Mechanisms underlying increased risk of hematological malignancy in sickle cell disease.

PROJECT SUMMARY/ABSTRACT Sickle cell disease (SCD) affects millions globally and results in recurrent vascular occlusions, chronic organ damage and early death. While childhood mortality is reduced and patients are surviving to adulthood with current therapies, an increased risk of hematological malignancy (HM) in SCD is becoming evident. Risk of HM is higher following gene therapy. Gene therapy involves hematopoietic stem cell transplant (HCT) of gene- modified autologous/sickle hematopoietic stem and progenitor cells (HSPC), and has had remarkable success and FDA approval. A similar high risk is observed in allogeneic-HCT SCD patients with suboptimal engraftment. However, the specific pathobiology that predisposes to increased HM is unknown, and necessary to address, since curative therapies (gene therapy and HCT) are on the forefront. We hypothesize that increased oxidative stress induced DNA damage results in HSPC clones with deleterious mutations; these clones amplify due to persistent HSPC replicative stress from SCD, and when the replicative stress is further magnified in gene therapy, where autologous gene-modified HSPC have to regenerate to reconstitute the entire hematopoiesis following myeloablative conditioning. We will: (1) Perform gain and loss of function experiments to increase or reduce the oxidative stress-induced DNA damage to HSPC, and study the development of clonal hematopoiesis and HM in SCD mice versus their normal counterparts. (2) Impose HCT-mediated regenerative stress on autologous young and old HSPC and assess whether development of HM occurs de novo, or from existing clones with deleterious mutations in putative oncogenes by high-depth next generation sequencing. Modeling the increased risk of HM in SCD will help identify underlying mechanisms, which can then be targeted to mitigate this risk.