Targeting HASPIN kinase disrupts SR protein-mediated RNA splicing and synergizes with BCL-2 inhibitor venetoclax in AML

Acute Myeloid Leukemia (AML) is a blood cancer complicated by acquired drug resistance, disease relapse, and low overall survival rates. Combination therapies using multiple targeted inhibitors can effectively treat AML patients. However, combination treatments are limited by the number of useable targets and our ability to create rational pairings using complimentary molecular mechanisms. Here, we used a human kinase domain-targeted CRISPR screen to identify histone H3 associated protein kinase (HASPIN) as a significant, understudied dependency in AML. HASPIN depletion significantly reduced growth rate, induced a cell cycle arrest, and dysregulated transcription in AML. A proteomics datamining study characterized splicing factors as major HASPIN kinase substrates and highlighted HASPIN's role as a splicing regulatory kinase. Accordingly, HASPIN depletion strongly dysregulated splicing and inversed aberrant, pro-leukemic splicing programs in AML patients. HASPIN inhibitor CHR-6494 effectively reduced cell viability across AML subtypes while sparing healthy cells. Furthermore, a novel combination therapy consisting of CHR-6494 and BCL-2 inhibitor Venetoclax synergistically reduced AML cell viability and resensitized Venetoclax-resistant AMLs to treatment. Our study presents HASPIN kinase as a novel, therapeutic target for AML, underscores an underappreciated role in splicing regulation, and proposes a viable combination treatment for clinical use. Overall design: RNA-sequencing of Kasumi-1 t(8;21) Human AML cell lines expressing either non-targeting control or HASPIN-targeting shRNAs. For analysis, 3 control samples were compared to 3 HASPIN knockdown samples.