High expression of CD28 enhanced the anti-cancer effect of siRNA-PD-1 through prompting the immune response of melanoma-bearing mice

Immune checkpoint blockade is considered to be an effective method of tumor immunotherapy. As one of the main immune checkpoints, blocking PD-1/PD-L1 pathway has been proved to be effective in the treatment of many cancers via activating T cells; however, many patients still do not respond to the blocking PD-1/PD-L1 treatment with satisfying results. Related research demonstrated that the activation of T cells required a co stimulatory signal generated by the interaction between CD28 and CD80/CD86, whereas in many patients, CD28 on the T cell surface was lost. Thus, in this study, we constructed the co-expression plasmid of CD28-siRNAPD-1 and explored the anti-tumor mechanism of the co-expression plasmid on mouse model. The results showed that the expression of PD-1 was inhibited and the expression of CD28 was increased significantly in tumor tissues after the mice were treated with the co-expression plasmid. The survival rate of the tumor-bearing mice was recorded every day. PD-1 expression and tumor-infiltrating lymphocytes in cancer tissues were detected by immunofluorescence staining and the ratios of different immune cells in spleens were detected by flow cytometry. We found that treatment with the co-expression plasmid significantly prolonged the survival of melanoma bearing mice, induced the cell apoptosis, increased the infiltration of T cells in tumor tissues, and altered the ratios of different immune cells in the spleens. These results also laid the foundation for reducing the resistance of PD-1 blockade in the clinic.

Automated summary

The study demonstrated that co-expression of CD28-siRNAPD-1 plasmid significantly increased T cell infiltration, induced tumor cell apoptosis, prolonged the survival of melanoma patients, and altered the ratios of different immune cells in the spleens. These results provide a foundation for reducing the resistance of PD-1 blockade in clinical settings.