Session: 102. Iron Homeostasis and Biology: Poster III
Hematology Disease Topics & Pathways:
Research, Translational Research
Methods and Results: Using an established protocol to evaluate bone marrow erythroblast differentiation in mice [Liu et al. 2013], we demonstrate that early stage erythroblast depletion occurs 24 hours following camonsertib treatment. This effect is reversible with erythroblast regeneration occurring 2-4 days after treatment is halted. Using an established in vitro protocol for human CD34+ cell differentiation to erythroblasts [Hu et al. 2013], we show that ROS concentration is highest in early-stage erythroblasts (P = 0.002). Next, we demonstrate altered transcripts levels for iron-related genes in erythroblasts with increased ferritin (FTH (P = 0.02) and FTL (P = 0.04)), PCBP1 (P = 0.02), and NCOA4 (P = 0.06) and decreased TFRC (P = 0.06) occur during in vitro erythroblast differentiation (n=5 experiments), confirming reliance on iron trafficking during erythropoiesis. When erythroblasts are treated with camonsertib (1nM, 10nM, and 30nM), proliferation and differentiation are reduced in a dose dependent fashion. Specifically, the proportion of early-stage erythroblasts decreases, while ROS concentration and NCOA4 transcripts increase and FTH transcripts decrease in treated cells; all consistent with enhanced ferritinophagy (Figure 1 and 2). Erythropoietin (EPO) supplementation does not affect erythroblast proliferation, differentiation, apoptosis, or ROS levels in camonsertib treated cells. Finally, the addition of ferristatin-1, a ferroptosis blocking agent, decreases ROS, increases apoptosis, and prevents the dose-dependent reduction in early-stage erythroblast numbers associated with camonsertib therapy, doubling the fraction of early-stage erythroblasts (Figure 2).
Conclusions: These results demonstrate for the first time that 1) camonsertib-induced anemia is reversible in vivo; 2) high levels of ROS, characteristically found in early-stage erythroblasts, increase their susceptibility to ATR inhibition; and 3) the effect of ATR inhibition on erythropoiesis is mediated by increased ferritinophagy, inducing ferroptosis. Although supplemental EPO does not alleviate the erythroid vulnerability to camonsertib, intermittent dosing allows for erythroid cell recovery, minimizing anemia while maintaining antitumor efficacy. Taken together, we provide evidence of the potential for manipulating ferritinophagy and ferroptosis to modulate erythropoiesis and enable an evidence-based strategy to prevent or enhance management of ATRi-induced anemia.
Disclosures: Ferraro: Repare Therapeutics: Current Employment. Li: Repare Therapeutics: Current Employment. Fournier: Repare Therapeutics: Current Employment. Hoffman: Repare: Research Funding; Ionis: Consultancy; Silence Therapeutics: Consultancy; Novartis: Other: Chair DSMB; Protagonist Therapeutics: Consultancy; Turning Point: Research Funding; Scholar Rock: Research Funding; Abbvie: Other: Chair DSMB, Research Funding; Novartis: Research Funding. Fretland: Repare Therapeutics: Current Employment. Roulston: Repare Therapeutics: Current Employment. Ginzburg: Repare: Research Funding; Dexcel: Consultancy; Takeda: Consultancy; Ionis: Consultancy; Protagonist: Consultancy, Research Funding.
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