Influence of oxidation resistance 1 on disease progression in chronic myeloid leukemia
Weiqi Huang, Bin Liu, Liping Hu, Chi-Hao Luan, Priyam Patel, Elizabeth Bartom, Elizabeth A. Eklund
Weiqi Huang, Bin Liu, Liping Hu, Chi-Hao Luan, Priyam Patel, Elizabeth Bartom, Elizabeth A. Eklund
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Research Article Hematology Oncology

Influence of oxidation resistance 1 on disease progression in chronic myeloid leukemia

Abstract

Survival in chronic myeloid leukemia (CML) was dramatically improved by development of tyrosine kinase inhibitors (TKIs) directed to the BCR:ABL1 oncogene. Unfortunately, ~30% of patients with CML develop TKI resistance during prolonged treatment, with enhanced blast crisis risk. Oxidation Resistance 1 (Oxr1) regulates antioxidant pathways that detoxify reactive oxygen species (ROS) generated by the phagocyte-NADPH oxidase. In the current studies, we found that Oxr1 expression increased in hematopoietic stem and progenitor cells (HSPCs) from CML mice versus controls, decreased during TKI-induced remission, and rose during chronic phase relapse. Oxr1 has long and short isoforms, and we found increased short, but decreased long, Oxr1 in mice or humans during CML relapse. We determined that long Oxr1 prevents ROS accumulation in CML marrow, but short Oxr1 is a dominant negative. Previously, we found exaggerated and sustained emergency granulopoiesis in CML mice, with repeated episodes facilitating relapse during TKI remission. In the current studies, we found knocking down Oxr1 in murine marrow further accelerated CML progression during this physiologic stress. We found increased DNA-damage in HSPCs from these mice, including a BCR:ABL1 kinase-domain mutation found in TKI-resistant human CML. These studies suggest that long Oxr1 detoxifies ROS to decrease mutagenesis in CML, but aberrant short Oxr1 expression enhances progression.

Authors

Weiqi Huang, Bin Liu, Liping Hu, Chi-Hao Luan, Priyam Patel, Elizabeth Bartom, Elizabeth A. Eklund

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Figure 5

Oxr1-knockdown in CML bone marrow enhances intracellular ROS and DNA damage.

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Oxr1-knockdown in CML bone marrow enhances intracellular ROS and DNA dam...
(A) Recipients of BCR:ABL1 transduced marrow were sacrificed in CP, and marrow transduced with vectors to express shRNAs to total Oxr1, the long Oxr1 isoform, scrambled controls, or to overexpress short Oxr1. Transduced marrow was transplanted into secondary recipients. Secondary recipients in TKI-induced remission were treated with Alum to induce emergency granulopoiesis, or saline steady state control, and sacrificed 2 weeks later. (B) CML mice have increased total cellular and mitochondrial ROS, and DNA damage during emergency granulopoiesis compared with non-CML mice, and this increases further with CP relapse. GFP+LSK cells were analyzed by flow cytometry. Significant differences were found by 1-way ANOVA with Tukey correction. *P < 0.05, **P < 0.01, ***P < 0.001, or ****P < 0.0001. Data are shown as mean ± SD, n = 3 and a representative histogram is shown. (C) Total Oxr1-knockdown, long Oxr1 knockdown, or short Oxr1 overexpression increases total intracellular and mitochondrial ROS and DNA damage during emergency granulopoiesis in CML mice, but long Oxr1 knockdown has the greatest effect. GFP+LSK cells were analyzed by flow cytometry. Significant differences were found by 1-way ANOVA. *P < 0.05, **P < 0.01 or ****P < 0.0001. Data are shown as mean ± SD, n = 3 and a representative histogram is shown. (D) Oxr1 long versus short isoform expression in these cells was verified. Western blots of GFP+Lin– marrow cells were probed with Oxr1 or GAPDH (loading control) antibody and densitometry performed (experiment was repeated 3 times and a representative blot shown).