Expression of programmed cell death 1 on neuroblastoma cells in TH-MYCN transgenic mice

Background: Immunotherapy may improve the poor prognosis of high-risk neuroblastoma. Programmed cell death 1 (PD-1) is expressed in several cancers. The tyrosine hydroxylase MYCN (TH-MYCN) transgenic mouse model is widely used in neuroblastoma research, but detailed information on its immunological background is lacking. Therefore, we studied the immunological tumor microenvironment and tumor cell surface antigen expression in homozygote and hemizygote mice and effects of antibody therapy against PD-1. Methods CD4, CD8, CD11b, and CD11c expression in immune cells from retroperitoneal lymph nodes and spleen was analyzed by flowcytometry. Tumor cell surface antigen expression was confirmed, and data from homozygote and hemizygote mice were compared. Effects of anti-PD-1 antibody were evaluated. Results CD4-, CD8-, CD11b-, and CD11c-positive cells were not significantly different in homozygote and hemizygote mice, and CD11b- and CD11c-positive cells were identified in the tumor microenvironment in both. Tumor cells expressed PD-1, and anti-PD-1 antibody had anti-tumor effects and significantly reduced the percentage of living tumor cells in cultures after 2 hours. Conclusion The immunological background is similar in homozygote and hemizygote TH-MYCN transgenic mice, and both have PD-1–positive tumor cells. Anti-PD-1 antibody suppresses tumor growth. This mouse model may be a useful for studying immunotherapy of neuroblastoma.