Androgen-independent Progression Research Articles

Insulin-like growth factor family and prostate cancer: new insights and emerging opportunities.

Prostate cancer is the second most commonly diagnosed cancer in men. The mammalian insulin-like growth factor (IGF) family is made up of three ligands (IGF-I, IGF-II, and insulin), three receptors (IGF-I receptor (IGF-1R), insulin receptor (IR), and IGF-II receptor (IGF-2R)), and six IGF-binding proteins (IGFBPs). IGF-I and IGF-II were identified as potent mitogens and were previously associated with an increased risk of cancer development including prostate cancer. Several reports showed controversy about the expression of the IGF family and their connection to prostate cancer risk due to the high degree of heterogeneity among prostate tumors, sampling bias, and evaluation techniques. Despite that, it is clear that several IGF family members play a role in prostate cancer development, metastasis, and androgen-independent progression. In this review, we aim to expand our understanding of prostate tumorigenesis and regulation through the IGF system. Further understanding of the role of IGF signaling in PCa shows promise and needs to be considered in the context of a comprehensive treatment strategy.

Abstract 2294: NEK1 phosphorylation of YAP promotes its stabilization and transcriptional output

Abstract Background: Despite recent development in prostate cancer (PCa) therapeutics, castration-resistant prostate cancer still accounts for high morbidity and mortality in patients, partly because of incomplete knowledge of the major players that contribute to the androgen independent growth of prostate tumor. NIMA related kinase 1 (NEK1), a dual specificity kinase, mainly functions in maintaining genomic stability by regulating DNA damage response (DDR) and G2/M transition of the cells. We previously reported that tousled-like kinase 1 (TLK1) mediated phosphorylation of NEK1 on T141 can lead to rapid androgen independent progression of PCa cells upon anti-androgen treatment by activating DDR. However, activating DDR alone may not be sufficient to trigger androgen insensitive growth of PCa cells. We hypothesize that TLK1>NEK1 axis may also regulate hippo pathway oncoprotein YAP as a previous study reported that NEK1 can phosphorylate YAP homolog TAZ and upregulate YAP/TAZ transcriptional targets. Yes-associated protein (YAP) is a transcriptional co-activator and a major effector of hippo kinases that binds to transcription factor TEAD and promotes many oncogenic activities in the cells. Methods and Results: To determine if NEK1 can regulate Hippo pathway, our western blotting (WB) analysis revealed higher cleaved YAP (cl-YAP) and lower total YAP level in the NEK1-T141A hypoactive variant overexpressing LNCaP than wt-NEK1 overexpressing cells treated with bicalutamide (anti-androgen) and/or THD (a specific inhibitor of TLK1) which suggest that NEK1 may play a role in stabilizing YAP. TLK1 inhibition also resulted in the reduced expression of some YAP target genes such as CTGF, CDH2, Twist1, and P53AIP1. Co-IP assay revealed that NEK1 can interact with YAP regardless of its kinase activity. We generated a CRISPR-Cas9 mediated NEK1 knockout NT1 (a mouse PCa cell line) cells which showed reduced level of YAP in NEK1 KO clones as well as downregulation of YAP target genes such as CTGF, Zeb1, Twist1, and Cyr61. TLK1 knockdown and inhibition also resulted in reduced pNEK1 (T141) and total YAP level which suggested TLK1 mediated NEK1 activation is necessary for YAP stabilization. An IVK assay using [γ-32P] ATP demonstrated that catalytically active purified NEK1 can phosphorylate purified YAP1. MS analysis determined eight NEK1 mediated phospho-acceptor sites of YAP1: T83, T361, S366, S388, Y407, and T493. Y407 and T493 are the first ever reported phosphorylation sites on YAP1 especially by NEK1 which lies in the transactivation and PDZ binding domain. Our bioinformatics analysis revealed mRNA downregulation of YAP1, while upregulation of YAP protein level was observed in high-grade PCa, which is consistent with our model of post-transcriptional protein stabilization. Conclusion: Our data support that TLK1>NEK1 signaling promotes YAP stabilization and may contribute to castration resistant growth of PCa during AR blockade. Citation Format: Md Imtiaz Khalil, Ishita Ghosh, Vibha Singh, Jing Chen, Haining Zhu, Arrigo De Benedetti. NEK1 phosphorylation of YAP promotes its stabilization and transcriptional output [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2294.

Anaplastic features (AnaF) and DNA-damage repair pathway (DDR) mutations in metastatic castration-resistant prostate cancer (mCRPC).

92 Background: Anaplastic prostate cancer displays features of small-cell carcinoma, a type of neuroendocrine tumor. Treatments for anaplastic prostate cancer are based on small cell lung cancer regimens. Both AnaF and mutations in DDR pathways, including BRCA2 confer an aggressive phenotype. For patients (pts) with certain DDR mutations, olaparib (O) was recently FDA approved, and an ongoing study is evaluating whether the addition of durvalumab (D) confers additional benefit in mCRPC (NCT02484404). We evaluate a potential preliminary relationship between DDR mutations, treatment with D and O, and AnaF. Methods: This is a phase II study of O plus D in pts with mCRPC with disease that is amenable to biopsy. On-study core biopsies undergo mutational analysis. Prior treatment with enzalutamide (enza) and/or abiraterone (abi) is required. D is given at 1500 mg iv q28 days + O 300 mg tablets po q12 hours. The primary endpoint is PFS. Pts were categorized into those with and without AnaF as defined by Aparicio et al. (2013). AnaF include small-cell histology; exclusively visceral metastases; predominantly lytic bone metastases; bulky lymphadenopathy (≥5 cm) or high-grade (Gleason ≥8) mass in prostate/pelvis; low PSA (≤10 ng/mL) at initial presentation with high volume (≥20) bone metastases; neuroendocrine markers in histology or serum plus elevated LDH, malignant hypercalcemia, or elevated serum CEA; or short interval (≤6 months) to androgen-independent progression. Results: Of 55 pts accrued, 24 had prior abi and enza; 19 pts had prior taxane. Common adverse events include anemia, fatigue, and nausea. Also, 11 pts (20.0%) displayed clear AnaF (Table) and 43 pts lacked AnaF, including 8 (14.5%) with partial AnaF that did not meet the full criteria, 4 (7.3%) who likely did not have AnaF due to difficulty in quantifying disease burden, 29 (52.7%) who did not have AnaF, and 2 (3.6%) had unknown status. Four pts (36.4%) with clear AnaF had DDR aberrations, including 3 (27.3%) with BRCA2, 1 (9.1%) with both BRCA2 and CHEK2, and 1 (9.1%) with ATM. Conclusions: Pts with mCRPC with DDR mutations can also have AnaF. This preliminary data demonstrates that pts with anaplastic prostate cancer and pts with DDR mutations are two distinct populations with some degree of overlap. O+D is well-tolerated, and future studies should focus on finding optimal treatments for pts with AnaF without and without DDR mutations. Clinical trial information: NCT02484404. [Table: see text]

Crosstalk Between AR and Wnt Signaling Promotes Castration-Resistant Prostate Cancer Growth.

IntroductionProstate cancer (PCa) is the most commonly diagnosed cancer and the third leading cause of cancer-related death in males in the United States. Despite the initial efficacy of androgen deprivation therapy in prostate cancer (PCa) patients, most patients progress to castration-resistant prostate cancer. However, the mechanisms underlying the androgen-independent progression of PCa remain largely unknown.MethodsIn this study, we established a PCa cell line (LNCaP-AI) by maintaining LNCaP cells under androgen-depleted conditions. To explore the cellular and molecular mechanisms of androgen-independent growth of PCa, we analyzed the gene expression patterns in androgen-independent prostate cancer (AIPC) compared with that in androgen-dependent prostate cancer (ADPC). KEGG pathway analysis revealed that Wnt signaling pathways were activated after androgen deprivation therapy (ADT). In vitro experiments showed that the inhibition of Wnt pathway reduced AIPC cell growth by inhibiting cell cycle progression and promoting apoptosis. Furthermore, WNT5A, LEF1 were identified as direct targets of AR by chromatin immunoprecipitation (ChIP) assay and public ChIP-seq datasets analysis.ResultsIn the present study, we found a regulatory mechanism through which crosstalk between androgen receptor (AR) and Wnt signals promoted androgen-independent conversion of PCa. The Wnt pathway was inhibited by androgen in androgen-dependent prostate cancer cells, but this blocking effect was not elicited in androgen-independent prostate cancer (AIPC) cells. Moreover, Wnt pathway genes WNT5A and LEF1 were directly downregulated by AR. In vitro experiments showed that inhibition of the Wnt pathways repressed AIPC cell growth by inhibiting cell cycle progression and promoting apoptosis. We found that WNT5A and LEF1 were downregulated in low-grade PCa but upregulated in metastatic PCa.ConclusionIn summary, we revealed that crosstalk between AR and Wnt signaling pathways promotes androgen-independent growth of PCa, which may provide novel therapeutic opportunities for castration-resistant prostate cancer.

Can ultrasound irradiation be a therapeutic option for prostate cancer?

Focal therapies for prostate cancer (PC) can reduce adverse events and do not lead to androgen-independent progression. Ultrasound could be used for cancer treatments if the repetition frequency is fitted to the purpose. We investigated the possible therapeutic effect of ultrasound irradiation on PC cells. We irradiated two PC cell lines, androgen-dependent LNCaP and -independent PC-3 with ultrasound (3.0 W/cm2 , 3 MHz, irradiation time rate: 20%) for 2 minutes for 1 day or 3 consecutive days at a repetition frequency of 1, 10, or 100 Hz in vitro. Cell proliferation and apoptosis were determined after irradiation. Cell proliferation of PC-3 was significantly inhibited after 1 day (P < .0001) and 3 days (P < .0001) of 10 Hz ultrasound irradiation, and that of LNCaP after 1 day (P < .0001) and 3 days (P < .0001) of irradiation. LNCaP was more sensitive to ultrasound at both lower and higher cell density but PC-3 was only sensitive at a lower cell density (P < .01). Irradiation with 10 Hz ultrasound-induced significantly more PC-3 apoptotic cells than control (1 day, P = .0137; 3 days, P = .0386) rather than irradiation with 1 Hz. Apoptosis via caspase-3 was induced at 10 Hz in 1-day (P < .05) irradiation in both cell lines. Ultrasound irradiation with even 1 day of 10 Hz significantly inhibited cell proliferation in both LNCaP and PC-3, especially by the remarkable induction of apoptosis in vitro. Our study indicated that ultrasound irradiation can be a therapeutic option for PC and further studies in vivo will be undertaken.

Changes in ki-67 and cleaved caspase-3 (CC3) with short term androgen deprivation therapy (ADT) prior to prostatectomy as part of a trial in intermediate and high-risk prostate cancer (PC).

e17502 Background: Ki-67 and CC3 are markers of cellular proliferation and apoptosis and have been associated with prognosis in localized PC. Testosterone suppression promotes a time-dependent modulation of these indices. We explored changes in Ki-67 and CC3 at different timepoints in a pilot trial using short-term ADT prior to radical prostatectomy (RP). Methods: Pts with intermediate and high-risk localized PC were randomized to receive a single dose of neoadjuvant degarelix (240 mg SC) either 4 ± 1 days (Cohort A) or 7 ± 1 days (Cohort B) prior to RP. Anatomically matched tumor foci from the pre-treatment diagnostic biopsy and the prostatectomy specimens were assessed by immunohistochemistry (IHC) for Ki-67, CC3, and PTEN expression. Results: 32 pts were randomized: 15 to Cohort A and 17 to Cohort B. Ki-67 and CC3 expression in the pre- and post-treatment samples for both cohorts are summarized in the table. A significant reduction in Ki-67 and increase in CC3 expression occurred in both cohorts (all p-values &lt; 0.05). No difference was found when the absolute difference of Ki-67 expression was compared between Cohort A and Cohort B (p = 0.7). A significant reduction of Ki-67 and increase in CC3 expression occurred in pts independent of PTEN status. Conclusions: A reduction of Ki-67 and an increase in CC3 expression was achieved in both cohorts following a single dose of degarelix within 1 week of RP. Although loss of PTEN has been associated with androgen-independent progression, reduction of proliferation and increase in apoptosis levels were achieved independent of PTEN status in this small cohort. Further analyses are ongoing to correlate the pathologic findings with clinical outcomes. Clinical trial information: NCT01542021 . [Table: see text]

New developments in mechanisms of prostate cancer progression.

Prostate cancer is the most prevalent type of cancer in men. The etiology of prostate cancer development and the mechanisms underlying androgen-independent progression remains to be further investigated. There are many known targets for prostate cancer therapy including the androgen receptor (AR) axis, but resistance eventually develops in advanced disease suggesting the need to better understand mechanisms of resistance and consideration of multi-targeted therapy. Mechanisms contributing to resistance may include gene amplifications, gene mutations, AR splice variants, and changes in expression of androgen receptor co-regulatory proteins. Given the limitations of approved therapies, further study of additional potential targets is warranted. This review focuses on the roles of autophagy pathway, p62, Yes-associated protein (YAP), cancer stem cells, and epigenetics. Therapies targeting these potential mechanisms of resistance may interact with currently approved therapies either additively or synergistically. Thus, the study of combination therapy against multiple targets may be critically important to achieve more impact against lethal forms of prostate cancer resistant to all approved current therapies.

MP70-13 DEPLETION OF PMEPA1 GENE CONFERS INCREASED CELL PROLIFERATION IN MOUSE PROSTATE EPITHELIUM

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology III1 Apr 2018MP70-13 DEPLETION OF PMEPA1 GENE CONFERS INCREASED CELL PROLIFERATION IN MOUSE PROSTATE EPITHELIUM Hua Li, Shashwat Sharad, Talai Barbiev, Wei Huang, Yingjie Song, Denise Young, Issabell Sesterhenn, Inger Rosner, Albert Dobi, Shiv Srivastava, and Taduru Sreenath Hua LiHua Li More articles by this author , Shashwat SharadShashwat Sharad More articles by this author , Talai BarbievTalai Barbiev More articles by this author , Wei HuangWei Huang More articles by this author , Yingjie SongYingjie Song More articles by this author , Denise YoungDenise Young More articles by this author , Issabell SesterhennIssabell Sesterhenn More articles by this author , Inger RosnerInger Rosner More articles by this author , Albert DobiAlbert Dobi More articles by this author , Shiv SrivastavaShiv Srivastava More articles by this author , and Taduru SreenathTaduru Sreenath More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.2257AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Dysfunctions of androgen receptor (AR) and transforming growth factor-β (TGF-β) signaling play important roles in tumorigenesis of prostate cancer (CaP). PMEPA1 gene is androgen and TGF-β -responsive with abundance in human prostate gland. The PMEPA1 biological functions involve suppression of AR and TGF-β signaling through similar negatively regulated feedback loop. Loss of PMEPA1 gene expression was reported in primary tumors of over two thirds of CaP patients may facilitate the activation AR and TGF-β signaling and supporting androgen dependent and independent progression of CaP respectively. Here we describe the evaluation of Pmepa1 gene knock-out model with conditionally silencing in mouse prostate epithelium to further dissect its biological functions in prostate development and tumorigenesis in vivo. METHODS Pmepa1 gene was conditionally deleted in C57BL/6 mouse prostate epithelium by ARR2PB-Cre-Lox system. Male mice of genotypes of wild-type, Pmepa1 flox/wild-type-ARR2PB-Cre, Pmepa1 flox/flox-ARR2PB-Cre were analyzed at age of 3, 9 and 15 months. The prostate and control tissues were sectioned and stained with Hematoxylin & Eosin (H&E). The protein levels of Pmepa1, Ar, Nkx3.1, Pten, Cre, Akt and proliferating cell nuclear antigen (Pcna) were analyzed by immunohistochemistry (IHC). The transcript levels of Pmepa1 were evaluated by RNA in situ hybridization (RISH). RESULTS The data of IHC and RISH showed Pmepa1 gene was suppressed in Pmepa1 flox/flox and Pmepa1 flox/wild-type ARR2PB-Cre mice. Compared to wild-type mice, protein levels of Ar and AR responsive gene Nkx3.1 were enhanced in prostate epithelium in Pmepa1 heterozygous and homozygous knockout mice at the age of 3, 9 and 15 months. The protein level of Pten was not significantly different in Pmepa1 conditional knockout mouse. However, the protein levels of Akt were increased in prostate epithelium with Pmepa1 deletion at the age of 9 and 15 months. Importantly, stronger Pcna IHC staining was observed in knockout prostate epitheliums, highly suggesting Pmepa1 silencing leading to accelerated prostate epithelium proliferation via activated Ar and Akt signaling. CONCLUSIONS Conditional deletion of Pmepa1 gene in mouse prostate epithelium resulted in enhanced Ar protein, activated Ar/Akt signaling and accelerated cell growth. This new mouse model provides opportunities to assess Pmepa1 functions in prostate and other cancers where PMEPA1 is altered. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e939 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Hua Li More articles by this author Shashwat Sharad More articles by this author Talai Barbiev More articles by this author Wei Huang More articles by this author Yingjie Song More articles by this author Denise Young More articles by this author Issabell Sesterhenn More articles by this author Inger Rosner More articles by this author Albert Dobi More articles by this author Shiv Srivastava More articles by this author Taduru Sreenath More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Inhibition of LSD1 by Pargyline inhibited process of EMT and delayed progression of prostate cancer in vivo

Recently, lysine-specific demethylase 1 (LSD1) was identified as the first histone demethylase. LSD1 interacted with androgen receptor (AR) and promoted androgen-dependent transcription of target genes, such as PSA, by ligand-induced demethylation of mono- and dimethylated histone H3 at Lys 9 (H3K9). Meanwhile, the phenomenon of epithelial–mesenchymal transition (EMT) had received considerable attention in tumor recurrence and metastasis. This study examined the effect of Pargyline (an inhibitor of LSD1) on the process of EMT in vitro and in vivo. SCID mice were injected subcutaneously with LNCap cells. Pargyline was given intraperitoneally or not after castration (implemented with Bilateral orchidectomy), then PSA levels in serum and tumor were determined to assess time to androgen-independent progression. The results showed that LSD1 expression was up-regulated when PCa progressed to Castration Resistant Prostate Cancer (CRPC). Pargyline reduced LNCap cells migration and invasion ability, and inhibited the process of EMT by up-regulating expression of E-cadherin, and down-regulating expressions of N-cadherin and Vimentin in vitro and in vivo. Although, Pargyline did not change the level of AR, it reduced PSA expression both in vitro and in vivo. Furthermore, Pargyline delayed prostate cancer transition from androgen-dependent to androgen-independent state (CRPC). These findings indicated that inhibition of LSD1 might be a promise adjunctive therapy with androgen deprivation therapy (ADT) for locally advanced or metastatic prostate cancer.

PC-1/PrLZ confers resistance to rapamycin in prostate cancer cells through increased 4E-BP1 stability.

An important strategy for improving advanced PCa treatment is targeted therapies combined with chemotherapy. PC-1, a prostate Leucine Zipper gene (PrLZ), is specifically expressed in prostate tissue as an androgen-induced gene and is up-regulated in advanced PCa. Recent work confirmed that PC-1 expression promotes PCa growth and androgen-independent progression. However, how this occurs and whether this can be used as a biomarker is uncertain. Here, we report that PC-1 overexpression confers PCa cells resistance to rapamycin treatment by antagonizing rapamycin-induced cytostasis and autophagy (rapamycin-sensitivity was observed in PC-1-deficient (shPC-1) C4-2 cells). Analysis of the mTOR pathway in PCa cells with PC-1 overexpressed and depressed revealed that eukaryotic initiation factor 4E-binding protein 1(4E-BP1) was highly regulated by PC-1. Immunohistochemistry assays indicated that 4E-BP1 up-regulation correlates with increased PC-1 expression in human prostate tumors and in PCa cells. Furthermore, PC-1 interacts directly with 4E-BP1 and stabilizes 4E-BP1 protein via inhibition of its ubiquitination and proteasomal degradation. Thus, PC-1 is a novel regulator of 4E-BP1 and our work suggests a potential mechanism through which PC-1 enhances PCa cell survival and malignant progression and increases chemoresistance. Thus, the PC-1-4E-BP1 interaction may represent a therapeutic target for treating advanced PCa.

Nadir testosterone within first year of androgen-deprivation therapy (ADT) predicts for time to castration-resistant progression: a secondary analysis of the PR-7 trial of intermittent versus continuous ADT.

Three small retrospective studies have suggested that patients undergoing continuous androgen deprivation (CAD) have superior survival and time to progression if lower castrate levels of testosterone (< 0.7 nmol/L) are achieved. Evidence from prospective large studies has been lacking. The PR-7 study randomly assigned patients experiencing biochemical failure after radiation therapy or surgery plus radiation therapy to CAD or intermittent androgen deprivation. The relationship between testosterone levels in the first year and cause-specific survival (CSS) and time to androgen-independent progression in men in the CAD arm was evaluated using Cox regression. There was a significant difference in CSS (P = .015) and time to hormone resistance (P = .02) among those who had first-year minimum nadir testosterone ≤ 0.7, > 0.7 to ≤ 1.7, and ≥ 1.7 nmol/L. Patients with first-year nadir testosterone consistently > 0.7 nmol/L had significantly higher risks of dying as a result of disease (0.7 to 1.7 nmol/L: hazard ratio [HR], 2.08; 95% CI, 1.28 to 3.38; > 1.7 nmol/L: HR, 2.93; 95% CI, 0.70 to 12.30) and developing hormone resistance (0.7 to 1.7 nmol/L: HR, 1.62; 95% CI, 1.20 to 2.18; ≥ 1.7 nmol/L: HR, 1.90; 95% CI, 0.77 to 4.70). Maximum testosterone ≥ 1.7 nmol/L predicted for a higher risk of dying as a result of disease (P = .02). Low nadir serum testosterone (ie, < 0.7 mmol/L) within the first year of androgen-deprivation therapy correlates with improved CSS and duration of response to androgen deprivation in men being treated for biochemical failure undergoing CAD.

Abstract 4212: ADAM10/Kuzbanian is upregulated during neuroendocrine prostate carcinogenesis

Abstract Prostate cancer (CaP) is the second leading cause of cancer death in men. Advanced prostate tumors often contain neuroendocrine differentiation, which correlates with androgen-independent progression and poor prognosis. Currently, androgen deprivation is the first line of therapy for metastatic CaP. However, CaP often progresses to an androgen-independent bone-metastatic stage, at which point chemotherapy and radiotherapy become the primary therapeutic options. Despite recent advances in therapeutic strategies, many cancers still develop resistance to radiation and therapies, making the identification of new therapies essential to improve the lives and survival rates of patients. We have studied neuroendocrine cancer progression in the cryptdin-2 SV40-TAg (CR2-TAg) mouse model of CaP. Since these cancers do not express androgen receptor, they are refractory to androgen therapy. Therefore, we sought new potential targets. We previously found that matrix metalloproteinases (MMPs), which are capable of degrading many extracellular matrix proteins and cell surface receptors, are upregulated during CR2-Tag tumor progression. In the present study, we examined expression of a family of a disintegrin and metalloproteinases (ADAMs) that is actively involved in these signaling pathways due to their role in releasing the extracellular domain of transmembrane proteins. ADAMs contain features of both adhesive proteins and proteinases. ADAM10 activates the epidermal growth factor receptor (EGFR) and NOTCH signaling systems controlling cell growth, invasion, and metastasis. We found that ADAM10 expression increased during tumor progression and was highly penetrant. We are quantifying the expression levels and localization patterns of ADAM10 in these samples over time. Since MMPs, like ADAMs, are capable of degrading many extracellular matrix proteins and cell surface receptors, we determined if MMPs (MMP 2, 7, and 9) contribute to ADAM10 expression or localization in aggressive hormone refractory CaP. We have stained for ADAM10 in tissue sections from the CR2-TAg mice that are each missing expression of MMPs to determine if that particular MMP contributes to ADAM10 expression or localization. Our research using ADAM10 localization as a potential biomarker and therapeutic target has potential clinical value to identify aggressive CaP earlier in patients. Our study of MMPs and their role in ADAM10 expression will offer insight into the mechanisms of advanced prostate tumor progression. Note: This abstract was not presented at the meeting. Citation Format: Brian D. Shannon, Laurie E. Littlepage. ADAM10/Kuzbanian is upregulated during neuroendocrine prostate carcinogenesis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4212. doi:10.1158/1538-7445.AM2014-4212

Long-term efficacy and tolerability of abdominal once-yearly histrelin acetate subcutaneous implants in patients with advanced prostate cancer.

Objectives. Long-term assessment of the efficacy and tolerability of subcutaneous abdominal histrelin acetate implants that have been inserted for more than two years. Materials and Methods. Retrospective data collected over a six-year period at a single center from charts of 113 patients who received the subcutaneous abdominal histrelin acetate implant. Results. Following insertion of the first implant, 92.1% and 91.8% of patients had a serum testosterone level of ≤30 ng/dL at 24 and 48 weeks, respectively. Serum testosterone levels remained at <30 ng/dL for 96% of patients at two years and for 100% of patients at 3, 4, and 5 years. The testosterone levels remained significantly less than baseline (P < 0.05). Six patients (5.3%) had androgen-independent progression when followed up on the long term, increasing the mean serum PSA at 3, 4, and 5 years to 35.0 µg/L (n = 22), 30.7 µg/L (n = 13), and 132.9 µg/L (n = 8), respectively. The mean serum PSA was significantly greater than baseline during these years (P < 0.05). Eight patients (7.1%) experienced minor, but not serious, adverse events from the histrelin acetate. Conclusion. Subcutaneous abdominal histrelin acetate implants are an effective long-term and well-tolerated administration method for treating patients with advanced prostate cancer.

Abstract 2126: Inhibition of hedgehog and androgen receptor signaling pathways produced synergistic suppression of androgen independent prostate cancer progression.

Abstract Introduction: Prostate cancer (PCa) is the second most common cause of death from cancer and the leading cancer diagnosed in the US men. Approximately 1 in 6 American men will be diagnosed with prostate cancer during his lifetime. Estimated new cases and deaths from prostate cancer in the United States for 2012 include: 241,740 new cases and 28,710 deaths. Initial treatment for metastatic PCa involves androgen ablation therapy, which causes regression of androgen-dependent tumors. However they all eventually relapse resulting in recurrent androgen independent prostate cancer (AIPC). Methods: This study aims at assessing the role of Hedgehog (Hh) and Androgen receptor (AR) signaling in the development of AIPC. Quantitative RT-PCR analysis was performed for AIPC cells in vitro and for AIPC xenograft after castration, to assess the levels of Hh and AR signaling components. Hh inhibitors, LDE225 (Novartis) and Cyclopamine, and Androgen receptor inhibitor Pyrvinium pamoate were tested individually and in combination to assess the suppression of AIPC progression both in vitro and in vivo. AR-responsive and Gli-responsive promoter-luciferase assay and MTT assay were used for in vitro studies. Intraperitoneal administration of drugs and bioluminescence imaging for monitoring orthotopic tumors in mice were used to study the effect of drugs on the growth of AIPC in vivo. Results: We demonstrate that androgen deprivation leads to increase in Hedgehog (Hh) signaling components in the AIPC cells in vitro and in vivo. AIPC cells also show increased sensitivity to low concentrations of androgen, suggesting increased androgen receptor expression. Together, these results suggest that increased Hh signaling and androgen receptor expression in the absence of androgen agonist plays an important role in the development and progression of AIPC. Our results show that inhibiting either Hh or androgen receptor signaling pathway individually was not effective in preventing AIPC cell proliferation in vitro as well as in inhibiting xenograft tumor growth in mice. In contrast, combination of an Hh pathway inhibitor with an androgen receptor inhibitor synergistically suppressed the growth of AIPC cells in vitro as assessed by MTT assay and reduced tumor burden in a mouse xenograft model of AIPC as compared to individual treatments.Conclusion: Upregulated Hh signaling and AR expression mediates development and progression of AIPC. Combined inhibition of Hh and androgen receptor signaling pathways may be a novel effective therapeutic strategy for the treatment of androgen independent prostate cancer. Citation Format: pramod gowda, Jianhong Deng, Sweta Mishra, LuZhe Sun. Inhibition of hedgehog and androgen receptor signaling pathways produced synergistic suppression of androgen independent prostate cancer progression. [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 2126. doi:10.1158/1538-7445.AM2013-2126

Genomic Rearrangements of PTEN in Prostate Cancer

The phosphatase and tensin homolog gene (PTEN) on chromosome 10q23.3 is a negative regulator of the PIK3/Akt survival pathway and is the most frequently deleted tumor suppressor gene in prostate cancer. Monoallelic loss of PTEN is present in up to 60% of localized prostate cancers and complete loss of PTEN in prostate cancer is linked to metastasis and androgen-independent progression. Studies on the genomic status of PTEN in prostate cancer initially used a two-color fluorescence in situ hybridization (FISH) assay for PTEN copy number detection in formalin fixed paraffin embedded tissue preparations. More recently, a four-color FISH assay containing two additional control probes flanking the PTEN locus with a lower false-positive rate was reported. Combined with the detection of other critical genomic biomarkers for prostate cancer such as ERG, androgen receptor, and MYC, the evaluation of PTEN genomic status has proven to be invaluable for patient stratification and management. Although less frequent than allelic deletions, point mutations in the gene and epigenetic silencing are also known to contribute to loss of PTEN function, and ultimately to prostate cancer initiation. Overall, it is clear that PTEN is a powerful biomarker for prostate cancer. Used as a companion diagnostic for emerging therapeutic drugs, FISH analysis of PTEN is promisingly moving human prostate cancer closer to more effective cancer management and therapies.

Targeting TCTP as a New Therapeutic Strategy in Castration-resistant Prostate Cancer

Heat shock protein 27 (Hsp27) is highly overexpressed in castration-resistant prostate cancer (CRPC) and an antisense inhibitor (OGX-427) is currently in phase II clinical trials. In order to understand mechanisms of action of Hsp27 and find new therapeutic targets specific of CRPC, we screened for Hsp27 client proteins. Here, we report that translationally controlled tumor protein (TCTP) is a new Hsp27 client protein involved in Hsp27 cytoprotection. We found that TCTP expression is absent or weak in normal prostate cells, moderately expressed in 18.5% of treatment naive PC, and becomes uniformly and strongly expressed in 75% of CRPC. To define TCTP function, we developed and worldwide patented a TCTP antisense oligonucleotide (ASO). Interestingly, we found that CRPC progression correlates with TCTP overexpression and loss of P53. TCTP knockdown restored P53 expression and function, suggesting that castration-sensitivity is directly linked to P53 expression. Collectively, these findings provide a new Hsp27 cytoprotection mechanism in CRPC, and preclinical proof-of-concept that combining ASO-mediated TCTP knockdown with castration and/or docetaxel therapy could serve as a novel strategy to treat CRPC, with no or little toxicity for normal prostate cells.

Spontaneous Cancer-Stromal Cell Fusion as a Mechanism of Prostate Cancer Androgen-Independent Progression

We have previously shown that human prostate cancer cells are capable of acquiring malignant attributes through interaction with stromal cells in the tumor microenvironment, while the interacting stromal cells can also become affected with both phenotypic and genotypic alterations. This study used a co-culture model to investigate the mechanism underlying the co-evolution of cancer and stromal cells. Red fluorescent androgen-dependent LNCaP prostate cancer cells were cultured with a matched pair of normal and cancer-associated prostate myofibroblast cells to simulate cancer-stromal interaction, and cellular changes in the co-culture were documented by tracking the red fluorescence. We found frequent spontaneous fusions between cancer and stromal cells throughout the co-culture. In colony formation assays assessing the fate of the hybrid cells, most of the cancer-stromal fusion hybrids remained growth-arrested and eventually perished. However, some of the hybrids survived to form colonies from the co-culture with cancer-associated stromal cells. These derivative clones showed genomic alterations together with androgen-independent phenotype. The results from this study reveal that prostate cancer cells are fusogenic, and cancer-stromal interaction can lead to spontaneous fusion between the two cell types. While a cancer-stromal fusion strategy may allow the stromal compartment to annihilate invading cancer cells, certain cancer-stromal hybrids with increased survival capability may escape annihilation to form a derivative cancer cell population with an altered genotype and increased malignancy. Cancer-stromal fusion thus lays a foundation for an incessant co-evolution between cancer and the cancer-associated stromal cells in the tumor microenvironment.

Transcriptional Signatures of Ral GTPase Are Associated with Aggressive Clinicopathologic Characteristics in Human Cancer

RalA and RalB are small GTPases that support malignant development and progression in experimental models of bladder, prostate, and squamous cancer. However, demonstration of their clinical relevance in human tumors remains lacking. Here, we developed tools to evaluate Ral protein expression, activation, and transcriptional output and evaluated their association with clinicopathologic parameters in common human tumor types. To evaluate the relevance of Ral activation and transcriptional output, we correlated RalA and RalB activation with the mutational status of key human bladder cancer genes. We also identified and evaluated a transcriptional signature of genes that correlates with depletion of RalA and RalB in vivo. The Ral transcriptional signature score, but not protein expression as evaluated by immunohistochemistry, predicted disease stage, progression to muscle invasion, and survival in human bladder cancers and metastatic and stem cell phenotypes in bladder cancer models. In prostate cancer, the Ral transcriptional signature score was associated with seminal vesicle invasion, androgen-independent progression, and reduced survival. In squamous cell carcinoma, this score was decreased in cancer tissues compared with normal mucosa, validating the experimental findings that Ral acts as a tumor suppressor in this tumor type. Together, our findings show the clinical relevance of Ral in human cancer and provide a rationale for the development of Ral-directed therapies.

Testosterone recovery in the off-treatment time in prostate cancer patients undergoing intermittent androgen deprivation therapy

Intermittent androgen deprivation (IAD) for prostate cancer was studied with the objective of reducing the side effects of treatment and potentially delaying the development of hormone resistance. There also appears to be a quality of life benefit during off-treatment intervals owing to the recovery of serum testosterone levels. In this multicentre European prospective randomised phase III trial EC507, testosterone serum concentrations were analysed in prostate cancer patients with PSA progression after radical prostatectomy. Patients were randomised to a continuous androgen deprivation (CAD) and IAD therapy using a 3-month depot with 11.25 mg leuprorelin acetate as microcapsule formulation. A complete IAD cycle comprises both a 6-month androgen deprivation therapy plus the off-treatment time (OTT). Serum testosterone recovery was recorded in 109 patients during OTT in the IAD group. Testosterone recovery to baseline values was achieved in 79.3% during the first and in 64.9% during the second IAD cycle, respectively. Median time to testosterone normalisation was 100 days in the first and 115 days in the second cycle, respectively. No significant difference was observed up to 1000 days between IAD and CAD with regard to time to androgen-independent progression. This is the first prospective study of leuprorelin acetate 11.25mg demonstrating normalisation of testosterone levels in the off-treatment period in patients undergoing IAD. The prerequisite of an IAD treatment is the testosterone recovery during off-treatment periods. In this study, in patients with PSA relapse after radical prostatectomy, a real achievement of intermittent castration with normalisation of testosterone levels during off-treatment periods could be confirmed.

Abstract 3927: Loss of bHLH transcription factor Id4 modulates androgen receptor activity in prostate cancer progression

Abstract Inhibitor of differentiation 4 (Id4), a crucial developmental gene also expressed in the normal prostate, has been shown to act as a tumor suppressor in prostate cancer. Promoter hypermethylation of Id4 is observed in several advanced stage cancers including prostate cancer. The loss of Id4 expression correlates with androgen independent prostate cancer progression. Our studies suggest that Id4 plays a crucial role in mediating the transition from androgen dependent to androgen independent prostate cancer by mediating the AR axis potential and reprogramming several cellular mechanisms including migration, senescence and proliferation. Stable transfection of a full length Id4 plasmid into the androgen-independent prostate cancer cell line DU145 resulted in re-expression of AR and downstream AR response gene PSA. Id4 transfected cells also observed an androgen regulated rate of proliferation in responsive to treatment with AR antagonist, Casodex. AR antagonism also significantly reduced the rate of migration as observed by a scratch wound assay. Under closer observation, AR antagonist treatment with Casodex also inhibited translocation of AR to the nucleus of DU145 cells as observed by immunofluorescence. Previous studies in our laboratory have demonstrated that DU145+Id4 transfected cells undergo a significant level of senescence (∼ 32%) compared to normal DU145 cells (∼ 4%). Treatment of DU145+Id4 cells with the AR antagonist Casodex demonstrate that the rate of senescence in DU145+Id4 transfected cells is closely related to inhibition of AR activity. Our results suggest that Id4 may play a crucial role in the loss of AR activity in advanced stage prostate cancer progression. These results also suggest that the antagonism of AR nuclear translocation post Id4 induction closely regulates the rate of proliferation and the induction of a senescent phenotype. These results provide a significant correlation between Id4 expression and AR activity during prostate cancer progression. Loss of AR activity through Id4 promoter hypermethylation may play a crucial role in understanding castration resistant prostate cancer. Therefore, induction of Id4 may provide a novel therapeutic target for advanced stage prostate cancer treatment. 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 3927. doi:1538-7445.AM2012-3927