The Impact of Autophagy on the Progression of the Myelodysplastic Syndromes

• Published in: Blood 2016-12, Vol.128 (22), p.3163-3163
• Main Authors: Vilcassim, Fathima Shahla, Banerjee, Ashish, Grigoriadis, George
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V128.22.3163.3163

Introduction About 75% of myelodysplastic syndromes (MDS) are lower risk categories with a paucity of definitive treatment and only supportive management as an option. MDS, defined by ineffective erythropoiesis produces anemia requiring frequent blood transfusions resulting in systemic iron overload. Refractory Anaemia with ring sideroblasts frequently characterised by mutations in the spliceosome machinery also contributes to cellular iron overload. Excess iron drives activation of the transcription factor NF-κB promoting pro-inflammatory cytokines production supporting tumour growth. Iron chelation is routinely used to treat transfusional iron overload. A number of observational studies have demonstrated that the iron chelator Deferasirox (DFX), improves haemoglobin levels in a subset of MDS patients (Messa, et al. 2008, Banerjee, et al. 2015). Iron metabolism is deregulated in cancer cells resulting in a net iron influx enhancing ROS production. Excess ROS promotes autophagy, a catabolic cellular recycling pathway clearing redundant and damaged organelles to sustain cellular metabolism. Autophagy is initiated by the Atg1-Atg13 protein complex and can be upregulated in cancer facilitating the propagation of the malignant clone. We have previously demonstrated that treatment with the iron chelator DFX, blocked growth of myeloid leukemia cell lines whilst sparing normal stem cells. Herein, we demonstrate that the growth inhibitory effects of DFX are mediated by its ability to inhibit autophagy. We therefore postulate that modulation of intracellular iron levels can be adopted as a viable tool to further elucidate the role of autophagy in this disease. AimsTo explore the impact of iron modulation on autophagy.To elucidate the role autophagy in myeloid cell growth and proliferation. Methods Thp-1 (myeloid cell line) expressing the autophagy reporter LC3-GFP was utilised. Autophagy results in LC3 recruitment to the autphagosomal membrane. These cells were treated with DFX in the presence/absence of chloroquine, a lysosomal enzyme inhibitor to visualise accumulated LC3-II. Cells were also treated with two other iron chelators, deferoxamine (DFO) and Dp44mT. Treated cells were then analysed using AMNIS Flow Imaging. Acute myeloid leukaemia cell lines were treated with DFX in the presence/absence of chloroquine and subjected to Western blotting using anti-LC3-II antibody. AML cell lines were also treated with 3-methyl adenine (3MA), an autophagy inhibitor. Doxyc