exercise exerts its anti-breast cancer effect via IGF axis

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Exercise Exerts Anti-Cancer Effect Via the Insulin-Like Growth Factor Axis



By Martha Kerr

NEW YORK (Reuters Health) May 29 - The anti-cancer effects of exercise are due to an increase in insulin-like binding protein-3 (IGFBP-3), which inhibits insulin-like growth factor-1 (IGF-1), blocking IGF-1's proliferative effect on cell growth, according to Australian researchers.

In a study published in the May issue of Gut, Dr. Andrew M. M. Haydon and colleagues at Manash Medical School in Melbourne identified new cases of colorectal cancer in the Melbourne Collaborative Cohort Study, a prospective study of 41,528 adults recruited between 1990 and 1994.

The investigators looked at baseline body mass index and level of physical activity reported and compared baseline levels of insulin-like growth factor-1 (IGF-1) or insulin-like growth factor binding protein-3 (IGFBP-3) with those measurements.

Dr. Haydon had information on 443 colon cancer patients at follow-up approximately 5.6 years later.

Among subjects who were physically active, an increase in IGFBP-3 of 26.2 nmol/l was associated with a 48% reduction in colon cancer-specific deaths, for a hazard ratio of 0.52. No association was seen for IGF-1.

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

Dr. Haydon told Reuters Health that that "physical activity can increase IGFBP-3 levels, which, in turn, reduces the amount of free IGF-1. The mechanism is not well understood, but may relate to serum insulin levels, as hyperinsulinaemia has been shown to reduce the production of IGF binding proteins."

IGF-1 has been shown to stimulate cell growth, inhibit apoptosis and promote angiogenesis.

"We did not look at the amount of physical activity needed to reduce colorectal cancer incidence, as we only looked at those from our cohort who had CRC," Dr. Haydon pointed out. "Other studies that have looked at this 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."

Gut 2006;55:689-694.