NOAA-USDA Research Finds Fish-Killing Toxin Holds Promising Cancer Applications

September 8, 2009

Euglena sanguinia.

Euglena sanguinia.

High resolution (Credit: NOAA)

A powerful fish-killing toxin could have cancer-killing properties as well, according to collaborative research led by the U.S. Department of Agriculture’s microbiologist Paul V. Zimba and NOAA chemist Peter Moeller.

The toxin, called euglenophycin, has a molecular structure similar to that of solenopsin, an alkaloid from fire ant venom known to inhibit tumor development. The findings were published in the online July 15 issue of Toxicon.

“This preliminary work demonstrates the tremendous potential for discovery of novel and effective new treatments for a variety of human diseases including cancer,” said Paul Sandifer, Ph.D., senior science advisor to the NOAA administrator. “By studying freshwater and marine organisms, NOAA and its partners stand to make important gains for human health and well being.”

Euglenophycin could have a promising future as a cancer treatment. Laboratory tests have shown that even low concentrations of euglenophycin led to a significant decrease in cancer cell growth, and can kill cancer cells. Preliminary studies have shown the toxin to be especially effective in fighting renal cancer, one of the most challenging cancers to beat. Future research will test whether it also can prevent the formation of tumors. Euglenophycin also may have applications as a powerful insecticide.

This work grew out of observations of a mysterious disease killing fish in the ponds of a commercial aquaculture facility in North Carolina in 2002. More than 21,000 striped bass died in July and August, with losses valued at more than $100,000.

To find out why the fish had died, Zimba and Moeller collaborated with Michigan State University biologist Richard Triemer. Zimba works at the Agricultural Research Service Catfish Genetics Research Unit in Stoneville, Miss., which is the principal intramural scientific research agency of the U.S. Department of Agriculture. The scientists isolated and analyzed dissolved compounds, bacteria and algae from samples of the pond water the dead fish lived in.

Their research, published in the Journal of Fish Disease in 2004, identified the culprits as Euglena sanguinea and E. granulate, two species of freshwater algae that had generally been considered benign. Laboratory tests have since confirmed that euglenophycin, the toxin found in these algae, is deadly to fish. Catfish exposed to its purified form died within four hours.

Moeller, working in NOAA’s Center for Human Health Risk at the Hollings Marine Laboratory in Charleston, S.C., purified the active compounds and mapped the molecular structure of euglenophycin, the algal toxin responsible for the fish kills.

The 2002 fish die-off was the first report of freshwater algae killing fish, but it wasn’t the last. Zimba and his colleagues have since confirmed 11 additional occasions in which euglenoid algae have caused fish to die in aquaculture ponds. Losses from these events, which have affected striped bass, tilapia and channel catfish, may have exceeded $1.1 million. The scientists are seeking agency patent protection on the toxin, and are currently investigating its properties.

NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.