Acute myeloid leukemia (AML) is the second most common type of leukemia and accounts for 80% of adult acute leukemia cases and is characterized by the accumulation of poorly or undifferentiated myeloid blast cells. Standard treatment includes chemotherapy, which if unsuccessful, is followed by more rigorous chemotherapy as well as stem cell transplantation. Considering most patients are over the age of 45, these more rigorous therapies are not always possible, and as such, new therapies must be developed. Furthermore, AML patients harboring a chromosomal rearrangement involving Multiple Lineage Leukemia (MLL) that results in the expression of an MLL fusion protein exhibit far worse prognoses than patients without. In recent years, Danio rerio (zebrafish) has emerged as a powerful model organism for investigating human blood malignancies due to the conservation of hematopoiesis between humans and zebrafish. The first objective of this study was to develop a transient transgenic AML model in zebrafish, and the second objective was to determine if co-treatment with two medications currently in human trials for AML, Venetoclax and Flavopiridol, would be more effective than using either drug individually. In order to develop a transient transgenic AML model, we first developed a DNA construct encoding a known mixed lineage leukemia (MLL) fusion protein associated with human AML, MLL-ENL, driven by the zebrafish lysozyme C (lyz) promoter, which drives myeloid specific expression in zebrafish. We then microinjected single-cell zebrafish embryos with DNA encoding lyz driven MLL-ENL along with transposase mRNA to facilitate the genomic integration of MLL-ENL. Injected embryos were first tested for MLL-ENL expression, and subsequently tested for AML phenotypic characteristics, via whole mount in-situ hybridization (WISH) at 72 hours post fertilization (hpf). First, WISH analysis utilizing a human MLL riboprobe verified MLL-ENL expression in injected embryos, and WISH analysis utilizing the same MLL riboprobe revealed an expansion and clustering of MLL positive cells in injected embryos, characteristic of an AML phenotype. Embryos injected with MLL-ENL DNA were then treated with either DMSO (vehicle), 200 nanomolar (nM) Venetoclax, 200 nM Flavopiridol, or 200 nM Venetoclax and 200 nM Flavopiridol from 24 hpf to 72 hpf. MLL WISH analysis of injected and treated embryos revealed a reduction in MLL positive cells in both Venetoclax treated embryos and Flavopiridol treated embryos, and an even greater reduction in MLL positive cells in embryos treated with both Venetoclax and Flavopiridol, compared to controls. Although further analysis is required to be confident, these data suggest that we successfully developed an AML transient transgenic model in zebrafish. Furthermore, these data suggest that Venetoclax and Flavopiridol co-treatment could yield better outcomes for AML patients than treatment with either drug individually.

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Myelodysplastic syndrome (MDS) is a group of clonal bone marrow disorders characterized by bone marrow dysplasia with myeloblasts <20%, typically seen in older patients. MDS has a significant risk of transformation to Acute Myeloid Leukemia (AML). We report a case of MDS transformed to AML, with sustained Complete Remission and incomplete count recovery (CRi) with treatment. A 78-year-old male with a 2-year history of leukopenia had a workup including bone marrow biopsy (BMBX) revealing intermediate- risk MDS with 13% blasts (Refractory Anemia Excess Blasts II), deletion 20 on cytogenetics and normal MDS FISH panel. He was categorized as revised IPSS score 4.5 on risk stratification. Patient initiated treatment with hypomethylating agent Azacytidine with subsequent improved BMBX with 7% blasts. He continued Azacytidine with dose reductions due to cytopenia only to develop 14% blasts on another follow up BMBX. He continued successful treatment for over 3 years before developing with 40-50% CD 34+/CD117+ blasts in the bone marrow consistent with transformation to AML. He commenced salvage treatment with Venetoclax and full dose Azacytidine as advanced age and performance status precluded transplant options. Repeat BMBX 4 weeks following Venetoclax showed hypocellular marrow, blasts percentage less than 2% indicating a CRi. Two other subsequent marrow exams have demonstrated sustained CRi twelve months after transformation with continued Venetoclax and Azacytidine administration. Around 30% of MDS patients eventually transform to secondary AML. Azacytidine therapy has significantly improved survival and time to AML transformation in intermediate-2 and high-risk MDS patients. Venetoclax, a BCL-2 inhibitor, in treating AML. Based on the results of the VIALE-A trial, the incidence of CR (complete remission) was higher around 36.7% with Azacytidine-Venetoclax (A-V) compared to 17.9% with Azacytidine. The composite CR (CR+ Cri) was higher in the A-V group, 66.4% compared to 28.3% with Azacytidine group. The median overall survival was 14.7 months in the A-V group compared to 9.6 months in the Azacytidine group. Our patient achieved a CRi with A-V treatment and has demonstrated a durable response beyond 16 months in secondary AML which has a bleak prognosis indicating the promise of this new combination treatment.

No description available.