We also replicated associations with rs4148737 in the ATP-binding cassette subfamily B member 1 (ABCB1) gene (discovery: HR = 2.96, 95% CI = 1.08-8.10, P = 0.034; replication: HR = 1.60, 95% CI = 1.05-2.44, P = 0.029), which we have previously found to be associated with poorer OS in pediatric osteosarcoma patients, and rs11188147 in cytochrome P450 family 2 subfamily C member 8 gene (CYP2C8) (discovery : HR = 2.49, 95% CI = 1.06-5.87, P = 0.037; replication: HR = 1.77, 95% CI = 1.06-2.96, P = 0.030), an enzyme involved in the oxidative metabolism of the ES chemotherapeutic agents cyclophosphamide and ifosfamide.
Overexpression of HER2 was present in 32% of OS and 16% of ES and was significantly associated with the increased expression of P-glycoprotein, a surface molecule responsible for multidrug resistance.