Amrita Datta

Nrf1 and Nrf2 Transcription Factors Regulate Androgen Receptor Transactivation in Prostate Cancer Cells

Despite androgen deprivation therapy (ADT), persistent androgen receptor (AR) signaling enables outgrowth of castration resistant prostate cancer (CRPC). In prostate cancer (PCa) cells, ADT may enhance AR activity through induction of oxidative stress. Herein, we investigated the roles of Nrf1 and Nrf2, transcription factors that regulate antioxidant gene expression, on hormone-mediated AR transactivation using a syngeneic in vitro model of androgen dependent (LNCaP) and castration resistant (C4-2B) PCa cells. Dihydrotestosterone (DHT) stimulated transactivation of the androgen response element (ARE) was significantly greater in C4-2B cells than in LNCaP cells. DHT-induced AR transactivation was coupled with higher nuclear translocation of p65-Nrf1 in C4-2B cells, as compared to LNCaP cells. Conversely, DHT stimulation suppressed total Nrf2 levels in C4-2B cells but elevated total Nrf2 levels in LNCaP cells. Interestingly, siRNA mediated silencing of Nrf1 attenuated AR transactivation while p65-Nrf1 overexpression enhanced AR transactivation. Subsequent studies showed that Nrf1 physically interacts with AR and enhances AR’s DNA-binding activity, suggesting that the p65-Nrf1 isoform is a potential AR coactivator. In contrast, Nrf2 suppressed AR-mediated transactivation by stimulating the nuclear accumulation of the p120-Nrf1 which suppressed AR transactivation. Quantitative RT-PCR studies further validated the inductive effects of p65-Nrf1 isoform on the androgen regulated genes, PSA and TMPRSS2. Therefore, our findings implicate differential roles of Nrf1 and Nrf2 in regulating AR transactivation in PCa cells. Our findings also indicate that the DHT-stimulated increase in p65-Nrf1 and the simultaneous suppression of both Nrf2 and p120-Nrf1 ultimately facilitates AR transactivation in CRPC cells.

Dysregulation of miR-212 Promotes Castration Resistance through hnRNPH1-Mediated Regulation of AR and AR-V7: Implications for Racial Disparity of Prostate Cancer

Purpose: The causes of disproportionate incidence and mortality of prostate cancer among African Americans (AA) remain elusive. The purpose of this study was to investigate the mechanistic role and assess clinical utility of the splicing factor heterogeneous nuclear ribonucleoprotein H1 (hnRNP H1) in prostate cancer progression among AA men. Experimental Design: We employed an unbiased functional genomics approach coupled with suppressive subtractive hybridization (SSH) and custom cDNA microarrays to identify differentially expressed genes in microdissected tumors procured from age- and tumor grade–matched AA and Caucasian American (CA) men. Validation analysis was performed in independent cohorts and tissue microarrays. The underlying mechanisms of hnRNPH1 regulation and its impact on androgen receptor (AR) expression and tumor progression were explored. Results: Aberrant coexpression of AR and hnRNPH1 and downregulation of miR-212 were detected in prostate tumors and correlate with disease progression in AA men compared with CA men. Ectopic expression of miR-212 mimics downregulated hnRNPH1 transcripts, which in turn reduced expression of AR and its splice variant AR-V7 (or AR3) in prostate cancer cells. hnRNPH1 physically interacts with AR and steroid receptor coactivator-3 (SRC-3) and primes activation of androgen-regulated genes in a ligand-dependent and independent manner. siRNA silencing of hnRNPH1 sensitized prostate cancer cells to bicalutamide and inhibited prostate tumorigenesis in vivo. Conclusions: Our findings define novel roles for hnRNPH1 as a putative oncogene, splicing factor, and an auxiliary AR coregulator. Targeted disruption of the hnRNPH1-AR axis may have therapeutic implications to improve clinical outcomes in patients with advanced prostate cancer, especially among AA men. Clin Cancer Res; 22(7); 1744–56. ©2015 AACR.

Selective targeting of FAK-Pyk2 axis by alpha-naphthoflavone abrogates doxorubicin resistance in breast cancer cells.

Despite an initial positive response, breast cancer cells inevitably acquire resistance to doxorubicin (Dox). Alpha-naphthoflavone (ANF) is a well-known chemopreventive agent; however, its anti-cancer properties have not been established. We examined the therapeutic efficacy of ANF in doxorubicin-resistant MCF-7 (MCF-7/Dox) breast cancer cells and investigated its underlying molecular mechanisms of action. MCF-7/Dox cells expressed constitutively active forms of the tyrosine kinases: focal adhesion kinase (FAK-Y397) and protein tyrosine kinase 2 beta (Pyk2- Y579/580) compared with parental MCF-7 cells. ANF significantly enhanced the sensitivity of MCF-7/Dox cells to Dox cytotoxicity in vitro and when co-administered in vivo. This ANF-mediated chemosensitization has dual mechanisms of action: (a) intracellular Dox retention via suppression of P-glycoprotein pump activity, and (b) inhibition of clonogenic cell survival via de-phosphorylation of FAK, Pyk2, and EGF-induced Akt in MCF-7/Dox cells and tumor xenografts. Because of its strong chemosensitization action, broad safety profile, and health benefits, ANF is an attractive anti-cancer drug with therapeutic implications to circumvent drug resistance in breast cancer patients.

Collagenase Clostridium histolyticum (Xiaflex) for the Treatment of Urethral Stricture Disease in a Rat Model of Urethral Fibrosis

OBJECTIVE To evaluate the treatment effect of collagenase Clostridium histolyticum (CCH) in a rat model of urethral fibrosis. MATERIALS AND METHODS Thirty male Sprague-Dawley rats (300-350 g) were divided into 5 groups. The rat urethra was injected with normal saline in the sham group and, in the other 4 groups, the rat urethra was injected with 10 μg of transforming growth factor beta 1 to create fibrosis of the urethra. Two weeks following transforming growth factor beta 1 injection, the rats were injected with varying doses of CCH or vehicles, depending on their group. The rats were then euthanized at 4 weeks after CCH or vehicle injection. Urethral tissue was harvested for histologic and molecular analyses. Type I and III collagen levels were evaluated by Western blot analysis. RESULTS There was urethral fibrosis and to significant increase in collagen type I and III expressions in the urethral fibrosis group compared with the sham group (P <.05). Urethral injection of CCH appeared to be safe and significantly reduce urethral fibrosis as well as collagen type I and III expressions in the high-dose CCH treatment groups when compared with the treatment control group (P <.01). CONCLUSION This study demonstrated a beneficial effect of CCH injections in a rat model of urethral fibrosis. These findings suggest a potential role for CCH as a therapeutic option in urethral stricture patients and warrant further investigation.

Manumycin A suppresses exosome biogenesis and secretion via targeted inhibition of Ras/Raf/ERK1/2 signaling and hnRNP H1 in castration-resistant prostate cancer cells.

Emerging evidence links exosomes to cancer progression by the trafficking of oncogenic factors and neoplastic reprogramming of stem cells. This necessitates identification and integration of functionally validated exosome-targeting therapeutics into current cancer management regimens. We employed quantitative high throughput screen on two libraries to identify exosome-targeting drugs; a commercially available collection of 1280 pharmacologically active compounds and a collection of 3300 clinically approved compounds. Manumycin-A (MA), a natural microbial metabolite, was identified as an inhibitor of exosome biogenesis and secretion by castration-resistant prostate cancer (CRPC) C4-2B, but not the normal RWPE-1, cells. While no effect was observed on cell growth, MA attenuated ESCRT-0 proteins Hrs, ALIX and Rab27a and exosome biogenesis and secretion by CRPC cells. The MA inhibitory effect is primarily mediated via targeted inhibition of the Ras/Raf/ERK1/2 signaling. The Ras-dependent MA suppression of exosome biogenesis and secretion is partly mediated by ERK-dependent inhibition of the oncogenic splicing factor hnRNP H1. Our findings suggest that MA is a potential drug candidate to suppress exosome biogenesis and secretion by CRPC cells.

Identification of microRNA signature and potential pathway targets in prostate cancer.

Prostate cancer (PC) is the most common and the second leading cause of cancer-related death among American men. Early diagnosis is a prerequisite to improving therapeutic benefits. However, the current clinical biomarkers for PC do not reliably decipher indolent PC from other urogenital disorders. Thus, effective clinical intervention necessitates development of new biomarkers for early detection of PC. The present study aimed to identify the miRNA signature in organ-confined (Gleason Score 6) prostate tumors. MicroRNA (miRNA/miR) array analysis identified 118 upregulated and 73 downregulated miRNAs in microdissected tumors in comparison to matched neighboring normal prostate epithelium. The miRs-Plus-A1083, -92b-5p, -18a-3p, -19a-3p, -639, -3622b-3p, -3189-3p, -155-3p, -410, -1179, 548b-5p, and -4469 are predominantly expressed (7–11-fold), whereas miRs-595, 4490, -3120-5p, -1299, -21-5p, -3677-3, -let-7b-5p, -5189, 3-121-5p, -4518, -200a-5p, -3682-5p, -3689d, -3149 represent the most downregulated (12–113-fold) miRNAs in microdissected prostate tumors. The array expression profile of selected miRNA signature and their potential mRNA targets was validated by qRT-PCR analysis in PC cell lines. Integrated in silico and computational prediction analyses demonstrated that the dysregulated miRNA signature map to key regulatory factors involved in tumorigenesis, including cell cycle, apoptosis, and p53 pathways. The newly identified miRNA signature has potential clinical utility as biomarkers, prognostic indicators, and therapeutic targets for early detection of PC. Further studies are needed to assess the functional significance and clinical usefulness of the identified miRNAs. Impact Statement To our knowledge his is the first study of identifying miRNA signatures in microdissected indolent (Gleason score 6) prostate cancer in comparison to matched normal prostate epithelium. By employing in silico and computational prediction analysis, the study provides a landscape of potential miRNA targets and key cellular pathways involved in prostate tumorigenesis. Identification if miRNAs and their relevant targets and pathways pave the way for underpinning their mechanistic role of miRNAs in human prostate tumorigenesis, and possibly other human cancers. Importantly, the outcome of the study has important clinical implications for the management of prostate cancer, including the use of miRNA(s) as biomarkers for early detection of prostate cancer.

Nanotechnology combined therapy: tyrosine kinase-bound gold nanorod and laser thermal ablation produce a synergistic higher treatment response of renal cell carcinoma in a murine model.

To investigate tyrosine kinase inhibitors (TKI) and gold nanorods (AuNRs) paired with photothermal ablation in a human metastatic clear cell renal cell carcinoma (RCC) mouse model. Nanoparticles have been successful as a platform for targeted drug delivery in the treatment of urological cancers. Likewise, the use of nanoparticles in photothermal tumour ablation, although early in its development, has provided promising results. Our previous in vitro studies of nanoparticles loaded with both TKI and AuNRs and activated with photothermal ablation have shown significant synergistic cell kill greater than each individual arm alone. This study is a translation of our initial findings to an in vivo model.

Pharmacogenomics Dictate Pharmacokinetics: Polymorphisms in Drug-Metabolizing Enzymes and Drug-Transporters

The discovery of a drug is focused on the goal of producing a useful therapeutic agent through a process utilizing the multiple skills and expertise of basic scientists, pharmaceutical chemists, toxicologists, clinical investigators, governmental regulators and clinicians (Mager DE, 2009; Michel MC, 2009; Nagase H, 2011). Drug development and its clinical evaluation is thus a very lengthy and expensive endeavor. One has to first come up with a novel mechanism, identifying relevant target(s) and pathway(s) towards formulation of a new chemical entity (NCE) to treat a disease. Both in vitro and in vivo models that are relevant to the disease form the basis of preclinical testing and identification of lead compounds, and the development of an Investigational New Drug (IND), and ultimately the entry of only a select few into human clinical trials. Therefore, initial studies in drug developments involve the synthesis and extraction of new compounds, their biological screening and pharmacological testing, followed by small animal model testing of toxicology and safety profiles. These early pharmacokinetic (PK) measurements guide researchers to formulate effective pharmaceutical dosage, in vivo stability, elimination and eventually the therapeutic index of lead compound(s). In pre-clinical studies, a favorable PK outcome can lead to the FDA approval for the phase-I, -II and -III clinical evaluation process (Fasolo A, 2009). However, even after clinical approval, drugs have to be continuously monitored towards improvements in their bioavailability, therapeutic, and toxicologic differences especially in a large patient population with patient-specific variability. For example, the azathioprine and mercaptopurine intolerance in patients were found to be linked to the deficiency of a metabolic enzyme, thiopurine S-methyltransferase, and formed the genetic basis for a molecular diagnostic test to designate specific population (Yates CR, et al. 1997). Thus, before testing in humans can start, a significant body of pre-clinical data on PK must be compiled and an appropriate dose should be established to ensure human safety. Toxicology, pharmacology and pharmaceutical sciences all represent the core of pre-

High-throughput screening identified selective inhibitors of exosome biogenesis and secretion: A drug repurposing strategy for advanced cancer

Targeting exosome biogenesis and release may have potential clinical implications for cancer therapy. Herein, we have optimized a quantitative high throughput screen (qHTS) assay to identify compounds that modulate exosome biogenesis and/or release by aggressive prostate cancer (PCa) CD63-GFP-expressing C4-2B cells. A total of 4,580 compounds were screened from the LOPAC library (a collection of 1,280 pharmacologically active compounds) and the NPC library (NCGC collection of 3,300 compounds approved for clinical use). Twenty-two compounds were found to be either potent activators or inhibitors of intracellular GFP signal in the CD63-GFP-expressing C4-2B cells. The activity of lead compounds in modulating the secretion of exosomes was validated by a tunable resistive pulse sensing (TRPS) system (qNano-IZON) and flow cytometry. The mechanism of action of the lead compounds in modulating exosome biogenesis and/or secretion were delineated by immunoblot analysis of protein markers of the endosomal sorting complex required for transport (ESCRT)-dependent and ESCRT-independent pathways. The lead compounds tipifarnib, neticonazole, climbazole, ketoconazole, and triademenol were validated as potent inhibitors and sitafloxacin, forskolin, SB218795, fenoterol, nitrefazole and pentetrazol as activators of exosome biogenesis and/or secretion in PC cells. Our findings implicate the potential utility of drug-repurposing as novel adjunct therapeutic strategies in advanced cancer.

Estradiol-ERβ2 signaling axis confers growth and migration of CRPC cells through TMPRSS2-ETV5 gene fusion

Estrogen receptor beta (ERβ) splice variants are implicated in prostate cancer (PC) progression; however their underlying mechanisms remain elusive. We report that non-canonical activation of estradiol (E2)-ERβ2 signaling axis primes growth, colony-forming ability and migration of the androgen receptor (AR)-null castration-resistant PC (CRPC) cells under androgen-deprived conditions (ADC). The non-classical E2-ERβ2 mediates phosphorylation and activation of Src-IGF-1R complex, which in turn triggers p65-dependent transcriptional upregulation of the androgen-regulated serine protease TMPRSS2:ETV5a/TMPRSS2:ETV5b gene fusions under ADC. siRNA silencing of TMPRSS2 and/or ETV5 suggests that TMPRSS2:ETV5 fusions facilitates the E2-ERβ induced growth and migration effects via NF-κB-dependent induction of cyclin D1 and MMP2 and MMP9 in PC-3 cells. Collectively, our results unravel the functional significance of oncogenic TMPRSS2:ETV5 fusions in mediating growth and migration of E2-ERβ2 signaling axis in CRPC cells. E2-ERβ2 signaling axis may have significant therapeutic and prognostic implications in patients with CRPC.Estrogen receptor beta (ERβ) splice variants are implicated in prostate cancer (PC) progression; however their underlying mechanisms remain elusive. We report that non-canonical activation of estradiol (E2)-ERβ2 signaling axis primes growth, colony-forming ability and migration of the androgen receptor (AR)-null castration-resistant PC (CRPC) cells under androgen-deprived conditions (ADC). The non-classical E2-ERβ2 mediates phosphorylation and activation of Src-IGF-1R complex, which in turn triggers p65-dependent transcriptional upregulation of the androgen-regulated serine protease TMPRSS2:ETV5a/TMPRSS2:ETV5b gene fusions under ADC. siRNA silencing of TMPRSS2 and/or ETV5 suggests that TMPRSS2:ETV5 fusions facilitates the E2-ERβ induced growth and migration effects via NF-κB-dependent induction of cyclin D1 and MMP2 and MMP9 in PC-3 cells. Collectively, our results unravel the functional significance of oncogenic TMPRSS2:ETV5 fusions in mediating growth and migration of E2-ERβ2 signaling axis in CRPC cells. E2-ERβ2 signaling axis may have significant therapeutic and prognostic implications in patients with CRPC.