Energy Balance-Related Factors and Risk of Colorectal Cancer Expressing Different Levels of Proteins Involved in the Warburg Effect

BACKGROUND: Energy balance-related factors [body mass index (BMI), waist circumference, physical activity] have been associated with colorectal cancer risk. Warburg effect activation via PI3K/Akt signaling is one of the proposed mechanisms. We investigated whether energy balance-related factors were associated with risk of Warburg subtypes in colorectal cancer.METHODS: We investigated this using immunohistochemistry for six proteins involved in the Warburg effect (LDHA, GLUT1, MCT4, PKM2, P53, PTEN) on tissue microarrays of 2,399 incident colorectal cancer cases from the prospective Netherlands Cohort Study (n total = 120,852; n subcohort = 5,000; aged 55-69 in 1986; 20.3 years follow-up). Data analyses included 3,911 subcohort members and 1,972 colorectal cancer cases with complete covariate data. Expression levels of all proteins were combined into a pathway-based sum score and categorized into three "Warburg subtypes" (Warburg-low/moderate/high). Multivariable Cox regression analyses were used to estimate associations of BMI, clothing size (waist circumference proxy), and physical activity with Warburg subtypes in colorectal cancer.RESULTS: BMI and clothing size were positively associated with Warburg-moderate and Warburg-high colon cancer risk in men (P heterogeneity = 0.192). In women, clothing size was positively associated with Warburg-low and Warburg-high colon cancer (P heterogeneity = 0.005). Nonoccupational physical activity was inversely associated with Warburg-low and Warburg-moderate colon cancer in women (P heterogeneity = 0.045), but positively associated with Warburg-high rectal cancer in men (P heterogeneity = 0.089).CONCLUSIONS: The Warburg effect might be involved in associations between adiposity and colon cancer risk, though additional mechanisms could be at play in women as well. The inverse association between physical activity and colon cancer might be explained by mechanisms other than the Warburg effect.IMPAC