Energy balance, the PI3K-AKT-mTOR pathway genes, and the risk of bladder cancer

Abstract

We evaluated the association between energy balance and risk of bladder cancer and assessed the joint effects of genetic variants in the mammalian target of rapamycin (mTOR) pathway genes with energy balance. The study included 803 Caucasian bladder cancer patients and 803 healthy Caucasian controls matched to cases by age (+/-5 years) and gender. High energy intake [odds ratio, 1.60; 95% confidence interval (95% CI), 1.23-2.09] and low physical activity (odds ratio, 2.82; 95% CI, 2.10-3.79) were each associated with significantly increased risk of bladder cancer with dose-response pattern (P(trend) < 0.001). However, obesity (body mass index, > or =30) was not associated with the risk. Among 222 single nucleotide polymorphisms, 28 single nucleotide polymorphisms located in six genes of mTOR pathway were significantly associated with the risk. Further, the risk associated with high energy intake and low physical activity was only observed among subjects carrying a high number of unfavorable genotypes in the pathway. Moreover, when physical activity, energy intake, and genetic variants were analyzed jointly, the study population was clearly stratified into a range of low- to high-risk subgroups as defined energy balance status. Compared with subjects within the most favorable energy balance category (low energy intake, intensive physical activity, low number of unfavorable genotypes), subjects in the worst energy balance category (high energy intake, low physical activity, and carrying > or =7 unfavorable genotypes) had 21.93-fold increased risk (95% CI, 6.7-71.77). Our results provide the first strong evidence that physical activity, energy intake, and genetic variants in the mTOR pathway jointly influence bladder cancer susceptibility and that these results have implications for bladder cancer prevention.

Figure 1

Joint effects of energy intake and physical activity in the risk of bladder cancer Note: The number on top of each bar is the odds ratio. ORs with P<0.05 are represented by dotted bars while ORs not significant in blank bars. The reference group is set as low physical activity and high energy intake.

Figure 2

CART analysis of genetic polymorphisms in mTOR pathway in the risk of bladder cancer Note: Odds ratios and 95% CIs (in parenthesis) are presented underneath each terminal node box.