Acute monocytic leukaemia (AML-M5) associated antigen-34 (MLAA-34) is a novel antigen overexpressed in patients with acute monocytic leukaemia. RNA interference is a promising therapy in oncology, especially for refractory acute leukaemia. In this study, we delivered MLAA-34 siRNA into AML-M5 THP-1 cells using CpG(B)-MLAA-34 siRNA conjugates, in the absence of any other transfection reagent. The uptake efficiency and the rate of apoptosis were measured by using flow cytometry. The level of relevant mRNAs was measured by quantitative PCR. THP-1 cell invasion was assessed by transwell assay. Protein expression was analysed by western blotting. The spleen and liver of AML-M5 nude mice were measured and weighted after euthanisation. Spleen sections were analysed by immunohistochemistry. We found that MLAA-34 siRNA was successfully delivered into THP-1 cells and induced MLAA-34 gene silencing via the blockade of JAK2/STAT3 and Wnt/-catenin signalling pathways. In addition, CpG(B)-MLAA-34 siRNA upregulated Gsk3β protein expression, resulting in retraining of the JAK2/STAT3 and Wnt/β-catenin signalling pathways. Importantly, CpG(B)-MLAA-34 siRNA reduced the survival and invasiveness of THP-1 cells. We further demonstrated that CAB39L was effectively downregulated by CpG(B)-MLAA-34 siRNA in vivo. These findings suggested CpG(B)-MLAA-34 siRNA conjugates may provide a novel therapeutic strategy for acute monocytic leukaemia.
Keywords: Acute monocytic leukaemia; CpG(B) oligonucleotides; JAK2; MLAA-34; STAT3; siRNA; targeted delivery; toll-like receptor 9.