Upregulation of CD3 zeta and L-selectin in antigen-specific cytotoxic T lymphocytes by eliminating myeloid-derived suppressor cells with doxorubicin to improve killing efficacy of neuroblastoma cells in vitro

Background Agglomeration of myeloid-derived suppressor cells (MDSCs) in tumors impedes immunotherapeutic effects. Doxorubicin (DOX) is currently the most specific drug used for the selective removal of MDSCs. Here, we study the feasibility and mechanism of eliminating MDSCs by DOX to improve antigen-specific cytotoxic T lymphocyte (CTL)-killing neuroblastoma (NB) cells in vitro. Methods CTL and MDSC were prepared; then, CTLs, NB cells, MDSCs, and DOX were mixed and cultivated in different collocation patterns and divided into different groups. The levels of cluster of differentiation 3 zeta chain (CD3 zeta) and L-selectin in CTL in different groups were detected. Thereafter, the killing rate of NB cells and secretion of interleukin-2 and interferon-gamma were measured and compared. Results By real-time polymerase chain reaction (PCR) and Western blot test respectively, the proliferation and killing effect of CTLs on NB cells were all inhibited by MDSC through downregulating CD3 zeta (p = 0.002; p = 0.001) and L-selectin (p = 0.006; p < 0.001). However, this inhibitory effect was reversed by DOX. Significant differences were observed in the levels of interleukin-2 (p < 0.001), interferon-gamma (p < 0.001), and the killing rate (p < 0.001) among the groups, except between the CTL +SK-N-SH and CTL +SK-N-SH +DOX groups (p > 0.05). Conclusions Targeted elimination of MDSCs by DOX can improve Ag-specific CTL killing of NB cells in vitro by upregulating CD3 zeta and L-selectin. This study provides a novel method to enhance the immunotherapeutic effects of NB.