DNMT3A in Development of Hematologic Malignancies

Project Summary/Abstract Cancers of the hematopoietic system, including leukemias and lymphomas, make up over 7% of new cancer diagnoses identified every year. While some types are increasingly treatable, others, such as acute myeloid leukemia, have a poor long-term survival rate. Recent studies have shown that initiating mutations often occur in hematopoietic stem cells (HSCs), resulting in a pre-malignant clone that can survive and expand for decades before additional hits drive exponential growth. For improved treatment of hematologic malignancies, it is imperative to understand the initiating mutations, how they drive pre-malignant expansion, how they promote transformation in the context of additional mutations, and to develop strategies to eradicate pre-malignant clones. The proposed program aims to address some of these questions, focusing on the role of mutations in the critical tumor suppressor DNMT3A. DNMT3A is important for normal stem cell differentiation and its deficiency cooperates with numerous other mutations to drive a variety of hematologic malignancies. Here, we will particularly focus on how DNMT3A mutations cooperate with a common co-mutation in nucleophosmin 1 (NPM1). Our previous work showed that the oncogenic cytoplasmic variant, NPM1c, drives gene expression at the critical HOXA locus. Here, using mouse models, human cell lines, and leukemia samples, we examine how DNMT3A loss potentiates the activity of NPM1c by modulating chromatin. We will also examine in depth the mechanisms of pathogenesis of NPMc by identifying its localization on chromatin, domains required for nuclear condensate formation, and protein and nucleic acid interacting partners. Finally, we will investigate the role of the ubiquitin-degradation complex adaptor protein DCAF8 in modulating DNMT3A in vivo with a view to potential therapeutic applications. We have established a battery of reagents and technologies including novel mouse models to facilitate this program. The program addresses questions designed to uncover fundamental biology with a view to developing new therapeutic approaches in the long-term. Given our long track-record in this area, we are poised to continue to make significant contributions to this critical area of cancer biology. The principles we uncover here may be applicable to other epigenetic regulators in a variety of malignancies.