More evidence supports tumor-shrinking therapy

September 17, 1999
Web posted at: 9:41 AM EDT (1341 GMT)

By Rochelle Jones

(WebMD) -- Cancer patients may eventually be treated with drugs that shrink tumors without the traumatic side effects associated with surgery, chemotherapy or radiation, researchers reported in this week's journal Science.

Researchers at Children's Hospital Medical Center in Boston reported that an anti-clotting protein caused tumors to shrink dramatically with minimal toxic side effects when it was injected into mice. The protein caused the nutrient-rich blood supply to the tumor to be cut off.

The study is significant because the results offer further evidence that the growth of cancer tumors may be stopped by simply eliminating the tumor's blood supply, said Dr. Michael O'Reilly, first author of the article and a research associate at Children's Hospital. Principal investigator Dr. Judah Folkman was unavailable for comment.

Previous research suggested that small clusters of abnormal cells may grow into large malignant tumors because they are supplied with nutrients through tiny blood vessels, which are constantly multiplying by a process known as angiogenesis. With a steady source of nutrients, a tumor can grow quickly, expanding to a billion malignant cells in a few months.

Unlike other cancer treatments, anti-angiogenic therapy does not try to destroy cancer cells. Instead, the therapy aims at inhibiting a tumor's growth by interfering with the proliferation of blood vessels, which are thinner than a single strand of hair.

"It's a very specific therapy," O'Reilly said. "It's potentially a very powerful strategy that may work without side effects."

O'Reilly said that he and other researchers would soon begin working with Genzyme Corp., a Cambridge, Massachusetts-based biotechnology company that will help to produce enough of the anti-angiogenic substance to conduct more animal studies and, if all goes well, human clinical trials. However, O'Reilly explained that proteins can vary from "batch to batch" and can often be difficult to store.

Among the first to research anti-angiogenic compounds, O'Reilly and Folkman discovered last year that the protein angiostatin could reduce cancer tumors in animals to a microscopic size and keep them dormant as long as the compound was administered.

However, O'Reilly is cautiously optimistic, especially after scientists couldn't replicate Folkman's highly publicized results of angiostatin's ability to shrink tumors. After The New York Times first reported Folkman's discovery last May, stocks of EntreMed, the Rockville, Maryland-based biotechnology company that makes angiostatin, skyrocketed from 12 1/16 to a high of 85 in one day.