Treatment Of Hormone-refractory Prostate Cancer Research Articles

TGF-β causes Docetaxel resistance in Prostate Cancer via the induction of Bcl-2 by acetylated KLF5 and Protein Stabilization.

Prostate cancer is the second leading cause of cancer-related death in the United States. As a first line treatment for hormone-refractory prostate cancer, docetaxel (DTX) treatment leads to suboptimal effect since almost all patients eventually develop DTX resistance. In this study, we investigated whether and how TGF-β affects DTX resistance of prostate cancer.Methods: Cytotoxicity of DTX in DU 145 and PC-3 cells was measured by CCK-8 and Matrigel colony formation assays. Resistance to DTX in DU 145 cells was examined in a xenograft tumorigenesis model. A luciferase reporter system was used to determine transcriptional activities. Gene expression was analyzed by RT-qPCR and Western blotting.Results: We found that KLF5 is indispensable in TGF-β-induced DTX resistance. Moreover, KLF5 acetylation at lysine 369 mediates DTX resistance in vitro and in vivo. We showed that the TGF-β/acetylated KLF5 signaling axis activates Bcl-2 expression transcriptionally. Furthermore, DTX-induced Bcl-2 degradation depends on a proteasome pathway, and TGF-β inhibits DTX-induced Bcl-2 ubiquitination.Conclusion: Our study demonstrated that the TGF-β-acetylated KLF5-Bcl-2 signaling axis mediates DTX resistance in prostate cancer and blockade of this pathway could provide clinical insights into chemoresistance of prostate cancer.

Plumbagin Triggers ER Stress-Mediated Apoptosis in Prostate Cancer Cells via Induction of ROS

Background/Aims: Prostate cancer (PCa) is the second most frequently diagnosed cancer in men worldwide. Currently available therapies for hormone-refractory PCa are only marginally effective. Plumbagin (PLB), a natural naphthoquinone isolated from the traditional folk medicine Plumbago zeylanica, is known to selectively kill tumor cells. Nevertheless, antitumor mechanisms initiated by PLB in cancer cells have not been fully defined. Methods: MTT assay was used to evaluate the effect of PLB on the viability of cancer cells. Cell apoptosis and reactive oxygen species (ROS) production were determined by flow cytometry. Protein expression was detected by western blotting. In vivo anti-tumor effect was measured by using tumor xenoqraft model in nude mice. Results: In the present study, we found that PLB decreases cancer cell growth and induces apoptosis in DU145 and PC-3 cells. In addition, by increasing intracellular ROS levels, PLB induced a lethal endoplasmic reticulum stress response in PCa cells. Importantly, blockage of ROS production significantly reversed PLB-induced ER stress activation and cell apoptosis. In vivo, we found that PLB inhibits the growth of PCa xenografts without exhibiting toxicity Treatment of mice bearing human PCa xenografts with PLB was also associated with induction of ER stress activation. Conclusion: Inducing ER stress by PLB thus discloses a previously unrecognized mechanism underlying the biological activity of PLB and provides an in-depth insight into the action of PLB in the treatment of hormone-refractory PCa.

Abstract 176: Early development of GMC1, a novel molecule targeting FKBP52 for the treatment of hormone-refractory prostate cancer

Abstract Purpose: GMC1 directly inhibits FKBP52, effectively blocking androgen receptor dependent gene expression and androgen-stimulated proliferation. This make it an attractive option for the treatment of hormone-dependent and hormone-independent prostate cancer. This study investigated an analytical method for GMC1 quantification, pre-formulation characteristics of GMC1, and developed intravenous formulations for the evaluation of GMC1 in animal models. Method: An LC/MS/MS method for the quantification of GMC1 in solution, plasma and urine was developed, validated and applied to the determination of the stability, log P, plasma protein binding and solubility of GMC1 in various solvents. Liposomal formulations and co-solvent systems with various ratios of high capacity vehicles were formulated and the optimal formulation applied, at 2 mg/kg single IV bolus dose, to the pharmacokinetic study of GMC1 in a rat model. Result: The intra- and inter-day accuracy (%RE) and precision (%CV) of the LC/MS/MS method ranged from 1.6 – 11.7 % and 1.4 – 8.8 %, respectively. GMC1 is stable in solid and solution state, moderately lipophilic (log P = 1.38 ± 0.05), poorly water soluble (0.4 ± 0.01 mg/mL), and highly plasma protein bound (>71%). The optimal formulation consisting of PEG 300 and Labrasol ® (1:1, v/v) allowed us to achieve a GMC1 concentration of 10 mg/mL, and tolerated an aqueous environment. GMC1 has a tri-exponential disposition with a Cmax of 7.6 ± 1.97 mg/L, clearance of 0.53 L/kg/hr, α-distribution, β-phase and terminal elimination half-lives of 0.1 ± 0.04 hr, 1.2 ± 0.34 hr, and 19.7 ± 5.09 hr respectively. Conclusion: The LC/MS/MS method, formulations and pharmacokinetic study can be applied to the pre-clinical and clinical development of GMC1. Grant Support: This work was performed under funding from NIH/NIGMS grant (5SC3GM102018) and NIH/NIMHD/RCMI grant (5G12MD007605). Citation Format: Huan Xie, Oscar Ekpenyong. Early development of GMC1, a novel molecule targeting FKBP52 for the treatment of hormone-refractory prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 176. doi:10.1158/1538-7445.AM2017-176

New treatment for advanced and hormone refractory prostate cancer (HRPC) with an oral cholesterol derivative (hydroxysterol 24-ethyl-cholestane- 3β,5α,6α-triol).

e16531 Background: Hydroxysterols and oxysterols are oxygenated derivatives of cholesterol. They are involved in the regulation of some aspects of neoplastic cell growth and proliferation, as demonstrated in vitro in a variety of human cancer cells including prostate cancer cells.These effects can be dependent on the activation of the oxysterol-binding liver X receptors (LXRs). LNCaP prostate tumor cells stimulated with synthetic LXR agonists showed G1 to S-phase cell cycle arrest through the suppression of Skp2.Prostate cancer is the most frequent cancer in men and most patients become resistant to upfront treatments with hormones. At advanced stages most refractory patients are symptomatic and their life expectancy is limited. (24-ethyl-cholestane- 3β,5α,6α-triol) is a new hydroxysterol developed by us. It is the first oxysterol to be tested in the clinic. It is also one of the safest in this class of compounds. Methods: We have treated with this new drug 14 patients suffering from advanced and hormone-refractory prostate cancer (HRPC). Their median age was 73 (60-88). Seven with a Gleason 7, 5 with a Gleason 8 and 2 with a Gleason 9. Eleven had stage IV disease, Eight with bone metastasis, 4 with advanced loco-regional disease and 2 with visceral metastasis. Ten patients were symptomatic. Four patients had received also 1 line of chemotherapy and 2 others received 2 lines of chemo. Four patients were also previously treated with radiotherapy. Patients received daily 10 mg/Kg of oral (24-ethyl-cholestane- 3β,5α,6α-triol) divided into 3 equal doses, until disease progression. Results: Ten patients experienced either a biological or a radiological partial response (PR), Two patients had a stable disease (NC) and two patients had a disease progression (PD). The median duration of response was 2 years. Patients did not report any side-effect from treatment. Eighty percent of symptomatic patients had a remarkable symptom control. Conclusions: These encouraging results make this new and safe drug a good candidate for further clinical trials either alone or in combination with other drugs in the treatment of HRPC.

Determination of Cabazitaxel (An Anti-prostate cancer agent) by reverse phase liquid chromatography

Cabazitaxel is used in the treatment of hormone-refractory prostate cancer. It is a semisynthetic taxane that can be used as a precursor molecule obtained from yew tree needles. The authors have developed a stability indicating liquid chromatographic method for the determination of Cabazitaxel in pharmaceutical products. Shimadzu Model CBM-20A/20 Alite HPLC system (PDA detector) with Zorbax SB C18 column (150 mm × 4.6 mm i.d., 3.5 µm particle size) was selected for the quantification of Cabazitaxel. A mixture of tetra butyl ammonium hydrogen sulphate and methanol was used as the mobile phase with a flow rate of 1.0 mL/min (UV detection at 210 nm). The proposed analytical method was statistically validated and forced degradation studies were conducted. Cabazitaxel has shown linearity over the concentration range 0.1-200 µg/mL with regression equation y = 26145x + 22943 (r2=0.9997) and considerable degradation was observed in acidic, alkaline and oxidation conditions. The method is specific as the resolution of Cabazitaxelwas good in presence of its degradation products. This validated stability indicating liquid chromatographic method can be used for the determination of Cabazitaxel in biological studies as well as for the pharmaceutical products.

Bioactive natural products for chemoprevention and treatment of castration-resistant prostate cancer.

Prostate cancer (PCa), a hormonally-driven cancer, ranks first in incidence and second in cancer related mortality in men in most Western industrialized countries. Androgen and androgen receptor (AR) are the dominant modulators of PCa growth. Over the last two decades multiple advancements in screening, treatment, surveillance and palliative care of PCa have significantly increased quality of life and survival following diagnosis. However, over 20% of patients initially diagnosed with PCa still develop an aggressive and treatment-refractory disease. Prevention or treatment for hormone-refractory PCa using bioactive compounds from marine sponges, mushrooms, and edible plants either as single agents or as adjuvants to existing therapy, has not been clinically successful. Major advancements have been made in the identification, testing and modification of the existing molecular structures of natural products. Additionally, conjugation of these compounds to novel matrices has enhanced their bio-availability; a big step towards bringing natural products to clinical trials. Natural products derived from edible plants (nutraceuticals), and common folk-medicines might offer advantages over synthetic compounds due to their broader range of targets, as compared to mostly single target synthetic anticancer compounds; e.g. kinase inhibitors. The use of synthetic inhibitors or antibodies that target a single aberrant molecule in cancer cells might be in part responsible for emergence of treatment refractory cancers. Nutraceuticals that target AR signaling (epigallocatechin gallate [EGCG], curcumin, and 5α-reductase inhibitors), AR synthesis (ericifolin, capsaicin and others) or AR degradation (betulinic acid, di-indolyl diamine, sulphoraphane, silibinin and others) are prime candidates for use as adjuvant or mono-therapies. Nutraceuticals target multiple pathophysiological mechanisms involved during cancer development and progression and thus have potential to simultaneously inhibit both prostate cancer growth and metastatic progression (e.g., inhibition of angiogenesis, epithelial-mesenchymal transition (EMT) and proliferation). Given their multi-targeting properties along with relatively lower systemic toxicity, these compounds offer significant therapeutic advantages for prevention and treatment of PCa. This review emphasizes the potential application of some of the well-researched natural compounds that target AR for prevention and therapy of PCa.

MET expression during prostate cancer progression.

Tyrosine-kinase inhibitors of the hepatocyte growth factor receptor MET are under investigation for the treatment of hormone-refractory prostate cancer (HRPC) metastasis. Analysis of MET protein expression and genetic alterations might contribute to therapeutic stratification of prostate cancer patients. Our objective was to investigate MET on protein, DNA and RNA level in clinical prostate cancer at various stages of progression.Expression of MET was analyzed in hormone-naive primary prostate cancers (N=481), lymph node (N=40) and bone (N=8) metastases, as well as HRPC (N=54) and bone metastases (N=15). MET protein expression was analyzed by immunohistochemistry (D1C2 C-terminal antibody). MET mRNA levels and MET DNA copy numbers were determined by in situ hybridization.None of the hormone-naive primary prostate cancer or lymph node metastases demonstrated MET protein or mRNA expression. In contrast, MET protein was expressed in 12/52 (23%) evaluable HRPC resections. RNA in situ demonstrated cytoplasmic signals in 14/54 (26%) of the HRPC patients, and was associated with MET protein expression (p=0.025, χ2), in absence of MET amplification or polysomy. MET protein expression was present in 7/8 (88%) hormone-naive and 10/15 (67%) HRPC bone metastases, without association of HRPC (p=0.37; χ2), with MET polysomy in 8/13 (61%) evaluable cases.In conclusion, MET was almost exclusively expressed in HRPC and prostate cancer bone metastasis, but was not related to MET amplification or polysomy. Evaluation of MET status could be relevant for therapeutic stratification of late stage prostate cancer.

Docetaxel induces Bcl-2- and pro-apoptotic caspase-independent death of human prostate cancer DU145 cells.

Docetaxel is a useful chemotherapeutic agent for the first-line treatment of hormone-refractory prostate cancer. Abnormal expression of Bcl-2 is commonly found in cancer cells, which increases their anti-apoptotic potency and chemo-resistance. We investigated the effects of Bcl-2 expression status on the susceptibility of DU145 cells, an androgen-independent human prostate cancer cell line, to docetaxel and other anticancer agents. A panel of Bcl-2-expressing DU145 cell lines was established. Bcl-2 expression levels were unrelated to the susceptibility of DU145 cells to docetaxel. The sensitivity of DU145 cells to cisplatin fluctuated, and the sensitivity to tumor necrosis factor (TNF)-α was decreased by Bcl-2 overexpression. In a xenograft mouse model, overexpression of Bcl-2 drastically decreased the sensitivity of DU145 cells to cisplatin and TNF-α; however, there was no change in the response to docetaxel. Fluorescent microscopy revealed that Bcl-2-overexpression had no effect on the docetaxel-induced death of DU145 cells, but significantly decreased DU145 cell death induced by cisplatin or TNF-α. Interestingly, docetaxel hardly induced caspase-3/7 activation in control or Bcl-2-overexpressing DU145 cells, but did at a low level in LNCaP cells, another prostate cancer cell line. Moreover, in contrast to LNCaP cells, the reduced viabilities of docetaxel-treated control and Bcl-2-overexpressing DU145 cells were not restored by the addition of either a Bid inhibitor or a panel of pro-apoptotic caspase inhibitors. These findings indicate that the antitumor effects of docetaxel on DU145 cells are independent of both Bcl-2 and pro-apoptotic caspases.

Bortezomib and etoposide combinations exert synergistic effects on the human prostate cancer cell line PC-3.

Novel treatment modalities are urgently required for androgen-independent prostate cancer. In order to develop an alternative treatment for prostate cancer, the cytotoxic effects of the 26S proteasome inhibitor bortezomib, either alone or in combination with the two commonly used chemotherapeutic agents irinotecan and etoposide, on the human prostate cancer cell line PC-3 were evaluated in the present study. The PC-3 cell line was maintained in Dulbecco's modified Eagle's medium with 10% fetal bovine serum and treated with various doses of bortezomib, irinotecan, etoposide or their combinations. The growth inhibitory and cytotoxic effects were determined by water-soluble tetrazolium (WST)-1 assay, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay or iCELLigence system. The combination index values were determined by the Chou-Talalay method. The half maximal inhibitory concentration (IC50) value of bortezomib on the PC-3 cell line was determined to be 53.4 nM by WST-1 assay, whereas the IC50 values of irinotecan and etoposide were determined to be 2.1 and 26.5 µM, respectively. These results suggest that the 26S proteasome inhibitor bortezomib is more potent, compared with irinotecan and etoposide, in the androgen-insensitive and tumor protein p53-null cell line PC-3. The combined effects of bortezomib+irinotecan and bortezomib+etoposide were also tested on PC-3 cells. The effect of bortezomib+irinotecan combination was not significantly different than that produced by either monotherapy, according to the results of iCELLigence system and MTT assay. However, 40 nM bortezomib+5 µM etoposide or 40 nM bortezomib+20 µM etoposide combinations were observed to be more effective than each drug tested alone. The results of the current study suggest that bortezomib and etoposide combination may be additionally evaluated in clinical trials for the treatment of hormone-refractory prostate cancer.

Ligustrazine Suppresses the Growth of HRPC Cells through the Inhibition of Cap- Dependent Translation Via Both the mTOR and the MEK/ERK Pathways.

Ligustrazine (TMP) has recently been used for the treatment of various cancers. However, its exact mechanisms of action, particularly the functions and the mechanisms of Ligustrazine in human hormone-refractory prostate cancer (HRPC), have not yet been extensively studied. Recently, our findings suggest that Ligustrazine dose- and time-dependently inhibits the growth of HRPC cells by reducing their proliferation and promoting apoptosis. Interestingly, the treatment of hormone-refractory prostate cancer (PC-3) cells with Ligustrazine results in a significant inhibition of the activation of mTOR and related downstream targets, which are critical for cell growth. Furthermore, pull-down assays with 7-methyl- GTP Sepharose 4B beads indicate that Ligustrazine reduces the available eIF4E for translation initiation. Accordingly, the results from the translation assay using a luciferase reporter system further demonstrate that Ligustrazine indeed inhibits cap-dependent translation. In addition, the transient overexpression of eIF4E or MNK1 prevents the Ligustrazine-induced inhibition of proliferation and confers significant protection against Ligustrazine-induced apoptosis. Therefore, the present study provides evidences that Ligustrazine may be a candidate for therapeutic reagent for the treatment of HRPC and certifies that Ligustrazine modulates the availability of eIF4E mainly through the mTOR and MEK/ERK signaling pathways to inhibit cap-dependent translation. Taken together, our results indicate that the inhibition of cap-dependent translation is likely an essential mechanism in Ligustrazine-induced apoptosis.

Paradoxical and contradictory effects of imatinib in two cell line models of hormone-refractory prostate cancer.

Imatinib mesylate is a chemotherapeutic drug that inhibits the tyrosine kinase activity of c-KIT and has been successfully used to treat leukemias and some solid tumors. However, its application for treatment of hormone-refractory prostate cancer (HRPC) has shown modest effectiveness and did not follow the outcomes in cultured cells or animal models. Moreover, the molecular pathways by which imatinib induces cytotoxicity in prostate cancer cells are poorly characterized. Two cell line models of HRPC (DU145 and PC3) were exposed to 20 μM of imatinib for 6-72 hr. MTS assay was used to assess cell viability during the course of experiment. Gene expression analysis of c-KIT, cell-cycle and apoptosis regulators, and angiogenic factors was determined by means of real-time PCR, western blot, and/or immunocytochemistry. The enzymatic activity of the apoptosis effector, caspase-3, was determined by a colorimetric assay. Imatinib significantly decreased the viability of DU145 cells but paradoxically augmented the viability of PC3 cells. DU145 cells displayed diminished expression of anti-apoptotic Bcl-2 protein and augmented levels of caspase-8 and -9, as well as, increased enzymatic activity of caspase-3 in response to imatinib. No differences existed on the expression levels of apoptosis-related proteins in PC3 cells treated with imatinib, though the activity of caspase-3 was decreased. The mRNA levels of angiogenic factor VEGF were decreased in DU145-treated cells, whereas an opposite effect was seen in PC3. In addition, it was shown that DU145 and PC3 cells present a differential expression of c-KIT protein variants. DU145 and PC3 cells displayed a contradictory behavior in response to imatinib, which was underpinned by a distinct expression pattern (or activity) of target regulators of cell-cycle, apoptosis, and angiogenesis. The paradoxical effect of imatinib in PC3 cells may be related with the differential expression of c-KIT protein variants. Moreover, the present findings helped to understand the discrepancies in the efficacy of imatinib as therapeutic option in HRPC.

Camptothecin and taxol – from nature to bench to bedside

Camptothecin (CPT) and taxol are secondary metabolites found, respectively, in the wood bark of Camptotheca acuminata, a native of China, and Taxus brevifolia, found in the Pacific north-west coastal region of the USA. The compounds were isolated by the bioassay-guided fractionation of the crude plant material and their structures established by single crystal X-ray analysis. Both compounds have unique mechanisms of antitumour activity. Camptothecin inhibits an enzyme, topoisomerase I, involved in DNA replication. Taxol binds to a protein, tubulin, thus inhibiting cell division. Currently, two analogues of camptothecin, topotecan (Hycamtin®, GlaxoSmithKline, Brentford, UK) and irinotecan (Campto®, Pfizer Ltd, New York, NY, USA), and taxol and its analogues, docetaxel (Taxotere®, Sanofi-Aventis Ltd, Guilford, UK) and cabazitaxel (Jevtana®, Sanofi-Aventis Ltd, Guilford, UK), are approved for clinical use in the USA by the Food and Drug Administration (FDA). The camptothecin analogues are used to treat ovarian, colorectal and small-cell lung cancers. Taxol is used extensively to treat refractory ovarian, breast and non-small-cell lung cancers and Kaposi ’ s sarcoma. Docetaxel has been a very important drug for the treatment of breast cancer and cabazitaxel is FDA approved for the treatment of hormone-refractory prostate cancer.

Bcl-2 family inhibition sensitizes human prostate cancer cells to docetaxel and promotes unexpected apoptosis under caspase-9 inhibition.

Docetaxel (DTX) is a useful chemotherapeutic drug for the treatment of hormone-refractory prostate cancer. However, emergence of DTX resistance has been a therapeutic hurdle. In this study, we investigated the effect of combining DTX with Bcl-2 family inhibitors using human prostate cancer cell lines (PC3, LNCaP, and DU145 cells). PC3 cells were less sensitive to DTX than were the other two cell lines. In contrast to ABT-199, which inhibits Bcl-2 and Bcl-w, both ABT-263 and ABT-737, which inhibit Bcl-2, Bcl-xL, and Bcl-w, significantly augmented the antitumor effect of DTX on PC3 cells. ABT-263 also enhanced the antitumor effect of DTX on a DTX-resistant PC3 variant cell line. The antitumor effect of ABT-263 was due mainly to its inhibitory effect on Bcl-xL. In a xenograft mouse model, DTX and ABT-737 combination therapy significantly inhibited PC3 tumor growth. Interestingly, although ABT-263 activated caspase-9 in PC3 cells, inhibition of caspase-9 unexpectedly promoted ABT-263-induced apoptosis in a caspase-8-dependent manner. This augmented apoptosis was also observed in LNCaP cells. These findings indicate that Bcl-xL inhibition can sensitize DTX-resistant prostate cancer cells to DTX, and they reveal a unique apoptotic pathway in which antagonism of Bcl-2 family members in caspase-9-inhibited prostate cancer cells triggers caspase-8-dependent apoptosis.

The use of LC-MS to identify differentially expressed proteins in docetaxel-resistant prostate cancer cell lines

Docetaxel is a taxane-derived chemotherapy drug that has been approved for treatment of prostate cancer. While docetaxel is frequently used as a treatment for hormone-refractory prostate cancer, a subset of patients either do not respond to this treatment or those that do respond eventually become resistant to the drug over time. Resistance to docetaxel is complex and multi-factoral and further understanding of the cellular biochemistry underlying resistance is vital to improve treatment efficacy. To identify proteins altered in the resistant phenotype, three parental cell lines DU145, 22RV1 and PC-3, as well as their docetaxel resistant sub-lines, were subjected to quantitative label-free LC-MS proteomic profiling. A total of 189 significant (p < 0.05) protein abundance changes were identified in the DU145 resistant sub-lines, 254 in the 22RV1 sub-lines, and 51 and 72 in the 8 and 12 nM resistant PC-3 sub-lines, respectively. From these, 29 proteins demonstrated a significant (p < 0.05) fold change across two or more resistant variants. These included proteins indicative of an epithelial-to-mesenchemyl transition as well as altered heat shock response elements.

Abstract 4826: A therapeutic sphingosine 1-phosphate antibody improves intratumoral oxygenation and sensitizes to chemotherapy in prostate cancer animal model

Abstract Hypoxia promotes neovascularization, metastasis, and resistance to treatments. The activation of the transcription factor HIF-1α has been identified as the master mechanism of adaptation to hypoxia. We recently identified the sphingosine kinase 1/sphingosine 1-phosphate (SphK1/S1P) pathway as a new modulator of HIF-1α activity under hypoxia in multiple cancer cell models including prostate cancer (Ader et al, Cancer Res, 2008). S1P elicits proliferation, survival, or angiogenesis, and is believed to exert most of its actions as a ligand for a family of specific GPCRs to elicit paracrine or autocrine signaling. We have suggested that inhibiting SphK1/S1P signaling, which is upregulated under hypoxia, may normalize the microenvironment and increase sensitivity to chemotherapy, in the broader concept of “normalization of tumor vessels” as tumor oxygenation is known to enhance response to chemotherapy (Ader et al., Cancer Res, 2009). Methods: Quantification of intratumoral hypoxia and angiogenesis, and treatment efficacy (primary tumor, metatasis dissemination) using an orthotopic (o.t) xenograft model of fluorescent hormone refractory prostate cancer cells. Results: We first provide in vitro evidence that inhibition of the S1P exogenous signaling, through pharmacological inhibition of its receptors or by taking advantage of a monoclonal antibody neutralizing S1P, blocks HIF-1α accumulation and its activity in prostate cancer cells under to hypoxia. Second, using an o.t model of prostate cancer, we show that an anti-S1P antibody inhibits intratumoral hypoxia and modifies vessel architecture and improves tumor perfusion within 5 days of treatment. Third, we show for the first time that an anti-S1P strategy sensitizes to docetaxel, the ‘gold standard’ treatment for hormone-refractory prostate cancer. A 5-day anti-S1P antibody pretreatment markedly sensitizes to docetaxel in an o.t. PC-3/GFP model established in nude mice. The combination anti-S1P antibody together with docetaxel was not only accompanied by a smaller primary tumor volume compared to docetaxel treatment, but also significantly reduced the occurrence and number of metastases. Conclusion: These preclinical data establish the proof-of-concept that blocking the exogenous action of S1P induces vascular normalization, improves intratumoral oxygenation and sensitizes to chemotherapy in prostate cancer animal model. 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 4826. doi:1538-7445.AM2012-4826

Protein BIII-tubulin expression as a prognostic and/or predictive factor of response to docetaxel in patients with hormone-refractory prostate cancer.

84 Background: Docetaxel is a standard treatment for hormone-refractory prostate cancer. Preclinical-clinical studies suggest that the determination of the BIII-tubulin is associated with response to taxanes. This study analyzes the role of that subunit of microtubules in prostate biopsies of patients with HRPC treated with docetaxel. Methods: Thirty two patients with prostate biopsy who received docetaxel in first-line chemotherapy between 2006 and 2011 were included in this retrospective cohort analysis. The clinic-pathological characteristics, PSA response, progression-free survival (PFS) and overall survival (OS) were collected. The findings were correlated with the overexpression of BIII-tubulin protein measured by immunohistochemistry techniques (IHC) with a purified and monoclonal Ac mouse. Results: The median age and Karnofstky index (KI) were 68 years (range 49-77) and 80% (60-90) respectively. Five patients (15.6%) had received only one anti-hormone treatment, fifteen (46.8), two and twelve (37.5) more than two lines. Twenty patients (62.5) had only one metastatic localization. The median of PSA value before the docetaxel treatment was 302 (4-3745). With a median of eight cycles (3-10) of docetaxel (75mg/m2/ /3s) 41% of patients achieved biochemical response with a median PFS and OS of 4.9 and 19.6 months respectively. Moderate-intense overexpression of BIII-tubulin was identified in five patients (15.6) and minimal or absent in 27 (84.4). In univariate analysis, over-expression was correlated with KI, but not with Gleason score. PSA responses to docetaxel was observed in four patients (80%) with over-expression compared with 20% of those with minimal or absent BIII-tubulin staining. The median PFS and OS for patients with over-expression was 8.6 and 20 months respectively compared to 4.3 and 17 months for those with minimal or absent BIII-tubulin. Conclusions: Over-expression of BIII-tubulin in tumor prostate tissue, applying the present technique is unusual. Its presence appears to be related with higher biochemical response to docetaxel and improvement in PFS and OS. These findings are discordant with those previously published.

Localized but Biochemicaly Progressing Prostate Cancer Under Long-Term Hormonal Ablation Treated by Therapeutic High-Intensity Focal Robotic Ultrasound

Treatment of hormone-refractory prostate cancer (HRPCa) is challenging and rewarding at the same time. Use of high-intensity focal ultrasound (HIFU) as primary prostate cancer therapy is still judged to be experimental, ignoring the fact that already more than 30.000 men worldwide have been treated and that 10 years data are available. Early onset of androgen deprivation therapy (ADT) and general longer patient survival lead to an increase in the number of patients requiring post-hormonal therapy resulting in increasing numbers of biochemical PSA relapse after few years.

The TORC1/TORC2 inhibitor, Palomid 529, reduces tumor growth and sensitizes to docetaxel and cisplatin in aggressive and hormone-refractory prostate cancer cells

One of the major obstacles in the treatment of hormone-refractory prostate cancer (HRPC) is the development of chemo-resistant tumors. The aim of this study is to evaluate the role of Palomid 529 (P529), a novel TORC1/TORC2 inhibitor, in association with docetaxel (DTX) and cisplatin (CP). This work utilizes a wide panel of prostatic cancer cell lines with or without basal activation of Akt as well as two in vivo models of aggressive HRPC. The blockade of Akt/mTOR activity was associated to reduced cell proliferation and induction of apoptosis. Comparison of IC50 values calculated for PTEN-positive and PTEN-negative cell lines as well as the PTEN transfection in PC3 cells or PTEN silencing in DU145 cells revealed that absence of PTEN was indicative for a better activity of the drug. In addition, P529 synergized with DTX and CP. The strongest synergism was achieved when prostate cancer (PCa) cells were sequentially exposed to CP or DTX followed by treatment with P529. Treatment with P529 before the exposure to chemotherapeutic drugs resulted in a moderate synergism, whereas intermediated values of combination index were found when drugs were administered simultaneously. In vivo treatment of a combination of P529 with DTX or CP increased the percentage of complete responses and reduced the number of mice with tumor progression. Our results provide a rationale for combinatorial treatment using conventional chemotherapy and a Akt/mTOR inhibitor as promising therapeutic approach for the treatment of HRPC, a disease largely resistant to conventional therapies.

The significance of Her2 on androgen receptor protein stability in the transition of androgen requirement in prostate cancer cells

Androgen ablation therapy is the most common strategy for suppressing prostate cancer progression; however, tumor cells eventually escape androgen dependence and progress to an androgen-independent phase. The androgen receptor (AR) plays a pivotal role in this transition. To address this transition mystery in prostate cancer, we established an androgen-independent prostate cancer cell line (LNCaPdcc), by long-term screening of LNCaP cells in androgen-deprived conditions, to investigate changes of molecular mechanisms before and after androgen withdrawal. We found that LNCaPdcc cells displayed a neuroendocrine morphology, less aggressive growth, and lower expression levels of cell cycle-related factors, although the cell cycle distribution was similar to parental LNCaP cells. Notably, higher protein expression of AR, phospho-Ser(81)-AR, and PSA in LNCaPdcc cells were observed. The nuclear distribution and protein stability of AR increased in LNCaPdcc cells. In addition, cell proliferation results exhibited the biphasic nature of the androgen (R1881) effect in two cell lines. On the other hand, LNCaPdcc cells expressed higher levels of Her2, phospho-Tyr(1221/1222)-Her2, ErbB3, and ErbB4 proteins than parental LNCaP cells. These two cell lines exhibited distinct responses to Her2 activation (by heregulin treatment) on Her2 phosphorylation and Her2 inhibition (by AG825 or Herceptin treatments) on proliferation. In addition, the Her2 inhibitor more effectively caused AR degradation and diminished AR Ser(81) phosphorylation in LNCaPdcc cells. Taken together, our data demonstrate that Her2 plays an important role in the support of AR protein stability in the transition of androgen requirement in prostate cancer cells. We hope these findings will provide novel insight into the treatment of hormone-refractory prostate cancer.

Discovery of a novel AR pure antagonist (ZR291) for the treatment of hormonerefractory prostate cancer (HRPC)

Discovery of a novel AR pure antagonist (ZR291) for the treatment of hormonerefractory prostate cancer (HRPC)