Combinatorial genetics reveals the Dock1-Rac2 axis as a potential target for the treatment of NPM1;Cohesin mutated AML.

Acute myeloid leukemia (AML) is driven by mutations that occur in numerous combinations. A better understanding of how mutations interact with one another to cause disease is critical to developing targeted therapies. Approximately 50% of patients that harbor a common mutation in NPM1 (NPM1cA) also have a mutation in the cohesin complex. As cohesin and Npm1 are known to regulate gene expression, we sought to determine how cohesin mutation alters the transcriptome in the context of NPM1cA. We utilized inducible Npm1 cAflox/+ and core cohesin subunit Smc3 flox/+ mice to examine AML development. While Npm1 cA/+ ;Smc3 Δ/+ mice developed AML with a similar latency and penetrance as Npm1 cA/+ mice, RNA-seq suggests that the Npm1 cA/+ ; Smc3 Δ/+ mutational combination uniquely alters the transcriptome. We found that the Rac1/2 nucleotide exchange factor Dock1 was specifically upregulated in Npm1 cA/+ ;Smc3 Δ/+ HSPCs. Knockdown of Dock1 resulted in decreased growth and adhesion and increased apoptosis only in Npm1 cA/+ ;Smc3 Δ/+ AML. Higher Rac activity was also observed in Npm1 cA/+ ;Smc3 Δ/+ vs. Npm1 cA/+ AMLs. Importantly, the Dock1/Rac pathway is targetable in Npm1 cA/+ ;Smc3 Δ/+ AMLs. Our results suggest that Dock1/Rac represents a potential target for the treatment of patients harboring NPM1cA and cohesin mutations and supports the use of combinatorial genetics to identify novel precision oncology targets.