Effective delivery of anti-PD-L1 siRNA with human heavy chain ferritin (HFn) in acute myeloid leukemia cell lines

Abstract

Because of the high biocompatibility, self-assembly capability, and CD71-mediated endocytosis, using human heavy chain ferritin (HFn) as a nanocarrier would greatly increase therapeutic effectiveness and reduce possible adverse events. Anti-PD-L1 siRNA can downregulate the level of PD-L1 on tumor cells, resulting in the activation of effector T cells against leukemia. Therefore, this study aimed to produce the tumor-targeting siPD-L1/HFn nanocarrier. Briefly, the HFn coding sequence was cloned into a pET-28a, and the constructed expression plasmid was subsequently transformed into E. coli BL21. After induction of Isopropyl β-D-1-thiogalactopyranoside (IPTG), HFn was purified with Ni-affinity chromatography and dialyzed against PBS. The protein characteristics were analyzed using SDS-PAGE, Western Blot, and Dynamic light scattering (DLS). The final concentration was assessed using the Bicinchoninic acid (BCA) assay. The encapsulation was performed using the standard pH system. The treatment effects of siPD-L1/HFn were carried out on HL-60 and K-562 cancer cell lines. The RT-PCR was used to determine the mRNA expression of PD-L1. The biocompatibility and excretion of siPD-L1/HFn have also been evaluated. The expression and purity of HFn were well verified through SDS-PAGE, WB, and DLS. RT-PCR analyses also showed significant siRNA-mediated PD-L1 silencing in both HL-60 and K-562 cells. Our study suggested a promising approach for siRNA delivery. This efficient delivery system can pave the way for the co-delivery of siRNAs and multiple chemotherapies to address the emerging needs of cancer combination therapy.

Keywords: Human heavy chain ferritin; Nanoparticle; PD-L1; siRNA.