Folate Levels and Polymorphisms in the Genes MTHFR, MTR, and TS in Colorectal Cancer

Abstract

AIMThe aim of the study was to explore and describe the effect of polymorphisms in folate-associated genes regarding the levels of different folate forms and their distribution in tumors and mucosa in patients with colorectal cancer.MATERIALS AND METHODSTumor and mucosa tissues from 53 patients with colorectal cancer were analyzed. The concentrations of tetrahydrofolate (THF), 5-methylTHF, and 5,10-methyleneTHF were measured by liquid chromatography—mass spectrometry. Genotyping of polymorphisms in the folate-associated genes methylenetetrahydrofolate reductase (MTHFR, C677T), methionine synthase (MTR, A2756G), and thymidylate synthase (TS, 5′-TSER 28 bp tandem repeat and 3′-TSUTR 6 bp deletion/insertion), were done by real-time polymerase chain reaction. Folate levels and distributions were determined in the total patient cohort and after subgrouping by genotypes.RESULTSThe total folate level, as well as the THF and 5,10-methyleneTHF levels, were significantly higher in the tumor compared with mucosa tissue (P = 0.030, 0.031, and 0.015, respectively). The individual variation in folate levels in both tumor and mucosa were larger than the variation found when the patients were subgrouped by the gene polymorphisms. No significant differences in the mean concentration of any folate in the mucosa or tumor tissue were found in relation to the analyzed polymorphisms. The percentage level of 5,10-methyleneTHF in tumors was highest in patients with the MTHFR 677 CC genotype, and lowest in patients with the TT genotype (P = 0.033). A significantly lower percentage level of the 5,10-methyleneTHF level was found in tumors of patients with the 5′-TSER 3R/3R genotype (P = 0.0031).CONCLUSIONA significant difference was found between the percentage level of 5,10-methyleneTHF in tumor tissues in relation to the MTHFR C677T and 5′-TSER 28 bp repeat polymorphisms. However, no differences were found in the actual tissue folate levels, or in their distribution, in relation to the polymorphisms in the MTHFR, MTR, or TS genes. These findings could be of importance for further research in the field by explaining some of the difficulties of obtaining reproducible and uniform results when using a few selected polymorphisms as predictive markers.

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Folate levels measured by LC–MS/MS in patients with colorectal cancer treated with different leucovorin dosages

“…Thus, the actual concentration of methyleneTHF, and not only of total folates, can now be measured in tissue samples. As evidenced by our recent findings, using the novel method, there is a significant variability in the folate levels in tumour and mucosa tissues between patients [ 13 ].…”

Mass Spectrometry Imaging of Therapeutics from Animal Models to Three-Dimensional Cell Cultures

“…Leucovorin or folinic acid is converted in vivo into the biologically active metabolite folate and enhances the effect of 5-fluorouracil (5-FU) in colorectal cancer. 5-FU is metabolized to the active metabolite 5-fluoro-2′-deoxyuridine 5′-monophosphate (FdUMP), binding to and inhibiting the enzyme thymidylate synthase (TS) 123 . Folinic acid is rapidly metabolized to 5, 10-methylenetetrahydrofolate (5,10-CH 2 -THF), 5, 10-methenyltetrahydrofolate (5, 10-CH=THF), and then to 5-methyltetrahydrofolate (5-MTHF) 123–124 .…”