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Frequency of single and combined genotypes of GSTM1, GSTT1 and GSTP1 in Mexican individuals: a pilot study

Background: The Glutathione S-transferase is supergene family polymorphic involved in Phase II metabolism. Participate together in the detoxification of xenobiotics. There are few reports where these set of polymorphism of GSTs genes of the same individual are studied. These polymorphisms can be used as biomarkers for predicting disease risk or response to treatment.

Objective: Determine the genotype set of each individual harbouring polymorphisms GSTT1, GSTM1 and GSTP1 in healthy volunteers of Mexican origin.

Methods: We studied 160 samples of healthy volunteers. DNA was extracted from peripheral blood. GSTT1 and GSTM1 polymorphisms were identified by multiplex end point PCR. The identification of GSTP1b (exon 5) and GSTP1c (exon 6) was performed separately by PCR-RFLP.

Results: The frequency for the GSTM1 null was 47%; GSTT1 null 65%; GSTP1 exon 5 for heterozygotes (P1a/P1b) 51.9%, 35.6% in homozygotes (P1b/P1b) and exon 6 heterozygous 25.6% (P1a/ P1c). The most common genotypes set were, wild M1; null T1; a/b P1b; a/a P1c and wild M1; null T1; b/b P1b; a/a P1c, both with a frequency of 12.5%. The null M1; null T1; a/b P1b; a/a P1c frequency was 11.9%. The highest risk genotypes were 3.8% (null M1; null T1; a/b P1b, a/c P1c) and 2.5% (null M1; null T1; b/b P1b; a/c P1c).

Conclusion: The frequencies show genotypes that can be considered high risk, indicating increased susceptibility to xenobiotics. These results are the first report of GSTM1, GSTT1 and GSTP1 combined genotype in Mexican population.

Author(s): Fernando Mejia-Sanchez, Maria G. Enríquez-Mejía, Miriam V. Flores-Merino, Antonio Laguna Camacho, Julieta Castillo-Cadena