Hormone-resistant Prostate Cancer Research Articles

78P - Immunotherapy enhanced by geroprotection: Hormone-resistant prostate cancer

78P - Immunotherapy enhanced by geroprotection: Hormone-resistant prostate cancer

Development of New Gonadotropin-Releasing Hormone-Modified Dendrimer Platforms with Direct Antiproliferative and Gonadotropin Releasing Activity.

Gonadotropin-releasing hormone (GnRH) agonists (e.g., triptorelin) are used for androgen suppression therapy. They possess improved stability as compared to the natural GnRH, yet they suffer from a poor pharmacokinetic profile. To address this, we used a GnRH peptide-modified dendrimer platform with and without lipidation strategy. Dendrimers were synthesized on a polylysine core and bore either native GnRH (1, 2, and 5) or lipid-modified GnRH (3 and 4). Compound 3, which bore a lipidic moiety in a branched tetramer structure, showed approximately 10-fold higher permeability and metabolic stability and 39 times higher antitumor activity against hormone-resistant prostate cancer cells (DU145) relative to triptorelin. In gonadotropin-release experiments, dendrimer 3 was shown to be the most potent construct. Dendrimer 3 showed similar luteinizing hormone (LH)-release activity to triptorelin in mice. Our findings indicate that dendrimer 3 is a promising analog with higher potency for the treatment of hormone-resistant prostate cancer than the currently available GnRH agonists.

Chlorine dioxide as a possible adjunct to metabolic treatment

A first patient with metastatic adenocarcinoma of the pancreas has decided, on his own, to refuse chemotherapy but to treat himself with lipoic acid, hydroxycitrate combined with oral ingestion of chlorine dioxide. His blood tests and radiological examinations have almost normalized and the disease is stable at 18 months. Another patient with hormone resistant metastatic prostate cancer has experienced a sharp drop in PSA level as well as improved medical condition. From extensive literature review, the mechanism of action of chlorine dioxide is unknown. It is our hypothesis (albeit unproven) that chlorine dioxide results in tumor cell acidification of the alkaline pH of cancer cells.

Aristeromycin and DZNeP cause growth inhibition of prostate cancer via induction of mir-26a

Most prostate cancers initially respond to androgen deprivation therapy, but then progress from androgen-dependent to androgen-independent prostate cancers. In the present study, a differential cytotoxicity screen of hormone-resistant prostate cancer LNCaP-hr cells and the parental LNCaP-FGC cells against normal MRC5 fibroblast cells, identified a small molecule compound, Aristeromycin (a derivative of 3-deazaneplanocin A (DZNeP)). The molecular target was shown to be S-adenosylhomocysteine hydrolase (AHCY), which catalyzes reversible hydrolysis of S-adenosylhomocysteine (SAH) to adenosine and L-homocysteine. DZNeP and Aristeromycin showed high inhibitory activity against AHCY. Treatment of the prostate cancer cells with DZNeP led to SAH accumulation and decreased levels of homocysteine and histone H3K27 methylation. SAH accumulation and cell growth inhibition were confirmed after siRNA-mediated AHCY knockdown. To further understand why AHCY inhibitors decreased prostate cancer cell growth, we performed microRNA expression profiling with LNCaP-hr cells. Mir-26a, which is involved in regulation of EZH2 expression, was upregulated in Aristeromycin-treated LNCaP-hr cells. A reporter assay established with the EZH2 3′-UTR confirmed that transfection of microRNA precursor molecules for miR-26a decreased the EZH2 3′-UTR luciferase activity. Meanwhile, an antisense microRNA inhibitor for miR-26a recovered the luciferase activity. The present findings suggest, at least in part, that miR-26a induced by an AHCY inhibitor can regulate oncogenic EZH2 expression, and could thus be an important mechanism of action for AHCY inhibitors in the treatment of prostate cancer.

Combination of RAD001 (everolimus) and docetaxel reduces prostate and breast cancer cell VEGF production and tumour vascularisation independently of sphingosine-kinase-1

Resistance to docetaxel is a key problem in current prostate and breast cancer management. We have recently discovered a new molecular mechanism of prostate cancer docetaxel chemoresistance mediated by the mammalian target of rapamycin (mTOR)/sphingosine-kinase-1 (SK1) pathway. Here we investigated the influence of this pathway on vascular endothelial growth factor (VEGF) production and tumour vascularisation in hormone resistant prostate and breast cancer models. Immunofluorescent staining of tumour sections from human oestrogen receptor (ER)-negative breast cancer patients showed a strong correlation between phosphorylated P70S6 kinase (mTOR downstream target), VEGF and SK1 protein expression. In hormone-insensitive prostate (PC3) and breast (MDA-MB-231 and BT-549) cancer cell lines the mTOR inhibitor RAD001 (everolimus) has significantly inhibited SK1 and VEGF expression, while low dose (5 nM) docetaxel had no significant effect. In these cell lines, SK1 overexpression slightly increased the basal levels of VEGF, but did not block the inhibitory effect of RAD001 on VEGF. In a human prostate xenograft model established in nude mice, RAD001 alone or in combination with docetaxel has suppressed tumour growth, VEGF expression and decreased tumour vasculature. Overall, our data demonstrate a new mechanism of an independent regulation of SK1 and VEGF by mTOR in hormone-insensitive prostate and breast cancers.

Anticancer applications of allosteric inhibitors of proteasome.

e23066 Background: Proteasome as a hub protease of the ubiquitin proteasome pathway is an established anticancer drug target. Several drugs that inhibit proteasome are currently used to successfully treat aggressive blood cancers. These drugs are based on their competition with protein substrates of proteasome. However, efficacy of these drugs toward solid cancers is inadequate. Besides, the side effects and developing drug resistance are increasingly hampering the therapy. Therefore, there is an unmet challenge to develop new types of proteasome targeting compounds that are efficient against solid cancers and utilize other mechanisms to stop proteasome. Here we present a compound with a novel molecular mechanism, potentially bypassing limitations of the available drugs. Methods: We rationally designed and synthesized a series of small molecule “B” compounds, derivatives of a binding domain of seco-rapamycin that noncompetitively interfere with peptidase activities of proteasome. We tested effects of the compounds in vitro on purified proteasome, in cellulo with selected cancer cell lines and in a xenograft mouse model of prostate cancer. Results: We found that compound B1 binds to the catalytic core of proteasome far from the catalytic sites, destabilizes assembly of the 26S proteasome responsible for digest of polyUb substrates and allosterically inhibits its proteolytic activities. Molecularly, B1 impedes the gating mechanism responsible for substrate uptake as found with AFM. Tryptophan fluorescence indicates that B1 changes proteasome fold and the binding mode of competitive inhibitors. B1 substantially decreases viability of selected cancer cell lines and shifts their mechanical phenotype toward noncancerous status. B1 synergizes with bortezomib decreasing the IC50 5-10 fold. In a xenograft hormone resistant prostate cancer model, B1 treatment leads to shrinkage of the tumor size, decreases enumeration of aggressive, EpCAM+ CTCs and shifts the macrophage profile toward predator M1 type. Conclusions: B1 compounds constitute a new class of noncompetitive allosteric inhibitors of proteasome that could be useful to develop to treat aggressive prostate cancers alone or in synergy with competitive inhibitors.

296P Efficiency of intermittent androgen blockade in patients with advanced prostate cancer

Background One of the methods to prevent the development of hormone-resistant prostate cancer (PC) is intermittent androgen blockade (IAB). The concept of IAB is in a temporary androgen blockade, in which stem tumor cells are partially preserved. When a certain response is achieved, antiandrogen therapy is stopped to allow the growth of new clones of androgen-sensible cancer cells. Then treatment is resumed. The mechanism of this method is based on the activity of the remaining stem tumor cells, which cause the growth of androgen-dependent colony, receptive to re-hormonal treatment. Methods The study included 235 patients with advanced prostate cancer who were treated at the City Cancer Center, Tashkent city. Patients were divided into 2 groups: group 1(n = 49) - patients underwent surgical castration; group 2(n = 186) - patients received combined hormone therapy. All patients from group 2 were treated in the mode of intermittent therapy with - LHRH agonist - goserelin acetate 3.6 mg in the form of a depot injection 1 time per month and the injection form of cyproterone acetate 300 mg 2 times a month in combination with bisphosphonates. Results The study included 235 patients with advanced prostate adenocarcinoma. In group1 (n=49),wherepatientsreceivedorchiectomy,theaverageageofpatientswas 77.0861.12years.In18patients(36.766.88%) theprevalenceoftumorprocesswas T2NxMx,26patients(53.167.12%)-T3NxMx,5patients(10.264.32)-T3NxMx.19 patients (38.7 6 6.96%) were detected to have skeletal bone metastases, retroperitoneal and iliac lymph nodes. Conclusions The results of our research confirm the effectiveness of hormone therapy IAB in comparison with the traditional method of surgical castration. Our certain methods of selecting the optimal mode of hormonal therapy, depending on prognostic factors has led to improved health outcomes and quality of life of patients with advanced prostate cancer. Herewith, determination of the period of the second cycle start of hormone therapy is decided individually for each patient based on the PSA level before treatment and on the extent of tumor spread, dynamics of clinical symptoms, tolerance to androgen blockade. Legal entity responsible for the study Yusupov Sherali Khasanovich Funding Tashkent city oncology dispanser Disclosure All authors have declared no conflicts of interest.

Comparison of the effect of multidrug resistance modifiers on prostate cancer, mouse lymphoma and colon cancer cells

The reason for unsuccessful tumor chemotherapy is related to multidrug resistance. An important factor is the overexpression of efflux pumps, such as P-glycoprotein. Amino- and amide-substituted steroid compounds and phenothiazine derivatives were investigated in tumor models in vitro. The inhibition of P-glycoprotein was evaluated by flow cytometry and the interaction of these compounds with doxorubicin was investigated as well. Molecular docking was used to estimate the binding energies of the compounds to P-glycoprotein. The aminosteroids showed anticancer activity on multidrug resistant mouse T-lymphoma and prostate cancer cell lines. The combination of steroids and doxorubicin potentiated its effect in hormone resistant prostate cancer cells. Among the N-hydroxyalkyl-2-aminophenothiazines, secondary amines exhibited anticancer effects on multidrug resistant colon adenocarcinoma cells. The tested phenothiazine and steroid derivatives showed potent anticancer activity, furthermore, the stereoisomerism of thioridazine did not play a role in the antitumor properties. Neither steroids nor thioridazine influenced apoptosis in hormone resistant cells. Orv. Hetil., 2016, 157(37), 1489-1495.

Abstract 23: Caloric restriction slows tumor growth and metastases in both hormone-sensitive and hormone-resistant prostate cancers

Abstract Introduction: The purpose of this study is to assess the effect of caloric restriction (CR) on prostate cancer (PCa) tumor burden, proliferation, and overall survival with and without radiation treatment (RT). Additionally, we determined if the beneficial effect of CR noted are due to a reduction in pro-inflammatory markers hypothesized to enhance PCa tumorgenesis. Methods: To assess the effect of CR in vivo, 40 male 12 week-old NCRNu-M mice were injected with LNCaP or PC3 tumor cells. Once tumors were palpable, mice were randomly assigned to one of four treatment groups in cohorts of 10: ad libitum (AL) diet, 6.5Gy of radiation (RT), 30% reduction in caloric intake (CR), or CR+RT. Tumor growth and proliferation rate were measured 3 times per week via calipers and live bioluminescent imaging. Additionally, PCa tumor tissue were analyzed to determine if CR can exert its effect on tumor growth and metastases via IGF-1R signaling pathway. Results: Adding CR to RT decreased tumor progression. In the PC3 murine model, when compared to AL, RT reduced tumor size by 22%, 77% with CR, and 80% with CR+RT. In the LNCaP murine model, compared with AL, CR reduced tumor size by 49% and a 55% reduction with CR+RT. Primary tumor formation began 9 weeks post tumor injection in the radiated cohort and was delayed to 15 weeks post tumor injection in the CR and CT+ RT cohorts. Additionally, time to metastasis was delayed with CR (86 days to metastasis in AL, 93 with RT, and 108 when combining CR+RT). Molecularly, CR decreased multiple members of the IGF-1R signaling pathway. The total IGF-1 and IGF-1R levels exhibited 50% reduction with CR and CR+RT but total INSR levels. CR also induced a significant decrease of pGSK3β and pAKT levels. Conclusions: For the first time, we have shown that decreasing calories by 30% in both hormone-sensitive and hormone-refractory prostate cancer models, enhance the efficacy of radiation. Our experiments show that even CR alone and in combination with RT can improve PCa tumor proliferation rate, tumor burden, time to metastasis, and overall survival. We hypothesize that these changes are in part, due to the decrease of the IGF-1R signaling pathway. We propose that CR may be used as a novel therapeutic intervention to enhance outcomes of radiation treatment by altering the molecular profile of prostate tumors. Citation Format: Robert S. Gitman, Meredith LaRose, Edouard J. Trabulsi, Ajay Palagani, Tiziana DeAngelis, William K. Kelly, Leonard G. Gomella, Nicole L. Simone. Caloric restriction slows tumor growth and metastases in both hormone-sensitive and hormone-resistant prostate cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 23.

Neuronal Trans-Differentiation in Prostate Cancer Cells.

Neuroendocrine (NE) differentiation in prostate cancer (PCa) is an aggressive phenotype associated with therapy resistance. The complete phenotype of these cells is poorly understood. Clinical classification is based predominantly on the expression of standard NE markers. We analyzed the phenotype of NE carcinoma of the prostate utilizing in vitro methods, in silico, and immunohistochemical analyses of human disease. LNCaP cells, subjected to a variety of stressors (0.1% [v/v] fetal bovine serum, cyclic AMP) induced a reproducible phenotype consistent with neuronal trans-differentiation. Cells developed long cytoplasmic processes resembling neurons. As expected, serum deprived cells had decreased expression in androgen receptor and prostate specific antigen. A significant increase in neuronal markers also was observed. Gene array analysis demonstrated that LNCaP cells subjected to low serum or cAMP showed statistically significant manifestation of a human brain gene expression signature. In an in silico experiment using human data, we identified that only hormone resistant metastatic prostate cancer showed enrichment of the "brain profile." Gene ontology analysis demonstrated categories involved in neuronal differentiation. Three neuronal markers were validated in a large human tissue cohort. This study proposes that the later stages of PCa evolution involves neuronal trans-differentiation, which would enable PCa cells to acquire independence from the neural axis, critical in primary tumors. Prostate 76:1312-1325, 2016. © 2016 Wiley Periodicals, Inc.

Radiosensitization by the investigational NEDD8-activating enzyme inhibitor MLN4924 (pevonedistat) in hormone-resistant prostate cancer cells.

Salvage radiotherapy (SRT) is the first-line treatment for prostate cancer patients with biochemical recurrence following radical prostatectomy, and new specific radiosensitizers are in urgent need to enhance SRT effect. MLN4924 (also known as Pevonedistat), a specific inhibitor of NEDD8-activating enzyme, has recently entered phase I/II clinical trials in several malignancies. By inhibiting cullin neddylation, MLN4924 inactivates Cullin-RING ligases (CRL), which have been validated as an attractive radiosensitizing target. In our study, we demonstrate that MLN4924 can be used as a potent radiosensitizer in hormone-resistant prostate cancer cells. We found that MLN4924 inhibited cullin neddylation and sensitized prostate cancer cells to irradiation (IR). Mechanistically, MLN4924 enhanced IR-induced G2 cell-cycle arrest, by inducing accumulation of WEE1/p21/p27, three well-known CRL substrates. Importantly, siRNA knockdown of WEE1/p21/p27 partially abrogated MLN4924-induced G2 cell-cycle arrest, indicating a causal role of WEE1/p21/p27 in MLN4924-induced radiosensitization. Further mechanistic studies revealed that induction of DNA damage and apoptosis also contributed to MLN4924 radiosensitization in hormone-resistant prostate cancer cells. Our findings lay the foundation for future application of MLN4924 as a potential radiosensitizer in hormone refractory prostate cancer (HRPC).

Effect of caloric restriction on the efficacy of radiation in both hormone-sensitive and hormone-resistant prostate cancers.

16 Background: Locally advanced prostate cancers (LAPC) are aggressive, have poor prognosis, and are associated with high recurrence rates and conversion to castrate resistance. The molecular underpinnings of LAPC are being investigated to identify novel therapeutics. Animal models have shown that caloric restriction (CR) can potentially prevent the initiation of prostate cancer. We propose that CR may be used as a novel therapeutic intervention to enhance outcomes of radiation treatment by altering the molecular profile of prostate tumors. Methods: To assess the effect of CR with radiation in vivo, 6 week old male nude mice were injected with LNCaP (hormone sensitive, N = 60) or PC3 (hormone refractory, N = 60) tumor cells. Once tumors were palpable, mice were randomized to be treated with one of 4 conditions: ad libitum (AL) diet, 8Gy of radiation (RT), 30% reduction in caloric intake (CR), or CR+RT. Results: After PC3 tumor injection, compared with AL, the mice had a 22% reduction in tumor size with radiation, 77% with CR (p < 0.01) and an 80% reduction with CR+RT (p < 0.01). After LNCaP tumor injection, compared with ad libitum, the mice had a 49% reduction in tumor size with CR and a 55% reduction with CR+RT (p < 0.01). Tissue evaluation of mice treated with CR or CR+RT from both the LNCaP and PC3 models revealed decreased proliferation via Ki-67 and increased apoptosis with cleaved caspase-3 levels. Furthermore we establish significant changes of the pro-inflammatory IGF-1R pathway hypothesized to play in intricate roll in prostate cancer; down regulation of serum IGF-1R, IRS-1, PI3K, pAKT, and IGF-1:IGF-BP3. Conclusions: For the first time, we have shown that the efficacy of radiation can be increased by decreasing calories by 30% in both hormone-sensitive and hormone-refractory prostate cancer models. Future clinical trials should consider the innovative use of CR to augment standard cancer therapy as it has the potential to change the biology of tumors and enhance the opportunity for clinical benefit.

A biomimetic approach to hormone resistant prostate cancer cell isolation using inactivated Sendai virus (HVJ-E).

Our study reports a versatile immobilization method of Hemagglutinating Virus of Japan Envelope (HVJ-E) for the generation of viral-mimetic surfaces for hormone resistant prostate cancer cell isolation. HVJ-E has recently attracted much attention as a new type of therapeutic material because hormone resistant prostate cancer cells such as PC-3 cells possess the HVJ-E receptors, GD1a. The HVJ-E was successfully immobilized on precursor films composed of poly-l-lysine and alginic acid via layer-by-layer assembly without changing the biological activity. The monolayer adsorption of HVJ-E particles was confirmed by quartz crystal microbalance, fluorescent and atomic force microscopy analyses. By developing the HVJ-E coating with an affinity based cell trap within a glass capillary tube, we are able to gently isolate PC-3 from LN-Cap cells that represent adenocarcinoma without compromising cell viability. We achieved approximately 100% cell separation efficiency only by 60 seconds of flowing. We believe that the proposed technique offers significant promise for the creation of a hormone resistant cancer cell trap on a broad range of materials.

Theranostic hollow/mesoporous organosilica nanospheres enhance the therapeutic efficacy of anticancer drugs in metastatic hormone-resistant prostate cancer

Hollow mesoporous silica materials have received intensive interest in the field of cancer treatment owing to their large drug loading capacity, controlled release property and excellent biocompatibility.

Cyclin D1 silencing suppresses tumorigenicity, impairs DNA double strand break repair and thus radiosensitizes androgen-independent prostate cancer cells to DNA damage.

Patients with hormone-resistant prostate cancer (PCa) have higher biochemical failure rates following radiation therapy (RT). Cyclin D1 deregulated expression in PCa is associated with a more aggressive disease: however its role in radioresistance has not been determined. Cyclin D1 levels in the androgen-independent PC3 and 22Rv1 PCa cells were stably inhibited by infecting with cyclin D1-shRNA. Tumorigenicity and radiosensitivity were investigated using in vitro and in vivo experimental assays. Cyclin D1 silencing interfered with PCa oncogenic phenotype by inducing growth arrest in the G1 phase of cell cycle and reducing soft agar colony formation, migration, invasion in vitro and tumor formation and neo-angiogenesis in vivo. Depletion of cyclin D1 significantly radiosensitizes PCa cells by increasing the RT-induced DNA damages by affecting the NHEJ and HR pathways responsible of the DNA double-strand break repair. Following treatment of cells with RT the abundance of a biomarker of DNA damage, γ-H2AX, was dramatically increased in sh-cyclin D1 treated cells compared to shRNA control. Concordant with these observations DNA-PKcs-activation and RAD51-accumulation, part of the DNA double-strand break repair machinery, were reduced in shRNA-cyclin D1 treated cells compared to shRNA control. We further demonstrate the physical interaction between CCND1 with activated-ATM, -DNA-PKcs and RAD51 is enhanced by RT. Finally, siRNA-mediated silencing experiments indicated DNA-PKcs and RAD51 are downstream targets of CCND1-mediated PCa cells radioresistance. In summary, these observations suggest that CCND1 is a key mediator of PCa radioresistance and could represent a potential target for radioresistant hormone-resistant PCa.

Up-Regulation of LAT1 during Antiandrogen Therapy Contributes to Progression in Prostate Cancer Cells

Cancer cells require massive amounts of amino acids for survival. LAT1 (L-type amino acid transporter 1) transports essential amino acids, including leucine, which trigger the downstream mTOR (mammalian target of rapamycin) pathway. We examined the association between androgen receptor and LAT1, and the association between LAT1 expression and the acquisition of castration resistance. Western blot and real-time polymerase chain reaction were performed to study protein and mRNA expression. siRNA was used to knock down target genes. A total of 92 prostate biopsy specimens of patients who underwent androgen deprivation therapy were used for immunohistochemical analyses. Cox hazard proportional models and the Kaplan-Meier method were used for statistical analyses. LAT1 was highly expressed in hormone resistant prostate cancer cell lines. Knockdown of LAT1 in LNCaP and C4-2 cells significantly suppressed cell proliferation, migration and invasion. Androgen receptor siRNA or androgen receptor blocking through bicalutamide (10 μM) or MDV3100 (10 μM) significantly increased LAT1 expression (p <0.01). Treatment with dihydrotestosterone (0.1 to 10 nM) reduced LAT1 expression in a dose dependent manner (p<0.01). Bicalutamide/MDV3100 plus siLAT1 synergistically suppressed prostate cancer cell proliferation compared to single inhibition by androgen receptor or LAT1 (p<0.01). High LAT1 expression correlated with significantly shorter prostate specific antigen recurrence-free survival in patients receiving androgen deprivation therapy (p <0.0001). LAT1 expression was an independentpredictor of castration resistance on multivariate analysis (HR 3.56, p=0.0133). The current data may indicate a novel mechanism to acquire castration resistance through activation of the amino acid transporter LAT1.

False-positive diagnosis of disease progression by magnetic resonance imaging for response assessment in prostate cancer with bone metastases: A case report and review of the pitfalls of images in the literature

Bone metastases are common in prostate cancer. However, differentiating neoplastic from non-neoplastic alterations of bone on images is challenging. In the present report, a rare case of bone marrow reconversion on magnetic resonance imaging (MRI) assessment, which may lead to a false-positive diagnosis of disease progression of bone metastases in hormone-resistant prostate cancer, is presented. Furthermore, a review of the literature regarding the pitfalls of images for response assessment, including the 'flare' phenomenon on bone scintigraphy, computed tomography (CT), positron emission tomography/CT and marrow reconversion on MRI is also provided. These inaccuracies, which may lead to a premature termination of an efficacious treatment, should be carefully considered by the radiologists and oncologists involved in clinical trials. The case reported in the present study showed how to assess the early therapeutic response and select the appropriate treatment for the patient when these pitfalls are encountered on clinical images.

Abstract 1790: Caloric restriction can increase the efficacy of radiation in both hormone-sensitive and hormone-resistant prostate cancers by downregulating the IGF-1R pathway

Abstract Locally advanced prostate cancers (LAPC) are aggressive, have poor prognosis, and are associated with high recurrence rates and conversion to castrate resistance. The molecular underpinnings of LAPC are being investigated to identify novel therapeutics. Animal models have shown that caloric restriction (CR) can potentially prevent the initiation of prostate cancer. We propose that CR may be used as a novel therapeutic intervention to enhance outcomes of radiation treatment by altering the molecular profile of prostate tumors. To assess the effect of CR with radiation in vivo, eighty 6 week old male nude mice were injected with LNCaP (hormone sensitive) or PC3 (hormone refractory) tumor cells. Once tumors were palpable, mice were randomized to be treated with one of 4 conditions: ad libitum (AL) diet, 8Gy of radiation (RT), 30% reduction in caloric intake (CR), or CR+RT. CR was associated with significant reduction in tumors. After PC3 tumor injection, compared with AL, the mice had a 22% reduction in tumor size with radiation, 77% with CR (p&amp;lt;0.01 by Student's t-test) and an 80% reduction with CR+RT (p&amp;lt;0.01). After LNCaP tumor injection, compared with ad libitum, the mice had a 49% reduction in tumor size with CR and a 55% reduction with CR+RT (p&amp;lt;0.01). Tissue evaluation of mice treated with CR or CR+RT from both the LNCaP and PC3 models revealed decreased proliferation via Ki-67 and increased apoptosis with cleaved caspase-3 levels. In addition, significant downregulation of multiple members of the IGF-1R pathway was seen, including downregulation of IGF-1R, IRS-1, PI3K and pAKT. Serum evaluation revealed decreased IGF-1:IGF-BP3 in serum. For the first time, we have shown that the efficacy of radiation can be increased by decreasing calories by 30% in both hormone-sensitive and hormone-refractory prostate cancer models. Future clinical trials for both hormone-sensitive and hormone-resistant prostate cancers should consider the innovative use of CR to augment standard cancer therapy as it has the potential to change the biology of tumors and enhance the opportunity for clinical benefit. Citation Format: Sunny Y. Han, Tu D. Dan, Tiziana De Angelis, John Y. Han, Mak Sarich, Peter Carroll, Karen Knudsen, Adam Dicker, Nicole L. Simone. Caloric restriction can increase the efficacy of radiation in both hormone-sensitive and hormone-resistant prostate cancers by downregulating the IGF-1R pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1790. doi:10.1158/1538-7445.AM2015-1790

Abstract 4995: HO1 induction interrupts the glucocorticoid receptor signaling in prostate cancer cells

Abstract Although initially treatable, prostate cancer can recur in a hormone refractory form that is not responsive to current available therapies. The mortality rate associated with hormone refractory prostate cancer is high, and there is an urgent need for new therapeutic agents to treat prostate cancer. In order to overcome the toxicity of chemotherapy, glucocorticoids have long been used in the treatment of hormone-resistant prostate cancer. Nevertheless, many authors reported that the glucocorticoid receptor (GR) can substitute the androgen receptor and activate a similar but distinguishable set of genes. A common feature of prostate cancer is the dependence on activated signal transducer and activator of transcription 3 (STAT3), a transcription factor for survival and a coactivator of GR signaling. We have previously demonstrated that the induction of HO1, an antioxidant and anti-inflammatory protein, increases STAT3 cytoplasmic retention, interfering with its signaling and promotes HO1 nuclear localization. Our aim is to study the effect of HO1 induction on GR signaling in prostate cancer. PC3 cells were treated with Dexamethasone (Dex) at different concentrations (10−7, 10−8 and 10−9 M) during 24 h in 10% charcoaled-serum media and were exposed to the pharmacological inducer of HO1 (hemin, 80 uM, 24 h). Control cells were treated with vehicles. No significant differences in cell viability were detected by MTT assay. In order to investigate whether HO1 interrupts the GR transcriptional activity, PC3 cells were transfected with a luciferase reporter plamid containing three glucocorticoid response elements. Transfected cells were treated either with hemin (80 uM, 24 h), Dex (10−8 M, 6 h) or the combination of both drugs. The GR transcriptional activation was confirmed when cells were treated with the agonist Dex (p&amp;lt;0.01). HO1 induction significantly reduced either the GR basal transcriptional activity (p&amp;lt;0.01) as well as the Dex induced (p&amp;lt;0.01). The expression of Ikb, a GR regulated gene, was screened by RT-qPCR and was confirmed its inhibition in hemin exposed cells treated or not with dexamethasone. The repressive activity of HO1 was also demonstrated using an NFkB luciferase reporter assay. Using confocal fluorescence microscopy, GR nuclear translocation upon Dex treatment was confirmed, and a decrease of GR nuclear localization was demonstrated under hemin+Dex treatment (p&amp;lt;0.01). These results correlate with the diminished luciferase activity of the MMTV-luc plasmid in the presence of hemin+Dex vs Dex alone. Strikingly this is the first report showing the immunoprecipitation of GR and HO1, showing physical interaction between these proteins, both in the nucleus and in the cytoplasm. In conclusion, these results provide a novel function for HO1 downmodulating GR transcriptional activity, repressing the expression of its target genes and interfering with the receptor's nuclear localization in prostate cancer cells. Citation Format: Daiana B. Leonardi, Alejandra V. Paez, Federico Schuster, Nicolas Anselmino, Javier N. Brandani, Mercedes Abbate, Geraldine Gueron, Javier H. Cotignola, Elba S. Vazquez. HO1 induction interrupts the glucocorticoid receptor signaling in prostate cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4995. doi:10.1158/1538-7445.AM2015-4995

False-Positive Results of 68ga-Dotatate and 11c-Cholıne Pet/CT in Patients with Hormone-Resistant Prostate Cancer at Biochemical Recurrence are Related to Inflamed Lesions

s of 17th ISORBE Congress 4-8 March 2015, Izmir, Turkey Molecular Imaging and Radionuclide Therapy 2015;24(1): 37-46 37 Omar Alonso, Gerardo Dos Santos, Eduardo Savio, Henry Engler Uruguayan Centre of Molecular Imaging (CUDIM), Montevideo, Uruguay False-Positive Results of 68ga-Dotatate and 11c-Choline Pet/CT in Patients with Hormone-Resistant Prostate Cancer at Biochemical Recurrence are Related to Inflamed Lesions Abstract Madhukar Thakur DOI: 10.4274/mirt.24.01.01Madhukar Thakur DOI: 10.4274/mirt.24.01.01 Thomas Jefferson University Faculty of Medicine, Department of Radiology, Philadelphia, United States Stem Cells