2011 – PATHWAY-GUIDED INTERCEPTION OF DOWN SYNDROME-ASSOCIATED LEUKEMOGENESIS

Abstract

Preventing leukemia remains one of the most ambitious goals in oncology. Myeloid leukemia associated with Down syndrome (ML-DS) offers a unique opportunity, as it evolves from a clinically detectable preleukemia, transient abnormal myelopoiesis (TAM). TAM arises in 30% of neonates with Down syndrome and progresses in 20% of cases. Defined by trisomy 21 and GATA1 mutations resulting in the truncated transcription factor GATA1s. To identify vulnerabilities, we performed CRISPR/Cas9-based dropout screens in a murine fetal hematopoietic stem/progenitor cell model engineered to express GATA1s in the context of chromosome 21 oncogene overexpression. A custom sgRNA library targeting genes linked to United States Food and Drug Administration (FDA)-approved drugs enabled mapping from genetic dependency to therapeutic candidate. Integration of functional screening data with patient-derived transcriptomes, gene essentiality scores, and pathway enrichment analyses revealed a reliance of TAM cells on IMPDH2 and the de novo purine biosynthesis pathway. Treatment with mycophenolate mofetil (MMF), a clinically established inhibitor with a favorable safety profile, induced apoptosis in TAM models and ML-DS cell lines, whereas healthy CD34⁺ progenitors are largely spared. Synergy studies have shown promising results when combining MMF with BCL2/XL inhibitors. Transcriptomic analyses revealed reciprocal adaptive circuitry between purine biosynthesis and anti-apoptotic signaling, explaining the mechanistic basis of synergy. Metabolomic phenotyping of treated primary TAM samples demonstrated that combination therapy in particular induced synergistic metabolic collapse by disrupting the cells compensatory networks. In vivo treatment of the preleukemic model conferred significant survival benefit, supporting feasibility of leukemia interception by targeting purine metabolism and survival signaling before malignant transformation.

Preventing leukemia remains one of the most ambitious goals in oncology. Myeloid leukemia associated with Down syndrome (ML-DS) offers a unique opportunity, as it evolves from a clinically detectable preleukemia, transient abnormal myelopoiesis (TAM). TAM arises in 30% of neonates with Down syndrome and progresses in 20% of cases. Defined by trisomy 21 and GATA1 mutations resulting in the truncated transcription factor GATA1s. To identify vulnerabilities, we performed CRISPR/Cas9-based dropout screens in a murine fetal hematopoietic stem/progenitor cell model engineered to express GATA1s in the context of chromosome 21 oncogene overexpression. A custom sgRNA library targeting genes linked to United States Food and Drug Administration (FDA)-approved drugs enabled mapping from genetic dependency to therapeutic candidate. Integration of functional screening data with patient-derived transcriptomes, gene essentiality scores, and pathway enrichment analyses revealed a reliance of TAM cells on IMPDH2 and the de novo purine biosynthesis pathway. Treatment with mycophenolate mofetil (MMF), a clinically established inhibitor with a favorable safety profile, induced apoptosis in TAM models and ML-DS cell lines, whereas healthy CD34⁺ progenitors are largely spared. Synergy studies have shown promising results when combining MMF with BCL2/XL inhibitors. Transcriptomic analyses revealed reciprocal adaptive circuitry between purine biosynthesis and anti-apoptotic signaling, explaining the mechanistic basis of synergy. Metabolomic phenotyping of treated primary TAM samples demonstrated that combination therapy in particular induced synergistic metabolic collapse by disrupting the cells compensatory networks. In vivo treatment of the preleukemic model conferred significant survival benefit, supporting feasibility of leukemia interception by targeting purine metabolism and survival signaling before malignant transformation.