A study on the effect of IL-6 gene polymorphism on the prognosis of non-small-cell lung cancer

BACKGROUND: Lung cancer is one of the most commonly diagnosed clinical diseases. IL-6 is a multifunctional cytokine that is related to chemotactic factors and tumor biological regulation. −174G/C polymorphism in the promoter region of the IL-6 gene single-nucleotide polymorphism is the −174 position change from G to C. However, the relationship between the IL-6 gene polymorphism and prognosis of lung cancer is elusive. Therefore, the aim of this study was to evaluate the effect of −174G/C polymorphism on the prognosis of patients with non-small-cell lung cancer (NSCLC). METHODS: DNA was extracted from the peripheral blood of 434 cases diagnosed with NSCLC by cytologic or histologic examination. Polymerase chain reaction–restriction fragment length polymorphism (NlaIII) was used to detect the genotype of −174G/C. Based on the functional activity of the IL-6 gene polymorphism, genotypes were divided into G vector (CG/GG) (high yield) and CC genotype (low yield). Prognosis of patients was analyzed and independent risk factors evaluated. A quantitative analysis of the degree of pain after diagnosis was performed to evaluate the correlations between gene polymorphisms and the degree of pain and use of analgesics. RESULTS: Survival analysis showed that survival of the patients carrying the G allele (CG/GG) was significantly lower than that of patients with CC genotype (42.31 versus 62.79 months; P=0.032). The IL-6 gene promoter region revealed the presence of polymorphic variants, which may be associated with changes in the gene transcription process that affect the level of serum cytokines. IL-6 −174G/C gene polymorphism is associated with a significant morphine equivalent daily dose (IL-6 GG, 69.61; GC, 73.17; CC, 181.67; P=0.004). Homozygous IL-6 −174C/C genotype carriers required higher doses of opioids than GG or GC carriers. CONCLUSION: Polymorphism of −174G/C in IL-6 is closely related to cancer pain in NSCLC patients, the use of analgesics, and survival prognosis. It is necessary to further confirm the related results and determine the underlying pathogenic mechanisms.