Purpose: Many studies, including the Atherosclerosis Risk in Communities (ARIC) cohort, reported a positive association between plasma C-reactive protein (CRP)-a biomarker of low-grade chronic inflammation-and colorectal cancer risk, although it is unclear whether the association is causal. Our aims were to assess the associations of a CRP genetic risk score (CRP-GRS) created from single-nucleotide polymorphisms (SNPs) with colorectal cancer risk, as well as examine plasma CRP and CRP-GRS in relation to common cancers in the ARIC cohort.
Methods: Cox proportional hazards models were used to prospectively estimate hazard ratios (HRs) and 95 % confidence interval (95 % CI) of total, colorectal, lung, prostate, and breast cancers in relation to: (1) CRP-GRS among 8,657 Whites followed in 1987-2006 and (2) log-transformed plasma CRP among 7,603 Whites followed in 1996-2006. A weighted CRP-GRS was comprised of 20 CRP-related SNPs located in/near CRP, APOC1, HNF1A, LEPR, and 16 other genes that were identified in genome-wide association studies.
Results: After multivariable adjustment, one standard deviation increment of the CRP-GRS was associated with colorectal cancer risk (HR 1.19; 95 % CI 1.03-1.37), but not with any other cancer. One unit of log-transformed plasma CRP was associated with the risk of total, colorectal, lung, and breast cancers: HRs (95 % CIs) were 1.08 (1.01-1.15), 1.24 (1.01-1.51), 1.29 (1.08-1.54), and 1.27 (1.07-1.51), respectively. HRs remained elevated, although lost statistical significance for all but breast cancer, after excluding subjects with <2 years of follow-up.
Conclusions: The study corroborates a causative role of chronic low-grade inflammation in colorectal carcinogenesis.