The association between -1304T>G polymorphism in the promoter of mitogen-activated protein kinase kinase 4 gene and the risk of cervical cancer in Chinese population

Abstract

Mitogen-activated protein kinase kinase 4 (MKK4) is a critical mediator of stress-activated protein kinase signals that regulate apoptosis, inflammations, and tumorigenesis. Several polymorphisms have been identified in the MKK4 gene. We hypothesized that genetic variants in the MKK4 promoter may alter its functions and thus cancer risk. In the current, hospital-based case-control study of 471 cervical cancer cases and 600 sex and age frequency-matched cancer-free controls in an Eastern Chinese population, we genotyped two common polymorphisms in the MKK4 promoter region (-1304T>G, rs3826392 and -1044A>T, rs3809728)c and assessed their associations with the risk of cervical cancer. We found that compared with the most common -1304TT genotype, carriers of -1304G variant genotypes had a significantly decreased risk of cervical cancer [odds ratio (OR) = 0.71; 95% confidence interval (CI) = 0.53-0.92 for TG, and OR = 0.52; 95%CI = 0.30-0.91 for GG] in an allele dose-response manner (adjusted P(trend) = 0.004). Moreover, the luciferase assay showed that the G allele in the promoter significantly increased the transcription activity of the MKK4 gene in vitro and that the MKK4 mRNA expression levels of the G variant carriers was significantly higher in tumor tissues than those of the -1304TT genotype. However, no significant association was observed between the -1044A>T polymorphism and risk of cervical cancer. Our data suggest that the functional -1304G variant in the MKK4 promoter contributes to a decreased risk of cervical cancer by increasing the promoter activity and that the G variant may be a marker for susceptibility to cervical cancer.

FIG. 1.

Transient reporter gene expression assays with constructs containing full length MKK4 promoter. (A) Schematic of reporter gene constructs having a full-length MKK4 promoter with the only difference between the four constructs being a T>G or A>T at the -1304 and -1044 polymorphic sites. (B) Luciferase expression of four constructs in HeLa and CaSKi cells co-transfected with pRL-SV40 to standardize transfection efficiency. Luciferase levels of pGL3-Basic and pRL-SV40 were determined in triplicate and standardized for transfection efficiency. Fold increase was measured by defining the activity of the empty pGL3-Basic vector as 1. Data shown are the mean fold increase 6 SD from three independent transfection experiments, each done in triplicate. MKK4, mitogen-activated protein kinase kinase 4.

FIG. 2.

MKK4 mRNA expression level in cervical cancer tissues as function of MKK4-1304T>G genotypes. Expression level among the −1304GG (n=15) genotype was significantly different from that among the TG (n=11) or TT (n=4) genotype (p=0.006).