ABSTRACT
Title
Investigation on MTHFR, DYPD and TSER polymorphisms in 5-Fluorouracil toxicity: a case report
Authors
A. Scalvini 1, S. Bodei2, V. Ferrari 1, G. Arcangeli 1, F. Consoli 1, P.F. Spano 2, S. Sigala 2
1 Division of Oncology, A.O. Spedali Civili, P.le Spedali Civili 1, Brescia, 2 Section of Pharmacology, University of Brescia Medical School, V.le Europa 11, Brescia.
1 Division of Oncology, A.O. Spedali Civili, P.le Spedali Civili 1, Brescia, 2 Section of Pharmacology, University of Brescia Medical School, V.le Europa 11, Brescia.
Abstract
Introduction.5-Fluorouracil (5-FU) is a chemotherapic drug belonging to the fluoropyrimidine family, broadly used either alone or in combination with other agents. 5-FU indications include palliative and adjuvant treatment of many cancers, including colorectal, breast, head and neck cancers. 5-FU requires enzymatic conversion to the nucleotide floxouridine monophosphate (FdUMP) in order to exert its cytotoxic activity. The interaction between the FdUMP and the thymidylate synthase (TS) blocks the synthesis of thymidine triphosphate. The folate cofactor 5-10 methylenetetrahydrofolate (MTHF) and FdUMP form a covalently bound complex with TS. It should be underline that the MTHF intracellular levels are regulated by the enzyme MTHFR (MethyleneTetraHydroFolate Reductase). Enzymes involved in the 5-FU mechanism of action as well as those involved in its metabolism have shown polymorphisms at the genetic level, that influence the structure and function of the encoded protein. Based on this, it has been suggested that the presence of polymorphisms could be one of the reason for the significant interindividual variability in the safety profile reported in patients undergoing 5-FU therapy. Thus, the knowledge of the 5-FU-related pharmacogenomic profile may help to predict the response outcome and the chemotherapy toxicity in patients treated with this drug. In this work, we described a case report of two patients with relevant systemic toxicity following 5-FU therapy. The 5-FU related pharmacogenomic profile revealed polymorphisms in the target genes that may explain the clinical findings.
Patients and Methods.Informed written consent was obtained from the two patients who experienced acute toxicity following 5-FU administration. An aliquot of routinarly collected peripheral blood was used for DNA extraction. Genomic DNA was extracted using the Qiagen Blood & Cell Culture DNA kit(Qiagen, Milano, Italy) . The 5-FU pharmacogenomic profile was performed with the “fluoropyrimidines response” kit (Diatech, Jesi, AN, Italy) that evaluate the following genetic markers: MTHFR C677T, MTHFR A1298C, DPYD (DihydroPYrimidine Dehydrogenase) and TSER (Thymidylate Synthase Promoter)28bp VNTR.
Results and Discussion.The systemic toxicity of the two patients was incoercible vomiting, epatotoxicity and paresthesias in one patient; while the other developed G4 mucositis and pancytopenia. The genetic analysis revealed that one patient presented 1) heterozygosity (C/T) at MTHFR C677T gene marker and heterozygosity (A/C) at MTHFR A1298C, both associated with a reduced enzyme activity resulting in increased homocysteine levels and altered distribution of intracellular folate; 2) mutation (2R/2R) at TSER 28bp VNTR, associated with an significant increase in the incidence of adverse events in a fluoropyrimidines-based therapy. The DPYP profile was wild-type (G/G).
The other patient showed 1) heterozygosity (A/C) at MTHFR A1298C and 2) heterozygosity (2R/3R) at TSER 28bp VNTR gene marker,. This latter polymorphism is associated with an increased enzyme expression and activity. Analysis of the other genetic markers (MTHFR C677T; DPYD) revealed a wild-type genotype.
Conclusion. The prediction of response or toxicity and therapy individualization are becoming very important tools in cancer chemotherapy. There have been, indeed, numerous studies on the relationship between genotypes and the response to chemotherapeutic agents. Potentially useful pharmacogenomic markers of the response to chemotherapeutic agents are now available. Here we reported two patients with severe systemic toxicity following 5-FU therapy, that may be linked to polymorphisms found in the MTHFR and TSER genes, whit a wild-type expression of the metabolizing enzyme DPYD.
Patients and Methods.Informed written consent was obtained from the two patients who experienced acute toxicity following 5-FU administration. An aliquot of routinarly collected peripheral blood was used for DNA extraction. Genomic DNA was extracted using the Qiagen Blood & Cell Culture DNA kit(Qiagen, Milano, Italy) . The 5-FU pharmacogenomic profile was performed with the “fluoropyrimidines response” kit (Diatech, Jesi, AN, Italy) that evaluate the following genetic markers: MTHFR C677T, MTHFR A1298C, DPYD (DihydroPYrimidine Dehydrogenase) and TSER (Thymidylate Synthase Promoter)28bp VNTR.
Results and Discussion.The systemic toxicity of the two patients was incoercible vomiting, epatotoxicity and paresthesias in one patient; while the other developed G4 mucositis and pancytopenia. The genetic analysis revealed that one patient presented 1) heterozygosity (C/T) at MTHFR C677T gene marker and heterozygosity (A/C) at MTHFR A1298C, both associated with a reduced enzyme activity resulting in increased homocysteine levels and altered distribution of intracellular folate; 2) mutation (2R/2R) at TSER 28bp VNTR, associated with an significant increase in the incidence of adverse events in a fluoropyrimidines-based therapy. The DPYP profile was wild-type (G/G).
The other patient showed 1) heterozygosity (A/C) at MTHFR A1298C and 2) heterozygosity (2R/3R) at TSER 28bp VNTR gene marker,. This latter polymorphism is associated with an increased enzyme expression and activity. Analysis of the other genetic markers (MTHFR C677T; DPYD) revealed a wild-type genotype.
Conclusion. The prediction of response or toxicity and therapy individualization are becoming very important tools in cancer chemotherapy. There have been, indeed, numerous studies on the relationship between genotypes and the response to chemotherapeutic agents. Potentially useful pharmacogenomic markers of the response to chemotherapeutic agents are now available. Here we reported two patients with severe systemic toxicity following 5-FU therapy, that may be linked to polymorphisms found in the MTHFR and TSER genes, whit a wild-type expression of the metabolizing enzyme DPYD.