Project 3: Novel therapies for spliceosome-mutant MDS

Timothy Graubert, MD, and Matthew Walter, MD

The long-term goal of this project is to develop novel mechanism-based therapies targeting myeloid malignancies with splicing factor mutations. We and others identified frequent, recurrent mutations in RNA splicing factors (e.g., U2AF1, SF3B1, SRSF2) in patients with myeloid malignancies, including myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and chronic myelomonocytic leukemia (CMML). The canonical hotspot mutations in U2AF1 (S34F), SF3B1 (K700E), or SRSF2 (P95H) alter RNA splicing. We recently reported that expression of mutant splicing factors or pharmacologic perturbation of splicing increase the abundance of R loops, which are structures containing DNA:RNA hybrids and displaced single-strand DNA. R loops trigger an ATR-dependent DNA damage checkpoint response that mediates resolution of the R loop to protect cells from genomic instability and cell death. Our preliminary data suggest that spliceosome mutant cells are more sensitive to ATR inhibition than wild-type cells. This project will explore the hypothesis that splicing factor mutations may create a vulnerability to ATR inhibition that can be exploited for the development of novel therapeutic strategies.