Career Enhancement Program

Program Directors

Matt Walter, MD   (Wash U)

Geoffrey Uy, MD   (Wash U)

Timothy J. Ley, MD (Wash U)

The Leukemia SPORE Career Enhancement Program (CEP) has a goal of recruiting and supporting a set of new investigators in the field of translational leukemia research. To accomplish this objective, the CEP will provide financial support and mentored research training. It will leverage institutional strengths to recruit basic scientists and clinical investigators from varied disciplines and backgrounds to promote multidisciplinary translational research. These goals will be accomplished in three ways: 1) We will recruit and financially support new investigators in the field of translational leukemia research. 2) We will provide training and mentoring to junior faculty from all backgrounds in translational leukemia research. CEP will work with new investigators to craft an individualized career development plan that may combine didactic coursework, patient care, and career skills tailored to their individual goals. 3) We will foster inter-SPORE collaborations. We have established educational exchanges to provide CEP awardees the opportunity to present their research and meet with the leadership at a peer Leukemia SPORE Institution.

CEP Awardee 2025

Stefan P. Tarnawsky

Tarnawsky Headshot (1)

The Role of TP53 in Mutant U2AF1 Myelodysplastic Syndromes

The goal of this project is to identify how splicing factor gene mutations regulate the growth of hematopoietic stem and progenitor cells (HSPCs) and to develop novel therapies to treat patients with myeloid neoplasms such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML).

Among genes frequently mutated in clonal hematopoiesis, splicing factor gene mutations (e.g. U2AF1, SRSF2) have the highest growth advantage and the highest risk of progression to malignancy. However, in both human and mouse models, splicing factor gene mutations consistently reduce HSPC growth, compared to controls. Our preliminary in vitro and in vivo data suggest that the impaired growth of HSPCs expressing the common U2AF1S34F mutation is due to activation of TP53. This paradoxical finding suggests that for splicing factor mutant HSPCs to cause myeloid neoplasms, they must first overcome growth-suppressing signals. Understanding how splicing factor gene mutations initially impair the growth of HSPCs is the first step in understanding how mutant cells later adapt, expand, and cause disease.

R-loops are naturally occurring DNA:RNA triple helices, whose formation must be tightly balanced with RNASEH1-mediated degradation to prevent stalled replication forks, DNA damage, and TP53 activation. R-loops accumulate in models of splicing factor mutant MDS. This suggests that the high TP53 activity and impaired growth of U2AF1S34F HSPCs may be due to their unresolved R-loops. We hypothesize that RnaseH1 overexpression will rescue the growth of U2af1S34F HSPCs in vivo by normalizing their R-loops and reducing TRP53 pathway activity. In parallel, the increased R-loops in MDS patients with splicing factor mutations indicates a tipped balance favoring R-loop formation > degradation. This suggests that further disruption of R-loop maintenance may preferentially kill splicing factor mutant cells by causing insurmountable replication stress. Using complementary genetic and pharmacologic approaches, we will test whether mouse and human MDS patient-derived U2AF1S34F HSPCs are preferentially sensitive to RNASEH1 inhibition due to an overwhelming accumulation of R-loops.

Collectively, this project will elucidate the mechanisms whereby splicing factor mutant HSPCs activate TP53, providing insight into how mutant cells adapt and expand in splicing factor mutant myeloid neoplasms. Our findings will nominate disrupting R-loop maintenance via RNASEH1 inhibition as a novel therapeutic strategy to treat the 50% of MDS patients and 20% of AML patients who have splicing factor gene mutations.

CEP Awardee 2024

Michael Kramer

Michael Kramer

The goal of this project is to identify druggable targets for Acute Myeloid Leukemia (AML) initiated by mutations in DNMT3A and NPM1, and to test and validate interventions that target these vulnerabilities.

NPM1 and DNMT3A are among the most commonly mutated genes in AML patients. These mutations co-occur more frequently than expected by chance, with ~15% of AML patients containing mutations in both genes. Based on this clinical observation, we have generated mouse models that recapitulate this synergy. Mice with either Dnmt3aR878H or Npm1cA mutations develop AML with a long latency (>12 months) and low penetrance, but mice with both mutations develop AML in 6-15 months with nearly 100% penetrance. We have characterized 11 independent, spontaneous AMLs from this model that rapidly cause fatal leukemias in secondary recipients. Whole genome sequencing revealed one or more human AML-like cooperating mutations in each tumor (e.g. mutations in Flt3, Idh2, Ptpn11, Kit, Nf1 and Cbl). Surprisingly, 11 of the 12 AMLs also had an amplification of murine chromosome 7 as the sole structural variant. Using publicly available data from similar mouse models, we identified a minimally amplified 8.9 Mbp region on chromosome 7 containing 209 genes. We identified Gab2 on this interval as a key candidate gene, since its expression is also increased in human AMLs, and since it is known to facilitate signaling from receptor tyrosine kinases (including FLT3) to downstream pathways. We have now shown that overexpression of Gab2 induces significant expansion of hematopoietic cells from Dnmt3aR878H x Npm1cA mice, leading to the accelerated development of AML. Importantly, overexpression of Gab2 induces more limited expansion of hematopoietic cells with the Npm1cA mutation only, and is selected against in cells with Dnmt3aR878H only, and in wildtype cells, suggesting that its actions may require the presence of both Dnmt3a and Npm1 mutations. We have also observed that knockout of Gab2 in fully transformed murine AML leads to slower growth of the AML cells. In this project we will aim to use these findings can be used to identify novel, druggable targets in human AMLs with mutations in DNMT3A and NPM1. Firstly, we will use CRISPR-Cas9 gene editing of GAB2 in primary human AML cells to evaluate whether GAB2 may be a potential therapeutic target in human AML. Secondly, we will perform a CRISPR-based  “essentiality screen” of druggable targets in murine AML arising in Dnmt3aR878H x Npm1cA mice to identify additional potential therapeutic targets. Finally, we will evaluate the top candidate genes using CRISPR-mediated gene editing in primary human AML samples.  If successful, these studies will identify additional therapeutic targets for AML cells initiated by DNMT3A and NPM1 mutations, with a long-term goal of translation in early-phase clinical trials.