Treatment of MDS patients with recombinant human erythropoietin and the role of GSTs.

Glutathione S-transferases (GSTs) are a group of enzymes involved in the detoxification process of carcinogens and other substances. The genes encoding isoenzymes M1 and T1 have "null" alleles, which are polymorphic in humans. Our purpose was to examine whether the GSTM1 and GSTT1 homozygous null genotypes have an impact on the response to recombinant human erythropoietin (rhuEpo) treatment in MDS patients. We analyzed lymphocyte DNA samples from 27 patients with all types of myelodysplastic syndromes (MDS) at the time of diagnosis. All patients were scheduled to receive rHuEpo in doses of 150 u/Kg/day for a period of 12 weeks in order to obtain and maintain stable responses. A multiplex polymerase chain reaction (PCR) was used to genotype both GSTM1 and GSTT1 simultaneously, in responders and non-responders to rhuEpo with respect to various pretreatment parameters: haemoglobin, white blood cell count, platelets, serum erythropoietin, transfusion requirements and bone marrow blasts. The data obtained were evaluated by chi2 test and odds ratio were extracted. Twelve out of 27 evaluated patients demonstrated an erythroid response (44%). Nine out of the 12 patients (75%) responding after 12 weeks of treatment had GSTM1 null genotype (OR=3.4). In contrast, only 1 responder (8.3%) was homozygotes of GSTT1 null genotype. Furthermore, no statistically significant difference in the response rate of the different MDS subgroups was observed. Our results suggest that a treatment with rHuEpo may be effective in achieving a stable erythroid response in MDS patients who carry an homozygous deletion of the GSTM1 gene.

Increased prevalence of GSTM(1) null genotype in patients with myelodysplastic syndrome: a case-control study.

BACKGROUND AND OBJECTIVE: Myelodysplastic syndromes (MDS) are clonal disorders of bone marrow stem cells characterized by ineffective hematopoiesis leading to blood cytopenia; they often progress to acute myeloid leukemia (AML). The glutathione S-transferases (GST) detoxify various agents, including those implicated in MDS. Both GSTM(1) and GSTT(1) genes have "null" alleles and are polymorphic. We studied the impact of GTM(1) and GSTT(1) null genotypes on the MDS susceptibility, disease severity and laboratory indices with prognostic value for the syndrome. MATERIAL AND METHODS: In a hospital-based case-control study we analyzed lymphocyte DNA samples from 54 patients with MDS and 60 cancer-free controls matched for age, sex, smoking habits and origin. A multiplex polymerase chain reaction was used to genotype both GSTM(1) and GSTT(1) simultaneously. The chi(2) test was used for statistical evaluation of the data and the odds ratios and attributable risk and population attributable risk were also calculated. RESULTS: A significantly increased frequency of GSTM(1) null genotype was found among MDS patients (57.4%) compared to controls (33.3%) (p < 0.01), while the frequency of GSTT(1) null genotype was not significantly higher in MDS patients (11.1% vs. 6.66%). Neither GSTM(1) and GSTT(1) null genotype was associated with a particular category of the French-American-British (FAB) classification in the patients studied. Additionally, GSTM(1) null genotype was associated with a significant decrease in the absolute number of neutrophils among the MDS patients. CONCLUSIONS: Individuals with GSTM(1) null genotype may have increased susceptibility to MDS. Null genotypes do not seem to have be associated with FAB classification while they may be associated with putative prognostic factors.