Role of glutathione S-transferase and cytochrome P-450 polymorphisms in the clinical outcome of osteosarcoma patients.

Abstract

10535 Background: Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents. Glutathione S-transferase (GST) and Cytochrome P-450 (CYP) family genes are involved in almost all anticancer drugs metabolism. The polymorphisms in these genes are associated with anticancer drugs resistance and toxicity events. This study aims to investigate the genotype frequencies of GSTM1, GSTT1, GSTM3, CYP1A2, CYP2C9 and CYP3A5 genes in OS patients and the influence of these polymorphisms in their clinical outcome. Methods: We investigated the peripheral blood DNA of 70 OS patients (25 metastatic and 45 nonmetastatic at diagnosis), following the GLATO - Latin American Group of Osteosarcoma Treatment - 2006. GSTM1 and GSTT1 deletion polymorphisms were examined through a multiplex-PCR and the GSTM3 polymorphism of three base pair-deletion using PCR-RFLP method. CYP1A2, CYP2C9 and CYP3A5 single nucleotide polymorphisms (SNPs) were investigated through real time PCR using TaqMan probe. Results: We found that GSTM1 null genotype was correlated with relapse occurrence (p=0,031) in patients that received high doses of chemotherapy. The CYP1A2*F allele was associated with lung metastasis (p=0,032), lung relapse (p=0,018) and high grade of ototoxicity (p=0,039). The CYP3A5*3 allele was associated with high grade of hepatotoxicity (p=0,010). The presence of at least one GSTM3*B allele was associated with better overall survival (p=0,045). The presence of CYP3A5*3 homozygous genotype was associated with better overall survival (p=0,043) in metastatic patients at diagnosis. The genotype GSTM3*B/ GSTM1 present, GSTM3*B/ GSTT1 present and GSTM3*B/CYP3A5*3 in metastatic patients at diagnosis were associated with better survival (p=0,048; p=0,004; p=0,012, respectively). Conclusions: The findings of this study suggest that GST and CYP polymorphisms may have a role in treatment response and may be an important marker in the future to personalized therapy in OS. Furthermore, CYP1A2*F allele is correlated with risk of lung metastasis and GSTM3*B homozygous genotype in combination with GSTM1 present, GSTT1 present and CYP3A5*3 were associated with better survival.