The RFC1 80G>A, among Common One-Carbon Polymorphisms, Relates to Survival Rate According to DNA Global Methylation in Primary Liver Cancers

Abstract

Polymorphisms within one-carbon metabolism genes have been largely studied in relation to cancer risk for the function of this pathway in nucleotide synthesis and DNA methylation. Aims of this study were to explore the possible link among several common functional gene polymorphisms within one-carbon metabolism and survival rate in primary liver cancers, i.e., hepatocellular carcinoma and cholangiocarcinoma, and to assess the additional effect of global DNA methylation on survival rate and mortality risk. Forty-seven primary liver cancer patients were genotyped for ten polymorphisms: DHFR 19bp ins/del, TS 2rpt-3rpt, MTHFD1 1958G>A, MTHFR 677C>T, MTR 2756A>G, MTRR 66A>G, RFC1 80G>A, SHMT1 1420C>T, BHMT 716 A>G, TC II 776C>G. Methylation was determined in peripheral blood mononuclear cells (PBMCs) DNA as methylcytosine (mCyt) content using LC/MS/MS. Among the polymorphisms analysed, the RFC1 80G>A (rs1051266) influenced the survival rate in primary liver cancers. The RFC1 80AA was associated to a significantly reduced survival rate (22.2%) as compared to both GG and GA genotypes (61.5% and 76% respectively, p = 0.005). When the cancer patients were stratified according to the mCyt median value as high (>5.34%) or low (≤5.34%), the concomitant presence of AA genotype and low mCyt level led to a significantly worse survival rate as compared to the G allele carriership (p<0.0001) with a higher Hazard Ratio (HR = 6.62, p = 0.001). The subjects carrying the AA genotype in association with high mCyt did not show a significant difference in survival rate as compared with the G allele carriers (p = 0.919). The RFC1 80G>A polymorphism influenced the survival rate, and the presence of RFC1 80AA genotype with low global methylation in PBMCs DNA was associated with poorer prognosis and higher mortality risk, therefore highlighting novel molecular signatures potentially helpful to define prognostic markers for primary liver cancers.

One-carbon genetic variants and the role of MTHFD1 1958G>A in liver and colon cancer risk according to global DNA methylation

“…When global DNA methylation was analysed according to MTHFD1 1958G>A genotypes, the 1958GG genotype was either significantly more represented in patients affected by cancer, and associated with lower mCyt levels in PBMCs DNA. These results are in agreement with the previous observation of global DNA hypomethylation in cancer tissues [ 6 , 12 , 13 ] as well as in PBMCs DNA of patients affected by cancer [ 8 ]. In the subgroup of patients affected by colon cancer, the association between the presence of MTHFD1 1958GG genotype and DNA hypomethylation in PBMCs did not reach statistical significance probably due to the small sample size.…”

“…One-carbon metabolism is an essential crossroad in the balance between nucleotide synthesis and methylation reactions including that of DNA, known to be a key epigenetic mechanism in carcinogenesis [ 2 , 12 , 13 ]. Moreover, functional genetic variants of genes pertaining to one-carbon pathway are considered as potential risk factors for cancer disease ( Fig 1 ) [ 5 , 29 ].…”

“…Moreover, functional genetic variants of genes pertaining to one-carbon pathway are considered as potential risk factors for cancer disease ( Fig 1 ) [ 5 , 29 ]. Few data are available, so far concerning the mechanisms underlying the role of one-carbon metabolism variants in affecting cancer risk through the modulation of DNA methylation [ 8 , 12 , 13 ]. The MTHFD1 enzyme catalyzes three sequential and reversible reactions in the pathway of conversion of tetrahydrofolate (THF), the active form of folate, into substrates essential for the de novo purine and thymidylate synthesis [ 30 ] ( Fig 5 ).…”

“…There is evidence that global DNA hypomethylation in peripheral blood mononuclear cells (PBMCs) may be associated to an increased cancer risk and may be useful as a biomarker for cancer susceptibility [ 11 ]. Significantly reduced methylcytosine (mCyt) levels in PBMCs DNA from cancer patients were previously observed [ 8 , 12 , 13 ], where low levels of global DNA methylation was related to future cancer development and therefore might be considered as a potentially useful epigenetic marker for cancer risk [ 8 ]. Cancer is a major public health issue [ 14 ].…”