Targeted Photodynamic Virotherapy Armed With a Genetically Encoded Photosensitizer

Mol Cancer Ther. 2016 Jan;15(1):199-208. doi: 10.1158/1535-7163.MCT-15-0344. Epub 2015 Dec 1.

Abstract

Photodynamic therapy (PDT) is a minimally invasive antitumor therapy that eradicates tumor cells through a photosensitizer-mediated cytotoxic effect upon light irradiation. However, systemic administration of photosensitizer often makes it difficult to avoid a photosensitive adverse effect. The red fluorescent protein KillerRed generates reactive oxygen species (ROS) upon green light irradiation. Here, we show the therapeutic potential of a novel tumor-specific replicating photodynamic viral agent (TelomeKiller) constructed using the human telomerase reverse transcriptase (hTERT) promoter. We investigated the light-induced antitumor effect of TelomeKiller in several types of human cancer cell lines. Relative cell viability was investigated using an XTT assay. The in vivo antitumor effect was assessed using subcutaneous xenografted tumor and lymph node metastasis models. KillerRed accumulation resulted in ROS generation and apoptosis in light-irradiated cancer cells. Intratumoral injection of TelomeKiller efficiently delivered the KillerRed protein throughout the tumors and exhibited a long-lasting antitumor effect with repeated administration and light irradiation in mice. Moreover, intratumorally injected TelomeKiller could spread into the regional lymph node area and eliminate micrometastasis with limited-field laser irradiation. Our results suggest that KillerRed has great potential as a novel photosensitizer if delivered with a tumor-specific virus-mediated delivery system. TelomeKiller-based PDT is a promising antitumor strategy to efficiently eradicate tumor cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviridae / genetics
  • Animals
  • Apoptosis
  • Caspase 3 / metabolism
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Disease Models, Animal
  • Female
  • Gene Expression
  • Genetic Therapy
  • Genetic Vectors / genetics
  • HCT116 Cells
  • Humans
  • Light*
  • Mice
  • Neoplasms / genetics*
  • Neoplasms / metabolism*
  • Neoplasms / pathology
  • Neoplasms / therapy
  • Oncolytic Virotherapy*
  • Oncolytic Viruses / genetics
  • Photochemotherapy*
  • Photosensitizing Agents / pharmacology*
  • Reactive Oxygen Species / metabolism
  • Transgenes
  • Tumor Burden
  • Virus Replication
  • Xenograft Model Antitumor Assays

Substances

  • Photosensitizing Agents
  • Reactive Oxygen Species
  • Caspase 3