Targeting cancer by transcriptional control in cancer gene therapy and viral oncolysis

Protection of CHO cells by transfer of survivin driven by ovarian-specific promoter OSP-2

Chemotherapy is the major therapy for cancer in clinic. However, chemotherapeutic agents can harm the other tissues/organs besides cancer. Thus, there are great interests in protecting the innocents by the transfer of protective genes. There are two problems to be solved, one is the selection of protective genes and the other is the orientation of the exotic genes. Recent researches demonstrated that the principal mechanism of chemotherapeutics was through apoptosis. Hereby, introduction of anti-apoptosis genes might interrupt the processes of apoptosis to avoid side effect from chemotherapeutics. On the other hand, tissue-specific promoters, which control gene expression in a tissue-specific manner, might be an alternative tool to guarantee the location of target genes. In this research, we applied gene therapy to chemoprotection using anti-apoptosis gene survivin and ovarian-specific promoter OSP-2. The results showed that OSP-2 could specifically drive the expression of survivin in ovarian cells and survivin could protect cells via inhibiting apoptosis. This might put a light on the future of chemoprotective gene therapy.

Toxin-based therapeutic approaches

Protein toxins confer a defense against predation/grazing or a superior pathogenic competence upon the producing organism. Such toxins have been perfected through evolution in poisonous animals/plants and pathogenic bacteria. Over the past five decades, a lot of effort has been invested in studying their mechanism of action, the way they contribute to pathogenicity and in the development of antidotes that neutralize their action. In parallel, many research groups turned to explore the pharmaceutical potential of such toxins when they are used to efficiently impair essential cellular processes and/or damage the integrity of their target cells. The following review summarizes major advances in the field of toxin based therapeutics and offers a comprehensive description of the mode of action of each applied toxin.

Unity and diversity in the human adenoviruses: exploiting alternative entry pathways for gene therapy

Human Ads (adenoviruses) have been extensively utilized for the development of vectors for gene transfer, as they infect many cell types and do not integrate their genome into host-cell chromosomes. In addition, they have been widely studied as cytolytic viruses, termed oncolytic adenoviruses in cancer therapy. Ads are non-enveloped viruses with a linear double-stranded DNA genome of 30–38 kb which encodes 30–40 genes. At least 52 human Ad serotypes have been identified and classified into seven species, A–G. The Ad capsid has icosahedral symmetry and is composed of 252 capsomers, of which 240 are located on the facets of the capsid and consist of a trimeric hexon protein and the remaining 12 capsomers, the pentons, are at the vertices and comprise the penton base and projecting fibre protein. The entry of Ads into human cells is a two-step process. In the first step, the fibre protein mediates a primary interaction with the cell, effectively tethering the virus particle to the cell surface via a cellular attachment protein. The penton base then interacts with cell-surface integrins, leading to virus internalization. This interaction of the fibre protein with a number of cell-surface molecules appears to be important in determining the tropism of adenoviruses. Ads from all species, except species B and certain serotypes of species D, utilize CAR (coxsackie and adenovirus receptor) as their primary cellular-attachment protein, whereas most species B Ads use CD46, a complement regulatory protein. Such species-specific differences, as well as adaptations or modifications of Ads required for applications in gene therapy, form the major focus of the present review.

Self-assembled terplexes for targeted gene delivery with improved transfection

To improve transfection efficiency and to incorporate target ligands to the gene delivery systems, heparin and heparin-biotin were introduced to complexes of polyamidoamine dendrimer and DNA (PAMAM/DNA) via electrostatic interactions to form self-assembled PAMAM/DNA/heparin and PAMAM/DNA/heparin-biotin terplexes, respectively. The self-assembled terplexes were characterized by agarose gel electrophoresis and particle size analysis. The MTT assay indicated that, after incorporation of heparin and heparin-biotin, the terplexes exhibited decreased cytotoxicity. In addition, as compared with PAMAM/DNA and PAMAM/DNA/heparin complexes, the PAMAM/DNA/heparin-biotin complexes exhibited much higher cellular uptake into HeLa cells due to the specific interactions between biotin and biotin receptors on HeLa cells, which led to the enhanced transfection activity. The PAMAM/DNA/heparin-biotin complexes would be a promising targeting gene delivery system.

Development of chimeric gene regulators for cancer-specific gene therapy with both transcriptional and translational targeting

Cancer gene therapy has been of great challenge in achieving maximal high levels of specificity and more rational efficiency in target cancer cell. We herein developed a novel approach for cancer-specific gene therapy using both transcriptional and translational targeting regulation. We integrated the tumor-specific gene promoter of hTERT, the 5'UTR of bFGF-2, the enhancer of woodchuck hepatitis virus post-transcriptional regulatory element (WRE), and/or the 3'UTR of the human EGFR into two major chimeric gene regulators. We found that chimeric gene regulator I (hTERT_5'UTR...WRE_BGHpolyA) enhanced the specificity of expression in hepatocellular carcinoma (HCC) cells up to 300% in total due to increases at both the transcriptional and translational levels but only 120-200% enhancement at the transcriptional level and 120-180% enhancement at the translational level. In addition, chimeric gene regulator II (hTERT_5'UTR...WRE_3'UTR_BGHpolyA) improved the specificity to 550% and also highly strengthened the stability of the mRNA. In vitro cytotoxicity assays demonstrated that HCC cell growth was inhibited by HSV-1 TK expression under the control of both chimeric regulators, with a relative cell viability of approximately 80% for 2 days and approximately 85% for 4 days after transfection, respectively. These observations represent a new approach for highly tumor-specific gene expression and also provide insights into application to cancer gene therapy.

Analysis of adenovirus trans-complementation-mediated gene expression controlled by melanoma-specific TETP promoter in vitro

BACKGROUND

Human adenoviruses (Ads) have substantial potential for clinical applications in cancer patients. Conditionally replicating adenoviruses (CRAds) include oncolytic adenoviruses in which expression of the immediate early viral transactivator protein E1A is controlled by a cancer cell-selective promoter. To enhance efficacy, CRAds are further armed to contain therapeutic genes. Due to size constraints of the capsid geometry, the capacity for packaging transgenes into Ads is, however, limited. To overcome this limitation, the employment of E1A-deleted replication-deficient viruses carrying therapeutic genes in combination with replication-competent CRAd vectors expressing E1A in trans has been proposed. Most trans-complementing studies involved transgene expressions from strong ubiquitous promoters, and thereby relied entirely on the cancer cell specificity of the CRAd vector.

RESULTS

Here we tested the trans-complementation of a CRAd and a replication-deficient transgene vector containing the same cancer cell-selective promoter. Hereto, we generated two new vectors expressing IL-2 and CD40L from a bicistronic expression cassette under the control of the melanoma/melanocyte-specific tyrosinase enhancer tyrosinase promoter (TETP), which we previously described for the melanoma-specific CRAd vector AdDeltaEP-TETP. These vectors gave rise to tightly controlled melanoma-specific transgene expression levels, which were only 5 to 40-fold lower than those from vectors controlled by the nonselective CMV promoter. Reporter analyses using Ad-CMV-eGFP in combination with AdDeltaEP-TETP revealed a high level of trans-complementation in melanoma cells (up to about 30-fold), but not in non-melanoma cells, unlike the AdCMV-eGFP/wtAd5 binary vector system, which was equally efficient in melanoma and non-melanoma cells. Similar findings were obtained when replacing the transgene vector AdCMV-eGFP with AdCMV-IL-2 or AdCMV-CD40L. However, the combination of the novel AdTETP-CD40L/IL-2 vector with AdDeltaEP-TETP or wtAd5 gave reproducible moderate 3-fold enhancements of IL-2 by trans-complementation only.

CONCLUSIONS

The cancer cell-selective TETP tested here did not give the expected enforceable transgene expression typically achieved in the Ad trans-complementing system. Reasons for this could include virus-mediated down regulation of limiting transcription factors, and/or competition for such factors by different promoters. Whether this finding is unique to the particular promoter system tested here, or also occurs with other promoters warrants further investigations.

Synthesis, functionalization, and biomedical applications of multifunctional magnetic nanoparticles

Synthesis of multifunctional magnetic nanoparticles (MFMNPs) is one of the most active research areas in advanced materials. MFMNPs that have magnetic properties and other functionalities have been demonstrated to show great promise as multimodality imaging probes. Their multifunctional surfaces also allow rational conjugations of biological and drug molecules,making it possible to achieve target-specific diagnostics and therapeutics.This review fi rst outlines the synthesis of MNPs of metal oxides and alloy sand then focuses on recent developments in the fabrication of MFMNPs of core/shell, dumbbell, and composite hybrid type. It also summarizes the general strategies applied for NP surface functionalization. The review further highlights some exciting examples of these MFMNPs for multimodality imaging and for target-specific drug/gene delivery applications.

Effects of transferred NK4 gene on proliferation, migration, invasion and apoptosis of human prostate cancer DU145 cells

We investigated the ability of NK4, an antagonist of human hepatocyte growth factor (HGF), to inhibit the influence of HGF on proliferation, migration, invasion and apoptosis of human prostate cancer cells. Expression vector pBudCE4.1-EGFP-NK4 containing NK4 cDNA was used to transfect human prostate cancer DU145 cells, and the effects of the autocrine NK4 on tumor cell proliferation, migration, invasion and apoptosis were assessed in vitro. In vivo, we subcutaneously implanted DU145 cells, mock-transfected clone (DU145/empty vector) cells and NK4-transfected clone (DU145/NK4) cells into nude mice, and then evaluated tumor growth, cell proliferation and cell apoptosis in vivo. We found that DU145/NK4 cells expressed NK4 protein. In the in vitro study, autocrine NK4 attenuated the HGF-induced tumor cell proliferation, migration and invasion, and stimulated apoptosis. Furthermore, autocrine NK4 effectively inhibited the HGF-induced phosphorylation of c-Met, extracellular signal-regulated kinase-1 (ERK1). and protein kinase B 1/2 (Akt1/2). Histological examination revealed that autocrine NK4 inhibited proliferation and accelerated apoptosis of prostate cancer cells. These results show that genetic modification of DU145 cells with NK4 cDNA yields a significant effect on their proliferation, migration, invasion and apoptosis. Molecular targeting of HGF/c-Met by NK4 could be applied as a novel therapeutic approach to prostate cancer.