Exisulind (sulindac sulfone) suppresses growth of human prostate cancer in a nude mouse xenograft model by increasing apoptosis

How do phosphodiesterase-5 inhibitors affect cancer? A focus on glioblastoma multiforme

Since the discovery of phosphodiesterase-5 (PDE5) enzyme overexpression in the central nervous system (CNS) malignancies, investigations have explored the potential capacity of current PDE5 inhibitor drugs for repositioning in the treatment of brain tumors, notably glioblastoma multiforme (GBM). It has now been recognized that these drugs increase brain tumors permeability and enhance standard chemotherapeutics effectiveness. More importantly, studies have highlighted the promising antitumor functions of PDE5 inhibitors, e.g., triggering apoptosis, suppressing tumor cell growth and invasion, and reversing tumor microenvironment (TME) immunosuppression in the brain. However, contradictory reports have suggested a pro-oncogenic role for neuronal cyclic guanosine monophosphate (cGMP), indicating the beneficial function of PDE5 in the brain of GBM patients. Unfortunately, due to the inconsistent preclinical findings, only a few clinical trials are evaluating the therapeutic value of PDE5 inhibitors in GBM treatment. Accordingly, additional studies should be conducted to shed light on the precise effect of PDE5 inhibitors in GBM biology regarding the existing molecular heterogeneities among individuals. Here, we highlighted and discussed the previously investigated mechanisms underlying the impacts of PDE5 inhibitors in cancers, focusing on GBM to provide an overview of current knowledge necessary for future studies.

Phosphodiesterase Type-5 Inhibitor Tadalafil Modulates Steroid Hormones Signaling in a Prostate Cancer Cell Line

Background: The androgen receptor (AR) plays a key role in normal prostate homeostasis and in prostate cancer (PCa) development, while the role of aromatase (Cyp19a1) is still unclear. We evaluated the effects of a treatment with Tadalafil (TAD) on both these proteins. Methods: Androgen-sensitive human PCa cell line (LnCAP) was incubated with/without TAD (10⁻⁶ M) and bicalutamide (BCT) (10⁻⁴ M) to evaluate a potential modulation on cell proliferation, protein and mRNA expression of Cyp19a, AR and estrogen receptor-β (ERβ), respectively. Results: TAD increased early AR nuclear translocation (p < 0.05, after 15 min of exposure), and increased AR transcriptional activity (p < 0.05) and protein expression (p < 0.05) after 24 h. Moreover, after 24 h this treatment upregulated Cyp19a1 and ERβ mRNA (p < 0.05 and p < 0.005 respectively) and led to an increase in protein expression of both after 48 h (p < 0.05). Interestingly, TAD counteracted Cyp19a1 stimulation induced by BCT (p < 0.05) but did not alter the effect induced by BCT on the AR protein expression. Conclusion: We demonstrate for the first time that TAD can significantly modulate AR expression and activity, Cyp19a1 and ERβ expression in PCa cells, suggesting a specific effect of these proteins. In addition, TAD potentiates the antiproliferative activity of BCT, opening a new clinical scenario in the treatment of PCa.

Association between phosphodiesterase type 5 inhibitors and prostate cancer: A systematic review

INTRODUCTION

We aim to assess the effect of phosphodiesterase type 5 inhibitors (PDE5I) on prostate cancer risk as well on biochemical recurrence after radical prostatectomy.

METHOD

We performed a research using the following keywords "Phosphodiesterase type 5 inhibitors" and "Prostate cancer". Only trials examining the effect of PDE5I on prostate cancer risk and recurrence after radical prostatectomy were included.

RESULTS

Seventeen preclinical trials and seven clinical trials were included. Preclinical studies demonstrate a pivotal role for PDE5I as a modulator of apoptosis preventing prostate carcinogenesis. The clinical benefit of PDE5I was not demonstrated. PDE5I use was not associated with decreased prostate cancer diagnosis in two retrospective cohort studies. Biochemical recurrence after radical prostatectomy was not lower (nor higher) in patients taking PDE5I in three retrospective case match studies.

CONCLUSION

Based on this review, a change in our practice regarding pharmacological reeducation after radical prostatectomy is not justified.

Celecoxib inhibits proliferation and survival of chronic myelogeous leukemia (CML) cells via AMPK-dependent regulation of β-catenin and mTORC1/2

CML is effectively treated with tyrosine kinase inhibitors (TKIs). However, the efficacy of these drugs is confined to the chronic phase of the disease and development of resistance to TKIs remains a pressing issue. The anti-inflammatory COX2 inhibitor celecoxib has been utilized as anti-tumour drug due to its anti-proliferative activity. However, its effects in hematological malignancies, in particular CML, have not been investigated yet. Thus, we tested biological effects and mechanisms of action of celecoxib in Philadelphia-positive (Ph⁺) CML and ALL cells.

We show here that celecoxib suppresses the growth of Ph⁺ cell lines by increasing G1-phase and apoptotic cells and reducing S- and G2-phase cells. These effects were independent of COX2 inhibition but required the rapid activation of AMP-activated protein kinase (AMPK) and the consequent inhibition mTORC1 and 2. Treatment with celecoxib also restored GSK3β function and led to down-regulation of β-catenin activity through transcriptional and post-translational mechanisms, two effects likely to contribute to Ph⁺ cell growth suppression by celecoxib.

Celecoxib inhibited colony formation of TKI-resistant Ph⁺ cell lines including those with the T315I BCR-ABL mutation and acted synergistically with imatinib in suppressing colony formation of TKI-sensitive Ph⁺ cell lines. Finally, it suppressed colony formation of CD34⁺ cells from CML patients, while sparing most CD34⁺ progenitors from healthy donors, and induced apoptosis of primary Ph⁺ ALL cells.

Together, these findings indicate that celecoxib may serve as a COX2-independent lead compound to simultaneously target the mTOR and β-catenin pathways, key players in the resistance of CML stem cells to TKIs.

Phosphodiesterase type 5 inhibitors usage and prostate cancer: a match-paired analysis

Background

To treat erectile dysfunction (ED), phosphodiesterase type 5 inhibitors (PDE5i) are commonly used. However, to date, only a few studies exist evaluate a possible effect on the incidence of prostate cancer. One such study completed by the authors’ institution suggested men who use PDE5i for ED may have a lower incidence of prostate cancer. This study was meant to address some of the shortcomings of the former study and further characterize the link between prostate cancer and PDE5i use.

Methods

A retrospective, match-paired analysis was undertaken: 5,717 patients were identified between 2000 and 2011; a 1:2 match pair analysis ultimately identified 394 cases with cancer and 788 controls without cancer. Pairs were matched based on age, ethnicity, and PSA value.

Results

No correlation existed between PDE5i use and prostate cancer [OR 1.02, 95% confidence interval (CI): 0.78–1.35, P=0.8842] or diabetes mellitus and prostate cancer (OR 1.12, 95% CI: 0.84–1.48, P=0.4499). A statistically significant correlation was demonstrated with PSA and prostate cancer (OR 1.48, 95% CI: 1.38–1.58, P<0.0001).

Conclusions

The data suggest that there is essentially no association with PDE5i use and prostate cancer.

Phosphodiesterase type 5 and cancers: progress and challenges

Cancers are an extraordinarily heterogeneous collection of diseases with distinct genetic profiles and biological features that directly influence response patterns to various treatment strategies as well as clinical outcomes. Nevertheless, our growing understanding of cancer cell biology and tumor progression is gradually leading towards rational, tailored medical treatments designed to destroy cancer cells by exploiting the unique cellular pathways that distinguish them from normal healthy counterparts. Recently, inhibition of the activity of phosphodiesterase type 5 (PDE5) is emerging as a promising approach to restore normal intracellular cyclic guanosine monophosphate (cGMP) signalling, and thereby resulting into the activation of various downstream molecules to inhibit proliferation, motility and invasion of certain cancer cells. In this review, we present an overview of the experimental and clinical evidences highlighting the role of PDE5 in the pathogenesis and prevention of various malignancies. Current data are still not sufficient to draw conclusive statements for cancer patient management, but could provide further rational for testing PDE5-targeting drugs as anticancer agents in clinical settings.

Medical treatment of erectile dysfunction: too many medical prescriptions?

Erectile dysfunction (ED) is a worldwide commonly reported condition; epidemiological data showed a prevalence ranging from 2.3 to 53.4% within different population subsets. In this context, the advent of phosphodiesterase type 5 inhibitors (PDE5is) in the second mid of 1990s has deeply changed the treatment scenario of this bothersome condition. Being user-friendly compounds with an excellent overall safety profile, PDE5is emerged as the first-line treatment for ED, thus overcoming topical alprostadil and intracavernous injections (ICIs). However, available data on treatment-utilization patterns and medical prescriptions of PDE5is showed a range of as wide as 22-78% of patients reporting to purchase PDE5is even without a proper medical prescription. Moreover, an increase in the recreational use of PDE5is among young men has been observed in the last decades, with a worrisome diffusion of potential health-risky behaviours associated with this habit. Indeed, treatment of ED should carefully follow internationally based clinical guidelines to avoid inappropriate drug prescriptions, which may eventually expose treated patients to drug-related side effects. Thereof, a careful assessment of the so-called modifiable and reversible ED risk factors along with a patient-tailored screening for potential contraindications to the treatment itself should be performed in every case. Lastly, although conclusive data still lack, the potential association between life-risky PDE5is side effects (i.e. cardiovascular adverse events, melanoma skin cancer and worsening of prostate cancer outcomes) should be carefully taken into account when counselling patients for ED treatment.

PDE5 Overexpression in Well-Differentiated Thyroid Carcinomas Is Associated with Lymph Node Metastasis

Overexpression of PDE5 is observed in certain human cancers, but PDE5 expression in well-differentiated thyroid carcinoma (WDTC) is unknown. We therefore examined PDE5 expression and its relationship with the clinicopathological features of WDTC. Real-time qPCR and Western blotting were performed to analyze the expression of PDE5 mRNA and protein in paired WDTC tumor and adjacent nontumor tissues. Immunohistochemistry was used to analyze the expression of PDE5 in paraffin-embedded tissues obtained from 103 cases of WDTC. Statistical analyses were performed to examine the correlation between PDE5 expression and clinicopathological features. The expression of PDE5 mRNA and protein was upregulated in WDTC lesions compared to their paired noncancerous tissues. The expression of PDE5 was significantly correlated with age (P = 0.032), regional lymph node status (P = 0.004), and the presence of distant metastasis (P = 0.020). High PDE5 expression was more closely associated with lymph node involvement in patients over 45 years (OR = 15.60, P ≤ 0.05). Thus, PDE5 may be a potential biomarker in WDTC, particularly in patients with regional lymph node metastasis, which is associated with disease recurrence, treatment failure, and morbidity. PDE5 expression may also help predict the prognosis and recurrence of WDTC after surgery.

Activation of Protein Kinase G (PKG) Reduces Neointimal Hyperplasia, Inhibits Platelet Aggregation, and Facilitates Re-endothelialization

In spite of its great success in reducing restenosis, drug-eluting stent (DES) has unfavorable aspects such as stent thrombosis and delayed re-endothelialization. We examined the effects of PKG activation by Exisulind on neointimal formation, platelet aggregation, and re-endothelialization. Exisulind significantly reduced VSMCs viability, cell cycle progression, migration, and neointimal hyperplasia after vascular injury in rat carotid arteries. Interestingly, in contrast to the effect on VSMC viability, Exisulind did not reduce the viability of endothelial cells. Increased PKG activity by Exisulind inhibited PDGF-stimulated phenotype change of VSMCs from a contractile to a synthetic form. Conversely, the use of PKG inhibitor or gene transfer of dominant-negative PKG reversed the effects of Exisulind, resulting in the increased viability of VSMCs and neointimal formation. In addition, Exisulind facilitated the differentiation of peripheral blood mononuclear cells to endothelial lineage via PKG pathway, while inhibiting to VSMCs lineage, which was correlated with the enhanced re-endothelialization in vivo. Finally, Exisulind reduced platelet aggregation, which was mediated via PKG activation. This study demonstrated that Exisulind inhibits neointimal formation and platelet aggregation while increasing re-endothelialization via PKG pathway. These findings suggest that Exisulind could be a promising candidate drug of DES for the prevention of restenosis without other complications.

A Second WNT for Old Drugs: Drug Repositioning against WNT-Dependent Cancers

Aberrant WNT signaling underlies cancerous transformation and growth in many tissues, such as the colon, breast, liver, and others. Downregulation of the WNT pathway is a desired mode of development of targeted therapies against these cancers. Despite the urgent need, no WNT signaling-directed drugs currently exist, and only very few candidates have reached early phase clinical trials. Among different strategies to develop WNT-targeting anti-cancer therapies, repositioning of existing drugs previously approved for other diseases is a promising approach. Nonsteroidal anti-inflammatory drugs like aspirin, the anti-leprotic clofazimine, and the anti-trypanosomal suramin are among examples of drugs having recently revealed WNT-targeting activities. In total, 16 human-use drug compounds have been found to be working through the WNT pathway and show promise for their prospective repositioning against various cancers. Advances, hurdles, and prospects of developing these molecules as potential drugs against WNT-dependent cancers, as well as approaches for discovering new ones for repositioning, are the foci of the current review.

Phosphodiesterase 5/protein kinase G signal governs stemness of prostate cancer stem cells through Hippo pathway

Cancer stem cells (CSC) are critical for initiation, metastasis, and relapse of cancers, however, the underlying mechanism governing stemness of CSC remains unknown. Herein, we have investigated the roles of phosphodiesterase 5 (PDE5) in stemness of prostate cancer cells. Both PDE5 and WW domain-containing transcription regulator protein-1 (TAZ), a core effector of Hippo pathway, are highly expressed in the PC3-derived cancer stem cells (PCSC). Either TAZ knockdown or inhibition of PDE5 activity attenuated colony formation, altered expression patterns of stem cell markers, and enhanced cisplatin cytotoxicity, resulting in attenuation of stemness in PCSC. In addition, inhibition of PDE5 activity by its specific inhibitors activates cGMP-dependent protein kinase G (PKG), which in turn induces MST/LATS kinases, resulting in cytosolic degradation of TAZ and activation of Hippo pathway. Accordingly, knockdown of TAZ almost completely abolished PDE5 inhibitor-induced attenuation in stemness in cultured PCSC, whereas knockdown of TAZ not only abolished PDE5 inhibitor-induced attenuation in stemness but also facilitated PDE5 inhibitor-induced trans-differentiation in PCSC xenografts. Together, the present study has uncovered that PDE/cGMP/PKG signal targets to Hippo/TAZ pathway in maintaining stemness of PCSC, and suggested that PDE5 inhibitors in combination with chemotherapeutic agents could effectively prevent initiation, metastasis, and relapse of prostate cancer.

The Association between Phosphodiesterase Type 5 Inhibitors and Prostate Cancer: Results from the REDUCE Study

PURPOSE

Despite routine use of phosphodiesterase type 5 inhibitor to treat erectile dysfunction the role in prostate cancer chemoprevention remains unclear. Only a few studies have explored the link between phosphodiesterase type 5 inhibitor use and prostate cancer. We tested the association between phosphodiesterase type 5 inhibitor and prostate cancer risk in the REDUCE (Reduction by Dutasteride of Prostate Cancer Events) trial.

MATERIALS AND METHODS

REDUCE was a 4-year multicenter study testing the effect of daily dutasteride on prostate cancer risk in men with prostate specific antigen 2.5 to 10.0 ng/ml and negative biopsy who underwent study mandated biopsies at 2 and 4 years. The association of phosphodiesterase type 5 inhibitor with overall prostate cancer risk and disease grade (Gleason 2-6 and 7-10) was examined using adjusted logistic and multinomial regression analysis. Secondary analysis was performed to explore the association between phosphodiesterase type 5 inhibitor and prostate cancer risk in North American men, given the significantly higher use of phosphodiesterase type 5 inhibitor in these subjects.

RESULTS

Phosphodiesterase type 5 inhibitor was not associated with prostate cancer diagnosis (OR 0.90, 95% CI 0.68-1.20, p = 0.476), low grade disease (OR 0.93, 95% CI 0.67-1.27, p = 0.632) or high grade disease (OR 0.85, 95% CI 0.51-1.39, p = 0.508). An inverse trend was seen between phosphodiesterase type 5 inhibitor and prostate cancer diagnosis in North American men but this was not statistically significant (OR 0.67, 95% CI 0.42-1.07, p = 0.091).

CONCLUSIONS

Phosphodiesterase type 5 inhibitor use was not associated with decreased prostate cancer diagnoses on post-hoc analysis of REDUCE. In North American men, who had much higher baseline use of phosphodiesterase type 5 inhibitor, this treatment was associated with an inverse trend of prostate cancer diagnosis that approached but did not reach statistical significance.

The Role of PDE5 Inhibitors and the NO/cGMP Pathway in Cancer

INTRODUCTION

Phosphodiesterase 5 (PDE5) inhibitors (PDE5i) have been used clinically for the treatment of erectile dysfunction, acting on the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) signaling pathway. Simultaneously, researchers have elucidated the roles that this pathway plays in the regulation of cell proliferation, tumor development, and progression. As a result, our knowledge of PDE5i and cancer biology has expanded and provides an integration that holds great promise for some, but concern for others.

AIM

This review evaluates the role of PDE5i and the NO/cGMP signaling pathway in the pathogenesis and prevention of various malignancies.

METHODS

A literature review was performed with regard to the role of NO/cGMP pathway in tumor formation and prevention in preclinical and clinical studies. Studies that utilized PDE5i to further explore the involvement of this pathway also were included.

MAIN OUTCOME MEASURES

To evaluate whether PDE5i provide a potential benefit for treating and/or preventing malignancies; or if they create potential harm leading to the development of these malignancies.

RESULTS

The best available data suggest that the interactions between PDE5i and cancer are tumor- and tissue-specific. Currently, the effect of PDE5i use on melanoma development is being debated. Further clinical controversy lies in PDE5i use for penile rehabilitation after nerve-sparing prostate cancer surgery. Preclinical studies suggest that PDE5 inhibition could lead to a decreased risk of developing colorectal and breast cancer, leukemia, and myeloma. PDE5i also may provide an additional antitumor immune response. Finally, researchers have demonstrated a synergistic effect from combining PDE5i with current chemotherapeutic regimens.

CONCLUSION

Currently, there are inadequate data to make any conclusive statements regarding the role of PDE5i in cancer pathogenesis and how to alter clinical management. In order to create appropriate clinical guidelines, further experimental and clinical evidence is required.

Hitting the Bull's-Eye in Metastatic Cancers-NSAIDs Elevate ROS in Mitochondria, Inducing Malignant Cell Death

Tumor metastases that impede the function of vital organs are a major cause of cancer related mortality. Mitochondrial oxidative stress induced by hypoxia, low nutrient levels, or other stresses, such as genotoxic events, act as key drivers of the malignant changes in primary tumors to enhance their progression to metastasis. Emerging evidence now indicates that mitochondrial modifications and mutations resulting from oxidative stress, and leading to OxPhos stimulation and/or enhanced reactive oxygen species (ROS) production, are essential for promoting and sustaining the highly metastatic phenotype. Moreover, the modified mitochondria in emerging or existing metastatic cancer cells, by their irreversible differences, provide opportunities for selectively targeting their mitochondrial functions with a one-two punch. The first blow would block their anti-oxidative defense, followed by the knockout blow—promoting production of excess ROS, capitulating the terminal stage—activation of the mitochondrial permeability transition pore (mPTP), specifically killing metastatic cancer cells or their precursors. This review links a wide area of research relevant to cellular mechanisms that affect mitochondria activity as a major source of ROS production driving the pro-oxidative state in metastatic cancer cells. Each of the important aspects affecting mitochondrial function are discussed including: hypoxia, HIFs and PGC1 induced metabolic changes, increased ROS production to induce a more pro-oxidative state with reduced antioxidant defenses. It then focuses on how the mitochondria, as a major source of ROS in metastatic cancer cells driving the pro-oxidative state of malignancy enables targeting drugs affecting many of these altered processes and why the NSAIDs are an excellent example of mitochondria-targeted agents that provide a one-two knockout activating the mPTP and their efficacy as selective anticancer metastasis drugs.

PDE5 inhibitors as therapeutics for heart disease, diabetes and cancer

The phosphodiesterase 5 (PDE5) inhibitors, including sildenafil (Viagra™), vardenafil (Levitra™), and tadalafil (Cialis™) have been developed for treatment of erectile dysfunction. Moreover, sildenafil and tadalafil are used for the management of pulmonary arterial hypertension in patients. Since our first report showing the cardioprotective effect of sildenafil in 2002, there has been tremendous growth of preclinical and clinical studies on the use of PDE5 inhibitors for cardiovascular diseases and cancer. Numerous animal studies have demonstrated that PDE5 inhibitors have powerful protective effect against myocardial ischemia/reperfusion (I/R) injury, doxorubicin cardiotoxicity, ischemic and diabetic cardiomyopathy, cardiac hypertrophy, Duchenne muscular dystrophy and the improvement of stem cell efficacy for myocardial repair. Mechanistically, PDE5 inhibitors protect the heart against I/R injury through increased expression of nitric oxide synthases, activation of protein kinase G (PKG), PKG-dependent hydrogen sulfide generation, and phosphorylation of glycogen synthase kinase-3β - a master switch immediately proximal to mitochondrial permeability transition pore and the end effector of cardioprotection. In addition, PDE5 inhibitors enhance the sensitivity of certain types of cancer to standard chemotherapeutic drugs, including doxorubicin. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular and anti-cancer benefits. Despite mixed results of these clinical trials, there is a continuing strong interest by basic scientists and clinical investigators in exploring their new clinical uses. It is our hope that future new mechanistic investigations and carefully designed clinical trials would help in reaping additional benefits of PDE5 inhibitors for cardiovascular disease and cancer in patients.

Exisulind in the treatment of prostate cancer

Prostate cancer represents the most common noncutaneous malignancy in men. With the widespread use of prostate-specific antigen screening, as many as one in six men in the USA will be diagnosed with prostate cancer. Significant healthcare resources are currently devoted to the treatment of this disease, specifically aimed at improving the side effects of successful treatment. Surgery or radiation therapy provides the best chance of cure from this disease. However, as many as 50% of patients treated with curative intent will develop a recurrence 10-15 years following treatment. Hormonal ablation via medical or surgical castration provides disease control, but is associated with significant hot flushes, loss of libido and impotence. Selective, apoptotic antineoplastic drugs, such as exisulind, may provide an alternative method to treating or preventing prostate cancer. This drug profile reviews the evidence for the use of exisulind in the treatment of prostate cancer.

The strategies to control prostate cancer by chemoprevention approaches

Prostate cancer (PCA) is the most commonly diagnosed cancer in men in the United States with growing worldwide incidence. Despite intensive investment in improving early detection, PCA often escapes timely detection and mortality remains high; this malignancy being the second highest cancer-associated mortality in American men. Collectively, health care costs of PCA results in an immense financial burden that is only expected to grow. Additionally, even in cases of successful treatment, PCA is associated with long-term and pervasive effects on patients. A proactive alternative to treat PCA is to prevent its occurrence and progression prior to symptomatic malignancy. This may serve to address the issue of burgeoning healthcare costs and increasing number of sufferers. One potential regimen in service of this alternative is PCA chemoprevention. Here, chemical compounds with cancer preventive efficacy are identified on the basis of their potential in a host of categories: their historical medicinal use, correlation with reduced risk in population studies, non-toxicity, their unique chemical properties, or their role in biological systems. PCA chemopreventive agents are drawn from multiple broad classes of chemicals, themselves further subdivided based on source or potential effect, with most derived from natural products. Many such compounds have shown efficacy, varying from inhibiting deregulated PCA cell signaling, proliferation, epithelial to mesenchymal transition (EMT), invasion, metastasis, tumor growth and angiogenesis and inducing apoptosis. Overall, these chemopreventive agents show great promise in PCA pre-clinical models, though additional work remains to be done in effectively translating these findings into clinical use.

cGMP-dependent protein kinase Iβ interacts with p44/WDR77 to regulate androgen receptor-driven gene expression

The androgen receptor (AR) pathway plays critical roles in controlling differentiation and proliferation of prostate epithelial cells. We previously identified a novel AR cofactor, p44/WDR77, which specifically enhances AR transcriptional activity in the prostate gland and prostate cancer. To further elucidate p44/WDR77's role in the AR signaling pathway, we conducted a yeast two-hybrid screening and identified cGMP-dependent protein kinase (PKG) as a p44/WDR77-interacting protein. Further investigation by lusiferase assay and kinase assay demonstrated that PKG-Iβ physically interacted with and phosphorylated both p44 and AR and enhanced AR transactivity in synergy with p44 in an androgen- and cGMP-dependent manner. Furthermore, PKG1β expression promoted p44/WDR77 nuclear translocation and inhibited prostate cancer cell growth via G1 cell cycle arrest. Our findings characterize PKG as a novel regulator of AR-mediated transcription by enhancing AR cofactor p44/WDR77's function, which provide a novel mechanism for the growth regulation of prostate cancer cells by the androgen signaling.

Nitric oxide donor exisulind is an effective inhibitor of murine photocarcinogenesis

NO-releasing nonsteroidal anti-inflammatory drugs (NO-NSAIDs) have been shown to have anti-inflammatory, antiproliferative and apoptosis-inducing effects in tumor cells. Herein, we have investigated the effects of NO-exisulind on the growth of UVB-induced skin tumor development in a murine model. We found that the topical treatment with NO-exisulind significantly reduced UVB-induced tumors in SKH-1 hairless mice. The tumors/tumor bearing mouse, the number of tumors/mouse and tumor volume/mouse decreased significantly (P < 0.05) as compared with vehicle-treated and UVB-irradiated positive controls. Consistently, NO-exisulind-treated animals showed reduced expression of proliferation markers, such as PCNA and cyclin D1. These mice also manifested increased expression of proapoptotic Bax and decreased expression of antiapoptotic Bcl2 with an increase in the number of TUNEL-positive cells in tumors. We also investigated whether NO-exisulind-treated tumors are less invasive and progress less efficiently from benign to malignant carcinomas. For this, tumors were stained for various epithelial-mesenchymal transition (EMT) markers. NO-exisulind decreased the expression of mesenchymal markers, such as Fibronectin, N-cadherin, SNAI, Slug and Twist and enhanced the epithelial marker E-cadherin. Similarly, UVB-induced phosphorylation of Erk1/2 and p38 was decreased in NO-exisulind-treated animals. These data suggest that NO-exisulind reduces tumor growth and inhibits tumor progression by blocking proliferation, inducing apoptosis and reducing EMT.

Increased androgen receptor transcription: a cause of castration-resistant prostate cancer and a possible therapeutic target

Few effective therapies exist for the treatment of castration-resistant prostate cancer (CRPC). Recent evidence suggests that CRPC may be caused by augmented androgen/androgen receptor (AR) signaling, generally involving AR overexpression. Aberrant androgen/AR signaling associated with AR overexpression also plays a key role in prostate carcinogenesis. Although AR overexpression could be attributed to gene amplification, only 10-20% of CRPCs exhibit AR gene amplification, and aberrant AR expression in the remaining instances of CRPC is thought to be attributed to transcriptional, translational, and post-translational mechanisms. Overexpression of AR at the protein level, as well as the mRNA level, has been found in CRPC, suggesting a key role for transcriptional regulation of AR expression. Since the analysis of the AR promoter region in the 1990s, several transcription factors have been reported to regulate AR transcription. In this review, we discuss the molecules involved in the control of AR gene expression, with emphasis on its transcriptional control by transcription factors in prostate cancer. We also consider the therapeutic potential of targeting AR expression.

Inhibition of PDE5 by sulindac sulfide selectively induces apoptosis and attenuates oncogenic Wnt/β-catenin-mediated transcription in human breast tumor cells

Nonsteroidal anti-inflammatory drugs (NSAID) such as sulindac sulfide (SS) display promising antineoplastic properties, but toxicities resulting from COX inhibition limit their clinical use. Although COX inhibition is responsible for the anti-inflammatory activity of SS, recent studies suggest that phosphodiesterase (PDE) 5 inhibition and activation of cyclic guanosine monophosphate (cGMP) signaling are closely associated with its ability to induce apoptosis of tumor cells. However, the underlying mechanisms responsible for apoptosis induction, factors that influence sensitivity of tumor cells to SS, and the importance of PDE5 for breast tumor cell growth have not been established. Here we show that SS can induce apoptosis of breast tumor cells, which predominantly rely on PDE5 for cGMP hydrolysis but not normal mammary epithelial cells, which rely on PDE isozymes other than PDE5 for cGMP hydrolysis. Inhibition of PDE5 and activation of protein kinase G (PKG) by SS was associated with increased β-catenin phosphorylation, decreased β-catenin mRNA and protein levels, reduced β-catenin nuclear localization, decreased T-cell factor/lymphoid enhancer factor (Tcf/Lef) promoter activity, and decreased expression of Wnt/β-catenin-regulated proteins. Suppression of PDE5 with siRNA or known PDE5 inhibitors was sufficient to selectively induce apoptosis and attenuate β-catenin-mediated transcription in breast tumor cells with minimal effects on normal mammary epithelial cells. These findings provide evidence that SS induces apoptosis of breast tumor cells through a mechanism involving inhibition of PDE5 and attenuation of oncogenic Wnt/β-catenin-mediated transcription. We conclude that PDE5 represents a novel molecular target for the discovery of safer and more efficacious drugs for breast cancer chemoprevention.

Mechanisms of the anti-cancer and anti-inflammatory actions of vitamin D

Calcitriol, the hormonally active form of vitamin D, is being evaluated in clinical trials as an anti-cancer agent. Calcitriol exerts multiple anti-proliferative, pro-apoptotic, and pro-differentiating actions on various malignant cells and retards tumor growth in animal models of cancer. Calcitriol also exhibits several anti-inflammatory effects including suppression of prostaglandin (PG) action, inhibition of p38 stress kinase signaling, and the subsequent production of pro-inflammatory cytokines and inhibition of NF-κB signaling. Calcitriol also decreases the expression of aromatase, the enzyme that catalyzes estrogen synthesis in breast cancer, both by a direct transcriptional repression and indirectly by reducing PGs, which are major stimulators of aromatase transcription. Other important effects include the suppression of tumor angiogenesis, invasion, and metastasis. These calcitriol actions provide a basis for its potential use in cancer therapy and chemoprevention. We summarize the status of trials involving calcitriol and its analogs, used alone or in combination with known anti-cancer agents.

Sildenafil increases chemotherapeutic efficacy of doxorubicin in prostate cancer and ameliorates cardiac dysfunction

We have shown that the potent phosphodiesterase-5 (PDE-5) inhibitor sildenafil (Viagra) induces a powerful effect on reduction of infarct size following ischemia/reperfusion injury and improvement of left ventricular dysfunction in the failing heart after myocardial infarction or doxorubicin (DOX) treatment. In the present study, we further investigated the potential effects of sildenafil on improving antitumor efficacy of DOX in prostate cancer. Cotreatment with sildenafil enhanced DOX-induced apoptosis in PC-3 and DU145 prostate cancer cells, which was mediated by enhanced generation of reactive oxygen species, up-regulation of caspase-3 and caspase-9 activities, reduced expression of Bcl-xL, and phosphorylation of Bad. Overexpression of Bcl-xL or dominant negative caspase 9 attenuated the synergistic effect of sildenafil and DOX on prostate cancer cell killing. Furthermore, treatment with sildenafil and DOX in mice bearing prostate tumor xenografts resulted in significant inhibition of tumor growth. The reduced tumor size was associated with amplified apoptotic cell death and increased expression of activated caspase 3. Doppler echocardiography showed that sildenafil treatment ameliorated DOX-induced left ventricular dysfunction. In conclusion, these results provide provocative evidence that sildenafil is both a powerful sensitizer of DOX-induced killing of prostate cancer while providing concurrent cardioprotective benefit.

Comparative evaluation of three 64Cu-labeled E. coli heat-stable enterotoxin analogues for PET imaging of colorectal cancer

Analogues of the E. coli heat-stable enterotoxin (STh) are currently under study as both imaging and therapeutic agents for colorectal cancer. Studies have shown that the guanylate cyclase C (GC-C) receptor is commonly expressed in colorectal cancers. It has also been shown that STh peptides inhibit the growth of tumor cells expressing GC-C. The ability to determine GC-C status of tumor tissue using in vivo molecular imaging techniques would provide a useful tool for the optimization of GC-C-targeted therapeutics. In this work, we have compared receptor binding affinities, internalization/efflux rates, and in vivo biodistribution patterns of an STh analogue linked to N-terminal DOTA, TETA, and NOTA chelating moieties and radiolabeled with Cu-64. The peptide F(19)-STh(2-19) was N-terminally labeled with three different chelating groups via NHS ester activation and characterized by RP-HPLC, ESI-MS, and GC-C receptor binding assays. The purified conjugates were radiolabeled with Cu-64 and used for in vitro internalization/efflux, in vivo biodistribution, and in vivo PET imaging studies. In vivo experiments were carried out using SCID mice bearing T84 human colorectal cancer tumor xenografts. Incorporation of DOTA-, TETA-, and NOTA-chelators at the N-terminus of the peptide F(19)-STh(2-19) resulted in IC(50)s between 1.2 and 3.2 nM. In vivo, tumor localization was similar for all three compounds, with 1.2-1.3%ID/g at 1 h pi and 0.58-0.83%ID/g at 4 h pi. The principal difference between the three compounds related to uptake in nontarget tissues, principally kidney and liver. At 1 h pi, (64)Cu-NOTA-F(19)-STh(2-19) demonstrated significantly (p < 0.05) lower uptake in liver than (64)Cu-DOTA-F(19)-STh(2-19) (0.36 +/- 0.13 vs 1.21 +/- 0.65%ID/g) and significantly (p < 0.05) lower uptake in kidney than (64)Cu-TETA-F(19)-STh(2-19) (3.67 +/- 1.60 vs 11.36 +/- 2.85%ID/g). Use of the NOTA chelator for coordination of Cu-64 in the context of E. coli heat-stable enterotoxin analogues results in higher tumor/nontarget tissue ratios at 1 h pi than either DOTA or TETA macrocycles. Heat-stable enterotoxin-based radiopharmaceuticals such as these provide a means of noninvasively determining GC-C receptor status in colorectal cancers by PET.

Suppression of Wnt/beta-catenin signaling inhibits prostate cancer cell proliferation

Although mounting evidence has demonstrated an important role of Wnt/beta-catenin signaling in the development and progression of cancer, the therapeutic potential of small molecules that target this pathway for prostate cancer remains largely unknown. We reported herein that the highly invasive androgen-independent PC-3 and DU145 human prostate cancer cells exhibited higher levels of Wnt/beta-catenin signaling than the androgen-dependent LNCaP prostate cancer cells and non-cancerous PZ-HPV-7 and PWR-1E prostate cells, and that exogenous Wnt3A treatment exaggerated the difference of the Wnt/beta-catenin signaling levels among these prostate cells. Furthermore, we demonstrated that the non-steroidal anti-inflammatory drug, sulindac sulfide, the cyclooxygenase-2 (COX-2) selective inhibitor, celecoxib, and the nitric oxide-donating aspirin derivative, NO-ASA, blocked Wnt/beta-catenin signaling in PC-3 and DU145 cells. These effects occurred at concentrations comparable to those required to inhibit cell proliferation, indicating that the inhibitory effect of these drugs on prostate cancer cell proliferation may involve the suppression of Wnt/beta-catenin signaling. Finally, we showed that a novel small molecule inhibitor of Wnt/beta-catenin signaling, PKF118- 310, inhibited Wnt/beta-catenin signaling and proliferation in prostate cancer cells within the same concentration range. Together, these results suggest that small molecules that inhibit Wnt/beta-catenin signaling have therapeutic potential for the prevention or treatment of prostate cancer.

Apoptosis: a relevant tool for anticancer therapy

Apoptosis is a form of cell death that permits the removal of damaged, senescent or unwanted cells in multicellular organisms, without damage to the cellular microenvironment. Defective apoptosis represents a major causative factor in the development and progression of cancer. The majority of chemotherapeutic agents, as well as radiation, utilize the apoptotic pathway to induce cancer cell death. Resistance to standard chemotherapeutic strategies also seems to be due to alterations in the apoptotic pathway of cancer cells. Recent knowledge on apoptosis has provided the basis for novel targeted therapies that exploit apoptosis to treat cancer. These new target include those acting in the extrinsic/intrinsic pathway, proteins that control the apoptosis machinery such as the p53 and proteosome pathway. Most of these forms of therapy are still in preclinical development because of their low specifity and susceptibility to drug resistance, but several of them have shown promising results. In particular, this review specifically aims at providing an update of certain molecular players that are already in use in order to target apoptosis (such as bortezomib) or which are still being clinically evaluated (such ONYX-015, survivin and exisulind/aptosyn) or which, following preclinical studies, might have the necessary requirements for becoming part of the anticancer drug programs (such as TRAIL/Apo2L, apoptin/VP3).

Docetaxel and exisulind in previously treated non-small cell lung cancer (NSCLC) patients: a multicenter, phase II clinical trial

PURPOSE

This multicenter, phase II clinical trial was conducted to evaluate the activity of the combination of docetaxel and exisulind in advanced non-small cell lung cancer (NSCLC) patients who failed a prior platinum-containing regimen.

PATIENTS AND METHODS

Patients with measurable disease and adequate organ function received exisulind (250 mg) given orally, twice daily, and docetaxel (36 mg/m) administered intravenously on days 1, 8, and 15 of a 4-week cycle for up to six cycles. In the absence of disease progression or intolerable side effects, patients continued taking 250 mg of exisulind orally, twice daily.

RESULTS

Thirty-three patients (median age 60 years; range 34-77; median performance status 1) were enrolled. There were no objective responses documented. Sixteen patients [48%, 95% confidence interval (CI): 31%-66%] had stable disease after 8 weeks of treatment. Median progression-free survival (PFS) was 2.1 months (95% CI: 1.5-3.2 months); median overall survival time was 8.0 months (range 0.2-25.9 months). Toxicity was moderate, with dose adjustment for adverse event/toxicity required for docetaxel or exisulind in 13 (39.3%) patients. Grade 3/4 lymphopenia, neutropenia, and anemia occurred in 48.5%, 12.1%, and 9.1% of patients, respectively. Grade 3 or greater toxicity was seen in 12.1%, 6.1%, and 3% of patients for nausea/vomiting, dyspnea, and abdominal pain, respectively.

CONCLUSIONS

Treatment with exisulind and weekly docetaxel was not active in NSCLC patients who failed a prior platinum-containing regimen. Further study of this combination does not seem warranted.

A comparison of the effectiveness of selected non-steroidal anti-inflammatory drugs and their derivatives against cancer cells in vitro

PURPOSE

Previously, we reported in vitro observations suggesting that ibuprofen is an effective non-prescription non-steroidal anti-inflammatory drug (NSAID) to reduce the survival of human prostate cancer cells (Andrews et al. in Cancer Chemother Pharmacol 502:77-284, 2002), and that this observed effectiveness is mediated by an up-regulation of the p75 NTR tumor suppressor (Khwaja et al. in Cancer Res 646:207-6213, 2004). However, other NSAIDs and their derivatives have received significant attention with regard to their anti-cancer effectiveness and have been selected for clinical trials to treat a variety of human cancers. In this investigation, we compared celecoxib, sulindac sulfone, nitric oxide linked NSAIDs, and R-flurbiprofen with ibuprofen in their ability to inhibit the growth of a variety of human cancer cells lines including cells lines with multi-drug resistance. We also evaluated whether, like ibuprofen, an up-regulation of p75 NTR is a molecular mechanism that mediates the anti-growth effectiveness of these drugs.

MATERIALS AND METHODS

Selected dosages for each drug were evaluated for their ability to reduce the growth (MTT analysis) and induce apoptosis (Hoechst staining) of a variety of different cancer cell lines, including an ovarian cell line expressing multidrug resistance-1 glycoprotein (MDR-1). The drugs were then analyzed using immunoblot, RT-PCR and siRNA to study the role of p75 NTR in their anti-growth effectiveness.

RESULTS

Our study revealed consistency in the drug dosages that inhibit the survival of different human cancer cell lines. While NO-linked aspirin and celecoxib were most effective in decreasing cell growth and inducing apoptosis at the lowest dosages, R-flurbiprofen and ibuprofen were most effective at clinically relevant dosages. A multidrug resistant ovarian cell line is more resistant to growth inhibition by the drugs tested than its non-drug resistant parental counterpart. There was no correlation between the expression of cyclooxygenase-2 (COX-2) and the ability of the drugs to reduce cancer cell survival. All the drugs tested induced an up-regulation in p75 NTR tumor suppressor gene expression in concert with their observed growth inhibiting ability. Inhibition of p75 NTR expression with siRNA reduced the cell growth inhibiting effects of all the drugs tested.

CONCLUSIONS

The method of chemotherapy (i.e., intravascular, intrathecal, oral) might dictate the choice of NSAID/NSAID derivative used to treat/prevent a given type of cancer. Also, the p75 NTR tumor suppressor appears to be a common molecular mechanism that mediates the growth inhibiting effectiveness of these drugs.

Celecoxib induces apoptosis in COX-2 deficient human gastric cancer cells through Akt/GSK3beta/NAG-1 pathway

In this study, we analyzed the mechanisms of the apoptotic effects of celecoxib on COX-2 deficient gastric cancer cell line, MGC-803. We found celecoxib treatment induced caspase-dependent apoptosis in MGC-803 cells. Celecoxib inhibited Ser473 Akt and Ser9 GSK3beta phosphorylation and induced upregulation of nonsteroidal anti-inflammatory drugs-activated gene-1 (NAG-1) expression. The effects of celecoxib on NAG-1 expression were abolished by pretreatment with GSK3beta inhibitor, SB216763. Furthermore, GSK3beta gene silencing by siRNA inhibited the celecoxib-induced NAG-1 expression. Our study demonstrated that Akt/GSK3beta/NAG-1 signal pathway may represent as the major mechanism of the COX-2-independent effects of celecoxib on gastric cancer cells.

Alpha-tocopheryl succinate sensitizes human colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (also known as exisulind) and its chemical derivatives are promising anticancer agents capable of inducing apoptosis in a variety of malignant cell types with minimal toxicity to normal cells. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to sensitize colon cancer cells to exisulind-induced apoptosis. We found that sub-apoptotic doses of TOS greatly enhanced exisulind-induced growth suppression and apoptosis in the HCT116, LoVo and SNU-C4 human colon cancer cell lines. Our results revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8, -9 and -3. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor), z-IETD-FMK (a caspase-8 inhibitor) or z-LEHD-FMK (a caspase-9 inhibitor) blocked TOS and exisulind cotreatment-induced PARP cleavage and apoptosis. Furthermore, TOS/exisulind cotreatment induced JNK phosphorylation, while pretreatment with SP600151 (a JNK inhibitor) partially blocked cotreatment-induced caspase-dependent PARP cleavage and apoptosis. Taken together, these findings indicate that TOS sensitizes human colon cancer cells to exisulind-induced apoptosis. Apoptotic synergy induced by exisulind plus TOS seems likely to be mediated through a mechanism involving activation of caspases and JNK.

An update on chemoprevention strategies in prostate cancer for 2006

PURPOSE OF REVIEW

An increasing volume of research has been directed at the prevention of prostate cancer. This review proposes to summarize the large trials, novel approaches and molecular mechanisms of effect published in 2004 and 2005.

RECENT FINDINGS

The impact of the Prostate Cancer Prevention Trial continues and subsequent articles have addressed the increase of high-grade prostate cancers detected in the finasteride arm of the trial, as well as the potential costs and benefits of extrapolating the findings to a public health campaign. Studies of risk have been published warning of excessive vitamin E and cyclooxygenase-2 inhibitor use in chemoprevention. Growing evidence supports the concept of chemopreventative agent combinations and further data on the roles of selenium, lycopene, soy, green tea, anti-inflammatories and statins in prostate-cancer prevention are presented.

SUMMARY

Level one evidence exists for the preventative effects of finasteride in prostate cancer. The evidence for other agents is less conclusive but a number of large-scale, appropriately designed trials will hopefully address some of the relevant issues in prostate-cancer prevention over the next decade.

Phase II Evaluation of Docetaxel Plus Exisulind in Patients With Androgen Independent Prostate Carcinoma

OBJECTIVES

In this phase II study, the combination of docetaxel and exisulind (a GMP phosphodiesterase inhibitor) was given to patients with metastatic androgen independent prostate cancer (AIPC) to establish efficacy, assess toxicity, and determine pharmacokinetics of docetaxel administered alone and in combination with exisulind.

METHODS

Fourteen patients with metastatic AIPC were registered to receive weekly docetaxel for 4 weeks, followed by 2 weeks of rest; repeated up to a maximum of 6 cycles. Exisulind 250 mg was given orally twice a day starting on day 8 of the study and taken continuously.

RESULTS

All patients were evaluable for toxicity, response and survival. Grade 3 reversible toxicities included: fatigue, nausea, diarrhea, abdominal pain, rash, syncope, pulmonary edema, deep vein thrombosis, congestive heart failure, and elevations in transaminases, requiring therapy delays and/or dose reductions, or removal from therapy. Only 3 out of 14 patients (21.4%) had a 50% decline in prostate specific antigen (PSA) level that lasted > or =4 weeks; 1 out of 14 patients (7%) had a lymph node response. Median survival was 17.28 months. Docetaxel pharmacokinetics for 11 patients demonstrated mean +/- SD clearance values that were similar during week 1 and week 3 when exisulind had been added.

CONCLUSIONS

: Overall, our trial indicated that the toxicity profile and efficacy of this regimen is unlikely to be substantially better than single agent docetaxel.

Sulindac Sulfide and Exisulind Inhibit Expression of the Estrogen and Progesterone Receptors in Human Breast Cancer Cells

In previous studies, we found that sulindac sulfide and exisulind (sulindac sulfone, Aptosyn) cause growth inhibition, arrest cells in the G1 phase of the cell cycle, and induce apoptosis in human breast cancer cell lines. These effects were associated with decreased expression of cyclin D1. The present study focuses on the effects of sulindac sulfide and exisulind on hormone signaling components in breast cancer cells. We found that estrogen receptor (ER)-positive and progesterone receptor (PR)-positive T47D breast cancer cells were somewhat more sensitive to growth inhibition by sulindac sulfide or exisulind than ER-negative PR-negative MB-MDA-468 breast cancer cells. Further studies indicated that sulindac sulfide and exisulind caused marked down-regulation of expression of the ER and PR-A and PR-B in T47D cells. However, neither compound caused a major change in expression of the retinoic acid receptor alpha (RARalpha), RARbeta, or RARalpha in T47D cells. Sulindac sulfide and exisulind also caused a decrease in expression of the ER in estrogen-responsive MCF-7 breast cancer cells. Both compounds also markedly inhibited estrogen-stimulated activation of an estrogen-responsive promoter in transient transfection reporter assays. Treatment of T47D cells with specific protein kinase G (PKG) activators did not cause a decrease in ER or PR expression. Therefore, although sulindac sulfide and exisulind can cause activation of PKG, the inhibitory effects of these two compounds on ER and PR expression does not seem to be mediated by PKG. Our findings suggest that the growth inhibition by sulindac sulfide and exisulind in ER-positive and PR-positive human breast cancer cells may be mediated, in part, by inhibition of ER and PR signaling. Thus, these and related compounds may provide a novel approach to the prevention and treatment of human breast cancers, especially those that are ER positive.

Tumour plasticity and extravascular circulation in ECV304 human bladder carcinoma cells

BACKGROUND

The concepts of vasculogenic mimicry and mosaic vessels have been proposed as novel modes of tumour neovascularisation. However, the presence and significance of these types of neovascularisation remain unclear.

MATERIALS AND METHODS

ECV304 human bladder carcinoma cells were used to determine how tumour cells take part in tumour neovascularisation.

RESULTS

Subcutaneous ECV304 xenografts in mice showed various vessel types, including angiogenic vessels, tumour cell-related vessels and extracellular matrix networks. A tracer experiment demonstrated perfusion of beads in these structures. ECV304 cells, cultured on collagen I gels, formed tube networks with expressions of several endothelial-related markers. In coculture models of ECV304 cells and human umbilical vein endothelial cells, the two cells collaborated to form sprouts or networks.

CONCLUSION

ECV304 cells possess an endothelial character which confers the ability to mimic and collaborate with vascular endothelial cells and facilitates the acquisition of tumour microcirculation.

Phase I clinical trial of weekly docetaxel and exisulind, a novel inducer of apoptosis

BACKGROUND

The objective of this phase I study was to determine the maximal tolerated dose (MTD) of the combination of weekly docetaxel and exisulind in patients with advanced solid tumors.

PATIENTS AND METHODS

Patients with advanced or refractory solid tumors were treated with intravenous weekly docetaxel with daily oral exisulind. The following dose levels (docetaxel/exisulind) were explored: 30-mg/m2/200 mg po bid, 35/200, 35/250 and 40/250. Docetaxel was administered weekly for 6 weeks followed by 2 weeks off, and exisulind was taken twice daily. Each cycle was 8 weeks.

RESULTS

Eighteen patients were enrolled in the study. All of them had received prior systemic therapy. Most patients had either melanoma or carcinomas of the upper gastrointestinal tract. A total of 31 cycles of therapy were administered. DLTs were grade 3 diarrhea, anorexia and fatigue and grade 3 cutaneous toxicity at dose level 4 (40/250). Myelosuppression was mild. Fatigue and gastrointestinal toxicity (anorexia, dyspepsia, nausea, abdominal pain and diarrhea) represented the most common toxicities. However, grade 3 and grade 4 toxicities were uncommon. There were no treatment related deaths. No objective responses were observed and five patients achieved stable disease.

CONCLUSIONS

The recommended dose for phase II studies is weekly docetaxel 35 mg/m2 for 6 weeks followed by 2 weeks off in combination with oral exisulind 250 mg po bid. This combination is feasible and well-tolerated at these doses.

Zyflamend, a unique herbal preparation with nonselective COX inhibitory activity, induces apoptosis of prostate cancer cells that lack COX-2 expression

Cyclooxygenase (COX) inhibitors have suppressive effects on several types of cancer cells including prostate cancer. In this study, we considered the potential COX-inhibitory activity of a unique anti-inflammatory herbal preparation (Zyflamend; New Chapter, Inc., Brattleboro, VT) and analyzed its effects on the human prostate cancer cell line LNCaP. COX inhibitory activity of Zyflamend was determined by a spectrophotometric-based assay using purified ovine COX-1 and COX-2 enzymes. Effects of Zyflamend on LNCaP cell growth and apoptosis in vitro were assessed by cell counting, Western blot detection of poly ADP-ribose polymerase (PARP) cleavage, and measurement of caspase-3 activity in treated and control cell extracts. Western blotting techniques were conducted to determine the effects of this herbal preparation on the expression of the cell signaling proteins, p21, androgen receptor (AR), phospho-protein kinase C (pPKC)(alpha/beta), and phospho (p)Stat3. The phospohorylation status of several signal transduction phosphoproteins was profiled using a high-throughput phosphoprotein screening assay in treated cells and compared to controls. Zyflamend dramatically decreased COX-1 and COX-2 enzymatic activity. Elevated p21 expression coincided with attenuated cell growth following treatment of LNCaP cells with Zyflamend. PARP cleavage fragments were evident, and caspase-3 activity was upregulated over the control indicating the ability of Zyflamend to induce apoptosis of these cells. Androgen receptor expression levels declined by 40%, and decreases were observed in the active forms of Stat3 and PKC(alpha/beta) in Zyflamend-treated LNCaP cells. Zyflamend inhibited both COX-1 and COX-2 enzymatic activities, suppressed cell growth, and induced apoptosis in LNCaP cells. However, our data suggests that the effects are likely due to COX-independent mechanisms potentially involving enhanced expression of p21 and reduced expression of AR, pStat3, and pPKC(alpha/beta).

Non-COX-2 targets and cancer: Expanding the molecular target repertoire of chemoprevention

Chemoprevention represents a highly promising approach for the control of cancer. That nonsteroidal anti-inflammatory drugs (NSAIDs) prevent colon and other cancers has led to novel approaches to cancer prevention. The known inhibitory effect of NSAIDs on the eicosanoid pathway prompted mechanistic and drug development work focusing on cyclooxygenase (COX), culminating in clinical trials of cyclooxygenase 2 (COX-2) inhibitors for cancer prevention or treatment. However, two COX-2 inhibitors have been withdrawn due to side effects. Here we review several pathways of the eicosanoid cascade that are relevant to cancer; summarize the evidence regarding the role of COX-2 as a target for cancer prevention; and discuss several of the molecular targets that may mediate the chemopreventive effect of NSAIDs. The clinically modest results obtained to date with COX-2 specific inhibitors used in cancer prevention; the multiple COX-2-independent targets of both NSAIDs and COX-2 inhibitors; and the limitations of some COX-2 inhibitors indicate that exploiting these (non-COX-2) molecular targets will likely yield effective new approaches for cancer chemoprevention.