Involvement of C677T MTHFR variant but not A1298C in methotrexate-induced toxicity in acute lymphoblastic leukemia

Methotrexate (MTX) is a key drug in acute lymphoblastic leukemia (ALL) treatment; it inhibits DNA replication by blocking the conversion of 5, 10 Methylenetetrahydrofolate to 5-methylene tetrahydrofolate by methylenetetrahydrofolate reductase (MTHFR). Variants of the Methylenetetrahydrofolate reductase (MTHFR) and MTX related toxicities were largely investigated in several populations, nevertheless, the results are conflicting.

This study aimed to assess the prevalence of MTHFR SNVs: C677>T and A1298>C in Tunisian patients with ALL and the relation to the frequency of drug-induced complications.

28 ALL patients were included in the study. They were treated according to EORTOC, in which a high dose of MTX (HDMTX) was prescribed. A toxicity score (ST) is calculated for each patient, summing the grades of toxicities. Genotyping of MTHFR variants was done with a PCR-based restriction fragment length polymorphism assay.

The toxicity's score (TS) was higher with C677T variant compared to wild genotype (C677C) (TS = 4; IC95% [-2.65-13.32] versus TS = 2.5; IC95% [1.65-4.55], respectively; p = 0.2); but lower with the A1298C mutation compared to those with the wild genotype (A1298A) (TS = 2.5; IC95% [0.48-4.77], versus TS =3; IC95% [1.9-5.69], p = 0.4). HDMTX-related toxicity is associated with the 677CT genotype in ALL patients (RR = 1.41, p = 0.2); not for the A1298C [OR = 0.46, [0.08-2.61], p = 0.18].

Our preliminary findings highlight the impact of the C677T variant of MTHFR, but not the A1289C; in HD-MTX chemotherapy-related adverse effects in younger Tunisian ALL.