The -137G/C Polymorphism in Interleukin-18 Gene Promoter Contributes to Chronic Lymphocytic and Chronic Myelogenous Leukemia Risk in Turkish Patients

OBJECTIVE: Interleukin-18 (IL-18) is a cytokine that belongs to the IL-1 superfamily and is secreted by various immune and nonimmune cells. Evidence has shown that IL-18 has both anticancer and procancer effects. The aim of this study was to evaluate the relationship between IL-18 gene polymorphisms and susceptibility to chronic lymphocytic leukemias (CLL) and chronic myelogenous leukemias (CML) in Turkish patients. MATERIALS AND METHODS: The frequencies of polymorphisms (rs61667799(G/T), rs5744227(C/G), rs5744228(A/G), and rs187238(G/C)) were studied in 20 CLL patients, 30 CML patients, and 30 healthy individuals. The genotyping was performed by polymerase chain reaction and DNA sequencing analysis. RESULTS: Significant associations were detected between the IL-18 rs187238(G/C) polymorphism and chronic leukemia. A higher prevalence of the C allele was found in CML cases with respect to controls. The GC heterozygous and CC homozygous genotypes were associated with risk of CML when compared with controls. However, prevalence of the C allele was not significantly high in CLL cases with respect to controls. There was only a significant difference between the homozygous CC genotype of CLL patients and the control group; thus, it can be concluded that the CC genotype may be associated with the risk of CLL. Based on our data, there were no significant associations between the IL-18 rs61667799(G/T), rs5744227(C/G), or rs5744228(A/G) polymorphisms and CLL or CML. CONCLUSIONS: IL-18 gene promoter rs187238(G/C) polymorphism is associated with chronic leukemia in the Turkish population. However, due to the limited number of studied patients, these are preliminary results that show the association between -137G/C polymorphism and patients (CLL and CML). Further large-scale studies combined with haplotype and expression analysis are required to validate the current findings.