OBJECTIVEThis study was to establish a stable, effective and reproducible human acute promyelocytic leukemia model in severe combined immunodeficient (SCID) mice by using NB4 cell line, and to investigate the disease course character and biological behaviors.

METHODSThree-five-week-old SCID beige mice were divided randomly into two groups: experimental and control group. SCID mice of experimental group were transplanted by tail vein (iv) injection of 5×10(6) NB4 cells. The WBC cell count and the positive rate of promyelocytes in peripheral blood were dynamically monitored by using smears. Morphological examination and histopathological assay were employed to confirm NB4 cell infiltration in organs (liver, spleen, lung, kidney and brain). The expression level of PML-RARα fusion protein was detected by Western blot.

RESULTSWithin two weeks there was no significant difference in peripheral blood WBC count between two groups (P > 0.05), meanwhile, NB4 cells were not found. At the day 21 and 28 after inoculation, the peripheral blood white blood cell count of experimental group reached to (4.79 ± 1.13)×10(9)/L and (7.62 ± 2.24)×10(9)/L respectively, which were significantly higher than that in control group (P < 0.05); simultaneously, the positive rates of promyelocytes on smears were (2.14 ± 0.63)% and (6.6 ± 2.76)%, respectively. Morphological observation showed single or multiple tumor lumps at day 21 after inoculation; HE staining of tissue biopsies demonstrated a large number of promyelocyte in the liver, spleen, lung, kidney and brain tissue. Cell immunofluorescence results showed that the CD33 expression of bone marrow cells in mice of experimental group was strongly positive (P < 0.05). Western blot confirmed that the PML-RARα fusion protein was expressed variously in liver, kidney and brain tissue.

CONCLUSIONSThe human acute promyelocytic leukemia SCID mouse model is succesfully established by tail vein injection of NB4 cells. This model can mimic the characters of involved bone marrow and diffuse growth of cells. This model is a useful tool to explore the pathogenic mechanism and experimental treatment of human leukemia.