There is still a strong need for new treatment strategies that will maintain remission and prolong survival in patients with acute lymphoblastic leukemia (ALL). The glutathione-S-transferase (GST) enzymes, which are coded by highly polymorphic genes, have been associated with the risk of developing cancer and were found to regulate effect of cancer treatment drugs.
OBJECTIVES: The present study determines the association of GSTM1, GSTP1 and GSTT1 polymorphisms and treatment response in terms of occurrence of adverse events and relapse in ALL in Filipino children.
METHODS: This is a follow up study on the 2007 investigation done by Alcausin et al. which determined the association of the GST P1, M1, and T1 polymorphisms and occurrence of ALL. Four-year follow-up data were available for 46 out of the 50 patients from January 2007 to May 2011. Odds ratios (OR) as measures of association of GST M1, P1 and T1 gene polymorphisms with treatment outcomes were estimated at 95% confidence interval.
RESULTS: Results show a trend towards predisposition to elevation of liver enzymes in patients with GSTT1 and GSTP1 mutant genotypes showing an OR (95% Cl) of 2.0 (0.62-6.49). The presence of GSTM1 null genotype showed a trend towards protection from occurrence of relapse basing on both crude and adjusted ORs, 0.58 (0.16-2.07) and 0.23 (0.05-1.20), respectively. However, these results are not statistically significant.
CONCLUSION: The GSTP1 heterozygous genotype conferred increased predisposition to elevation of liver enzymes while the GSTT1 null genotype was shown to be a possible risk factor towards the occurrence of both infection and elevation of liver enzymes during chemotherapy. Furthermore, the GSTM1 null genotype appears to be protective from occurrence of relapse. It is recommended to do similar large-scale studies in the future to obtain more conclusive results.