Influence of CHIEF pathway genes on gene expression: a pathway approach to functionality.

Background: Candidate pathway approaches in disease association studies often utilize a tagSNP approach to capture genetic variation. In this paper we assess gene expression patterns with SNPs in genes in the CHIEF pathway to help determine their potential functionality.

Methods: Quantitative real-time RT-PCR was run to determine gene expression of 13 genes in normal colon tissue samples from 82 individuals. TagSNP genotype data were obtained from a GoldenGate Illumina multiplex bead array platform. Age, sex, and genetic ancestry adjusted general linear models were used to estimate beta coefficients and p values.

Results: Genetic variation in mTOR (1 SNP), NFKB1 (4 SNPs), PRKAG2 (3 SNPs), and TSC2 (1 SNP) significantly influenced their expression. After adjustment for multiple comparisons several associations between pathway genes and expression of other genes were significant. These included AKT1 rs1130214 associated with expression of PDK1; NFκB1 rs13117745 and rs4648110 with STK11 expression; PRKAG2 rs6965771 with expression of NFκB1, PIK3CA, and RPS6KB2; RPS6KB1 rs80711475 with STK11 expression; STK11 rs741765 with PIK3CA and PRKAG2 expression; and TSC2 rs3087631 with AKT1, IkBκB, NFκB1, PDK1, PIK3CA, PRKAG2, and PTEN expression. The higher levels of differential expression were noted for TSC2 rs3087631 (percent difference ranges from 108% to 198% across genes). Many of these SNPs and genes also were associated with colon and rectal cancer risk.

Conclusions: Our results suggest that pathway genes may regulate expression of other genes in the pathway. The convergence of these genes in several biological pathways involved in cancer further supports their importance to the carcinogenic process.