New light therapy to treat cancers

British researchers took a lesson from the common firefly in an investigational treatment for cancer.

Using a firefly gene, researchers produced bioluminescent light to treat modified cancer cells in the laboratory. The goal was to find a new version of light therapy to treat cancers that respond well to the therapy but are inaccessible by regular photodynamic therapy that use lasers or lamps.

Photodynamic therapy works by “exciting” a photosensitive substance to produce other substances, such as singlet oxygen or free radicals, to destroy cancerous cells. The treatment is often the first choice of doctors because it causes few side effects. However, external forms of the treatment can’t reach deeply lying tumors. Invasive methods to deliver light into these tumors — such as placing optical fibers into the tumor via needles — often fail to hit all the cancerous cells.

The use of chemically produced light such as that produced by the firefly could overcome these problems because it would cover all the cells. According to the authors, it has already shown promise in the treatment of a virus that causes anemia in horses. When used with other substances, the therapy resulted in a 10-fold decrease in the infectiousness of the virus. Research also suggests it is possible to deliver the firefly gene that produces bioluminescent light to prostate cancer cells.

In this laboratory study, investigators inserted the gene into modified cancer cells known as fibroblasts. They then added a photosensitizer. This produced toxic substances that caused the cancer cells to die.

The authors write, “Our data, for the first time, demonstrate cytotoxicity through the production of intracellular light and introduce the possibility of targeting this light specifically to tumor cells for a potent and plausible modality for certain cancer treatments.”

SOURCE: Cancer Research, 2003;63:1818-1821