 2-iodomelatonin (a melatonin receptor agonist) attenuated EGF-stimulated increases in LNCaP cell proliferation and cyclin D1 levels. Melatonin had no effect on the proliferation or growth of MT(1) receptor-expressing DU 145 cells, and of PC-3 cells in which MT(1) receptor protein was undetectable. The proliferation of transfected PC-3 cells expressing MT(1) receptor was unaffected by 2-iodomelatonin. CONCLUSION: Together with previous data, the present results indicate synergistic action of melatonin and castration in inhibiting the growth of androgen-sensitive LNCaP tumor. Androgen-sensitive prostate cancer cell proliferation may be modulated by opposite changes in cyclin D1 levels induced by activated MT(1) and EGF receptors. In androgen-insensitive prostate cancer cells, MT(1) receptor-mediated signal transduction may become defective not only through changes in membrane receptor protein expression and/or functions, but also by means of alterations in downstream postreceptor signaling events.     

Comparative experimental study of the serum prostate specific antigen and prostatic acid phosphatase in serially transplantable human prostatic carcinoma lines in nude mice

Three different human lines of prostate carcinoma were successively transplanted on Balb/c nude mice and the serum values of the prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) were determined simultaneously. In a group of the tumor-bearing animals the influence of endocrine manipulation (castration, estradiol) on the serum concentration of these tumor markers was studied. As far as untreated tumor-bearing mice are concerned, the serum values of both PAP and PSA proved to be strictly dependent on the tumor volume measured. In the exponential growth phase of the grafted tumors, linear growth was linked with a correspondingly increasing PAP and PSA serum level of the test animals. A close correlation was found to exist between the two tumor markers; however, the indicator value of PSA was 20 to 50 times higher than that of PAP under the test conditions. PSA determination yielded no false-negative results, if PAP was elevated. PAP determination was false-negative in 21 per cent of cases with measurable tumors, although the serum level of PSA already showed marked elevation. In treated animals both markers were found to decrease. Arrested growth and tumor regression was associated with falling PAP and PSA serum levels or with levels within normal range. The results of this experimental study support the conclusion that prostate specific antigen represents a substantially more sensitive tumor marker than prostatic acid phosphatase.     

Growth of heterotopic LNCaP prostate cancer tumor in nude mice is not affected by dietary calcium

BACKGROUND: We attempted to provide experimental evidence linking increased dietary calcium to progression of prostate cancer, as suggested by some epidemiological studies, using a heterotopic prostate cancer nude mice model. METHODS: Twenty heterotopic LNCaP prostate cancer tumor bearing nude mice were randomly assigned to one of the four groups: (I) high fat/low calcium diet, (II) high fat and high calcium diet, (III) high fat diet fortified with Vitamin D3, and (IV) high fat and high calcium diet fortified with Vitamin D3. In addition to weekly animal weights and tumor size measurements, the serum prostate specific antigen (PSA), 25-hydroxy Vitamin D3, calcium, phosphorus, total protein, albumin (to account for bound calcium) [1], and serum alkaline phosphatase (a measure of bone loss) [2] were determined at the termination of experiments. RESULTS: Although the serum calcium and 25-hydroxy Vitamin D3 were significantly higher in groups III and IV compared to groups I and II (P < 0.05), there was no significant difference between the tumor growth rates, final tumor weights (P = 0.9), and the serum PSA levels (P = 0.94) between the four groups. CONCLUSIONS: The results suggest that dietary calcium does not significantly affect the growth of heterotopic LNCaP prostate cancer in nude mice.     

Inhibition of vascular endothelial cell growth factor suppresses the in vivo growth of human prostate tumors

The LNCaP human prostate cancer cell line is androgenand stromal-dependent for in vivo growth. We co-inoculated LNCaP cells with human fetal fibroblasts, isolated from prostate, bone (male), and lung (male and female) derived from 18- to 22-week-old human fetal tissue, into non-castrate male nude mice. Co-inoculation of LNCaP with fetal prostatic fibroblasts resulted in high tumor take rates (27 of 30, or 90%) 6 to 8 weeks after subcutaneous co-inoculation. Serum prostate specific antigen (PSA) values correlated strongly with wet tumor weight (r=0.86). The fetal fibroblast enhancement of tumor take rates in vivo was neither gender- nor organ-specific. Fetal fibroblast-conditioned medium (CM) did not have a significant proliferative effect on LNCaP cell growth in vitro. Areas of angiogenesis were demonstrable in all tumors, with blood vessels arising at the interface between stromal and tumor cells. The fetal fibroblasts, but not the LNCaP cells, expressed significant amounts of the mRNA and protein for vascular endothelial cell growth factor (VEGF). Treatment of tumor-bearing animals with neutralizing antibodies to VEGF resulted in significant tumor growth suppression. These findings indicate that VEGF is an important mediator of stromal-induced enhancement of human prostate cancer cell growth in vivo.     

The differentiating agent phenylacetate increases prostate-specific antigen production by prostate cancer cells

The prostatic-specific antigen (PSA) is the tumor marker most widely relied upon for the monitoring of patients with prostate cancer. Recently, declines in the serum concentrations of PSA have been advocated as a surrogate marker of tumor response in clinical trials of investigational antitumor agents. We examined the hypothesis that this postulate may not apply to the evaluation of drugs such as phenylacetate, a differentiating agent endowed with mechanisms of action different from those of classic cytotoxic chemotherapy. Using human prostatic carcinoma LNCaP cells as a model, we show that phenylacetate induces PSA production despite inhibition of tumor cell proliferation. Incubation of LNCaP cultures with cytostatic doses of phenylacetate (3–10 mM) resulted in a three- to fourfoLd increase in PSA secretion per cell. This appears to result from upregulation of PSA gene expression, as indicated by elevated PSA mRNA steady-state levels in treated cells. The increase in PSA production per cell was confirmed in rats bearing subcutaneous LNCaP tumor implants that were treated systemically with phenylacetate. Further comparative studies indicate that upregulation of PSA is common to various differentiation inducers, including all, trans-retinoic acid, 1,25-dihydroxyvitamin D₃, and butyrate but is not induced by other antitumor agents of clinical interest such as suramin. We conclude that declines in PSA may be treatment specific and that the exclusive use of this criterion as a marker of disease response may mislead the proper evaluation of differentiating agents in prostate cancer patients. © 1996 Wiley-Liss, Inc.     

Can prostate-specific antigen be used as a valid end point to determine the efficacy of chemotherapy for advanced prostate cancer?

Summary It is current practice in many clinical trials evaluating new chemotherapy regimens for the treatment of advanced prostate cancer to use prostate-specific antigen (PSA) decline as a response criteria with the assumption that the level of PSA reflects the efficacy of chemotherapy. Advanced prostate cancer is heterogeneous; therefore, the validity of PSA decline as a measurable end point was studied in advanced human prostate-cancer cell lines: androgen-sensitive LNCaP and androgen-insensitive PC3 cells. Each cell line was grown for 4 days with escalating doses of Adriamycin or vinblastine. Cell counts, intracellular PSA concentrations, and secreted PSA levels were determined daily for 4 days. Untreated LNCaP cells had constant secretion of PSA per cell. In contrast, LNCaP cells treated with Adriamycin or vinblastine had an 80% reduction in cell numbers and a 3-fold increase in secreted PSA per cell by day 4. In contrast, PC3 cells had a different response to Adriamycin and vinblastine. Both drugs reduced cell numbers by 97% of control values and suppressed PSA production in the remaining viable cells by 4 days in culture. Thus, prostate-cancer cell production of PSA is variable with chemotherapy and the PSA level may not accurately reflect the actual tumor response to chemotherapy.     

Regulation of prostate-specific antigen gene expression in LNCaP human prostatic carcinoma cells by growth,dihydrotestosterone, and extracellular matrix

We have examined the role of extracellular matrix (ECM), cell growth, and dihydrotestosterone on the expression of prostate-specific antigen (PSA) by human prostatic carcinoma cells LNCaP. ECM induced a transient decrease in PSA mRNA even in the presence of growth factors. PSA mRNA, but not actin mRNA, was down-regulated on ECM in a biphasic manner and was not detected up to 48 hr after culture, but was re-expressed after 3 days. Cycloheximide and actinomycin D pretreatment did not prevent ECM-induced down-regulation of PSA mRNA, while actinomycin D-treated cells on plastic maintained stable PSA mRNA levels. DNA synthesis and PSA glycoprotein secretion were also transiently suppressed on ECM. LNCaP growth inhibition correlated with decreased glyceraldehyde phosphate dehydrogenase mRNA levels. However, the transient growth suppression induced by ECM was not observed with primary endothelial cells on Matrigel. Down-regulation of PSA mRNA by culture on Matrigel was reversible upon transfer to a different matrix substrate. Re-expression was highest on heparan sulfate proteoglycan (4-fold) and fibronectin or collagen I (2-fold) compared to plastic or laminin. Our results indicate that the morphology and proliferation of LNCaP cells may be regulated by the ability of ECM to control cellular differentiation and proliferation. © 1994 Wiley-Liss, Inc.     

Regulation of prostate-specific antigen (PSA) gene expression and release in LNCaP prostate cancer by antagonists of growth hormone-releasing hormone and vasoactive intestinal peptide

BACKGROUND: Prostate-specific antigen (PSA) is the best tumor marker for diagnosis and prognosis of prostatic carcinoma. The secretion of PSA from LNCaP human prostate cancer cells is influenced by acute stimuli such as vasoactive intestinal peptide (VIP), growth hormone-releasing hormone (GHRH), and chronic stimuli like androgens. METHODS: To study the regulation of basal and VIP/GHRH or androgen-stimulated secretion from LNCaP cells, we used a superfusion system, which allowed us to simultaneously measure PSA gene expression, PSA secretion, and cAMP release from the same cancer cells. LNCaP cancer cells were also implanted orthotopically into nude mice. RESULTS: VIP (30 pM-3 nM), GHRH (3 nM-300 nM), and dihydrotestosterone (100 nM) induced a significant increase in PSA gene expression, PSA secretion, and cAMP release. The dose and time-dependent effects of peptides were manifested only in the presence of androgens. At the end of continuous stimulation of cells with 1 nM VIP for 2 hr, large amounts of stored immunoreactive PSA still remained in the cells. Adenylate cyclase activator, forskolin (FSK), significantly increased PSA secretion and gene expression, and potassium, which causes nonspecific depolarization of membranes, augmented gene expression, and secretion of PSA, but did not influence cAMP release. This suggests that PSA secretion is regulated by cAMP-dependent as well as cAMP-independent pathways. In superfusion system, stimulatory effects of VIP and GHRH on PSA secretion were inhibited by VIP antagonist JV-1-53, and less by GHRH antagonist JV-1-38. In cell cultures, JV-1-38 had a stronger inhibitory effect on proliferation, indicating an involvement of the recently discovered tumoral GHRH receptors in this process. In nude mice, with orthotopically implanted LNCaP cancer cells, GHRH antagonist JV-1-38 alone or androgen ablation by castration had no effect on tumor growth and PSA levels. However, castration combined with treatment with GHRH antagonist, significantly decreased tumor growth and PSA secretion. CONCLUSIONS: Our findings suggest that the secretion of PSA is regulated rather than constitutive, contrary to previous reports. In addition, the effect of GHRH and VIP antagonists on PSA secretion from prostate cancer cells is not correlated with their antiproliferative action.     

High-malignancy orthotopic nude mouse model of human prostate cancer LNCaP.

BACKGROUND: An animal model of human prostate cancer LNCaP demonstrating high rates of spontaneous metastasis from the orthotopic site after tumor implantation would be very valuable for mechanistic and drug discovery studies. We previously developed microsurgical techniques to implant histologically intact tumor tissues orthotopically in nude mice in order to develop high metastatic mouse models of human cancer. METHODS: Intact tissue of the androgen-dependent human prostate cancer cell line, LNCaP, was implanted on the ventral lateral lobes of the prostate gland by surgical orthotopic implantation (SOI) in a series of 20 nude mice. Mice were autopsied, and histopathological examination of primary tumors and relevant organs was done to identify and quantitate micrometastasis. RESULTS: Eighteen of 20 animals transplanted with LNCaP by SOI had tumor growth. Mean primary tumor weight in the prostate was 9.24 g at time of necropsy. Sixty-one percent of the transplanted animals had lymph node metastasis. Forty-four percent had lung metastasis. Mean survival time was 72 days, indicating a high degree of malignancy of the tumor. CONCLUSIONS: The extensive and widespread lung metastasis as well as lymph node metastasis following orthotopic implantation of LNCaP in nude mice and the short survival time provide a high-malignancy nude model of the LNCaP human prostate tumor.     

bFGF及其抗体对移植前列腺癌生长影响的研究

目的探讨碱性成纤维细胞生长因子（bFGF）及其抗体对裸鼠人前列腺癌移植瘤生长的影响和作用机制。方法建立人前列腺癌细胞系（DU-145）细胞裸鼠皮下移植瘤动物模型,观察移植肿瘤生长及荷瘤裸鼠状况,观察bFGF与bFGF抗体对裸鼠皮下瘤生长状况的影响;应用免疫组织化学方法检测肿瘤组织中增殖细胞核抗原（PCNA）和CD34的表达。结果 1bFGF治疗组移植瘤重量和体积分别比对照组显著增多,移植瘤组织中PCNA指数和微血管密度（MVD）也显著提高;2bFGF抗体治疗组移植瘤体积重量和体积比对照组均显著减少,移植瘤组织中PCNA指数和MVD也显著降低。结论 bFGF能促进前列腺癌细胞的增殖生长,bFGF抗体则能抑制肿瘤的细胞生长,其作用机制与调控肿瘤细胞的增殖和血管形成密切相关。     

A new serially transplantable human prostatic cancer (HONDA) in nude mice

A new serially transplantable human prostatic cancer (HONDA) in nude mice was established from a patient with metastatic prostate carcinoma. The tumor grows well in male nude mice. Doubling time of the tumor weight at passage #13 was 9.5 +/- 0.87 days (mean +/- SD). The tumor retains the original histological features of adenocarcinoma even after 6 years of continuous passage. High levels of human prostatic acid phosphatase were detected by radioimmunoassay in sera from the tumor-bearing mice. The tumor cells contain human prostate specific antigen. Electron microscopy showed particles resembling type A retroviruses in cisterns of endoplasmic reticulum, and particles resembling type C retroviruses in the intercellular space of the tumor cells. The tumor grew well in female mice treated with testosterone, but not in untreated female mice or castrated male mice.     

Regulation of prostatic carcinoma cell proliferation and secretory activity by extracellular matrix and stromal secretions.

Previous studies from our laboratory have shown that reconstituted basement membrane and stromal secretory products are important regulators of benign prostatic epithelial cell growth and differentiation. In the present study we evaluated the impact of extracellular matrix (ECM) and soluble stromal secretory products on the proliferation and secretory activity of the androgen-responsive prostatic carcinoma cell line LNCaP. In these studies, dihydrotestosterone (DHT) was a potent mitogen for LNCaP cells cultured on plastic or on type I collagen. The growth response to DHT was greatly attenuated when LNCaP cells were grown on prostatic stromal ECM. Cells grown on stromal ECM also exhibited clustered morphology compared to the monolayer growth observed on plastic and secreted elevated levels of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP). These findings indicate that cultivation of LNCaP on stromal ECM will promote the expression of differentiated functions. In additional studies, stromal cell conditioned medium (SCM) significantly increased PSA/PAP secretion by LNCaP cells in the presence of 10 nM DHT. The enhancement of DHT-induced PSA/PAP secretion by SCM was most pronounced when LNCaP cells were grown on stromal ECM. SCM did not significantly alter LNCaP proliferation. These studies indicate that prostatic stromal ECM and soluble secretory products will promote differentiated function in cultured LNCaP cells. In addition, we show that DHT can act as either a growth or differentiation-promoting stimulus depending on the presence of stromal factors.     

Inhibition of orthotopic growth and metastasis of androgen-sensitive human prostate tumors in mice by bioactive soybean components

BACKGROUND: Systematic analysis of the influence of diet on the initiation and progression of prostate cancer is often difficult in human populations, for which dietary variables overlap a diversity of genetic backgrounds and social behaviors. Animal models that emulate human prostate cancer allow experimental analysis of the mechanisms of action of nutritional agents that show anti-prostate cancer activity. METHODS: We have used an orthotopic implant model to characterize the in vivo response of androgen-sensitive LNCaP prostate tumors to three well-characterized soy dietary supplements: isoflavone depleted soy protein, soy phytochemical concentrate (SPC), and genistin. RESULTS: In male SCID mice orthotopically implanted with the androgen-sensitive human prostate cell line LNCaP, dietary supplements of soy protein, genistin, and SPC reduced primary tumor weight by 42% (P = 0.07), 57% (P < 0.05) and 70% (P < 0.005), respectively. All three soy supplements significantly increased tumor apoptosis and decrease microvessel density, with no significant change in tumor proliferation. Each supplement produced a distinct serum androgen response, with genistin producing the greatest decrease in total serum testosterone and dihydrotestosterone (DHT) (P < 0.05) and the greatest increase in testosterone to DHT ratio (P < 0.05) and soy protein the greatest decrease in bioactive androgen (P < 0.05). Only SPC significantly inhibited metastases to lymph nodes and lungs, and only SPC produced a significant increase in tumor p53 expression. CONCLUSION: Taken together, these data suggest that the anti-prostate cancer activity of dietary soy protein, soy phytochemicals, and genistin use different molecular pathways. In addition, we have demonstrated that this animal model can be used in the design of dietary strategies for prostate cancer prevention and therapy.