Hoxa11-mediated reduction of cell migration contributes to myeloid sarcoma formation induced by cooperation of MLL/AF10 with activating KRAS mutation in a mouse transplantation model: Hoxa11 in myeloid sarcoma formation

The molecular mechanism of myeloid sarcoma (MS) formation remains nuclear. Our clinical and mouse model findings from a previous study revealed that cooperation of KMT2A (MLL) translocation (MLL-t) with activating N-/K-RAS mutations promoted MS formation in a shorter latency. To improve the understanding of MS formation, in this study, we performed imaging cell trafficking analysis and demonstrated that cells harboring cooperating mutations migrated more slowly to omental adipose tissues and more cells were retained in adipose tissues in vivo. Comparison of transcriptome profiling among three pairs of mouse MLL/AF10(OM-LZ) leukemia cell lines harboring activating and wild-type KRAS identified 77 differentially expressed genes (DEGs) with >1.5-fold change. Functional annotation of these 77 DEGs using Gene Ontology (GO) enrichment analysis followed by cluster analysis revealed that GO terms related to development/differentiation have the highest enrichment score. The roles of Hoxa10 and Hoxa11, two genes which mapped to this cluster, were further characterized. Silencing Hoxa10 and Hoxa11 in cells harboring cooperating mutations prolonged the survival and reduced MS formation, respectively, in the recipient mice. Data of imaging cell trafficking as well as competitive engraftment and clonal expansion analyses indicated that silencing or overexpressing Hoxa11 in mouse leukemia cells affected cell migration and retention in omental adipose tissue. Although silencing Hoxa11 in leukemia cells did not affect Cxcr4 expression, it resulted in increased transwell migration, motility in confined spaces 3 μm in size, and cell protrusion. Our results revealed that Hoxa10 plays an important role in survival and Hoxa11 contributes to MS formation in MLL-t acute myeloid leukemia with activating KRAS mutation.