Bacteriophage-Mediated Cancer Gene Therapy

Abstract

Bacteriophages have long been considered only as infectious agents that affect bacterial hosts. However, recent studies provide compelling evidence that these viruses are able to successfully interact with eukaryotic cells at the levels of the binding, entry and expression of their own genes. Currently, bacteriophages are widely used in various areas of biotechnology and medicine, but the most intriguing of them is cancer therapy. There are increasing studies confirming the efficacy and safety of using phage-based vectors as a systemic delivery vehicle of therapeutic genes and drugs in cancer therapy. Engineered bacteriophages, as well as eukaryotic viruses, demonstrate a much greater efficiency of transgene delivery and expression in cancer cells compared to non-viral gene transfer methods. At the same time, phage-based vectors, in contrast to eukaryotic viruses-based vectors, have no natural tropism to mammalian cells and, as a result, provide more selective delivery of therapeutic cargos to target cells. Moreover, numerous data indicate the presence of more complex molecular mechanisms of interaction between bacteriophages and eukaryotic cells, the further study of which is necessary both for the development of gene therapy methods and for understanding the cancer nature. In this review, we summarize the key results of research into aspects of phage-eukaryotic cell interaction and, in particular, the use of phage-based vectors for highly selective and effective systemic cancer gene therapy.

Keywords: bacteriophages; cancer gene therapy; gene delivery.

Figure 1

The structures of (A) M13 phage, (B) T4 phage and (C) T7 phage.

Figure 2

(A) Structure of RGD4C-targeted AAV/phage (AAVP) hybrid virus. The chimeric virus displays several copies of the RGD4C peptide on its pIII proteins to serve as a targeting ligand which specifically binds to β3 integrin receptors. The AAVP contains a therapeutic gene expression cassette flanked by AAV inverted terminal repeats (ITRs) and includes the CMV or Grp78 promoter; (B) Cancer gene therapy using the AAVP vector. (1) Suicide gene therapy mediated by the transformation of ganciclovir (GCV) to the toxic metabolite GCV-triphosphate under the influence of the herpes simplex virus thymidine kinase (HSVtk) expressed by AAVP in target cancer cells. (2) The delivery and expression of tumor necrosis factor α (TNF-α) by the AAVP in cancer cells leads to the release of this multifunctional protein and its binding to cell-surface receptors. The interaction of TNF-α with tumor necrosis factor receptor 1 (TNFR1) leads to the activation of various apoptotic pathways and cancer cell death, mediating cytokine gene therapy. (3) The goal of p53 gene replacement therapy is to disable the defective mutant tumor suppressor p53 gene (mTP53) and to simultaneously introduce the native functional p53 gene. Disabling the mTP53 can be mediated by combining the AAVP vector with clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9 (CRISPR/Cas9) technology, targeting the desired nucleotide sequence and generating DNA double-strand breaks.