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

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 mu M, which was significantly lower than that on Molt-3 cells (45.89 mu M, 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.