Treatment Of Castration-refractory Prostate Cancer Research Articles

Abstract 5097: PEDF inhibits bone metastases formation, prolongs survival and enhances the antitumor efficacy of low-dose chemotherapy in castration-refractory prostate cancer.

Abstract Background: The development of metronomic/low dose administration of conventional chemotherapeutic drugs has shown great promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which is down-regulated in prostate cancer. We have previously demonstrated that the over-expression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF anti-tumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF may enhance the cytotoxicity effects of low dose docetaxel (DTX) and cyclophosphamide (CTX) chemotherapies in vivo. Methods: PC3 and CL1 cell lines were genetically modified to stably express the fluorescent DsRed Express protein with PEDF. Resulting cells were characterized in vitro for PEDF expression by western blot and, for proliferation by growth curves and clone formation in matrigel. PEDF anti-tumor effects were assessed on established s.c. xenografts in mice treated with DTX (5mg/kg ip every 4 days, 1mg/kg ip daily for 10 days, 0.5mg/kg every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1-PEDF or -control cells into the left lobe of the dorsal prostate of anesthetized mice. For bone metastases, CL1-PEDF or -control cells were injected into the proximal region of the tibia. Results: We showed that PEDF expression inhibits the proliferation and induces the differentiation of CPRC cells in vitro, and decreases by 85% and 70% the development of s.c. PC3 and CL1 tumors, respectively. In vivo, PEDF expression inhibits the formation of bone metastases and bone destruction, and prolongs significantly (P=0.01; 95% confidence interval) the median survival of CL1 tumor-bearing mice (53±0.001 days versus 57±1). Furthermore, we demonstrated that PEDF enhances the cytotoxicity effects of low dose chemotherapy on established s.c. tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for PC3 and CL1) and prolongs significantly the survival of tumor-bearing mice undergoing low dose chemotherapy. Conclusions: These data reinforce the significance of PEDF as a potent target for the treatment of CRPC. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low dose chemotherapies. Citation Format: Thomas Nelius, Jennifer Hirsch, Stephanie Filleur. PEDF inhibits bone metastases formation, prolongs survival and enhances the antitumor efficacy of low-dose chemotherapy in castration-refractory prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5097. doi:10.1158/1538-7445.AM2013-5097 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

793 PIGMENT EPITHELIUM-DERIVED FACTOR INHIBITS BONE METASTASES FORMATION, PROLONGS SURVIVAL AND ENHANCES THE IN VIVO ANTITUMOR ACTIVITIES OF LOW-DOSE CHEMOTHERAPY IN CASTRATION-REFRACTORY PROSTATE CANCER

INTRODUCTION AND OBJECTIVES: The development of metronomic/low dose administration of conventional chemotherapeutic drugs has shown great promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which is down-regulated in prostate cancer. We have previously demonstrated that the over-expression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF anti-tumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF may enhance the cytotoxicity effects of low dose docetaxel (DTX) and cyclophosphamide (CTX) chemotherapies in vivo. METHODS: PC3 and CL1 cell lines were genetically modified to stably express the fluorescent DsRed Express protein with PEDF. Resulting cells were characterized in vitro for PEDF expression by western blot and, for proliferation by growth curves and clone formation in matrigel. PEDF anti-tumor effects were assessed on established s.c. xenografts in mice treated with DTX (5mg/kg ip every 4 days, 1mg/kg ip daily for 10 days, 0.5mg/kg every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1-PEDF or -control cells into the left lobe of the dorsal prostate of anesthetized mice. For bone metastases, CL1-PEDF or -control cells were injected into the proximal region of the tibia. RESULTS: We showed that PEDF expression inhibits the proliferation and induces the differentiation of CPRC cells in vitro, and decreases by 85% and 70% the development of s.c. PC3 and CL1 tumors, respectively. In vivo, PEDF expression inhibits the formation of bone metastases and bone destruction, and prolongs significantly (P 0.01; 95% confidence interval) the median survival of CL1 tumorbearing mice (53 0.001 days versus 57 1). Furthermore, we demonstrated that PEDF enhances the cytotoxicity effects of low dose chemotherapy on established s.c. tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for PC3 and CL1) and prolongs significantly the survival of tumor-bearing mice undergoing low dose chemotherapy. CONCLUSIONS: These data reinforce the significance of PEDF as a potent target for the treatment of CRPC. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low dose chemotherapies.

A randomized phase II trial of dexamethasone versus prednisolone as secondary hormonal therapy in CRPC.

123 Background: Dexamethasone and prednisolone are glucocorticosteroids used as second line hormonal treatment for castration refractory prostate cancer (CRPC). The biochemical response rates in cohort studies suggest that dexamethasone may be the more active agent. We conducted an open label, randomised phase II trial of dexamethasone versus prednisolone. Methods: Patients with castration resistant prostate cancer with progressive disease on androgen deprivation therapy were eligible. They were randomized to receive either prednisolone 10mg daily or dexamethasone 0.5mg daily. The main endpoint was confirmed PSA response rate according to the PSA Working Group 2 criteria. Patients with PSA progression on prednisolone crossed over to dexamethasone. Secondary endpoints included time to PSA progression, radiologic response rate using RECIST criteria, and safety. Results: Seventy-five patients were randomized. Confirmed PSA response was achieved in 12/39 patients (31%) on dexamethasone compared to 6/36 (17%) on prednisolone (p = 0.153). Median time to PSA progression was 9.7 months on dexamethasone compared to 5.1 months on prednisolone (HR 1.57, 95% CI 0.90 -2.75). In 43 patients with measurable disease, the response rate by RECIST criteria was 15% and 6% for dexamethasone and prednisolone, respectively (p = 0.606). Clinically significant toxicities were rare. Of 23 patients who crossed over at progression on prednisolone to dexamethasone, 19 patients were evaluable for PSA response. Seven of the 19 patients (37%) had a confirmed PSA response to dexamethasone after progression on prednisolone. Conclusions: The data are consistent with the hypothesis that dexamethasone is more active than prednisolone in the treatment of CRPC. In the absence of definitive, larger trials, dexamethasone should be used in preference to prednisolone in this setting. Clinical trial information: 2005-006018-16.

Effect of PEDF on the in vivo antitumor activities of low-dose chemotherapy in CRPC.

173 Background: The development of metronomic/low dose administration of conventional chemotherapeutic drugs has shown great promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which is down-regulated in prostate cancer. We have previously demonstrated that the over-expression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF anti-tumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF may enhance the cytotoxicity effects of low dose docetaxel (DTX) and cyclophosphamide (CTX) chemotherapies in vivo. Methods: PC3 and CL1 cell lines were genetically modified to stably express the fluorescent DsRed Express protein with PEDF. Resulting cells were characterized in vitro for PEDF expression by western blot and, for proliferation by growth curves and clone formation in matrigel. PEDF anti-tumor effects were assessed on established s.c. xenografts in mice treated with DTX (5mg/kg ip every 4 days, 1mg/kg ip daily for 10 days, 0.5mg/kg every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1-PEDF or -control cells into the left lobe of the dorsal prostate of anesthetized mice. Results: We showed that PEDF expression inhibits the proliferation and induces the differentiation of CPRC cells in vitro, and decreases by 85% and 70% the development of s.c. PC3 and CL1 tumors, respectively. In the survival study, PEDF expression prolongs significantly (P=0.01; 95% confidence interval) the median survival of CL1 tumor-bearing mice (53±0.001 days versus 57±1). Furthermore, we demonstrated that PEDF enhances the cytotoxicity effects of low dose chemotherapy on established s.c. tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for PC3 and CL1) and prolongs significantly the survival of tumor-bearing mice undergoing low dose chemotherapy. Conclusions: These data reinforce the significance of PEDF as a potent target for the treatment of CRPC. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low dose chemotherapies.

Abiraterone Acetate for the Treatment of Castrate-Refractory Prostate Cancer

Patients with de novo metastatic prostate cancer are primarily treated with androgen deprivation with very high (>95%) response rates, but all patients eventually develop castrate-refractory prostate cancer, which has a poor prognosis. Accumulating evidence suggests that continued androgen receptor signaling remains critical for survival and growth, with adrenal and intratumoral sources of androgens contributing to disease activation. Abiraterone acetate is a novel androgen biosynthesis inhibitor that has been shown to improve survival for patients with metastatic castrate-refractory prostate cancer who have progressed on docetaxel chemotherapy. It is a well-tolerated orally administered drug with a low incidence of serious side effects, taken with prednisone to reduce the secondary effects of mineralocorticoid excess. In the chemo-naive population, a recent trial has also shown improved outcomes, and ongoing studies are investigating its role even earlier in the disease course and in combination with other drugs.

Effect of PEDF on survival and in vivo antitumor activities of low-dose chemotherapy in castration-refractory prostate cancer.

e15103 Background: The development of metronomic/low-dose treatment with conventional chemotherapeutic drugs has recently shown promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which is downregulated in prostate cancer. Previously we demonstrated that overexpression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validate PEDF anti-tumor properties in highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF may enhance the cytotoxic effects of low-dose docetaxel (Doc) and cyclophosphamide (CTX) chemotherapies in vivo. Methods: Human PC3 and CL1 cell lines were genetically modified to stably express fluorescent DsRed Express protein with PEDF. Resulting cells were characterized in vitro for PEDF expression by western blot and for proliferation by growth curves and clone formation in Matrigel. PEDF anti-tumor effects were assessed on established SC xenografts in mice treated with Doc (5mg/kg IP every 4 days, 1mg/kg IP daily for 10 days, 0.5mg/kg IP every other day), CTX (10-20mg/kg in drinking water) or placebo. Survival studies were performed by injecting CL1 cells that express PEDF or control into the left lobe of the dorsal prostate of anesthetized mice. Results: We showed that PEDF inhibits proliferation and induces differentiation of all CPRC cells tested in vitro. Similarly, PEDF expression decreases by 85% and 70% the development of SC PC3 and CL1 tumors, respectively. In the survival study, we found that PEDF expression prolongs significantly (p=0.01; 95% confidence interval) median survival of CL1 tumor-bearing mice (53±0.001 days versus 57±1). Most importantly, we demonstrated that PEDF enhances the cytotoxic effects of low-dose chemotherapy on established tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for PC3 and CL1). Conclusions: This data reinforces the significance of PEDF as a potential new target when treating advanced prostate cancer. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low-dose Doc and CTX chemotherapies.

Sarcopenia and altered body composition following abiraterone acetate (AA) and corticosteroid (C) treatment in men with castration-refractory prostate cancer (CRPC).

e15134 Background: Sarcopenia, or skeletal muscle wasting, is an independent prognostic factor in advanced malignancy (Prado Lancet Onc 2008). Decreased muscle and increased fat are recognized side effects of androgen deprivation therapy. AA is a CYP17 inhibitor administered with corticosteroids (C), approved for treatment of advanced CRPC. AA reduces circulating androgens to ‘super-castrate’ levels; we hypothesized that AA + C would impact body composition. Methods: We retrospectively evaluated 54 CRPC pts treated on a Phase I/II trial. Pts received AA alone followed by combination AA + C on biochemical progression. CT scans at baseline, on AA alone and on AA + C were analyzed. Cross-sectional areas of fat and muscle were measured on 3 consecutive images at L4 using OsiriX 4.0. Muscle area was used to calculate skeletal muscle index (SMI); sarcopenia was defined as SMI <52.4 cm2/m2. Data were analyzed using t-tests and Kaplan-Meier analysis with overall survival (OS) measured from day 1 of AA. Results: Median duration on AA alone was 7.4 months (m; range 1.4-37.5); median duration on concurrent AA + C was 7.4m (range 0.9-46.2). Body composition did not change between two pre-treatment scans (n=29; median 3m apart). On AA alone there was a decrease in total fat (-8.5%, p=0.0001), visceral fat (-9.8%, p=0.0015) and muscle mass (-3.9%, p=0.0023) with a significant decrease in mean body mass index (BMI; -3.4 %, p=0.0118). Conversely AA + C was associated with increased total fat (+15.1%, p<0.0001) and visceral fat (+21.4%, p<0.0001) but no further change in muscle mass. Mean BMI significantly increased on the addition of C, returning to baseline levels (p< 0.0001). Overall, 13 pts (24%) were sarcopenic prior to commencing AA compared to 22 (41%) at the end of treatment. Pts who were sarcopenic at baseline had significantly reduced OS: 26.1m (95%CI 16.6 – 41) vs 46.5m (95%CI 28.6 – 57.5, p=0.0253). Conclusions: Treatment with AA alone resulted in decreased fat and muscle. AA + C increased body fat without further alteration in muscle mass. Changes in BMI did not reflect changes in body composition. Sarcopenia at baseline was a negative prognostic factor in this population.

Abstract 3717: Pigment epithelium-derived factor prolongs survival and enhances the in vivo antitumor activities of low-dose chemotherapy in castration-refractory prostate cancer

Abstract Background: The development of metronomic/low-dose administration of conventional chemotherapeutic drugs has recently shown great promise in the treatment of castration-refractory prostate cancer (CRPC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which has been shown to be down-regulated in prostate cancer. We have previously demonstrated that the over-expression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF anti-tumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF could enhance the cytotoxic effects of low-dose docetaxel (Doc) and cyclophosphamide (CTX) chemotherapies in vivo. Methods: Human CRPC PC3 and CL1 cell lines were genetically modified to stably co-express the fluorescent DsRed Express protein with PEDF. Resulting cell lines were characterized in vitro for PEDF expression by Western blot and for proliferation by growth curves and clone formation in Matrigel. PEDF anti-tumor effects were assessed on established subcutaneous xenografts in mice treated with Doc (5mg/kg ip every 4 days, 1mg/kg ip daily for 10 days, 0.5mg/kg ip every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1 cells, pre-mixed with 50nM hr-PEDF or carrier control, into the left lobe of the dorsal prostate of anesthetized mice. Results: We showed that PEDF inhibits the proliferation and induces the differentiation of all CRPC cells tested in vitro. Similarly, PEDF expression decreases the development of subcutaneous PC3 and CL1 tumors in immune-compromised mice by 85% and 70%, respectively. In the survival study, we found that all control animals die within 61 days after surgery while 50% of PEDF-pretreated animals were still alive. Most importantly, we demonstrated that PEDF enhances the cytotoxic effects of low-dose chemotherapy on established tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for both PC3 and CL1). Conclusions: This data reinforces the significance of PEDF as a potential new target for the treatment of advanced prostate cancer. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low-dose Doc and CTX chemotherapies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3717. doi:1538-7445.AM2012-3717

780 PIGMENT EPITHELIUM-DERIVED FACTOR PROLONGS SURVIVAL AND ENHANCES THE IN VIVO ANTI-TUMOR ACTIVITIES OF LOW-DOSE CHEMOTHERAPY IN CASTRATION-REFRACTORY PROSTATE CANCER

INTRODUCTION AND OBJECTIVES: The development of metronomic/low dosing of conventional chemotherapeutic drugs have recently showed great promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which has been shown to be down-regulated in prostate cancer. We have previously demonstrated that the overexpression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF antitumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF could enhance the cytotoxicity effects of low dose docetaxel (Doc) and cyclophosphamide (CTX) chemotherapies in vivo. METHODS: Human CRPC PC3 and CL1 cell lines were genetically modified to stably co-express the fluorescent DsRed Express protein with PEDF. Resulting cell lines were characterized in vitro for PEDF expression by western blot and, for proliferation by growth curves and clone formation in matrigel. PEDF anti-tumor effects were assessed on established s.c. xenografts in mice treated with Doc (5mg/kg ip every 4 days, 1mg/kg ip daily for 10 days, 0.5mg/kg every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1 cells, pre-mixed with 50nM hrPEDF or carrier control, into the left lobe of the dorsal prostate of anesthetized mice. RESULTS: We showed that PEDF inhibits the proliferation and induces the differentiation of all CPRC cells tested in vitro. Similarly, PEDF expression decreases by 85% and 70% the development of s.c. PC3 and CL1 tumors in immuno-compromised mice, respectively. In the survival study, we found that all control animals die within 61 days after surgery while 50% of PEDF-pretreated animals were still alive. Most importantly, we demonstrated that PEDF enhances the cytotoxicity effects of low dose chemotherapy on established tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for both PC3 and CL1). CONCLUSIONS: These data reinforce the significance of PEDF as a potential new target for the treatment of advanced prostate cancer. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low dose Doc and CTX chemotherapies.

Effect of PEDF on survival and the in vivo antitumor activities of low-dose chemotherapy in castration-refractory prostate cancer.

237 Background: The development of metronomic/low dose of conventional chemotherapeutic drugs have recently showed great promise in the treatment of castration-refractory prostate cancer (CPRC). Pigment Epithelium-Derived Factor (PEDF) is a natural angio-inhibitor which is down-regulated in prostate cancer. We have previously demonstrated that the over-expression of PEDF in human CRPC PC3 cells decreased tumor growth in vivo. In the present study, we further validated PEDF anti-tumor properties in the highly metastatic CRPC LNCaP-derivative CL1 cells. We also hypothesized that PEDF may enhance the cytotoxicity effects of low dose docetaxel (Doc) and cyclophosphamide (CTX) chemotherapies in vivo. Methods: Human PC3 and CL1 cell lines were genetically modified to stably express the fluorescent DsRed Express protein with PEDF. Resulting cells were characterized in vitro for PEDF expression by western blot and, for proliferation by growth curves and clone formation in matrigel. PEDF anti-tumor effects were assessed on established s.c. xenografts in mice treated with Doc (5mg/kg ip every 4 dy, 1mg/kg ip daily for 10 days, 0.5mg/kg every other day), CTX (10-20mg/kg in the drinking water) or placebo. Survival studies were performed by injecting CL1 cells with 50nM hrPEDF or carrier control into the left lobe of the dorsal prostate of anesthetized mice. Results: We showed that PEDF inhibits the proliferation and induces the differentiation of all CPRC cells tested in vitro. Similarly, PEDF expression decreases by 85% and 70% the development of s.c. PC3 and CL1 tumors, respectively. In the survival study, we found that all control animals die within 61 days after surgery while 50% of PEDF-pretreated animals were still alive. Most importantly, we demonstrated that PEDF enhances the cytotoxicity effects of low dose chemotherapy on established tumors (best Doc dose: 1mg/kg for PC3 and 5mg/kg for CL1; best CTX dose: 10mg/kg for PC3 and CL1). Conclusions: These data reinforce the significance of PEDF as a potential new target for the treatment of advanced prostate cancer. It also emphasizes PEDF as a promising new agent to enhance the anti-tumor efficacy of low dose Doc and CTX chemotherapies.

Phase II study of cytarabine in men with docetaxel‐refractory, castration‐resistant prostate cancer with evaluation of TMPRSS2‐ERG and SPINK1 as serum biomarkers

What's known on the subject? and What does the study add? To date, there has been limited impetus to examine the use of cytarabine in prostate cancer. We presented preliminary laboratory data to suggest its utility in the castration refractory prostate cancer (CRPC) population which, combined with a previous case report, suggested it may have hitherto unrecognized utility in this setting. Embedded in this study was peripheral blood sampling for TMPRSS2-ERG and SPINK1, two genes that are believed to define prostate cancer genotypes, to assess their utility as biomarkers This study suggests that at the delivered doses, cytarabine has limited efficacy and significant myelotoxicity suggesting, it does not have a role in the treatment of docetaxel-refractory CRPC. The presence of serum TMPRSS2-ERG and SPINK1 mRNA biomarkers recovered from blood suggest that their analysis is worthy of further study. To run a phase II clinical trial of cytarabine in men with docetaxel-refractory, castration-resistant prostate cancer (CRPC), based on evidence that cytarabine might be effective in men with abnormalities of ERG oncogenes. To measure mRNA levels of prostate cancer-related genes in blood as biomarkers. Ten of a planned maximum of 30 men received i.v. cytarabine at doses of 0.25-1g/m(2) at 21-day intervals. The primary endpoint was prostate-specific antigen (PSA) response. Archival tumour samples were assessed by fluorescence in-situ hybridization for TMPRSS2:ERG translocation, and by immunohistochemistry for serine peptidase inhibitor Kazal type 1 (SPINK1). Blood was processed for mRNA quantification of TMPRSS2:ERG (exon1:exon4), SPINK1 and PSA. A PSA response was not observed in any patient. The trial was stopped at the end of stage 1 of a modified Flemming design. The median number of cycles administered was 3. Grade 3-4 haematological toxicity was common. Five patients were subsequently excluded from the study for toxicity, and five for disease progression. Analysis of whole blood mRNA for T1:E4 translocation in TMPRSS2:ERG was consistent with that in the tumour in 8/9 evaluable cases (one was concordantly positive, seven were concordantly negative), SPINK1 results were concordant in 9/10 cases (two were concordantly positive, seven were concordantly negative [P = 0.047 for the predictive value]). There was no correlation between PSA or SPINK protein and their respective mRNA copy levels in blood. Cytarabine at the doses used is ineffective for men with CRPC. Blood mRNA levels of prostate cancer genes may represent a novel aspect of monitoring prostate cancer and have implications for the understanding of tumour-derived mRNA.

A new approach to delay the development of resistance to docetaxel in the treatment of castration-refractory prostate cancer.

e15177 Background: Resistance to docetaxel is a common problem in the treatment of castration-refractory prostate cancer (CPRC). Pigment epithelium-derived factor (PEDF) is antiangiogenic. We have shown that: (a) PEDF is down-regulated in prostate cancer; and (b) over-expression of PEDF in CRPC cells decreased tumor growth in vivo. Since both increase in interleukin-8 (IL8) production and, plasma membrane Vacuolar H+-ATPases(pmV-ATPases) have been involved in the resistance of cancer cells to chemotherapeutic drugs, we hypothesize that PEDF enhances docetaxel cytotoxicity by modulating IL8 and pmV-ATPases in prostate cancer cells. Methods: CRPC cells (PC3/DU145) were treated with 0-100 nM PEDF alone or in combination with 0-100 nM docetaxel. IL8 was measured in cell conditioned media by ELISA. mRNA levels of the a isoforms that target V-ATPase to the cell surface were investigated by qPCR. pmV-ATPase activity was measured on isolated plasma membranes. To evaluate PEDF anti-tumor properties, we used human CRPC LNCaP-derivative CL1 and LNCaP cell lines that stably express the fluorescent DsRed Express protein in combination with PEDF. Results: We found that PEDF inhibits the proliferation of all CPRC cells tested in vitro associated with a decrease in IL8 production in PC3 and DU145 cells. The effect of PEDF on growth was prominent in PC3 and DU145 cells under PEDF/docetaxel combined treatment. The mRNA levels of the a isoforms of pmV-ATPase were decreased when PEDF is expressed. PEDF expression in vivo decreases by 70% the development of subcutaneous CL1 tumors in immuno-compromised mice. We injected CL1 cells (pre-mixed with 50 nM human recombinant PEDF) into the left lobe of mice dorsal prostate. We found that all control animals die within 61 days after surgery. Importantly, 50% of PEDF-pretreated animals were still alive. Conclusions: These data indicate that inhibition of V-ATPases and over-expression of PEDF are promising new targets to enhance the cytotoxicity of docetaxel drug. Understanding the consequences of V-ATPase inhibition or PEDF over-expression in human prostate cancer cells will contribute significantly to our understanding of prostate cancer progression and treatment.

Abstract 1711: Establishment and characterization of docetaxel resistant prostate cancer cell lines

Abstract Introduction: For treatment of castration-refractory prostate cancer (CRPC) patients a systemic chemotherapy and a second line hormone therapy have been developed in the last years. The administration of the chemotherapeutic drug docetaxel in combination with prednisone given to patients with CRPC on the basis of its improved survival, pain reduction, PSA response, and quality of life is the state of the art treatment at the moment. However, many patients do not respond to docetaxel or develop a resistance during treatment. Due to the low overall response survival of the patient is prolonged just for a few months. Until now, not much of molecular characteristics for docetaxel resistance is known in prostate cancer. Therefore, the main aim of the study was the establishment and characterization of docetaxel resistant cell lines. For this reason we generated docetaxel resistent sub cell lines of DU-145 and PC3 cells, which are considered models for an advanced disease. Methods: PC3 and DU-145 cells were treated with increasing concentrations of docetaxel (up to 12,5nM). The resistance of the newly established sub lines was determined by testing cell viability, proliferation, apoptosis, and cell cycle regulation with MTT, [3H]thymidine incorporation assay and FACS measurement, respectively. Results: Treatment of parental PC3 and DU-145 cells with 12,5nM docetaxel up to 4 days leads to a significant decrease in cell viability. An increase of cleaved PARP protein after 48h for DU-145 and after 72h for PC3 cells could confirm this observation. In contrast to parental cells, the newly established PC3-DR and DU-145-DR docetaxel resistant cells have a different cell morphology. Treatment with docetaxel did not result in increased cPARP levels. Moreover, we could not detect a significant difference in proliferation, basal apoptosis and cell cycle regulation in a direct comparison between parental PC3 and PC3-DR cells. DU-145-DR cells showed a slight increase in apoptosis and a significant decrease in proliferation after docetaxel treatment. However, we still observed a higher viability compared to parental DU-145 cells treated with 12.5nM docetaxel. Conclusions: The generated sub lines are less sensitive to docetaxel compared to the parental cells. However, DU-145-DR cells are more sensitive to docetaxel than PC3-DR cells. Taken together, we report on successful establishment and characterization of docetaxel-resistant PC3 and DU-145 cells. These cells represent a promising cellular model to investigate the responsible molecular mechanism for docetaxel resistance in prostate cancer cells in vitro. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1711. doi:10.1158/1538-7445.AM2011-1711

Efficacy of low‐dose dexamethasone in castration‐refractory prostate cancer

To evaluate the prostate-specific antigen (PSA) response rate and duration of PSA response to dexamethasone in patients with castration-refractory prostate cancer (CRPC), as corticosteroids are frequently used as second-line hormonal treatment of CRPC and there is little published evidence concerning the efficacy of low-dose dexamethasone in this setting. In all, 102 patients with progressive CRPC received oral dexamethasone (0.5 mg daily) between January 2003 and October 2006. The median pretreatment PSA level was 83 ng/mL. The main endpoint was the PSA response rate according to the PSA Working Group criteria. In all, 50 patients (49%) had a confirmed PSA response. The median (range) time to PSA progression for the entire cohort was 7.4 (1-28) months. In responders, the median duration of the PSA response was 11.6 (1-24) months. Low-dose dexamethasone has significant activity in CRPC. Subject to validation with more clinically meaningful endpoints, dexamethasone could become the corticosteroid of choice in the management of CRPC, and its potential for use in combination with novel agents should be explored.