Effects of different levels of soluble PD-L1 protein on the growth of Lewis lung cancer transplanted tumor

: To investigate the effects of different doses of soluble PD-L1 (soluble form of Programmed death ligand 1, sPD-L1) protein on Lewis lung cancer cells, flow cytometry was used to detect the expression of PD-L1 (Programmed death ligand 1) on the surface of Lewis lung cancer cell lines and the expression of PD-1 on the surface of T lymphocytes in peripheral blood and spleen cells of C57BL/6 mice. A Lewis lung cancer animal model of C57BL/6 mice was established by transplanting Lewis lung cancer cells subcutaneously. The sPD-L1 protein was injected into the abdominal cavity of the mouse (sPD-L1 Ig) (working dose: 2.5, 5, 10 μg per mouse), while the sPD-L1 control protein was injected as a control. The growth of Lewis lung cancer xenografts was observed. On the 18th day after tumor cell inoculation, T lymphocyte subsets in mouse spleen were determined by flow cytometry. The PD-1 molecules on the surface of Lewis lung cancer cell line, C57BL/6 mouse spleen T lymphocytes and peripheral blood T lymphocytes were positively expressed. Compared with the control group, the volume of the transplanted tumor of Lewis lung cancer in C57BL/6 mice was larger with 10 μg sPD-L1 I g injection (P less than 0.05), and no significant difference was observed in tumor volume with 2.5 μg and 5 μg injection (P > 0.05). A certain level of soluble PD-L1 (10 μg/ mouse) could promote the growth of transplanted tumors of Lewis lung cancer in C57BL/6 mice.