Expression of pattern recognition receptor genes and mortality in patients with colorectal adenocarcinoma

Abstract

Toll-like receptors (TLRs) and the receptor for advanced glycation end products (AGER) are pattern recognition receptors that regulate intestinal inflammatory homeostasis. However, their relevance in colorectal cancer (CRC) prognosis is unclear. We investigated expression of TLRs, AGER, and interacting proteins in association with CRC mortality in a retrospective cohort study of 65 males diagnosed with primary resectable CRC between 2002 and 2009. Multiplex quantitative nuclease protection assay was used to quantify the expression of 19 genes in archived tissues of tumor and paired adjacent normal mucosa. We evaluated the association between log2 (tumor/normal) expression ratios for single and combined genes and all-cause mortality using multivariable Cox regression analysis. The false discovery rate adjusted q-value less than 0.10 indicated statistical significance for single gene. Five-year survival time was calculated from diagnosis of CRC to death, lost to follow-up, or December 31, 2014. Compared to paired normal mucosa, expression levels of AGER, IL1A, MYD88, and TLR5 were lower (q = 0.0002); while CXCL8 and S100P were higher (q = 0.0002) in tumor epithelia. Higher tumor expression of IL1A (HRadj = 0.68, 95% CI: 0.49-0.94), IL6 (HRadj = 0.70, 95% CI: 0.52-0.94), MyD88 (HRadj = 0.53, 95% CI: 0.30-0.93), and TLR5 (HRadj = 0.71, 95% CI: 0.52-0.98) was associated with higher mortality risk. There was a synergistic effect on lower five-year survival in lower co-expressers of IL-6 and MyD88 (P < 0.0001). Our findings suggest that a TLRs/MyD88-mediated inflammatory response may play a role in CRC prognosis. The role of pattern recognition receptor-mediated immunity in CRC mortality warrants further research.

Keywords: Toll-like receptors; colorectal neoplasms; gene expression; immune; inflammation; pattern recognition; receptor for advanced glycation end-products; receptors; survival; tumor microenvironment.

Figure 1

The difference between log2 gene expression (tumor-normal) in 65 paired colorectal tumor and adjacent normal tissue for 19 genes; ^aPaired T-Test; ^bMean difference or relative expression is [log2 (Diffⁱ)=log2 (Tumorⁱ)-log2 (Adjacent Normalⁱ)] Standard Deviation.

Figure 2

Kaplan Meier survival curves based on dichotomized median expression (above and below) for Log2 gene expression ratios (tumor/normal) of IL1A (A), IL6 (B), MyD88 (C), and TLR5 (D).

Figure 3

Kaplan Meier curves for combined TLR gene set analysis. Gene expression based on combined median log2 gene expression ratios for IL1A, and IL6, MyD88, and TLR5.

Figure 4

A pathway-based analysis of resulting gene set using KEGG Toll-Like Receptor Pathway information.