Immune checkpoint inhibitors such as anti-PD-1 antibody and anti-CTLA-4 antibody have recently been approved for the treatment of melanoma or non-small cell lung cancer. In this study, we examined an evaluation method for tumor infiltrating lymphocytes (TILs), which is one of the evaluation items of immune checkpoint inhibitors.
BALB/c mice were subcutaneously inoculated with CT26WT(mouse colorectal cancer cell line). They were allocated into anti-PD-1, anti-CTLA-4, or their combination treatment and the control groups. The drugs were administered intraperitoneally twice a week for two weeks. The tumor diameters were measured and tumor volumes were calculated. Observation and measurement were performed up to 14 days after the initiation of administration. Then, the tumor was excised and dispersed. TILs were isolated using CD45 microbeads, stained by fluorescently-conjugated antibodies and analyzed using flow cytometer.
As a result, the drugs changed the proportion of TILs subsets including regulatory T cells (Treg), CD8+ T cells, dendritic cells (DC) and myeloid-derived suppressor cells (MDSC). It is suggested that the evaluation system described above is useful for identification of TILs subsets in the CT26WT-bearing mouse model.