DOCK1 Expression Enhances the Activity of the Notch Signaling Pathway and Promotes the Proliferation and Survival of Acute Myeloid Leukemia Cells

In spite of recent advances in genetic risk categorization and treatment, the available options for patients of acute myeloid leukemia (AML) resistant to standard chemotherapy remain limited. There is an urgent need to address this problem. In a prior study, we identified DOCK1 gene expression as an independent prognostic marker by means of microarray analysis of gene expression in an AML cohort adopting the ELN 2010 risk stratification. To validate the prior results and explore deeper into the molecular mechanisms, we analyzed the clinical impacts of DOCK1 expression on a new cohort of 341 de novo non-M3 AML patients diagnosed from February 2004 to December 2016. These patients were risk-stratified using the 2022 ELN classifications, and we utilized more advanced RNA sequencing technology for our analysis. All of the patients were treated with standard chemotherapy. We demonstrate that higher DOCK1 expression still correlates with unfavorable cytogenetics and mutations, and it is an independent adverse prognostic factor.

We subsequently investigated its pathogenesis using cell lines, xenograft models, and a hematopoietic cell-specific Dock1-conditional knockout model in mice. Cell line experiments showed positive roles of DOCK1 in proliferation and viability. This observation is further corroborated by xenograft experiments, in which mice transplanted with DOCK1-knockdown cells had longer survival times than those engrafted with control cells. Although mice with a hematopoietic cell-specific knockout of Dock1 exhibited minimal phenotypic changes, the loss of Dock1 ameliorated MN1-induced AML in vivo. Transcriptome analyses of cell lines and human samples consistently revealed upregulation of NOTCH signaling pathway in cells with higher DOCK1 expression, as evidenced by higher expression levels of HES1, a direct downstream target of NOTCH pathway. Single-cell RNA sequencing of MN1-induced mouse leukemia cells within Dock1-conditional knockout background also revealed a unique cluster of cells that predominantly existed in DOCK1-wild type rather than Dock1-conditional knockout mice and exhibited the highest expression of DOCK1, MN1, and HES1 among all clusters. These cells showed upregulation of stem cell function, G2M checkpoint, E2F targets, and Myc signaling pathways, consistent with the phenotypes of DOCK1 in our study. Our findings highlight the role of DOCK1 expression in the pathogenesis of AML and suggest DOCK1 as a potential therapeutic target for this group of patients.

No relevant conflicts of interest to declare.