A methylenetetrahydrofolate reductase polymorphism is associated with expression of p16 in human lung cancer.

Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme in the folate cycle. Reduced MTHFR activity induces DNA hypomethylation and stability, which may protect the tumor suppressor gene p16INK4. We examined the association between MTHFR polymorphism and expression of p16INK4. The frequency of the MTHFR genotypes were 21 Ala/Ala, 29 Ala/Aal, and 7 Val/Val. Expression of p16INK4 was 26.2 +/- 26.8% in the Val/Val genotype and 11.2 +/- 16.6% in the other genotypes (p=0.46) as examined by immunostaining, and excluding four specimens that were overstained. These results suggest that folate metabolism can affect carcinogenesis through the expression of p16INK4.