Towards PDT with Genetically Encoded Photosensitizer KillerRed: A Comparison of Continuous and Pulsed Laser Regimens in an Animal Tumor Model

PLoS One. 2015 Dec 11;10(12):e0144617. doi: 10.1371/journal.pone.0144617. eCollection 2015.

Abstract

The strong phototoxicity of the red fluorescent protein KillerRed allows it to be considered as a potential genetically encoded photosensitizer for the photodynamic therapy (PDT) of cancer. The advantages of KillerRed over chemical photosensitizers are its expression in tumor cells transduced with the appropriate gene and direct killing of cells through precise damage to any desired cell compartment. The ability of KillerRed to affect cell division and to induce cell death has already been demonstrated in cancer cell lines in vitro and HeLa tumor xenografts in vivo. However, the further development of this approach for PDT requires optimization of the method of treatment. In this study we tested the continuous wave (593 nm) and pulsed laser (584 nm, 10 Hz, 18 ns) modes to achieve an antitumor effect. The research was implemented on CT26 subcutaneous mouse tumors expressing KillerRed in fusion with histone H2B. The results showed that the pulsed mode provided a higher rate of photobleaching of KillerRed without any temperature increase on the tumor surface. PDT with the continuous wave laser was ineffective against CT26 tumors in mice, whereas the pulsed laser induced pronounced histopathological changes and inhibition of tumor growth. Therefore, we selected an effective regimen for PDT when using the genetically encoded photosensitizer KillerRed and pulsed laser irradiation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Colonic Neoplasms / drug therapy*
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Female
  • Gene Expression
  • Green Fluorescent Proteins / genetics*
  • Green Fluorescent Proteins / metabolism
  • Histones / genetics*
  • Histones / metabolism
  • Humans
  • Lasers
  • Light
  • Mice
  • Mice, Inbred BALB C
  • Neoplasm Transplantation
  • Optical Imaging
  • Photochemotherapy / instrumentation
  • Photochemotherapy / methods*
  • Photosensitizing Agents / chemistry*
  • Photosensitizing Agents / metabolism
  • Recombinant Fusion Proteins / genetics*
  • Recombinant Fusion Proteins / metabolism
  • Xenograft Model Antitumor Assays

Substances

  • Histones
  • Photosensitizing Agents
  • Recombinant Fusion Proteins
  • killer red protein, Anthomedusae
  • Green Fluorescent Proteins

Grant support

This work was supported by the Russian Scientific Foundation (#14-25-00129) to KL, and the Russian Foundation for Basic Research (#14-02-00860) to VK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.