Chemotherapy for the treatment of hormone-refractory prostate cancer

Optimization Therapy by Coupling Intermittent Androgen Suppression with Impulsive Chemotherapy for a Prostate Cancer Model

Intermittent androgen suppression in the prostate cancer is often relapsed by the increasing of prostate specific antigen level during the on-treatment. Historically, chemotherapy has had a limited role in the treatment of prostate cancer. However, new agents are showing promise in patients with advanced disease. Intermittent androgen suppression plus chemotherapy in pulsed pattern has become an indispensable clinical scheme for prostate cancer, which is presented to describe the transformation mechanism for three kinds of cancer cells in this paper. The model is then extended to include the residual effect of chemotherapy which suppresses the cancer cells production, thereby preventing the relapse. The optimal controls represent the efficiencies of both intermittent androgen suppression and chemotherapy in suppressing relapse of prostate cancer. Based on an optimal algorithm, numerical simulations are implemented not only to show the optimal durations of on- and off-treatment and chemotherapy dosages but also to present the effectiveness of different strategies in inhibiting the relapse for three types of patients. Results reveal that the optimal intermittent androgen suppression scheme with alterable treatment cycles is pivotal for type I and II patients, in part because it can greatly reduce the on-treatment time and degrade the level of prostate specific antigen. Furthermore, optimal hybrid schedule even averts the relapse of prostate cancer for type II and III patients. Finally, comparing the prostate specific antigen under intermittent androgen suppression schedule with residual effect of chemotherapy to one without residual effect of chemotherapy demonstrates the validity of both our model and algorithms in lessening the prostate specific antigen and decreasing the chemotherapy dosages.

Optimized 68Ga-Labeled Urea-Based PSMA-Targeted PET Tracers for Prostate Cancer

Prostate-specific membrane antigen (PSMA)-targeting radiopharmaceuticals have become some of the most promising tools for the diagnosis and therapy prostate cancer (PCa). The structure of existing PSMA-targeted PET tracers still needs to be optimized to improve their pharmacokinetic properties and tumor-to-background ratio. In this study, we modified the structure of a well-studied PSMA tracer, and six novel tracers with variable hydrophilicity and pharmacokinetics were developed and evaluated both in vitro and in vivo. All of the novel tracers showed high hydrophilicity (log p = −2.99 ± 0.33 to −3.49 ± 0.01), rapid clearance rates (elimination half-times = 15.55 to 35.97 min), and high affinity for PSMA (Ki = 8.11 ± 0.49 to 42.40 ± 2.11 nM) in vitro. Specific cell binding and micro-PET experiments showed that [⁶⁸Ga]Ga-PSMA-Q displayed the highest specific PSMA+ cell uptake (3.75 ± 0.35 IA%/10⁶ at 60 min), tumor uptake (SUVmax = 0.97 ± 0.24 at 60 min p.i.), and tumor-to-muscle ratio (59.33 ± 5.72 at 60 min p.i.), while the tumor-to-muscle ratio was much higher than that of [⁶⁸Ga]Ga-PSMA-617. The results of this study validate the clinical potential of [⁶⁸Ga]Ga-PSMA-Q for PET imaging and further targeted therapy of prostate cancer.

Efficacy and safety of different interventions in castration resistant prostate cancer progressing after docetaxel-based chemotherapy: Bayesian network analysis of randomized controlled trials

Background: Most patients receiving docetaxel-based chemotherapy for castration resistant prostate cancer (CRPC) will eventually progress, and the optimal interventions for these patients are controversial. The objective of our study is to evaluate the clinical efficacy and safety of pharmacological interventions for CRPC patients progressing after docetaxel-based chemotherapy.

Methods: A systematic review and Bayesian network meta-analysis of the literature was carried out according to standard methods. Major electronic databases including PubMed, Web of Science and Embase were searched until Jan 2017. Hazard ratios (HRs) and odds ratios (ORs) with corresponding 95% credible intervals (CrIs) were used to estimate the association.

Results: 17 Randomized Controlled Trials (RCTs) comprising 14 different interventions with 12347 patients were enrolled. Compared with control arms, Abiraterone Acetate (HR: 0.70, 95%CrI: 0.63-0.79), Cabazitaxel (HR: 0.70, 95%CrI: 0.51-0.95) and Enzalutamide (HR: 0.63, 95%CrI: 0.53-0.75) presented similar benefits in term of OS. Enzalutamide showed superiority over PFS and PSA response with a highest probability to rank 1. Moreover, sensitivity analysis showed that Abiraterone Acetate (HR: 0.71, 95%CrI: 0.63-0.78) exhibited the most efficacious intervention of being rank 1 in term of OS compared with control arms, followed by Cabazitaxel and Cetuximab. On the other hand, Abiraterone Acetate (OR: 0.86, 95%CrI: 0.35-2.03) presented no significant toxicities compared with control arms.

Conclusions: Our results demonstrated that Abiraterone Acetate might be the optimal intervention for CRPC patients after docetaxel failure with acceptable tolerability. Future well-designed RCTs and systematic reviews are needed to validate these findings.

Simultaneous delivery of Paclitaxel and Bcl-2 siRNA via pH-Sensitive liposomal nanocarrier for the synergistic treatment of melanoma

pH-sensitive drug carriers that are sensitive to the acidic (pH = ~6.5) microenvironments of tumor tissues have been primarily used as effective drug/gene/siRNA/microRNA carriers for releasing their payloads to tumor cells/tissues. Resistance to various drugs has become a big hurdle in systemic chemotherapy in cancer. Therefore delivery of chemotherapeutic agents and siRNA's targeting anti apoptotic genes possess advantages to overcome the efflux pump mediated and anti apoptosis-related drug resistance. Here, we report the development of nanocarrier system prepared from kojic acid backbone-based cationic amphiphile containing endosomal pH-sensitive imidazole ring. This pH-sensitive liposomal nanocarrier effectively delivers anti-cancer drug (Paclitaxel; PTX) and siRNA (Bcl-2), and significantly inhibits cell proliferation and reduces tumor growth. Tumor inhibition response attributes to the synergistic effect of PTX potency and MDR reversing ability of Bcl-2 siRNA in the tumor supporting that kojic acid based liposomal pH-sensitive nanocarrier as efficient vehicle for systemic co-delivery of drugs and siRNA.

Lipid-coated gold nanocomposites for enhanced cancer therapy

The aim of the work reported here was to develop lipid-coated multifunctional nanocomposites composed of drugs and nanoparticles for use in cancer therapy. We incorporated thermosensitive phospholipids onto the surface of anisotropic gold nanoparticles (AuNPs) to further enhance drug delivery, with possible additional applications for in vivo imaging and photothermal cancer therapy. Lipid-coated nanohybrids loaded with the drug docetaxel (DTX) were prepared by a thin-film formation, hydration, and sonication method. Nanoparticles and their composites were characterized using particle-size analysis, zeta potential measurements, transmission electron microscopy, UV-visible spectroscopy, and reverse-phase high-performance liquid chromatography, demonstrating successful loading of DTX into the lipid bilayer on the surface of the gold nanoparticles. Initial in vitro studies using breast-cancer (MCF-7) and melanoma (B16F10) cell lines demonstrated that the drug-containing nanocomposites at equivalent drug concentrations caused significant cytotoxicity compared to free DTX. Differential flow cytometry analysis confirmed the improved cellular uptake of lipid-coated nanocomposites. Our preliminary results show that DTX-loaded anionic lipid-coated gold nanorod (AL_AuNR_DTX) and cationic lipid-coated gold nanoparticle (CL_AuNP_DTX) possess effective tumor cell-suppression abilities and can therefore be considered promising chemotherapeutic agents. Further evaluation of the therapeutic efficacy of these hybrid nanoparticles combined with external near-infrared photothermal treatment is warranted to assess their synergistic anticancer actions and potential bioimaging applications.

An examination of prostate cancer trends in Australia, England, Canada and USA: Is the Australian death rate too high?

PURPOSE

To compare prostate cancer incidence and mortality rates in Australia, USA, Canada and England and quantify the gap between observed prostate cancer deaths in Australia and expected deaths, using US mortality rates.

METHODS

Analysis of age-standardised prostate cancer incidence and mortality rates, using routinely available data, in four similarly developed countries and joinpoint regression to quantify the changing rates (annual percentage change: APC) and test statistical significance. Expected prostate cancer deaths, using US mortality rates, were calculated and compared with observed deaths in Australia (1994-2010).

RESULTS

In all four countries, incidence rates initially peaked between 1992 and 1994, but a second, higher peak occurred in Australia in 2009 (188.9/100,000), rising at a rate of 5.8 % (1998-2008). Mortality rates in the USA (APC: -2.9 %; 2004-2010), Canada (APC: -2.9 %; 2006-2011) and England (APC: -2.6 %; 2003-2008) decreased at a faster rate compared with Australia (APC: -1.7 %; 1997-2011). In 2010, mortality rates were highest in England and Australia (23.8/100,000 in both countries). The mortality gap between Australia and USA grew from 1994 to 2010, with a total of 10,895 excess prostate cancer deaths in Australia compared with US rates over 17 preceding years.

CONCLUSIONS

Prostate cancer incidence rates are likely heavily influenced by prostate-specific antigen testing, but the fall in mortality occurred too soon to be solely a result of testing. Greater emphasis should be placed on addressing system-wide differences in the management of prostate cancer to reduce the number of men dying from this disease.

Inhibition of PARP1 by small interfering RNA enhances docetaxel activity against human prostate cancer PC3 cells

Though poly(ADP-ribose) polymerase 1 (PARP1) inhibitors have benefits in combination with radiotherapy in prostate cancers, few is known about the exactly role and underlying mechanism of PARP1 in combination with chemotherapy agents. Here our data revealed that inhibition of PARP1 by small interfering RNA (siRNA) could enhance docetaxel's activity against PC3 cells, which is associated with an accelerate repression of EGF/Akt/FOXO1 signaling pathway. Our results provide a novel role of PARP1 in transcription regulation of EGFR/Akt/FOXO1 signaling pathway and indicate that PARP1 siRNA combined with docetaxel can be an innovative treatment strategy to potentially improve outcomes in CRPC patients.

Systematic review and meta-analysis of COX-2 expression and polymorphisms in prostate cancer

Evidence is accumulating that cyclooxygenase-2 (COX-2) may play an important role in prostate cancer (PCa). Recently, gene polymorphisms in COX-2 have been implicated to alter the risk of PCa and overexpression of COX-2 may be associated with clinical and prognostic significance in PCa. However, the results of these studies are inconclusive or controversial. To derive a more precise estimation of the relationships, we performed an updated meta-analysis. A comprehensive search was conducted to examine all the eligible studies of COX-2 polymorphism and expression in PCa. We used odds ratios (ORs) to assess the strength of the association and the 95 % confidence intervals (CIs) give a sense of the precision of the estimate. Overall, no significant associations between COX-2 polymorphism and PCa risk were found. However, high expression of COX-2 was significantly higher in T3-T4 stages of PCa than in T1-T2 stages of PCa (OR = 2.33, 95 %CI: 1.54-3.53, P < 0.0001). COX-2 might play an important role in the progress of PCa, overexpression of COX-2 correlates with T3-T4 stages of PCa. COX-2 might be a potential therapy target for PCa and work as a prognostic factor for PCa patients.

Enhanced docetaxel-mediated cytotoxicity in human prostate cancer cells through knockdown of cofilin-1 by carbon nanohorn delivered siRNA

We synthesized a non-viral delivery system (f-CNH3) for small interfering RNA (siRNA) by anchoring a fourth-generation polyamidoamine dendrimer (G4-PAMAM) to carbon nanohorns (CNHs). Using this new compound, we delivered a specific siRNA designed to knockdown cofilin-1, a key protein in the regulation of cellular cytoskeleton, to human prostate cancer (PCa) cells. The carbon nanohorn (CNH) derivative was able to bind siRNA and release it in the presence of an excess of the polyanion heparin. Moreover, this hybrid nanomaterial protected the siRNA from RNAse-mediated degradation. Synthetic siRNA delivered to PCa cells by f-CNH3 decreased the cofilin-1 mRNA and protein levels to about 20% of control values. Docetaxel, the drug of choice for the treatment of PCa, produced a concentration-dependent activation of caspase-3, an increase in cell death assessed by lactate dehydrogenase release to the culture medium, cell cycle arrest and inhibition of tumor cell proliferation. All of these toxic effects were potentiated when cofilin-1 was down regulated in these cells by a siRNA delivered by the nanoparticle. This suggests that knocking down certain proteins involved in cancer cell survival and/or proliferation may potentiate the cytotoxic actions of anticancer drugs and it might be a new therapeutic approach to treat tumors.

Chemotherapy of Prostate Cancer by Targeted Nanoparticles Trackable by Magnetic Resonance Imaging

Prostate cancer (CaP) is the commonest diagnosed malignancy and the second main cause of cancer mortality in males in the United States. Thus, there is an urgent need to develop novel drug delivery systems to improve the chemotherapy option for CaP patients. The goal of this paper is to describe novel moleculary guided nanoscale drug delivery system with dual functionality for treatment and MR imaging of CaP. We describe the synthesis of iron oxide nanoparticles (IONPs) which are then coated with carboxyl-ended amphiphilic polymer. We present the protocol for tethering of the CaP targeting protein, human amino terminal fragment (hATF) to the terminal carboxyls of the IONPs. We describe the drug loading and release and the methods for measuring of the internalization of the hATF-guided IONPs into CaP cells. We also describe the methods for usages of IONPs are MR imaging contrast agent and successful targeted drug carriers.

Weekly low-dose docetaxel combined with estramustine and dexamethasone for Japanese patients with metastatic castration-resistant prostate cancer

BACKGROUND

A low-dose chemotherapy consisting of docetaxel, estramustine and dexamethasone was investigated for its beneficial effect and feasibility in Japanese patients with metastatic castration-resistant prostate cancer (CRPC).

METHODS

Seventy-two Japanese patients with metastatic CRPC were enrolled to receive docetaxel (25 mg/m(2) on days 2 and 9), estramustine phosphate (280 mg orally twice daily from day 1 to day 3 and from day 8 to day 10) and dexamethasone (0.5 mg orally twice daily) every 21 days.

RESULTS

The median age of the patients was 72 years and 64 patients (89 %) had ≥grade 1 anemia at entry. The median total number of courses administered was 8.5 (range 1-93). Forty-two patients (58 %) had a prostate-specific antigen (PSA) decline of ≥50 %. The median progression-free survival and overall survival were 6 and 23 months, respectively. Fifteen patients (21 %) improved and 53 patients (74 %) were stable in their performance status. Of the 40 patients with bone pain, 25 patients (63 %) showed pain reduction. Among 71 patients assessable for their hemoglobin levels, 21 patients (30 %) achieved an increase of at least 1.0 g/dl. Of the 5 patients who terminated treatment because of ≥grade 3 toxicity, 4 patients had pneumonitis and one patient had anemia. Only one patient developed ≥grade 3 neutropenia.

CONCLUSIONS

The low-dose combination of docetaxel, estramustine and dexamethasone is active and tolerable with beneficial effects on serum PSA levels, performance status, anemia and bone pain in Japanese patients with CRPC. This regimen is a reasonable option for elderly patients with bone disease at risk of hematologic toxicity.

Lenalidomide enhances the anti-prostate cancer activity of docetaxel in vitro and in vivo

BACKGROUND

In this study, we investigated the effects of combining lenalidomide and docetaxel on in vitro and in vivo models of prostate cancer as a potential strategy for treatment of castrate resistant prostate cancer (CRPC).

METHODS

The effects of combining lenalidomide and docetaxel on proliferation, apoptosis, invasive potential, anchorage independent growth, and p53 activation in the PC3 and DU145 prostate cell lines were investigated. The effects of the lenalidomide and docetaxel combination on LNCaP prostate cancer cell growth and invasiveness in vitro was also studied. The combination of these two agents was finally tested on a xenograft model of PC3 tumor growth in nude mice.

RESULTS

Lenalidomide decreased the IC(50) of docetaxel by up to 50% (P < 0.05) and also decreased invasion in PC3, LNCaP, and DU145 cells and anchorage independent growth in PC3 cells (P < 0.01). Apoptosis in lenalidomide/docetaxel-treated cells was increased by 2.2-fold over single agent docetaxel and a corresponding increase in p53, p38, and BAD activation was observed in Western blots (P < 0.001). When PC3 challenged mice were treated with lenalidomide and docetaxel, median survival increased from 48 to 59 days and the rate of tumor growth was significantly reduced (P < 0.05).

CONCLUSIONS

Lenalidomide may be a promising candidate for combination with docetaxel in the treatment of CRPC.

Prolonged treatment with three-weekly docetaxel plus daily prednisolone for metastatic castration-resistant prostate cancer: a multicenter, phase II, open-label, non-comparative, extension study in Japan

BACKGROUND

There are few reports of long-term treatment with docetaxel in castration-resistant prostate cancer (CRPC) because of the limit of a maximum of ten cycles of treatment in TAX327 showing a survival benefit. Therefore, this study, ARD6563, was conducted to evaluate the safety of more than ten cycles of docetaxel in metastatic CRPC.

METHODS

We enrolled patients who had received ten cycles of docetaxel in the preceding study, ARD6562. For ARD6563, patients received docetaxel every 3 weeks, at the last dose (70, 60, or 50 mg/m(2)) received for cycle 10 in ARD6562, with prednisolone 5 mg orally twice daily.

RESULTS

The safety analysis set comprised 15 patients (median age, 64 years; performance status, 0 in 87%) out of 43 patients treated in ARD6562. The median initial dose of docetaxel was 60 mg/m(2), and the median number of additional cycles administered was 8 (range, 1-42). The relative dose intensity was 78.0% for docetaxel and 98.0% for prednisolone. Dose reduction was needed in 3 cycles because of grade 3 infection, febrile neutropenia, and grade 2 neuropathy. Administration delay was necessitated in 6 cycles because of grade 1-2 nonhematological toxicities. The major grade 3-4 toxicities were myelosuppression. Five patients who had an observed partial response or stable disease in ARD6562 maintained their clinical response in ARD6563. The study treatment was discontinued in 10 patients because of disease progression and in 4 patients for serious toxicities. There were no treatment-related deaths.

CONCLUSIONS

Long-term docetaxel with prednisolone is feasible in selected Japanese patients with CRPC.

Landscape phage fusion protein-mediated targeting of nanomedicines enhances their prostate tumor cell association and cytotoxic efficiency

Tumor-specific cytotoxicity of drugs can be enhanced by targeting them to tumor receptors using tumor-specific ligands. Phage display offers a high-throughput approach to screen for the targeting ligands. We have successfully isolated phage fusion peptides selective and specific for PC3 prostate cancer cells. Also, we have demonstrated a novel approach of targeting liposomes through tumor-specific phage fusion coat proteins, exploiting the intrinsic properties of the phage coat protein as an integral membrane protein. Here we describe the production of Rhodamine-labeled liposomes as well as doxorubicin-loaded long-circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides, as an extension of our previous studies. Targeting of labeled liposomes was demonstrated using fluorescence microscopy as well as flow cytometry. Targeting of doxorubicin-loaded liposomes enhanced their cytotoxic effect against PC3 cells in vitro, indicating a possible therapeutic advantage. The simplicity of the approach for generating targeted liposomes coupled with the ability to rapidly obtain tumor-specific phage fusion proteins via phage display may contribute to a combinatorial system for the production of targeted liposomal therapeutics for advanced stages of prostate tumor. From the clinical editor: This paper demonstrates targeting cytotoxic agents to tumor receptors using tumor-specific ligands. The authors describe the production of Rhodamine-labeled liposomes as well as doxorubicin loaded long circulating liposomes targeted to PC3 prostate tumor cells via PC-specific phage peptides. This approach may be especially relevant for advanced prostate tumors.

New potential anti-cancer agents synergize with bortezomib and ABT-737 against prostate cancer

BACKGROUND

We previously described the identification of a transcriptional inhibitor ARC and FoxM1 inhibitors, thiazole antibiotics, Siomycin A and thiostrepton that were able to induce potent p53-independent apoptosis in cancer cell lines of different origin. Here, we report the characterization of these drugs individually or in combination with ABT-737 and bortezomib on a panel of prostate cancer cell lines.

METHODS

DU 145, LNCaP and PC-3 prostate cancer cells were treated with ARC, Siomycin A and thiostrepton to evaluate their activity as single agents or in combination with ABT-737 and bortezomib to measure their synergistic potential in anti-proliferative and cell cycle assays. Chou-Talalay method was used to quantitate the synergistic interaction. Western blot method was used to determine Mcl-1 and FoxM1 expression and caspase-3 cleavage.

RESULTS

We show that ARC inhibited the viability of prostate cancer cells and induced apoptosis in low nanomolar concentration. It potently downregulated the expression of Mcl-1 and showed synergistic combination effect with Bcl-2 inhibitor ABT-737. Thiazole antibiotics, Siomycin A and thiostrepton inhibited growth, FoxM1 expression and induced cell death in prostate cancer cells in low micromolar concentrations. In addition, thiostrepton and ARC synergistically induced apoptosis in prostate cancer cells following combination treatment with proteasome inhibitor bortezomib. Furthermore, we found that all tested drug combinations were able to induce apoptosis selectively in transformed, but not normal cells of the same origin.

CONCLUSIONS

Based on their in vitro activity as single or combination agents, ARC, Siomycin A and thiostrepton represent potential candidates for drug development against prostate cancer.

Chimeric adenoviral vectors incorporating a fiber of human adenovirus 3 efficiently mediate gene transfer into prostate cancer cells

BACKGROUND

We have developed a range of adenoviral (Ad) vectors based on human adenovirus serotype 5 (HAdV-5) displaying the fiber shaft and knob domains of species B viruses (HAdV-3, -11, or -35). These species B Ads utilize different cellular receptors than HAdV-5 for infection. We evaluated whether Ad vectors displaying species B fiber shaft and knob domains (Ad5F3Luc1, Ad5F11Luc1, and Ad5F35Luc1) would efficiently infect cancer cells of distinct origins, including prostate cancer.

METHODS

The fiber chimeric Ad vectors were genetically generated and compared with the original Ad vector (Ad5Luc1) for transductional efficiency in a variety of cancer cell lines, including prostate cancer cells and primary prostate epithelial cells (PrEC), using luciferase as a reporter gene.

RESULTS

Prostate cancer cell lines infected with Ad5F3Luc1 expressed higher levels of luciferase than Ad5Luc1, as well as the other chimeric Ad vectors. We also analyzed the transductional efficiency via monitoring of luciferase activity in prostate cancer cells when expressed as a fraction of the gene transfer in PrEC cells. In the PC-3 and DU145 cell lines, the gene transfer ratio of cancer cells versus PrEC was once again highest for Ad5F3Luc1.

CONCLUSION

Of the investigated chimeric HAdV-5/species B vectors, Ad5F3Luc1 was judged to be the most suitable for targeting prostate cancer cells as it showed the highest transductional efficiency in these cells. It is foreseeable that an Ad vector incorporating the HAdV-3 fiber could potentially be used for prostate cancer gene therapy.

Molecular and traditional chemotherapy: a united front against prostate cancer

Castrate resistant prostate cancer (CRPC) is essentially incurable. Recently though, chemotherapy demonstrated a survival benefit ( approximately 2months) in the treatment of CRPC. While this was a landmark finding, suboptimal efficacy and systemic toxicities at the therapeutic doses warranted further development. Smart combination therapies, acting through multiple mechanisms to target the heterogeneous cell populations of PC and with potential for reduction in individual dosing, need to be developed. In that, targeted molecular chemotherapy has generated significant interest with the potential for localized treatment to generate systemic efficacy. This can be further enhanced through the use of oncolytic conditionally replicative adenoviruses (CRAds) to deliver molecular chemotherapy. The prospects of chemotherapy and molecular-chemotherapy as single and as components of combination therapies are discussed.

[Chemotherapy of hormonorefractory and hormonoresistant metastatic prostate cancer]

Since 2004 and the first improvement in overall survival in hormone refractory prostate cancer patients (HRPC) brought about by docetaxel, numerous phase II and III studies have been initiated. Considering the lack of efficacy in terms of overall survival, hormonal manipulations such as antiandrogen withdrawal, di-ethylstilbesterol or dexamethason are only indicated in "rising PSA" patients without clinical or radiological evidence of metastases. As first line treatment, the optimal chemotherapy regimen is docetaxel (75 mg/m(2) every 3 weeks) in association with prednisone (5 mg twice daily). Second line chemotherapies (mitoxantron, ixabepilon, docetaxel as a re-treatment, vinorelbin, doxorubicin...) provide modest results only in terms of progression-free survival. A phase III study of Straplatin has been prematurely interrupted. Targeted anti-angiogenic therapies have shown encouraging results in patients with metastatic localizations, and underline the need to identify target patients early through cellular markers (mTOR or EGFR overexpression) as well as the uselessness of PSA dosage to monitor efficacy. An ongoing phase III study is evaluating bevacizumab in association with docetaxel to improve overall survival. Both the Provenge vaccine and DN 101 (calcitriol) showed a survival gain of a few months in phase III studies. An ongoing EORTC phase II trial is evaluating antisense oligonucleotids in HRPC. Early introduction of docetaxel raises the issue of when to start chemotherapy as it may be relevant to initiate this treatment before the onset of hormone independence. GETUG 15 trial will try to answer this question.

Gamma-tocotrienol suppresses prostate cancer cell proliferation and invasion through multiple-signalling pathways

Tocotrienol-rich fraction (TRF) has demonstrated antiproliferative effect on prostate cancer (PCa) cells. To elucidate this anticancer property in PCa cells, this study aimed, first, to identify the most potent isomer for eliminating PCa cells; and second, to decipher the molecular pathway responsible for its activity. Results showed that the inhibitory effect of γ-tocotrienol was most potent, which resulted in induction of apoptosis as evidenced by activation of pro-caspases and the presence of sub-G₁ cell population. Examination of the pro-survival genes revealed that the γ-tocotrienol-induced cell death was associated with suppression of NF-κB, EGF-R and Id family proteins (Id1 and Id3). Meanwhile, γ-tocotrienol treatment also resulted in the induction of JNK-signalling pathway and inhibition of JNK activity by a specific inhibitor (SP600125) was able to partially block the effect of γ-tocotrienol. Interestingly, γ-tocotrienol treatment led to suppression of mesenchymal markers and the restoration of E-cadherin and γ-catenin expression, which was associated with suppression of cell invasion capability. Furthermore, a synergistic effect was observed when cells were co-treated with γ-tocotrienol and Docetaxel. Our results suggested that the antiproliferative effect of γ-tocotrienol act through multiple-signalling pathways, and demonstrated for the first time the anti-invasion and chemosensitisation effect of γ-tocotrienol against PCa cells.

Pretreatment of docetaxel enhances TRAIL-mediated apoptosis in prostate cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic agent because of its tumor selectivity. TRAIL is known to induce apoptosis in cancer cells but spare most normal cells. In this study, we examined whether treatment of docetaxel (DTX) can enhance apoptotic cell death by TRAIL against androgen-independent prostate cancer (AIPC). The cell death effect of combinations of TRAIL and docetaxel on prostate cancer cell lines (androgen-dependent LNCaP and its derived androgen-independent, metastatic C4-2B) was evaluated by synergisms of apoptosis. Western blot assay and DNA fragmentation assay were used to study the underlying mechanisms of cell death and search for any mechanisms of enhancement of TRAIL induced apoptosis in the presence of docetaxel. In addition, we investigated the in vitro anti-tumor effects of combined docetaxel and TRAIL using MAP kinase inhibitors. Docetaxel itself could not induce apoptotic cell death in 24 h even in high concentration. Apoptotic cell death, however, was drastically enhanced by pretreatment of docetaxel 20 h before TRAIL treatment. Docetaxel enhanced the PARP-1 cleavage and caspases activation by TRAIL especially in androgen-independent, metastatic C4-2B cell line, mainly by phosphorylation of Bcl-2 by JNK activation. It appears that apoptotic cell death was protected by the JNK inhibitor SP600125. The results of our study show that pretreatment of docetaxel is able to enhance the apoptosis produced by TRAIL in prostate cancer cells, especially in hormone-refractory prostate cancer (HRPC).