From San Francisco, at a meeting of the American Association for Cancer Research
Scientists in Japan have found that a protein fragment dubbed NK4 can stall the development of pancreatic cancer in mice.
The researchers isolated NK4 in 1989 by taking apart a protein called hepatocyte growth factor (HGF), which normally attaches to a receptor molecule on the surface of cells. In tumor cells, HGF’s attachment can rev up metabolism and set the cell on a cancerous growth path.
In an attempt to short-circuit that effect, the researchers tested NK4 to see if it would bind to the receptor in place of HGF and also block the growth factor’s cancer-triggering actions in vulnerable tissues.
In test-tube studies, it did both. To follow up, the researchers injected human pancreatic tumor cells into the pancreases of mice. Four days later, some of the mice got injections of NK4, while others received an inert saline injection.
After 4 weeks, tumors in the NK4-treated mice were only one-third the size of those in the mice that got the saline injections, says biochemist Kunio Matsumoto of Osaka University School of Medicine.
The mice receiving NK4 also survived longer on average than the others. “We found that [NK4] inhibits metastasis,” the deadly process by which cancer spreads between organs, says Matsumoto.
The NK4-treated mice also had about one-third as much blood vessel formation around their tumors. The researchers hadn’t expected NK4 to inhibit this vessel growth, called angiogenesis. “It was lucky,” says Matsumoto.
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The Japanese researchers “have taken the business end of the [HGF] molecule and . . . used it to fake out the cellular metabolism” that would otherwise lead to cancerous growth, says Daniel D. Karp of the Beth Israel Deaconess Medical Center in Boston.