Correspondence 1565 S-A-W Fadilah 1,2 1 Clinical Haematology and Stem Cell S-K Cheong 1 Transplantation Services, MAKNA- H Roslan 2 HUKM Cancer Institute, Hospital M Rozie-Hanisa 1 Universiti Kebangsaan Malaysia G-K Yen 3 (HUKM), Kuala Lumpur, Malaysia; 2 Department of Medicine, Universiti Kebangsaan Malaysia (UKM), Kuala Lumpur, Malaysia; 3 Department of Medicine, Universiti Malaya (UM), Kuala Lumpur, Malaysia References 1 Orkin SH. GATA-binding transcription factors in hematopoietic cells. Blood 1992; 80: 575–581. 2 Weiss MJ, Orkin SH. GATA transcription factors: Key regulators of hematopoiesis. Exp Hematol 1995; 23: 99–107. 3 Pevny L, Simon M, Robertson E, Kelvin W, Tsai S, D’Agati V, Orkin SH, Constantini F. Erythroid differentiation in chimaeric mice blocked by a targeted mutation in the gene for transcription factor GATA-1. Nature 1991; 349: 257–260. 4 Ho PJ, Gibson J, Vincent P, Joshua D. The myelodysplastic syn- drome: diagnostic criteria and laboratory evaluation. Pathology 1993; 25: 297–304. 5 Ehrlich GD, Greenberg S, Abbort MA. A guide to methods and applications. In: Innis MA, Gelfand DH, Sninski JJ, White TJ (eds). PCR Protocols. Academic Press: California, 1990, p 325. 6 Shimamoto T, Ohyashiki JH, Ohyashiki K, Kawakubo K, Kimura N, Nakazawa S, Toyama K. GATA-1, GATA-2 and stem cell leuke- mia gene expression in acute myeloid leukemia. Leukemia 1994; 8: 1176–1180. The GSTM1 and GSTT1 genetic polymorphisms and susceptibility to acute lymphoblastic leukemia in children from north Portugal Leukemia (2002) 16, 1565–1567. DOI: 10.1038/sj/leu/2402543 TO THE EDITOR Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer accounting for approximately 25–30% of all childhood malig- nancies. 1,2 The origin of this disease can be explained by a combi- nation of genetic and environmental factors, and therefore, like many other cancers, it is considered a complex disease, caused by the ‘car- cinogenetic’ effect of the environment modified by a series of genes. Many of these genes tend to occur in allelic forms representing func- tional polymorphisms partially explaining inter-individual variability in cancer susceptibility. 1 However, chemical carcinogens are not reactive per se: they require metabolic activation before interacting with genetic material that may lead to mutations and eventually the initiation of cancer. The glutathione S-transferase mu-1 (GSTM1) and glutathione S-transferase theta-1 (GSTT1) are phase II enzymes that have the ability to detoxify numerous electrophilic compounds including the activated carcinogens. 1 Both GSTM1 and GSTT1 exhibit genetic polymorphism in populations with a large percentage of indi- viduals displaying a homozygous deletion of the structural genes. Moreover, an increased frequency of GSTT1 and GSTM1 null geno- types (either in individual or combined status) has been associated with several malignancies. Particularly concerning ALL, the studies until now performed besides being very scarce, have reported contradictory results for associations between GSTM1 and GSTT1 and cancer predisposition. Correspondence: S Alves, IPATIMUP, Rua Dr Roberto Frias s/n, 4200– 465 Porto, Portugal; Fax: 351 225570799 Received 17 December 2001; accepted 25 February 2002 Leukemia 7 Ohyashiki JH, Ohyashiki K, Kawakubo K, Tauchi T, Nakazawa S, Kimura N, Toyama K. T-cell receptor -chain rearrangement in acute myeloid leukemia always occurs at the allele that contains undermethylated J1 region. Cancer Res 1992; 52: 6598–6602. 8 Tsai SF, Martin DIK, Zon LI, D’Andrea AD, Wong GG, Orkin SH. Cloning of cDNA for the major DNA-binding protein of the erythroid lineage through expression in mammalian cells. Nature 1989; 339: 446–451. 9 Dorfman DM, Wilson DB, Bruns GAP, Orkin SH. Human tran- scription factor GATA-2: evidence for regulation of preproendo- thelin-1 gene expression in endothelial cells. J Biol Chem 1992; 267: 1279–1285. 10 Raft T, van der Giet M, Endemann D, Wiederholt T, Paul M. Design and testing of -actin primers for RT-PCR that do not co- amplify processed pseudogenes. Biotechniques 1997; 23: 456– 460. 11 Hannon R, Evans T, Felsenfeld G, Gould H. Structure and pro- moter activity of the gene for the erythroid transcription factor GATA-1. Proc Natl Acad Sci USA 1991; 88: 3004–3008. 12 Schwartzbauer G, Schlesinger K, Evans T. Interaction of the erythroid transcription factor cGATA-1 with a critical auto-regulat- ory element. Nucleic Acids Res 1992; 20: 4429–4436. 13 Weiss MJ, Keller G, Orkin SH. Novel insights into erythroid devel- opment revealed through in vitro differentiation of GATA-1 embryonic stem cells. Genes Dev 1994; 8: 1184–1197. 14 Aird WC, Parvin JD, Sharp PA, Rosenberg RD. The interaction of GATA-binding proteins and basal transcription factors with GATA box-containing core promoters. A model of tissue-specific gene expression. J Biol Chem 1994; 269: 883–889. 15 Briegel K, Lim KC, Plank C, Beug H, Engel JD, Zenke M. Ectopic expression of a conditional GATA-2/estrogen receptor chimera arrests erythroid differentiation in a hormone-dependant manner. Genes Dev 1993; 7: 1097–1109. For instance, Krajinovic et al 3 analyzing a case-control study that involved a white population of Canadians with French origin, reported a significant association between the presence of the GSTM1 null genotype and an increased risk of ALL. For GSTT1, the authors have not detected any apparent role in the etiology of ALL. However, in a previous study, Chen etal 2 have found that only the double null geno- type for GSTM1 and GSTT1 was significantly more frequent among a sample of black children with ALL from USA, although failing to show a similar association among the white children analyzed. The discrepancies can be partially explained as the result of interpopu- lational differences in genetic backgrounds of susceptibility and/or of geographical differences in environmental exposure to carcinogens. 2,3 Therefore, extensive population-specific studies are needed. For studying in north Portugal the relationship between GSTM1 and GSTT1 genotypes and risk of susceptibility to ALL, we have applied the most recently described GSTM1 and GSTT1 genotyping pro- cedures, which allow the unambiguous detection of the three geno- types that can result from deleted and non-deleted alleles. 4,5 The detection of the deletions was PCR-based using the primers described by Kerb et al 4 and Sprenger et al 5 For both GSTM1 and GSTT1, the null alleles were co-amplified with the normal ones in a single reac- tion tube, and thereafter the amplified products were electrophoresed. For GSTT1, a 1460 bp fragment corresponded to the null allele and a fragment of 540 bp to the functional one (Figure 1). For GSTM1, fragments of 8073 bp or 4748 bp indicated the presence of a func- tional allele or of a deleted allele, respectively (Figure 2). Patients enrolled in the study were 47 children with ALL, in various clinical phases, all undergoing the same chemotherapy protocol. As controls, 102 healthy subjects not following any therapeutic treatment and born in the same geographic area as patients, north Portugal, were analyzed.