ROR-γ drives androgen receptor expression and represents a therapeutic target in castration-resistant prostate cancer

The androgen receptor (AR) is overexpressed and hyperactivated in human castration-resistant prostate cancer (CRPC). However, the determinants of AR overexpression in CRPC are poorly defined. Here we show that retinoic acid receptor-related orphan receptor γ (ROR-γ) is overexpressed and amplified in metastatic CRPC tumors, and that ROR-γ drives AR expression in the tumors. ROR-γ recruits nuclear receptor coactivator 1 and 3 (NCOA1 and NCOA3, also known as SRC-1 and SRC-3) to an AR-ROR response element (RORE) to stimulate AR gene transcription. ROR-γ antagonists suppress the expression of both AR and its variant AR-V7 in prostate cancer (PCa) cell lines and tumors. ROR-γ antagonists also markedly diminish genome-wide AR binding, H3K27ac abundance and expression of the AR target gene network. Finally, ROR-γ antagonists suppressed tumor growth in multiple AR-expressing, but not AR-negative, xenograft PCa models, and they effectively sensitized CRPC tumors to enzalutamide, without overt toxicity, in mice. Taken together, these results establish ROR-γ as a key player in CRPC by acting upstream of AR and as a potential therapeutic target for advanced PCa.

A phase 3b study of sofosbuvir plus ribavirin in treatment-naive and treatment-experienced Korean patients chronically infected with genotype 2 hepatitis C virus

In Korea, patients with chronic hepatitis C virus (HCV) infection are typically treated with pegylated interferon-alpha plus ribavirin, but interferons are contraindicated in many patients and are often poorly tolerated, particularly by the elderly and those with advanced liver disease. No interferon-free treatment regimens are approved in Korea. Sofosbuvir is an oral nucleotide analog inhibitor of the HCV nonstructural 5B RNA polymerase. It is approved in the USA, European Union and Japan for treating a number of HCV genotypes, including genotype 2. Genotype 2 has a seroprevalence of 38-46% in Korea. This single-arm, phase 3b study (NCT02021643) examined the efficacy and safety of sofosbuvir plus ribavirin (12-week duration) in chronic genotype 2 HCV-infected treatment-naive and treatment-experienced Korean patients with and without cirrhosis. The proportion of patients with sustained virologic response 12 weeks after treatment discontinuation (SVR12) was 97% (125/129), with 96% (101/105) of treatment-naive and 100% (24/24) of treatment-experienced patients achieving SVR12. Two patients experienced virologic failure (n = 1, on-treatment failure; n = 1, relapse). No patient discontinued study treatment due to an adverse event (AE). The most common treatment-emergent AEs were headache (18%, 23/129) and pruritus (15%, 19/129). Few patients had grade 3 AEs (5%, 6/129) or grade 3 laboratory abnormalities (12%, 15/129). No grade 4 AE was reported. These data suggest that 12 weeks of treatment with the all-oral, interferon-free regimen of sofosbuvir plus ribavirin is effective and well tolerated in Korean patients with chronic genotype 2 HCV infection.

Mechanisms of resistance in castration-resistant prostate cancer (CRPC)

Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies.

Sofosbuvir plus ribavirin for the treatment of patients with chronic genotype 1 or 6 hepatitis C virus infection in Hong Kong

BACKGROUND

In Hong Kong, most patients with hepatitis C virus (HCV) have either genotype 6a or 1b infection.

AIM

To evaluate the efficacy and safety of sofosbuvir with ribavirin in treatment-naïve patients in Hong Kong with HCV genotype 1 or 6.

METHODS

In an open-label study, patients were randomised to sofosbuvir 400 mg once daily plus ribavirin 1000-1200 divided twice daily for 12 (n = 10), 16 (n = 11) or 24 (n = 10) weeks. The primary endpoint was the percentage of patients with HCV RNA < LLOQ (lower limit of quantification, 25 IU/mL) 12 weeks after cessation of therapy (SVR12).

RESULTS

All 31 patients (20 HCV genotype 1 and 11 genotype 6) had HCV RNA < LLOQ by Week 4 of treatment and at their last on-treatment visit. SVR12 rates were high in all treatment groups: 100% (10/10) for 12 weeks, 100% (11/11) for 16 weeks and 90% (9/10) for 24 weeks of therapy. The only patient who did not reach SVR12 had genotype 1 HCV and relapsed at post-treatment Week 4. Sofosbuvir with ribavirin was generally well tolerated. The most common adverse events were malaise (13%) and upper respiratory tract infection (13%), followed by anaemia (10%). No patients experienced serious adverse events. One patient discontinued treatment at Week 16 because of an adverse event. The event, upper respiratory tract infection, was not considered treatment related by the investigator. This subject achieved SVR12.

CONCLUSIONS

The all-oral regimen sofosbuvir plus ribavirin is effective in treatment-naïve patients in Hong Kong with genotype 1 or 6 HCV.

TRIAL REGISTRATION NUMBER

NCT02021643.

miR-124 and Androgen Receptor Signaling Inhibitors Repress Prostate Cancer Growth by Downregulating Androgen Receptor Splice Variants, EZH2, and Src

miR-124 targets the androgen receptor (AR) transcript, acting as a tumor suppressor to broadly limit the growth of prostate cancer. In this study, we unraveled the mechanisms through which miR-124 acts in this setting. miR-124 inhibited proliferation of prostate cancer cells in vitro and sensitized them to inhibitors of androgen receptor signaling. Notably, miR-124 could restore the apoptotic response of cells resistant to enzalutamide, a drug approved for the treatment of castration-resistant prostate cancer. We used xenograft models to examine the effects of miR-124 in vivo when complexed with polyethylenimine-derived nanoparticles. Intravenous delivery of miR-124 was sufficient to inhibit tumor growth and to increase tumor cell apoptosis in combination with enzalutamide. Mechanistic investigations revealed that miR-124 directly downregulated AR splice variants AR-V4 and V7 along with EZH2 and Src, oncogenic targets that have been reported to contribute to prostate cancer progression and treatment resistance. Taken together, our results offer a preclinical rationale to evaluate miR-124 for cancer treatment.

Evaluation of the predictors of postoperative aggravation of shoulder imbalance in severe and rigid thoracic or thoracolumbar scoliosis

OBJECTIVE

To study the predictors of postoperative aggravation of shoulder imbalance in severe and rigid thoracic or thoracolumbar scoliosis.

METHODS

In this study, 49 patients with severe and rigid thoracic or thoracolumbar scoliosis were analyzed retrospectively. The patients underwent whole-spine anteroposterior and lateral radiography preoperatively and postoperatively. On the radiographs, we measured parameters, including T1 tilt, radiographic shoulder height (RSH), proximal curve, middle curve, distal curve, apical vertebral translation (AVT) of the middle curve, thoracic trunk shift (TTS), coronal balance, and sagittal balance. We regarded RSH and T1 tilt as postoperative shoulder balance parameters and divided the patients into improved and aggravated groups of shoulder imbalance. Univariate analysis, receiver operating characteristic (ROC) curve, and multivariate logistic regression analyses were used in the statistical analyses.

RESULTS

The RSH was -17.01 ± 21.85 mm before surgery and 4.76 ± 18.11 mm at follow-up. The T1 tilt angle was -10.20° ± 19.53° before surgery and -2.72° ± 13.48° at follow-up. The results of the univariate analysis suggest that preoperative RSH and proximal to middle curve change ratio were significantly higher in the patients in the improved RSH group (p < 0.01). In addition, preoperative RSH, preoperative T1 tilt, and apical vertebral translation of the middle curve were significantly higher, and preoperative proximal curve, postoperative proximal curve, and preoperative distal curve were significantly lower in the patients with improved T1 tilt group (p < 0.01). In a binary logistic regression analysis, preoperative RSH [B = -0.120, odds ratio (OR) = 0.887, p = 0.006] was found to be an independent predictor of postoperative aggravation of RSH. Similarly, preoperative T1 tilt (B = -0.488, OR = 0.614, p = 0.001) was found to be an independent predictor of postoperative aggravation of T1 tilt. Moreover, the relationship between changes in RSH and T1 tilt was either concordant or discordant.

CONCLUSION

Several radiographic parameters were found to affect postoperative aggravation of RSH and T1 tilt. In particular, preoperative RSH and T1 tilt were found to be independent predictive factors of postoperative aggravation of RSH and T1 tilt, respectively.

Targeting molecular resistance in castration-resistant prostate cancer

Multiple mechanisms of resistance contribute to the inevitable progression of hormone-sensitive prostate cancer to castration-resistant prostate cancer (CRPC). Currently approved therapies for CRPC include systemic chemotherapy (docetaxel and cabazitaxel) and agents targeting the resistance pathways leading to CRPC, including enzalutamide and abiraterone. While there is significant survival benefit, primary and secondary resistance to these therapies develops rapidly. Up to one-third of patients have primary resistance to enzalutamide and abiraterone; the remaining patients eventually progress on treatment. Understanding the mechanisms of resistance resulting in progression as well as identifying new targetable pathways remains the focus of current prostate cancer research. We review current knowledge of mechanisms of resistance to the currently approved treatments, development of adjunctive therapies, and identification of new pathways being targeted for therapeutic purposes.

Abstract 4969: Metformin causes AR degradation via Skp2-mediated ubiquitination

One of the mechanisms for prostate cancer cells to escape the new androgen receptor (AR) signaling inhibitor Enzalutamide (Enza) is through autophagy. Combination of anti-diabetic drug metformin with Enza demonstrated improved tumor suppression in the LNCaP C4-2B orthotopic model. Through delineating the mechanism in the metformin benefit, we discovered degradation of AR in cells treated with metformin alone and more in the combination with Enza and Abiraterone (Abi). The mRNA for AR in metformin-treated cells did not change significantly by qPCR assays. This degradation was inhibited when proteasome inhibitor MG132 was added prior to the treatments. Use of the FDA approved proteasome inhibitor Bortezomib also protected AR from degradation in the presence of metformin. Immunoprecipitation of AR with its antibodies showed ubiquitination; the reverse immunoprecipitation with anti-ubiquitin followed by anti-AR probing also showed similar results; suggesting ubiqutination responsible for AR degradation. With a paper by Li et al. proposing Skp2 being a novel E3 ubiquitin ligase targeting AR for ubiquitination, we attempted to knock-down Skp2 with transient siRNA transfection. Degradation of AR was lessened with Skp2 knockdown. This study supports that use of metformin in combination with Enza or other ARSI drugs may not only block autophagy survival but also cause AR degradation that leads to PC cell death.

Citation Format: Joy C. Yang, Allen C. Gao, Christopher P. Evans. Metformin causes AR degradation via Skp2-mediated ubiquitination. [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 4969. doi:10.1158/1538-7445.AM2015-4969

Using the modified Delphi method to establish a new Chinese clinical consensus of the treatments for cervical radiculopathy

PURPOSE

Although cervical radiculopathy is very common, there is no standard treatment for this condition, with little high-level evidence available to guide the treatment choice. Thus, this study aimed to review the current data on the management of cervical radiculopathy; and, further, to establish a new Chinese clinical consensus of the treatments for cervical radiculopathy using the Delphi method.

METHODS

First, a systematic review of the previously established treatment guidelines and of articles related to cervical radiculopathy was conducted to establish a protocol for the clinical consensus of the treatment for cervical radiculopathy. Second, from February 2012 to June 2014, we performed a modified Delphi survey in which the current professional opinions from 30 experienced experts, representing almost all of the Chinese provinces, were gathered. Three rounds were performed, and consensus was defined as ≥70% agreement.

RESULTS

Consensus of the treatments for cervical radiculopathy was reached on seven aspects, including the proportion of patients requiring only non-surgical therapies; the effectiveness of neck immobilization, physiotherapy, pharmacologic treatment; surgical indications; contraindications; surgery.

CONCLUSIONS

The modified Delphi study conducted herein reached a consensus concerning several treatment issues for cervical radiculopathy. In the absence of high-level evidence, at present, these expert opinion findings will help guide health care providers to define the appropriate treatment in their regions. Items with no consensus provide excellent areas for future research.

Identification of the man-made barium copper silicate pigments among some ancient Chinese artifacts through spectroscopic analysis

This article describes the complementary application of non-invasive micro-Raman spectroscopy and energy dispersive X-ray fluorescence spectrometry to the characterization of some ancient Chinese silicate artifacts. A total of 28 samples dated from fourth century BC to third century AD were analyzed. The results of chemical analysis showed that the vitreous PbO-BaO-SiO2 material was used to sinter these silicate artifacts. The barium copper silicate pigments including BaCuSi4O10, BaCuSi2O6 and BaCu2Si2O7 were widely identified from colorful areas of the samples by Raman spectroscopy. In addition, other crystalline phases such as Fe2O3, BaSi2O5, BaSO4, PbCO3 and quartz were also identified. The present study provides very valuable information to trace the technical evolution of man-made barium copper silicate pigments and their close relationship with the making of ancient PbO-BaO-SiO2 glaze and glass.

Abstract 327: Targeting autophagy overcomes enzalutamide resistance in castrate-resistant prostate cancer cells and improves therapeutic response in a xenograft model

Androgen deprivation or treatment with the androgen receptor signaling inhibitor (ARSI), Enzalutamide (MDV-3100, ENZA) or biclutamide induces autophagy in androgen-dependent and castration resistant CaP (CRPC) cell lines. This autophagic process is mediated by AMPK activation and the suppression of mTOR through Raptor phosphorylation (Serine 792). Using autophagy modulators such as clomipramine (CMI) or metformin in combination with ENZA drastically reduces the cell survival in the colony formation assay. Metformin in combination with ENZA causes AR degradation, which is inhibited by proteasome inhibitor MG132. Transcriptome deep sequencing of parental and ENZA resistant C4-2B cells was carried out to examine differential gene expression pattern that may be related to their ability to survive under constant high exposure to ARSI. In-vivo studies with mice orthotopically implanted with ENZA resistant cells demonstrates that the combination of ENZA and autophagy modulators, CMI or metformin significantly reduces tumor growth when compared to control groups (p&lt;0.005). Blocking autophagy pharmacologically or genetically significantly impairs prostate cancer cell survival in- vitro and in-vivo, implying the therapeutics potential of autophagy inhibitors in the antiandrogen resistance setting.This work is supported in part by Stand Up To Cancer - Prostate Cancer Foundation–Prostate Dream Team Translational Cancer Research Grant. This research grant is made possible by the generous support of the Movember Foundation. Stand Up To Cancer is a program of the Entertainment Industry Foundation administered by the American Association for Cancer Research.

Citation Format: Joy C. Yang, Hao G. Nguyen, Hsing-Jien Kung, Xu-Bao Shi, Derya Tilki, Ralph W. deVere White, Allen C. Gao, Christopher P. Evans. Targeting autophagy overcomes enzalutamide resistance in castrate-resistant prostate cancer cells and improves therapeutic response in a xenograft model. [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 327. doi:10.1158/1538-7445.AM2014-327

Conduction control at ferroic domain walls via external stimuli

Intriguing functionalities at nano-sized domain walls have recently spawned a new paradigm for developing novel nanoelectronics due to versatile characteristics. In this study, we explore a new scenario to modulate the local conduction of ferroic domain walls. Three controlling parameters, i.e., external electrical field, magnetic field and light, are introduced to the 90° domain walls (90° DWs) of BiFeO₃. Electrical modulation is realized by electrical transport, where the mobility of 90° DWs can be altered by gating voltage. We further use the ferromagnetic/antiferromagnetic coupling to reveal the inherent magnetism at the DWs. With an established magnetic nature, magnetotransport has been conducted to introduce magnetic controlling parameter, where a giant positive magnetoresistance change can be observed up to 200%. In addition, light modulated conduction, a core factor for multifunctional applications, is successfully demonstrated (current enhancement by a factor of 2 with 11 W white lamp). These results offer new insights to discover the tunability of domain wall nanoelectronics.

Targeting autophagy overcomes Enzalutamide resistance in castration-resistant prostate cancer cells and improves therapeutic response in a xenograft model

Macro-autophagy is associated with drug resistance in various cancers and can function as an adaptive response to maintain cell survival under metabolic stresses, including androgen deprivation. Androgen deprivation or treatment with androgen receptor (AR) signaling inhibitor (ARSI), Enzalutamide (MDV-3100, ENZA) or bicalutamide induced autophagy in androgen-dependent and in castration-resistant CaP (castration-resistant prostate cancer (CRPC)) cell lines. The autophagic cascade triggered by AR blockage, correlated with the increased light chain 3-II/I ratio and ATG-5 expression. Autophagy was observed in a subpopulation of C4-2B cells that developed insensitivity to ENZA after sustained exposure in culture. Using flow cytometry and clonogenic assays, we showed that inhibiting autophagy with clomipramine (CMI), chloroquine or metformin increased apoptosis and significantly impaired cell viability. This autophagic process was mediated by AMP-dependent protein kinase (AMPK) activation and the suppression of mammalian target of rapamycin (mTOR) through Raptor phosphorylation (Serine 792). Furthermore, small interfering RNA targeting AMPK significantly inhibited autophagy and promoted cell death in CaP cells acutely or chronically exposed to ENZA or androgen deprivation, suggesting that autophagy is an important survival mechanism in CRPC. Lastly, in vivo studies with mice orthotopically implanted with ENZA-resistant cells demonstrated that the combination of ENZA and autophagy modulators, CMI or metformin significantly reduced tumor growth when compared with control groups (P<0.005). In conclusion, autophagy is as an important mechanism of resistance to ARSI in CRPC. Antiandrogen-induced autophagy is mediated through the activation of AMPK pathway and the suppression of mTOR pathway. Blocking autophagy pharmacologically or genetically significantly impairs prostate cancer cell survival in vitro and in vivo, implying the therapeutics potential of autophagy inhibitors in the antiandrogen-resistance setting.

CTA095, a novel Etk and Src dual inhibitor, induces apoptosis in prostate cancer cells and overcomes resistance to Src inhibitors

Etk is a non-receptor tyrosine kinase, which provides a strong survival signal in human prostate cancer cells. Src, another tyrosine kinase that cross-activates with Etk, has been shown to play an important role in prostate cancer metastasis. Herein, we discovered a new class of Etk inhibitors. Within those inhibitors, CTA095 was identified as a potent Etk and Src dual inhibitor. CTA095 was found to induce autophagy as well as apoptosis in human prostate cancer cells. In addition, CTA095 inhibited HUVEC cell tube formation and “wound healing” of human prostate cancer cells, implying its role in inhibition of angiogenesis and metastasis of human prostate cancer. More interestingly, CTA095 could overcome Src inhibitor resistance in prostate cancer cells. It induces apoptosis in Src inhibitor resistant prostate cancer cells, likely through a mechanism of down regulation of Myc and BCL2. This finding indicates that simultaneously targeting Etk and Src could be a promising approach to overcome drug resistance in prostate cancer.

lncRNA-dependent mechanisms of androgen-receptor-regulated gene activation programs

While recent studies indicated roles of long non-coding RNAs (lncRNAs) in physiologic aspects of cell-type determination and tissue homeostasis¹ yet their potential involvement in regulated gene transcription programs remain rather poorly understood. Androgen receptor (AR) regulates a large repertoire of genes central to the identity and behavior of prostate cancer cells², and functions in a ligand-independent fashion in many prostate cancers when they become hormone refractory after initial androgen deprivation therapy³. Here, we report that two lncRNAs highly overexpressed in aggressive prostate cancer, PRNCR1 and PCGEM1, bind successively to the AR and strongly enhance both ligand-dependent and ligand-independent AR-mediated gene activation programs and proliferation in prostate cancer cells. Binding of PRNCR1 to the C-terminally acetylated AR on enhancers and its association with DOT1L appear to be required for recruitment of the second lncRNA, PCGEM1, to the DOT1L-mediated methylated AR N-terminus. Unexpectedly, recognition of specific protein marks by PCGEM1-recruited Pygopus2 PHD domain proves to enhance selective looping of AR-bound enhancers to target gene promoters in these cells. In “resistant” prostate cancer cells, these overexpressed lncRNAs can interact with, and are required for, the robust activation of both truncated and full length AR, causing ligand-independent activation of the AR transcriptional program and cell proliferation. Conditionally-expressed short hairpin RNA (shRNA) targeting of these lncRNAs in castration-resistant prostate cancer (CRPC) cell lines strongly suppressed tumor xenograft growth in vivo. Together, these results suggest that these overexpressed lncRNAs can potentially serve as a required component of castration-resistance in prostatic tumors.

Abstract 3279: Enhanced in vivo inhibition of neuropeptide-mediated castration resistant prostate cancer progression by combination therapy with enzalutamide and saracatinib

Introduction: It has been shown that overexpression of the neuropeptides gastrin-releasing peptide (GRP) in LNCaP cells renders the cells castration-resistant through both androgen receptor (AR) activation and intracrine androgen biosynthesis. Aberrant activation of AR by GRP is mediated through Src kinase activation, which may be inhibited by the specific SFK inhibitor saracatinib. Inhibition of cognate AR activation requires anti-androgen. We hypothesize that treatment of this kind of CRPC demands the combination of saracatinib and new generation anti-androgen enzalutamide (MDV-3100).

Materials and methods: LNCaP GRP-Pro cells grown in CS medium were treated with control, saracatinib (2 μM), enzalutamide (10 μM) or the combination. Cell proliferation over 7 days was monitored by MTT assays. Cell cycle distributions over 72 hours of treatment were analyzed by flow cytometry. Cells were collected to prepare nuclear and cytosolic lysates respectively and examined by Western Blotting analysis for AR, pSrc, pAkt, LC-3 and β-actin. Expression of full-length AR and variants were compared by RT-qPCR. Orthotopic injection of GRP-Pro cells into castrated SCID male mice was used as the animal model for drug treatment studies.

Results: Enzalutamide or saracatinib alone only slightly inhibited CR cell growth but the combination brought it down to 27% of the control. Apoptosis was also enhanced with the combination. Enzalutamide only inhibited AR nuclear translocation in regular serum-kept GRP-Pro cells, while saracatinib inhibited the translocation in CS conditions. In the orthotopic model, neither treatments with saracatinib (25 mg/kg/daily) or enzalutamide (10 mg/kg/daily) alone showed any effect on tumor take, tumor weight or serum PSA levels. However, the combination treatment drastically reduced the tumor weights (0.66±0.13 g for controls vs. 0.24±0.07 g for the combo) and serum PSA levels (120.79±27.87 ng/ml vs. 19.19±7.45 ng/ml).

Conclusions: For GRP mediated CRPC growth, neither saracatinib or enzalutamide alone is sufficient to inhibit AR translocation and tumor progression. Combination of the two significantly improved the treatment for the CRPC orthotopic tumor model.

Citation Format: Joy C. Yang, Hao G. Ngyuen, Allen C. Gao, Christopher P. Evans. Enhanced in vivo inhibition of neuropeptide-mediated castration resistant prostate cancer progression by combination therapy with enzalutamide and saracatinib. [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 3279. doi:10.1158/1538-7445.AM2013-3279

Abstract 1665: Autophagy is a survival mechanism in mediating resistance to androgen receptor signaling inhibitors in castrate resistant prostate cancer cells

Introduction and Objective: Macro-autophagy is associated with drug resistance in various cancers and can function as an adaptive response to maintain cell survival under metabolic stresses, including androgen deprivation. Our hypothesis was: 1) autophagy is a cellular mechanism that confers resistance to the androgen receptor signaling inhibitor (ARSI), enzalutamide (MDV-3100) therapy and 2) blocking autophagy circumvents this survival mechanism to improve therapeutic response.

Materials and methods: To determine if autophagy was activated, we examined expression levels of LC3-I/II using Western Blotting in prostate cancer (CaP) cell lines, LNCaP, C4-2B, and CWR22 stably over-expressing LC3-GFP. Flow cytometry and fluorescence microscopy were used to quantify and visualize autophagy and to analyze cell cycle progression and apoptosis. Clonogenic assays were employed to evaluate cell survival. Enzalutamide (ENZA) and biclutamide were used as androgen receptor inhibitors. SiRNA to AMPK was transfected with Lipofectamine 2000.

Results: Androgen deprivation or treatment with androgen receptor signaling inhibitors, ENZA or biclutamide induced autophagy in androgen-dependent and in castration resistant CaP (CRPC) cell lines. The autophagic cascade triggered by AR blockage, correlated with the increased LC3-II/I ratio and ATG-5 expression. Autophagy was observed in a subpopulation of C4-2B cells that developed insensitivity to ENZA after sustained exposure in culture. Using flow cytometry and clonogenic assays we showed that inhibiting autophagy with clomipramine or hydroxychloroquine increased apoptosis and significantly impaired cell viability. This autophagic process was mediated by AMPK activation and the suppression of mTOR through Raptor phosphorylation (Serine 792). Finally, si-RNA targeting AMPK significantly inhibited autophagy and promoted cell-death in CaP cells acutely or chronically exposed to ENZA or androgen deprived culturing condition, suggesting that autophagy is an important survival mechanism in CRPC cells.

Conclusion: These novel data support autophagy as an important mechanism of resistance to the androgen receptor signaling inhibitor in CRPC. Antiandrogen mediated autophagy is dependent on the activation of AMPK pathway and the suppression of mTOR pathway. Blocking autophagy pharmacologically or genetically significantly impairs prostate cancer cell survival, implying the therapeutics potential of autophagy inhibitors in the antiandrogen resistance setting.

Citation Format: Hao G. Nguyen, Joy C. Yang, Hsing-Jien Kung, Allen C. Gao, Christopher P. Evans. Autophagy is a survival mechanism in mediating resistance to androgen receptor signaling inhibitors in castrate resistant prostate cancer cells. [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 1665. doi:10.1158/1538-7445.AM2013-1665

Abstract 100: NF-κB2/p52 induces resistance to enzalutamide possibly by upregulation of AR-V7

Introduction and Objective: Despite initial response of prostate cancer (CaP) to androgen deprivation, clinical observations suggest that castration-resistant prostate cancer (CRPC) develops resistance to the recently approved anti-androgen, enzalutamide. There is an urgent need to identify pathways that perpetuate disease progression during AR blockade. Identification of these resistance pathways will help design co-targeting strategies to improve the magnitude and duration of benefit of enzalutamide in CRPC. Our previous studies have demonstrated that NF-κB2/p52 plays an important role in the aberrant activation of AR in CaP. In this study we tested whether NF-κB2/p52 mediates resistance to enzalutamide in CaP cells.

Methods: Cell growth was analyzed in LNCaP cells stably expressing p52 (LN-p52) and control cells (LN-neo) treated with enzalutamide. C4-2B cells were transfected with shRNA against p52 and cell growth was monitored. Expression levels of p52 in CaP cells grown chronically in enzalutamide were analyzed by Western blotting. Expression of AR variant AR-V7 was examined in LN-p52 and LN-neo cells by qRT-PCR and Western blotting. Expression of p52 was downregulated in VCaP and 22Rv1 cells by shRNA followed by treatment with enzalutamide and cell growth was monitored. Expression of AR-V7 was examined by qRT-PCR and Western blotting in VCaP and 22Rv1 cells transfected with shRNA against p52.

Results: LN-p52 cells exhibited significantly better growth rates compared to LN-neo cells in the presence of enzalutamide, indicating that NF-κB2/p52 may enhance the survival of CaP cells treated with enzalutamide. Downregulation of p52 in castration resistant C4-2B cells reduced cell survival when treated with enzalutamide, suggesting that p52 may mediate resistance to enzalutamide. Expression levels of p52 were enhanced in enzalutamide resistant C4-2B cells generated by chronic treatment with enzalutamide, indicating that increased expression of p52 may facilitate the development of resistance to enzalutamide. We also found that LN-p52 cells exhibited higher levels of AR-V7 compared to LN-neo cells. Downregulation of p52 in VCaP and 22Rv1 cells (expressing endogenous levels of AR variants such as AR-V7) decreased the expression of AR-V7, demonstrating that p52 may regulate alternative splicing of AR mRNA.

Conclusions: Our findings demonstrate an important role for NF-κB2/p52 in inducing resistance to enzalutamide in CaP cells. Our results also suggest that NF-κB2/p52 may regulate resistance to enzalutamide via upregulation of AR-V7.

Citation Format: Nagalakshmi Nadiminty, Ramakumar Tummala, Wei Lou, Joy C. Yang, Christopher P. Evans, Allen C. Gao. NF-κB2/p52 induces resistance to enzalutamide possibly by upregulation of AR-V7. [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 100. doi:10.1158/1538-7445.AM2013-100

Orthorhombic BiFeO3

A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO(3)(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane {110}(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism.

Inorganic phosphorus fractionation and its translocation dynamics in a low-P soil

The translocation of different inorganic phosphorus (Pi) forms in a low-P soil (Langfang experimental station, Hebei province, China) over time was investigated using P fractionation extraction and a (32)P tracer technique. The L-value and P availability of the soil was assessed using 5 different maize genotype (Zea mays L.) cultivars. The results showed that the different Pi fractions in the soil increased in the order of H(2)SO(4)-extractable P (Ca(10)-P) > Na(3)C(6)H(5)O(7)-Na(2)S(2)O(4)-extractable P (O-P) > NH(4)Ac-extractable P (Ca(8)-P) > NaHCO(3)-extractable P (Ca(2)-P), NH(4)F-extractable P (Al-P), NaOH-Na(2)CO(3)-extractable P (Fe-P), and the content of plant-unavailable P (Ca(10)-P + O-P) was high, up to 79.1%, which might be an important reason for P deficiency in this low-P soil. The (32)P tracer results showed that after the addition of (32)P-Pi to the soil with no P fertilizer applied for 25 d, 29.0% of (32)P was quickly transformed into Ca(2)-P (rapidly available P), and 66.1% of (32)P was transformed into Al-P, Fe-P and Ca(8)-P (slowly available P). Only 5.0% of (32)P was transformed into O-P and Ca(10)-P (plant-unavailable P). Moreover, in the soil with P fertilizer applied, (32)P transformation into Ca(2)-P increased, and the transformation into Ca(8)-P + Fe-P + AL-P and O-P, Ca(10)-P significantly decreased compared to the soil with no P fertilizer applied (p < 0.05). This result suggested a higher rate for water-soluble P transformation to slowly available and plant-unavailable P in P deficient soil than in soil with sufficient P. The results of maize L-value determination showed that different genotype maize cultivars had different soil P-use efficiency and low-P tolerance mechanisms. Low-P tolerant cultivar DSY-32 regulated soil P-use efficiency and plant P content according to exogenous P fertilizer application. However, another low-P tolerant cultivar, DSY-2, used soil P more efficiently, regardless of the application of exogenous P.