Adeno-associated virus 2-mediated intratumoral prostate cancer gene therapy: long-term maspin expression efficiently suppresses tumor growth

Adeno-associated virus as a delivery vector for gene therapy of human diseases

Adeno-associated virus (AAV) has emerged as a pivotal delivery tool in clinical gene therapy owing to its minimal pathogenicity and ability to establish long-term gene expression in different tissues. Recombinant AAV (rAAV) has been engineered for enhanced specificity and developed as a tool for treating various diseases. However, as rAAV is being more widely used as a therapy, the increased demand has created challenges for the existing manufacturing methods. Seven rAAV-based gene therapy products have received regulatory approval, but there continue to be concerns about safely using high-dose viral therapies in humans, including immune responses and adverse effects such as genotoxicity, hepatotoxicity, thrombotic microangiopathy, and neurotoxicity. In this review, we explore AAV biology with an emphasis on current vector engineering strategies and manufacturing technologies. We discuss how rAAVs are being employed in ongoing clinical trials for ocular, neurological, metabolic, hematological, neuromuscular, and cardiovascular diseases as well as cancers. We outline immune responses triggered by rAAV, address associated side effects, and discuss strategies to mitigate these reactions. We hope that discussing recent advancements and current challenges in the field will be a helpful guide for researchers and clinicians navigating the ever-evolving landscape of rAAV-based gene therapy.

CPEB3 suppresses gastric cancer progression by inhibiting ADAR1-mediated RNA editing via localizing ADAR1 mRNA to P bodies

Deciphering the crosstalk between RNA-binding proteins and corresponding RNAs will provide a better understanding of gastric cancer (GC) progression. The comprehensive bioinformatics study identified cytoplasmic polyadenylation element-binding protein 3 (CPEB3) might play a vital role in GC progression. Then we found CPEB3 was downregulated in GC and correlated with prognosis. In addition, CPEB3 suppressed GC cell proliferation, invasion and migration in vitro, as well as tumor growth and metastasis in vivo. Mechanistic study demonstrated CPEB3 interacted with 3'-UTR of ADAR1 mRNA through binding to CPEC nucleotide element, and then inhibited its translation by localizing it to processing bodies (P bodies), eventually leading to the suppression of ADAR1-mediated RNA editing. Microscale thermophoresis assay further revealed that the direct interaction between CPEB3 and GW182, the P-body's major component, was through the 440-698AA region of CPEB3 binding to the 403-860AA region of GW182. Finally, AAV9-CPEB3 was developed and administrated in mouse models to assess its potential value in gene therapy. We found AAV9-CPEB3 inhibited GC growth and metastasis. Besides, AAV9-CPEB3 induced hydropic degeneration in mouse liver, but did not cause kidney damage. These findings concluded that CPEB3 suppresses GC progression by inhibiting ADAR1-mediated RNA editing via localizing ADAR1 mRNA to P bodies.

rAAV-based and intraprostatically delivered miR-34a therapeutics for efficient inhibition of prostate cancer progression

At present, there is no effective treatment for prostate cancer (PCa). Previous studies have reported that miR-34a is significantly downregulated in PCa cells; therefore, modulation of miR-34a expression might be a promising therapeutic approach for PCa treatment. To this end, we first verified the downregulation of miR-34a in prostate tumors from a transgenic adenocarcinoma mouse prostate (TRAMP) model. We found that miR-34a overexpression significantly inhibited the cell cycle, viability, and migration of PCa cells by targeting its downstream genes. Next, we tested the concept of intraprostatic injection of rAAV9·pri-miR-34a into 8-week-old TRAMP mice to inhibit PCa progression. We observed that the treatment lowered body weights significantly compared to the control treatment starting at 30 weeks after injection. rAAV9·pri-miR-34a treatment also obviously extended the lifespan of TRAMP mice. Moreover, we confirmed that the neoplasia in the treated prostates was significantly diminished compared to that in the control group. In addition, overexpressed miR-34a downregulated the expression of its target genes. Taken together, our results demonstrated, for the first time, the potential of rAAV-mediated efficient modulation of miR-34a expression in the prostate to inhibit PCa progression by regulating its downstream gene expression.

rAAV-delivered PTEN therapeutics for prostate cancer

Effective treatments for prostate cancer (PCa) require further development, and previous studies have reported that PTEN and its downstream target CDKN1B are significantly downregulated in PCa cells compared with normal cells. Therefore, modulation of PTEN and CDKN1B expression might be a promising therapeutic approach for PCa treatment. Expression of PTEN and CDKN1B was verified in specimens from PCa patients and transgenic adenocarcinoma mouse prostate (TRAMP) mice. The effect of PTEN on PCa cell migration, apoptosis, and the cell cycle was analyzed in vitro using a wound-healing assay and flow cytometry. We assessed the ability of intraprostatic and intratumoral injections of recombinant adeno-associated virus (rAAV) 9 expressing Pten or Cdkn1b into TRAMP mice and a subcutaneous tumor xenograft mouse model, respectively, to inhibit PCa progression. PTEN and CDKN1B were significantly downregulated in human and mouse PCa samples, and CDKN1B expression correlated positively with PTEN expression. PTEN overexpression significantly inhibited cell migration and cell-cycle progression and promoted apoptosis in PCa cells by decreasing Ccnd1 expression and increasing that of Cdkn1b. Importantly, treatment with the rAAV9.Pten or rAAV9.Cdkn1b extended the lifespan of TRAMP mice and inhibited the growth rate of tumor xenografts by regulating downstream gene expression. Moreover, neoplasia in treated prostates was significantly diminished compared with that in control prostates, and apoptosis was markedly observed in xenografts treated with Pten or Cdkn1b. These data indicate that rAAV-based PTEN/CDKN1B delivery is promising for the development of novel therapeutics for PCa.

Vinculin orchestrates prostate cancer progression by regulating tumor cell invasion, migration, and proliferation

BACKGROUND

Prostate cancer (PCa) is a leading cause of death in men, and effective treatment of PCa requires further development. Our study aimed to investigate the potential role of vinculin (VCL) in PCa progression in vitro and in vivo.

METHODS

We investigated the methylation level of the VCL promoter based on the TCGA database. The knockdown efficacy of VCL gene expression was confirmed by quantitative polymerase chain reaction, Western blot analysis, and immunofluorescence. Furthermore, morphological changes in PCa cells were detected using phalloidin staining. The mobility of PCa cells was measured using transwell assays and high-content analysis. Moreover, cell growth and viability were determined using the colony formation and cell counting kit-8 assays. The role of VCL in tumor growth in vivo was investigated using a subcutaneous xenograft model generated by injecting tumor cells into the right flank of BALB/c nude mice.

RESULTS

The methylation level of the VCL promoter in PCa was significantly downregulated concomitant with age and the progression of nodal metastasis. VCL expression was markedly decreased by shRNA. Importantly, VCL knockdown significantly changed the cell morphology; inhibited the migration, invasion, and movement; and repressed colony formation and viability of PCa cells in vitro. Furthermore, downregulation of VCL suppressed tumor growth in vivo.

CONCLUSIONS

Our study comprehensively evaluated the role of VCL in PCa progression in vivo and in vitro. The findings of the present study suggest that VCL can be a potential target for PCa prognosis and treatment.

Disruption by SaCas9 Endonuclease of HERV-Kenv, a Retroviral Gene with Oncogenic and Neuropathogenic Potential, Inhibits Molecules Involved in Cancer and Amyotrophic Lateral Sclerosis

The human endogenous retrovirus (HERV)-K, human mouse mammary tumor virus like-2 (HML-2) subgroup of HERVs is activated in several tumors and has been related to prostate cancer progression and motor neuron diseases. The cellular splicing factor 2/alternative splicing factor (SF2/ASF) is a positive regulator of gene expression, coded by a potent proto-oncogene, amplified, and abnormally expressed in tumors. TAR DNA-binding protein-43 (TDP-43) is a DNA/RNA-binding protein, negative regulator of alternative splicing, known for causing neurodegeneration, and with complex roles in oncogenesis. We used the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology, with the Cas9 system from Staphylococcus aureus (SaCas9), to disrupt the HERV-K(HML-2)env gene, and evaluated the effects on cultured cells. The tool was tested on human prostate cancer LNCaP cells, whose HERV-Kenv transcription profile is known. It caused HERV-K(HML-2)env disruption (the first reported of a HERV gene), as evaluated by DNA sequencing, and inhibition of env transcripts and proteins. The HERV-K(HML-2)env disruption was found to interfere with important regulators of cell expression and proliferation, involved in manaling, RNA-binding, and alternative splicing, such as epidermal growth factor receptor (EGF-R), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), SF2/ASF, and TDP-43. These novel findings suggest that HERV-K is not an innocent bystander, they reinforce its links to oncogenesis and motor neuron diseases, and they open potential innovative therapeutic options.

Adeno-associated virus (AAV) vectors in cancer gene therapy

Gene delivery vectors based on adeno-associated virus (AAV) have been utilized in a large number of gene therapy clinical trials, which have demonstrated their strong safety profile and increasingly their therapeutic efficacy for treating monogenic diseases. For cancer applications, AAV vectors have been harnessed for delivery of an extensive repertoire of transgenes to preclinical models and, more recently, clinical trials involving certain cancers. This review describes the applications of AAV vectors to cancer models and presents developments in vector engineering and payload design aimed at tailoring AAV vectors for transduction and treatment of cancer cells. We also discuss the current status of AAV clinical development in oncology and future directions for AAV in this field.

Maspin enhances cisplatin chemosensitivity in bladder cancer T24 and 5637 cells and correlates with prognosis of muscle-invasive bladder cancer patients receiving cisplatin based neoadjuvant chemotherapy

Background

Maspin, a non-inhibitory member of the serine protease inhibitor superfamily, has been characterized as a tumor suppressor gene in multiple cancer types. Chemotherapeutic insensitivity is one of major obstacles to effectively treating muscle invasive bladder cancer (MIBC). This study was conducted to investigate the role and probable mechanism of Maspin enhancing cisplatin chemosensitivity of bladder cancer in vitro and MIBC patients.

Methods

Maspin expression was quantified by qRT-PCR in two MIBC cell lines (T24 and 5637). After successful established Maspin overexpression model by lipidosome transfection, MTT and cell apoptosis assay were used to assess the MIBC’s cisplatin sensitivity. Western blot method was used to test PI3K/ AKT/mTOR signal passway and apoptosis related molecules Caspase3 and Bcl-2. Additionally, we evaluated Maspin expression and prognosis in 62 MIBC cases who underwent cisplatin based neoadjuvant chemotherapy (NACT) using immunohistochemistry.

Result

Upregulate Maspin expression could enhance the chemosensitivity induced by cisplatin in T24 and 5637 cell lines. The cell viability, cloning ability and IC50 were reduced while apoptosis rate was upregulated when cells were transfected Maspin. Phospho(p)-AKT, PI3K, mTOR, and Bcl-2 expression were significantly decreased, whereas Caspase3 was greatly increased in the Maspin group. In the clinic study, there was significant correlation between Maspin expression and overall survival (OS) and progression-free survival (PFS) rate in MIBC patients who received cisplatin based NACT.

Conclusion

Maspin could enhance cisplatin chemosensitivity in T24 and 5637 cell lines. Its expression correlated with prognosis of MIBC patients who received cisplatin based neoadjuvant chemotherapy.

A novel gene expression system strongly enhances the anticancer effects of a REIC/Dkk-3-encoding adenoviral vector

Gene expression systems with various promoters, including the cytomegalovirus (CMV) promoter, have been developed to increase the gene expression in a variety of normal and cancer cells. In particular, in the clinical trials of cancer gene therapy, a more efficient and robust gene expression system is required to achieve sufficient therapeutic outcomes. By inserting the triple translational enhancer sequences of human telomerase reverse transcriptase (hTERT), Simian virus 40 (SV40) and CMV downstream of the sequence of the BGH polyA, we were able to develop a novel gene expression system that significantly enhances the expression of the genes of interest. We termed this novel gene expression cassette the super gene expression (SGE) system, and herein verify the utility of the SGE cassette for a replication-deficient adenoviral vector. We newly developed an adenoviral vector expressing the tumor suppressor, reduced expression in immortalized cells (REIC)/Dickkopf-3 (Dkk-3), based on the CMV promoter-driven SGE system (Ad-SGE-REIC) and compared the therapeutic utility of Ad-SGE-REIC with that of the conventional adenoviral vectors (Ad-CMV-REIC or Ad-CAG-REIC). The results demonstrated that the CMV promoter-SGE system allows for more potent gene expression, and that the Ad-SGE-REIC is superior to conventional adenoviral systems in terms of the REIC protein expression and therapeutic effects. Since the SGE cassette can be applied for the expression of various therapeutic genes using various vector systems, we believe that this novel system will become an innovative tool in the field of gene expression and gene therapy.

Maspin: molecular mechanisms and therapeutic implications

Maspin, a non-inhibitory member of the serine protease inhibitor superfamily, has been characterized as a tumor suppressor gene in multiple cancer types. Among the established anti-tumor effects of Maspin are the inhibition of cancer cell invasion, attachment to extracellular matrices, increased sensitivity to apoptosis, and inhibition of angiogenesis. However, while significant experimental data support the role of Maspin as a tumor suppressor, clinical data regarding the prognostic implications of Maspin expression have led to conflicting results. This highlights the need for a better understanding of the context dependencies of Maspin in normal biology and how these are perturbed in the context of cancer. In this review, we outline the regulation and roles of Maspin in normal and developmental biology while discussing novel evidence and emerging theories related to its functions in cancer. We provide insight into the immense therapeutic potential of Maspin and the challenges related to its successful clinical translation.

Targeted expression of Escherichia coli purine nucleoside phosphorylase and Fludara® for prostate cancer therapy

BACKGROUND

Previous studies have shown that Herpes Simplex Virus thymidine kinase (HSV-tk)/ganciclovir (GCV) comprised the most commonly used suicide gene therapy for prostate cancer, with modest results being obtained. However, novel suicide genes, such as Escherichia coli purine nucleoside phosphorylase (PNP), have been utilized to demonstrate more potent tumor killing and an enhanced bystander effect on local, non-expressing cells compared to HSV-tk.

METHODS

PNP/fludarabine (Fludara®; fludarabine phosphate; Berlex Labs, Richmond, CA, USA) was deliveried by prostate-specific, rat probasin-based promoter, ARR2PB. After infection of various cell lines with ADV.ARR(2) PB-PNP and administration of androgen analog, R1881, expression of PNP mRNA was detected; in vivo, the antitumor effect of the ARR(2) PB-PNP/Fludara system was monitored and analyzed, as well as animal survival.

RESULTS

After in vitro infection with ADV.ARR(2) PB-PNP (multiplicity of infection  =  10), LNCaP cells were more sensitive to a lower concentration Fludara (LD(50) , approximately 0.1 µg/ml) in the presence of R1881. Furthermore, robust bystander effects after R1881/Fludara treatment were observed in LNCaP cells after infection with bicistronic vector ADV.ARR2PB/PNP-IRES-EGFP in contrast to a much weaker effect in cells treated with ADV.CMV-HSV-tk/GCV. In vivo, tumor size in the ADV.ARR2PB-PNP/Fludara treatment group was dramatically smaller than in the control groups, and the mice treated with our system had a significantly prolonged survival, with three of eight mice surviving up to the 160-day termination point, as well as no systemic toxicity.

CONCLUSIONS

The ARR(2) PB-PNP/Fludara system induced massive tumor cell death and a prolonged life span without systemic cytotoxicity; therefore, it might be a more attractive strategy for suicide gene therapy of prostate cancer.

Role of maspin in cancer

Maspin (mammary serine protease inhibitor), is a member of the serine protease inhibitor/non-inhibitor superfamily. Its expression is down-regulated in breast, prostate, gastric and melanoma cancers but over-expressed in pancreatic, gallbladder, colorectal, and thyroid cancers suggesting that maspin may play different activities in different cell types. However, maspin expression seems to be correlated with better prognosis in prostate, bladder, lung, gastric, colorectal, head and neck, thyroid and melanoma cancer. In breast and ovarian cancer maspin significance is associated with its subcellular localization: nucleus maspin expression correlates with a good prognosis, whilst in pancreatic cancer it predicts a poor prognosis. Since tumor metastasis requires the detachment and invasion of tumor cells through the basement membrane and stroma, a selectively increased adhesion by the presence of maspin may contribute to the inhibition of tumor metastasis. Furthermore the different position of maspin inside the cell or its epigenetic modifications may explain the different behavior of the expression of maspin between tumors. The expression of maspin might be useful as a prognostic and possibly predictive factor for patients with particular types of cancer and data can guide physicians in selecting therapy. Its expression in circulating tumor cells especially in breast cancer, could be also useful in clinical practice along with other factors, such as age, comorbidities, blood examinations in order to select the best therapy to be carried out. Focusing on the malignancies in which maspin showed a positive prognostic value, therapeutic approaches studied so far aimed to re-activate a dormant tumor suppressor gene by designed transcription factors, to hit the system that inhibits the expression of maspin, to identify natural substances that can determine the activation and the expression of maspin or possible “molecules binds” to introduce maspin in cancer cell and gene therapy capable of up-regulating the maspin in an attempt to reduce primarily the risk of metastasis.

Further studies in these directions are necessary to better define the therapeutic implication of maspin.

Growth differentiation factor-15 upregulates interleukin-6 to promote tumorigenesis of prostate carcinoma PC-3 cells

Growth differentiation factor-15 (GDF15), a member of the transforming growth factor-β superfamily, is associated with human cancer progress. We evaluated the role GDF15 plays in tumorigenesis of prostate carcinoma PC-3 cells. Results from real-time RT-PCR and ELISA revealed that expression of GDF15 was approximately threefold higher in LNCaP cells than in PC-3 cells. Other prostate cell lines (PZ-HPV-7, CA-HPV-10, and DU145 cells) expressed extremely low levels of GDF15. Stable overexpression of GDF15 in PC-3 cells enhanced the degree of cell proliferation and invasion as shown in the (3)H-thymidine incorporation assay and in the Matrigel invasion assay respectively. Soft agar assays and xenograft animal studies indicated that overexpression of GDF15 in PC-3 cells increased tumorigenesis in vitro and in vivo. Results from RT-PCR, immunoblot, and reporter assays revealed that overexpression of GDF15 resulted in decreased expression of maspin and upregulation of interleukin-6 (IL6), matriptase, and N-myc downstream-regulated gene 1 (NDRG1) expression. Further studies revealed that overexpression of IL6 enhanced GDF15 expression in LNCaP cells while knockdown of IL6 blocked the expression of GDF15 in PC-3 cells, suggesting that expression of GDF15 is upregulated by IL6. This study demonstrated that expression of GDF15 induces cell proliferation, invasion, and tumorigenesis of prostate carcinoma PC-3 cells. The enhancement of tumorigenesis and invasiveness of prostate carcinoma cells that stably overexpress GDF15 may be caused by the dysregulation of maspin, matriptase, and IL6 gene expression. The expression of GDF15 and IL6 is controlled via a positive feedback loop in PC-3 cells.

Glycoprotein transmembrane nmb: an androgen-downregulated gene attenuates cell invasion and tumorigenesis in prostate carcinoma cells

BACKGROUND

Glycoprotein transmembrane nmb (GPNMB) gene was originally identified in osteoblasts and belongs to the pmel-17/nmb family. The function or regulation of GPNMB in the human prostate remains unknown.

METHODS

The expression of GPNMB in prostate carcinoma cells were determined by real-time reverse transcription-polymerase chain reaction (RT-qPCR) and immunoblot assays. Effects of ectopic GPNMB overexpression on cell proliferation, invasion, and tumorigenesis were determined by (3) H-thymidine incorporation, matrigel invasion, soft agar cloning assays, and murine xenograft study. Effects of GPNMB, p53, and androgen on target gene were assessed using RT-PCR, immunoblotting, and transient gene expression assays.

RESULTS

In vitro analysis using several prostate cell lines suggested that expression of GPNMB may be relevant to the extent of neoplasia. Ectopic overexpression of GPNMB significantly attenuated cell proliferation and invasion and exerted antitumorigenic activity on PC-3 cells in vitro and in vivo. GPNMB overexpression induced the gene expressions of N-myc downstream regulated gene 1 (Ndrg1) and maspin in PC-3 cells. Doxorubicin treatment or transient overexpression of p53 increased GPNMB expression. Androgen (R1881) treatment has a divergent effect on gene expression of prostate-specific antigen (PSA) and GPNMB in LNCaP cells. Androgen treatment enhanced cell proliferation but downregulated GPNMB protein expression in stably overexpressed androgen receptor (AR) CA-HPV-10 cells.

CONCLUSIONS

Together these results suggest that GPNMB gene is a p53- and androgen-dysregulated gene and should be regarded as an anti-tumor gene for prostate cancer. The enhancement of Ndrg1 and maspin gene expressions may account for the anti-proliferative and anti-invasive function of GPNMB in PC-3 cells.

Epigenetic reprogramming of cancer cells via targeted DNA methylation

An obstacle in the treatment of human diseases such as cancer is the inability to selectively and effectively target historically undruggable targets such as transcription factors. Here, we employ a novel technology using artificial transcription factors (ATFs) to epigenetically target gene expression in cancer cells. We show that site-specific DNA methylation and long-term stable repression of the tumor suppressor Maspin and the oncogene SOX2 can be achieved in breast cancer cells via zinc-finger ATFs targeting DNA methyltransferase 3a (DNMT3a) to the promoters of these genes. Using this approach, we show Maspin and SOX2 downregulation is more significant as compared with transient knockdown, which is also accompanied by stable phenotypic reprogramming of the cancer cell. These findings indicate that multimodular Zinc Finger Proteins linked to epigenetic editing domains can be used as novel cell resources to selectively and heritably alter gene expression patterns to stably reprogram cell fate.

Reactivation of MASPIN in non-small cell lung carcinoma (NSCLC) cells by artificial transcription factors (ATFs)

Tumor suppressor genes have antiproliferative and antimetastatic functions, and thus, they negatively affect tumor progression. Reactivating specific tumor suppressor genes would offer an important therapeutic strategy to block tumor progression. Mammary Serine Protease Inhibitor (MASPIN) is a tumor suppressor gene that is not mutated or rearranged in tumor cells, but is silenced during metastatic progression by transcriptional and epigenetic mechanisms. In this work, we have investigated the ability of Artificial Transcription Factors (ATFs) to reactivate MASPIN expression and to reduce tumor growth and metastatic dissemination in Non-Small Cell Lung Carcinoma (NSCLC) cell lines carrying a hypermethylated MASPIN promoter. We found that the ATFs linked to transactivator domains were able to demethylate the MASPIN promoter. Consistently, we observed that co-treatment of ATF-transduced cells with methyltransferase inhibitors enhanced MASPIN expression as well as induction of tumor cell apoptosis. In addition to tumor suppressive functions, restoration of endogenous MASPIN expression was accompanied by inhibition of metastatic dissemination in nude mice. ATF-mediated reactivation of MASPIN lead to changes in cell motility and to induction of E-CADHERIN. These data suggest that ATFs are able to reprogram aggressive lung tumor cells towards a more epithelial, differentiated phenotype, and thus, represent novel therapeutic agents for metastatic lung cancers.

Gene therapy of benign gynecological diseases

Gene therapy is the introduction of genetic material into patient's cells to achieve therapeutic benefit. Advances in molecular biology techniques and better understanding of disease pathogenesis have validated the use of a variety of genes as potential molecular targets for gene therapy based approaches. Gene therapy strategies include: mutation compensation of dysregulated genes; replacement of defective tumor-suppressor genes; inactivation of oncogenes; introduction of suicide genes; immunogenic therapy and antiangiogenesis based approaches. Preclinical studies of gene therapy for various gynecological disorders have not only shown to be feasible, but also showed promising results in diseases such as uterine leiomyomas and endometriosis. In recent years, significant improvement in gene transfer technology has led to the development of targetable vectors, which have fewer side-effects without compromising their efficacy. This review provides an update on developing gene therapy approaches to treat common gynecological diseases such as uterine leiomyoma and endometriosis.

Application of a haematopoetic progenitor cell-targeted adeno-associated viral (AAV) vector established by selection of an AAV random peptide library on a leukaemia cell line

BACKGROUND

For many promising target cells (e.g.: haematopoeitic progenitors), the susceptibility to standard adeno-associated viral (AAV) vectors is low. Advancements in vector development now allows the generation of target cell-selected AAV capsid mutants.

METHODS

To determine its suitability, the method was applied on a chronic myelogenous leukaemia (CML) cell line (K562) to obtain a CML-targeted vector and the resulting vectors tested on leukaemia, non-leukaemia, primary human CML and CD34+ peripheral blood progenitor cells (PBPC); standard AAV2 and a random capsid mutant vector served as controls.

RESULTS

Transduction of CML (BV173, EM3, K562 and Lama84) and AML (HL60 and KG1a) cell lines with the capsid mutants resulted in an up to 36-fold increase in CML transduction efficiency (K562: 2-fold, 60% +/- 2% green fluorescent protein (GFP)+ cells; BV173: 9-fold, 37% +/- 2% GFP+ cells; Lama84: 36-fold, 29% +/- 2% GFP+ cells) compared to controls. For AML (KG1a, HL60) and one CML cell line (EM3), no significant transduction (<1% GFP+ cells) was observed for any vector. Although the capsid mutant clone was established on a cell line, proof-of-principle experiments using primary human cells were performed. For CML (3.2-fold, mutant: 1.75% +/- 0.45% GFP+ cells, p = 0.03) and PBPC (3.5-fold, mutant: 4.21% +/- 3.40% GFP+ cells) a moderate increase in gene transfer of the capsid mutant compared to control vectors was observed.

CONCLUSION

Using an AAV random peptide library on a CML cell line, we were able to generate a capsid mutant, which transduced CML cell lines and primary human haematopoietic progenitor cells with higher efficiency than standard recombinant AAV vectors.

REIC/Dkk-3 overexpression downregulates P-glycoprotein in multidrug-resistant MCF7/ADR cells and induces apoptosis in breast cancer

The overexpression of reduced expression in immortalized cells (REIC)/Dickkopf-3 (Dkk-3), a tumor suppressor gene, induced apoptosis in human prostatic and testicular cancer cells. The aim of this study is to examine the potential of REIC/Dkk-3 as a therapeutic target against breast cancer. First, the in vitro apoptotic effect of Ad-REIC treatment was investigated in breast cancer cell lines and the adenovirus-mediated overexpression of REIC/Dkk-3 was thus found to lead to apoptotic cell death in a c-Jun-NH(2)-kinase (JNK) phosphorylaion-dependent manner. Moreover, an in vivo apoptotic effect and MCF/Wt tumor growth inhibition were observed in the mouse model after intratumoral Ad-REIC injection. As multidrug resistance (MDR) is a major problem in the chemotherapy of progressive breast cancer, the in vitro effects of Ad-REIC treatment were investigated in terms of the sensitivity of multidrug-resistant MCF7/ADR cells to doxorubicin and of the P-glycoprotein expression. Ad-REIC treatment in MCF7/ADR cells also downregulated P-glycoprotein expresssion through JNK activation, and sensitized its drug resistance against doxorubicin. Therefore, not only apoptosis induction but also the reversal of anticancer drug resistance was achieved using Ad-REIC. We suggest that REIC/Dkk-3 is a novel target for breast cancer treatment and that Ad-REIC might be an attractive agent against drug-resistant cancer in combination with conventional antineoplastic agents.

Turning the gene tap off; implications of regulating gene expression for cancer therapeutics

Cancer poses a tremendous therapeutic challenge worldwide, highlighting the critical need for developing novel therapeutics. A promising cancer treatment modality is gene therapy, which is a form of molecular medicine designed to introduce into target cells genetic material with therapeutic intent. Anticancer gene therapy strategies currently used in preclinical models, and in some cases in the clinic, include proapoptotic genes, oncolytic/replicative vectors, conditional cytotoxic approaches, inhibition of angiogenesis, inhibition of growth factor signaling, inactivation of oncogenes, inhibition of tumor invasion and stimulation of the immune system. The translation of these novel therapeutic modalities from the preclinical setting to the clinic has been driven by encouraging preclinical efficacy data and advances in gene delivery technologies. One area of intense research involves the ability to accurately regulate the levels of therapeutic gene expression to achieve enhanced efficacy and provide the capability to switch gene expression off completely if adverse side effects should arise. This feature could also be implemented to switch gene expression off when a successful therapeutic outcome ensues. Here, we will review recent developments related to the engineering of transcriptional switches within gene delivery systems, which could be implemented in clinical gene therapy applications directed at the treatment of cancer.

Direct and distant antitumor effects of a telomerase-selective oncolytic adenoviral agent, OBP-301, in a mouse prostate cancer model

We previously constructed OBP-301 (Telomelysin, a telomerase-specific replication-competent adenovirus with human telomerase reverse transcriptase (hTERT) promoter), which showed a strong anticancer effect by inducing cell lysis of human non-small cell lung cancer and colorectal cancer cells. To investigate the utility of OBP-301 for prostate cancer treatment, we herein evaluate the cell killing and antitumor effects. First, in vitro hTERT-specific adenovirus transduction in human prostate cancer cells (LNCaP, PC3, DU145) was confirmed using OBP-401 (Telomelysin-green fluorescent protein (GFP)). There was no detectable GFP transduction in the human prostate normal cells (PrEC, PrSC). Consistently, the cell-killing effect of OBP-301 was observed only in the cancer cells. Second, using an in vivo subcutaneous LNCaP tumor model in nude mice, we demonstrated that three intratumoral OBP-301 injections (10(7) PFU per tumor x 3 days) were sufficient to eradicate the detectable LNCaP prostate tumor. We also demonstrated that the ispilateral treatment with OBP-301 significantly suppressed contralateral LNCaP tumor growth in both sides of the tumor model. Histological and immunohistochemical analyses revealed diffuse oncolytic degeneration and adenoviral E1A protein expression in both sides of the tumors. Therefore, in situ OBP-301 administration could be a promising therapeutic strategy against prostate cancer and its metastatic lesions.

The role of the adeno-associated virus capsid in gene transfer

Adeno-associated virus (AAV) is one of the most promising viral gene transfer vectors that has been shown to effect long-term gene expression and disease correction with low toxicity in animal models, and is well tolerated in human clinical trials. The surface of the AAV capsid is an essential component that is involved in cell binding, internalization, and trafficking within the targeted cell. Prior to developing a gene therapy strategy that utilizes AAV, the serotype should be carefully considered since each capsid exhibits a unique tissue tropism and transduction efficiency. Several approaches have been undertaken in an effort to target AAV vectors to specific cell types, including utilizing natural serotypes that target a desired cellular receptor, producing pseudotyped vectors, and engineering chimeric and mosaic AAV capsids. These capsid modifications are being incorporated into vector production and purification methods that provide for the ability to scale-up the manufacturing process to support human clinical trials. Protocols for small-scale and large-scale production of AAV, as well as assays to characterize the final vector product, are presented here. The structures of AAV2, AAV4, and AAV5 have been solved by X-ray crystallography or cryo-electron microscopy (cryo-EM), and provide a basis for rational vector design in developing customized capsids for specific targeting of AAV vectors. The capsid of AAV has been shown to be remarkably stable, which is a desirable characteristic for a gene therapy vector; however, recently it has been shown that the AAV serotypes exhibit differential susceptibility to proteases. The capsid fragmentation pattern when exposed to various proteases, as well as the susceptibility of the serotypes to a series of proteases, provides a unique fingerprint for each serotype that can be used for capsid identity validation. In addition to serotype identification, protease susceptibility can also be utilized to study dynamic structural changes that must occur for the AAV capsid to perform its various functions during the virus life cycle. The use of proteases for structural studies in solution complements the crystal structural studies of the virus. A generic protocol based on proteolysis for AAV serotype identification is provided here.

Therapeutic ultrasound facilitates antiangiogenic gene delivery and inhibits prostate tumor growth

Gene therapy clinical trials are limited due to several hurdles concerning the type of vector used, particularly, the viral vectors, and transfection efficacy when non-viral vectors are used. Therapeutic ultrasound is a promising non-viral technology that can be used in the clinical setting. Here, for the first time, we show the efficacy of therapeutic ultrasound to deliver genes encoding for hemopexin-like domain fragment (PEX), an inhibitor of angiogenesis, to prostate tumors in vivo. Moreover, the addition of an ultrasound contrast agent (Optison) to the transfection process was evaluated. Prostate cancer cells and endothelial cells (EC) were transfected in vitro with cDNA-PEX using therapeutic ultrasound alone (TUS + pPEX) or with Optison (TUS + pPEX + Optison). The biological activity of the expressed PEX was assessed using proliferation, migration, and apoptosis assays done on EC and prostate cancer cells. TUS + pPEX + Optison led to the inhibition of EC and prostate cancer cell proliferation (<65%), migration (<50%), and an increase in apoptosis. In vivo, C57/black mice were inoculated s.c. with prostate cancer cells. The tumors were treated with TUS + pPEX and TUS + pPEX + Optison either once or repeatedly. Tumor growth was evaluated, after which histology and immunohistochemistry analyses were done. A single treatment of TUS + pPEX led to a 35% inhibition in tumor growth. Using TUS + PEX + Optison led to an inhibition of 50%. Repeated treatments of TUS + pPEX + Optison were found to significantly (P < 0.001) inhibit prostate tumor growth by 80%, along with the angiogenic indices, with no toxicity to the surrounding tissues. These results depict the efficacy of therapeutic ultrasound as a non-viral technology to efficiently deliver genes to tumors in general, and to deliver angiogenic inhibitors to prostate cancer in particular.

Adenovirus-mediated REIC/Dkk-3 gene transfer inhibits tumor growth and metastasis in an orthotopic prostate cancer model

We had previously reported that REIC/Dkk-3, a member of the Dickkopf (Dkk) gene family, works as a tumor suppressor. In this study, we evaluated the therapeutic effects of an intratumoral injection with adenoviral vector encoding REIC/Dkk-3 gene (Ad-REIC) using an orthotopic mouse prostate cancer model of RM-9 cells. We also investigated the in vivo anti-metastatic effect and in vitro anti-invasion effect of Ad-REIC gene delivery. We demonstrated that the Ad-REIC treatment inhibited prostate cancer growth and lymph node metastasis, and prolonged mice survival in the model. These therapeutic responses were consistent with the intratumoral apoptosis induction and in vitro suppression of cell invasion/migration with reduced matrix metalloprotease-2 activity. We thus concluded that in situ Ad-REIC/Dkk-3 gene transfer may be a promising therapeutic intervention modality for the treatment of prostate cancer.

Systemic cancer gene therapy using adeno-associated virus type 1 vector expressing MDA-7/IL24

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL24), selectively induces apoptosis in cancer cells without harming normal cells. It also exerts immunomodulatory and antiangiogenic effects, as well as potent antitumor bystander effects, making it an ideal candidate for a new anticancer gene therapy. Here, we examined the feasibility of adeno-associated virus type 1 (AAV1) vector-mediated systemic gene therapy using mda-7/IL24. In vitro studies showed that medium conditioned by AAV1-mda7-transducedC2C12 cells induces tumor cell-specific apoptosis and inhibits angiogenesis in a human umbilical vein endothelial cell tube formation assay. To assess the in vivo effects of AAV1-mediated systemic delivery of MDA-7/IL24, we generated a subcutaneous tumor model by injecting Ehrlich ascites tumor cells into the dorsum of DDY mice. A single intravenous injection of AAV1-mda7 (2.0 x 10(11) viral genomes) significantly inhibited tumor growth. In addition, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), and immunohistochemical analyses showed significant induction of tumor-cell-specific apoptosis and reduction of microvessel formation within the tumors, and there was a significant increase in survival among the AAV1-mda7-treated mice. These results clearly demonstrate that continuous systemic delivery of MDA-7/IL24 can serve as an effective treatment for cancer. Thus, AAV1 vector-mediated systemic delivery of MDA-7/IL24 represents a potentially important new approach to anticancer therapy.

Mitochondrial membrane permeabilization in cell death

Irrespective of the morphological features of end-stage cell death (that may be apoptotic, necrotic, autophagic, or mitotic), mitochondrial membrane permeabilization (MMP) is frequently the decisive event that delimits the frontier between survival and death. Thus mitochondrial membranes constitute the battleground on which opposing signals combat to seal the cell's fate. Local players that determine the propensity to MMP include the pro- and antiapoptotic members of the Bcl-2 family, proteins from the mitochondrialpermeability transition pore complex, as well as a plethora of interacting partners including mitochondrial lipids. Intermediate metabolites, redox processes, sphingolipids, ion gradients, transcription factors, as well as kinases and phosphatases link lethal and vital signals emanating from distinct subcellular compartments to mitochondria. Thus mitochondria integrate a variety of proapoptotic signals. Once MMP has been induced, it causes the release of catabolic hydrolases and activators of such enzymes (including those of caspases) from mitochondria. These catabolic enzymes as well as the cessation of the bioenergetic and redox functions of mitochondria finally lead to cell death, meaning that mitochondria coordinate the late stage of cellular demise. Pathological cell death induced by ischemia/reperfusion, intoxication with xenobiotics, neurodegenerative diseases, or viral infection also relies on MMP as a critical event. The inhibition of MMP constitutes an important strategy for the pharmaceutical prevention of unwarranted cell death. Conversely, induction of MMP in tumor cells constitutes the goal of anticancer chemotherapy.

High WT1 expression is associated with very poor survival of patients with osteogenic sarcoma metastasis

PURPOSE

Although metastasis is the primary determinant of poor survival of patients with osteogenic sarcoma, some patients live much longer than others, indicating metastatic heterogeneity underlying survival outcome. The purpose of the investigation was to identify genes underlying survival outcome of patients with osteogenic sarcoma metastasis.

EXPERIMENTAL DESIGN

We have used microarray to first compare mRNA expression between normal bone and osteogenic sarcoma specimens, identified genes overexpressed in osteogenic sarcoma, and compared expression of the selected gene between a poorly metastatic (SAOS) and two highly metastatic cell lines (LM8 and 143B). Finally, expression of the selected gene was assessed by immunostaining of osteogenic sarcoma samples with known survival outcome.

RESULTS

Microarray analysis revealed 5.3-fold more expression of WT1 mRNA in osteogenic sarcoma compared with normal bone and >2-fold overexpression in 143B and LM8 cells compared with SAOS. Furthermore, WT1 mRNA was absent in normal bone (10 of 10) by reverse transcription-PCR but present in osteogenic sarcoma-derived cell lines (5 of 8). One hundred percent (42 of 42) of low-grade osteogenic sarcoma specimens expressed no WT1 as determined by immunostaining; however, 24% (12 of 49) of the high-grade specimens showed intense staining. Mean survival of patients with high-grade metastatic osteogenic sarcoma but low WT1 staining (27 of 37) was 96.5 +/- 129.3 months, whereas mean survival of patients with high-grade metastatic osteogenic sarcoma having intense staining (10 of 37) was 18.3 +/- 12.3 months (P > 0.0143). All splice variants of WT1 mRNA, including a hitherto unknown variant (lacking exons 4 and 5), were found to be expressed in osteogenic sarcoma.

CONCLUSION

WT1 seems to be associated with very poor survival of patients with osteogenic sarcoma metastasis.

Anti-angiogenic gene therapy of cancer: current status and future prospects

The discovery of endogenous inhibitors of angiogenesis has made it possible to test the hypothesis that blocking the angiogenic switch may keep tumor growth in check, and has added a new investigational arm to the field of cancer gene therapy. Angiogenesis inhibitors are heterogeneous in origin and potency, and their growing list includes proteolysis products of larger molecules with a different function, such as angiostatin, endostatin and vasostatin, modulators of vascular endothelial growth factor activity, such as sFLT-1, and some cytokines/chemokines with marked anti-endothelial activity, such as IL-12, IFN-alpha, and CXCL10. Pre-clinical studies have clearly indicated that these factors are essentially cytostatic and that they need long-term administration in order to obtain prolonged anti-tumor effects, representing a rational basis for their delivery by a gene therapy approach. The experimental approaches attempted to date, reviewed herein, indicate overall that anti-angiogenic gene therapy has efficacy mainly as an early intervention strategy and that a better understanding of the biological mechanisms underlying resistance to angiogenesis inhibition, as well as appropriate combined treatments, are required to generate a conceptual advancement which could drive the field towards successful management of established tumors.

Cancer gene therapy targeting angiogenesis: An updated Review

Since the relationship between angiogenesis and tumor growth was established by Folkman in 1971, scientists have made efforts exploring the possibilities in treating cancer by targeting angiogenesis. Inhibition of angiogenesis growth factors and administration of angiogenesis inhibitors are the basics of anti-angiogenesis therapy. Transfer of anti-angiogenesis genes has received attention recently not only because of the advancement of recombinant vectors, but also because of the localized and sustained expression of therapeutic gene product inside the tumor after gene transfer. This review provides the up-to-date information about the strategies and the vectors studied in the field of anti-angiogenesis cancer gene therapy.

Re-activation of a dormant tumor suppressor gene maspin by designed transcription factors

The controlled and specific re-activation of endogenous tumor suppressors in cancer cells represents an important therapeutic strategy to block tumor growth and subsequent progression. Other than ectopic delivery of tumor suppressor-encoded cDNA, there are no therapeutic tools able to specifically re-activate tumor suppressor genes that are silenced in tumor cells. Herein, we describe a novel approach to specifically regulate dormant tumor suppressors in aggressive cancer cells. We have targeted the Mammary Serine Protease Inhibitor (maspin) (SERPINB5) tumor suppressor, which is silenced by transcriptional and aberrant promoter methylation in aggressive epithelial tumors. Maspin is a multifaceted protein, regulating tumor cell homeostasis through inhibition of cell growth, motility and invasion. We have constructed artificial transcription factors (ATFs) made of six zinc-finger (ZF) domains targeted against 18-base pair (bp) unique sequences in the maspin promoter. The ZFs were linked to the activator domain VP64 and delivered in breast tumor cells. We found that the designed ATFs specifically interact with their cognate targets in vitro with high affinity and selectivity. One ATF was able to re-activate maspin in cell lines that comprise a maspin promoter silenced by epigenetic mechanisms. Consistently, we found that this ATF was a powerful inducer of apoptosis and was able to knock down tumor cell invasion in vitro. Moreover, this ATF was able to suppress MDA-MB-231 growth in a xenograft breast cancer model in nude mice. Our work suggests that ATFs could be used in cancer therapeutics as novel molecular switches to re-activate dormant tumor suppressors.

Targeting maspin in endothelial cells to induce cell apoptosis

The diseases of cancer remain as some of the leading causes of death in the industrialised world, although there are a multitude of technologies being used in the field of medical oncology to combat these diseases and scientific research continues to make discoveries to improve patient outcomes. Some of this research has focused on the maspin gene and protein. Maspin is predicted to be a unique serpin with tumour suppressor activity. Recent studies have explored the use of maspin as a therapeutic agent against cancer. In one study, maspin was found to inhibit cancer growth and metastasis in a breast cancer mouse model through a maspin DNA-liposome therapy. A separate study showed the ability of maspin to induce apoptosis in tumour-specific endothelial cells. Taken together, these studies demonstrate the potential use of maspin as a viable anticancer therapeutic agent.

Treatment of human disease by adeno-associated viral gene transfer

During the past decade, in vivo administration of viral gene transfer vectors for treatment of numerous human diseases has been brought from bench to bedside in the form of clinical trials, mostly aimed at establishing the safety of the protocol. In preclinical studies in animal models of human disease, adeno-associated viral (AAV) vectors have emerged as a favored gene transfer system for this approach. These vectors are derived from a replication-deficient, non-pathogenic parvovirus with a single-stranded DNA genome. Efficient gene transfer to numerous target cells and tissues has been described. AAV is particularly efficient in transduction of non-dividing cells, and the vector genome persists predominantly in episomal forms. Substantial correction, and in some instances complete cure, of genetic disease has been obtained in animal models of hemophilia, lysosomal storage disorders, retinal diseases, disorders of the central nervous system, and other diseases. Therapeutic expression often lasted for months to years. Treatments of genetic disorders, cancer, and other acquired diseases are summarized in this review. Vector development, results in animals, early clinical experience, as well as potential hurdles and challenges are discussed.

Gene therapy and uterine leiomyoma: a review

Leiomyomas (fibroids) are common estrogen-dependent uterine tumours that cause significant morbidity for women and a substantial economic impact on health delivery systems. Currently, there is no effective medical treatment option for this condition-hysterectomy is the mainstay of management. This is not an attractive choice for many women, especially patients desiring to preserve their fertility potential. Gene therapy is becoming a clinical reality, with more than 600 clinical trials worldwide. Researchers have recently attempted to develop a gene-therapy-based approach for the ablation of uterine fibroids. The localized nature of this condition and its accessibility using different imaging or endoscopic techniques make it an attractive target for direct delivery of gene-based vectors. Recent work from our laboratory suggests the potential use of a dominant-negative form of estrogen receptor (ER) to inactivate estrogen signalling in leiomyoma cells and induce apoptosis. Our in vivo data in a mouse model demonstrate the ability of an adenovirus-expressing dominant-negative ER to arrest leiomyoma growth. We and others also have described the utility of the herpes simplex virus-thymidine kinase (HSV-TK) plus ganciclovir (GCV) suicide gene-therapy system to effectively eradicate leiomyoma cells by utilizing the bystandard effect phenomena and the high expression of gap-junction protein in these tumours. Further work on rat models will pave the way for future leiomyoma gene-therapy clinical trials and allow the realization of gene therapy as a viable non-surgical option for this common problem in women's health.