Systemic treatment for prostate cancer

Cabazitaxel versus docetaxel for treatment of metastatic castrate refractory prostate cancer

Objectives

To assess cabazitaxel versus docetaxel re-challenge for the treatment of metastatic castrate refractory prostate cancer (CRPC) patients previously treated with docetaxel at inception of primary hormone therapy.

Patients and Methods

The CANTATA trial was a prospective, two-arm, open-label, phase II study conducted in eight UK centres. Patients over the age of 18, with histologically proven, metastatic prostate cancer who had been previously treated with up to 6 cycles of docetaxel as part of the STAMPEDE trial (or treated with the same drug outside of the trial at primary diagnosis) and had a performance status (PS) of 0-2, were eligible. Patients who progressed during primary treatment with docetaxel or had received prior systemic chemotherapy were excluded. Cabazitaxel (25 mg/m2) or docetaxel (75 mg/m2) was administered via intravenous infusion every 3 weeks with oral prednisolone (10 mg) for up to 10 cycles, until disease progression, death or unacceptable toxicity. The primary outcome was clinical progression-free survival (PFS) as defined by either date of pain progression, date of a cancer-related skeletal-related event, or date of death from any cause. Analyses were by intention to treat. EudraCT number: 2012-003835-40.

Results

Between 7 March 2013 and 4 January 2016, 15 patients with a median age of 70 years (range 54-76) were recruited; seven received cabazitaxel, eight docetaxel. The study was halted due to slow accrual. The median clinical PFS time in the cabazitaxel group was 6.2 months compared with 8.4 for the docetaxel group (95% confidence intervals were not reached due to the small number of patients). A total of 13 serious adverse events were reported.

Conclusion

Due to the low number of patients recruited, meaningful comparisons could not be made. However, toxicity was in line with known outcomes for these agents, demonstrating it is feasible and safe to deliver chemotherapy to men relapsing with CRPC after upfront chemotherapy.

Expression of heat shock protein 27 in prostate cancer cell lines according to the extent of malignancy and doxazosin treatment

Purpose

Heat shock protein 27 (HSP27) is known as the material that plays a role in apoptosis control in tumor and cell protection including the immune response, drug tolerance, and so on. In this study, HSP27 expression according to the prostate cancer malignancy level was evaluated, and HSP27 expression was also analyzed after inducing apoptosis by doxazosin treatment of the prostate cancer cell lines.

Materials and Methods

Reverse transcription polymerase chain reaction (RT-PCR) and immunofluorescence staining of the HSP27 was implemented by the culture of RWPE-1, LNCaP, androgen-independent human prostate cancer cells (PC-3), and TSU-Pr1 cell lines. Analysis was separately conducted in the control group, control vector group treated by dimethyl sulfoxide, and groups treated with 10 µM or 25 µM doxazosin. The expression of HSP27 in RT-PCR and immunofluorescence staining was observed and evaluated after conversion to numerical values.

Results

In the RT-PCR results, depending on the cell type, LNCaP, TSU-Pr1 showed the highest HSP27 expression followed by PC-3, LNCaP and RWPE-1 in sequence. After doxazosin treatment, the expression detected by RT-PCR was stronger at a 25-µM doxazosin concentration compared to that at a 10-µM concentration, and the result was similar by immunofluorescence staining.

Conclusions

HSP27 expression increased depending on the prostate cancer cell line. This meant that HSP27 expression was related to the prostate cancer malignancy level. Additionally, the higher the treatment concentration in PC-3 was, the higher the HSP27 expression was. This result showed that doxazosin induced apoptosis of prostate cancer.

Diethylstilboestrol for the treatment of prostate cancer: past, present and future

The aim of this review was to discuss the most recent data from current trials of diethylstilboestrol (DES) to identify its present role in advanced prostate cancer treatment as new hormonal therapies emerge. The most relevant clinical studies using DES in castration-refractory prostate cancer (CRPC) were identified from the literature. The safety, efficacy, outcomes and mechanisms of action are summarized. In the age of chemotherapy this review highlights the efficacy of oestrogen therapy in CRPC. The optimal point in the therapeutic pathway at which DES should be prescribed remains to be established.

A novel histone deacetylase (HDAC) inhibitor MHY219 induces apoptosis via up-regulation of androgen receptor expression in human prostate cancer cells

Histone deacetylase (HDAC) inhibitors are a new class of anticancer agents that act by inhibiting cancer cell proliferation and inducing apoptosis in various cancer cell lines. To investigate the anticancer effect of a novel histone deacetylase (HDAC) inhibitor MHY219, its efficacy was compared to that of suberoylanilide hydroxamic acid (SAHA) in human prostate cancer cells. The anticancer effects of MHY219 on cell viability, HDAC enzyme activity, cell cycle regulation, apoptosis and other biological assays were performed. MHY219 was shown to enhance the cytotoxicity on DU145 cells (IC₅₀, 0.36 μM) when compared with LNCaP (IC₅₀, 0.97 μM) and PC3 cells (IC₅₀, 5.12 μM). MHY219 showed a potent inhibition of total HDAC activity when compared with SAHA. MHY219 increased histone H3 hyperacetylation and reduced the expression of class I HDACs (1, 2 and 3) in prostate cancer cells. MHY219 effectively increased the sub-G1 fraction of cells through p21 and p27 dependent pathways in DU145 cells. MHY219 significantly induced a G2/M phase arrest in DU145 and PC3 cells and arrested the cell cycle at G0/G1 phase in LNCaP cells. Furthermore, MHY219 effectively increased apoptosis in DU145 and LNCaP cells, but not PC3 cells, according to Annexin V/PI staining and Western blot analysis. These results indicate that MHY219 is a potent HDAC inhibitor that targets regulating multiple aspects of cancer cell death and might have preclinical value in human prostate cancer chemotherapy, warranting further investigation.

Differential effects of estrogen receptor ligands on regulation of dihydrotestosterone-induced cell proliferation in endothelial and prostate cancer cells

Androgen deprivation therapy of prostate cancer with estrogens shows significant cardiovascular side-effects. To develop effective prostate cancer therapeutic agent(s) with minimal cardiovascular side-effects, we compared the effects of various estrogen receptor (ER) ligands on the modulation of dihydrotestosterone (DHT) actions in LAPC-4 and LNCaP prostate cancer cells and human aortic endothelial cells (HAECs). DHT stimulated the proliferation of HAEC, LAPC-4 and LNCaP cells and induced PSA mRNA expression in LAPC-4 cells. These DHT actions were differentially modulated by ER ligands in a cell-dependent manner. In LAPC-4 cells, knockdown of ERβ expression partially eliminated the βE2 inhibition of DHT-induced LAPC-4 cell proliferation, and a parallel change was observed between ER ligand modulation of DHT-induced cell proliferation and cyclin A expression. The obtained data suggest that it is feasible to develop effective agent(s) for prostate cancer therapy with minimal cardiovascular side-effects and 17α-estradiol and genistein are such potential agents.

TP53INP1 as new therapeutic target in castration-resistant prostate cancer

BACKGROUND

Prostate cancer (PC) is one of the most common malignancies in industrialized countries, and the second leading cause of cancer-related death in the United States. We recently showed that over-expression of tumor protein 53-induced nuclear protein 1 (TP53INP1), a cell stress response protein, is a worse prognostic factor in PC, particularly predictive of biological cancer relapse. Moreover, treatment of castration-sensitive (CS) LNCaP tumor cells with a TP53INP1 antisense oligonucleotide (TP53INP1 ASO) inhibits proliferation and induces apoptosis. The aim of this study was to investigate variations of TP53INP1 expression in PC during androgen withdrawal therapy and in castration-resistant prostate cancer (CRPC).

METHODS

Quantitative measurements of immunohistochemical expression of TP53INP1 using high-throughput densitometry, assessed on digitized microscopic tissue micro-array images were correlated with hormone therapy (HT) status in human PC. Northern blot analysis of TP53INP1 after castration was performed in LNCaP xenograft. Treatment of CR C4-2 tumor cells in vitro with TP53INP1 ASO was analyzed. We also analyzed the effect of TP53INP1 ASO treatment in vivo on tumor xenograft growth.

RESULTS

TP53INP1 protein expression decreases during HT and increases after HT in human CRPC. TP53INP1 mRNA increases significantly in CR tumors of LNCaP xenograft. Moreover, treatment of CR C4-2 cells with TP53INP1 ASO downregulates TP53INP1 protein level, inhibits proliferation, and induces apoptosis. Finally, in vivo, TP53INP1 ASO treatment significantly inhibits the tumoral progression of CR C4-2 xenograft and enhances docetaxel cytotoxicity.

CONCLUSIONS

These results suggest that TP53INP1 could be considered as a relevant-specific target for molecular therapy of CRPC.

NSC606985, a novel camptothecin analog, induces apoptosis and growth arrest in prostate tumor cells

PURPOSE

Prostate cancer is a major cause of cancer mortality in American males. Once prostate cancer has metastasized, there is currently no curative therapy available. The development of effective agents is therefore a continuing effort to combat this disease. In the present study, the effects and potential mechanisms of NSC606985 (NSC), a water-soluble camptothecin analog, in prostate cancer cells were investigated.

METHODS

Prostatic tumor cells, DU-145, LNCaP and PC-3, were used for the study. Cell proliferation, cell cycle, cell apoptosis and caspase 3/7 activity were determined in the presence or absence of NSC. The levels of Bax and Bak, and the release of cytochrome c from mitochondria were analyzed by Western blot.

RESULTS

Treatment with NSC at nanomolar concentrations produced a time- and dose-dependent decrease in viable cell numbers of multiple prostate cancer cells. In DU-145 cells, NSC produced a time-and dose-dependent induction of cell apoptosis and cell cycle arrest as evidenced by cell morphological changes, increases in S-phase and sub-G1 cell fractions, an elevation of caspase 3/7 activity, DNA fragmentation and apoptotic cells. NSC increased the levels of apoptotic proteins, Bax and Bak, and induced a release of cytochrome c from mitochondria to cytosol in DU-145 cells. Co-administration of Z-VAD-FMK, a pan-caspase inhibitor, blocked NSC-induced caspase 3/7 activity and cell apoptosis without affecting NSC-induced cell cycle arrest. In contrast, co-administration of a PKCdelta inhibitor, rottlerin, had no significant effect on NSC induction of caspase activity, and slightly potentiated NSC-induced cell death. Furthermore, like camptothecin, a mutation of topoisomerase 1 that prevents the binding of camptothecin to the enzyme completely abolished the NSC effect in DU-145 cells.

CONCLUSION

The data obtained suggest that NSC is able to decrease cell growth, induce cell apoptosis and cause growth arrest in prostatic tumor cells, which may involve an interaction with topoisomerase 1 and an activation of mitochondrial apoptotic pathway.

Configurations of a two-tiered amplified gene expression system in adenoviral vectors designed to improve the specificity of in vivo prostate cancer imaging

Effective treatment for recurrent, disseminated prostate cancer is notably limited. We have developed adenoviral vectors with a prostate-specific two-step transcriptional amplification (TSTA) system that would express therapeutic genes at a robust level to target metastatic disease. The TSTA system employs the prostate-specific antigen (PSA) promoter/enhancer to drive a potent synthetic activator, which in turn activates the expression of the therapeutic gene. In this study, we explored different configurations of this bipartite system and discovered that physical separation of the two TSTA components into E1 and E3 regions of adenovirus was able to enhance androgen regulation and cell-discriminatory expression. The TSTA vectors that express imaging reporter genes were assessed by noninvasive imaging technologies in animal models. The improved selectivity of the E1E3 configured vector was reflected in silenced ectopic expression in the lung. Significantly, the enhanced specificity of the E1E3 vector enabled the detection of lung metastasis of prostate cancer. An E1E3 TSTA vector that expresses the herpes simplex virus thymidine kinase gene can effectively direct positron emission tomography (PET) imaging of the tumor. The prostate-targeted gene delivery vectors with robust and cell-specific expression capability will advance the development of safe and effective imaging guided therapy for recurrent metastatic stages of prostate cancer.

17alpha-estradiol inhibits LAPC-4 prostatic tumor cell proliferation in cell cultures and tumor growth in xenograft animals

BACKGROUND

Blockade of androgen activity is a major effective therapy for advanced prostate cancer. Estrogen analogs have been used for prostate cancer therapy for years presumably by inhibiting testosterone biosyntheses, but with considerable adverse events due to their classic estrogenic activity. With the discovery of the estrogen receptor (ER) beta and its presence in prostate tumor cells, evaluation of estrogen analogs with less classic estrogenic activity in prostate cancer therapy is emerging.

METHODS

The effects of 17alpha-estradiol (alphaE2), a stereo-isomer of 17beta-estradiol (betaE2), on dihydrotestosterone (DHT)-induced cell growth and gene expressions were examined in androgen-dependent LAPC-4 prostatic tumor cells and in LAPC-4 xenograft animals, and compared to those of betaE2.

RESULTS

Both alphaE2 and betaE2 attenuated DHT induction of PSA gene expression, cell proliferation, and cell growth in cultured LAPC-4 cells. The inhibition of cell proliferation was associated with a blockade of DHT-induced cyclin A and cyclin D1 expression by alphaE2 and betaE2. In LAPC-4 xenograft mice, alphaE2 significantly inhibited tumor growth without altering the plasma testosterone level, while betaE2 failed to inhibit tumor growth even though it significantly inhibited PSA gene expression.

CONCLUSION

alphaE2 is an effective agent for inhibition of DHT-induced PSA, cyclin A, cyclin D1 gene expression, and cell proliferation in LAPC-4 cells, and tumor growth in LAPC-4 xenograft mice.

Preventive and therapeutic vaccination with PAP-3, a novel human prostate cancer peptide, inhibits carcinoma development in HLA transgenic mice

Conventional treatment of recurrent and metastasized prostate cancer (CaP) remains inadequate; this fact mandates development of alternative therapeutic modalities, such as specific active or passive immunotherapy. Previously, we reported the identification of a novel highly immunogenic HLA-A*0201-restricted Prostatic Acid Phosphatase-derived peptide (PAP-3) by a two-step in vivo screening in an HLA-transgenic (HHD) mouse system. In the present study we aimed at elucidating the efficiency of PAP-3-based vaccine upon active antitumor immunization. To this end we established preventive and therapeutic carcinoma models in HHD mice. The 3LL murine Lewis lung carcinoma clone D122 transduced to express HLA-A*0201 and PAP served as a platform for these models. The HLA-A*0201-PAP-3 complex specific recombinant single chain scFV-PAP-3 antibodies were generated and used to confirm an endogenous PAP processing resulting in PAP-3 presentation by HLA-A*0201. PAP-3 based vaccines significantly decreased tumor incidence in a preventive immunization setting. Therapeutic vaccination of HHD mice with PAP-3 led to rejection of early established tumors and to increase of mouse survival. These results strongly support a therapeutic relevance of the identified CTL epitope upon active antitumor immunization. The newly established carcinoma model presented herein might be a useful tool for cancer vaccine design and optimization.

Small interference RNA targeting heat-shock protein 27 inhibits the growth of prostatic cell lines and induces apoptosis via caspase-3 activation in vitro

OBJECTIVES

To evaluate synthetic small interference RNA (siRNA) compounds targeting heat-shock protein 27 (Hsp27) as an alternative approach to Hsp27 'knockdown' in prostate cancer cells, as Hsp27 expression is highly up-regulated in prostate cancer cells after androgen withdrawal or chemotherapy, to become uniformly highly expressed in androgen-independent (AI) prostate cancer.

MATERIALS AND METHODS

We recently showed that targeting Hsp27 by a 2'-methoxyethyl modified phosphorothioate antisense oligonucleotide, OGX-427, inhibits Hsp27 expression and enhances hormone- and chemotherapy in prostate cancer xenograft models. In the present study, a 'gene walk' screening different siRNAs was initially used in PC-3 and LNCaP cells to determine the most potent sequence to down-regulate Hsp27 mRNA and protein levels. The effects of Hsp27 silencing on in vitro growth rates were studied by tetrazolium-blue and crystal violet assays. Apoptosis was determined by single-stranded DNA nuclear and cleaved caspase-3 immunostaining, as well as flow cytometry. Spotted microarrays with 14,000 human oligonucleotides were used to examine changes in gene expression.

RESULTS

Low concentrations of 1 nm siRNA decreased Hsp27 mRNA levels by 19-fold and suppressed protein expression to undetectable levels. Silencing of Hsp27 in prostate cancer cells by siRNA # 2 increased apoptotic rates 2.4-4 fold and caused 40-76% inhibition of cell growth in LNCaP and PC-3 cells. Characteristic cleavage of caspase-3 occurred after treatment with Hsp27 siRNA (1 nm). cDNA microarray analysis from LNCaP and PC-3 cell lines revealed differential gene expression profiles after Hsp27 down-regulation that could be used to identify various survival pathways involved in androgen-dependent and AI growth.

CONCLUSIONS

These findings illustrate the potential utility of Hsp27-silencing therapy and highlight Hsp27 siRNA strategies as a novel and highly effective tool, with the potential for future targeted therapy in enhancing the efficacy of chemotherapy in advanced prostate cancer.

FTY720, a fungus metabolite, inhibits invasion ability of androgen-independent prostate cancer cells through inactivation of RhoA-GTPase

The failure of controlling androgen-independent and metastatic prostate cancer growth is the main cause of death in prostate cancer patients. In this study, we have demonstrated evidence on the inhibitory effects of a fungus metabolite, FTY720, on the clonogenesity as well as invasion ability of androgen-independent prostate cancer cells. First, using colony forming assay, we found that FTY720 treatment led to decreased colony forming ability of androgen-independent prostate cancer cell lines DU145 and PC3, indicating its negative role on cancer cell survival. In addition, treatment with relatively low dose of FTY720 (i.e. inhibitory concentration of 50% cell survival) resulted in suppression of prostate cancer cell migration and invasion abilities demonstrated by Wound closure, 3D collagen gel invasion assays and stress fiber staining. Furthermore, we found that the inhibitory effect of FTY720 on prostate cancer invasion was associated with down-regulation of GTP-bound active form of RhoA. Transfection of a dominant-active RhoA vector in DU145 and PC3 cells conferred resistance to FTY720. Since activation of RhoA-GTPase is associated with metastasis in many types of malignancies, our results not only suggest a new agent for the treatment of advanced prostate cancer, but also implicate a possible novel anticancer drug especially against metastatic cancers.

Functionality of androgen receptor-based gene expression imaging in hormone refractory prostate cancer

PURPOSE

A highly augmented, prostate-specific two-step transcriptional amplification (TSTA) method was developed with the ultimate goal of delivering an effective and safe gene-based treatment to prostate cancer patients. Because very limited treatment options are available for recurrent hormone refractory prostate cancer (HRPC), it is imperative to assess whether the prostate-specific antigen (PSA) promoter-based TSTA gene therapy will be functional in HRPC.

EXPERIMENTAL DESIGN

We tested the TSTA-driven adenovirus vector on three androgen-dependent and six HRPC models. Real-time gene expression was monitored by both optical imaging and the combined modality of positron emission tomography (PET) and computed tomography.

RESULTS

The TSTA-driven firefly luciferase expressing adenoviral vector was active in all androgen receptor (AR)-expressing HRPC models, but inactive in AR- and PSA-negative lines. Interestingly, the TSTA-mediated gene expression was induced by hydrocortisone in MDA PCa 2b, a cell line with mutated AR that possesses altered ligand specificity. In animal models, the TSTA-mediated optical signal was more robust in the HRPC than androgen-dependent tumors. In a parallel trend, a TSTA vector that expresses the herpes simplex virus thymidine kinase PET reporter gene also displayed more robust PET signal in the HRPC tumor.

CONCLUSIONS

The activity of TSTA system is AR dependent and it recapitulates the functional status of endogenous AR. These data support the conclusion that AR function is activated in HRPC despite castrated levels of androgen. Together with the fact that majority of recurrent prostate cancers express AR and PSA, we foresee that the TSTA approach can be a promising gene therapy strategy for the advanced stages of prostate cancer.

Up-regulation of TWIST in prostate cancer and its implication as a therapeutic target

Androgen-independent metastatic prostate cancer is the main obstacle in the treatment of this cancer. Unlike a majority of solid cancers, prostate cancer usually shows poor response to chemotherapeutic drugs. In this study, we have shown a potential novel target, TWIST, a highly conserved bHLH transcription factor, in the treatment of prostate cancer. Using malignant and nonmalignant prostate tissues, we found that TWIST expression was highly expressed in the majority (90%) of prostate cancer tissues but only in a small percentage (6.7%) of benign prostate hyperplasia. In addition, the TWIST expression levels were positively correlated with Gleason grading and metastasis, indicating its role in the development and progression of prostate cancer. Furthermore, down-regulation of TWIST through small interfering RNA in androgen-independent prostate cancer cell lines, DU145 and PC3, resulted in increased sensitivity to the anticancer drug taxol-induced cell death which was associated with decreased Bcl/Bax ratio, leading to activation of the apoptosis pathway. More importantly, inactivation of TWIST suppressed migration and invasion abilities of androgen-independent prostate cancer cells, which was correlated with induction of E-cadherin expression as well as morphologic and molecular changes associated with mesenchymal to epithelial transition. These results were further confirmed on the androgen-dependent LNCaP cells ectopically expressing the TWIST protein. Our results have identified TWIST as a critical regulator of prostate cancer cell growth and suggest a potential therapeutic approach to inhibit the growth and metastasis of androgen-independent prostate cancer through inactivation of the TWIST gene.

Overexpression of Id-1 in prostate cancer cells promotes angiogenesis through the activation of vascular endothelial growth factor (VEGF)

Androgen-independent metastatic prostate cancer is the main cause of cancer related death in men. One of the reasons for this is the lack of understanding of the molecular mechanisms leading to the metastatic progression of prostate cancer. In this study, we have demonstrated that overexpression of Id-1 (inhibitor of differentiation/DNA synthesis), a member of the helix-loop-helix family proteins, is a key factor in promoting angiogenesis through activation of the vascular endothelial growth factor (VEGF) in prostate cancer cells. Using prostate cancer cells ectopically transfected with the Id-1 gene, we found that upregulation of Id-1 induced VEGF secretion through activation of the VEGF gene transcription. Downregulation of Id-1, however, led to the suppression of VEGF secretion and its gene promoter activity. The association between Id-1 and VEGF was also confirmed on human xenografts by immunohistochemical staining. In addition, the growth medium generated by the Id-1 expressing cells was able to promote morphological changes as well as capillary tube formation in human umbilical vein endothelial cells (HUVECs) at similar degrees to the recombinant human VEGF. Furthermore, inhibition of VEGF function by the treatment with an Flk-1 inhibitor, SU1498, or with the VEGF neutralizing antibody resulted in the reverse of the angiogenic effect on HUVECs. Our results suggest that overexpression of Id-1 in prostate cancer cells may provide an autocrine signal to promote angiogenesis through the activation of VEGF. Since increased Id-1 has been reported in many types of advanced human cancers, our results indicate that downregulation of Id-1 may be a novel target to inhibit the growth of metastatic cancers through the suppression of angiogenesis.

Immunotherapy (APC8015, Provenge) targeting prostatic acid phosphatase can induce durable remission of metastatic androgen-independent prostate cancer: a Phase 2 trial

BACKGROUND

Prostate cancer is the most commonly diagnosed malignancy in American men, yet treatment of its metastatic androgen-independent form remains inadequate. This mandates development of new therapies such as immunotherapy. In this Phase 2 trial, we determined the efficacy of antigen presenting cells (APCs) loaded with PA2024, a recombinant fusion protein containing prostatic acid phosphatase (PAP) and GM-CSF.

METHODS

We enrolled 21 patients with histologically documented androgen-independent prostate carcinoma that could be evaluated by radionuclide bone scan or computed tomography scan. APC8015 was prepared from a leukapheresis product; it contained autologous CD54-positive PA2024-loaded APCs with admixtures of monocytes, macrophages, B and T cells. APC8015 was infused intravenously twice, 2 weeks apart. Two weeks after the second infusion, patients received three subcutaneous injections of 1.0 mg of PA2024 1 month apart. We monitored patients' physical condition, immune response, and laboratory parameters.

RESULTS

Nineteen patients could be evaluated for response to treatment. The median time to progression was 118 days. Treatment was tolerated reasonably well; most adverse effects were secondary to APC8015 and were NCI Common Toxicity Criteria Grade 1-2. Four of the 21 patients reported Grade 3-4 adverse events. Two patients exhibited a transient 25-50% decrease in prostate-specific antigen (PSA). For a third patient, PSA dropped from 221 ng/ml at baseline to undetectable levels by week 24 and has remained so for more than 4 years. In addition, this patient's metastatic retroperitoneal and pelvic adenopathy has resolved. PBMC collected from patients for at least 16 weeks proliferated upon in vitro stimulation by PA2024. For the patient with responsive disease, PBMC could be stimulated for 96 weeks.

CONCLUSIONS

This study demonstrates a definite clinical response of androgen-independent prostate cancer to APC immunotherapy. Currently we are studying this mode of therapy in Phase 3 trials.

Development of prostate cancer treatment: the good news

Prostate cancer is the most commonly diagnosed cancer in American men representing one-third of all new cancer cases each year. This translates into one out of every six American men being diagnosed with prostate cancer over the course of their lifetimes. Over 31,000 of these men die each year from prostate cancer. Before the 1980's, 50% of men were diagnosed with widespread metastatic disease and there were few therapeutic choices for patients. The good news for patients is that, over the last 30 years there have been significant advances in detection and prognostication as well as major improvements in the surgical, radiation, and medical oncological management of prostate cancer. This review describes the evolution of these therapeutic modalities for prostate cancer. This evolution has been driven by the explosion of knowledge concerning cancer in general and in the specific biology of prostate cancer in particular over the last 30 years. This knowledge has been obtained by concentrating human and financial resources in organ specific studies of the prostate. The end result of this effort is that, today, 85% of new prostate cancer cases are diagnosed at local and regional stages and the 5-year relative prostate cancer survival rate has increased by 20% since 1985. In addition, the therapeutic approach to prostate cancer can now be individualized based on the characteristics of the patient's disease. Finally, recent data suggest that the death rate from prostate cancer is decreasing by approximately 4% per year since 1994. Further good news for patients is that new discoveries about the biology of prostate cancer are rapidly being translated into new therapies, a large number of which are currently being tested in clinical trials. Continued allocation of appropriate human and material resources should yield new, more effective therapies for prostate cancer that will further impact patient quality of life and survival in the 21st century.

Induction of cellular and humoral immune responses to tumor cells and peptides in HLA-A24 positive hormone-refractory prostate cancer patients by peptide vaccination

BACKGROUND

To assess the safety and immune response of a peptide-based immunotherapy for patients with hormone-refractory prostate cancer, a phase I clinical trial was conducted.

METHODS

This study first investigated whether cytotoxic T-lymphocyte (CTL) precursors reacting to peptide with vaccine candidates (14 peptides for HLA-A24 positive patients) were detectable in the pre-vaccination peripheral blood mononuclear cells (PBMCs) of ten patients with hormone-refractory prostate cancer. Patients were then vaccinated subcutaneously with only those peptides to which pre-vaccination PBMCs reacted (CTL precursor-oriented peptide vaccine) for up to four kinds of peptides.

RESULTS

Overall vaccinations were generally well tolerated, but most patients (nine of ten) developed grade 1 local redness and swelling at the injection site. Increased CTL response to both peptides and cancer cells were observed in four of ten patients. Anti-peptide IgG antibodies were also detected in post-vaccination sera of seven of ten patients. One patient achieved a partial response with an 89% decrease in PSA. Stable disease was demonstrated in five of ten patients (50%) for the median duration of 2 months (range, 2-5 months). There were no objective responses of measurable lesions.

CONCLUSIONS

Increase in cellular and humoral immune responses, and decrease in PSA level in some patients support further development of peptide-based immunotherapy for hormone refractory prostate cancer.

Phase II study of oxaliplatin versus oxaliplatin combined with infusional 5-fluorouracil in hormone refractory metastatic prostate cancer patients

BACKGROUND

A randomized, multicenter phase II study evaluating oxaliplatin alone (OXA) and oxaliplatin-5-fluorouracil combination (OXFU) in advanced hormone-refractory prostate cancer (HRPC) patients.

PATIENTS AND METHODS

Metastatic, pathologically proven prostate carcinoma patients, progressing despite anti-androgen therapy, received intravenous OXA (130 mg/m(2 )over 2 h), alone or with 5-FU (1000 mg/m(2)/day, continuous intravenous infusion, days 1-4), every 3 weeks. OXA patients could receive OXFU after treatment failure.

RESULTS

Fifty-four patients (26 OXA, 28 OXFU) from nine centers received 269 treatment cycles (106 OXA, 163 OXFU; median 3.5 OXA or 5 OXFU cycles per patient; range 1-10 or 1-14, respectively). Patient characteristics were similar in both arms. Three partial responses (PR) occurred in 21 evaluable OXA patients [14%; 95% confidence interval (CI) 1% to 30%], and in five of 26 evaluable OXFU patients (19%; 95% CI 7% to 39%). Clinical benefit response (pain, performance status and weight changes) was assessed in 20 OXA and 22 OXFU symptomatic patients, with more responders in the OXFU arm (39% compared with 12%). Median time to progression in the OXA and OXFU arms was 2.6 and 3.4 months, and median overall survival was 9.4 and 11.4 months, respectively. Hematotoxicity was common, but mostly mild to moderate. Neutropenia was more common in OXFU than OXA patients. After oxaliplatin failure, 12 patients received 46 cycles of OXFU and one of 11 evaluable patients had a PR.

CONCLUSION

The objective response rate, palliation benefit, survival and manageable toxicity obtained in this heavily pretreated HRPC population with OXFU merit further study.

Optimisation of treatment by applying programmable rate-controlled drug delivery technology

A number of programmable rate-controlled drug delivery technologies have been developed during the last two decades with the aim of regulating the rate of drug delivery, sustaining the duration of therapeutic action and/or targeting the delivery of drug to a specific tissue. As a result, several therapeutically beneficial outcomes can be achieved, such as: (i) controlled delivery of a therapeutic dose at a desirable rate of delivery; (ii) maintenance of drug concentrations within an optimal therapeutic range for prolonged duration of treatment; (iii) maximisation of efficacy-dose relationship; (iv) reduction of adverse effects; (v) minimisation of the need for frequent dose intake; and (vi) enhancement of patient compliance. The treatment of illness can thus be optimised. To gain a better understanding of how to optimise the treatment of illnesses by applying programmable rate-controlled drug delivery technologies, this article reviews the scientific concepts and technical principles behind the development of various programmable rate-controlled drug delivery systems that have been marketed or are under active development. Finally, the roles of these technologies in optimising therapeutic outcomes in nine therapeutic areas are discussed.

A 5-fluorodeoxyuridine prodrug as targeted therapy for prostate cancer

A method for targeted delivery of the cytotoxic agent 5-fluorodeoxyuridine (FudR) (1) to sites of metastatic prostate cancer is described. The prodrug was synthesized by coupling the active drug (FudR) to the PSA-peptide via a self-cleaving diamino acid linker to produce HSSKLQ-Leu-Aib-FudR. This prodrug serves as a substrate for prostate specific antigen (PSA). This approach permitted efficient conversion of the inactive prodrug back to the active cytotoxic state by the enzymatic activity of PSA which is highly expressed by prostate cells.

A history of prostate cancer treatment

The increased incidence of prostate cancer has led to remarkable changes in diagnosis and treatment over the past century. What were the first ways in which prostate cancer was treated, and how did these evolve into the variety of therapeutic strategies from which patients have to choose today?

Molecular biology and cellular physiology of refractoriness to androgen ablation therapy in advanced prostate cancer

We review the extensive body of data on the molecular aetiology of hormone refractory disease in metastatic prostate cancer patients. Particular emphasis is placed on the crucial role of the bone micro-environment, especially the intercellular interactions of metastatic prostate cancer cells and osteoblasts in promoting the establishment of hormone refractory disease. Resistance of tumour cells to anticancer therapies is generally viewed as a phenomenon almost exclusively determined by chromosomal defects and/or gene mutations. However, it is now well-documented that the local milieu of the bone metastases can also protect tumour cells from anticancer therapy- induced apoptosis, either independently or synergistically with resistance-related genetic alterations. A key determinant of this protection is the urokinase/plasmin cascade which modulates the local concentration of survival factors, such as insulin-like growth factor (IGF-1). The molecular pathways whereby this major growth and survival factor for prostate cancer cells exerts its anti-apoptotic effect on prostate cancer cells are discussed.

Prostate cancer and the androgen receptor: strategies for the development of novel therapeutics

The early demonstrations that prostate cancer was hormone-sensitive initiated a therapeutic strategy of hormone ablation that is still in use today. Although chemical or surgical castration reduces androgen stimulation of the androgen receptor (AR) and produces tumor regression, little survival benefit is achieved. Patients with metastatic cancer eventually relapse as their tumors progress to hormone independence. The AR is a member of the steroid receptor family; however, it manifests many unique features including: N-terminal, C-terminal interactions and antiparallel dimerization, unique N-terminal domains for co-factor recruitment, AR-specific co-activators and upstream promoter/enhancer response elements that amplify AR-mediated responses. The AR is regulated by phosphorylation and cross-talk with several signaling pathways, including MAP kinases, PKA and PKC. Non-genomic effects of AR to regulate transcription factors elk-1 and -2 have also been demonstrated. These unique features suggest mechanisms by which novel therapeutics might target and influence AR-mediated actions. Progress in this direction has been realized with the recent synthesis of non-steroidal androgen agonists that may have tissue-selective effects.

Immunotherapy of hormone-refractory prostate cancer with antigen-loaded dendritic cells

PURPOSE

Provenge (Dendreon Corp, Seattle, WA) is an immunotherapy product consisting of autologous dendritic cells loaded ex vivo with a recombinant fusion protein consisting of prostatic acid phosphatase (PAP) linked to granulocyte-macrophage colony-stimulating factor. Sequential phase I and phase II trials were performed to determine the safety and efficacy of Provenge and to assess its capacity to break immune tolerance to the normal tissue antigen PAP.

PATIENTS AND METHODS

All patients had hormone-refractory prostate cancer. Dendritic-cell precursors were harvested by leukapheresis in weeks 0, 4, 8, and 24, loaded ex vivo with antigen for 2 days, and then infused intravenously over 30 minutes. Phase I patients received increasing doses of Provenge, and phase II patients received all the Provenge that could be prepared from a leukapheresis product.

RESULTS

Patients tolerated treatment well. Fever, the most common adverse event, occurred after 15 infusions (14.7%). All patients developed immune responses to the recombinant fusion protein used to prepare Provenge, and 38% developed immune responses to PAP. Three patients had a more than 50% decline in prostate-specific antigen (PSA) level, and another three patients had 25% to 49% decreases in PSA. The time to disease progression correlated with development of an immune response to PAP and with the dose of dendritic cells received.

CONCLUSION

Provenge is a novel immunotherapy agent that is safe and breaks tolerance to the tissue antigen PAP. Preliminary evidence for clinical efficacy warrants further exploration.