Abstract: Objective To construct a mouse-derived tumor organoid that can retain various types of immune cells in the immune microenvironment without artificial reconstruction. Methods The mouse-derived tumor organoids were cultured and constructed by air-liquid interface method. The histological morphology of the tumor organoids was analyzed by hematoxylin and eosin(HE). The proportion of various types of immune cells in the tumor organoids was analyzed by flow cytometry. The interleukin-2 (IL-2) was used to maintain the number of T lymphocytes in tumor organoids. Results The tumor organoids from three tumor types of mouse CT26 colon cancer, Lewis lung cancer and MC38 colon cancer all retained the histomorphology of the original tumor. Compared with mouse CT26 colon cancer tumor tissues, the proportion of CD4⁺T cells, CD8⁺ T cells and B cells in tumor organoids didn't show significant change and the proportion of macrophages decreased from 66.7% to 44.3%. The proportion of dendritic cells decreased from 66.5% to 7.25%. Compared with mouse Lewis lung cancer tumor tissue, the proportion of CD4⁺T cells, macrophages, dendritic cells and B cells in tumor organoids remained unchanged and the proportion of CD8⁺ T cells decreased from 5.6% to 1.95%. Compared with mouse MC38 colon cancer tumor tissue, the proportion of CD4⁺T cells, CD8⁺ T cells and B cells in tumor organoids remained unchanged, the proportion of macrophages decreased from 33.5% to 17%, and the proportion of dendritic cells decreased from 46.8% to 1.2%. IL-2 could increase the tumor-infiltrating T lymphocytes in tumor organoids derived from three tumor types. Conclusions Mouse tumor organoids retain the histological morphology of the original tumor and the various types of immune cells are retained in a certain extent. IL-2 can increase the quantity of T lymphocytes.

Key words: air-liquid interaction method, tumor organoid, immune microenvironment, immune cells, interleukin-2 (IL-2)