Abstract: Objective:To construct a humanized mouse models with human immune system and human tumor growth, and to provide the basis for human tumor immunological research and evaluation on the efficacy of tumor immunotherapeutic durgs. Methods:The humanized mice with human immune system reconstruction were established by intravenous injection of human CD34⁺ fetal liver cells combined with implantation of human fetal thymic tissue under the renal capsule of NOD/SCID IL 2rg-/- after sub-lethal total body irradiation. The peripheral blood was collected,and the immune cell reconstitution was monitored every 3 weeks from the 3th week after humanization, including the ratios of CD45⁺, CD33⁺, CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺,and CD56⁺ cells. The human A375 melanoma cells were subcutaneously inoculated at the 15th week after humanization,and the tumor volume was measured every 5 d.. Six weeks after tumor inoculation, the mice were sacrificed and the composition of human immune cells as well as their phenotypes in peripheral blood, bone marrow, lymph node,spleen and tumor tissue were measured by flow cytometry. The composition of human immune cells as well as their phenotypes in tumor tissue were measured by immunohistochemistry. Results:At the 15th week after humanization, the ratio of human T cells was (33.53±8.57)% and the ratio of human B cells was (43.33±10.05)% in the peripheral blood of the humanized mice. The human melanoma grew slowly during the first 3 weeks, and the human tumor sizes expanded rapidly and reached (1 564±334.3) mm³ at the 6th week after tumor inoculation. The immunohistochemical and flow cytometry analysis results showed that a large number of human T cells, which mainly composed by CD8⁺ T subsets, infiltrated in the human melanoma. The ratio of CD8⁺/CD4⁺ in tumor tissue was significantly higher than those in the peripheral blood, bone marrows, lymph nodes and spleen tissue (P<0.01). The levels of PD-1 molecules expressed in tumor-infiltrated human CD4⁺ T and CD8⁺ T cells were higher than those in the peripheral blood and immune organs. Conclusion:A humanized mouse models with human immune system and allogeneic human melanoma is successfully established. The high levels of human immune cells, including human T cells and B cells, can be detected in the peripheral blood, lymph organs, and human tumor tissue in this mouse model.

Key words: humanized mice, melanoma, tumor microenvironment, cancer immunotherapy