Format

Send to

Choose Destination
PLoS One. 2015 Jul 27;10(7):e0131518. doi: 10.1371/journal.pone.0131518. eCollection 2015.

Photodynamic Treatment of Tumor with Bacteria Expressing KillerRed.

Author information

1
Medical Photonics Research Center, Hamamatsu University School of Medicine, Handayama, Higashi-ku, Hamamatsu, Japan.

Abstract

Photodynamic therapy (PDT) is a cancer treatment modality in which a photosensitizing dye is administered and exposed to light to kill tumor cells via the production of reactive oxygen species (ROS). A fundamental obstacle for PDT is the low specificity for staining solid tumors with dyes. Recently, a tumor targeting system guided by anaerobic bacteria was proposed for tumor imaging and treatment. Here, we explore the feasibility of the genetically encoded photosensitizer KillerRed, which is expressed in Escherichia coli, to treat tumors. Using nitroblue tetrazolium (NBT), we detected a lengthy ROS diffusion from the bodies of KillerRed-expressing bacteria in vitro, which demonstrated the feasibility of using bacteria to eradicate cells in their surroundings. In nude mice, Escherichia coli (E. coli) expressing KillerRed (KR-E. coli) were subcutaneously injected into xenografts comprising CNE2 cells, a human nasopharyngeal carcinoma cell line, and HeLa cells, a human cervical carcinoma cell line. KR-E. coli seemed to proliferate rapidly in the tumors as observed under an imaging system. When the intensity of fluorescence increased and the fluorescent area became as large as the tumor one day after KR-E. coli injection, the KR-E. coli-bearing tumor was irradiated with an orange light (λ = 540-580 nm). In all cases, the tumors became necrotic the next day and were completely eliminated in a few days. No necrosis was observed after the irradiation of tumors injected with a vehicle solution or a vehicle carrying the E. coli without KillerRed. In successfully treated mice, no tumor recurrence was observed for more than two months. E. coli genetically engineered for KillerRed expression are highly promising for the diagnosis and treatment of tumors when the use of bacteria in patients is cleared for infection safety.

PMID:
26213989
PMCID:
PMC4516238
DOI:
10.1371/journal.pone.0131518
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center