What's new in the treatment of advanced prostate cancer?

DUP1 peptide modified micelle efficiently targeted delivery paclitaxel and enhance mitochondrial apoptosis on PSMA-negative prostate cancer cells

Prostate tumor cell targeted peptide fragment conjugated to the nano drug delivery system is a promising strategy for prostate cancer therapy. In this work, an amphiphilic copolymer Chol–PEG–DUP1 (PEG–cholesterol conjugated with DUP1 peptide) has been synthesized and characterized by proton nuclear magnetic resonance spectrum (¹H NMR). The paclitaxel (PTX) was encapsulated into the Chol–PEG–DUP1 micelles to obtain aqueous formulation with small particle size (within 200 nm) and high drug encapsulating efficiency. The DUP1 modified PTX micelle significantly enhanced the cytotoxicity of paclitaxel to PSMA negative prostate tumor cells (PC-3 cell) as demonstrated by MTT (IC₅₀ = 15.8 μg/mL compared to 68.7 μg/mL of free PTX). Flow cytometry analysis and fluorescence images revealed the DUP1 peptide fragments on the surface of micelles increased drug uptake (2.08-fold) by PC-3 cells. Flow cytometry and immunoblotting analysis showed the DUP1 modified PTX micelle enhanced the mitochondrial apoptosis-inducing capacity of PTX to PC-3 cells. In conclusion, Chol–PEG–DUP1 modified micelle was a reasonable, facile, and economic drug delivery system to target the PSMA-negative prostate cancer.

Multinational, double-blind, phase III study of prednisone and either satraplatin or placebo in patients with castrate-refractory prostate cancer progressing after prior chemotherapy: the SPARC trial

PURPOSE

This multinational, double-blind, randomized, placebo-controlled, phase III trial assessed the efficacy and tolerability of the oral platinum analog satraplatin in patients with metastatic castrate-refractory prostate cancer (CRPC) experiencing progression after one prior chemotherapy regimen.

PATIENTS AND METHODS

Nine hundred fifty patients were randomly assigned (2:1) to receive oral satraplatin (n = 635) 80 mg/m(2) on days 1 to 5 of a 35-day cycle and prednisone 5 mg twice daily or placebo (n = 315) and prednisone 5 mg twice daily. Primary end points were progression-free survival and overall survival (OS). The secondary end point was time to pain progression (TPP).

RESULTS

A 33% reduction (hazard ratio [HR] = 0.67; 95% CI, 0.57 to 0.77; P < .001) was observed in the risk of progression or death with satraplatin versus placebo. This effect was maintained irrespective of prior docetaxel treatment. No difference in OS was seen between the satraplatin and placebo arms (HR = 0.98; 95% CI, 0.84 to 1.15; P = .80). Compared with placebo, satraplatin significantly reduced TPP (HR = 0.64; 95% CI, 0.51 to 0.79; P < .001). Satraplatin was generally well tolerated, although myelosuppression and GI disorders occurred more frequently with satraplatin.

CONCLUSION

Oral satraplatin delayed progression of disease and pain in patients with metastatic CRPC experiencing progression after initial chemotherapy but did not provide a significant OS benefit. Satraplatin was generally well tolerated. These results suggest activity for satraplatin in patients with CRPC who experience progression after initial chemotherapy.

Prostate Cancer - What's New?

Research has shown that prostate specific antigen (PSA) is a tumour marker for diagnosis of cancer prostate with significant prognostic value. Screening studies in North America and Europe have revealed that carcinoma prostate is common. Early detection and treatment improves the quality of life besides preventing deaths due to metastatic prostate cancer. Radical prostatectomy and laparoscopic radical prostatectomy has become the standard treatment for localized prostate cancer in all major uro-oncological centres resulting in reduced mortality. Magnetic resonance imaging and positron emission tomography have helped in detecting local and distant spread of cancer prostate. Revised approach to reduce occurrence of prostate cancer by the use of 5 alpha reductase inhibitors like finasteride and dietary supplements has been instituted. The World Health Organisation (WHO) has recommended lifestyle changes to promote men's health and reduce the incidence of prostate cancer.

Lysosomotropic acid ceramidase inhibitor induces apoptosis in prostate cancer cells

PURPOSE

Alterations in ceramide metabolism have been reported in prostate cancer (PCa), resulting in escape of cancer cells from ceramide-induced apoptosis. Specifically, increased expression of lysosomal acid ceramidase (AC) has been shown in some primary PCa tissues and in several PCa cell lines. To determine if this represents a novel therapeutic target, we designed and synthesized LCL204, a lysosomotropic analog of B13, a previously reported inhibitor of AC METHODS: Prostate cancer cell lines were treated with LCL204 for varying times and concentrations. Effects of treatment on cytotoxicity, sphingolipid content, and apoptotic markers were assessed.

RESULTS

Treatment of DU145 PCa cells resulted in increased ceramide and decreased sphingosine levels. Interestingly, LCL204 caused degradation of AC in a cathepsin-dependent manner. We also observed rapid destabilization of lysosomes and the release of lysosomal proteases into the cytosol following treatment with LCL204. Combined, these events resulted in mitochondria depolarization and executioner caspase activation, ultimately ending in apoptosis

CONCLUSIONS

These results provide evidence that treatment with molecules such as LCL204, which restore ceramide levels in PCa cells may serve as a new viable treatment option for PCa.

Immunotherapy of patients with hormone-refractory prostate carcinoma pre-treated with interferon-gamma and vaccinated with autologous PSA-peptide loaded dendritic cells--a pilot study

PURPOSE

We conducted a pilot trial to assess the feasibility and tolerability of a prime/boost vaccine strategy using interferon-gamma (IFN-gamma) and autologous dendritic cells (DCs) pulsed with HLA-A2-specific prostate-specific antigen (PSA) peptides (PSA-1 [141-150]; PSA-2 [146-156]; PSA-3 [154-163]) for the treatment of 12 patients with hormone refractory prostate carcinoma.

PATIENTS AND METHODS

All patients were vaccinated four times with intracutaneously injected PSA-peptide loaded DCs after subcutaneous administration of IFN-gamma 2 hr before DC administration (50 microg/m(2) body surface). Objectives were safety, clinical benefit, clinical and biochemical response, quality of life, and immunological parameters.

RESULTS

The vaccination was well tolerated without any vaccination-associated adverse events. One partial and one mixed responder were identified, four patients showed stable diseases. Two patients had a decrease and four a slow-down velocity slope in the PSA serum level. All responders showed a positive DTH-response, but only two a slight increase in PSA-peptide specific T-lymphocytes.

CONCLUSION

The immunotherapy with IFN-gamma and PSA-peptide loaded DCs was feasible and well tolerated. The observed responses imply a potential antitumor activity.

Future directions for vaccine-based therapies

During recent years, cancer vaccines have made encouraging progress toward becoming a clinically relevant form of biologic therapy. However, current vaccine approaches have shown only limited success in patients with cancer because of inadequate immune activation. Recent insights into the elements that regulate immune responsiveness have provided new opportunities to enhance the efficacy of cancer vaccines through multiple pathways that involve afferent and efferent arms of the immune system. This article presents a set of emerging strategies that have resulted from our recent efforts to boost tumor-associated antigen-specific immunity and improve patient outcome. These new insights represent important consideration for the design and development of more effective immunotherapies during the next decade.

Restructuring dynamics of DU 145 and LNCaP prostate cancer spheroids

Neoplastic cells acquire multidrug resistance as they assemble into multicellular spheroids. Image analysis and Monte Carlo simulation provided an insight into the adhesion and motility events during spheroid restructuring in liquid-overlay culture of DU 145 and LNCaP human prostate cancer cells. Irregularly shaped, two-dimensional aggregates restructured through incremental cell movements into three-dimensional spheroids. Of the two cultures examined, restructuring was more pronounced for DU 145 aggregates. Motile DU 145 cells formed spheroids with a minimum cell overlay of 30% for 25-mers as estimated by simulation versus 5% for adhesive LNCaP cells in aggregates of the same size. Over 72 h, the texture ratio increased from 0.55 +/- 0.05 for DU 145 aggregates with projected areas exceeding 2000 microm2 to a value approaching 0.75 +/- 0.02 (P < 0.05). For LNCaP aggregates of comparable size, the increase in texture ratio was more modest, less than 15% during the same time period (P < 0.05). Combined, these data suggest that motility events govern the overall rate of spheroid restructuring. This information has application to the chemosensitization of solid tumors and kinetic modeling of spheroid production.

Maspin sensitizes prostate cancer cells to doxazosin-induced apoptosis

Maspin is a mammary serine protease inhibitor or serpin with tumor suppressive and antiangiogenic activity that inhibits tumor motility, invasion and metastasis, at least by its actions on cell membrane and extracellular matrix (ECM) proteins. Previous studies documented that the quinazoline-derived alpha1-adrenoceptor antagonist doxazosin affects the attachment and migration of prostate cancer cells. In this study, we investigated the effect of maspin overexpression on the apoptotic/antiadhesion response of prostate cancer cells to doxazosin. The response of maspin-overexpressing clones of human prostate cancer cells DU-145 to doxazosin was evaluated by determining cell viability, apoptosis and cell proliferation on the basis of the trypan blue exclusion assay/methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay, Hoechst staining and caspase-3 activation, and [(3)H]thymidine incorporation assay. Vascular endothelial growth factor (VEGF), transforming growth factor betaRII (TGFbetaRII), Smad4 (a TGFbeta intracellular effector) and bax expression was evaluated at the mRNA and protein level using reverse transcriptase-polymerase chain reaction and Western blotting, respectively. The effect of doxazosin on cell attachment of maspin-expressing prostate cancer cells was evaluated on collagen- and fibronectin-coated plates. Cell migration was assessed using the wounding assay. In response to tumor necrosis factor-related apoptosis-inducing ligand, DU-145-maspin expressing cells undergo apoptosis, via poly(ADP-ribose) polymerasecleavage and caspase-3 activation. DU-145-maspin cells exhibited higher sensitivity to doxazosin and an earlier temporal activation of caspase-3. The number of apoptotic cells detected in response to doxazosin was significantly higher compared to the neo control (P<0.0001). Doxazosin resulted in dramatic downregulation of the 189 isoform of VEGF in maspin transfectants, while a fivefold induction of Smad4 mRNA expression was detected in those cells after 24 h of treatment. Maspin overexpression in prostate cancer cells resulted in an increased ability to attach to ECM-coated plates, and doxazosin treatment considerably antagonized this effect by decreasing the attachment potential to collagen and fibronectin. The present study supports the ability of maspin to enhance the apoptotic threshold of prostate cancer cells to the quinazoline-based alpha1-adrenoceptor antagonist doxazosin. These findings may have therapeutic significance in the development of antiangiogenic targeting by doxazosin and derivative agents for advanced prostate cancer.

Combined application of RT-PCR and immunohistochemistry on paraffin embedded sentinel lymph nodes of prostate cancer patients

The detection of tumor cells in the sentinel lymph node (SLN) is of great importance for the prognosis of cancer patients. At present, immunohistochemistry and RT-PCR for tumor marker expression are the most sensitive techniques available for this analysis. However, so far, most RT-PCR-based analyses of SLNs have been performed on fresh material, excluding a direct comparison with the (immuno)histologic results. In our view, this does not entirely aid routine diagnosis. We established an efficient method for RNA extraction and RT-PCR from paraffin sections of SLNs from prostate cancer patients and compared the results with the (immuno)histologic data of adjacent sections. Amplifiable RNA was obtained from 133 SLNs of 68 prostate cancer patients. Correlation of PSA-specific RT-PCR with (immuno)histologic findings showed a positive and negative predictive value of 83% and 100%, respectively, for the prostate cancer patients investigated. Four of 12 patients with biochemical relapse, but without (immuno)histologically detectable tumor cells were RT-PCR-positive for PSA. We found that single sections of paraffin-embedded SLNs are suitable for routinely performed RT-PCR. Combined with (immuno)histology, PSA-specific RT-PCR is a revealing supplementary technique for the detection of tumor cells in SLNs of prostate cancer patients.

Phase III trial of satraplatin, an oral platinum plus prednisone vs. prednisone alone in patients with hormone-refractory prostate cancer

Satraplatin is a novel oral platinum (IV) complex that shows activity against hormone-refractory prostate cancer (HRPC) in cisplatin-resistant human tumor lines in phase I and phase II trials. A randomized multicenter phase III trial with a target sample size of 380 patients was initiated in men with HRPC. After 50 randomized patients, the trial was closed to further accrual by the sponsoring company. An ad hoc analysis of all available data is reported here. Eligibility criteria included pathological proof of prostate cancer, documented progression despite prior hormonal manipulation, WHO PS 0-2, and no daily intake of narcotic analgesics. Patients were randomized between satraplatin 100 mg/m(2) for 5 days plus prednisone 10 mg orally BID or prednisone alone. Compliance was excellent. 48/50 patients have progressed and 42 have died, mostly due to prostate cancer. Median overall survival was 14.9 months (95% CI: 13.7-28.4) on the satraplatin plus prednisone arm and 11.9 months (95% CI: 8.4-23.1) on prednisone alone (hazard ratio, HR = 0.84, 95% CI: 0.46-1.55). A >50% decrease in prostrate specific antigen (PSA) was seen in 9/27 (33.3%) in the satraplatin plus prednisone arm vs. 2/23 (8.7%) on the prednisone alone arm. Progression-free survival was 5.2 months (95% CI: 2.8-13.7) on the satraplatin plus prednisone arm as compared to 2.5 months (95% CI: 2.1- 4.7) on the prednisone alone arm (HR = 0.50, 95% CI: 0.28-0.92). This difference is statistically significant (p = 0.023). Toxicity was generally minimal in both arms. This randomized comparison of a combination of satraplatin and prednisone versus prednisone alone supports the antitumor activity of the combination. Its role in the treatment of HPRC remains to be elucidated in an appropriate phase III setting.

Shifting paradigms in prostate cancer; docetaxel plus low-dose prednisone - finally an effective chemotherapy

Until now, the use of systemic chemotherapy for advanced androgen-independent prostate cancer has had very little to offer to patients. However, in 2004, two large randomised trials investigating docetaxel vs. mitoxantrone have both demonstrated survival improvements, and, in one of the trails, improvements in important secondary clinical outcome measures such as pain relief and quality of life measurements. In this current perspective, these two trials are summarised and discussed. It is concluded that, docetaxel every 3 weeks plus low-dose prednisone can be considered standard treatment for patients with androgen-independent disease.

A New Prostate Carcinoma Binding Peptide (DUP-1) for Tumor Imaging and Therapy

Purpose: Prostate carcinomas belong to the most widespread tumors, and their number is increasing. Imaging modalities used for diagnosis, such as ultrasound, computed tomography, and positron emission tomography, often produce poor results. Radiolabeled peptides with high sensitivity and specificity for prostate cancer would be a desirable tool for tumor diagnosis and treatment.

Experimental Design: We used phage display and the prostate-specific membrane antigen–negative cell line DU-145 to identify a peptide. The isolated DUP-1 was tested invitro for its binding specificity, kinetics, and affinity. Internalization of the peptide was evaluated with confocal microscopy. The tumor accumulation in a nude mouse model was analyzed with 131I-labeled DUP-1 in PC-3 and DU-145 prostate tumors as well as in the rat prostate tumor model AT-1.

Results: The synthesized peptide showed rapid binding kinetics peaking at 10 minutes. It shows specific binding to prostate carcinoma cells but low binding affinity to nontumor cells. Peptide binding is competed with unlabeled DUP-1, and a time-dependent internalization into DU-145 cells was shown. Biodistribution studies of DUP-1 in nude mice with s.c. transplanted DU-145 and PC-3 tumors showed a tumor accumulation of 5% and 7% injected dose per gram, and bound peptide could not be removed by perfusion. The rat prostate tumor model showed an increase of radioactivity in the prostate tumor up to 300% in comparison with normal prostate tissue.

Conclusions: DUP-1 holds promise as a lead peptide structure applicable in the development of new diagnostic tracers or anticancer agents that specifically target prostate carcinoma.

Combined ionizing radiation and sKDR gene delivery for treatment of prostate carcinomas

Overexpression of vascular endothelial growth factor (VEGF) and its cognate receptor KDR has been linked to a more aggressive phenotype of human prostate carcinomas. The importance of signal transduction through the VEGF receptor 2 is illustrated by use of soluble KDR, which binds to VEGF and sequesters this ligand before its binding to cellular receptor. Treatment with recombinant adenovirus AdVEGF-sKDR, encoding sKDR under control of the human VEGF promoter, significantly inhibited the proliferation of human vascular endothelial cells and prostate cancer cells. AdVEGF-sKDR infection decreased migration of endothelial 1P-1B cells (61% reduction) and DU145 prostate carcinoma cells (47%) in comparison with AdCMV-Luc-infected control cells. Ionizing radiation upregulated VEGF promoter activity in prostate carcinoma and endothelial cells. AdVEGF-sKDR infection significantly reduced human vascular endothelial and prostate cancer cell proliferation and sensitized cancer cells to ionizing radiation. In vivo tumor therapy studies demonstrated significant inhibition of DU145 tumor growth in mice that received combined AdVEGF-sKDR infection and ionizing radiation versus AdVEGF-sKDR alone or radiation therapy alone. These results suggest that selective transcriptional targeting of sKDR gene expression employing a radiation inducible promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.

Adenovirus-mediated FLT1-targeted proapoptotic gene therapy of human prostate cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is of particular interest in the development of prostate carcinoma therapeutics as it preferentially induces apoptosis of tumor cells. To employ adenoviral vectors for highly efficient and specific TRAIL gene transfer into cancer cells could overcome some potential problems for recombinant TRAIL. The vascular endothelial growth factor receptor FLT-1 is involved in regulation of angiogenesis and tumor growth, invasion, and metastasis of prostate carcinoma. FLT-1 expression is observed in both tumor endothelial cells and prostate cancer cells. We developed an adenoviral vector encoding the TRAIL gene under control of the FLT1 promoter (AdFlt-TRAIL), which produced endothelial and prostate cancer cell death. The combination of ionizing radiation and adenovirus-driven TRAIL expression overcame human prostate cancer cell resistance to TRAIL. Furthermore, in vivo administration of AdFlt-TRAIL at the site of tumor growth in combination with radiation treatment produced significant suppression of the growth of DU145 human prostate tumor xenografts in athymic nude mice. Our results suggest that specific TRAIL delivery employing the FLT1 promoter can effectively inhibit tumor growth and demonstrate the advantage of combination radiotherapy and gene therapy for the treatment of prostate cancer.

Apoptotic impact of alpha1-blockers on prostate cancer growth: a myth or an inviting reality?

BACKGROUND

Pharmacological manipulation or genetic targeting of the major apoptosis regulators, such as bcl-2, caspases, and inhibitors of apoptosis (IAPs), represent clinically attractive avenues towards effective therapeutic strategies for advanced prostate cancer. A wealth of evidence established the alpha(1)-adrenoceptor antagonists to be clinically effective in relieving the symptoms associated with benign prostatic hyperplasia (BPH) by relaxing prostatic smooth muscle tone. This action alone however does not fully account for the long-term clinical response to these drugs in BPH patients.

METHODS

Experimental and retrospective clinical studies provided new evidence supporting a differential growth-suppressing function of two alpha(1)-adrenoceptor antagonists against prostate cancer, independent of an alpha(1)-adrenoceptor mechanism.

RESULTS

The quinazoline-based antagonists, doxazosin and terazosin, induce apoptosis, inhibit cell adhesion to the extracellular matrix (by activating anoikis), and prevent cell invasion and migration of prostate tumor epithelial cells and vascular endothelial cells. Tamsulosin, a sulphonamide-based, clinically effective alpha(1)-adrenoceptor antagonist for BPH treatment, fails to exert a similar apoptotic action against prostate cells. Furthermore, at pharmacologically relevant doses, doxazosin suppresses benign and malignant prostate growth in in vivo experimental models. The effect is characterized by three intriguing features: (a) it is mediated by an alpha(1)-adrenoceptor-independent action, (possibly related to the quinazoline nucleus); (b) it is targeted at the apoptotic process without affecting cell proliferation; and (c) the elevated apoptotic index correlated with symptom score improvement in BPH patients.

CONCLUSIONS

This evidence challenges conventional knowledge of the mechanism of action of alpha(1)-adrenoceptor antagonists, and points to a new therapeutic value for these drugs by providing a differential molecular basis for their anti-tumor efficacy. The present review focuses on the characterization of the apoptotic/anti-angiogenic effect of quinazoline-based alpha(1)-adrenoceptor antagonists against prostate cancer cells and discusses the clinical significance of this action in the prevention and treatment of prostate cancer.

G Proteins in Cancer: The Prostate Cancer Paradigm

Signal transduction research investigating mechanisms of androgen-independent prostate cancer cell proliferation has historically focused on the role of androgen and peptide growth factor receptors. More recent work has raised the idea that intracellular signaling mechanisms triggered by extracellular hormonal factors acting through heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) can also mediate and sustain this pathologic process. Prostate cancer patients with advanced disease express elevated levels of GPCRs and GPCR ligands, suggesting that the GPCR system is activated in the cancerous gland and may contribute to tumor growth. Importantly, inhibition of G protein signaling attenuates prostate cancer cell growth in animal models. The nature of intracellular signaling pathways mediating mitogenic effects of GPCRs in prostate cancer is poorly defined, although the G protein-dependent activation of the Ras-to-mitogen-activated protein kinase pathway has emerged as a critical regulatory event. Activated GPCRs may also exert their mitogenic effects in the prostate by activating the androgen receptor.

[Chemotherapy of hormone refractory prostate carcinoma]

An increasing life expectancy and the growing number of largely healthy older men have lead to more patients with hormone insensitive relapses after palliative hormone or curative therapy for prostate cancer. After 10 years without therapeutic improvement for hormone refractory prostate cancer, the introduction of new substances has led to a revival of chemotherapy. Although a definitive cure is still not possible, such chemotherapy fulfils important palliative criteria-good toleration and an improvement in quality of life-in addition to distinct long-term remission. For example, taxane as a monotherapy or in combination with estramustine is effective and well tolerated while mitoxantrone in combination with prednisolone, although of limited effectiveness, leads to a substantial reduction in symptoms. Although evidence for increased longevity through modern chemotherapy is available, this has still not been definitively demonstrated. The substantial reduction in pain and therapy related morbidity frequently makes chemotherapy for hormone refractive prostate cancer a superior alternative to simple pain and complication management.