Researchers from Northwestern University have found a gene variation that is linked with a decreased risk of colorectal cancer, according to a new study.

The research team has identified the mutation in a gene that creates a hormone called adiponectin. The hormone is secreted by fat cells.

Higher adiponectin levels in the blood are associated with obesity and previous research has linked obesity with an increased risk of develop colorectal cancer.

However, this single mutation in the adiponectin gene is associated with a 30 per cent reduction in the risk of developing the colorectal cancer. This means that the mutation may actually lower the risk level of a person who is at high risk for the disease.

"If these exciting results can be confirmed in other studies, the adiponectin axis may emerge as an important modifier of colorectal cancer risk," the authors conclude in their study.

The research was led by Dr. Virginia G. Kaklamani of the Feinberg School of Medicine at Northwestern University and conducted by a team of scientists from a number of U.S. institutions.

They conducted two studies, which together included nearly 1,500 people.

The findings were published in the Journal of the American Medical Association.

Abstract:

Variants of the Adiponectin (ADIPOQ) and Adiponectin Receptor 1 (ADIPOR1) Genes and Colorectal Cancer Risk

Virginia G. Kaklamani, MD, DSc; Kari B. Wisinski, MD; Maureen Sadim, BS; Cassandra Gulden, MS; Albert Do, BS; Kenneth Offit, MD, MPH; John A. Baron, MD; Habibul Ahsan, MD, MPH; Christos Mantzoros, MD, MPH; Boris Pasche, MD, PhD

Context: Current epidemiological evidence suggests an association between obesity, hyperinsulinemia, and colorectal cancer risk. Adiponectin is a hormone secreted by the adipose tissue, and serum levels are inversely correlated with obesity and hyperinsulinemia. While there is evidence of an association between circulating adiponectin levels and colorectal cancer risk, no association between genes of the adiponectin pathway and colorectal cancer have been reported to date.

Objective: To determine the association of 10 haplotype-tagging single-nucleotide polymorphisms (SNPs) of the adiponectin (ADIPOQ) and adiponectin receptor 1 (ADIPOR1) genes with colorectal cancer risk.

Design, Setting, and Patients: Two case-control studies including patients with a diagnosis of colorectal cancer and controls were recruited between 2000 and 2007. Case-control study 1 included a total of 441 patients with a diagnosis of colorectal cancer and 658 controls; both groups were of Ashkenazi Jewish ancestry and from New York, New York. Case-control study 2 included 199 patients with a diagnosis of colorectal cancer and 199 controls from Chicago, Illinois, matched 1:1 for sex, age, and ethnicity.

Main Outcome Measures: ADIPOQ and ADIPOR1 SNP frequency among cases and controls.

Results: In study 1, after adjustment for age, sex, and SNPs from the same gene, 3 ADIPOQ SNPs and 1 ADIPOR1 SNP were associated with colorectal cancer risk: rs266729 (adjusted odds ratio [AOR], 0.72; 95% confidence interval [CI], 0.55-0.95) and rs822396 (AOR, 0.37; 95% CI, 0.14-1.00) were associated with decreased risk whereas rs822395 (AOR, 1.76; 95% CI, 1.09-2.84) and rs1342387 (AOR, 1.79; 95% CI, 1.18-2.72) were associated with increased risk. In study 2, after adjustment for age, sex, race, and SNPs from the same gene, the ADIPOQ SNP rs266729 was associated with a decreased colorectal cancer risk of similar magnitude as in study 1 (AOR, 0.52; 95% CI, 0.34-0.78). Combined analysis of both studies shows an association of rs266729 with decreased colorectal cancer risk (AOR, 0.73; 95% CI, 0.53-0.99).

Conclusion: The SNP rs266729, which tags the 5' flanking region of the ADIPOQ gene, is associated with decreased colorectal cancer risk.