Two-step Transcriptional Amplification Research Articles

A transcriptional biosensor to monitor single cancer cell therapeutic responses by bioluminescence microscopy.

When several life-prolonging drugs are indicated for cancer treatment, predictive drug-response tumor biomarkers are essential to guide management. Most conventional biomarkers are based on bulk tissue analysis, which cannot address the complexity of single-cell heterogeneity responsible for drug resistance. Therefore, there is a need to develop alternative drug response predictive biomarker approaches that could directly interrogate single-cell and whole population cancer cell drug sensitivity. In this study, we report a novel method exploiting bioluminescence microscopy to detect single prostate cancer (PCa) cell response to androgen receptor (AR)-axis-targeted therapies (ARAT) and predict cell population sensitivity.Methods: We have generated a new adenovirus-delivered biosensor, PCA3-Cre-PSEBC-ITSTA, which combines an integrated two-step transcriptional amplification system (ITSTA) and the activities of the prostate cancer antigen 3 (PCA3) and modified prostate-specific antigen (PSEBC) gene promoters as a single output driving the firefly luciferase reporter gene. This system was tested on PCa cell lines and on primary PCa cells. Single cells, exposed or not to ARAT, were dynamically imaged by bioluminescence microscopy. A linear discriminant analysis (LDA)-based method was used to determine cell population sensitivities to ARAT.Results: We show that the PCA3-Cre-PSEBC-ITSTA biosensor is PCa-specific and can dynamically monitor single-cell AR transcriptional activity before and after ARAT by bioluminescence microscopy. After biosensor transduction and bioluminescence microscopy single-cell luminescence dynamic quantification, LDA analysis could discriminate the cell populations overall ARAT sensitivity despite heterogeneous single-cell responses. Indeed, the biosensor could detect a significant decrease in AR activity following exposure to conventional ARAT in hormone-naive primary PCa cells, while in castration-resistant PCa patients, treatment response correlated with the observed clinical ARAT resistance.Conclusion: The exploitation of bioluminescence microscopy and multi-promoter transcriptionally-regulated biosensors can aptly define the overall treatment response of patients by monitoring live single cell drug response from primary cancer tissue. This approach can be used to develop predictive biomarkers for drug response in order to help clinicians select the best drug combinations or sequences for each patient.

Limited potential of AAV-mediated gene therapy in transducing human mesenchymal stem cells for bone repair applications.

Adeno-associated viral vectors (AAV) are unique in their ability to transduce a variety of both dividing and nondividing cells, with significantly lower risk of random genomic integration and with no known pathogenicity in humans, but their role in ex vivo regional gene therapy for bone repair has not been definitively established. The goal of this study was to test the ability of AAV vectors carrying the cDNA for BMP-2 to transduce human mesenchymal stem cells (MSCs), produce BMP-2, and induce osteogenesis in vitro as compared with lentiviral gene therapy with a two-step transcriptional amplification system lentiviral vector (LV-TSTA). To this end, we created two AAV vectors (serotypes 2 and 6) expressing the target transgene; eGFP or BMP-2. Transduction of human MSCs isolated from bone marrow (BMSCs) or adipose tissue (ASCs) with AAV2-eGFP and AAV6-eGFP led to low transduction efficiency (BMSCs: 3.57% and 8.82%, respectively, ASCs: 6.17 and 20.2%, respectively) and mean fluorescence intensity as seen with FACS analysis 7 days following transduction, even at MOIs as high as 106. In contrast, strong eGFP expression was detectable in all of the cell types post transduction with LV-TSTA-eGFP. Transduction with BMP-2 producing vectors led to minimal BMP-2 production in AAV-transduced cells 2 and 7 days following transduction. In addition, transduction of ASCs and BMSCs with AAV2-BMP-2 and AAV6-BMP-2 did not enhance their osteogenic potential as seen with an alizarin red assay. In contrast, the LV-TSTA-BMP-2-transduced cells were characterized by an abundant BMP-2 production and induction of the osteogenic phenotype in vitro (p < 0.001 vs. AAV2 and 6). Our results demonstrate that the AAV2 and AAV6 vectorscannot induce a significant transgene expression in human BMSCs and ASCs, even at MOIs as high as 106. The LV-TSTA vector is significantly superior in transducing human MSCs; thus this vector would be preferable when developing an ex vivo regional gene therapy strategy for clinical use in orthopedic surgery applications.

Abstract 2015: A transcriptionally enhanced biosensor to detect and monitor biopsy-dissociated primary prostate cancer single cell drug responses by bioluminescence microscopy

Abstract Background: In the past decade, the therapeutic landscape of metastatic castration resistant prostate cancer (mCRPC) has been transformed with the introduction of novel pharmaceutical agents including novel antiandrogens (nAA) such as darolutamide, enzalutamide or apalutamide. Currently, the management of mCRPC is mainly based on biomarkers obtained from the patient's blood or bulk tumor samples, which do not take into account for prostate cancer (PCa) cell heterogeneity. Objectives: To develop a bioluminescence imaging technology enabling: 1) the detection of PCa single cells from dissociated biopsies and 2) single cell nAA sensitivity assessment. Methods: The PCA3 promoter (PCa specific) and PSEBC promoter (androgen receptor-driven to monitor response to nAA therapy) have been incorporated in the non-replicating adenoviral multi-promoter integrated two-step transcriptional amplification system (MP-ITSTA) that allows imaging of complementary activities of two different promoters by a single output reporter gene. Thus, PCA3/PSEBC-ITSTA system was designed to monitor androgen receptor (AR) activity specifically within each single PCa cell by bioluminescence microscopy. Prostatic biopsies were dissociated in the presence of collagenase II and DNase for 18h. PCa cell lines or fresh biopsies-dissociated cancer cells were transduced for 72h and then covered with an extracellular matrix gel. Single cell bioluminescence microscopy images were done before and after exposure to DHT or DHT+AA to specifically monitoring therapy response. Changes in cell number and luminescence intensity after AA were normalized to the DHT group to exclude non-specific cell-death due to infection or time spent in culture. Results: PCA3/PSEBC-ITSTA was specific to PCa cell lines. By determining the ratio of AR active cells before and after DHT or DHT+AA treatment in culture, PCA3-Cre-PSEBC-ITSTA was able to determine the AA sensitivity of LNCaP (sensitive), LAPC4 (moderately resistant) and 22Rv1 (resistant) PCa cell lines. Also, our method could detect and monitor AA sensitivity of primary PCa cells harvested from eight radical prostatectomy specimens. PCA3/PSEBC-ITSTA could dynamically quantify AR transcriptional activity during enzalutamide or bicalutamide treatments, in a dose dependent manner, and could unveil tumor AA response heterogeneity. As expected, inhibition of AR activity was stronger with enzalutamide than with bicalutamide. Conclusions: Our bioluminescence microscopy-based biosensor could detect primary PCa cells in culture and it allows dynamic evaluation of AA sensitivity at a single-cell level in a heterogeneous cell population harvested from radical prostatectomy biopsies. We believe our approach opens to a novel field of treatment response predictive tools for cancer treatment decision-making. Citation Format: Audrey Champagne, Pallavi Jain, Bertrand Neveu, Frédéric Pouliot. A transcriptionally enhanced biosensor to detect and monitor biopsy-dissociated primary prostate cancer single cell drug responses by bioluminescence microscopy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2015.

Exploiting the transcriptional specificity of the alpha-methylacyl-CoA racemase AMACR promoter for the molecular imaging of prostate cancer.

The metabolic protein alpha-methylacyl-CoA racemase (AMACR) is significantly overexpressed in prostate cancer compared to the normal prostate and other non-malignant tissue. Though an attractive target, there are no reports in the literature on leveraging the expression of AMACR for the molecular imaging of prostate cancer. Here, we used a molecular-genetic imaging strategy to exploit the transcriptional specificity of the AMACR promoter for the in vivo detection of prostate cancer using the reporter gene luciferase. We performed a stepwise truncation of the promoter and identified a 565 base pair minimal promoter for AMACR that retained both high activity and specificity. Following identification of the minimal promoter for AMACR, we used an advanced two-step transcriptional amplification system to maximize the promoter output. We showed that our optimized AMACR promoter can drive expression of luciferase for molecular imaging in subcutaneous xenograft models of androgen receptor-positive and androgen receptor-negative prostate cancer using a non-replicative adenovirus for gene delivery. Our results provide evidence that the AMACR promoter can be exploited to drive the cancer-specific expression of reporter genes and potentially even be incorporated into conditionally replicative adenoviruses for oncolytic therapy and other applications.

In vitro evaluation of a lentiviral two-step transcriptional amplification system using GAL4FF transactivator for gene therapy applications in bone repair.

In this study, we developed a lentiviral two-step transcriptional amplification (TSTA) system expressing bone morphogenetic protein-2 (BMP-2) under the control of a GAL4FF transactivator to enhance gene expression and limit toxicity for bone repair applications. To this end human MSCs, isolated from bone marrow or adipose tissue, were transduced overnight with a LV-TSTA system (GAL4FF or GAL4vp16) expressing BMP-2 or GFP and evaluated in vitro for transduction efficiency, mean fluorescence intensity, cell viability, and BMP-2 production. FACS analysis of GFP-transduced MSCs confirmed successful transduction with the GAL4FF+GFP vector. Moreover, ELISA demonstrated abundant BMP-2 production by GAL4FF+BMP2-transduced human MSCs over a period of 8 weeks, with minimal cytotoxicity at all time points. Compared to GAL4vp16, GAL4FF was superior with respect to BMP production at 1, 2, 4, 6, and 8 weeks in BMSCs. In ASCs, GAL4FF was still associated with higher BMP-2 production at weeks 2-8, but this difference was not as prominent as in BMSCs. To our knowledge, this is the first report of GAL4FF-mediated BMP-2 production by human BMSCs and ASCs. Compared to the standard GAL4vp16TSTA vector, GAL4FF was associated with lower cytotoxicity and higher in vitro gene expression in both BMSCs and ASCs.

Therapeutic effect of targeted Fas-expressing adenoviruses method combining γδ T cells in a mouse model of human ovarian carcinoma

The present study aimed to investigate the therapeutic effect and safety of targeted use of Fas-expressing adenoviruses combined with γδ T cell-mediated killing to treat human ovarian cancer xenografts in BALB/c mice. Shuttle plasmids containing control elements of human telomerase reverse transcriptase promoter and two-step transcriptional amplification system were constructed and packaged into adenovirus-5 vectors to generate expression of an exogenous Fas gene. A mouse xenograft model of human ovarian carcinoma was constructed. A total of 35 BALB/c mice were randomly divided into five groups, which were injected with PBS, γδ T cells, Fas-expressing adenoviruses, taxol, or Fas-expressing adenovirus and γδ T cells. The weight and volume of tumors in mice in each group was monitored. Tissue sections of the various tissues of mice in the Fas-expressing adenovirus and γδ T cells group was compared with those in the PBS group to evaluate the safety of Fas-expressing adenovirus and γδ T cells in the treatment of human ovarian cancer xenograft tumors. The results of the present study indicated that mice in all treatment groups were alive at the end of the treatment course. Tumor weight and volume was the highest in the PBS group, followed successively by the adenovirus group, the γδ T cell group, the adenovirus and γδ T cell group, and the taxol group. The weight and volume inhibition rate in adenovirus and γδ T cell group were significantly higher compared with in the PBS group (P<0.05). Pathological observation of tissue samples revealed that none of vital organs in the adenovirus and γδ T cell group developed any evident morphological changes during treatment, when compared with healthy controls. In conclusion, the combined therapy with Fas-expressing adenoviruses and γδ T cells is efficient and safe for the treatment of mouse human ovarian carcinoma xenografts.

Gene Therapy for Bone Repair Using Human Cells: Superior Osteogenic Potential of Bone Morphogenetic Protein 2-Transduced Mesenchymal Stem Cells Derived from Adipose Tissue Compared to Bone Marrow.

Ex vivo regional gene therapy strategies using animal mesenchymal stem cells genetically modified to overexpress osteoinductive growth factors have been successfully used in a variety of animal models to induce both heterotopic and orthotopic bone formation. However, in order to adapt regional gene therapy for clinical applications, it is essential to assess the osteogenic capacity of transduced human cells and choose the cell type that demonstrates the best clinical potential. Bone-marrow stem cells (BMSC) and adipose-derived stem cells (ASC) were selected in this study for in vitro evaluation, before and after transduction with a lentiviral two-step transcriptional amplification system (TSTA) overexpressing bone morphogenetic protein 2 (BMP-2; LV-TSTA-BMP-2) or green fluorescent protein (GFP; LV-TSTA-GFP). Cell growth, transduction efficiency, BMP-2 production, and osteogenic capacity were assessed. The study demonstrated that BMSC were characterized by a slower cell growth compared to ASC. Fluorescence-activated cell sorting analysis of GFP-transduced cells confirmed successful transduction with the vector and revealed an overall higher but not statistically significant transduction efficiency in ASC versus BMSC (90.2 ± 4.06% vs. 80.4 ± 8.51%, respectively; p = 0.146). Enzyme-linked immunosorbent assay confirmed abundant BMP-2 production by both cell types transduced with LV-TSTA-BMP-2, with BMP-2 production being significantly higher in ASC versus BMSC (239.5 ± 116.55 ng vs. 70.86 ± 24.7 ng; p = 0.001). Quantitative analysis of extracellular deposition of calcium (Alizarin red) and alkaline phosphatase activity showed that BMP-2-transduced cells had a higher osteogenic differentiation capacity compared to non-transduced cells. When comparing the two cell types, ASC/LV-TSTA-BMP-2 demonstrated a significantly higher mineralization potential compared to BMSC/LV-TSTA-BMP-2 7 days post transduction (p = 0.014). In conclusion, this study demonstrates that transduction with LV-TSTA-BMP-2 can significantly enhance the osteogenic potential of both human BMSC and ASC. BMP-2-treated ASC exhibited higher BMP-2 production and greater osteogenic differentiation capacity compared to BMP-2-treated BMSC. These results, along with the fact that liposuction is an easy procedure with lower donor-site morbidity compared to BM aspiration, indicate that adipose tissue might be a preferable source of MSCs to develop a regional gene therapy approach to treat difficult bone-repair scenarios.

MP45-08 STABILIZATION OF INVADOPODIA BY PLECTIN- MEDIATED CONJUNCTION TO VIMENTIN INTERMEDIATE FILAMENT IS A CRITICAL MOLECULAR STEP OF INVASION AND EXTRAVASATION FOR METASTASIS IN BLADDER CANCER.

You have accessJournal of UrologyBladder Cancer: Basic Research & Pathophysiology I1 Apr 2016MP45-08 STABILIZATION OF INVADOPODIA BY PLECTIN- MEDIATED CONJUNCTION TO VIMENTIN INTERMEDIATE FILAMENT IS A CRITICAL MOLECULAR STEP OF INVASION AND EXTRAVASATION FOR METASTASIS IN BLADDER CANCER. Mihoko Sutoh Yoneyama, Shingo Hatakeyama, Tomonori Habuchi, Takamitsu Inoue, Toshiya Nakamura, Tomihisa Funyu, Gerhard Wiche, Shigeru Tsuboi, and Chikara Ohyama Mihoko Sutoh YoneyamaMihoko Sutoh Yoneyama More articles by this author , Shingo HatakeyamaShingo Hatakeyama More articles by this author , Tomonori HabuchiTomonori Habuchi More articles by this author , Takamitsu InoueTakamitsu Inoue More articles by this author , Toshiya NakamuraToshiya Nakamura More articles by this author , Tomihisa FunyuTomihisa Funyu More articles by this author , Gerhard WicheGerhard Wiche More articles by this author , Shigeru TsuboiShigeru Tsuboi More articles by this author , and Chikara OhyamaChikara Ohyama More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.285AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES To investigate the molecular mechanisms of bladder cancer (BCa) metastasis, we previously isolated a high-metastatic BCa cell subpopulation from a low-metastatic cell line by using an in vivo selection system (Sugiyama et al Oncol. Res. 20, 289-295). The high-metastatic BCa cell subpopulation showed a high ability to form invadopodia, the filamentous (F-) actin-based membrane protrusions that play an essential role in cancer cell invasion. Analysis of gene expression profiles revealed that the expression of an intermediate filament (IF) protein, vimentin and a cytoskeletal linker protein, plectin was up-regulated in the high-metastatic BCa cells compared with the low-metastatic BCa cell line. Here we report a novel molecular mechanism of invasive bladder cancer cell extravasation using vimentin IF and plectin. METHODS Six human BCa cell lines (RT-4, 5637, KK-47, T24, BOY and YTS-1) and primary culture of BCa cells from three genetically independent patients were used. The expression of vimentin and plectin in BCa cells was assessed by immunoblotting. The interaction between vimentin and plectin was examined by immunoprecipitation. The spatial correlation between vimentin, plectin and F-actin in BCa cells was analyzed by confocal microscopy. To evaluate the functions of invadopodia, cells were assayed for extracellular matrix (ECM) degradation, Matrigel invasion, transendothelial invasion and lung metastasis. RESULTS In invasive BCa cells, the expression levels of vimentin and plectin were elevated and the vimentin IF-plectin-invadopodia F-actin link was formed. Disruption of this link severely impaired invadopodia formation, reducing the capacities of ECM degradation, Matrigel invasion, transendothelial invasion and metastasis. In addition, the vimentin assembly into the filaments was required for invadepodia formation. CONCLUSIONS Our results strongly suggest that plectin anchoring invadopodia to vimentin IF scaffolds and stabilizes invadopodia, which is a critical molecular step for BCa cell invasion and extravasation for metastasis. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e610-e611 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Mihoko Sutoh Yoneyama More articles by this author Shingo Hatakeyama More articles by this author Tomonori Habuchi More articles by this author Takamitsu Inoue More articles by this author Toshiya Nakamura More articles by this author Tomihisa Funyu More articles by this author Gerhard Wiche More articles by this author Shigeru Tsuboi More articles by this author Chikara Ohyama More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

792 Advanced two-step transcriptional amplification as a novel system for cancer-specific gene expression and imaging

792 Advanced two-step transcriptional amplification as a novel system for cancer-specific gene expression and imaging

Noninvasive Imaging of Hypoxia-Inducible Factor-1α Gene Therapy for Myocardial Ischemia

Hypoxia-inducible factor-1 alpha (HIF-1α) gene therapy holds great promise for the treatment of myocardial ischemia. Both preclinical and clinical evaluations of this therapy are underway and can benefit from a vector strategy that allows noninvasive assessment of HIF-1α expression as an objective measure of gene delivery. We have developed a novel bidirectional plasmid vector (pcTnT-HIF-1α-VP2-TSTA-fluc), which employs the cardiac troponin T (cTnT) promoter in conjunction with a two-step transcriptional amplification (TSTA) system to drive the linked expression of a recombinant HIF-1α gene (HIF-1α-VP2) and the firefly luciferase gene (fluc). The firefly luciferase (FLuc) activity serves as a surrogate for HIF-1α-VP2 expression, and can be noninvasively assessed in mice using bioluminescence imaging after vector delivery. Transfection of cultured HL-1 cardiomyocytes with pcTnT-HIF-1α-VP2-TSTA-fluc led to a strong correlation between FLuc and HIF-1α-dependent vascular endothelial growth factor expression (r(2)=0.88). Intramyocardial delivery of pcTnT-HIF-1α-VP2-TSTA-fluc into infarcted mouse myocardium led to persistent HIF-1α-VP2 expression for 4 weeks, even though it improved neither CD31+ microvessel density nor echocardiographically determined left ventricular systolic function. These results lend support to recent findings of suboptimal efficacy associated with plasmid-mediated HIF-1α therapy. The imaging techniques developed herein should be useful for further optimizing HIF-1α-VP2 therapy in preclinical models of myocardial ischemia.

A Titratable Two-Step Transcriptional Amplification Strategy for Targeted Gene Therapy Based on Ligand-Induced Intramolecular Folding of a Mutant Human Estrogen Receptor

The efficacy and safety of cardiac gene therapy depend critically on the level and the distribution of therapeutic gene expression following vector administration. We aimed to develop a titratable two-step transcriptional amplification (tTSTA) vector strategy, which allows modulation of transcriptionally targeted gene expression in the myocardium. We constructed a tTSTA plasmid vector (pcTnT-tTSTA-fluc), which uses the cardiac troponin T (cTnT) promoter to drive the expression of the recombinant transcriptional activator GAL4-mER(LBD)-VP2, whose ability to transactivate the downstream firefly luciferase reporter gene (fluc) depends on the binding of its mutant estrogen receptor (ER(G521T)) ligand binding domain (LBD) to an ER ligand such as raloxifene. Mice underwent either intramyocardial or hydrodynamic tail vein (HTV) injection of pcTnT-tTSTA-fluc, followed by differential modulation of fluc expression with varying doses of intraperitoneal raloxifene prior to bioluminescence imaging to assess the kinetics of myocardial or hepatic fluc expression. Intramyocardial injection of pcTnT-tTSTA-fluc followed by titration with intraperitoneal raloxifene led to up to tenfold induction of myocardial fluc expression. HTV injection of pcTnT-tTSTA-fluc led to negligible long-term hepatic fluc expression, regardless of the raloxifene dose given. The tTSTA vector strategy can effectively modulate transgene expression in a tissue-specific manner. Further refinement of this strategy should help maximize the benefit-to-risk ratio of cardiac gene therapy.

A Molecular Imaging System Based on Both Transcriptional and Genomic Amplification to Detect Prostate Cancer Cells In Vivo

An imaging modality that can accurately discern prostate cancer (PCa) foci would be useful to detect PCa early or guide treatment. We have engineered numerous adenoviral vectors (Ads) to carry out reporter gene-based imaging using specific promoters to express a potent transcriptional activator, which in turn activates the reporter gene in PCa. This two-step transcriptional amplification (TSTA) method can boost promoters' activity, while maintaining cell specificity. Here, we examined a dual TSTA (DTSTA) approach, which utilizes TSTA not only to express the imaging reporter, but also to direct viral genome replication of a conditionally replicating Ad (CRAd) to further augment the expression levels of the reporter gene by genomic amplification supported in trans by coadministered CRAd. In vitro studies showed up to 50-fold increase of the reporter genome by DTSTA. Compared with TSTA reporter alone, DTSTA application exhibited a 25-fold increase in imaging signal in PCa xenografts. DTSTA approach is also beneficial for a combination of two TSTA Ads with distinct promoters, although amplification is observed only when TSTA-CRAd can replicate. Consequently, the DTSTA approach is a hybrid method of transcriptional and genomic augmentation that can provide higher level reporter gene expression potentially with a lower dose of viral administration.

Abstract 354: Monitor androgen blockade therapy with functional androgen receptor reporting system

Abstract Hormonal manipulation remains the first line treatment for advanced prostate cancer. It includes surgical and medical means of androgen deprivation and androgen receptor (AR) blockade therapies. However, the majority of patients will develop castration resistant prostate cancer, often with metastasis that accounts for the lethality of this disease. Therefore, a reliable imaging modality capable of active surveillance of tumor recurrence and/or new incidence of metastasis would greatly benefit the timing and decision-making in adopting second line therapies. To this end, we recently constructed a prostate specific yet androgen independent promoter system, namely PSES-TSTA (Prostate Specific Enhancer Sequence coupled with Two-Step Transcriptional Amplification). We used this system to drive PET and optical imaging reporters and successfully visualized subcutaneous tumor and intra-tibial metastasis in castrated mice. The androgen independency of PSES-TSTA, which secured viability of this imaging approach when only castrated level of androgen is available, is attributed to the composition of the chimeric PSES sequence - an androgen inducible element derived from the prostate specific antigen (PSA) gene promoter and an androgen suppressible element from the prostate specific membrane antigen gene enhancer (PSME). Another challenge faced by patients after hormonal ablation therapy is the need for effective second-line therapies. Interestingly, a growing body of evidence points out that even at castration resistant stage, AR remains active and most prostate cancer still rely on AR signaling axis for proliferation and survival. Accordingly, much effort has been devoted to the development of second generation anti-androgen agents. Therefore, it would be greatly beneficial to establish a practical and reliable reporting system that reflects the functional status of the androgen-AR axis so that the efficacy of such new drugs can be monitored at the molecular level. Inspired by previous results, we separated the two components of PSES and generated two imaging reporters: PSA-driven Firefly Luciferase (PSA-FL) and PSME-driven Renilla Luciferase (PSME-RL). Based on their respective response to androgen signaling, we anticipated that the PSA-FL signal will decrease while the PSME-RL signal will increase in the face of an effective anti-androgen therapy. Indeed, we observed such pattern of reporter gene expression in multiple prostate cancer cell lines. Importantly, this system is able to differentiate the potency and efficacy between the first generation and the more potent second generation AR antagonists. Moreover, the simultaneous application of the PSME- and PSA-driven reporter system is advantageous over the single PSA promoter-based reporter in that it rules out the effect of tumor mass reduction on the readout because both up- and down-regulation of gene expression are being assessed and imaged. 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 354. doi:1538-7445.AM2012-354

Abstract 5654: Novel tissue-targeted virogeneimaging system for squamous cell carcinoma therapy expressing cell cycle regulator cdk2ap1

Abstract Oral squamous cell carcinoma (OSCC) affects about 30,000 Americans each year, and although the overall prognosis has improved in recent years for localized carcinomas, metastases can decrease survival rates by half. For tongue and palate lesions, surgery is usually the initial treatment, but metastases aggressively develop at sites where conventional therapies are ineffective. Therefore, our goal has been to develop more effective therapeutic modalities for the disease utilizing expression of cell cycle arrest and apoptosis-modulating genes. Our efforts have focused on gaining understanding of the biology and therapeutic potential of p12cdk2ap1 (p12), an S-phase growth suppressor and proapoptotic gene commonly downregulated in OSCC. In vivo, we have showed that expressing p12 using a nonviral vector can result in effective reduction in tumor size and a dramatically altered tumor phenotype. Moreover, we have showed that p12 can have cell growth inhibitory effects in a cell-autonomous as well as non-cell autonomous manner, rendering expression of this cell cycle regulator a very promising new gene therapy strategy. Therefore, we hypothesized that this growth regulator molecule will comprise a highly efficient antiumor gene therapy for OSCC. We have developed a novel viral delivery vector system with high activity and high specificity expression in oral tumor cells. This Adenovirus (Ad) utilizes a two-step transcriptional amplification system driven by the SCCA2 promoter and a bidirectional target cassette containing the sequences for the p12 and ether firefly luciferase (Luc) or thymidine kinase (TK) imaging genes. We constructed and are characterizing novel configurations of these dE1dE3 Ad-SCCA2-p12/Luc or p12/TK bidirectional vectors for gene therapy and virogeneimaging (VGI) applications. We are currently testing the specificity of these vectors and their effectiveness in tumor growth inhibition at either floor of mouth, orthotopic, or distant sites following intratumoral or systemic administration. We propose VGI can be adapted to a nonviral system as well and may hold promise not only as a novel SCC-specific gene therapy but perhaps as a molecular imaging detection agent for tumor cells that have metastasized to distant and thus difficult to treat sites. 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 5654. doi:1538-7445.AM2012-5654

A novel gene expression system for detecting viable bladder cancer cells

A novel transcriptional system was developed that can robustly enhance cancer-specific gene expression. In the system, hTERT promoter-driven gene expression was enhanced by an advanced two-step transcriptional amplification (TSTA). This construct was used to develop a novel system for detection of bladder cancer cells. The current study evaluated the advanced TSTA system by examining the cancer-specific gene transcription in various bladder cancer cell lines. The system significantly enhanced cancer-specific luciferase gene expression in the bladder cancer cell lines in comparison to the previous expression system of one-step or conventional TSTA. The fold gain of the enhancement was significantly correlated to the telomerase activity of the cell lines. A green fluorescent protein (GFP) gene encoding plasmid vector was constructed where hTERT promoter-driving transcription is enhanced by the advanced TSTA to utilize the system for the imaging and detection of viable bladder cancer cells. The advanced TSTA-hTERT-GFP plasmid successfully induced cancer-specific gene expression, showing robust GFP expression in human bladder cancer cell lines, but no visible GFP expression in normal bladder urothelial cells. The control GFP plasmid with a CMV promoter yielded GFP expression in both normal bladder cells and cancer cells. The advanced TSTA-hTERT-GFP plasmid allowed selective visualization of viable human bladder cancer cells in mixed cell culture containing 10- and 100-fold more normal bladder urothelial cells. These findings indicate that the advanced TSTA-hTERT expressional system is a valuable tool for detecting viable bladder cancer cells. The current system can be applied for in vitro detection of bladder cancer cells in urine and other types of cancer cells disseminated in vivo.

Intratumoral versus Intravenous Gene Therapy Using a Transcriptionally Targeted Viral Vector in an Orthotopic Hepatocellular Carcinoma Rat Model

PurposeTo evaluate the feasibility of intratumoral delivery of adenoviral vector carrying a bidirectional two-step transcriptional amplification (TSTA) system to amplify transcriptional strength of cancer-specific Survivin promoter in a hepatocellular carcinoma model. Materials and MethodsMCA-RH7777 cells were implanted in rat liver, and tumor formation was confirmed with [18F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). The adenoviral vector studied had Survivin promoter driving a therapeutic gene (tumor necrosis factor-α–related apoptosis-inducing ligand [TRAIL]) and a reporter gene (firefly luciferase [FL]; Ad-pSurvivin-TSTA-TRAIL-FL). Tumor-bearing rats were administered Ad-pSurvivin-TSTA-TRAIL-FL intravenously (n = 7) or intratumorally (n = 8). For control groups, adenovirus FL under cytomegalovirus (CMV) promoter (Ad-pCMV-FL) was administered intravenously (n = 3) or intratumorally (n = 3). One day after delivery, bioluminescence imaging was performed to evaluate transduction. At 4 and 7 days after delivery, 18F-FDG-PET was performed to evaluate therapeutic efficacy. ResultsWith intravenous delivery, Ad-pSurvivin-TSTA-TRAIL-FL showed no measurable liver tumor FL signal on day 1 after delivery, but showed better therapeutic efficacy than Ad-pCMV-FL on day 7 (PET tumor/liver ratio, 3.5 ± 0.58 vs 6.0 ± 0.71; P = .02). With intratumoral delivery, Ad-pSurvivin-TSTA-TRAIL-FL showed positive FL signal from all tumors and better therapeutic efficacy than Ad-pCMV-FL on day 7 (2.4 ± 0.50 vs 5.4 ± 0.78; P = .01). In addition, intratumoral delivery of Ad-pSurvivin-TSTA-TRAIL-FL demonstrated significant decrease in tumoral viability compared with intravenous delivery (2.4 ± 0.50 vs 3.5 ± 0.58; P = .03). ConclusionsIntratumoral delivery of a transcriptionally targeted therapeutic vector for amplifying tumor-specific effect demonstrated better transduction efficiency and therapeutic efficacy for liver cancer than systemic delivery, and may lead to improved therapeutic outcome for future clinical practice.

Androgen-Independent Molecular Imaging Vectors to Detect Castration-Resistant and Metastatic Prostate Cancer

Prostate-specific promoters are frequently employed in gene-mediated molecular imaging and therapeutic vectors to diagnose and treat castration-resistant prostate cancer (CRPC) that emerges from hormone ablation therapy. Many of the conventional prostate-specific promoters rely on the androgen axis to drive gene expression. However, considering the cancer heterogeneity and varying androgen receptor status, we herein evaluated the utility of prostate-specific enhancing sequence (PSES), an androgen-independent promoter in CRPC. The PSES is a fused enhancer derived from the prostate-specific antigen (PSA) and prostate-specific membrane antigen gene regulatory region. We augmented the activity of PSES by the two-step transcriptional amplification (TSTA) system to drive the expression of imaging reporter genes for either bioluminescent or positron emission tomography (PET) imaging. The engineered PSES-TSTA system exhibits greatly elevated transcriptional activity, androgen independency, and strong prostate specificity, verified in cell culture and preclinical animal experimentations. These advantageous features of PSES-TSTA elicit superior gene expression capability for CRPC in comparison with the androgen-dependent PSA promoter-driven system. In preclinical settings, we showed robust PET imaging capacity of PSES-TSTA in a castrated prostate xenograft model. Moreover, intravenous administrated PSES-TSTA bioluminescent vector correctly identified tibial bone marrow metastases in 9 of 9 animals, whereas NaF- and FDG-PET was unable to detect the lesions. Taken together, this study showed the promising utility of a potent, androgen-independent, and prostate cancer-specific expression system in directing gene-based molecular imaging in CRPC, even in the context of androgen deprivation therapy.

Advanced two-step transcriptional amplification as a novel method for cancer-specific gene expression and imaging

The two-step transcriptional amplification (TSTA) system was previously reported to enhance the tissue-specific gene expression driven by weak promoters, but the enhancement of the gene expression is limited to use in invitro and invivo experimental situations. To achieve robust tissue-specific gene expression using the TSTA system, we developed an advanced TSTA system which includes polyglutamines and rat glucocorticoid receptor sequences between the GAL4 and VP16 sequences in the region of the first step of transcription. We evaluated the advanced TSTA system as a method to enhance the human telomerase reverse transcriptase (hTERT) promoter-driving cancer-specific transcription in various cancer cell lines. As a result, the advanced TSTA enhanced cancer-specific luciferase gene expression in all of the examined cancer cell lines, when compared with both the one-step and conventional TSTA systems (an ~6- and ~17-fold enhancement, respectively). Notably, the enhancement of the hTERT driven expression by the conventional TSTA system was modest and even inferior to the one-step system in several cancer cell lines. We then constructed a luciferase gene encoding the adeno-associated virus vector in which the hTERT promoter-mediated expression was driven by the advanced TSTA or control systems. In an orthotopic liver tumor model, mice were treated with the vector via tail vein injection. An optical imaging device was used to visualize the in vivo luciferase expression in the orthotopic tumor. The advanced TSTA system significantly enhanced the luciferase expression compared with the one-step and conventional TSTA systems (18.0±1.0- and 15.9±0.85-fold gain, respectively). Therefore, the advanced TSTA system significantly improves hTERT-dependent cancer-specific gene expression both invitro and in vivo when compared with the previous systems. Since the advanced TSTA method can also be applied to other site-specific gene expression systems using tissue-specific promoters, this approach is expected to become a valuable tool enabling in vivo site-specific targeting in the field of gene therapy and molecular imaging.

In Vivo Imaging of Intraprostatic-Specific Gene Transcription by PET

Better intraprostatic cancer imaging techniques are needed to guide clinicians in prostate cancer treatment decisions. Because many genes are specifically overexpressed in cancer cells, one strategy to improve prostate cancer detection is to image intraprostatic cancer-specific transcriptional activity. Because of the obstacles of weak cancer- or tissue-specific promoter activity and bladder clearance of many PET tracers, intraprostatic PET of gene transcriptional activity has not been previously reported. The two-step transcriptional amplification (TSTA) system that amplifies the prostate-specific antigen promoter activity was used for PET imaging of the reporter gene herpes simplex virus type-1 sr39 thymidine kinase (HSV1-sr39tk). The TSTA-sr39tk system was injected directly into prostates or prostatic tumors as a replication-incompetent adenovirus (AdTSTA-sr39tk) and imaged using PET. AdTSTA-sr39tk was able to image prostate-specific antigen promoter transcriptional activity by 9-(4-(18)F-fluoro-3-[hydroxymethyl]butyl)guanine PET, in both mouse and canine prostates in vivo. Ex vivo small-animal PET images, scintigraphic counts, and sr39tk expression analysis confirmed the specificity of the observed signal. Here, by combining the TSTA-amplified signal with a protocol for tracer administration, we show that in vivo PET detection of transcriptional activity is possible in both mouse and immunocompetent canine prostates. These results suggest that imaging applications using transcription-based tumor-specific promoters should be pursued to better visualize cancer foci that escape detection by conventional biopsies.

Abstract 5414: Novel tissue-targeted adenoviral vector for squamous cell carcinoma therapy expressing cell cycle regulator cdk2ap1 and molecular imaging genes

Abstract Oral squamous cell carcinoma (OSCC) affects about 30,000 Americans each year, and although the overall prognosis has improved in recent years for localized carcinomas, metastases can decrease survival rates by half. For tongue and palate lesions, surgery is usually the initial treatment, but metastases aggressively develop at sites where conventional therapies are ineffective. Therefore, our goal has been to develop more effective therapeutic modalities for the disease utilizing expression of cell cycle arrest and apoptosis-modulating genes. Our efforts have focused on gaining understanding of the biology and therapeutic potential of p12cdk2ap1 (p12), an S-phase growth suppressor and proapoptotic gene commonly downregulated in OSCC. In vivo, we have showed that expressing p12 using a nonviral vector can result in effective reduction in tumor size and a dramatically altered tumor phenotype. Moreover, we have showed that p12 can have cell growth inhibitory effects in a cell-autonomous as well as non-cell autonomous manner, rendering expression of this cell cycle regulator a very promising new gene therapy strategy. Therefore, we hypothesized that this growth regulator molecule will comprise a highly efficient antiumor gene therapy for OSCC. We have developed a novel viral delivery vector system with high activity and high specificity expression in oral tumor cells. This Adenovirus (Ad) utilizes a two-step transcriptional amplification system driven by the SCCA2 promoter and a bidirectional target cassette containing the sequences for the p12 and ether firefly luciferase (Luc) or thymidine kinase (TK) imaging genes. We constructed and are characterizing novel configurations of these dE1dE3 Ad-SCCA2-p12/Luc or p12/TK bidirectional vectors for gene therapy and molecular imaging applications. We are currently testing the specificity of these vectors and their effectiveness in tumor growth inhibition at either floor of mouth, orthotopic, or distant sites following intratumoral or systemic administration. We propose this new vector design may hold promise not only as a novel SCC-specific gene therapy but perhaps as a molecular imaging detection agent for tumor cells that have metastasized to distant and thus difficult to treat sites. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5414. doi:10.1158/1538-7445.AM2011-5414