Androgen-dependent Prostate Carcinoma Research Articles

Thalidomide up-regulates prostate-specific antigen secretion from LNCaP cells.

Thalidomide has been shown to have species- and metabolic-dependent antiangiogenic activity in vitro and in vivo, suggesting its potential in treating human angiogenesis-dependent pathologies such as solid tumors. Based on promising preclinical studies, thalidomide has entered phase II clinical trials for prostate, brain, breast cancer, and Kaposi's sarcoma. However, the antiangiogenic mechanism of action is largely unresolved, as are its effects on tumor-associated gene expression, cytokine secretion, etc. We have investigated the effects of thalidomide on: 1) the secretion of prostate-specific antigen (PSA) in a human androgen-dependent prostate cell line; 2) growth and viability of human prostate cells; and 3) differential gene expression profiles of thalidomide-treated vs untreated human prostate cells. A human androgen-dependent prostate carcinoma cell line (LNCaP) and a human androgen-independent prostate carcinoma cell line (PC-3) were incubated with thalidomide 0.6, 6, or 60 microg/mL for 5-6 days. Secreted PSA from LNCaP cells was measured using a commercial enzyme-linked immunosorbant assay. Cell viability studies were conducted in both LNCaP and PC-3 cells using the same thalidomide concentrations. Furthermore, the differential gene expression of thalidomide-treated LNCaP cells was compared to that of untreated control cells using a commercially available human cancer cDNA expression array system. Thalidomide-treated LNCaP cells demonstrated increased PSA/cell levels at all concentrations tested compared to untreated control cells. Thalidomide demonstrated a cytostatic effect in LNCaP cells but had no appreciable effect on PC-3 cell viability compared to untreated control cells. Comparison of cDNA expression arrays hybridized with thalidomide-treated LNCaP cDNA probes suggests that thalidomide may up- or downregulate expression of angiogenesis-related genes, i.e., vitronectin, but these differential effects require further verification. Thalidomide over a range of doses has demonstrated nontoxic, cytostatic activity in LNCaP cells and significant upregulation of LNCaP cell PSA secretion in vitro. Furthermore, preliminary data from cDNA nucleic acid arrays of thalidomide-treated LNCaP cells suggest that thalidomide upregulates a potential angiogenic modulatory protein, the vitronectin precursor, which may eventually link thalidomide's antiangiogenic activity with modulation of angiogenic vascular integrin pathways.

Effect of the dual 5 α-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-5 α-androst-1-ene-17 β-carboxamide] is a novel, potent and selective dual 5 α-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 5 α-reductase inhibitors in the hormonal therapy of prostatic cancer.

A Novel Human Prostate-Specific, Androgen-Regulated Homeobox Gene (NKX3.1) That Maps to 8p21, a Region Frequently Deleted in Prostate Cancer

We have isolated a prostate-specific gene (NKX3.1) in humans that is homologous to theDrosophilaNK homeobox gene family. Northern blot analyses indicate that this gene is expressed at high levels in adult prostate and at a much lower level in testis, but is expressed little or not at all in several other tissues. In an androgen-dependent prostate carcinoma line, LNCaP,NKX3.1mRNA is expressed at a basal level that was increased markedly upon androgen stimulation; theNKX3.1mRNA was undetectable in several other human tumor cell lines including two androgen-independent prostate carcinoma lines. TheNKX3.1gene maps to chromosome band 8p21, a region frequently reported to undergo a loss of heterozygosity associated with tissue dedifferentiation and loss of androgen responsiveness during the progression of prostate cancer. Based on these data we propose thatNKX3.1is a candidate gene for playing a role in the opposing processes of androgen-driven differentiation of prostatic tissue and loss of that differentiation during the progression of prostate cancer.

Active immunization against LHRH alone or combined with LHRH-analogue treatment impedes growth of androgen-dependent prostatic carcinoma.

To determine whether active immunization against LHRH can serve as treatment for androgen-dependent prostatic carcinoma. Male rats of Copenhagen X Fisher strain, implanted with Dunning R-3327 prostatic carcinoma cells were either immunized against LHRH, treated with LHRH-antagonist, or received a combined treatment of active immunization against LHRH and LHRH-antagonist. Testicular histology was consistent with infertility in all treatment groups. The rate of tumor growth was inhibited by all three treatment regimens. Tumor size increased by 3.8 +/- 1.4 cm2 in the LHRH-antagonist group, 3.2 +/- 1.1 cm2 in the immunized group, and 1.0 +/- 0.4 cm2 in the combined treatment group, as compared to 8.2 +/- 2.6 cm2 in non-treated control group. LHRH-antagonist administration combined with immunization against LHRH appeared to exert a synergistic effect. This may be due to the blockade of prostatic LHRH-like receptors by the antagonist, while androgen depletion was rapidly achieved by LHRH-antagonist, and maintained by continued gonadotropin suppression caused by active immunization against LHRH once antagonist treatment had been discontinued.

Isolation of cDNAs that are differentially expressed between androgen‐dependent and androgen‐independent prostate carcinoma cells using differential display PCR

In the development of prostate cancer there is an important transition from androgen-dependent growth (which can be treated) to androgen-independent growth (which is beyond medical control). This transition is probably accompanied by genetic changes, resulting in the activation of oncogenes or the inactivation of tumor suppressor genes. In the present manuscript, the isolation of genes that may be involved in advanced, androgen-independent prostate cancer growth is described. Using differential display PCR, 13 cDNAs were isolated representing genes that are differentially expressed between the androgen-dependent prostate carcinoma cell line LN-CaP and the androgen-independent prostate carcinoma cell lines PC-3 and DU 145. These clones were divided into four groups: androgen-responsive genes (TL5, TL25, TL32, and TL35); genes with a marked decreased expression in one of the prostate cancer cell lines (TL27); genes with a marked, increased expression in one or more of the prostate cancer cell lines (TL4, TL16, TL21, and TL22); and genes with minor (but repeatable) changes in expression between prostate cancer cell lines (TL7, TL15, TL18, and TL33). The 13 genes were analyzed for their sequence information, tissue specificity, and androgen responsiveness in order to identify genes of interest. In summary, differential display PCR appears to provide an attractive alternative to existing molecular techniques to screen for differentially expressed genes in prostate cancer cells.

Regulation of androgen receptor expression in the human heterotransplantable prostate carcinoma PC-82.

In vivo effects of androgen withdrawal and substitution on human androgen receptor (hAR) expression were evaluated in the androgen-dependent human prostatic carcinoma tumor line PC-82. By application of several antibodies reactive with different epitopes of the hAR molecule, hAR protein expression was studied in tumor transplants by immunohistochemistry and immunoblotting. hAR messenger RNA (mRNA) levels were quantitated in PC-82 tumor tissue with a S1-nuclease protection assay. Most PC-82 tumor cells (> 97%) from testosterone-supplemented mice displayed nuclear hAR protein expression immunohistochemically. The almost complete reduction of nuclear hAR immunoreactivity within 5 days after androgen withdrawal (< 10%) was restored after androgen substitution within 1 day. The immunochemical data were confirmed by Western blot analysis. In contrast, no significant changes were observed in hAR mRNA content of PC-82 cells after 5 days of androgen withdrawal. Correlating hAR expression with proliferative activity of PC-82 tumor tissue during endocrine manipulation, a rapid, castration-induced decline of the percentage of bromodeoxyuridine-labeled cells accompanied the loss of hAR. Androgen substitution in castrated male mice restored the proliferative activity. However, this increase of proliferative activity lagged at least 24 h behind the normalization of the hAR protein level. In contrast to the steroid receptor down-regulation by homologous ligands observed in other experimental models, our data support the concept of hAR up-regulation by androgen. Since the hAR mRNA content of PC-82 tumor tissue was hardly affected by castration, expression of the hAR in PC-82 is thought to be modulated by translational and/or posttranslational mechanisms.

Assessment of the Critical Level of Androgen for Growth Response of Transplantable Human Prostatic Carcinoma (PC-82) in Nude Mice

The androgen dependent prostatic carcinoma of human origin, PC-82, was used as a model system to investigate the effect of various levels of androgen on the growth of prostatic tumor tissue. Plasma testosterone levels in mice were correlated to tumor growth and intratumor concentrations of testosterone and 5α-dihydrotestosterone. PC-82 tumor burden remained stable at plasma testosterone levels of 0.8 nmol/1., whereas tumor growth occurred at higher levels and tumor regression was observed at lower plasma levels. This critical level of testosterone corresponded with intratumor testosterone and 5α-dihydrotestosterone concentrations of six to 10 and three to four pmol/gm. tissue, respectively, which are significantly above the levels found in castrated non-supplemented animals (3.1 and 1.4 pmol/gm. respectively). This indicates that remaining concentrations of dihydrotestosterone, which amount to two to three times the castrate level, are not stimulatory for tumor growth in the model of the androgen dependent PC-82 tumor.

Inhibition of growth of experimental prostate cancer with sustained delivery systems (microcapsules and microgranules) of the luteinizing hormone-releasing hormone antagonist SB-75.

Inhibitory effects of the sustained delivery systems (microcapsules and microgranules) of a potent antagonist of luteinizing hormone-releasing hormone N-Ac-[3-(2-naphthyl)-D-alanine1, 4-chloro-D-phenylalanine2, 3-(3-pyridyl)-D-alanine3, D-citrulline6, D-alanine10]LH-RH (SB-75) on the growth of experimental prostate cancers were investigated. In the first experiment, three doses of a microcapsule preparation releasing 23.8, 47.6, and 71.4 micrograms of antagonist SB-75 per day were compared with microcapsules of agonist [D-Trp6]LH-RH liberating 25 micrograms/day in rats bearing Dunning R3327H transplantable prostate carcinoma. During 8 weeks of treatment, tumor growth was decreased by [D-Trp6]LH-RH and all three doses of SB-75 as compared to untreated controls. The highest dose of SB-75 (71.4 micrograms/day) caused a greater inhibition of prostate cancer growth than [D-Trp6]LH-RH as based on measurement of tumor volume and percentage change in tumor volume. Doses of 23.8 and 47.6 micrograms of SB-75 per day induced a partial and submaximal decrease, respectively, in tumor weight and volume. Tumor doubling time was the longest (50 days) with the high dose of SB-75 vs. 15 days for controls. The body weights were unchanged. The weights of testes, seminal vesicles, and ventral prostate were greatly reduced in all three groups that received SB-75, and testosterone levels were decreased to nondetectable values in the case of the two higher doses of SB-75. LH levels were also diminished. Similar results were obtained in the second experiment, in which the animals were treated for a period of 8 weeks with microgranules of SB-75. Therapy with microgranules of SB-75 significantly decreased tumor growth as measured by the final tumor volume, the percentage change from the initial tumor volume, and the reduction in tumor weight. The results indicate that antagonist SB-75, released from sustained delivery systems, can produce a state of chemical castration and effectively inhibit the growth of experimental prostate cancers. The efficacy of the antagonist SB-75 in inhibiting androgen-dependent Dunning prostatic carcinoma and the absence of side effects suggest its possible usefulness for the treatment of hormone-sensitive tumors.

Clinical applications of gonadotropin-releasing hormone and gonadotropin-releasing hormone analogs

Investigations have proved the clinical importance of hypothalmic gonadotropin-releasing hormone (GnRH) and its agonistic and antagonistic analogs. A pulsatile pattern of stimulation of specific receptors in the anterior pituitary gonadotrope has been shown to activate pituitary-gonadal function; continuous administration inhibits it. Clinical research has shown promising results in the induction of ovulation using the pulsatile pattern of GnRH administration in patients with hypogonadotropic amenorrhea. Attempts to use GnRH and its agonists to activate the pituitary-gonadal system in patients with idiopathic delayed puberty has proved logistically impractical because of the duration of treatment required to achieve sexual maturation. Treatment of cryptorchidism by intranasal administration 6 times daily for 4 weeks resulted in complete descent in 38% of the 48 boys and partial descent in 28%. For GnRH nonresponders sequential treatment with human chorionic gonadotropin produced an 86.2% success rate. Because of the ability of GnRH agonists to reversibly suppress the pituitary-gonadal axis without side effects it can be used in diseases mediated by gonadal steroids. Successful halting of precocious puberty through the administration of GnRH to suppress the nocturnal release of gonadotropin has been demonstrated. Unlike treatment with progestational agents no side effects are discerned. Continuous administration of GnRH agonist in patients with endometriosis reduces ovarian estrogens and androgens to castration levels mimicking an ovariectomy. This castration effect highlights the potential use of GnRH agonists in the treatment of metastatic breast cancer. The use of GnRH agonists for the treatment of androgen-dependent prostatic carcinoma has induced clinical improvement with nonmetastatic stage 3 disease and pain relief in metastic stage D disease. In polycystic ovary syndrome administration of GnRH agonist shows promising results. As a potential contraceptive GnRH agonists have not yet demonstrated practical advantages. The actions under study include: ovulation inhibition luteolysis induction induction of luteal phase defect and reduction of testosterone production. Numerous antagonistic analogs of GnRH have been synthesized and have shown some potential contraceptive effects in animal studies.