How exercise might beat cancer

Martha Kerr Reuters

Tuesday, 30 May 2006

Exercise seems to put a brake on runaway cell growth, one of the hallmarks of cancer (Image: iStockphoto)

The anticancer effects of exercise are due to increases in a protein that blocks cell growth and induces cell death, say Australian researchers.

This would slow down runaway cell growth, one of the hallmarks of cancer, the researchers suggest.

But the team, led by Dr Andrew Haydon from Monash Medical School in Melbourne, cannot say how much exercise someone needs to show these effects.

The researchers publish their results in the May issue of the journal Gut.

They identified new cases of colorectal cancer in a prospective study of 41,528 adults recruited between 1990 and 1994.

They then looked at baseline body mass index, level of physical activity reported and compared baseline levels of two proteins: insulin-like growth factor binding protein-3, or IGFBP-3, and insulin-like growth factor-1, or IGF-1.

Analyses centered on 443 colon cancer patients followed for more than 5 years.

Among subjects who were physically active, an increase in IGFBP-3 was associated with a 48% reduction in colon cancer-specific deaths. There seemed to be no association with IGF-1.

For the physically inactive, there was no association between IGF-1 or IGFBP-3 and colon cancer survival.

The researchers conclude that increased levels of IGFBP-3 with exercise blocks IGF-1's proliferative effect on cell growth.

IGF-1 has been shown to stimulate cell growth, inhibit cell death, and promote angiogenesis, the formation of new blood vessels, which tumors need to grow.

"We did not look at the amount of physical activity needed to reduce colorectal cancer incidence," Haydon points out.

"Other studies ... have shown a dose-effect, meaning the more exercise the lower the risk. However, our study did not try to address this issue.

"We were examining the effect of physical activity on one's prognosis following a diagnosis of bowel cancer and the possible mechanisms behind this effect."

For more information about cancer, including fact sheets and where to go for counselling, see the Cancer Council Australia website.