Abstract
Busulfan (BU) is widely used in conditioning regimens prior to hematopoietic stem cell transplantation (HSCT). The exposure-escalated BU directed by therapeutic drug monitoring (TDM) is extremely necessary for the patients with high-risk hematologic malignancies in order to diminish relapse, but it increases the risk of drug-induced toxicity. BU exposure, involved in the glutathione- (GSH-) glutathione S-transferases (GSTs) pathway and proinflammatory response, is associated with clinical outcomes after HSCT. However, the expression of genes in the GSH-GSTs pathway is regulated by NF-E2-related factor 2 (Nrf2) that can also alleviate inflammation. In this study, we evaluated the influence of NRF2 polymorphisms on BU exposure, proinflammatory cytokine levels, and clinical outcomes in HSCT patients. A total of 87 Chinese adult patients receiving twice-daily intravenous BU were enrolled. Compared with the patients carrying wild genotypes, those with NRF2 -617 CA/AA genotypes showed higher plasma interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)-α levels, poorer overall survival (OS; RR = 3.91), and increased transplant-related mortality (TRM; HR = 4.17). High BU exposure [area under the concentration-time curve (AUC) > 9.27 mg/L × h)] was related to BU toxicities. Furthermore, NRF2 -617 CA/AA genotypes could significantly impact TRM (HR = 4.04; p = 0.0142) and OS (HR = 3.69; p = 0.0272) in the patients with high BU AUC. In vitro, we found that high exposure of endothelial cell (EC) to BU, in the absence of Nrf2, elicited the hyperstimulation of NF-κB-p65, accompanied with the elevated secretion of proinflammatory cytokines, and led to EC death. These results showed that NRF2 -617 CA/AA genotypes, correlated with high proinflammatory cytokine levels, could predict inferior outcomes in HSCT patients with high BU AUC. Thus, NRF2 -617 CA/AA genotyping combined with TDM would further optimize personalized BU dosing for sufficient efficacy and safety endpoint.