A novel two-step transcriptional activation system for gene therapy directed toward epithelial cells

Applications of tissue-specific and cancer-selective gene promoters for cancer diagnosis and therapy

Current treatment of solid tumors with standard of care chemotherapies, radiation therapy and/or immunotherapies are often limited by severe adverse toxic effects, resulting in a narrow therapeutic index. Cancer gene therapy represents a targeted approach that in principle could significantly reduce undesirable side effects in normal tissues while significantly inhibiting tumor growth and progression. To be effective, this strategy requires a clear understanding of the molecular biology of cancer development and evolution and developing biological vectors that can serve as vehicles to target cancer cells. The advent and fine tuning of omics technologies that permit the collective and spatial recognition of genes (genomics), mRNAs (transcriptomics), proteins (proteomics), metabolites (metabolomics), epiomics (epigenomics, epitranscriptomics, and epiproteomics), and their interactomics in defined complex biological samples provide a roadmap for identifying crucial targets of relevance to the cancer paradigm. Combining these strategies with identified genetic elements that control target gene expression uncovers significant opportunities for developing guided gene-based therapeutics for cancer. The purpose of this review is to overview the current state and potential limitations in developing gene promoter-directed targeted expression of key genes and highlights their potential applications in cancer gene therapy.

Molecular-genetic imaging of cancer

Molecular-genetic imaging of cancer using nonviral delivery systems has great potential for clinical application as a safe, efficient, noninvasive tool for visualization of various cellular processes including detection of cancer, and its attendant metastases. In recent years, significant effort has been expended in overcoming technical hurdles to enable clinical adoption of molecular-genetic imaging. This chapter will provide an introduction to the components of molecular-genetic imaging and recent advances on each component leading to safe, efficient clinical applications for detecting cancer. Combination with therapy, namely, generating molecular-genetic theranostic constructs, will provide further impetus for clinical translation of this promising technology.

Nucleic-acid based gene therapeutics: delivery challenges and modular design of nonviral gene carriers and expression cassettes to overcome intracellular barriers for sustained targeted expression

The delivery of nucleic acid molecules into cells to alter physiological functions at the genetic level is a powerful approach to treat a wide range of inherited and acquired disorders. Biocompatible materials such as cationic polymers, lipids, and peptides are being explored as safer alternatives to viral gene carriers. However, the comparatively low efficiency of nonviral carriers currently hampers their translation into clinical settings. Controlling the size and stability of carrier/nucleic acid complexes is one of the primary hurdles as the physicochemical properties of the complexes can define the uptake pathways, which dictate intracellular routing, endosomal processing, and nucleocytoplasmic transport. In addition to nuclear import, subnuclear trafficking, posttranscriptional events, and immune responses can further limit transfection efficiency. Chemical moieties, reactive linkers or signal peptide have been conjugated to carriers to prevent aggregation, induce membrane destabilization and localize to subcellular compartments. Genetic elements can be inserted into the expression cassette to facilitate nuclear targeting, delimit expression to targeted tissue, and modulate transgene expression. The modular option afforded by both gene carriers and expression cassettes provides a two-tier multicomponent delivery system that can be optimized for targeted gene delivery in a variety of settings.

Virion protein 16 induces demethylation of DNA integrated within chromatin in a novel mammalian cell model

DNA methylation and demethylation play important roles in mediating epigenetic regulation. So far, the mechanism of DNA demethylation remains elusive and controversial. Here, we constructed a plasmid, named with pCBS-luc, that contained an artificial CpG island, eight Gal4 DNA-binding domain binding site, an SV40 promoter, and a firefly luciferase reporter gene. The linearized pCBS-luc plasmid was methylated in vitro by DNA methyltransferase, and transfected into the HEK293 cells. The stable HEK293 transfectants with methylated pCBS-luc (me-pCBS-luc) were selected and obtained. The methylation status of the selected stable cell lines were confirmed by bisulfite sequencing polymerase chain reaction amplification. The methylation status could be maintained even after 15 passages. The virion protein 16 (VP16) was reported to enhance DNA demethylation around its binding sites of the promoter region in Xenopus fertilized eggs. Using our me-pCBS-luc model, we found that VP16 also had the ability to activate the expression of methylated luciferase reporter gene and induce DNA demethylation in chromatin DNA in mammalian cells. Altogether, we constructed a cell model stably integrated with the me-pCBS-luc reporter plasmid, and in this model we found that VP16 could lead to DNA demethylation. We believe that this cell model will have many potential applications in the future research on DNA demethylation and dynamic process of chromatin modification.

The use of a human papillomavirus 18 promoter for tissue-specific expression in cervical carcinoma cells

The use of tissue-specific promoter elements in the treatment of cervical cancer has been explored in this paper. The P₁₀₅ promoter of human papillomavirus 18 (HPV18) was utilised to direct tissue-specific expression in a number of cell types. Expression was examined in three cervical carcinoma cell lines: HeLa (HPV18 positive), SiHa (HPV16 positive), and C33A cells (HPV negative); the epithelial cell line, H1299; and the foetal fibroblast cell line, MRC5, utilising a luciferase expression vector. Expression was highest in the cervical cell lines by a factor of at least 80. The effect of a number of mutations in the P₁₀₅ promoter on expression levels was examined. Three deletion constructs of the long control region (LCR) were investigated: an 800 bp fragment (LCR800), a 400 bp fragment (LCR400), and a 200 bp fragment (LCR200), as well as the full length product LCR of HPV18 (LCR1000). The LCR800 construct of the HPV18 P₁₀₅ promoter had the highest level of expression in the cervical cell lines and was also highest in the HPV18-positive HeLa cell line. Site-directed mutagenesis was then employed on the LCR800 construct to create four further constructs that each had inactivating mutations in one of the four E2 binding sites (E2BSs). Overall, this study indicated that the LCR800 construct of the HPV18 P₁₀₅ promoter could be utilised as a tissuerestricted promoter in cervical cancer cells.

The human and canine TERT promoters function equivalently in human and canine cells

Telomerase targeted cancer gene therapy is being exploited for treatment of human cancer. The high incidence and many comparative aspects of human and canine cancer and the compliance and dedication of dog owners to treat cancer makes the canine pet population a good clinical model for investigating and developing new cancer therapeutics. Here, we report that the human telomerase promoter operates in canine cells, suggesting that human telomerase promoter-driven cancer therapy can be used to treat cancer in canines. Therefore, the canine pet population can act as a clinical model for new drug development based on telomerase therapeutics.