| Background. C-reactive protein (CRP) and interleukin-6 (IL-6) are involved in the innate immune response. Higher CRP, a sensitive but non-specific marker for inflammation, has been associated with some cancers. It is not known whether inflammation is an underlying risk for breast cancer. Variants in the genes encoding CRP and IL-6 may influence the immune response and breast cancer risk. We investigated whether CRP was associated with breast cancer and whether CRP and IL-6 single nucleotide polymorphisms (SNPs) were associated with breast cancer and CRP.; Methods. 246 breast cancer cases and controls (CLUE I) and 108 cases and controls (CLUE II) matched on age, race, day of menstrual cycle and date of blood draw were included in the CRP and breast cancer study. Odds ratios (ORs) of breast cancer and 95% confidence intervals (CIs) were estimated from conditional logistic regression models. 316 cases and controls (CLUE II) were included in the CRP (-717T/C, +1444C/T) and IL-6 (-174G/C) SNPs and breast cancer study. ORs (95% CIs) of breast cancer were estimated from conditional logistic regression models. For the CRP and IL-6 SNPs and CRP study, geometric mean CRP (95% CIs) was estimated from linear regression models in controls.; Results. There was no association between CRP and breast cancer risk. The ORs (95% CIs) of breast cancer for the top vs. bottom fourth were CLUE I:1.10(0.66-1.81) and CLUE II:0.84(0.38-1.87). There was no association between the CRP and IL-6 SNPs and breast cancer. Compared to wildtype, the ORs (95% CIs) of breast cancer for the heterozygotes and homozygous variants were: IL-6-174G/C: 0.99(0.67-1.47),1.08(0.65-1.81); CRP+1444C/T: 0.97(0.64-1.46),1.07(0.46-2.49); and CRP-717T/C: 1.16(0.76-1.77),0.89(0.42-1.85). Women with at least one IL-6-174C and CRP-717C allele had lower CRP (2.62 vs. 3.30 mg/L, p=0.37; 2.05 vs. 3.94 mg/L, p=0.04), whereas women with the CRP+1444T allele had higher concentration (3.45 vs 2.21 mg/L, p=0.21), as compared to women with two wildtype alleles, adjusted for age.; Conclusions. These findings do not support the hypothesis that CRP and IL-6 are associated with breast cancer. Additional studies are needed to confirm these findings and to determine whether inflammation assessed using other markers plays a role in breast carcinogenesis. |
