Published in:
01-03-2014 | Letter to the Editor
Haplotype analysis of the C677T and A1298C polymorphisms of MTHFR and susceptibility to chronic myeloid leukemia
Published in: Medical Oncology | Issue 3/2014
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I have read with great interest the recent study by Khorshied et al. [1], which has been published in the Medical Oncology. The authors investigated the possible association between genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR; EC: 1.5.1.20; OMIM: 607093) at nucleotides 677 (C677T, rs.1801133) and 1298 (A1298C, rs.1801131) and the risk of chronic myeloid leukemia (CML) in an Egyptian sample. The authors included 97 CML patients and 130 age- and gender-matched healthy controls in their study. They found that there is no significant association between these polymorphisms and the susceptibility to CML. I would like to make a few comments about the study.
1.
A mistake was observed in the Table 1 the above mentioned article. The numbers of the “A” and “C” alleles of the C677T polymorphism among control group should be 175 and 85, respectively.
Table 1
Haplotype frequencies of the C677T and A1298C polymorphisms of MTHFR in chronic myeloid leukemia patients and healthy control subjects
|
Haplotypes
|
Controls
|
Cases
|
χ 2 (df = 1)
|
P value
|
|---|---|---|---|---|
|
677C–1298A
|
0.4880
|
0.5212
|
0.42
|
0.482
|
|
677T–1298A
|
0.1850
|
0.2262
|
1.16
|
0.279
|
|
677C–1298C
|
0.2120
|
0.1334
|
4.68
|
0.030
|
|
677T–1298C
|
0.1150
|
0.1191
|
0.02
|
0.893
|
2.
The “STrengthening the REporting of Genetic Association (STREGA) studies” statement strongly recommended that authors of genetic studies state linkage disequilibrium (for linked polymorphic sites) [2].
3.
The authors tried to perform haplotype analysis of the two polymorphisms of the MTHFR. However, based on the data presented in the Table 2 of the above mentioned study, the analysis is not the haplotype analysis. Actually, the authors investigated the genotype combinations of the polymorphisms.
4.
The close physical proximity of the C677T and A1298C polymorphisms of MTHFR should place them in linkage disequilibrium. I used the software SNPAlyze(TM) version 6 Standard (Dynacom Co, Ltd. Kanagawa, Japan) to evaluate the status of pairwise linkage disequilibrium for the polymorphisms. Based on the complete dataset, according to data presented in the Table 2 of Khorshied and his coauthors study [1], the C677T and A1298C polymorphic sites showed significant linkage disequilibrium in patient group (D′ = 0.1929, r 2 = 0.0238, χ 2 = 4.46, P = 0.034). However, there was no significant linkage disequilibrium in the control group (D′ = 0.0837, r 2 = 6.17 × 10−3, χ 2 = 1.68, P = 0.194). It might be interpreted by the genetic structure of the Egyptian population. Considering that I am not familiar with the genetic structure of Egyptian population, I have no interpretation for any linkage disequilibrium in the controls.