Coding variants in NOD-like receptors: An association study on risk and survival of colorectal cancer

Nod-like receptors (NLRs) are important innate pattern recognition receptors and regulators of inflammation or play a role during development. We systematically analysed 41 non-synonymous single nucleotide polymorphisms (SNPs) in 21 NLR genes in a Czech discovery cohort of sporadic colorectal cancer (CRC) (1237 cases, 787 controls) for their association with CRC risk and survival. Five SNPs were found to be associated with CRC risk and eight with survival at 5% significance level. In a replication analysis using data of two large genome-wide association studies (GWASs) from Germany (DACHS: 1798 cases and 1810 controls) and Scotland (2210 cases and 9350 controls) the associations found in the Czech discovery set were not confirmed. However, expression analysis in human gut-related tissues and immune cells revealed that the NLRs associated with CRC risk or survival in the discovery set were expressed in primary human colon or rectum cells, CRC tissue and/or cell lines, providing preliminary evidence for a potential involvement of NLRs in general in CRC development and/or progression. Most interesting was the finding that the enigmatic development-related NLRP5 (also known as MATER) was not expressed in normal colon tissue but in colon cancer tissue and cell lines. Future studies may show whether regulatory variants instead of coding variants might affect the expression of NLRs and contribute to CRC risk and survival

Expression of selected CRC-associated NLRs in immune cells, primary tissue samples or CRC cell lines.

<p>mRNA expression of NLRP2 (A,B), NLRP5 (C), NLRP13 (D), NLRC5 (E) and NLRP3 (F) was determined relative to the housekeeper TBP by performing triplicate (means +SD show) qPCR using TaqMan gene-specific primers and probes on the indicated samples (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0199350#sec002" target="_blank">Methods</a>). In the case of (E) HCT cells were treated with 1000 U/ml IFNγ or 50 ng/ml S. typhimurium Flagellin for 3 or 6 hours as indicated. TBP-relative ΔCt values were normalized to a reference sample (labelled R, ΔΔCt method). N denotes samples in which no expression was detectable above Ct within 40 cycles.</p

CRC risk: genotype distribution of SNPs analyzed in the Czech case-control population for SNPs with p ≤ 0.05.

<p>Amino acid changes are given as <> with the amino acid position indicated. Data adjusted for age at diagnosis and sex. Nominal significance at p≤0.05; significance level corrected for multiple testing (39 genotyped SNPs) at p≤0.001.</p