(HealthDay News) — Obesity and physical inactivity are associated with a higher risk of WNT/β-catenin (CTNNB1)-negative colorectal cancer, but are not associated with CTNNB1-positive cancer risk, according to a study published online Feb. 26 in Cancer Research.

To examine whether tumor CTNNB1 status influences cellular sensitivity to obesity and physical activity, Teppei Morikawa, M.D., Ph.D., from the Dana-Farber Cancer Institute in Boston, and colleagues used tissue immunohistochemistry data on nuclear CTNNB1 expression from 861 incident rectal and colon cancers identified during follow-up of 109,046 women in the Nurses’ Health Study and 47,684 men in the Health Professionals Follow-up Study.

The researchers found that greater body mass index correlated with a significantly elevated risk of CTNNB1-negative cancer (multivariate hazard ratio [HR], 1.34 for 5.0 kg/m2 increment; Ptrend = 0.0001) but not with the risk of CTNNB1-positive cancer (multivariate HR, 1.07 for 5.0 kg/m2 increment; Ptrend = 0.36). There was a significantly lower risk of CTNNB1-negative cancer with higher physical activity levels (multivariate HR, 0.93 for 10 metabolic equivalent task [MET]-hours/week increment; Ptrend = 0.044) but no association with CTNNB1-positive cancer risk (multivariate HR, 0.98 for 10 MET-hours/week increment; Ptrend = 0.60).

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“These data suggest that energy balance status exerts its effect in a specific carcinogenic pathway that is less likely dependent on WNT/ CTNNB1 activation,” write the authors. “In the future, we may be able to identify individuals who are susceptible to the development of CTNNB1-negative tumors, and lifestyle preventive measures can be taken.”

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