Benzene-induced hematotoxicity enhances the self-renewal ability of HSPCs in Mll-Af9 mice

Patients with benzene-induced leukemia undergo a continuous transformation from myelosuppression to malignant proliferation. However, the underlying mechanisms in this process remain unknown. Our previous studies have shown that the pathways involved in self-renewal capacity of bone marrow (BM) cells in Mll-Af9 mice exposed to benzene for life are significantly activated after severe blood toxicity. In order to investigate the hematotoxicity effects of benzene on the self-renewal capacity of HSCs, Mll-Af9 chimeric mice were exposed to benzene and hematological parameters were dynamically monitored after benzene exposure. Transcriptomic analysis were used to analyze different time points during benzene exposure and after competitive bone marrow transplantation (BMT). Results showed that despite severe hematotoxicity in mice, but the chimerism rate of Mll-Af9 cells in peripheral blood (PB) cells was significantly increased after 10 weeks benzene exposure (P < 0.001). After competitive BMT, the chimerism rate of Mll-Af9 cells from 10 weeks benzene-exposed mice was gradually increased and significantly surpassed that of the control at 26 weeks of bone marrow reconstruction (benzene group 86 % VS control group 78 %, P = 0.03). Transcriptome analysis revealed that the expression levels of self-renewal related genes, such as Hox genes (Hoxb4, Hoxa7, Hoxa10), Mecom and Ms4a in BM cells of 10 weeks benzene-exposed mice were relatively higher compared to those in the control group, but no significant difference were observed. Interestingly, Hoxa7, Hoxa10 and Mecom were significantly up-regulated at 26 weeks after bone marrow transplantation. In conclusion, our study suggests that abnormal expression of self-renewal-related genes may be potential early biomarkers for benzene-induced hematotoxicity. This hematotoxicity may contribute to the acquisition of evolutionary advantages by leukemic precursor cells and accelerate malignant transformation.