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.

Two successful deliveries of healthy children by a young woman diagnosed and treated during induction and relapsed therapy for acute promyelocytic leukemia.

INTRODUCTION: Acute promyelocytic leukemia is an oncologic emergency. The limited cases reported in the literature have led to poor understanding of the safety of management of acute promyelocytic leukemia during pregnancy. CASE REPORT: Herein is an acute promyelocytic leukemia case of a 22-year-old young pregnant woman who had various social problems. The patient was diagnosed with acute promyelocytic leukemia in her the second trimester of her first pregnancy.Management and outcome: She was treated with all-trans-retinoic acid with idarubicin and successfully delivered a healthy baby. She completed induction with idarubicin but defaulted her all-trans-retinoic acid, 6-mercaptopurine and methotrexate maintenance. She relapsed after one year and was salvaged with all-trans-retinoic acid high dose cytarabine and arsenic trioxide. She went into remission and had autologous stem cells collected and was planned for an autologous stem cell transplant but she defaulted. She relapsed when she was pregnant with her second baby during her third trimester (29+weeks) 10 months later. Salvage chemotherapy with arsenic trioxide, all-trans-retinoic acid and idarubicin was given. Patient underwent an emergency lower segment caesarian section at 31 weeks of pregnancy due to abnormal fetal cardiotocography. A healthy baby was delivered. DISCUSSION: This drug regimen is controversial during pregnancy owing to the teratogenic effects and fatal retinoic acid syndrome especially in early gestation. In this case, patient was started the induction therapy of all-trans-retinoic acid treatment at her second trimester during her first pregnancy. CONCLUSION: Our lady demonstrated the possibility of using all-trans-retinoic acid and arsenic trioxide and chemotherapy during second and third trimester with successful pregnancy outcomes.