Hormone-Refractory Prostate Cancer

High-dose calcitriol, docetaxel and zoledronic acid in patients with castration-resistant prostate cancer: a phase II study

INTRODUCTION

Docetaxel has become the standard chemotherapy for patients with castration-resistant prostate cancer (CRPC). We wanted to assess the efficacy and safety of a weekly high-dose calcitriol, docetaxel and zoledronic acid combination in CRPC.

PATIENTS AND METHODS

Thirty patients were enrolled to receive calcitriol 0.5 µg/kg orally in 4 divided doses over 4 h on day 1 of each treatment week, docetaxel 36 mg/m(2) i.v. infusion on day 2 of each treatment week and zoledronic acid 4 mg i.v. on day 2 of the first and fifth week of each cycle. Treatment was administered weekly for 6 consecutive weeks on an 8-week cycle.

RESULTS

Out of 23 evaluable patients, there was a response of prostate-specific antigen (PSA) in 11 patients (47.8%); 6 (26.1%) had a stable PSA level for a median of 4.2 months. The median survival time was 15 months (95% confidence interval 13.9-16.1 months). The regimen was generally tolerated; anemia was the only grade 3/4 hematological toxicity in 2 patients.

CONCLUSIONS

This regimen was tolerated, and half of the patients had a PSA response. Although our response rates are inferior to some studies using docetaxel, we believe our response rates are acceptable knowing that we are treating CRPC, which still has variable outcomes.

The role of hypoxia-inducible factor-1α and -2α in androgen insensitive prostate cancer cells

OBJECTIVES

The aim of this study was to investigate the effects of induction and knocking down of hypoxia-inducible factor (HIF)-1α and/or -2α on tumor biology in androgen insensitive prostate cancer cell lines.

MATERIALS AND METHODS

The induction patterns of HIF-1α and -2α after treatment with ZnSO4 were evaluated in PC3 and DU145 cells. Both cell lines were transfected with siRNA targeted against HIF-1α and/or -2α, and the expression patterns of these 2 HIF isoforms were examined. We next performed cell counting Kit-8 (CCK-8) assays and matrigel invasion assays. Potential additive effects of HIF blockade to chemotherapy (docetaxel) or target agents (sunitinib and sorafenib) were examined. In addition, gene expression changes were determined in ZnSO4-treated DU145 cells using Western blotting.

RESULTS

ZnSO4 affected the expression of HIF in a dose-dependent manner. HIF expression was increased within the first 3 hours but then decreased. Cells in which HIF-1α and/or -2α had been knocked down using siRNA showed decreased cell viability. Invasion abilities were increased by ZnSO4 treatment in both cell lines overexpressing HIF. However, invasion potencies were decreased in response to treatment with HIF siRNAs. Blocking HIF prominently augmented the antitumor effects of target agents. The underlying mechanism could be associated with p21, cMET, IGF-1, and GLUT-1.

CONCLUSIONS

Our results demonstrate that HIF-1α and -2α are important for cell proliferation and invasion ability in prostate cancer. Together, our results indicate that combinations of target agents with HIF knockdown may represent a promising strategy for the treatment of prostate cancer.

Rottlerin potentiates camptothecin-induced cytotoxicity in human hormone refractory prostate cancers through increased formation and stabilization of topoisomerase I-DNA cleavage complexes in a PKCδ-independent pathway

Combination therapy, which can optimize killing activity to cancers and minimize drug resistance, is a mainstream therapy against hormone-refractory prostate cancers (HRPCs). Rottlerin, a natural polyphenolic component, synergistically increased PC-3 (a HRPC cell line) apoptosis induced by camptothecin (a topoisomerase I inhibitor). Using siRNA technique to knockdown protein kinase C-δ (PKCδ), the data showed that rottlerin-mediated synergistic effect was PKCδ-independent, although rottlerin has been used as a PKCδ inhibitor. Rottlerin potentiated camptothecin-induced DNA fragmentation at S phase and ATM phosphorylation at Ser1981. The effect was correlated to apoptosis (r2 = 0.9). To detect upstream signals, the data showed that camptothecin acted on and stabilized topoisomerase I-DNA complex, leading to the formation of camptothecin-trapped cleavage complexes (TOP1cc). The effect was potentiated by rottlerin. To determine DNA repair capability, the time-related γH2A.X formation was examined after camptothecin removal. Consequently, rottlerin significantly inhibited camptothecin removal-mediated decline of γH2A.X formation at S phase, indicating the impairment of DNA repair activity in the presence of rottlerin. The combinatory treatment of camptothecin and rottlerin induced conformational change and activation of Bax and formation of truncated Bad, suggesting the contribution of mitochondria stress to apoptosis. In summary, the data suggest that rottlerin-mediated camptothecin sensitization is through the augmented stabilization of TOP1cc, leading to an increase of DNA damage stress and, possibly, an impairment of DNA repair capability. Subsequently, mitochondria-involved apoptosis is triggered through Bax activation and truncated Bad formation. The novel discovery may provide an anticancer approach of combinatory use between rottlerin and camptothecin for the treatment of HRPCs.

The androgen-regulated Calcium-Activated Nucleotidase 1 (CANT1) is commonly overexpressed in prostate cancer and is tumor-biologically relevant in vitro

Previously, we identified the calcium-activated nucleotidase 1 (CANT1) transcript as up-regulated in prostate cancer. Now, we studied CANT1 protein expression in a large cohort of nearly 1000 prostatic tissue samples including normal tissue, prostatic intraepithelial neoplasia (PIN), primary carcinomas, metastases, and castrate-resistant carcinomas, and further investigated its functional relevance. CANT1 displayed predominantly a Golgi-type immunoreactivity with additional and variable cytoplasmic staining. In comparison to normal tissues, the staining intensity was significantly increased in PIN lesions and cancer. In cancer, high CANT1 levels were associated with a better prognosis, and castrate-resistant carcinomas commonly showed lower CANT1 levels than primary carcinomas. The functional role of CANT1 was investigated using RNA interference in two prostate cancer cell lines with abundant endogenous CANT1 protein. On CANT1 knockdown, a significantly diminished cell number and DNA synthesis rate, a cell cycle arrest in G(1) phase, and a strong decrease of cell transmigration rate and wound healing capacity of CANT1 knockdown cells was found. However, on forced CANT1 overexpression, cell proliferation and migration remained unchanged. In summary, CANT1 is commonly overexpressed in the vast majority of primary prostate carcinomas and in the precursor lesion PIN and may represent a novel prognostic biomarker. Moreover, this is the first study to demonstrate a functional involvement of CANT1 in tumor biology.

Castration-resistant prostate cancer: current and emerging treatment strategies

Until very recently, docetaxel was the only approved agent in castration-resistant prostate cancer (CRPC) and other effective therapeutic options are urgently needed. In recent years, several new agents with promising activity and a favourable toxicity profile have been developed and clinically investigated in the fields of hormonal, cytotoxic, targeted and immune therapy. In particular, recent results from two large phase III trials of sipuleucel-T and cabazitaxel show that these two agents significantly prolong overall survival in CRPC. Indeed, sipuleucel-T has recently been approved by the US FDA for the treatment of CRPC. Many other pharmaceuticals, which are presented in this review, have been investigated recently or are being investigated in phase III trials and might prove to be effective in the future. Reviewed articles are discussed in light of the innovations in study design brought by the Prostate Cancer Clinical Trials Working Group (PCWG2), which updated the Prostate-Specific Antigen Working Group (PCWG1) guidelines, in order to allow better identification of potentially active drugs in clinical trials.

Efficacy and safety of docetaxel plus prednisolone chemotherapy for metastatic hormone-refractory prostate adenocarcinoma: single institutional study in Korea

PURPOSE

To assess the efficacy and safety of treating Korean patients with metastatic hormone-refractory prostate cancer (HRPC) using docetaxel plus prednisolone chemotherapy.

MATERIALS AND METHODS

This was a retrospective cohort study performed in 98 patients with metastatic HRPC between October 2003 and April 2008. After screening, 72 patients fit the eligibility criteria for inclusion in this study. Treatment consisted of 5 mg prednisolone twice daily and 75 mg/m² docetaxel once every 3 weeks.

RESULTS

Patient demographic characteristics included: median age 67 years (range, 51~86), median ECOG performance status 1 (0~2), Gleason score ≥8 in 61 patients (86%), and median serum PSA 45.5 ng/mL (range, 3.7~2,420.0). A total of 405 cycles of treatment were administered with a median 6 cycles (range, 1~20) per patient. The median docetaxel dose-intensity was 24.4 mg/m(2)/week (range, 17.5~25.6). A PSA response was seen in 51% of 63 evaluable patients at 12 weeks and maximal PSA decline ≥50% in 59% of 70 evaluable patients. Tumor response was evaluated in 13 patients, 4 patients achieved PR, and 5 patients had SD with a response rate of 31%. With a median follow-up duration of 23.1 months (95%CI, 16.7~29.5), the median time to PSA progression was 5.1 months (95%CI, 4.5~5.8) and median overall survival was 22.8 months (95%CI, 16.6~29.1). Nine (13%) patients experienced grade 3 or higher febrile neutropenia.

CONCLUSION

This chemotherapy regimen (docetaxel every 3 weeks plus prednisolone daily) demonstrated a strong response in Korean patients with metastatic HRPC, while the toxicity profile was manageable and similar to that observed in Western patients.

Human xenograft models as useful tools to assess the potential of novel therapeutics in prostate cancer

With docetaxel as effective chemotherapy for hormone refractory prostate cancer (HRPC), the number of new treatment combinations for HRPC is expanding demanding a fast-track screening system. This review elaborates on the use of xenograft models to select the most promising combination therapies for entering into phase II clinical trials.

Induction of multinucleated cells and apoptosis in the PC-3 prostate cancer cell line by low concentrations of polyethylene glycol 1000

Polyethylene glycol (PEG) has been reported to inhibit the development of colonic lesions in carcinogen-treated rats when administered orally. However, the precise mechanism for the chemopreventive activity of PEG remains largely elusive. Based on a characteristic feature of PEG as a 'fusogen', we investigated its potential as a chemotherapeutic agent through the induction of multinucleated cell formation and apoptosis induction in PC-3 prostate cancer cells. When PC-3 cells were treated with 0.5 and 1.0% PEG 1000, multinucleated cells were induced at a frequency of 8.4 and 13%, respectively, 36 h after PEG treatment under high cell density (1 x 10(6) cells in 100 microL PEG solution) in vitro. Although abnormality of cell cycle progression was not evident in PEG-treated PC-3 cells, multinucleated cells substantially disappeared at around 38 h due to apoptosis. In contrast, no apparent growth suppression was observed when PC-3 cells were exposed to up to 1.0% PEG at a much lower cell density, namely under ordinary culture conditions. Furthermore, injection of 0.5% PEG solution in vivo into PC-3 xenografts implanted in BALB/c-nu/nu male mice significantly suppressed tumor growth compared to phosphate-buffered saline injection. Multinucleated TdT-mediated dUTP-biotin nick end-labeling (TUNEL)-positive cells were observed inside the PEG-injected tumors. PEG was here demonstrated to have anticell proliferation and antitumor effects via induction of apoptosis, possibly by cell fusion. PEG injection therapy could therefore be adopted as an alternative chemotherapeutic strategy for localized prostate cancers, including those that become refractory to androgen-deprivation therapy.

Combination of bevacizumab and docetaxel in docetaxel-pretreated hormone-refractory prostate cancer: a phase 2 study

OBJECTIVE

Although the taxanes represent the most active agents for the first-line treatment of metastatic hormone-refractory prostate cancer (HRPC), most patients eventually progress while receiving taxane-based treatments. No agents are approved for second-line therapy in HRPC, but common standard practice for the oncologists is to treat patients also after docetaxel failure.

METHODS

Twenty highly pretreated patients with HRPC received bevacizumab (10mg/kg) and docetaxel (60mg/m(2)) every 3 wk. All patients had bone metastases and eight had measurable lesions.

RESULTS

Eleven patients (55%) had major prostate-specific antigen (PSA) responses, and 3 (37.5%) had objective responses. Seven major PSA responses were recorded in the same patients who had reported a >50% PSA decrease after first-line docetaxel. However, four major PSA responses were observed in patients previously nonresponsive to docetaxel alone. The treatment was well tolerated.

CONCLUSIONS

Our results show that the combination of bevacizumab and docetaxel is active and well tolerated. Continued investigation of bevacizumab with cytotoxic chemotherapy is warranted in HRPC.