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HOUSTON, TEXAS. High blood levels of circulating IGF-1 (insulin-like growth factor 1) have been
associated with an increased risk of prostate, breast, colon and lung cancers. Now researchers at the
University of Texas report that patients with bladder cancer have significantly higher levels of IGF-1 and
significantly lower levels of its binding protein (IGF binding protein-3) than do controls.
IGF-1 is found in the blood both in free form (unbound) and bound to its carrier protein, IGF binding protein- 3. It can only exert its effects of stimulating tumour proliferation and reducing apoptosis (programmed cell death) in the unbound form. Thus it would make sense that higher levels of IGF binding protein-3 and lower levels of IGF-1 would be beneficial when it comes to cancer prevention.
This is exactly what the researchers found. They compared blood plasma levels of IGF-1 and IGF binding
protein-3 in 154 bladder cancer patients and 154 age and sex matched controls. They found that study
participants in the highest quartile of IGF-1 levels had 3 times the risk of bladder cancer than did participants
in the lowest quartile (OR=3.10). They also found that participants with the highest levels of insulin binding
protein-3 had a 3 times lower risk of bladder cancer than did those with the lowest levels (OR=0.38). A
combination of high IGF-1 levels and low insulin binding protein-3 levels was particularly detrimental
conferring a 4-fold increase in risk. The increased risk remained after correcting for other known risk factors
for bladder cancer such as age, ethnicity, and cigarette smoking. The researchers conclude that measuring
blood plasma levels of IGF-1 and IGF binding protein-3 may be useful for assessing bladder cancer
risk.
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