Androgen deprivation therapy remains the mainstay of medical treatment for advanced prostate cancer. Commonly, this is achieved with medical androgen deprivation rather than surgical intervention as the permanence and psychological effects of the latter are unacceptable for most patients. Degarelix is a third generation antagonist of luteinizing hormone-releasing hormone (LHRH, also termed gonadotropin-releasing hormone) for the first-line treatment of androgen-dependent advanced prostate cancer. Degarelix acts directly on the pituitary receptors for LHRH, blocking the action of endogenous LHRH. The use of degarelix eliminates the initial undesirable surge in gonadotropin and testosterone levels, which is produced by agonists of LHRH. Degarelix is the most comprehensively studied and widely available LHRH antagonist worldwide. Clinical trials have demonstrated that degarelix has a long-term efficacy similar to the LHRH agonist leuprolide in achieving testosterone suppression in patients with prostate cancer. Degarelix, however, produces a faster suppression of testosterone and prostate-specific antigen (PSA), with no testosterone surges or microsurges, and thus prevents the risk of clinical flare in advanced disease. Recent clinical trials demonstrated that treatment with degarelix results in improved disease control when compared with an LHRH agonist in terms of superior PSA progression-free survival, suggesting that degarelix likely delays progression to castration-resistant disease and has a more significant impact on bone serum alkaline phosphatase and follicle-stimulating hormone. Degarelix is usually well tolerated, with limited toxicity and no evidence of systemic allergic reactions in clinical studies. Degarelix thus represents an important addition to the hormonal armamentarium for therapy of advanced androgen-dependent prostate cancer.
degarelix; GnRH; LHRH; metastatic prostate cancer; androgen-dependent prostate cancer; hormonal therapy
Long-acting luteinizing hormone-releasing hormone (LHRH) agonists, such as goserelin, have been used for locally advanced and metastatic prostate cancer for many years and are the main forms of androgen deprivation therapy (ADT). Acting on pituitary LHRH receptors, they initially stimulate a transient rise in serum follicle-stimulating hormone (FSH) and LH. Long-term administration of an LHRH analogue will eventually lead to down regulation of LHRH receptors, thus suppressing FSH and LH secretion. This in turn suppresses testosterone production hence achieving and maintaining androgen deprivation. This case highlights the potential anomaly of a sustained elevated serum testosterone in the context of newly diagnosed locally advanced prostate cancer with a co-existing pituitary macroadenoma after administration of LHRH analogues. Alternative methods of androgen deprivation must be considered in such patients.
We examined the serum levels of testosterone (T) (total and bioavailable) dehydroepiandrosterone (DHEA), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prostate-specific antigen (PSA) in men receiving treatment with luteinizing hormone releasing-hormone (LHRH) agonists for metastatic prostate cancer. In doing this, we want to determine the efficacy of these agents in lowering T levels and whether a possible relationship exists between PSA values, as a surrogate measure of tumour activity, and hormone levels.
This was a single centre prospective study of patients on LHRH agonists. Of all the 100 eligible patients, 31 did not qualify (10 were receiving their first injection, 13 were on intermittent hormonal therapy, 7 refused to enter the trial and 1 patient’s blood sample was lost). Therefore in total, 69 patients were included in the final analysis. Each patient had their blood sample drawn immediately before the administration of a LHRH agonist. The new proposed criteria of <20 ng/dL (0.69 nmol/L) of total testosterone was used to define optimal levels of the hormone in this population.
Of the 69 patients, 41 were on goserelin injections, 21 on leuprolide, and 7 on buserelin. There was no statistical difference in hormone levels between any of the medications. Overall, 21% of patients failed to reach optimal levels of total testosterone. PSA levels were higher in this group. There was a statistically significant correlation between PSA and testosterone levels, as well as between PSA and FSH. Serum levels of PSA, however, did not correlate with those of bioavailable testosterone.
Failure to reach optimal levels of testosterone occurs in patients on LHRH agonist therapy. Higher PSA values are more commonly found in patients with suboptimal levels of testosterone receiving LHRH analogs, but the clinical importance of this finding has not been established. There is no significant difference with respect to hormonal levels reached among patients on a variety of LHRH agonists. Total testosterone determinations should be considered in patients on LHRH agonist therapy, particularly when the PSA values begin to rise since it may lead to further beneficial hormonal manipulation.
The prostate secretes enzymes and nutrients to promote sperm motility. Recent reports suggest that the prostate may also secrete testosterone, which is believed to be a fuel for prostate tumour growth. The aim of this study was to determine if a difference in serum testosterone levels exists between men on luteinizing hormone releasing-hormone (LHRH) agonists who have undergone radical prostatectomy, radiation or hormone therapy as primary prostate cancer treatment.
Serum testosterone levels were evaluated in 165 consecutive prostate cancer patients using LHRH analogues for >3 months. We excluded patients receiving either radiation or chemotherapy at time of time of testosterone measurement. Patients were classified based on primary treatment: (1) radical prostatectomy; (2) radiation; or (3) primary hormone therapy. We used one-way ANOVA to compare testosterone levels. Pearson correlation was used to correlate testosterone with prostate-specific antigen (PSA) and time on LHRH agonists. Multivariable linear regression was used to predict serum testosterone levels.
The median (interquartile range) serum testosterone levels were 1.4 (1–1.9), 1.3 (1–1.625) and 1.25 (0.9–1.525) nmol/L for radical prostatectomy, radiation and primary hormone therapy groups, respectively. There was no statistically significant difference in testosterone levels between the groups (p = 0.3). No correlation was found between testosterone and PSA levels or time on LHRH (r = 0.02 and r = 0.01), respectively. Multivariable linear regression showed that none of the clinical variables were predictors of serum testosterone levels.
Our study suggests that primary treatment does not affect serum testosterone levels among men using LHRH analogues.
Antiandrogen withdrawal is a potential therapeutic maneuver for patients with progressive prostate cancer. This study was designed to examine antiandrogen withdrawal effects within the context of a large multi-institutional prospective trial.
Eligibility criteria included progressive prostate adenocarcinoma despite combined androgen blockade. Eligible patients received prior initial treatment with an antiandrogen plus orchiectomy or luteinizing hormone-releasing hormone (LHRH) agonist. Patients were stratified according to type of antiandrogen, type of progression (prostate-specific antigen [PSA] or radiographic), presence or absence of metastatic disease, and prior LHRH agonist versus surgical castration.
A total of 210 eligible and evaluable patients had a median follow-up of 5.0 years; 64% of patients previously received flutamide, 32% bicalutamide, and 3% nilutamide. Of the 210 patients, 21% of patients had confirmed PSA decreases of ≥50% (95% CI, 16% to 27%). No radiographic responses were recorded. Median progression-free survival (PFS) was 3 months (95% CI, 2 months to 4 months); however, 19% had 12-month or greater progression-free intervals. Median overall survival (OS) after antiandrogen withdrawal was 22 months (20 and 40 months for those with and without radiographic evidence of metastatic disease, respectively). Multivariate analyses indicated that longer duration of antiandrogen use, lower PSA at baseline, and PSA-only progression at study entry were associated with both longer PFS and OS. Longer antiandrogen use was the only significant predictor of PSA response.
These data indicate a relatively modest rate of PSA response in patients who were undergoing antiandrogen withdrawal; however, PFS can be relatively prolonged (≥1 year) in approximately 19% of patients.
antiandrogen withdrawal; prostate cancer; PSA; prognosis; survival; secondary hormonal therapy; hormone-refractory prostate cancer
Background. Most patients with metastatic prostate cancer are endocrinologically treated with LHRH agonist, but finally castration-refractory and hormone-refractory cancers occur. Serum testosterone levels get low to “the castration level” by LHRH agonists but may not get low enough against castration-refractory prostate cancer. Methods. As case series, twelve patients suffering from hormone-refractory prostate cancer continuously on LHRH agonist underwent surgical castration. Additionally, one hundred and thirty-nine prostate cancer patients on LHRH agonist or surgical castration were tested for serum total testosterone levels. Results. Surgical castration caused decrease in serum PSA in one out of 12 hormone-refractory prostate cancer patients with PSA reduction rate 74%. Serum total testosterone levels were below the sensitivity threshold (0.05 ng/mL) in 40 of 89 (44.9%) medically castrated patients and 33 of 50 (66.0%) surgically castrated patients (P = .20). Conclusion. Even hormone-refractory prostate cancer patients are candidates for surgical castration because of endocrinological, oncological, and economical reasons.
Hormone therapy is well established for treating patients with prostate cancer and remains the mainstay of the treatment of metastatic and locally advanced disease, this article reviews the rationale for its use, its different forms, and complications and controversies still surrounding some of its modalities. Availability of long-acting synthetic luteinizing hormone-releasing hormone (LHRH) agonists revolutionized the hormonal treatment of prostate cancer, and helped to avoid the emotional and psychological effects related to surgical castration. The depot formula has gained wide acceptance from both patients and physicians. This review emphasizes the newer, long-acting formula, leuprorelin (leuprolide acetate), especially the 6-month formula, its advantage over over shorter-acting depot products, and its potential to become a standard of care for patients eligible for androgen deprivation therapy.
prostate cancer; androgen deprivation therapy (adt); leuprorelin
Androgen deprivation therapy (ADT) has traditionally formed the mainstay of treatment for advanced/metastatic prostate cancer (PCa); however, it is now also having an increasingly important role in earlier stages of disease. Indeed, in patients with locally advanced or high-risk localised disease, the addition of neoadjuvant and adjuvant hormone therapy is now considered the standard of care for those men treated with radical radiotherapy. Although luteinising hormone-releasing hormone (LHRH) agonists have been used for many years as ADT, they may be associated with clinical flare and testosterone breakthrough. Newer hormonal agents continue to be developed, such as gonadotropin-releasing hormone antagonists, which reduce testosterone and prostate-specific antigen levels more rapidly than LHRH agonists, without testosterone flare. This review examines ADT use in combination with radiotherapy to improve outcomes in localised or locally advanced disease, and examines some of the latest developments in hormonal therapy for PCa.
prostate cancer; androgen deprivation therapy; radiotherapy; neoadjuvant hormonal therapy; adjuvant hormonal therapy; GnRH antagonists
Active targeting could increase the efficacy of anticancer drugs. Methotrexate-human serum albumin (MTX-HSA) conjugates, functionalized by luteinizing hormone-releasing hormone (LHRH) as targeting moieties, with the aim of specifically targeting the cancer cells, were prepared. Owing to the high expression of LHRH receptors in many cancer cells as compared to normal cells, LHRH was used as the targeting ligand in this study. LHRH was conjugated to MTX-HSA nanoparticles via a cross-linker. Three types of LHRH targeted nanoparticles with a mean particle size between 120–138 nm were prepared. The cytotoxicity of LHRH targeted and non-targeted nanoparticles were determined on the LHRH positive and negative cell lines. The internalization of the targeted and non-targeted nanoparticles in LHRH receptor positive and negative cells was investigated using flow cytometry analysis and fluorescence microscopy. The cytotoxicity of the LHRH targeted nanoparticles on the LHRH receptor positive cells were significantly more than non-targeted nanoparticles. LHRH targeted nanoparticles were also internalized by LHRH receptor positive cells significantly more than non-targeted nanoparticles. There were no significant differences between the uptake of targeted and non-targeted nanoparticles to the LHRH receptor negative cells. The active targeting procedure using LHRH targeted MTX-HSA nanoparticles could increase the anti-tumoral activity of MTX.
nanoparticles; drug targeting; conjugates; anti-cancer; human serum albumin; LHRH
The effect of the luteinizing hormone-releasing hormone (LHRH) agonist, [D-Trp6,Pro9-NEth]LHRH (LHRHA), on luteinizing hormone (LH) bioactivity was assessed with a rat interstitial cell assay in four men during a 14-d treatment period. Biologic/immunologic (B/I) ratios were unchanged initially with treatment but by day 12 had fallen to levels lower than basal values. Frequent sampling on day 12 revealed blunted gonadotropin responsiveness to LHRHA and absence of spontaneous LH pulsations. Despite continued administration of LHRHA, human chorionic gonadotropin administration resulted in elevated B/I ratios and testosterone levels. Further characterization of the serum immunoreactive LH by Sephadex chromatography revealed a later elution profile during treatment with LHRHA. Thus, LHRHA appears to act, in part, by modification of the bioactivity of LH in man.
Fasting serum lipoproteins were measured in 10 untreated patients with carcinoma of the prostate (Group I), 17 patients with non-malignant urological disorders (Group II), and 12 patients on cyproterone acetate (Group III) and 5 on a long-acting luteinizing hormone-releasing hormone (LHRH) analogue (Group IV) for at least 2 months for carcinoma of the prostate. Total high-density lipoprotein (HDL) cholesterol levels were significantly lower in patients in Group III than all the other groups. Very low-density lipoprotein (VLDL) triglyceride levels were significantly higher in patients in Group III than those in Groups II and IV. These results suggest a potentially adverse effect of cyproterone acetate, but not of the long-acting LHRH analogue, on serum lipids, which is likely to be of relevance only in younger patients.
Prostate cancer is the second leading cause of cancer deaths among men. For patients with hormone-refractory disease, few treatments are available once the tumor has metastasized beyond the prostate. In the present study, two conjugated lytic peptide sequences (named JCHLHRH and JC21LHRH) were designed to target luteinizing hormone-releasing hormone receptors (LHRH-R). Our results indicate that human prostate cancer cell lines were sensitive to both LHRH-conjugated and non-conjugated lytic peptides, with IC50 concentrations for LNCaP cells, 4.4 and 9.1 µM; for DU-145 cells, 4.8 and 5.7 µM; and for PC-3 cells, 4.4 and 8.2 µM, respectively. JCHLHRH and JC21LHRH were nontoxic to normal primary human prostate epithelial cells or to bone marrow stromal cells in co-culture. There were morphological changes in PC-3 cells after 3 hr of exposure to either peptide; after 6 hr, there were significant reductions in cell numbers. Exposure of PC-3 cells for 24 hr to either JCHLHRH or JC21LHRH blocked their growth over 3 days. Since JCHLHRH and JC21LHRH have specificity for and anti-proliferative activity against tumor cells, and low toxicity for normal prostate cells, these peptides could serve as a new type of therapy for prostate cancer.
Lytic Peptides; Prostate Cancer; Luteinizing Hormone-Releasing Hormone; Luteinizing Hormone-Releasing Hormone Receptors; Chemotherapy
Serum concentrations of luteinising hormone and testosterone were measured by radioimmunoassay one, two, four, seven, and 24 hours after the subcutaneous administration of 500 micrograms of the luteinising hormone releasing hormone agonist [D-Trp6, des-Gly-NH2(10)] LHRH ethylamide or [D-Ser(TBU)6, des-Gly-NH2(10)]LHRH ethylamide in patients who had previously received daily treatment with these peptides for 0, 1, 6, 12, 18, and 24 months. No increase in the serum concentrations of luteinising hormone or testosterone were detected at any time between one and 24 months' treatment. The data show that daily subcutaneous administration of the two luteinising hormone releasing hormone agonists used at the appropriate dose can maintain concentrations of serum androgens equivalent to those after castration during long term treatment.
Abiraterone acetate is an orally administered potent inhibitor of cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1 or CYPc17), which is essential for synthesis of testosterone from cholesterol. While decreasing serum testosterone through inhibition of testicular function is the first line of treatment for men with metastatic prostate cancer, residual androgens may still be detected in patients treated with LHRH agonists. Treatment with abiraterone results in rapid, and complete, inhibition of androgen synthesis in the adrenal glands and within the tumor itself. An overall survival benefit of maximal androgen suppression was recently demonstrated in a randomized placebo controlled phase III clinical trial of abiraterone with prednisone versus prednisone in men with metastatic castrate resistant prostate cancer previously treated with docetaxel chemotherapy. Abiraterone’s efficacy demonstrates the importance of androgen signaling in patients with castrate resistant metastastic disease, and the importance of studies of other novel agents such as MDV3100, an androgen receptor inhibitor, that additionally targets androgen receptor translocation. These promising results now pose a new angle to an old problem regarding hormonal therapy and raise new questions about how resistance develops, how to best sequence therapy, and how to optimize combinations with other emerging novel targeted agents.
Abiraterone; Prostate Cancer; CYP17A1; CYP17; CYPc17
Current standard adjuvant therapies for early breast cancer include tamoxifen and chemotherapy, depending on the disease prognosis and menopausal status. Luteinizing hormone-releasing hormone (LHRH) analogues offer a different approach to the management of early breast cancer in pre- and perimenopausal women. The most widely studied LHRH analogue is goserelin. It acts on the hypothalamic-pituitary axis to suppress ovarian function, decreasing luteinizing hormone and oestradiol levels to post-menopausal values. Pooled data from 228 premenopausal and perimenopausal patients with advanced breast cancer enrolled in 29 studies worldwide demonstrated an objective response rate for goserelin, 3.6 mg, of 36.4%, with a median duration of response of 44 weeks. These results fall well within the ranges of reported response rates for ovarian ablation and for tamoxifen in similar patient populations. By virtue of its mode of action, goserelin does not stimulate the ovaries and is unlikely to have detrimental effects on the endometrium. In addition, given that goserelin has no oestrogen agonist-like effects, unlike tamoxifen, there is no potential for tumour stimulation in those patients becoming resistant to treatment. Goserelin is generally well tolerated, and the main side-effects are related to ovarian suppression, which is potentially reversible. Preliminary results in premenopausal women with early breast cancer indicate that endocrine treatment with goserelin plus tamoxifen may be as effective as standard combination chemotherapy (cyclophosphamide-methotrexate-5-fluorouracil), but has significantly less acute toxicity. A number of large, randomized trials are now in progress to assess the potential role of goserelin as adjuvant therapy for early breast cancer.
Analogues of luteinising hormone releasing hormone (LHRH) have recently been introduced as an alternative to surgical orchidectomy in prostate cancer, but there has been concern about the economic costs of long-term treatment. The paper presents a comparison of costs for LHRH analogues versus orchidectomy in patients with advanced prostate cancer. The cost for the surgical procedure was estimated using data on patients treated with orchidectomy in Stockholm County, Sweden, during 1981-86. Estimates of costs for treatment with a depot LHRH analogue was based on observed treatment times among patients with symptomatic prostate cancer in a British randomised clinical trial of medical castration versus surgical orchidectomy. The average cost for orchidectomy was estimated at 2,580 pounds i.e. 7-31% less than for treatment with a depot LHRH analogue (2,760 pounds-3,380 pounds) assuming a mean treatment time in the range 19-23 months. The most cost-effective policy for castration was found to be initial treatment with an LHRH analogue followed by deferred orchidectomy after about 2 years among long-term responders. This policy would obviate the need for surgery in about 85% of the patients and the average cost (1,900 pounds) would be about 26% lower compared to that of a policy of primary orchidectomy in all patients.
Breast cancer is the leading cancer in women of reproductive age; more than a quarter of women diagnosed with breast cancer in the US are premenopausal. A common adjuvant treatment for this patient population is chemotherapy, which has been shown to cause premature menopause and infertility with serious consequences to quality of life. Luteinizing-hormone-releasing hormone (LHRH) agonists, which induce temporary ovarian function suppression (OFS), has been shown to be a useful alternative to chemotherapy in the adjuvant setting for estrogen-receptor-positive breast cancer patients. LHRH agonists have the potential to preserve fertility after treatment, thus, reducing the negative effects on a patient’s reproductive health. However, little is known about the association between a patient’s underlying degree of OFS and disease-free survival (DFS) after receiving LHRH agonists. Specifically, we are interested in whether patients with lower underlying degrees of OFS (i.e. higher estrogen production) after taking LHRH agonists are at a higher risk for late breast cancer events. In this paper, we propose a latent class joint model (LCJM) to analyze a data set from International Breast Cancer Study Group (IBCSG) Trial VIII to investigate the association between OFS and DFS. Analysis of this data set is challenging due to the fact that the main outcome of interest, OFS, is unobservable and the available surrogates for this latent variable involve masked event and cured proportions. We employ a likelihood approach and the EM algorithm to obtain parameter estimates and present results from the IBCSG data analysis.
joint modeling; latent class model; EM algorithm; masked event; cured proportion; breast cancer
To assess the hormonal effects of Fem7® (Merck, KGaA, Darmstadt, Germany) 100 μg transdermal oestrogen patches on men undergoing first-line androgen-deprivation therapy for prostate cancer.
PATIENTS AND METHODS
PATCH is a multicentre, randomized, phase II trial for men with locally advanced or metastatic prostate cancer, comparing luteinizing hormone-releasing hormone agonist therapy with oestrogen patches. To assess the dosing schedule for the patches, as this was the first time that this brand of patch had been used in men, and to reassure patients and participating clinicians, the Independent Data Monitoring Committee agreed to early release of hormonal data from this study.
Oestradiol, testosterone and prostate-specific antigen (PSA) levels are presented for the first group of 14 patients who received the patches (with 1 withdrawal) and for whom there were ≥12 weeks of follow-up by March 2007. After 12 weeks, testosterone levels (nmol/L) in eight of the 13 patients were <1.7, two were 1.7–2 and three were >2. The median (range) serum oestradiol levels was 442 (52.1–1542) pmol/L and all patients had a PSA response, with eight having a PSA level of <4 ng/mL.
These results confirm that oestrogen patches produce castrate levels of testosterone and concomitant PSA responses. They also highlighted the potential differences between different brands of oestrogen patches, and the need to monitor hormonal response, toxicity and efficacy until more experience with oestrogen patches for this clinical indication is obtained. The number of patches recommended in the PATCH study has now been increased.
transdermal oestrogen patches; hormone therapy; prostate cancer; randomized controlled trial
Four male transsexual subjects were given a superactive luteinizing hormone-releasing hormone (LHRH) analogue, D-tryptophan-6-LHRH at daily doses of 100 micrograms for 3--6 mo. A decrease in beard growth, acne, and erectile potency was noted; the latter was documented objectively with the recordings of nocturnal penile tumescence episodes. Plasma testosterone and dihydrotestosterone levels fell to castrate values; basal prolactin and luteinizing hormone levels showed a small decline, whereas the acutely releasable luteinizing hormone was significantly suppressed. A rise of plasma testosterone from castrate to normal levels was demonstrable with the use of human chorionic gonadotropin. Discontinuation of treatment led to a normalization of erectile potency and plasma testosterone. The suppression of Leydig cell function by D-tryptophan-6-LHRH might have wide application in reproductive biology and in endocrine-dependent neoplasia (where it could replace surgical castration).
Leuprolide is an established luteinizing hormone–releasing hormone (LHRH) agonist used as first-line treatment in advanced prostate cancer. As different formulations and dosing schedules are likely to have economic implications, we aimed to evaluate their efficacy, safety, and costs in nine European countries: Austria, Belgium, Czech Republic, Hungary, Italy, Latvia, Netherlands, Poland, and Portugal.
Database searches identified 13 clinical trials of leuprolide 1- (1 M), 3- (3 M) and 6-monthly (6 M). Only data on leuprolide with Atrigel were compared for all three formulations, which had the same efficacy, safety, and adherence. Cost-minimization analysis accounting for cost of Eligard®, specialist consultations, and diagnostics during up to 12 months follow-up was conducted. The perspective was that of public payers.
No significant differences were observed in the percentages of intention-to-treat patients achieving testosterone levels ≤ 50 ng/dL following treatment with Eligard® 1 M (93.3%), 3 M (98.3%), and 6 M (97.3%) (P > 0.05), and adverse event profiles of the three formulations were comparable. Overall, 6 M was the least expensive, with average total annual costs from €788 (Belgium) to €1839 (Portugal). The 3 M option was between 2.5% (Hungary) and 37.6% (Belgium) more expensive than 6 M; 1 M formulation was the most expensive, with costs 15.5% and 151.6% more expensive than 6 M for those countries, respectively. The 3 M option was 11.2%–45.3% less expensive than 1 M. Total costs were associated with frequency of visits for injection and monitoring. The 1 M required twelve visits, 3 M 4.4–4.8 visits, and 6 M 2.1–2.3 visits. Up to 50% additional visits could be funded with the savings resulting from switching eligible patients from 1 M and 3 M to 6 M. Results were stable in univariate and probabilistic sensitivity analyses.
Eligard® formulations offer comparable efficacy and safety, but different dosing schedules require different number of visits. The 6 M formulation offers the greatest cost savings and should be considered the treatment of choice in eligible patients in Europe.
prostate; cancer; androgen; leuprolide; Eligard; cost-effectiveness
Irreversible chemical programming of monoclonal aldolase antibody (mAb) 38C2 has been accomplished with β-lactam equipped mono- and bifunctional targeting modules, including a cyclic-RGD peptide linked to either the peptide (D-Lys6)-LHRH or another cyclic RGD unit and a small-molecule integrin inhibitor SCS-873 conjugated to (D-Lys6)LHRH. We also prepared monofunctional targeting modules containing either cyclic RGD or (D-Lys6)-LHRH peptides. Binding of the chemically programmed antibodies to integrin receptors α(v)β(3) and α(v)β(5) and to the luteinizing hormone releasing hormone receptor were evaluated. The bifunctional and bivalent c-RGD/LHRH and SCS-783/LHRH, the monofunctional and tetravalent c-RGD/c-RGD, and the monofunctional bivalent c-RGD chemically programmed antibodies bound specifically to the isolated integrin receptor proteins as well as to integrins expressed on human melanoma M21 cells. c-RGD/LHRH, SCS-783/LHRH, and LHRH chemically programmed antibodies bound specifically to the LHRH receptors expressed on human ovarian cancer cells. This approach provides an efficient, versatile, and economically viable route to high-valency therapeutic antibodies that target defined combinations of specific receptors. Additionally, this approach should be applicable to chemically programmed vaccines.
A sterically stabilized, mitoxantrone-loaded liposome, tailored to target luteinizing hormone-releasing hormone (LHRH) receptor overexpressing cells, was developed to promote the efficiency of intracellular delivery of mitoxantrone through receptor-mediated endocytosis. Liposomes were prepared by lipid film hydration and an ultrasound dispersion process. Thiolated gonadorelin with affinity for the LHRH receptor was chemically coupled to N-[(3-maleimide-1-oxopropyl) aminopropyl polyethylene glycol-carbamyl] distearoyl-l-phosphatidyl-ethanolamine via a thioether bond and subsequently inserted into polyethylene glycol-grafted liposomes. The liposome was characterized in terms of its size, ligand density, drug loading, and leakage properties. The targeting nature and antitumor effects of the liposomes were evaluated in vitro using cultured MCF-7 breast cancer cells. A protein assay of ligand coupling to the liposomal surface indicated that more than 60% of the LHRH peptides were inserted into the liposome bilayer. Up to 1.0 mg/mL of stable liposomal mitoxantrone loading was achieved, with approximately 98% of this being entrapped within the liposomes. In vitro cell culture studies revealed that the gonadorelin-modified liposomes bound to their target cells had significantly higher affinity and better antitumor efficiency than generic drug-loaded liposomes. These events were presumed to occur through specific interactions of the LHRH with its cognate receptors on the cell surface. It was concluded that the targeting properties of the delivery system would potentially improve the therapeutic benefits of mitoxantrone, as compared with nontargeted liposomes.
mitoxantrone; liposome; luteinizing hormone-releasing hormone receptor; tumor targeting
The standard hormonal therapy with currently available antiandrogens and the leutinizing hormone releasing hormone (LHRH) analogs is not effective in the hormone-refractory stage of prostate cancer due to changes in androgen receptor (AR) signaling axis. In this refractory stage, AR continues to play a significant role in the growth of cancer cells even though the cancer cells are no longer dependent on the level of circulating androgens.
A series of 11β-Δ9-19 nortestosterone compounds were designed through structure-based rationale and tested for their binding affinity against AR and glucocorticoid receptor (GR) using fluorescence polarization assays, their agonistic ability to induce AR dependent transcription using PSA-driven report gene assays, and their growth inhibitory affects against a series of AR positive (LAPC4, LNCap, and CWR22R) and negative human prostate cancer cell lines (PC3) using MTT cell proliferation assays.
This study proposes the design of novel bifunctional antiandrogens based on the conjugation of 11β and/or 7α-Δ9-19 nortestosterone class of steroidal compounds to the synthetic ligand for FK506-binding proteins. As a critical step towards the development of bifunctional antiandrogens, highly potent and AR-specific lead compounds were identified using in vitro data. The lead compounds identified in this study possessed low binding affinity for GR, indicating the absence of undesirable antiglucocorticoid activity.
The results of this study validate our drug discovery rationale based on the structural biology of AR and pave the pay for future development of bifunctional compounds in order to block AR function in hormone refractory stage of prostate cancer.
prostate cancer; bifunctional; antiandrogens; FKBP; SLF
The effects of steroid hormones are pleiotropic. Similarly, non-steroidal oestrogen receptor antagonists such as tamoxifen exert partial agonistic effects with a species- and tissue-specific pattern. Conversely, little is known of the biological effects of non-steroidal anti-androgens, whose role has been investigated in the palliative treatment of prostate cancer. We studied the effects of the non-steroidal anti-androgen nilutamide on parameters of red blood cells, an androgen-dependent cell compartment, in 24 men with prostate cancer and compared the results with those obtained in 38 historical control patients treated with D-tryptophan-6-LHRH. Administration of the anti-androgen induced a limited rise in testosterone concentrations (from 14.1 +/- 1.8 up to a maximum of 19.6 +/- 2.3 nmol l-1) and a significant increase with time in haemoglobin and haematocrit (y = 12.6 g dl-1 + 0.15 months and y = 37.3% + 0.46 months respectively, P = 0.008 for both), while no change occurred in red blood cell count (y = 4.19 x 10(6) mm-3 + 0.02 months, P = 0.2). Conversely, no variation in erythroid parameters was observed in the patients treated with the LHRH analogue (haemoglobin = 12.7 + 0.02 months, P = 0.59; haematocrit = 38.1 + 0.02 months, P = 0.9; red blood cells = 4.34 x 10(6) mm-3 + 0.15 months, P = 0.4). The difference between the linear regression slopes of haemoglobin in the two treatment groups was significant (F-ratio = 3.39, P = 0.03). While the stimulation of erythropoiesis induced by the anti-androgen might be due to incomplete neutralisation of endogenous androgens at the bone marrow level, a cell-specific agonistic effect of the drug cannot be excluded, thus calling into question the designation of pure antagonists which has been attributed to this class of compounds. Ongoing randomised trials should address this issue.
Almost all prostate cancers respond to androgen deprivation treatment but many recur. We postulated that risk of hormone escape -frequency and delay- are influenced by hormone therapy modalities. More, hormone therapies induce crucial biological changes involving androgen receptors; some might be targets for escape prevention. We investigated the relationship between the androgen deprivation treatment and the risk of recurrence using nude mice bearing the high grade, hormone-dependent human prostate cancer xenograft PAC120. Tumor-bearing mice were treated by Luteinizing-Hormone Releasing Hormone (LHRH) antagonist alone, continuous or intermittent regimen, or combined with androgen receptor (AR) antagonists (bicalutamide or flutamide). Tumor growth was monitored. Biological changes were studied as for genomic alterations, AR mutations and protein expression in a large series of recurrent tumors according to hormone therapy modalities. Therapies targeting Her-2 or AKT were tested in combination with castration. All statistical tests were two-sided. Tumor growth was inhibited by continuous administration of the LH-RH antagonist degarelix (castration), but 40% of tumors recurred. Intermittent castration or complete blockade induced by degarelix and antiandrogens combination, inhibited tumor growth but increased the risk of recurrence (RR) as compared to continuous castration (RRintermittent: 14.5, RRcomplete blockade: 6.5 and 1.35). All recurrent tumors displayed new quantitative genetic alterations and AR mutations, whatever the treatment modalities. AR amplification was found after complete blockade. Increased expression of Her-2/neu with frequent ERK/AKT activation was detected in all variants. Combination of castration with a Her-2/neu inhibitor decreased recurrence risk (0.17) and combination with an mTOR inhibitor prevented it. Anti-hormone treatments influence risk of recurrence although tumor growth inhibition was initially similar. Recurrent tumors displayed genetic instability, AR mutations, and alterations of phosphorylation pathways. We postulated that Her-2/AKT pathways allowed salvage of tumor cells under castration and we demonstrated that their inhibition prevented tumor recurrence in our model.