A case-control study of methylenetetrahydrofolate reductase polymorphisms in cervical carcinogenesis.

OBJECTIVES: Polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene are thought to be associated with a varying risk of cervical dysplasia. The purpose of this trial was to study the role of the two common functional MHTFR polymorphisms in a large multiracial population at risk for cervical dysplasia and cancer. METHODS: This is a nested case-control study of 376 subjects obtained from cohorts enrolled in an ongoing prospective cervical carcinogenesis protocol. Cases included invasive cancers (n = 51), and high (n = 50) and low (n = 50) grade dysplasia. There were 225 normal controls. Functional MTHFR 677C-->T and 1298A-->C genotypes were identified. Follow-up cytology data were reviewed for the control subjects from the time of study entry until August 2004. RESULTS: There is a significant racial difference in allele frequency of the 677C-->T polymorphism (P < 0.005). African-American women had an extremely low prevalence of the 677T allele (8%). There was no significant difference in the frequency of the 677T allele between cases and controls. There is no racial difference in allele frequency of the 1298A-->C polymorphism. Also, no significant difference was found between cases and controls. Of the 51 cancers, no case was homozygous for both aberrant polymorphisms (677T, 1298C), and only 3 cases were heterozygous for both. Follow-up data were available for 129 of 225 control subjects (57%). Only 15 (12%) have had a subsequent abnormal pap, and there was no association with the 677C-->T polymorphism. CONCLUSIONS: We confirm a significant difference in the 677T allele frequencies among racial groups. However, there is no association of either the 677C-->T or 1298A-->C polymorphisms in cervical carcinogenesis. There is no role of the combined polymorphism effect in cervical cancer or evidence of prediction for future Pap abnormalities.

Aberrant p16 methylation is a biomarker for tobacco exposure in cervical squamous cell carcinogenesis.

OBJECTIVE: The purpose of this study was to determine the association between active tobacco exposure and aberrant p16 promoter methylation in primary cervical squamous cell cancer and high-grade squamous cervical dysplasia. STUDY DESIGN: p16 methylation-specific polymerase chain reaction was performed on DNA that was extracted from 60 cervical cancers, 30 high-grade dysplasia specimens, and 78 normal cervical cytologic specimens. Patient data were obtained by medical record review or were collected prospectively. RESULTS: Aberrant p16 methylation was significantly higher in squamous cell cervical cancers (61%) than in squamous high-grade dysplasia (20%) or normal cytologic specimens (7.5%). Approximately one half the women with squamous cancer and one half of the women with high-grade dysplasia were active smokers. Aberrant p16 methylation was associated with active tobacco use in patients with squamous carcinoma (odds ratio, 20.6; 95% CI, 3.6-118; P<.001) and high-grade dysplasia (odds ratio, 4.57; 95% CI, 1.63-12.78; P=.002). CONCLUSION: Aberrant p16 methylation is associated strongly with active tobacco use in squamous cell cervical cancers and high-grade dysplasia.