Blood protein may hold key to stopping tumour growth in cancer patients

A recent discovery by researchers at Wake Forest University School of Medicine could clear the way for a new drug that inhibits tumour growth in cancer patients and could potentially help in the healing of wounds.

The discovery stems from a study, recently published in the Proceedings of the National Academy of Sciences of the United States of America, in which researchers looked at angiogenesis the body's formation of new blood vessels from existing blood vessels and how some blood proteins are involved in that process and affect blood vessel growth.

Researchers found that a protein called ferritin binds to and cripples the ability of another blood protein, called HKa, to shut down blood vessel growth. Because new blood vessels supply a steady stream of nutrients and oxygen that are essential for tumour growth, researchers found that the binding of the two proteins actually assists in new blood vessel formation by removing HKa's influence and therefore promotes tumour growth.

The finding led researchers to the hypothesis that if they can somehow prevent the binding of ferritin and HKa, it will allow HKa to prevent new blood vessel growth and therefore block the growth of tumours.

The finding also has possible implications for wound care. In order to heal, wounds need blood vessel growth. It is therefore possible that by increasing the binding of ferritin to HKa, one could increase the rate at which a serious wound heals.

"It's been known for a long time that levels of ferritin are increased in people with tumours, but it's never been understood why that happens," said Suzy V. Torti, PhD, the study's lead investigator, an associate professor of biochemistry and an expert in iron biology at the School of Medicine. "Ferritin appears to play an important role in blood vessel formation. Further, the interaction between ferritin and HKa may represent a new area of interest for possible drug development."

For the study, researchers injected mice with prostate cancer cells to determine how ferritin and HKa affected the formation of new blood vessels.

The mice injected with the cancer cells grew tumours. But when researchers mixed HKa with the tumour cells, the HKa inhibited blood vessel formation. When researchers added ferritin to the mixture of HKa and cancer cells, however, the ferritin restored blood vessel formation, allowing the tumours to grow again.

"Blood vessels can either be helpful, for example in wound healing, or they can be harmful, for example by favouring tumour growth," Torti said. "Our new finding is that the interaction between ferritin and HKa can influence blood vessel formation. This finding could serve as the basis for strategies to either inhibit or stimulate blood vessels. This opens up a new realm of potential ways to treat tumours or other conditions that depend on new blood vessel formation."

The research team, supported by a National Institutes of Health grant, has begun work to develop an anti-tumour drug based on their findings.

(Source: Wake Forest University Baptist Medical Center: Proceedings of the National Academy of Sciences: April 2009)