Association of GSTP1 gene (I105V) polymorphism with acute leukaemia

Abstract

Glutathione S-transferase P1 (GSTP1) enzyme plays a key role in biotransformation and bioactivation of certain environmental pollutants such as benzo[a]pyrene-7, 8-diol-9, 10-epoxide (BPDE) and other diol epoxides of polycyclic aromatic hydrocarbons (Hengstler et al. 1998) and catalyses detoxification of base propanols that arise from DNA oxidation thus offering cellular protection against oxidative stress. GSTP1 gene belongs to the pi class gene family, located on chromosome 11q13 (Autrup 2000). It comprises of seven exons (Morrow et al. 1989; Bora et al. 1997) and codes for cytosolic GST enzyme (Fryer et al. 1986). The first polymorphism identified is an A–G polymorphism at nucleotide 313 in exon 5 of GSTP1 gene which leads to an amino acid substitution of isoleucine (IE) by valine (val) at 105 amino acid position (Ile105Val). This substitution results in three GSTP1 genotypes: they are isoleucine/isoleucine (Ile/Ile) homozygous wildtype, isoleucine/valine (Ile/Val) heterozygote and valine/valine (Val/Val) homozygous variant.GSTP1 codon 105 polymorphism might play an important role in leukaemiogenesis, as it potentially alters protein function, diminishing its detoxification ability for certain mutagens and carcinogens, which could result in increased DNA damage and mutation, and a greater risk of developing cancer. Biochemical studies indicated that GSTP1 Val105 allele has a lower thermal stability than GSTP1 Ile105 allele (Zimniak et al. 1994; Johanson et al. 1998), and Val homozygotes had a lower conjugating activity than Ile homozygotes, with heterozygotes displaying intermediate activity (Watson et al. 1998). Individuals with at least one Val allele at codon 105 of GSTP1 enzyme might have an underlying predisposition to cancer when exposed to environmentally derived