Department of Medical Laboratory Sciences and Technology, Division of Clinical Pharmacology, Karolinska Institutet at Huddinge University Hospital, Stockholm, Sweden and
1 Department of Medical Sciences, Clinical Pharmacology, University Hospital, Uppsala, Sweden
Dear Sir,
We read with interest the article by Martinez et al. (1) regarding a possible association between CYP2C9 genotypes leading to high enzyme activity and colorectal cancer. An important issue in this study is the selection of a control group consisting of healthy Spanish volunteers rather than patients in the same age group with benign diseases of the colon.
The same research group has reported recently the allele frequencies of CYP2C9*1, CYP2C9*2 and CYP2C9*3 as 0.695, 0.143 and 0.162, respectively, in 157 Spanish healthy volunteers as `high frequency of mutations related to impaired CYP2C9 metabolism in a Caucasian population (2)'. These figures are almost identical to those reported by Martinez et al. (1). The CYP2C9*3 variant is grossly over-represented in this Caucasian population. As a consequence of this, the frequency of CYP2C9*1 is lower than in several other Caucasian studies (35, and references therein), and not consistent with other reports as mentioned in the article. The frequencies of the CYP2C9 variant alleles in the colorectal cancer patients are very similar to those reported in healthy volunteers from other Caucasian populations (5).
In conclusion, the suggested association between the CYP2C9 genotype and colorectal cancer is based on an atypical allelic distribution in the control group of healthy volunteers, and should be interpreted with caution.
Notes
2 To whom correspondence should be addressed Email: umit.yasar{at}labtek.ki.se
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