News Article: Plant Hormones Form Basis of New Anti-Cancer Drugs

By Patricia Reaney

LONDON (Reuters) (date unknown) - A hormone used by plants to control their growth is being harnessed by British researchers to develop new targeted treatments for cancer, researchers said on Wednesday.

Plants need the hormone, called indole acetic acid (IAA), to bend shoots toward sunlight to help cuttings grow roots. Scientists at the Cancer Research Campaign (CRC), a leading scientific charity, are using fragments of IAA to kill cancer cells.

The hormone, which is produced by most plants, is harmless to humans. But, in early laboratory studies when scientists used bits of it and coupled them with an enzyme, it produced toxic by-products that destroyed cancerous tumors without harming healthy cells. "The fragmented molecule is only released in the tumor," Professor Peter Wardman told a news conference.

By targeting only the cancerous cells, synthetic drugs based on IAA, called prodrugs, would be highly effective in killing the cancerous cells and would not produce side effects such as hair loss and nausea as do conventional chemotherapy drugs.

"We're really excited that a common or garden plant hormone could fulfill one of the ultimate aims of cancer
research, by providing a drug that only attacks cancerous cells and leaves the rest of the body untouched," Wardman, a scientist at the Gray Cancer Institutes in southern England, explained.

In laboratory studies of cell cultures Wardman and his colleagues used an enzyme called peroxidase, which is derived from the horseradish plant, to trigger the release of the toxic by-products of IAA to destroy tumors.

Early results show that the treatment, which has been patented by the CRC, killed 99 f the cancerous cells and with different types of cancer. Scientists said tests will now have to be done on animals and humans.

"Nearly all of the cells are killed with a single treatment," said Wardman.

The scientists used the horseradish enzyme because it is cheap and well studied. It breaks up IAA into smaller chemicals which react with other molecules in the body to produce the toxins.

To direct the toxins only to the cancerous cells the scientists are using antibodies to tumor cells linked to the
enzymes. Wardman said genetic techniques could also be used to direct the therapy to the cancerous cells.

The scientists are also working on developing prodrugs that can be activated by light, which Wardman said could be used during surgery to kill any remaining cancer cells after the tumor has been removed.

"It's long been the ambition of cancer researchers to develop drugs that directly target the tumor, and thanks to
these amazing plant hormones and a bit of nifty chemistry, we're now a step closer to that ideal," said Professor Gordon McVie, the director general of the CRC.