Targeting of the B-lineage leukemia stem cells and their progeny with norcantharidin encapsulated liposomes modified with a novel CD19 monoclonal antibody 2E8 in vitro

Abstract

This study was aimed to generate a new agent, norcantharidin (NCTD) encapsulated liposomes modified with a novel murine anti-human CD19 monoclonal antibody 2E8 (2E8–NCTD–liposomes), to specifically target the B-lineage leukemia stem cells (B-LSCs) and their progeny in vitro. Our results have shown that the positive percentage of 2E8–NCTD–liposomes on CD19+ Nalm-6 cells was (95.82 ± 1.09)%, significantly higher than that on CD19− Molt-3 cells [(2.94 ± 0.07)%, P < 0.01], demonstrated by using multiparameter flow cytometry. The IC50 of 2E8–NCTD–liposomes on Nalm-6 cells using MTT assay was 14.52 μM, which was significantly lower than that on Molt-3 cells (45.89 μM, P < 0.01). The confocal microscopy and multiparameter flow cytometry analyses revealed that the internalization of 2E8–NCTD–liposomes into the cells and subsequently the release of NCTD into the cytoplasm to induce the apoptosis of B cells were responsible for specific cytotoxicity to the cells targeted. Real-time RT-PCR showed that the immunoliposomes were able to induce the apoptosis of B-LSCs via down-regulating the HLF and up-regulating the NFIL3 (nuclear factor, IL3 regulated) expressions at the mRNA level. Our conclusion is that 2E8–NCTD–liposome is a promising agent for selectively eradicating the B-LSCs and their progeny in vitro which warrants further studies in vivo.

Keywords::

• 2E8(CD19)
• immunoliposome
• leukemia stem cells
• norcantharidin
• targeting

Acknowledgements

We thank Professor Yi Jin at Zhejiang University School of Pharmacy and Professor Jue Wang at the pharmacy department of Children’s Hospital, Zhejiang University School of Medicine for their critical comments and suggestions. We also thank Mrs Baiqin Qian and Mr Hongqiang Shen for their excellent technical support.

Declaration of interest

This study was supported in part by grants from the National Natural Scientific Fund of China (No: 30170391, 30971283), the Zhejiang Provincial Fund of Natural Science (No: Z205166) and the Zhejiang Provincial Fund of Science and Technology Bureau (No: 2007C23007). The authors declare no conflict of interest.