Estramustine revisited

SAHA-sensitized prostate cancer cells to TNFalpha-related apoptosis-inducing ligand (TRAIL): mechanisms leading to synergistic apoptosis

Treatment of cancer cells with histone deacetylase inhibitors (HDACi) such as suberolylanilide hydroxamic acid (SAHA) activates genes that promote apoptosis. To enhance proapoptotic efficiency, SAHA has been used in combination with radiation, kinase inhibitors and cytotoxic drugs. Although several prostate cells respond to TNFalpha-Related Apoptosis-Inducing Ligand (TRAIL), LNCaP are resistant. This model system was utilized to examine the advantages of combined treatment with SAHA and TRAIL. In LNCaP cells, TRAIL induced synergistic apoptosis when combined even with the lowest dose of SAHA. Treatment with caspase inhibitor confirmed that SAHA-induced apoptosis was mediated through caspases. In addition to induction of apoptosis, SAHA and TRAIL decreased the levels of proapoptotic proteins IKKalpha, IKKbeta and IKKgamma, suggesting that SAHA treatment may reduce the activity of NFkappaB. However, assay for NFkappaB luciferase reporter activity showed highly significant increase in SAHA-treated cells, supporting earlier suggestions that HDACi promotes NFkappaB transcriptional activity. Further analyses to determine the mechanisms by which the combination of SAHA and TRAIL led to synergistic apoptosis indicated that the apoptotic response of LNCaP is due to a complex regulation of death receptor pathway and alterations of NFkappaB activity at several regulatory steps.

Gene expression profiling reveals novel targets of estramustine phosphate in prostate cancer cells

Estramustine phosphate (EMP) is a compound widely used for the treatment of hormone-refractory prostate cancer. In order to better understand the precise molecular mechanism(s) by which EMP exerts its effects on hormone-resistant PC3 prostate cancer cells, we have utilized microarray to interrogate 22,215 known genes to determine the gene expression profiles altered by EMP treatment. The purpose of this investigation was to identify gene expression profile first and then in future studies determine the specific role of these genes in EMP-induced apoptosis in prostate cancer cells. We found a total of 726 genes which showed >2 fold change after EMP treatment. Clustering analysis showed 12 different types of expression alteration. These genes were also subjected to cluster analysis according to their biological functions. We found that EMP regulated the expression of genes, which are critically involved in the regulation of cell growth, cell cycle, apoptosis, iron homeostasis, cytoskeleton and cell signaling transduction. Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis was used to confirm the results of microarray, and the results of real-time quantitative RT-PCR were consistent with the microarray data. From these results, we conclude that EMP caused changes in the expression of a large number of genes that are related to the control of cell survival and physiological behaviors. The gene expression profiles may provide comprehensive molecular mechanism(s) by which EMP exerts its pleiotropic effects on prostate cancer cells. EMP-induced regulation of these genes may be further exploited for devising therapeutic strategies for prostate cancer.

Regulation of Vinca alkaloid-induced apoptosis by NF-κB/IκB pathway in human tumor cells

Antimicrotubule Vinca alkaloids, such as vinblastine and vincristine, interfere with the dynamics of microtubules and have shown significant cell killing activity in a variety of tumor cells through induction of apoptosis. The mechanism by which Vinca alkaloids induce apoptosis is not entirely clear. In this study, we found that glucocorticoids inhibit Vinca alkaloid-induced apoptosis without affecting G2-M arrest in human breast cancer BCap37 cells and human epidermoid tumor KB cells, suggesting that Vinca alkaloid-induced apoptosis may occur via a pathway independent of cell cycle arrest. Further analyses indicated that Vinca alkaloids cause significant degradation of IκBα, which in turn results in nuclear factor-κB (NF-κB) activation. Transfection of antisense IκBα in BCap37 cells sensitizes Vinca alkaloid-induced apoptosis. Moreover, in vitro kinase assays show that the activity of IκB kinase (IKK) was activated by Vinca alkaloids and was not affected by glucocorticoids. Stable transfection of dominant-negative deletional mutant IκBα, which is insensitive to IKK-mediated phosphorylation and degradation, resulted in the inhibition of Vinca alkaloid-induced NF-κB activation and reduced sensitivity of tumor cells to Vinca alkaloid-induced apoptosis. These findings suggest that the NF-κB/IκB signaling pathway may contribute to the mediation of Vinca alkaloid-induced apoptosis in human tumor cells.

The Evolving Role of Chemotherapy and Other Systemic Therapies for Managing Localized Prostate Cancer

PURPOSE

The recent literature is reviewed regarding the use of neoadjuvant and adjuvant chemotherapy, and promising new molecular targeted agents in patients with high risk localized prostate cancer.

MATERIALS AND METHODS

A MEDLINE literature review was performed of studies evaluating chemotherapy and other systemic therapies for localized prostate cancer.

RESULTS

Patients with prostate cancer at high risk for recurrence despite local therapy include those with clinical stage T3 disease, biopsy Gleason scores of 8 to 10 or serum prostate specific antigen greater than 20 ng/ml. Although hormonal therapy has palliative benefit for the majority of patients with metastatic disease, randomized trials have not demonstrated a survival benefit from its administration before surgery for high risk localized disease. Recent trials have shown that cytotoxic chemotherapy has significant activity in hormone refractory prostate cancer, which has led to ongoing clinical trials that are investigating the use of chemotherapy in the neoadjuvant setting. Published and ongoing clinical trials in the use of systemic therapy for localized prostate cancer are reviewed.

CONCLUSIONS

Systemic therapy for advanced prostate cancer is improving. Efforts to use such therapies for managing localized disease are ongoing.

Neoadjuvant therapy before radical prostatectomy in high-risk localized prostate cancer: defining appropriate endpoints

High-risk localized prostate cancer remains a vexing problem for clinicians. Definitive local treatments such as surgery and radiation therapy cure only a minority of these patients. As a result, efforts are being made to reduce the risk of recurrence by using chemotherapy and new agents before, during or after definitive local therapy. Neoadjuvant androgen deprivation therapy has yielded disappointing results when combined with surgery. Chemotherapy in the management of localized disease is evolving, and preliminary studies are just now being completed. Although these agents have established activity and acceptable toxicity in the hormone-refractory setting, more extensive use of them in patients with androgen-dependent disease will require data from randomized studies to determine overall efficacy. New molecular-targeted therapies are promising and hold the greatest hope that outcomes in early disease may be improved with early use of systemic therapy. The neoadjuvant surgical model also has promise in assessing the activity of new drugs, because it provides a means to determine molecular effects of specific agents, along with standard pathologic and clinical parameters of efficacy.

Recent advances in chemotherapy for advanced prostate cancer

Recently, several important studies have validated prostate-specific antigen (PSA) as a reliable measure of response to chemotherapeutic treatment in advanced hormone-refractory prostate cancer. Furthermore, although chemotherapy in this setting has always been considered palliative, several analyses of recent clinical trials have demonstrated a significant association between declines in PSA values of 50% or more and prolonged survival. Mitoxantrone, in combination with prednisone, has been shown to provide significant palliation and improved quality of life. The use of combinations of chemotheraputic agents also seems to provide significantly superior objective and subjective responses compared with single-agent regimens. In particular, estramustine has been shown to synergize many of the agents used in prostate cancer treatment and has been demonstrated to provide significant palliation and decline in PSA levels in combination with vinblastine, vinorelbine, etoposide, paclitaxel, and docetaxel. The results of several important trials of the taxanes both as single agents and in combination with estramustine have been completed in the past year and have demonstrated that these agents are very effective in the treatment of hormone-refractory prostate cancer.