Inhibition of PLK4 remodels histone methylation and activates the immune response via the cGAS-STING pathway in TP53-mutated AML.

Acute myeloid leukemia (AML) with TP53 mutation is one of the most lethal cancers and portends an extremely poor prognosis. Based on in silico analyses of druggable genes and differential gene expression in TP53-mutated AML, we identified pololike kinase 4 (PLK4) as a novel therapeutic target and examined its expression, regulation, pathogenetic mechanisms, and therapeutic potential in TP53-mutated AML. PLK4 expression was suppressed by activated p53 signaling in TP53 wild-type AML and was increased in TP53-mutated AML cell lines and primary samples. Short-term PLK4 inhibition induced DNA damage and apoptosis in TP53 wild-type AML. Prolonged PLK4 inhibition suppressed the growth of TP53-mutated AML and was associated with DNA damage, apoptosis, senescence, polyploidy, and defective cytokinesis. A hitherto undescribed PLK4/PRMT5/EZH2/H3K27me3 axis was demonstrated in both TP53 wild-type and mutated AML, resulting in histone modification through PLK4-induced PRMT5 phosphorylation. In TP53-mutated AML, combined effects of histone modification and polyploidy activated the cGAS-STING pathway, leading to secretion of cytokines and chemokines and activation of macrophages and T cells upon coculture with AML cells. In vivo, PLK4 inhibition also induced cytokine and chemokine expression in mouse recipients, and its combination with anti-CD47 antibody, which inhibited the "don't-eat-me" signal in macrophages, synergistically reduced leukemic burden and prolonged animal survival. The study shed important light on the pathogenetic role of PLK4 and might lead to novel therapeutic strategies in TP53-mutated AML.

Characterization of Drug Effect on Leukemia Cells Through Single Cell Assay With Optical Tweezers and Dielectrophoresis.

One of the greatest challenges in acute myeloid leukemia (AML) treatment is preventing relapse. Leukemia cells can hide in bone marrow niche or vascular niche. Hence, many chemical drugs cannot kill these cells. To characterize migration and adhesion properties of leukemia cells in specific niches, CXCR4/SDF- 1α signal pathway has been widely used for investigation. AMD3100 is treated as one of the most common chemical drugs that can inhibit this signal. In the current study, we particularly investigate the effect of AMD3100 on the adhesion property of leukemia cells on stromal cells by using engineering tools, namely, optical tweezers (OT) and dielectrophoresis (DEP), to probe single cell property. AMD3100 not only inhibits the CXCR4/SDF- 1α signal pathway but also reduces gene expression of CXCR4 and VLA-4 on leukemia cells. The drug also softens leukemia cells. This work provides a new way to investigate cell behavior under drug treatment. The use of combined engineering tools will benefit drug discovery and assessment for leukemia treatment.