Treatment options in hormone-refractory prostate cancer: current and future approaches

Predictors of Testicular Cancer Mortality in Brazil: A 20-Year Ecological Study

Testicular cancer is common in young men, and early detection and multimodality treatment can lead to successful outcomes. This study aims to identify sociodemographic and risk factors associated with higher testicular cancer mortality and poorer survival rates, while examining the impact of diagnostic and treatment procedures on reducing mortality. The retrospective ecological study analyzed mortality data from testicular cancer in Brazil from 2001 to 2020. Sociodemographic variables such as marital status, age, birth period, year of death (cohort), race, and geographic region were assessed. Risk factors included cryptorchidism and pesticide exposure. Data were subjected to statistical analysis, which revealed an increasing trend in mortality after 2011 among persons born after 1976 in the 15-40 age group. Individuals in the South Region, whites, and singles had higher age-standardized mortality rates (ASMRs), while singles had lower survival rates. The Northeast region had a higher survival rate. Fungicides and insecticides increase ASMR in Brazil. Herbicides increase ASMR in the Northeast and Midwest regions and insecticides increase ASMR in the Northeast, Southeast, and Midwest regions. High rates of implementation of diagnostic procedures in the Midwest were not sufficient to reduce ASMR. No treatment procedure was associated with mortality at the national or regional level.

Angiogenesis and prostate cancer: MicroRNAs comes into view

Angiogenesis, the formation of new blood vessels, is an important stage in the growth of cancer. Extracellular matrix, endothelial cells, and soluble substances must be carefully coordinated during the multistep procedure of angiogenesis. Inducers and inhibitors have been found to control pretty much every phase. In addition to benign prostatic hyperplasia, prostatic intraepithelial neoplasia, and angiogenesis have a critical role in the initiation and progression of prostate cancer. MicroRNA (miRNA) is endogenous, short, non-coding RNA molecules of almost 22 nucleotides play a role in regulating cellular processes and regulating several genes' expression. Through controlling endothelial migration, differentiation, death, and cell proliferation, miRNAs have a significant function in angiogenesis. A number of pathological and physiological processes, particularly prostate cancer's emergence, depend on the regulation of angiogenesis. Investigating the functions played with miRNAs in angiogenesis is crucial because it might result in the creation of novel prostate cancer therapies that entail regulating angiogenesis. The function of several miRNAs and its targeting genes engaged in cancer of the prostate angiogenesis will be reviewed in this review in light of the most recent developments. The potential clinical utility of miRNAs potentially a novel therapeutic targets will also be explored, as well as their capacity to control prostate cancer angiogenesis and the underlying mechanisms.

Estrogen Enhances the Expression of the Multidrug Transporter Gene ABCG2-Increasing Drug Resistance of Breast Cancer Cells through Estrogen Receptors

Background: Multidrug resistance is a major obstacle in the successful therapy of breast cancer. Studies have proved that this kind of drug resistance happens in both human cancers and cultured cancer cell lines. Understanding the molecular mechanisms of drug resistance is important for the reasonable design and use of new treatment strategies to effectively confront cancers. Results: In our study, ATP-binding cassette sub-family G member 2 (ABCG2), adenosine triphosphate (ATP) synthase and cytochrome c oxidase subunit VIc (COX6C) were over-expressed more in the MCF-7/MX cell line than in the normal MCF7 cell line. Therefore, we believe that these three genes increase the tolerance of MCF7 to mitoxantrone (MX). The data showed that the high expression of COX6C made MCF-7/MX have more stable on mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) expression than normal MCF7 cells under hypoxic conditions. The accumulation of MX was greater in the ATP-depleted treatment MCF7/MX cells than in normal MCF7/MX cells. Furthermore, E2 increased the tolerance of MCF7 cells to MX through inducing the expression of ABCG2. However, E2 could not increase the expression of ABCG2 after the inhibition of estrogen receptor α (ERα) in MCF7 cells. According to the above data, under the E2 treatment, MDA-MB231, which lacks ER, had a higher sensitivity to MX than MCF7 cells. Conclusions: E2 induced the expression of ABCG2 through ERα and the over-expressed ABCG2 made MCF7 more tolerant to MX. Moreover, the over-expressed ATP synthase and COX6c affected mitochondrial genes and function causing the over-expressed ABCG2 cells pumped out MX in a concentration gradient from the cell matrix. Finally lead to chemoresistance.

Liver protects metastatic prostate cancer from induced death by activating E-cadherin signaling

Liver is one of the most common sites of cancer metastasis. Once disseminated, the prognosis is poor as these tumors often display generalized chemoresistance, particularly for carcinomas that derive not from the aerodigestive tract. When these cancers seed the liver, the aggressive cells usually undergo a mesenchymal to epithelial reverting transition that both aids colonization and renders the tumor cells chemoresistant. In vitro studies demonstrate that hepatocytes drive this phenotypic shift. However, the in vivo evidence and the molecular signals that protect these cells from induced death are yet to be defined. Herein, we report that membrane surface E-cadherin-expressing prostate cancer cells were resistant to cell death by chemotherapeutic drugs but E-cadherin null cells or those expressing E-cadherin only in the cytoplasm were sensitive to death signals and chemotherapies both in vitro and in vivo. While cell-cell E-cadherin ligandation reduced mitogenesis, this chemoprotection was proliferation-independent as killing of both 5-ethynyl-2'-deoxyuridine-positive (or Ki67⁺ ) and 5-ethynyl-2'-deoxyuridine-negative (Ki67^- ) cells was inversely related to membrane-bound E-cadherin. Inhibiting the canonical survival kinases extracellular signal-regulated protein kinases, protein kinase B, and Janus kinase, which are activated by chemotherapeutics in epithelial cell-transitioned prostate cancer, abrogated the chemoresistance both in cell culture and in animal models of metastatic cancer. For disseminated tumors, protein kinase B disruption in itself had no effect on tumor survival but was synergistic with chemotherapy, leading to increased killing.

CONCLUSION

Liver microenvironment-driven phenotypic switching of carcinoma cells and subsequent survival signaling results in activation of canonical survival pathways that protect the disseminated prostate cancer liver micrometastases in a proliferation-independent manner, and these pathways can be targeted as an adjuvant treatment to improve the efficacy of traditional chemotherapeutics (Hepatology 2016;64:1725-1742).

Dichotomy in the Epigenetic Mark Lysine Acetylation is Critical for the Proliferation of Prostate Cancer Cells

The dynamics of lysine acetylation serve as a major epigenetic mark, which regulates cellular response to inflammation, DNA damage and hormonal changes. Microarray assays reveal changes in gene expression, but cannot predict regulation of a protein function by epigenetic modifications. The present study employs computational tools to inclusively analyze microarray data to understand the potential role of acetylation during development of androgen-independent PCa. The data revealed that the androgen receptor interacts with 333 proteins, out of which at least 92 proteins were acetylated. Notably, the number of cellular proteins undergoing acetylation in the androgen-dependent PCa was more as compared to the androgen-independent PCa. Specifically, the 32 lysine-acetylated proteins in the cellular models of androgen-dependent PCa were mainly involved in regulating stability as well as pre- and post-processing of mRNA. Collectively, the data demonstrate that protein lysine acetylation plays a crucial role during the transition of androgen-dependent to -independent PCa, which importantly, could also serve as a functional axis to unravel new therapeutic targets.

A new target for an old drug: identifying mitoxantrone as a nanomolar inhibitor of PIM1 kinase via kinome-wide selectivity modeling

The rational design of selective kinase inhibitors remains a great challenge. Here we describe a physics-based approach to computationally modeling the kinase inhibitor selectivity profile. We retrospectively assessed this protocol by computing the binding profiles of 17 well-known kinase inhibitors against 143 kinases. Next, we predicted the binding profile of the chemotherapy drug mitoxantrone, and chose the predicted top five kinase targets for in vitro kinase assays. Remarkably, mitoxantrone was shown to possess low nanomolar inhibitory activity against PIM1 kinase and to inhibit the PIM1-mediated phosphorylation in cancer cells. We further determined the crystal complex structure of PIM1 bound with mitoxantrone, which reveals the structural and mechanistic basis for a novel mode of PIM1 inhibition. Although mitoxantrone's mechanism of action had been originally thought to act through DNA intercalation and type II topoisomerase inhibition, we hypothesize that PIM1 kinase inhibition might also contribute to mitoxantrone's therapeutic efficacy and specificity.

Marine- and plant-derived ω-3 fatty acids differentially regulate prostate cancer cell proliferation

Fish oil contains the marine ω-3 polyunsaturated fatty acids (ω-3 PUFAs) docosahexaenoic (DHA) and eicosapentaenoic acid (EPA). The consumption of diets rich in these fatty acids is associated with a decreased incidence of prostate cancer. However, there is limited knowledge regarding the non-marine ω-3 PUFA α-linolenic acid (ALA). To study which ω-3 PUFAs are more effective in prostate cancer prevention, and whether the mechanisms of action are conserved between them, we investigated the effect of DHA, EPA and ALA on the human prostate cancer cell lines PC-3 and LNCaP. Different trends of inhibition of PC-3 cell proliferation were observed for the three ω-3 PUFA, with DHA having the most pronounced effects on cell proliferation, while ALA had the minimum effects of the three ω-3 PUFAs. All the ω-3 PUFAs decreased fatty acid synthase (FASN) mRNA. Concerning genes involved in inflammation, cell cycle and apoptosis, DHA regulated the most genes in all categories, followed by EPA and then ALA. In addition, DHA and EPA increased the gene expression of the pro-apoptotic protein activating transcription factor 3 mRNA. Moreover, these two fatty acids significantly induced apoptosis. In conclusion, while some mechanisms of cancer cell inhibition are conserved among ω-3 PUFA, the extent, magnitude, and duration of transcriptional changes vary for each individual fatty acid.

Assessment of the Effects of Zoledronic Acid Therapy on Bone Metabolic Indicators in Hormone-Resistant Prostate Cancer Patients with Bone Metastatasis

Purpose. Assessment of effects of zoledronic acid therapy on bone metabolic indicators in hormone-resistant prostate cancer patients with bone metastasis. Material and Methods. Hormone-resistant prostate cancer patients who were identified to have metastases in their bone scintigraphy were taken to trial group. Before administration of zoledronic acid, routine tests for serum calcium, total alkalen phosphates were studied. Sample sera for bone metabolic indicators BALP, PINP, and ICTP were collected. Bone pain was assessed via visual analogue scale and performance via Karnofsky performance scale. Four mg zoledronic acid was administered intravenously once a month. Results. When serum levels of bone forming indicators PINP; BALP were compared before and after therapy, there were insignificant decreases (P = .33, P = .21, resp.). Serum levels of bone destruction indicator ICTP was compared, and there was a significant decrease after zoledronic acid therapy (P = .04). When performances of the patients were compared during therapy period, performances decreased significantly due to progress of illness (P = .01). All patients had ostalgia caused by bone metastases at various degrees. Significant decrease in pain scores was observed (P < .01). Conclusion. Zoledronic acid therapy decreased bone destruction and was effective in palliation of pain in patient with bone metastasis. Using bone metabolic indicators during followup of zoledronic acid therapy might be useful.

Involvement of Fatty Acid Binding Protein 5 and PPARβ/δ in Prostate Cancer Cell Growth

Fatty acid binding protein 5 (FABP5) delivers ligands from the cytosol directly to the nuclear receptor PPARβ/δ and thus facilitates the ligation and enhances the transcriptional activity of the receptor. We show here that expression levels of both FABP5 and PPARβ/δ are correlated with the tumorigenic potential of prostate cancer cell lines. We show further that FABP5 comprises a direct target gene for PPARβ/δ and thus the binding protein and its cognate receptor are engaged in a positive feedback loop. The observations demonstrate that, similarly to effects observed in mammary carcinomas, activation of the FABP5/PPARβ/δ pathway induces PPARβ/δ target genes involved in cell survival and growth and enhances cell proliferation and anchorage-independent growth in prostate cancer cells. Furthermore, the data show that downregulation of either FABP5 or PPARβ/δ inhibits the growth of the highly malignant prostate cancer PC3M cells. These studies suggest that the FABP5/PPARβ/δ pathway may play a general role in facilitating tumor progression and that inhibition of the pathway may comprise a novel strategy in treatment of cancer.

Dynamic assessment of mitoxantrone resistance and modulation of multidrug resistance by valspodar (PSC833) in multidrug resistance human cancer cells

P-glycoprotein (Pgp), a member of the ATP-binding cassette transporter family, is one of the major causes for multidrug resistance (MDR). We report using confocal microscopy to study the roles of Pgp in mediating the efflux of the anticancer agent mitoxantrone and the reversal of MDR by the specific Pgp inhibitor valspodar (PSC833). The net uptake and efflux of mitoxantrone and the effect of PSC833 were quantified and compared in Pgp-expressing human cancer MDA-MB-435 (MDR) cells and in parental wild-type cells. The MDR cells, transduced with the human Pgp-encoding gene MDR1 construct, were approximately 8-fold more resistant to mitoxantrone than the wild-type cells. Mitoxantrone accumulation in the MDR cells was 3-fold lower than that in the wild-type cells. The net uptake of mitoxantrone in the nuclei and cytoplasm of MDR cells was only 58 and 67% of that in the same intracellular compartment of the wild-type cells. Pretreatment with PSC833 increased the accumulation of mitoxantrone in the MDR cells to 85% of that in the wild-type cells. In living animals, the accumulation of mitoxantrone in MDA-MB-435mdr xenograft tumors was 61% of that in the wild-type tumors. Administration of PSC833 to animals before mitoxantrone treatment increased the accumulation of mitoxantrone in the MDR tumors to 94% of that in the wild-type tumors. These studies have added direct in vitro and in vivo visual information on how Pgp processes anticancer compounds and how Pgp inhibitors modulate MDR in resistant cancer cells.

Targeting prostate cancer based on signal transduction and cell cycle pathways

Prostate cancer remains a leading cause of death in men despite increased capacity to diagnose at earlier stages. After prostate cancer has become hormone independent, which often occurs after hormonal ablation therapies, it is difficult to effectively treat. Prostate cancer may arise from mutations and dysregulation of various genes involved in regulation signal transduction (e.g., PTEN, Akt, etc.,) and the cell cycle (e.g., p53, p21(Cip1), p27(Kip1), Rb, etc.,). This review focuses on the aberrant interactions of signal transduction and cell cycle genes products and how they can contribute to prostate cancer and alter therapeutic effectiveness.

Prostate cancer in the elderly

Prostate cancer is the second leading cause of cancer deaths among men. Despite earlier diagnosis due to prostate specific antigen (PSA) screening, it is still a disease of the elderly. Diagnosis is based on digital rectal examination (DRE) and PSA assessment. Refinements in PSA testing (age-specific reference ranges, free PSA, PSA density and velocity) increased specificity and limited unnecessary prostate biopsies. Diagnosis in earlier stages (T1 and T2) commonly leads to cure with current treatment modalities. These include radical prostatectomy, external beam radiotherapy and brachytherapy. Other treatment options under development include cryotherapy and high-intensity focused ultrasound. Metastatic prostate cancer is incurable and treatment is based on hormonal therapy. Cytotoxic chemotherapy has only limited role in hormone-independent prostate cancer. Radioisotopes and biphosphonates may alleviate bone pain and prevent osteoporosis and pathological fractures. Follow-up is based on PSA. Prognostic factors for recurrence include stage, Gleason score, pre- and posttreatment PSA. Quality of life issues play an important role in selecting treatment, especially in the elderly due to comorbidities that may negatively affect the overall quality of life. A holistic approach is recommended addressing all quality of life issues without focus only in cancer control.

Diethylstilboestrol versus bicalutamide in hormone refractory prostate carcinoma: a prospective randomized trial

OBJECTIVE

To compare the efficacy of diethylstilboestrol (DES) with bicalutamide in the treatment of hormone refractory prostate cancer in relation to its effect on prostate-specific antigen (PSA) and survival.

METHODS

Patients on LHRH analogues for prostate carcinoma with evidence of biochemical or clinical progression were randomized into one of the treatment arms (n=58). The first group (group A, n=26) received 1 mg of DES with 75 mg of aspirin per day in addition to the primary hormonal treatment. The second group (group B, n=32) received bicalutamide at a dose of 50 mg/day in addition to the primary treatment. Patients were followed up every 3 months with their PSA being checked and were also monitored for any clinical progression and adverse effects as a result of treatment. Any adverse event occurring after patients were started on treatment was attributed to the drug and patients were clinically assessed at each visit. Failure of treatment was defined as a 50% or greater increase in PSA after commencing treatment. Once randomized, all patients were followed up for survival regardless of failure of second-line hormonal manipulation.

RESULTS

The mean age of the patients was 76.7 years (60-88, SD 7.4) in group A and 76 years (67-86, SD 6.9) in group B. Twelve patients in each group had metastatic disease. The median follow-up periods for both groups were 24 months (range 6-48 in group A, range 3-54 in group B). 65% of the patients in group A (17/26) and 43.5% (14/32) in group B had a fall in their PSA levels (p=0.08, Fisher's exact test) with 23% (6/26) and 31% (10/32) having a >50% response respectively (p=0.34, Fisher's exact test). Mean PSA nadir in those who responded were 20.6 ng/ml (range 1.6-59.4) and 7.41 ng/ml (range 0.1-42.6) in groups A and B respectively. The median duration of response was 9 months (3-18 months) for group A and 12 months (3-18 months) for group B. Seven patients in group A and 6 in group B experienced adverse events. Three of the 7 in the group A experienced cardiovascular related adverse effects (1 congestive cardiac failure, 1 pulmonary embolism and 1 stroke). At the end of the study period, 14 (54%) of group A patients were alive and 12 (46%) were dead. In group B, 15 (47%) were alive, 16 (50%) were dead and 1 (3%) lost to follow-up. At the completion of the study, 3 patients in each group were still on treatment.

CONCLUSION

Low-dose DES and 50 mg of bicalutamide per day are equally effective in hormone refractory prostate carcinoma with respect to biochemical response, although DES has more severe adverse effects. This is a small sample and larger multicentre trials are needed to give us a definite conclusion.

Irofulven demonstrates clinical activity against metastatic hormone-refractory prostate cancer in a phase 2 single-agent trial

BACKGROUND

The primary objective of this study was to assess the antitumor activity of irofulven in patients with hormone-refractory prostate cancer by measuring a sustained decrease of 50% or greater in serum prostate-specific antigen (PSA) levels.

PATIENTS AND METHODS

Forty-two patients (median age, 73 years) received at least 1 dose of 10.6 mg/m2 irofulven per day on days 1-5 of a 28-day course. Eligible patients had pathologically confirmed metastatic hormone-refractory adenocarcinoma of the prostate and had not received prior cytotoxic chemotherapy.

RESULTS

Forty-two patients received a median of 3 courses of irofulven. Thirty-two patients received at least 2 courses of therapy and were evaluable for efficacy. Four patients (13%) achieved partial response, with a median duration of 2.9 months (range, 2.6-5.8 months). Twenty-seven patients (84%) had disease stabilization and 1 patient (3%) progressed on study. Median progression-free survival was 3.2 months (95% confidence interval, 2.3-4.2 months), with a median progression-free survival of 4.2 months (range, 3.5-6.9 months) for responders. Grade 4 toxicities consisted of thrombocytopenia, anemia, and neutropenia, occurring in 1 patient each. The most common treatment-related grade 3 nonhematologic toxicities included asthenia (19% of patients), vomiting (14%), nausea (12%), and infection without grade 3/4 neutropenia (10%).

CONCLUSION

Irofulven shows activity in hormone-refractory prostate cancer and has an acceptable safety profile, warranting further investigation of this drug, particularly in combination therapies.

Angiogenesis-targeted therapies in prostate cancer

Most patients with metastatic prostate cancer will respond initially to ablation of gonadal androgen production. Eventually, all patients will develop progressive disease despite continued androgen suppression, a condition called androgen-independent or hormone-refractory prostate cancer. Hormone-refractory prostate cancer is characterized by virulent biologic and clinical behavior. Recently, docetaxel-based chemotherapy has been shown to improve survival and quality of life in this disease when compared with mitoxantrone-based therapy. However, results remain suboptimal. Recently, there have been remarkable advances in the delineation of the mechanisms of cancer growth, metastasis, and the intricate interactions between tumor cells and the surrounding normal tissues. The accumulated evidence has confirmed the importance of angiogenesis in these processes and validated the theory that inhibition of neovascularization is a promising therapeutic anticancer strategy. Currently, dozens of compounds that interfere with different steps of the angiogenic cascade are in preclinical and clinical development. Some of these agents have exhibited promising antitumor activity in hormone-refractory prostate cancer. This review summarizes the molecular mechanisms implicating angiogenesis in the development and progression of advanced-stage prostate cancer, as well as the drug development efforts that are targeting this process.

Novel molecular aspects of prostate carcinogenesis

Prostate adenocarcinoma is one of the most frequently diagnosed forms of cancer in the male population of the Western world. The pivotal role of androgen and its receptor in this disease has been abundantly documented and indeed, chemical castration and treatment with antiandrogens are now standard therapies. However, relapse is often observed after 18-24 months, due to the remarkable ability of prostate tumour cells to adapt to low or undetectable androgen levels. Amplification and mutations of the androgen receptor (AR) gene have been described as well as alterations in cofactor expression and crosstalk with other signalling pathways. Another recent line of research focused on the re-programming of gene expression taking place in prostate tumours. Global expression profiling of normal and cancerous prostate tissues led to the identification of tumour-distinctive patterns. Validation studies are currently underway to identify novel drug targets as well as diagnostic and outcome prediction markers.

Cost-effectiveness analysis of bicalutamide (Casodex) for adjuvant treatment of early prostate cancer

OBJECTIVES

To assess the cost-effectiveness of bicalutamide (Casodex) as adjuvant treatment in early prostate cancer (EPC).

METHODS

A Markov state transition model was developed, using disease progression rates from a large (N = 8113) clinical trial program comparing bicalutamide in addition to standard care with standard care alone. Utility scores for different disease stages were obtained from published reports. Costs of disease progression were obtained from a retrospective patient chart analysis in six Belgian centers (n = 60). The time horizon was 15 years and the analysis was conducted from the public payer perspective.

RESULTS

The model showed good validity in predicting clinical outcomes. At a time horizon of 15 years, an incremental cost-effectiveness of 27,059 euros/QALY was obtained. The main factors influencing conclusions included the time horizon, the duration of bicalutamide treatment, which was set at a maximum (5 years) in the base case, and possible differences in prognosis of metastatic cancer between comparators. Also the discounting of health effects significantly altered cost-effectiveness ratios. Many of these influences are inherently associated with any cost-effectiveness analysis related to treatment of early, slowly progressing malignancies because such an analysis requires a sufficient time horizon to include not only the treatment costs but its benefits as well.

CONCLUSION

Based on the current data, bicalutamide appears to be a cost-effective option for adjuvant treatment of EPC.

RETRACTED: Proanthocyanidins from grape seeds inhibit expression of matrix metalloproteinases in human prostate carcinoma cells, which is associated with the inhibition of activation of MAPK and NFκB

Prostate cancer (PCA) is the second most frequently diagnosed and leading cause of cancer-related deaths in men in the USA. The recognition that matrix metalloproteinases (MMPs) facilitate tumor cell invasion and metastasis of PCA has led to the development of MMP inhibitors as cancer therapeutic agents. As part of our efforts to develop newer and effective chemopreventive agents for PCA, we evaluated the effect of proanthocyanidins from grape seeds (GSP) on metastasis-specific MMP-2 and -9 in human prostate carcinoma DU145 cells by employing western blot and gelatinolytic zymography. Treatment of GSP dose-dependently inhibited cell proliferation (15-100% by 5-80 microg/ml of GSP), viability (30-80% by 20-80 microg/ml of GSP) and fibroblast conditioned medium (FCM)-induced expression of MMP-2 and -9 in DU145 cells. Since the signaling cascade of mitogen-activated protein kinases (MAPK) have been shown to regulate the expression of MMPs in tumor cells, we found that the treatment of DU145 cells with GSP (20-80 microg/ml) resulted in marked inhibition of FCM-induced phosphorylation of extracellular signal regulated kinase (ERK)1/2 and p38 but had little effect on c-Jun N-terminal kinase under similar experimental conditions. GSP treatment (20-80 microg/ml) to DU145 cells also dose-dependently inhibited FCM-induced activation of NF kappa B concomitantly with inhibition of MMP-2 and -9 expression in the same system. Additionally, the treatment of inhibitors of MEK (PD98059) and p38 (SB203580) to DU145 cells resulted in the reduction of FCM-induced phosphorylation of ERK1/2 and p38 concomitantly marked reduction in MMP-2 and -9 expressions. In further studies, treatment of androgen-sensitive LNCaP cells with a synthetic androgen R1881, resulted in an increase of MMP-2 and -9, which were completely abrogated in the presence of GSP (20-60 microg/ml). These data suggest that inhibition of metastasis-specific MMPs in tumor cells by GSP is associated with the inhibition of activation of MAPK and NF kappa B pathways, and thus provides the molecular basis for the development of GSP as a novel chemopreventive agent for both androgen-sensitive and -insensitive prostate cancer therapies.

Antitumor activity of irofulven monotherapy and in combination with mitoxantrone or docetaxel against human prostate cancer models

BACKGROUND

Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114) is a novel antitumor agent currently undergoing clinical trials in hormone-refractory prostate cancer. This report examines the efficacy of irofulven alone or in combination with mitoxantrone or docetaxel against androgen-independent prostate cancer cell lines.

METHODS

To elucidate the activity of irofulven monotherapy and in combination, PC-3 and DU-145 cell lines were utilized in cellular viability assessments and tumor growth inhibition studies.

RESULTS

Viability assays with irofulven and mitoxantrone show additive to synergistic activity. Furthermore, irofulven and mitoxantrone in combination exhibit enhanced antitumor activity against PC-3 and DU-145 xenografts. Additive combination effects are also observed when irofulven and docetaxel were tested against PC-3 xenografts and curative activity (8/10 CR) is observed in DU-145 xenografts.

CONCLUSIONS

These studies demonstrate that irofulven displays strong activity as monotherapy and in combination with mitoxantrone or docetaxel against androgen-independent prostate cancer in vitro and in vivo; thus, supporting the clinical investigation of irofulven against hormone-refractory prostate cancer.

The androgen receptor: a potential target for therapy of prostate cancer

The androgen receptor plays a pivotal role in the prostate. Its primary function is to provide responsive gene products for differentiation and growth, but under abnormal conditions it contributes to the development of prostate cancer. The goal of this review is to elucidate the molecular functions of the androgen receptor and its role in prostate cancer. Initially the function of the androgen receptor will be described. Next, the clinical diagnosis, epidemiological impact, and treatments of androgen-dependent and -independent prostate cancer will be discussed. Finally we will examine how the mechanism of androgen action has played a role in the translation of new therapies and how this may influence future treatment modalities of prostate cancer.

Hypoxia induced resistance to doxorubicin in prostate cancer cells is inhibited by low concentrations of glyceryl trinitrate

PURPOSE

Tumor hypoxia has been correlated with metastasis and resistance to chemotherapy. Hypoxia is also associated with human prostate cancers, which are highly resistant to chemotherapy. We hypothesized that hypoxia contributes to chemoresistance in prostate cancer cells and this hypoxia induced chemoresistance can be inhibited by low concentrations of nitric oxide (NO) mimetics.

MATERIALS AND METHODS

Human PC-3 and mouse TRAMP-C2 prostatic adenocarcinoma cells were incubated in 20% or 0.5% O(2) for 12 hours with or without glyceryl trinitrate (GTN) (0.1 nM). This treatment was followed by a 1-hour incubation with doxorubicin and survival was assessed by clonogenic assays. Western blot analysis was used to measure NO synthase levels. The effect of hypoxia and GTN on cell cycle distribution was determined by flow cytometry.

RESULTS

Hypoxic pre-incubation of the 2 cell lines resulted in increased survival following exposure to doxorubicin. Co-incubation of PC-3 and TRAMP-C2 cells with GTN (0.1 nM) inhibited the hypoxia induced resistance to doxorubicin. Each cell line expressed all 3 NO synthase isoforms at levels that were not significantly affected by O(2) concentrations. Cell cycle analysis revealed that there was no significant difference in the distribution of PC-3 cells at each stage of the cycle. However, incubation under hypoxia resulted in a small decrease in the number of TRAMP-C2 cells in S-phase.

CONCLUSIONS

These findings indicate that NO may have an important role in the regulation of chemosensitivity in prostate cancer cells. Furthermore, the results suggest that GTN administration may represent a means of chemosensitizing prostatic carcinomas.

Current strategies in the management of hormone refractory prostate cancer

Prostate cancer is the most common cancer diagnosed in American males, and is the second leading cause of cancer-related deaths. Most patients who develop metastatic disease will initially respond to androgen deprivation, but response is invariably temporary. Most patients will develop androgen-independent ("hormone-refractory") disease that results in progressive clinical deterioration and ultimately death. This progression to androgen independence is accompanied by increasingly evident DNA instability and alterations in genes and gene expression, including mutations in p53, over-expression of Bcl2, and mutations in the androgen receptor gene, among others. Treatment options for hormone refractory disease include intensive supportive care, radiotherapy, bisphosphonates, second-line hormonal manipulations, cytotoxic chemotherapy and investigational agents. A post-treatment reduction in the level of prostate specific antigen (PSA) by 50% has been shown to correlate with survival and has been accepted by consensus as a valid endpoint in clinical trials. Chemotherapeutic agents such as mitoxantrone, estramustine, and the taxanes have yielded improved response rates and palliative benefit, but not improved survival. Therefore, current efforts must be focused on enrolling patients onto clinical trials of investigational agents with novel mechanisms of action, and on using survival, time to progression, and quality of life as end points in routine clinical practice.

Grape seed extract inhibits EGF-induced and constitutively active mitogenic signaling but activates JNK in human prostate carcinoma DU145 cells: possible role in antiproliferation and apoptosis

A loss of functional androgen receptor and an enhanced expression of growth factor receptors and associated ligands are causal genetic events in prostate cancer (PCA) progression. These genetic alterations lead to an epigenetic mechanism where a feedback autocrine loop between membrane receptor and ligand (e.g. EGFR-TGFalpha) results in a constitutive activation of MAPK-Elk1-AP1-mediated mitogenic signaling in human PCA at an advanced and androgen-independent stage. We rationalized that inhibiting these epigenetic events could be useful in controlling advanced PCA growth. Recently, we found that grape seed extract (GSE), a dietary supplement rich in flavonoid procyanidins, inhibits advanced and androgen-independent human PCA DU145 cell growth in culture and nude mice. Here, we performed detailed mechanistic studies to define the effect of GSE on EGFR-Shc-MAPK-Elk1-AP1-mediated mitogenic signaling in DU145 cells. Pretreatment of serum-starved cells with GSE resulted in 70% to almost complete inhibition of EGF-induced EGFR activation and 50% to complete inhibition of Shc activation, which corroborated with a comparable decrease in EGF-induced Shc binding to EGFR. Conversely, EGF-induced ERK1/2 phosphorylation was inhibited only by lower doses of GSE; in fact, higher doses showed an increase. Additional studies showed that GSE alone causes a dose- and time-dependent increase in ERK1/2 phosphorylation in starved DU145 cells that is inhibited by an MEK1 inhibitor PD98059. Independent of this increase in ERK1/2 phosphorylation, GSE showed a strong inhibition of ERK1/2 kinase activity to Elk1 in both cellular and cell-free systems. GSE treatment of cells also inhibited both EGF-induced and constitutively active Elk1 phosphorylation and AP1 activation. GSE treatment also showed DNA synthesis inhibition in starved and EGF-stimulated cells as well as loss of cell viability and apoptotic death that was further increased by adding MEK1 inhibitor. Since GSE strongly induced apoptosis independent of its affect on an increase in phospho-ERK1/2, we hypothesized that apoptotic effect of GSE could be by other mechanism(s) including its effect on stress-associated MAPK, the JNK. Indeed, GSE-treated cells showed a strong and sustained increase in phospho-JNK1/JNK2 levels, JNK activity and phospho-cJun levels. An inhibition of GSE-induced JNK activation by a novel JNK inhibitor SP600125 resulted in a significant reversal of GSE-induced apoptotic death suggesting the involvement of JNK activation by GSE in its apoptosis response. Together, these results suggest that anticancer effects of GSE in PCA be mediated via impairment of EGFR-ERK1/2-Elk1-AP1-mediated mitogenic signaling and activation of JNK causing growth inhibition and apoptosis, respectively.

Prostate cancer cell proliferation is strongly reduced by the epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 in vitro on human cell lines and primary cultures

PURPOSE

To investigate the effects of the epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) ZD1839 ('Iressa') on the cellular proliferation of androgen-sensitive and androgen-independent human prostatic cancer cell lines and primary cultures in vitro.

EXPERIMENTAL DESIGN

In this study, we investigated the effects of the quinazoline ZD1839, a potent, selective EGFR-TKI, on the EGFR autophosphorylation and cellular proliferation of androgen-sensitive (ND1, LNCaP, and ALVA-31) and androgen-independent (PC3, DU145, and TSU-Pr1) human prostatic cancer cell lines and 20 primary cultures derived from human prostatic cancer tissue.

RESULTS

EGFR was present and phosphorylated in all cell lines tested. ZD1839 reduced EGFR autophosphorylation in intact cell lines with IC(50)s of 0.46-0.97 microM, and inhibited cellular proliferation with IC(50)s of 0.37-1.03 microM. Constitutive EGFR autophosphorylation was low in primary cell cultures, but addition of EGF (50 ng/ml) caused marked EGFR autophosphorylation; cellular proliferation in the presence of EGF was inhibited by ZD1839 with a mean IC(50) of 0.45 microM. At doses >1 microM, ZD1839 induced apoptosis in both androgen-dependent and androgen-independent PCa cell lines. CONCLUSION. Our experiments suggest that EGFR-TKIs such as ZD1839 may have potential in blocking the growth and progression of human prostatic cancers even in early phases of the disease.

Early versus late hormonal therapy: debating the issues

Hormonal therapy for prostate cancer has traditionally been reserved for advanced disease, but current evidence suggests that earlier use can confer a survival advantage. Survival benefit has been observed among patients with TNM stage T3 tumors who were treated with hormonal therapy plus external irradiation. Patients with nodal metastases (D1) who received immediate treatment with hormonal therapy after radical prostatectomy and pelvic lymphadenectomy also survived longer than those who were treated only after disease progression. The patients included in these studies are distinguished from those exhibiting "biochemical" failure (ie, increased levels of prostate-specific antigen, despite local therapy). It is in these patients that the use of hormonal therapy is, at present, controversial. For the purpose of identifying the subgroup of patients who might specifically benefit from early hormonal treatment, various schemas for defining predictors of poor outcome have been developed, including nomograms and artificial neural network programs. As with hormonal therapy, the use of chemotherapy in prostate cancer has been regarded as a palliative option for hormone-refractory disease. However, positive experience with early chemotherapy in other cancers suggests that such strategies might be similarly beneficial in prostate cancer. Limited clinical data show that chemotherapy combined with hormonal therapy can increase the initial response rate and prolong survival in locally advanced disease (T3 or D2), but not in metastatic tumors. An international trial is under way to evaluate the role of adjuvant chemotherapy in patients with localized prostate cancer who are at high risk of relapse after radical prostatectomy. Thus, accumulating evidence provides a rationale for continued investigation into the use of early hormonal therapy in selected patients.

Cytochrome P450-based cancer gene therapy: current status

Results from a number of preclinical studies have demonstrated that a P450-based gene-directed enzyme prodrug therapy (GDEPT) strategy for the treatment of cancer is both safe and efficacious. This strategy has now moved forward into the clinic. At least two different approaches using different delivery methods (retroviral vector MetXia [Oxford BioMedica] and encapsulated P450 expressing cells), different cytochrome P450 isoforms (human CYP2B6 versus rat CYP2B1) and different prodrugs (cyclophosphamide [CPA] versus ifosfamide [IFA]) have concluded Phase I/II clinical trial with encouraging results. In the future, P450-based GDEPT can potentially be further enhanced by improved vectors for P450 gene delivery and disease-targeted promoters for focused gene expression at the target site. In addition, there is scope for developing synthetic P450s and their respective prodrugs to improve both enzyme kinetics and the profile of the active moiety.

Estramustine and Vinblastine (EV) Regimen for Advanced Hormone-Refractory Prostate Cancer

The increasing complexity of cancer chemotherapy makes it mandatory that pharmacists be familiar with these highly toxic agents. This column reviews various issues related to the preparation, dispensing, and administration of cancer chemotherapy, both commercially available and investigational.