Pre-clinical and clinical evaluation of estramustine, docetaxel and thalidomide combination in androgen-independent prostate cancer

Evaluation of JQ1 Combined With Docetaxel for the Treatment of Prostate Cancer Cells in 2D- and 3D-Culture Systems

Introduction: Prostate cancer (PCa) is dependent on coupled androgen-androgen receptor (AR) signaling for growth and progression. Significant efforts have been made in this research field, as hormonal therapies have greatly improved the survival of patients with metastatic PCa (mPCa). The drug treatment agent JQ1, which potently abrogates bromodomain 4 (BRD4) localization to the AR target loci and therefore significantly impairs AR-mediated gene transcription, is a potent therapeutic option for patients with advanced PCa. In this study, we aimed to investigate the inhibitory effect of JQ1 combined with docetaxel on PCa cells in vitro for the first time. Furthermore, the 3D spheroid culture system was modeled to more accurately simulate the response of PCa cells to drugs.

Methods: We established and measured 3D LNCaP spheroids in vitro in order to evaluate the susceptibility of 2D- and 3D-cultured LNCaP cells exposed to the same anti-cancer drug.

Results: We demonstrated that JQ1 was an effective drug for promoting cell inhibition after docetaxel treatment in 2D- and 3D- cultured LNCaP cells. Inhibition of 3D cultured formation in the combined treatment group was significantly higher than that in docetaxel or JQ1 alone. Under the same conditions of drug solubility, the drug resistance of 3D spheroids was significantly higher than that of 2D cells. Moreover, dmax and lg volume were suitable parameters for LNCaP cells/spheroid size displaying and evaluating cell viability.

Conclusion: 3D cultured spheroids of PCa are an effective tool for studying PCa drug trials. JQ1 combined with docetaxel may be an effective treatment for advanced PCa. This combination therapy strategy deserves further evaluation in clinical trials.

Angiogenesis and Anti-Angiogenic Treatment in Prostate Cancer: Mechanisms of Action and Molecular Targets

Prostate cancer (PC) is the most common cancer in men and the second leading cause of cancer-related death worldwide. Many therapeutic advances over the last two decades have led to an improvement in the survival of patients with metastatic PC, yet the majority of these patients still succumb to their disease. Antiagiogenic therapies have shown substantial benefits for many types of cancer but only a marginal benefit for PC. Ongoing clinical trials investigate antiangiogenic monotherapies or combination therapies. Despite the important role of angiogenesis in PC, clinical trials in refractory castration-resistant PC (CRPC) have demonstrated increased toxicity with no clinical benefit. A better understanding of the mechanism of angiogenesis may help to understand the failure of trials, possibly leading to the development of new targeted anti-angiogenic therapies in PC. These could include the identification of specific subsets of patients who might benefit from these therapeutic strategies. This paper provides a comprehensive review of the pathways involved in the angiogenesis, the chemotherapeutic agents with antiangiogenic activity, the available studies on anti-angiogenic agents and the potential mechanisms of resistance.

Role of chemotherapy in prostate cancer

Chemotherapy in prostate cancer (PCa) has undergone dramatic landscape changes. While earlier studies utilized varying chemotherapy regimens which were found to be largely palliative in nature and hardly resulted in durable or meaningful responses, docetaxel resulted in the first chemotherapy agent that showed improvement in overall survival in metastatic castration-resistant prostate cancer (mCRPC). However, combination chemotherapy or any agents added to docetaxel have failed to yield incremental benefits. The improvement in overall survival as well as secondary endpoints of prostate-specific antigen (PSA) and time to recurrence when using docetaxel in the metastatic hormone-sensitive state has changed the standard of care for treatment of newly diagnosed de novo metastatic PCa. There are also promising results in locally advanced PCa and high-risk PCa in both the neoadjuvant and adjuvant settings. This review summarizes the historical as well as the more contemporary use of chemotherapeutic agents in PCa in varying states and phases of disease.

Versican is a potential therapeutic target in docetaxel-resistant prostate cancer

In the current study, we investigated a combination of docetaxel and thalidomide (DT therapy) in castration-resistant prostate cancer (CRPC) patients. We identified marker genes that predict the effect of DT therapy. Using an androgen-insensitive PC3 cell line, we established a docetaxel-resistant PC-3 cell line (DR-PC3). In DR-PC3 cells, DT therapy stronger inhibited proliferation/viability than docetaxel alone. Based on gene ontology analysis, we found versican as a selective gene. This result with the findings of cDNA microarray and validated by quantitative RT-PCR. In addition, the effect of DT therapy on cell viability was the same as the effect of docetaxel plus versican siRNA. In other words, silencing of versican can substitute for thalidomide. In the clinical setting, versican expression in prostate biopsy samples (before DT therapy) correlated with PSA reduction after DT therapy (p<0.05). Thus targeting versican is a potential therapeutic strategy in docetaxel-resistant prostate cancer.

Genetic variation: effect on prostate cancer

The crucial role of androgens in the development of prostate cancer is well established. The aim of this review is to examine the role of constitutional (germline) and tumor-specific (somatic) polymorphisms within important regulatory genes of prostate cancer. These include genes encoding enzymes of the androgen biosynthetic pathway, the androgen receptor gene, genes that encode proteins of the signal transduction pathways that may have a role in disease progression and survival, and genes involved in prostate cancer angiogenesis. Characterization of deregulated pathways critical to cancer cell growth have lead to the development of new treatments, including the CYP17 inhibitor abiraterone and clinical trials using novel drugs that are ongoing or recently completed [1]. The pharmacogenetics of the drugs used to treat prostate cancer will also be addressed. This review will define how germline polymorphisms are known affect a multitude of pathways, and therefore phenotypes, in prostate cancer etiology, progression, and treatment.

Mechanism of immunomodulatory drugs' action in the treatment of multiple myeloma

Although immunomodulatory drugs (IMiDs), such as thalidomide, lenalidomide, and pomalidomide, are widely used in the treatment of multiple myeloma (MM), the molecular mechanism of IMiDs' action is largely unknown. In this review, we will summarize recent advances in the application of IMiDs in MM cancer treatment as well as their effects on immunomodulatory activities, anti-angiogenic activities, intervention of cell surface adhesion molecules between myeloma cells and bone marrow stromal cells, anti-inflammatory activities, anti-proliferation, pro-apoptotic effects, cell cycle arrest, and inhibition of cell migration and metastasis. In addition, the potential IMiDs' target protein, IMiDs' target protein's functional role, and the potential molecular mechanisms of IMiDs resistance will be discussed. We wish, by presentation of our naive discussion, that this review article will facilitate further investigation in these fields.

Germline pharmacogenetics of paclitaxel for cancer treatment

Paclitaxel is a highly effective chemotherapeutic agent used in a variety of solid tumors. Some paclitaxel-treated patients experience the intended therapeutic response with manageable side effects, while others have minimal response and/or severe toxicity. This variability in treatment outcome is partially determined by variability in drug exposure (pharmacokinetics) and by patient and tumor sensitivity (pharmacodynamics). Both pharmacokinetics and pharmacodynamics are dictated in part by common variants in the germline genome, known as SNPs. This article reviews the published literature on paclitaxel pharmacogenetics in cancer, focusing primarily on polymorphisms in genes relevant to paclitaxel pharmacokinetics and discusses preliminary work on pharmacodynamic genes and genome-wide association studies.

Separate calculation of DW-MRI in assessing therapeutic effect in liver tumors in rats

AIM: To explore whether the antitumor effect of a vascular disrupting agent (VDA) would be enhanced by combining with an antiangiogenic agent, and whether such synergistic effects can be effectively evaluated with separate calculation of diffusion weighted magnetic resonance imaging (DW-MRI).

METHODS: Thirty-seven rats with implanted liver tumors were randomized into the following three groups: (1) ZD6126, a kind of VDA; (2) ZDTHA, ZD6126 in combination with an antiangiogenic, thalidomide; and (3) control. Morphological DW-MRI were performed and quantified before, 4 h and 2 d after treatment. The apparent diffusion coefficient (ADC) values were calculated separately for low b values (ADC_low), high b values (ADC_high) and all b values (ADC_all). The tissue perfusion contribution, ADC_perf, was calculated as ADC_low-ADC_high. Imaging findings were finally verified by histopathology.

RESULTS: The combination therapy with ZDTHA significantly delayed tumor growth due to synergistic effects by inducing cumulative tumor necrosis. In addition to delaying tumor growth, ZDTHA caused tumor necrosis in an additive manner, which was verified by HE staining. Although both ADC_high and ADC_all in the ZD6126 and ZDTHA groups were significantly higher compared to those in the control group on day 2, the entire tumor ADC_high of ZDTHA was even higher than that of ZD6126, but the significant difference was not observed for ADC_all between ZDTHA and ZD6126. This indicated that the perfusion insensitive ADC_high values calculated from high b value images performed significantly better than ADC_all for the monitoring of tumor necrosis on day 2. The perfusion sensitive ADC_perf derived from ADC_low by excluding high b value effects could better reflect the reduction of blood flow due to the vessel shutdown induced by ZD6126, compared to the ADC_low at 4 h. The ADC_perf could provide valuable perfusion information from DW-MRI data.

CONCLUSION: The separate calculation of ADC is more useful than conventional averaged ADC in evaluating the efficacy of combination therapy with ZD6126 and thalidomide for solid tumors.

Pharmacogenetics, enzyme probes and therapeutic drug monitoring as potential tools for individualizing taxane therapy

The taxanes are a class of chemotherapeutic agents that are widely used in the treatment of various solid tumors. Although taxanes are highly effective in cancer treatment, their use is associated with serious complications attributable to large interindividual variability in pharmacokinetics and a narrow therapeutic window. Unpredictable toxicity occurrence necessitates close patient monitoring while on therapy and adverse effects frequently require decreasing, delaying or even discontinuing taxane treatment. Currently, taxane dosing is based primarily on body surface area, ignoring other factors that are known to dictate variability in pharmacokinetics or outcome. This article discusses three potential strategies for individualizing taxane treatment based on patient information that can be collected before or during care. The clinical implementation of pharmacogenetics, enzyme probes or therapeutic drug monitoring could enable clinicians to personalize taxane treatment to enhance efficacy and/or limit toxicity.

Emerging molecularly targeted therapies in castration refractory prostate cancer

Androgen deprivation therapy (ADT) with medical or surgical castration is the mainstay of therapy in men with metastatic prostate cancer. However, despite initial responses, almost all men eventually develop castration refractory metastatic prostate cancer (CRPC) and die of their disease. Over the last decade, it has been recognized that despite the failure of ADT, most prostate cancers maintain some dependence on androgen and/or androgen receptor (AR) signaling for proliferation. Furthermore, androgen independent molecular pathways have been identified as drivers of continued progression of CRPC. Subsequently, drugs have been developed targeting these pathways, many of which have received regulatory approval. Agents such as abiraterone, enzalutamide, orteronel (TAK-700), and ARN-509 target androgen signaling. Sipuleucel-T, ipilimumab, and tasquinimod augment immune-mediated tumor killing. Agents targeting classic tumorogenesis pathways including vascular endothelial growth factor, hepatocyte growth factor, insulin like growth factor-1, tumor suppressor, and those which regulate apoptosis and cell cycles are currently being developed. This paper aims to focus on emerging molecular pathways underlying progression of CRPC, and the drugs targeting these pathways, which have recently been approved or have reached advanced stages of development in either phase II or phase III clinical trials.

Targeting angiogenesis as a promising modality for the treatment of prostate cancer

Antiangiogenic therapy has been successful for the treatment of solid tumors. Several strategies have been used to target angiogenesis in prostate cancer. These strategies include blocking proangiogenic factors via monoclonal antibodies or small molecule inhibitors targeting downstream signaling effector pathways, or using agents with immune-modulatory effects. This review examines the general concepts of tumor angiogenesis and the key clinical trials that have used these agents and other novel biologics in prostate cancer. Targeting angiogenesis is still a promising treatment strategy in prostate cancer with a rational trial design and combination approach.

Enhanced antitumor efficacy of a vascular disrupting agent combined with an antiangiogenic in a rat liver tumor model evaluated by multiparametric MRI

A key problem in solid tumor therapy is tumor regrowth from a residual viable rim after treatment with a vascular disrupting agent (VDA). As a potential solution, we studied a combined treatment of a VDA and antiangiogenic. This study was approved by the institutional ethical committee for the use and care of laboratory animals. Rats with implanted liver tumors were randomized into four treatment groups: 1) Zd6126 (Zd); 2) Thalidomide (Tha); 3) Zd in combination with Tha (ZdTha); and 4) controls. Multiparametric MRIs were performed and quantified before and after treatment. Circulating endothelial progenitor cells (EPCs) and plasma stromal cell-derived factor-1α (SDF-1α) were monitored. Tumor apoptosis, necrosis, and microvessels were verified by histopathology. A single use of Zd or Tha did not significantly delay tumor growth. The combined ZdTha showed enhanced antitumor efficacy due to synergistic effects; it induced a cumulative tumor apoptosis or necrosis, which resulted in significant delay in tumor growth and reduction in the viable tumor rim; it also reduced tumor vessel permeability; and it improved tumor hemodynamic indexes, most likely via a transient normalization of tumor vasculature induced by Tha. A stepwise linear regression analysis showed that the apparent diffusion coefficient was an independent predictor of tumor growth. We found no significant increases in Zd-induced circulating EPCs or plasma SDF-1α. ZdTha showed improved therapeutic efficacy in solid tumors compared to either agent alone. The therapeutic effects were successfully tracked in vivo with multiparametric MRI.

CYP2C8*3 predicts benefit/risk profile in breast cancer patients receiving neoadjuvant paclitaxel

Paclitaxel is one of the most frequently used chemotherapeutic agents for the treatment of breast cancer patients. Using a candidate gene approach, we hypothesized that polymorphisms in genes relevant to the metabolism and transport of paclitaxel are associated with treatment efficacy and toxicity. Patient and tumor characteristics and treatment outcomes were collected prospectively for breast cancer patients treated with paclitaxel-containing regimens in the neoadjuvant setting. Treatment response was measured before and after each phase of treatment by clinical tumor measurement and categorized according to RECIST criteria, while toxicity data were collected from physician notes. The primary endpoint was achievement of clinical complete response (cCR) and secondary endpoints included clinical response rate (complete response+partial response) and grade 3+ peripheral neuropathy. The genotypes and haplotypes assessed were CYP1B1*3, CYP2C8*3, CYP3A4*1B/CYP3A5*3C, and ABCB1*2. A total of 111 patients were included in this study. Overall, cCR was 30.1% to the paclitaxel component. CYP2C8*3 carriers (23/111, 20.7%) had higher rates of cCR (55% vs. 23%; OR=3.92 [95% CI: 1.46-10.48], corrected p=0.046). In the secondary toxicity analysis, we observed a trend toward greater risk of severe neuropathy (22% vs. 8%; OR=3.13 [95% CI: 0.89-11.01], uncorrected p=0.075) in subjects carrying the CYP2C8*3 variant. Other polymorphisms interrogated were not significantly associated with response or toxicity. Patients carrying CYP2C8*3 are more likely to achieve clinical complete response from neoadjuvant paclitaxel treatment, but may also be at increased risk of experiencing severe peripheral neurotoxicity.

Current and emerging treatment modalities for metastatic castration-resistant prostate cancer

Docetaxel-based therapy is established as the standard first-line chemotherapy in patients with metastatic castration-resistant prostate cancer (mCRPC), based on results from two landmark Phase III studies. However, prognosis remains poor, with a median survival of less than 2 years. There is no standard of care for patients who progress during or after docetaxel treatment, which represents a real unmet medical need. Several small retrospective studies suggest that patients with mCRPC who responded to first-line docetaxel-based therapy are sensitive to re-treatment, but a survival benefit in prospective randomized trials has not been demonstrated. Epithelial-stromal interactions in the tumour microenvironment appear to play a central role in prostate cancer progression and response to therapy. Recent insights into the molecular mechanisms that underpin prostate cancer progression have allowed the identification of potential therapeutic targets. New agents, including angiogenesis inhibitors, hormone therapies, chemotherapies, bone targeting agents, vaccines and immunotherapies are currently undergoing clinical development in advanced prostate cancer using docetaxel as a backbone. Several Phase III studies have now been completed. Sipuleucel-T prolonged survival compared with placebo in asymptomatic or minimally symptomatic patients with mCRPC. Cabazitaxel plus prednisone prolonged survival in patients with mCRPC who progressed during or after docetaxel-based therapy compared with the active agent mitoxantrone, plus prednisone. Multidisciplinary management and optimization of the role and timing of new agents in this evolving treatment continuum will be critical to maximizing patient outcomes. Identification of predictive markers and better gene expression profiling will be critical to tailoring therapies to individual patients and disease states, whereas validated surrogate markers of overall survival will help accelerate drug approval.

Estrogen receptor α and aromatase polymorphisms affect risk, prognosis, and therapeutic outcome in men with castration-resistant prostate cancer treated with docetaxel-based therapy

CONTEXT

Reactive estrogen species cause genotoxicity and interfere with docetaxel-mediated tubulin polymerization resulting in shortened survival in men with castrate-resistant prostate cancer (CRPC).

OBJECTIVE

We hypothesized that polymorphisms in estrogen synthesis and estrogen targets (i.e., CYP19 and ERα) would be linked to interindividual variation in CRPC risk, docetaxel response, and overall survival in men with CRPC.

MATERIALS AND METHODS

Patients with CRPC (n=115) treated with docetaxel, single-agent thalidomide (n=42), or healthy controls (n=289) were genotyped for the CYP19 R264C (rs700519) and the ERα PvuII T>C (rs2234693) and XbaI A>G (rs9340799) polymorphisms.

RESULTS

Patients carrying two copies of ERα polymorphisms had shorter progression-free survival on docetaxel than other patients (median survival difference ≥ 3.1 months; P ≤ 0.036). When the analysis was limited to nonobese patients, the relationship between the ERα XbaI A>G polymorphism and PFS improved (median survival difference = 3.5 months; P = 0.0078). The CYP19 R264C variant was related to the duration of survival after docetaxel in patients who were >70 years old (median survival difference =10.6 months; P=0.041). Both ERα polymorphisms were also associated with increases in CRPC risk [P ≤ 0.032; double variants vs. wild-type odds ratio ≥ 2.6], and the association with the ERα PvuII T>C also improved in those men who were <70 years old (P = 0.0073; odds ratio = 3.0).

CONCLUSIONS

This study demonstrates that estrogen-related genetic variation affects docetaxel clinical response and that this relationship is dependent on age and body-type in men with CRPC. Moreover, this study suggests ERα polymorphisms confer risk of developing prostate cancer, especially in men under 70 years of age.

Novel targeted agents on the horizon for castration-resistant prostate cancer

Androgen deprivation treatment in prostate cancer patients is well established; however, resistance to such treatment manifests itself by progression to castration-resistant prostate cancer (CRPC). Despite significant advances in treatment options for patients with CRPC, their prognosis remains poor. Resistance results from multiple processes that facilitate cancer cell growth and survival. Mechanisms underlying the shift to castrate resistance have been attributed to a complex interplay of clonal selection, reactivation of the androgen receptor axis despite castrate levels of serum testosterone, stress-induced prosurvival genes and cytoprotective chaperone networks and alternative mitogenic growth factor pathways. This article discusses several pathways involved in the development of CRPC, with a particular focus on those mechanisms that have led to the development of new targeted therapies.

Angiogenesis inhibitors in the treatment of prostate cancer

Prostate cancer remains a significant public health problem, with limited therapeutic options in the setting of castrate-resistant metastatic disease. Angiogenesis inhibition is a relatively novel antineoplastic approach, which targets the reliance of tumor growth on the formation of new blood vessels. This strategy has been used successfully in other solid tumor types, with the FDA approval of anti-angiogenic agents in breast, lung, colon, brain, and kidney cancer. The application of anti-angiogenic therapy to prostate cancer is reviewed in this article, with attention to efficacy and toxicity results from several classes of anti-angiogenic agents. Ultimately, the fate of anti-angiogenic agents in prostate cancer rests on the eagerly anticipated results of several key phase III studies.

Angiogenesis as a strategic target for prostate cancer therapy

It is becoming increasingly clear that angiogenesis plays a crucial role in prostate cancer (CaP) survival, progression, and metastasis. Tumor angiogenesis is a hallmark of advanced cancers and an attractive treatment target in multiple solid tumors. By understanding the molecular basis of resistance to androgen withdrawal and chemotherapy in CaP, the rational design of targeted therapeutics is possible. This review summarizes the recent advancements that have improved our understanding of the role of angiogenesis in CaP metastasis and the potential therapeutic efficacy of inhibiting angiogenesis in this disease. Current therapeutic options for patients with metastatic hormone-refractory CaP are very limited. Targeting vasculature is a developing area, which shows promise for the control of late stage and recurrent CaP disease and for overcoming drug resistance. We discuss angiogenesis and its postulated mechanisms and focus on the regulation of angiogenesis in CaP progression and the therapeutic beneficial effects associated with targeting of the CaP vasculature to overcome the resistance to current treatments and CaP recurrence.

VEGF inhibitors and prostate cancer therapy

Prostate cancer remains the most common non-cutaneous malignancy among American men. Since the advent of PSA testing, most men are diagnosed with localized disease, but a proportion of men will be diagnosed with metastatic disease, many will eventually receive chemotherapy with docetaxel and prednisone. However, responses are not durable and all men will ultimately progress on this treatment. As such, continued efforts are geared towards the discovery of new agents and mechanisms of targeting prostate cancer. Angiogenesis has been shown to play an important role in tumorigenesis, proliferation and metastasis in prostate cancer. Here we discuss the major angiogenic signaling pathway involving VEGF in prostate cancer progression and the role of various promising agents that targets this pathway. This includes bevacizumab, thalidomide and its analogues, tyrosine kinase inhibitors sorafenib and AZD2171, and other inhibitors of angiogenic signaling pathways. Results of key clinical trials associated with the use of these agents and future directions are discussed herein.

Angiogenesis inhibitors in the treatment of prostate cancer

IMPORTANCE OF THE FIELD

Prostate carcinoma is the most common non-cutaneous malignancy in U.S. men. The efficacy of docetaxel and prednisone in metastatic castrate-resistant prostate cancer (mCRPC) has been shown to improve overall survival; however, its effect is not durable, highlighting the need for new therapies.

AREAS COVERED IN THIS REVIEW

We will review the development of some of the leading compounds with direct and indirect antiangiogenic activity in prostate cancer including antibodies to VEGF and its receptors, small-molecule inhibitors of downstream signaling, immunomodulatory drugs with antiangiogenic activity, and compounds thought to directly inhibit or destroy vascular endothelial cells.

WHAT THE READER WILL GAIN

The reader will gain a basic understanding of the role of angiogenesis in prostate cancer growth and metastasis. Current and potential targets of angiogenesis and their corresponding drugs under development for prostate cancer are discussed.

TAKE HOME MESSAGE

There are now multiple early-phase clinical trials of antiangiogenic agents alone or in combination in prostate cancer. Several of these agents are now in Phase III development. Combined therapy with two antiangiogenic compounds may improve the activity of either compound alone. Multiple targets in the angiogenesis pathway continue to be elucidated and should remain an active area of investigation for the treatment of prostate cancer.

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.

Signalling pathways in prostate carcinogenesis: potentials for molecular-targeted therapy

Prostate cancer represents a major health issue and its incidence is rising globally. In developed countries, prostate cancer is the most frequently diagnosed cancer and the second most common cause of death from cancer in men. Androgen deprivation reduces tumour activity in approx. 80% of patients with advanced disease, but most tumours relapse within 2 years to an incurable hormone-resistant state. Even for patients with early disease at the time of diagnosis, a proportion of patients will unfortunately develop relapsed disease following radical therapy. Treatment options for patients with hormone-resistant prostate cancer are very limited and, even with toxic therapy, such as docetaxel, the life expectancy is only improved by a median of 2 months. Advances in molecular oncology have identified key signalling pathways that are considered to be driving events in prostate carcinogenesis. The activation of multiple signalling pathways increases further the possibility of cross-talk among 'linear' signalling cascades. Hence signalling networks that may incorporate distinct pathways in prostate cancer, particularly in hormone-resistant disease, are increasingly appreciated in drug development programmes. With the development of potent small-molecule inhibitors capable of specifically suppressing the activities of individual 'linear' cascades, it may be that, by combining these agents as guided by the molecular signature of prostate cancer, a more efficient therapeutic regime may be developed. Therefore the present review focuses on evidence of abnormal signalling in prostate cancer and the potential of these targets in drug development, and incorporates key findings of relevant clinical trials to date.

Anti-angiogenesis approach to genitourinary cancer treatment

Angiogenesis plays a crucial role in the survival, proliferation, and metastatic potential of several tumors, including genitourinary (GU) cancers. Over the last decade, increasing basic science and clinical research have led to the approval of several angiogenesis inhibitors. GU tumors are unique in its pathogenesis whereby specific pathways, such as involvement of the Von Hippel-Lindau gene in clear cell renal cell cancer and aberrant overexpression of vascular endothelial growth factor in prostatic cancers and transitional cell bladder cancers, allow for potential targeting using angiogenesis inhibitors. This review discusses the biologic pathways as well as the rationale for using angiogenesis inhibitors in renal cell, prostate, and transitional cell bladder cancers. This review also focuses on pivotal trials and emerging data on the use of these inhibitors.

Thalidomide suppressed the growth of 4T1 cells into solid tumors in Balb/c mice in a combination therapy with the oncolytic fusogenic HSV-1 OncdSyn

PURPOSE

The anti-tumor properties of thalidomide or in combination with an oncolytic herpes virus (OncdSyn) was investigated in a mouse model of human breast cancer.

METHODS

To determine if thalidomide could act alone, 4T1 cells were injected into Balb/c mice. Tumors were sized, and the mice were fed chow or chow-containing thalidomide. After 4 days the tumor volumes were compared. To determine if thalidomide could act with the virus, tumors of mice were injected with phosphate buffered saline (PBS), or fed thalidomide with injections of PBS, or fed thalidomide with injections of OncdSyn, or received injections of OncdSyn.

RESULTS

Thalidomide alone suppressed tumor growth. The most significant treatment occurred in thalidomide-fed-OncdSyn-injected mice. Compared to PBS controls, there was a significant difference in the number of metastatic nodes in the lungs.

CONCLUSIONS

Thalidomide alone delayed tumor growth, but the combination of thalidomide with OncdSyn appeared to produce the best results.

Prediction of paclitaxel resistance in breast cancer: is CYP1B1*3 a new factor of influence?

This article focuses on the recent findings by Marsh and colleagues, and also discusses recent findings with regards to breast cancer. Taxanes are amongst the most active agents in the treatment of breast cancer. However, many tumors are intrinsically resistant. Therefore, it would be an enormous progress, if factors could be identified that reliably differentiate between taxane-sensitive and -resistant patients. Marsh and colleagues analyzed the CYP1B1*3 (Val432Leu) polymorphism in patients with high-risk stage III and IV breast cancer, who received dose-intense paclitaxel in combination with doxorubicin and cyclophosphamide. They report for the first time that patients with two leucine alleles in codon 432 of CYP1B1 experience a longer progression-free survival compared with patients with the Val/Leu or Val/Val genotypes. If confirmed in independent cohorts CYP1B1*3 may prove to be an important factor that helps to differentiate between paclitaxel-sensitive and resistant breast cancer patients. However, the mechanism behind the association between CYP1B1*3 and prognosis of paclitaxel-treated patients remains unclear. Several studies provide strong evidence that CYP1B1 does not influence tumor progression independently from paclitaxel chemotherapy, and that CYP1B1 itself does not alter paclitaxel resistance. In addition, CYP1B1 mRNA expression does not correlate with paclitaxel sensitivity of primary tumor cells. Although still speculative, a possible explanation is an association between CYP1B1*3 with still unknown factors that, on their part, influence paclitaxel sensitivity. In the future, studies with SNP chips and studies on the transcriptome, proteome and metabolome level should be performed in order to identify signatures differentiating between paclitaxel-sensitive and -resistant patients.

19F NMR in vivo spectroscopy reflects the effectiveness of perfusion-enhancing vascular modifiers for improving gemcitabine chemotherapy

Nuclear magnetic resonance spectroscopy of fluorine-19 ((19)F NMR) has proven useful for evaluating kinetics of fluorinated chemotherapy drugs in tumors in vivo. This work investigated how three perfusion-enhancing vascular modifiers (BQ123, thalidomide, and Botulinum neurotoxin type A [BoNT-A]) would affect the chemotherapeutic efficacy of gemcitabine, a fluorinated drug widely used in human cancer treatment. Murine tumor growth experiments demonstrated that only BoNT-A showed a strong trend to enhance tumor growth inhibition by gemcitabine (1.7 days growth delay, P = 0.052, Student t-test). In accord with these results, (19)F NMR experiments showed that only BoNT-A increased significantly the uptake of gemcitabine in tumors (50% increase, P = 0.0008, Student t-test). Further experiments on gemcitabine kinetics (NMR vs time) and distribution ((19)F MRI) confirmed the uptake-enhancing properties of BoNT-A. The results of this study demonstrate that (19)F NMR can monitor modulation of the pharmacokinetics of fluorinated chemotherapy drugs in tumors. The results also show that (19)F NMR data can give a strong indication of the effectiveness of perfusion-enhancing vascular modifiers for improving gemcitabine chemotherapy in murine tumors. (19)F NMR is a promising tool for preclinical evaluation of such vascular modifiers and may ultimately be used in the clinic to monitor how these modifiers affect chemotherapy.

Association of the CYP1B1*3 allele with survival in patients with prostate cancer receiving docetaxel

Using a single nucleotide polymorphism association study in 52 men with prostate cancer receiving docetaxel, we found that individuals carrying two copies of the CYP1B1*3 polymorphic variant had a poor prognosis after docetaxel-based therapies compared with individuals carrying at least one copy of the CYP1B1*1 allele (30.6 versus 12.8 months; P=0.0004). The association between CYP1B1*3 and response to therapy was not observed in similar subjects receiving non-taxane-based therapy (P=0.18). The systemic clearance of docetaxel was also unrelated to CYP1B1 genotype status (P=0.39), indicating that the association of CYP1B1*3 with clinical response is not due to docetaxel metabolism. To explain these results, we hypothesized that an indirect gene-drug interaction was interfering with the primary mechanism of action of docetaxel, tubulin polymerization. We therefore conducted tubulin polymerization experiments with taxanes in the presence or absence of certain CYP1B1 estrogen metabolites, which are known to bind to nucleophilic sites in proteins and DNA, that revealed the primary estrogen metabolite of CYP1B1, 4-hydroxyestradiol (4-OHE2), when oxidized to estradiol-3,4-quinone strongly inhibits tubulin polymerization. The 4-OHE2 is also formed more readily by the protein encoded by the CYP1B1*3 allele, validating further our data in patients. Furthermore, estradiol-3,4-quinone reacted in vitro with docetaxel to form the 4-OHE2-docetaxel adduct. This pilot study provides evidence that CYP1B1*3 may be an important marker for estimating docetaxel efficacy in patients with prostate cancer. This link is likely associated with CYP1B1*3 genotype-dependent estrogen metabolism.