MTHFR and TYMS genotypes influence TPMT activity and its differential modulation in males and females

ObjectivesTPMT catalyzes the deactivation of the cytostatic drug 6-mercaptopurine used in treatment of cancer. Patients with low levels of TPMT more often experience severe toxic effects when treated with standard doses of 6-mercaptopurine than patients with high levels who, in turn, may experience inadequate treatment. It is therefore very important to assess factors that could influence TPMT activity.Design and methodsRed blood cell TPMT activity was measured by means of HPLC and genotypes of 86 healthy individuals were analyzed using TaqMan and PCR-RFLP methods, in order to investigate the effect of TPMT, MTHFR and TYMS genotypes on TPMT activity.ResultsTPMT activity was higher in TPMT wild-type males than females (p = 0.028). Three-way ANOVA interaction analysis revealed a significant interaction effect between MTHFR genotype and gender on TPMT activity (p = 0.023).ConclusionMales have higher TPMT activity than females and the trend of influence of MTHFR genotype on TPMT activity is different in the two gender groups.