Prognostic value of methlylenetetrahydrofolate reductase (MTHFR), thymidylate synthase (TS) promoter, and p53 codon 72 variants and survival in advanced non-small cell lung cancer (NSCLC).

Background: Folate plays an important role as a cofactor of enzymes involved in DNA synthesis and in the regulation of gene expression through methylation. Hypometylation of the p53 tumor suppressor gene has been described in folate depletion. p53 codon 72 polymorphism influencing the function of the protein is thought to be linked with an increased risk of lung cancer. Since MTHFR 677 and 1298 SNP and TS promoter polymorphisms are involved in folate metabolism, DNA methylation and DNA repair we tested their expression and interaction with p53 codon72 polymorphism in patients (pts) with locally advanced and metastatic NSCLC and compared with patients’overall survival (OS). Methods: Genomic DNA was isolated from peripheral blood lymphocytes of 50 pts, using Puregene Genomic DNA Purification System. Pts (36 M/14 F) median age was 61.5 (range 45-84).Median OS was 21,2 months. Genotyping for MTHFR polymorphism was carried out by DG-DGGE(double gradient-denaturing gradient gel electrophoresis), for p53 codon 72 (Arg/Pro) with the use of fluorogenic allele-specific oligonucleotide TaqMan probes on a 7900HT Fast Real-Time PCR System and for TS Promoter Polymorphisms with PCR and subsequent electrophoresis on 3% agarose gel. Products of 214 bp, 242 bp, or both, depending on the TS promoter genotype, were observed. TS tandem repeats and SNPs were combined. Patient’s overall survival were compared with MTHFR, TS and/or p53 codon 72.A multivariate analysis was performed. Results: We have recorded no significant correlations between survival data and the expression of MTHFR 677 and 1298 SNPs, TS tandem repeats, and p53 codon 72 polymorphisms, considered separately. However, the combined MTHFR CT677/AC1298 genotype was significantly associated with longer survival (34,5 months p<0,05) also in association of TS genotype homozygous for triple repeats (3R/3R), (29,5 months p<0,05). Conclusions: Although preliminary, these data support the role of MTHFR and TS genotypes as prognostic marker in NSCLC patients, where gene-gene interactions between the genotypes may occur. Further studies are needed to confirm these findings.