Optical imaging: bacteria, viruses, and mammalian cells encoding light-emitting proteins reveal the locations of primary tumors and metastases in animals

Abstract

Early detection of tumors and their metastases is crucial for the prognosis of cancer treatment. Traditionally, tumor detection is achieved by various methods, including magnetic resonance imaging and computerized tomography. With the recent cloning, cellular expression, and real-time imaging of light-emitting proteins, such as Renilla luciferase (Ruc), bacterial luciferase (Lux), firefly luciferase (Luc), green fluorescent protein (GFP), or Ruc-GFP fusion protein, significant efforts have been focused on using these marker proteins for tumor detection. It has also been demonstrated that certain bacteria, viruses, and mammalian cells (BVMC), when administered systemically, are able to gain entry and replicate selectively in tumors. In addition, many tissue/tumor specific promoters have been cloned which allow transgene expression specifically in tumor tissues. Therefore, when light-emitting protein encoded BVMC are injected systemically into rodents, tumor-specific marker gene expression is achieved and is detected in real time based on light emission. Consequently, the locations of primary tumors and previously unknown metastases in animals are revealed in vivo. In the future it will likely be feasible to use engineered light-emitting BVMC as probes for tumor detection and as gene-delivery vehicles in vivo for cancer therapy.

Inhibition and eradication of human glioma with tumor-targetingSalmonella typhimuriumin an orthotopic nude-mouse model

“…31 Bacteria engineered to express light-emitting proteins have been shown to be readily visualized in tumors. 32,33 Induction of bacterial mutations with nitrosoguanidine and selection for auxotrophs of S. typhimurium-GFP. Freshly prepared nitrosoguanidine (NTG; 1 mg/ml in sterile water) was added to the washed culture to a final concentration of 100 μg/ ml in Tris-maleic acid buffer (pH 6.0).…”

Optical imaging of bacterial infection models

“…This has sparked an interest in using bioluminescent microbes to image tumors and metastases [33]. The bacteria can be delivered systemically and will localize selectively within tumors to provide an imaging signal for many days.…”

Anti-VEGF single-chain antibody GLAF-1 encoded by oncolytic vaccinia virus significantly enhances antitumor therapy

“…VACV has a large genome and a high capacity for recombinant gene delivery without compromising the oncolytic activity. It has also been shown to colonize tumor tissues selectively (11). GLV-1h68 is replication competent, which leads to high amplification in tumor tissue (8).…”