Genotypic and Haplotype Analysis of Interleukin-6 and-18 Gene Polymorphisms in Association with Clinicopathological Factors in Breast Cancer

Background: Cytokines are multifunctional glycoproteins playing a vital role in the tumor microenvironment and in the progression of breast cancer. The immune responses in the tumors restrained by pro- and anti-inflammatory cytokine expressions could be influenced by genetic polymorphisms. Hence, the present study evaluated the contribution of IL6 (rs1800797, rs1800796, and rs1800795), and IL18 (rs1946518, rs187238, and rs549908) genotypes and its haplotypes with risk and progression of breast cancer in south Indian population. Methods: The polymorphisms of IL6 gene -597G>A, -572G>C, -174G>C and IL18 gene -607C>A, -137G>C, and 105A>T were genotyped through PCR-RFLP and As-PCR assays in blood DNA of 600 subjects. We have performed haplotype, LD, univariate, multivariate logistic regression and Kaplan-Meier analyses for the obtained data. Results: The frequency of AA genotype & A-allele of IL6 -597G>A, and CC genotype & C allele of IL6 -174G>C polymorphism was higher in breast cancer patients and was found to be significantly associated with TNM staging, late (advanced) stage, metastasis, etc. While, CG and GG genotypes of IL6 -572 C>G polymorphism had a protective role against breast cancer. Further, IL18 -607C>A, -137G>C & 105A>T polymorphisms were found to be associated with lobular carcinoma subtype, PR-ve and HER2+ve breast cancer patients. Perfect LD was observed between all SNPs of IL6 & IL18 genes under study; G-C-C, A-G-G and A-C-C haplotype combination of IL6 genes had conferred 2.09, 2.25 and 4.72 folds risk for breast cancer respectively. In survival analysis, we observed that the C allele of rs 1800795 was found to be significantly associated with 5years overall survival in breast cancer subjects. Conclusions: Overall, our results suggest the importance of genotypic and haplotype analysis of IL6, and IL18 gene variants in progression and risk identification of breast cancer.