Interrogating Erythroid Differentiation and BCL-XL Axis in TP53-mutated Acute Myeloid Leukemia

About This Grant

Abstract Acute myeloid leukemia (AML) is a diverse hematologic malignancy marked by rapid proliferation of poorly differentiated myeloid cells, causing ineffective hematopoiesis and bone marrow suppression. TP53 mutations, present in ~15-20% of AML patients, are associated with poor responses to conventional therapies, including the BCL-2 inhibitor venetoclax, and a grim prognosis of less than six months median survival. Despite various strategies to target TP53-mutated AML, clinical advancements have been limited, highlighting the urgent need for novel approaches for this patient subgroup. Our preliminary data support that TP53-mutated AML from primary patients have higher dependency on BCL-XL and enriched for erythroid differentiation signatures. Erythroid differentiation was correlated with both BCL-XL and GATA1 transcription factor. Notably, we recently reported that acute erythroid leukemia (AEL), a subtype of AML with pure erythroid phenotype and highly enriched for TP53 mutations, is similarly dependent on BCL-XL. This data supports the rationale to exploit BCL- XL inhibition as a promising therapeutic strategy to overcome TP53-mutated therapeutic resistance mediated via erythroid differentiation. We recently demonstrated that the novel dual BCL-XL and BCL-2 Proteolysis targeting chimera (PROTAC) 753b can indeed induce cell death in AML cell lines and primary AML samples resistant to venetoclax. However, its efficacy in TP53-AML subset and in overcoming erythroid-mediated resistance has not been tested. Further, the underlying mechanisms governing erythroid differentiation, GATA1- related erythroid differentiation and its relation to BCL-XL in TP53-mutated AML are not explored. We hypothesize that TP53-mutated AML have a marked predisposition to acquire an erythroid phenotype associated with BCL-XL dependence, which can be leveraged to overcome therapeutic resistance in TP53-mutated AML via BCL-XL or dual BCL-2/BCL-XL degradation. Aim 1 will employ multimodal characterization of primary AML patient datasets (published and unpublished) that includes single cell RNA, single cell ATAC and bulk RNA and define differentiation states and potential dependencies. We will explore the GATA1 regulation of erythroid differentiation and BCL-XL expression via performing multiome analysis and CUT&RUN to identify GATA1 binding in isogenic TP53-mutated and wildtype K562 erythroid leukemia cell lines. Using machine learning, we will identify therapeutic targets and dependencies that mediate erythroid differentiation in TP53-mutated AML. Aim 2 will test the efficacy of the BCL-XL degraders including DT-2216, clinical BCL-XL degrader that has shown safety and preliminary efficacy in the ongoing solid tumor trials, and of dual BCL-2/BCL-XL degrader 753b, in TP53-mutated AML cell lines, primary patients’ samples and in PDXs in combination with hypomethylating agents. Findings from this work have the potential to significantly advance the therapy of this challenging AML subset, providing a foundation for clinical trials aimed at improving patient outcomes.