Frequencies of Xenobiotic-Metabolizing Enzyme Gene Polymorphisms CYP3A4, GSTM1 and GSTT1 in a Filipino Population
Roldan M. De Guia, Ariana Anne P. Baluyot, Emmanuel Austin A. Banzon Jr., Marice R. Bernal, Ralph Rayman B. Bio, Carlo Antonio G. Boado, Ma. Elena J. Manansala and Jovencio G. Apostol
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The inter-patient differences in drug response is documented to be attributable to heritable genetic variations in
the nucleotide sequence of drug-metabolizing enzymes. The identification of variant allele frequencies in specific ethnic
groups is important to individualize drug dosing and improve therapeutics. This study aimed to detect single-nucleotide
polymorphism (SNP) in CYP3A4 and the homozygous deletion (0/0) of GSTM1 and GSTT1 in a Filipino population. Onehundred
and forty-two Filipino subjects were genotyped for the CYP3A4*18 SNP using PCR-RFLP and the GSTM1 0/0
and GSTT1 0/0 by basic PCR followed by agarose gel electrophoresis. In the study population, the frequency of the
CYP3A4*18 variant allele was found to be 2.11%. The percentage of GSTM1 0/0 observed was 64.08 while that of GSTT1
0/0 was 48.59. These frequencies complement studies in other Asian populations highlighting the importance of the
screening for future prospects of individualized medicines.
CYP3A4*18, GSTM1, GSTT1, gene polymorphisms, drug metabolism.
Joint Research Division: Molecular Metabolic Control (A170) German Cancer Research Center (DKFZ), Center for Molecular Biology (ZMBH) University of Heidelberg and Heidelberg University Hospital, Im Neuenheimer Feld 280 69120 Heidelberg, Germany.