Mechanisms of transformation and therapy resistance in myelodysplastic syndrome and acute myeloid leukemia

Myelodysplastic syndrome (MDS) is a heterogenous myeloid lineage malignancy characterized by blood cell morphological dysplasia, ineffective clonal hematopoiesis, and risk of secondary transformation to acute myeloid leukemia (sAML). Genomic sequencing of large MDS cohorts has led to the identification of recurrent genetic abnormalities that carry independent prognostic significance and overlap with mutational changes in sAML. However, no set of mutations is sufficient to predict the transformation of MDS raising the question of how an identical genotype produces MDS in one patient and sAML in another. We hypothesize there are therapeutically targetable cellular processes altered by the initiating genetic changes in MDS that predict transformation to sAML. To uncover novel cellular pathways involved in MDS transformation, we performed an unbiased genome-wide CRISPR/Cas9 in a human MDS cell line, MDS-L. We discovered loss of FBXO11 expression, an Fbox protein and component of the SCF ubiquitin ligase complex, imparts cytokine-independent survival of MDS-L, a surrogate for MDS transformation. Multiple replicates of this screen are currently underway to uncover additional candidates. With this workflow optimized, we will also perform two other genome-wide CRISPR/Cas9 screens to: 1) Uncover mediators of resistance to FDA-approved therapies such as azacitidine and lenalidomide, and 2) Identify genes involved in the in vivo transformation of MDS to sAML using mouse models. In our initial genome-wide screen for cytokine independent survival of MDS-L, we identified a potential tumor suppressor role of FBXO11 in the transition of MDS to sAML. FBXO11 functions as a substrate adaptor for the E3-ubiquitin ligase complex, therefore we hypothesize that loss of FBXO11 stabilizes its targets to promote leukemogenesis. We have queried the Bloodspot gene expression database to show decreased levels of FBXO11 in a variety of AML samples, including complex karyotype, compared to